This study investigates the synergistic effects of combining fly ash and silica fume to produce high-strength self-compacting cementitious composites. Seven mixtures were prepared with varying amounts of fly ash (17.5-25%) and silica fume (1.25-7.5%) as a replacement for ordinary portland cement. The mixtures were tested for rheological properties in the fresh state and mechanical properties like compressive strength and ultrasonic pulse velocity in the hardened state. The results showed that a combination of 80% fly ash and 20% silica fume produced the highest flowability. For superior mechanical properties, the optimum mixture contained 80% cement, 17.5% fly ash and 2
This document summarizes a research study on the effect of using electrically precipitated fly ash (EPFA) as a partial replacement for cement in self-compacting concrete (SCC). The study tested SCC mixes with 0-30% EPFA replacement at 5% intervals. Tests were conducted on fresh properties, mechanical properties like compressive strength, and durability properties like rapid chloride permeability and water sorptivity. Results showed that 20% EPFA replacement provided better results than the control SCC mix, improving properties while also providing economic and environmental benefits through reduced cement usage.
This document discusses a study on the effect of using Sudanese aggregates and supplementary cementitious materials like silica fume and fly ash to produce high strength concrete. Hundreds of concrete specimens with different mixtures of local materials, silica fume, fly ash, and water-cement ratios were tested to determine compressive strength and workability. The results showed that local Sudanese materials can be used to successfully produce concrete with a compressive strength of 80 MPa when combined with supplementary cementitious materials. Water-cement ratio had an inverse relationship with compressive strength. Silica fume improved short and long-term concrete properties while fly ash inversely affected 28-day strength. The study aims to provide insights for producing
Iaetsd experimental study on properties of ternary blended fibreIaetsd Iaetsd
This document summarizes an experimental study on the properties of self-compacting concrete (SCC) blended with ternary fibers including fly ash, rice husk ash, and steel fibers. The study found that replacing some of the cement content in SCC with these mineral admixtures and fibers can improve the strength and durability of SCC while making it more cost effective. Specifically, the study observed overall improvements in the compressive strength, split tensile strength, and flexural strength of SCC mixtures with varying blends of fly ash, rice husk ash, and steel fibers.
Critical review on Mix Proportioning stipulations for High Volume Fly ash con...IRJET Journal
This document provides a critical review of mix proportioning specifications for High Volume Fly Ash Concrete (HVFAC). It discusses how HVFAC can be more eco-friendly and cost-efficient than traditional Portland cement concrete. Less water-to-binder ratio, finer fly ash particles, and increased curing time all contribute to higher compressive strength in HVFAC. The document reviews previous research on mix proportioning of HVFAC and the effects of variables like water-to-binder ratio, fly ash content, and curing age. It also summarizes typical mix designs used in previous studies involving 50-65% fly ash replacement of cement by mass.
The document presents the results of an experimental study investigating the use of silica fume as a partial replacement for cement in high performance concrete. Various mix proportions were tested with silica fume replacement levels ranging from 0% to 12.5%. Specimens including cubes, beams, and cylinders were cast and tested at 7, 14, and 28 days to evaluate the compressive strength, flexural strength, and split tensile strength of the concrete mixtures. The study found that replacing 7.5% of the cement with silica fume produced concrete with sufficient strength for construction purposes while also reducing the amount of cement used, providing economic and sustainability benefits.
The document discusses the mechanical properties of cement mortar containing lime and rice husk ash. Three types of mortar mixtures were tested: 1) cement-rice husk ash mortar, 2) cement-rice husk ash-lime mortar, and 3) rice husk ash-lime mortar. Testing showed that the cement-rice husk ash mortar achieved the highest compressive and flexural strengths over time due to cement hydration and pozzolanic reactions. The cement-rice husk ash-lime mortar had lower strengths, especially at early ages, because of the lower cement content. The rice husk ash-lime mortar gained strength through the combined pozzolanic reaction and carbon
Effects of Silica Fume and Fly Ash as Partial Replacement of Cement on Water ...idescitation
This document summarizes a study that investigated the effects of silica fume and fly ash as partial replacements for cement on the water permeability and strength of high performance concrete. Seven mix designs were tested for each material, with silica fume replacing 0-20% of cement and fly ash replacing 0-30%. Test results found that mixes with 10% silica fume and 20% fly ash exhibited the lowest water penetration depths at 11mm and 15mm, respectively. Mixes with 7.5% silica fume and 10% fly ash achieved the highest compressive, split tensile, and flexural strengths. The results indicate that partial replacement of cement with these industrial byproducts can improve the strength and water permeability
Characteristics of High-Strength Concrete Incorporating Marble Waste as a Par...IRJET Journal
The document discusses using marble waste as a partial replacement for cementitious materials in high-strength concrete. Various concrete mixtures were produced by replacing cement, silica fume, and fly ash with 5-20% marble waste. The mixtures were tested to evaluate the effect on workability, compressive strength, flexural strength, splitting tensile strength, water absorption, and unit weight at curing periods of 7, 28, and 56 days. Test results found that replacing 10% of the cementitious materials with marble waste, 10% with silica fume, and 5% with fly ash improved the mechanical properties and durability of the concrete while reducing costs.
This document summarizes a research study on the effect of using electrically precipitated fly ash (EPFA) as a partial replacement for cement in self-compacting concrete (SCC). The study tested SCC mixes with 0-30% EPFA replacement at 5% intervals. Tests were conducted on fresh properties, mechanical properties like compressive strength, and durability properties like rapid chloride permeability and water sorptivity. Results showed that 20% EPFA replacement provided better results than the control SCC mix, improving properties while also providing economic and environmental benefits through reduced cement usage.
This document discusses a study on the effect of using Sudanese aggregates and supplementary cementitious materials like silica fume and fly ash to produce high strength concrete. Hundreds of concrete specimens with different mixtures of local materials, silica fume, fly ash, and water-cement ratios were tested to determine compressive strength and workability. The results showed that local Sudanese materials can be used to successfully produce concrete with a compressive strength of 80 MPa when combined with supplementary cementitious materials. Water-cement ratio had an inverse relationship with compressive strength. Silica fume improved short and long-term concrete properties while fly ash inversely affected 28-day strength. The study aims to provide insights for producing
Iaetsd experimental study on properties of ternary blended fibreIaetsd Iaetsd
This document summarizes an experimental study on the properties of self-compacting concrete (SCC) blended with ternary fibers including fly ash, rice husk ash, and steel fibers. The study found that replacing some of the cement content in SCC with these mineral admixtures and fibers can improve the strength and durability of SCC while making it more cost effective. Specifically, the study observed overall improvements in the compressive strength, split tensile strength, and flexural strength of SCC mixtures with varying blends of fly ash, rice husk ash, and steel fibers.
Critical review on Mix Proportioning stipulations for High Volume Fly ash con...IRJET Journal
This document provides a critical review of mix proportioning specifications for High Volume Fly Ash Concrete (HVFAC). It discusses how HVFAC can be more eco-friendly and cost-efficient than traditional Portland cement concrete. Less water-to-binder ratio, finer fly ash particles, and increased curing time all contribute to higher compressive strength in HVFAC. The document reviews previous research on mix proportioning of HVFAC and the effects of variables like water-to-binder ratio, fly ash content, and curing age. It also summarizes typical mix designs used in previous studies involving 50-65% fly ash replacement of cement by mass.
The document presents the results of an experimental study investigating the use of silica fume as a partial replacement for cement in high performance concrete. Various mix proportions were tested with silica fume replacement levels ranging from 0% to 12.5%. Specimens including cubes, beams, and cylinders were cast and tested at 7, 14, and 28 days to evaluate the compressive strength, flexural strength, and split tensile strength of the concrete mixtures. The study found that replacing 7.5% of the cement with silica fume produced concrete with sufficient strength for construction purposes while also reducing the amount of cement used, providing economic and sustainability benefits.
The document discusses the mechanical properties of cement mortar containing lime and rice husk ash. Three types of mortar mixtures were tested: 1) cement-rice husk ash mortar, 2) cement-rice husk ash-lime mortar, and 3) rice husk ash-lime mortar. Testing showed that the cement-rice husk ash mortar achieved the highest compressive and flexural strengths over time due to cement hydration and pozzolanic reactions. The cement-rice husk ash-lime mortar had lower strengths, especially at early ages, because of the lower cement content. The rice husk ash-lime mortar gained strength through the combined pozzolanic reaction and carbon
Effects of Silica Fume and Fly Ash as Partial Replacement of Cement on Water ...idescitation
This document summarizes a study that investigated the effects of silica fume and fly ash as partial replacements for cement on the water permeability and strength of high performance concrete. Seven mix designs were tested for each material, with silica fume replacing 0-20% of cement and fly ash replacing 0-30%. Test results found that mixes with 10% silica fume and 20% fly ash exhibited the lowest water penetration depths at 11mm and 15mm, respectively. Mixes with 7.5% silica fume and 10% fly ash achieved the highest compressive, split tensile, and flexural strengths. The results indicate that partial replacement of cement with these industrial byproducts can improve the strength and water permeability
Characteristics of High-Strength Concrete Incorporating Marble Waste as a Par...IRJET Journal
The document discusses using marble waste as a partial replacement for cementitious materials in high-strength concrete. Various concrete mixtures were produced by replacing cement, silica fume, and fly ash with 5-20% marble waste. The mixtures were tested to evaluate the effect on workability, compressive strength, flexural strength, splitting tensile strength, water absorption, and unit weight at curing periods of 7, 28, and 56 days. Test results found that replacing 10% of the cementitious materials with marble waste, 10% with silica fume, and 5% with fly ash improved the mechanical properties and durability of the concrete while reducing costs.
1) The document presents a study on the mix design parameters of high strength concrete using iso-strength lines.
2) Sixteen concrete mixes were designed with water-binder ratios ranging from 0.30 to 0.42 and silica fume replacements ranging from 0 to 15%.
3) Regression analysis was used to develop relationships between slump, water content, and compressive strength at various ages for the different mixes. Iso-strength lines were plotted to predict strength based on water-binder ratio and silica fume content.
Experimental evaluation of the durability properties of high performanceIAEME Publication
The document discusses the use of admixtures to improve the durability properties of high performance concrete (HPC). It describes how supplementary cementing materials (SCMs) like fly ash, silica fume, and metakaoline can improve the strength and durability of HPC when used to partially replace cement. The document also examines the acid resistance and sulfate resistance of HPC specimens containing these admixtures through immersion testing in acid and sulfate solutions. Test results showed that HPC with SCMs exhibited greater resistance to chemical attacks compared to plain cement concrete.
Experimental evaluation of the durability properties of high performanceIAEME Publication
The document discusses the use of admixtures to improve the durability properties of high performance concrete (HPC). It describes how supplementary cementing materials (SCMs) like fly ash, silica fume, and metakaoline can improve the strength and durability of HPC when used to partially replace cement. The document also examines the acid resistance and sulfate resistance of HPC mixtures containing various SCMs through experimental testing of specimens exposed to acids and sulfate solutions.
An Experimental Investigation on Strength Characteristics of Concrete with Pa...ijsrd.com
One of the approaches in improving the durability of concrete is to use blended cement materials such as fly ash, silica fume, slag and more recently, metakaolin. By changing the chemistry and microstructure of concrete, pozzolans reduce the capillary porosity of the cementitious system and make them less permeable to exterior chemical sources as well as reducing the internal chemical incompatilities such as alkali-silica reaction. The concrete industry is known to leave an enormous environmental footprint on Planet Earth. First, there are the sheer volumes of material needed to produce the billions of tons of concrete worldwide each year. Then there are the CO2 emissions caused during the production of Portland cement. Together with the energy requirements, water consumption and generation of construction and demolition waste, these factors contribute to the general appearance that concrete is not particularly environmentally friendly or compatible with the demands of sustainable development. Thus, use of these supplementary cementitious materials can reduce the effects of cement causing severe environmental impact. This study presents the results of different mechanical properties of concrete such as compressive strength, split tensile strength and flexural concrete by partially replacing cement with metakaolin and silica fume. The replacement of metakaolin is varied from 10%, 15%, 20% and 25% and silica fume from 6%, 8% and 10%. The property of concrete in fresh state that is the workability is also studied during the present investigation. The optimum doses of silica fume and metakaolin in combination were found to be 6% and 15% (by weight) respectively, when used as part replacement of ordinary Portland cement.
This document summarizes an experimental investigation on the effect of industrial byproducts on the strength properties of high performance concrete. Specifically, it examines partially replacing cement, fine aggregate, and coarse aggregate with silica fume, bottom ash, and steel slag aggregate. There were a total of 15 mixes created with different material contents, including one conventional concrete mix. Testing found that replacing cement with 5% silica fume and replacing fine and coarse aggregate with 10% bottom ash and steel slag achieved higher strengths compared to other mixes. The mixes were classified as binary combinations of two materials or ternary combinations of all three materials.
IRJET - Effect of Partial Replacement of Portland Cement with Fly Ash, Rice H...IRJET Journal
This document summarizes research on partially replacing Portland cement with fly ash, rice husk ash, and bagasse ash in concrete. Studies have found improvements in the mechanical and chemical properties of concrete when cement is replaced with these materials at optimal levels, up to 30% replacement. The replacement materials act as pozzolans, reacting with calcium hydroxide produced during cement hydration to form additional calcium-silicate-hydrate, improving strength and durability. Research has shown increases in compressive, tensile, and flexural strength as well as reductions in permeability. Combinations of fly ash, rice husk ash, and bagasse ash have been found to be more effective than individual replacements.
Effects of Superplasticizers on Fresh and Hardened Portland Cement Concrete C...Fady M. A Hassouna
This document studied the effects of different dosages of superplasticizer on the properties of fresh and hardened concrete. Slump tests found that workability increased with higher dosages up to a point, beyond which it became undesirable. Compressive strength generally increased up to an optimum dosage of 1% for early strength and 3% for ultimate strength, beyond which strength decreased. The optimum dosages provided a good balance of workability and strength. The study concluded that superplasticizers can effectively increase strength and workability, but only up to a certain dosage, beyond which negative effects occur.
IRJET- Behaviour of Mineral Admixture on Strength and Durability of ConcreteIRJET Journal
This document discusses the effects of mineral admixtures on the strength and durability of high performance concrete (HPC). Two HPC mixes were designed - a control mix without admixtures and a mix replacing 15% cement with fly ash and 10% with silica fume. Testing found the admixture mix achieved higher 7-day and 28-day compressive strengths than the control. Durability testing also indicated the admixture mix had better resistance to chloride and sulfate attack over 180 days. The improved performance is attributed to the pozzolanic reactions of fly ash and silica fume creating a denser microstructure in the concrete.
UTILIZATION OF RICE HUSK ASH AS A POZZOLAN IN SELF COMPACTING CONCRETE IAEME Publication
The utilization of industrial and agricultural waste can be used as a pozzolanic material in Self-consolidating concrete, as the name a concrete that completely fills the formwork under its own weight without using compaction vibrator by maintaining the homogeneity of concrete. Self-compacting concrete is to resist deformability and segregation in concrete. Deformability known as flow ability is the ability of self-compacting concrete to deform under its own weight without any obstructions. On the other hand segregation resistance is the ability to maintain the homogeneous matrix in between concrete while casting concrete.
The study explores the use of Rice Husk Ash (RHA) to increase the amount of fines and hence achieve self-compact ability in an economical way. The pozzolan used in this research was rice husk under the ASTM standard C618 (Class N). The study focuses on comparison of fresh and hardened properties of self-compacting concrete containing varying amount of 0%, 5% and 10% RHA with dosage of viscosity modifying agent of 2% to 4.5% as an admixture. The comparison is done at different dosages of super-plasticizer keeping cement, water, coarse aggregate, and fine aggregate contents constant.
The fresh properties of SCC for flow spread shows that by increasing the amount of RHA the spread decreases. The V-funnel at T=5 min showed that increase in RHA and decrease in super plasticizer high, segregation is resisted at higher content of RHA. Beside this the 10% rice husk ash at 4% super plasticizer proved the higher compressive strength as compared to other mixes. The study concluded that the SCC produced utilizing RHA is more durable than the similar concrete utilizing commercially available admixture.
Characteristics of Ultra-High-Performance Fiber-Reinforced Concrete with admi...IRJET Journal
This document reviews the characteristics of ultra-high-performance fiber reinforced concrete (UHPFRC) with admixtures. It investigates the historical background and workability effects of steel fibers in plain and UHPFRC. The addition of mineral admixtures like nano-silica and steel fibers at 1-3% by volume is found to improve the strength and workability of UHPFRC. However, the workability is reduced by the finer particle sizes of mineral admixtures and increased viscosity from steel fibers. Optimal dosages of fibers and admixtures are needed to ensure uniform fiber distribution and adequate workability for practical applications of UHPFRC.
Strength Studies on Metakaolin Modified Cement Mortar with Quarry Dust as Fin...IDES Editor
Scarcity of river sand is one of the major problems
in the construction industry. Studies were conducted to find
out the feasibility of using quarry dust to partially replace
sand in concrete. . These studies revealed that, due to increased
fineness, the combination require an increased water cement
ratio which results in strength reduction or the use of a water
reducing admixture. Use of super pozzolanic supplementary
cementing materials such as silica fume, rice husk ash,
metakaolin etc in concrete and mortar improves the strength
even at a higher water binder ratio. Metakaolin, a
manufactured material, calcined kaolinite is available at
moderate cost. This paper presents the results of a study to
use metakaolin in cement mortar as a partial replacement of
cement where quarry dust was used as the fine aggregate.
The effect of water binder ratio and metakaolin replacement
level on the compressive strength of cement quarry dust mortar
was investigated.
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
RECENT INNOVATIONS IN HIGH VOLUME FLY ASH CONCRETE: A REVIEWIRJET Journal
This document provides a literature review of recent innovations in high volume fly ash concrete. It discusses how high volume fly ash concrete can provide improved mechanical and durability properties compared to conventional concrete when using mineral admixtures like fly ash, GGBS, silica fume, and limestone powder. The literature review revealed that curing time, fly ash content, choice and content of mineral admixtures are the main factors controlling properties. While research has shown benefits of high volume fly ash concrete, challenges remain regarding optimal mineral admixture selection and content.
IRJET- Experimental Investigation for Strength of Concrete by using Fly AshIRJET Journal
This document summarizes an experimental investigation into the strength of concrete when using fly ash. Fly ash from various sources was used to replace 25% of cement by weight or volume in mortar mixes. The mixes were tested at various water-to-binder ratios and cured for up to 90 days. Testing showed that early strength was lower with fly ash but most mixes recovered strength by 28 days. Finer fly ashes performed equal to or better than ordinary Portland cement after 28 days. The results indicate that fly ash can provide strength improvements to concrete while providing economic and environmental benefits over pure cement.
This document summarizes a study on the properties of self-compacting concrete (SCC) made with different percentages of fly ash replacement. The key points are:
1) SCC mixes were made with 0%, 10%, 20%, 30%, 40%, and 50% cement replacement by fly ash. Fresh properties like slump flow and passing ability generally increased with higher fly ash content.
2) Hardened properties like compressive, split tensile, and flexural strength generally decreased with higher fly ash content compared to the control mix, though the 30% replacement mix performed best.
3) Durability properties like acid resistance and saturated water absorption improved with increasing fly ash content, indicating fly ash increases concrete imper
Self Compacting Concrete And Its PropertiesIJERA Editor
Self-compacting concrete (SCC), which flows under its own weight and doesn’t require any external vibration for compaction, has revolutionized concrete placement. Such concrete should have relatively low yield value to ensure high flow ability, a moderate viscosity to resists segregation and bleeding and must maintain its homogeneity during transportation, placing and curing to ensure adequate structural performance and long term durability. Self-compacting concrete (SCC) can be defined as a fresh concrete which possesses superior flow ability under maintained stability (i.e. no segregation) thus allowing self-compaction that is, material consolidation without addition of energy. Self-compacting concrete is a fluid mixture suitable for placing in structures with Congested reinforcement without vibration and it helps in achieving higher quality of surface finishes. However utilization of high reactive Metakaolin and Flyash asan admixtures as an effective pozzolan which causes great improvement in the porestructure. The relative proportions of key components are considered by volumerather than by mass.
Impact and Performance of Linen Fiber Reinforced Concrete in Slender ColumnsAJSERJournal
This study was consisted of two phases, revealed the behavior of Self-Compacting Concrete (SCC)
specimens of small-diameter slender column to achieve high quality concrete properties without using concrete
vibrator. The first phase investigated the effect of linen fiber on the rheological properties of SCC using two mixes types:
type I mix: without lime powder, and type II mix: with 20% lime as a replacement of cement content. The linen fiber was
contented of 0, 2, and 4 Kg/m³. In the second phase, the type II mix was used to cast three columns; one with plain SCC
and the other two with 2 and 4 Kg/m³ fiber contents. These columns were cured and cut in a certain manner to obtain 7
cylinders 150 × 300 mm and 8 slices 20 mm thickness. The cylinders were used to measure the distribution of unit
weight, compressive strength, and ultrasonic pulse velocity (UPV) along the column height. The rheological properties
of SCC were reduced with the additives of fibers to the mix constituents, but the properties of Fiber reinforced SelfCompacted Concrete (FSCC) were tested at 4 Kg/m³ fiber content. The distribution of unit weight, compressive strength,
and UPV provided good compaction of concrete. Also, the distribution of coarse aggregate at bottom, middle and top
sections of columns were uniformly distributed.
Analysis of Microstructural Behaviour of Rice Husk Ash Blended Cement MortarIRJET Journal
1) The document analyzes the microstructural properties of rice husk ash (RHA) and the effects of replacing cement with RHA at levels from 0-25% in cement mortar.
2) Testing showed compressive strength initially increased with RHA up to 15% but declined above that, while consistency continuously increased with RHA.
3) Analysis using XRD, TGA and DSC showed RHA contains quartzite, coesite and amorphous silica which impacts properties. SEM and EDS examination showed phase changes in calcium silicate hydrate with curing.
4) Partial cement replacement by RHA could reduce environmental impacts from cement production while maintaining or improving mechanical
Study of Macro level Properties of SCC using GGBS and Lime stone powderIJERD Editor
The document summarizes a study on the use of ground granulated blast furnace slag (GGBS) and limestone powder to replace cement in self-compacting concrete (SCC). Tests were conducted on SCC mixes with 0-50% replacement of cement with GGBS and 0-20% replacement with limestone powder. The results showed that replacing 30% of cement with GGBS and 15% with limestone powder produced SCC with the highest compressive strength of 46MPa, meeting fresh property requirements. The study concluded that this ternary blend of cement, GGBS and limestone powder can improve SCC properties while reducing costs.
Analysis of Admixtures and Their Effects of Silica Fumes, Metakaolin and PFA...IJMER
This paper presents a review of the properties of fresh concrete including workability, heat
of hydration, setting time, bleeding, and reactivity by using mineral admixtures fly ash (FA), silica
fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK), and rice husk ash (RHA).
Comparison of normal and high strength concrete in which cement has been partially supplemented
by mineral admixture has been considered. It has been concluded that mineral admixtures may be
categorized into two groups: chemically active mineral admixtures and microfiller mineral
admixtures. Chemically active mineral admixtures decrease workability and setting time of concrete
but increase the heat of hydration and reactivity. On the other hand, micro filler mineral admixtures
increase workability and setting time of concrete but decrease the heat of hydration and reactivity. In
general, small particle size and higher specific surface area of mineral admixture are favourable to
produce highly dense and impermeable concrete; however, they cause low workability and demand
more water which may be offset by adding effective super plasticizer.
This document summarizes a study that assessed the fresh and hardened properties of self-consolidating concrete (SCC) containing steel, polypropylene, and hybrid fibers at various high temperatures. Four SCC mixtures were tested: a control without fibers, one with 1% polypropylene fibers, one with 1% steel fibers, and one with 0.5% of each steel and polypropylene fibers. All mixtures met standards for workability and passing ability. The inclusion of fibers slightly reduced workability. Mechanical properties generally increased with temperature up to 200°C then decreased at higher temperatures. Fiber-reinforced SCC exhibited improved spalling resistance compared to plain SCC.
This document reviews the development and use of supplementary cementitious materials (SCMs) in self-compacting concrete (SCC). It summarizes past literature on how various calcium-rich and silica-rich SCMs have been used to improve the properties of SCC. The review focuses on the effects of ultra-fine fly ash (UFFA) on the plastic and hardened properties of SCC. It notes that prior studies have examined the use of SCMs like fly ash, slag, and silica fume to enhance workability and strength but that no comprehensive study has looked at the impact of UFFA specifically. The review proposes that future work should examine how UFFA influences SCC properties using an artificial
1) The document presents a study on the mix design parameters of high strength concrete using iso-strength lines.
2) Sixteen concrete mixes were designed with water-binder ratios ranging from 0.30 to 0.42 and silica fume replacements ranging from 0 to 15%.
3) Regression analysis was used to develop relationships between slump, water content, and compressive strength at various ages for the different mixes. Iso-strength lines were plotted to predict strength based on water-binder ratio and silica fume content.
Experimental evaluation of the durability properties of high performanceIAEME Publication
The document discusses the use of admixtures to improve the durability properties of high performance concrete (HPC). It describes how supplementary cementing materials (SCMs) like fly ash, silica fume, and metakaoline can improve the strength and durability of HPC when used to partially replace cement. The document also examines the acid resistance and sulfate resistance of HPC specimens containing these admixtures through immersion testing in acid and sulfate solutions. Test results showed that HPC with SCMs exhibited greater resistance to chemical attacks compared to plain cement concrete.
Experimental evaluation of the durability properties of high performanceIAEME Publication
The document discusses the use of admixtures to improve the durability properties of high performance concrete (HPC). It describes how supplementary cementing materials (SCMs) like fly ash, silica fume, and metakaoline can improve the strength and durability of HPC when used to partially replace cement. The document also examines the acid resistance and sulfate resistance of HPC mixtures containing various SCMs through experimental testing of specimens exposed to acids and sulfate solutions.
An Experimental Investigation on Strength Characteristics of Concrete with Pa...ijsrd.com
One of the approaches in improving the durability of concrete is to use blended cement materials such as fly ash, silica fume, slag and more recently, metakaolin. By changing the chemistry and microstructure of concrete, pozzolans reduce the capillary porosity of the cementitious system and make them less permeable to exterior chemical sources as well as reducing the internal chemical incompatilities such as alkali-silica reaction. The concrete industry is known to leave an enormous environmental footprint on Planet Earth. First, there are the sheer volumes of material needed to produce the billions of tons of concrete worldwide each year. Then there are the CO2 emissions caused during the production of Portland cement. Together with the energy requirements, water consumption and generation of construction and demolition waste, these factors contribute to the general appearance that concrete is not particularly environmentally friendly or compatible with the demands of sustainable development. Thus, use of these supplementary cementitious materials can reduce the effects of cement causing severe environmental impact. This study presents the results of different mechanical properties of concrete such as compressive strength, split tensile strength and flexural concrete by partially replacing cement with metakaolin and silica fume. The replacement of metakaolin is varied from 10%, 15%, 20% and 25% and silica fume from 6%, 8% and 10%. The property of concrete in fresh state that is the workability is also studied during the present investigation. The optimum doses of silica fume and metakaolin in combination were found to be 6% and 15% (by weight) respectively, when used as part replacement of ordinary Portland cement.
This document summarizes an experimental investigation on the effect of industrial byproducts on the strength properties of high performance concrete. Specifically, it examines partially replacing cement, fine aggregate, and coarse aggregate with silica fume, bottom ash, and steel slag aggregate. There were a total of 15 mixes created with different material contents, including one conventional concrete mix. Testing found that replacing cement with 5% silica fume and replacing fine and coarse aggregate with 10% bottom ash and steel slag achieved higher strengths compared to other mixes. The mixes were classified as binary combinations of two materials or ternary combinations of all three materials.
IRJET - Effect of Partial Replacement of Portland Cement with Fly Ash, Rice H...IRJET Journal
This document summarizes research on partially replacing Portland cement with fly ash, rice husk ash, and bagasse ash in concrete. Studies have found improvements in the mechanical and chemical properties of concrete when cement is replaced with these materials at optimal levels, up to 30% replacement. The replacement materials act as pozzolans, reacting with calcium hydroxide produced during cement hydration to form additional calcium-silicate-hydrate, improving strength and durability. Research has shown increases in compressive, tensile, and flexural strength as well as reductions in permeability. Combinations of fly ash, rice husk ash, and bagasse ash have been found to be more effective than individual replacements.
Effects of Superplasticizers on Fresh and Hardened Portland Cement Concrete C...Fady M. A Hassouna
This document studied the effects of different dosages of superplasticizer on the properties of fresh and hardened concrete. Slump tests found that workability increased with higher dosages up to a point, beyond which it became undesirable. Compressive strength generally increased up to an optimum dosage of 1% for early strength and 3% for ultimate strength, beyond which strength decreased. The optimum dosages provided a good balance of workability and strength. The study concluded that superplasticizers can effectively increase strength and workability, but only up to a certain dosage, beyond which negative effects occur.
IRJET- Behaviour of Mineral Admixture on Strength and Durability of ConcreteIRJET Journal
This document discusses the effects of mineral admixtures on the strength and durability of high performance concrete (HPC). Two HPC mixes were designed - a control mix without admixtures and a mix replacing 15% cement with fly ash and 10% with silica fume. Testing found the admixture mix achieved higher 7-day and 28-day compressive strengths than the control. Durability testing also indicated the admixture mix had better resistance to chloride and sulfate attack over 180 days. The improved performance is attributed to the pozzolanic reactions of fly ash and silica fume creating a denser microstructure in the concrete.
UTILIZATION OF RICE HUSK ASH AS A POZZOLAN IN SELF COMPACTING CONCRETE IAEME Publication
The utilization of industrial and agricultural waste can be used as a pozzolanic material in Self-consolidating concrete, as the name a concrete that completely fills the formwork under its own weight without using compaction vibrator by maintaining the homogeneity of concrete. Self-compacting concrete is to resist deformability and segregation in concrete. Deformability known as flow ability is the ability of self-compacting concrete to deform under its own weight without any obstructions. On the other hand segregation resistance is the ability to maintain the homogeneous matrix in between concrete while casting concrete.
The study explores the use of Rice Husk Ash (RHA) to increase the amount of fines and hence achieve self-compact ability in an economical way. The pozzolan used in this research was rice husk under the ASTM standard C618 (Class N). The study focuses on comparison of fresh and hardened properties of self-compacting concrete containing varying amount of 0%, 5% and 10% RHA with dosage of viscosity modifying agent of 2% to 4.5% as an admixture. The comparison is done at different dosages of super-plasticizer keeping cement, water, coarse aggregate, and fine aggregate contents constant.
The fresh properties of SCC for flow spread shows that by increasing the amount of RHA the spread decreases. The V-funnel at T=5 min showed that increase in RHA and decrease in super plasticizer high, segregation is resisted at higher content of RHA. Beside this the 10% rice husk ash at 4% super plasticizer proved the higher compressive strength as compared to other mixes. The study concluded that the SCC produced utilizing RHA is more durable than the similar concrete utilizing commercially available admixture.
Characteristics of Ultra-High-Performance Fiber-Reinforced Concrete with admi...IRJET Journal
This document reviews the characteristics of ultra-high-performance fiber reinforced concrete (UHPFRC) with admixtures. It investigates the historical background and workability effects of steel fibers in plain and UHPFRC. The addition of mineral admixtures like nano-silica and steel fibers at 1-3% by volume is found to improve the strength and workability of UHPFRC. However, the workability is reduced by the finer particle sizes of mineral admixtures and increased viscosity from steel fibers. Optimal dosages of fibers and admixtures are needed to ensure uniform fiber distribution and adequate workability for practical applications of UHPFRC.
Strength Studies on Metakaolin Modified Cement Mortar with Quarry Dust as Fin...IDES Editor
Scarcity of river sand is one of the major problems
in the construction industry. Studies were conducted to find
out the feasibility of using quarry dust to partially replace
sand in concrete. . These studies revealed that, due to increased
fineness, the combination require an increased water cement
ratio which results in strength reduction or the use of a water
reducing admixture. Use of super pozzolanic supplementary
cementing materials such as silica fume, rice husk ash,
metakaolin etc in concrete and mortar improves the strength
even at a higher water binder ratio. Metakaolin, a
manufactured material, calcined kaolinite is available at
moderate cost. This paper presents the results of a study to
use metakaolin in cement mortar as a partial replacement of
cement where quarry dust was used as the fine aggregate.
The effect of water binder ratio and metakaolin replacement
level on the compressive strength of cement quarry dust mortar
was investigated.
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
RECENT INNOVATIONS IN HIGH VOLUME FLY ASH CONCRETE: A REVIEWIRJET Journal
This document provides a literature review of recent innovations in high volume fly ash concrete. It discusses how high volume fly ash concrete can provide improved mechanical and durability properties compared to conventional concrete when using mineral admixtures like fly ash, GGBS, silica fume, and limestone powder. The literature review revealed that curing time, fly ash content, choice and content of mineral admixtures are the main factors controlling properties. While research has shown benefits of high volume fly ash concrete, challenges remain regarding optimal mineral admixture selection and content.
IRJET- Experimental Investigation for Strength of Concrete by using Fly AshIRJET Journal
This document summarizes an experimental investigation into the strength of concrete when using fly ash. Fly ash from various sources was used to replace 25% of cement by weight or volume in mortar mixes. The mixes were tested at various water-to-binder ratios and cured for up to 90 days. Testing showed that early strength was lower with fly ash but most mixes recovered strength by 28 days. Finer fly ashes performed equal to or better than ordinary Portland cement after 28 days. The results indicate that fly ash can provide strength improvements to concrete while providing economic and environmental benefits over pure cement.
This document summarizes a study on the properties of self-compacting concrete (SCC) made with different percentages of fly ash replacement. The key points are:
1) SCC mixes were made with 0%, 10%, 20%, 30%, 40%, and 50% cement replacement by fly ash. Fresh properties like slump flow and passing ability generally increased with higher fly ash content.
2) Hardened properties like compressive, split tensile, and flexural strength generally decreased with higher fly ash content compared to the control mix, though the 30% replacement mix performed best.
3) Durability properties like acid resistance and saturated water absorption improved with increasing fly ash content, indicating fly ash increases concrete imper
Self Compacting Concrete And Its PropertiesIJERA Editor
Self-compacting concrete (SCC), which flows under its own weight and doesn’t require any external vibration for compaction, has revolutionized concrete placement. Such concrete should have relatively low yield value to ensure high flow ability, a moderate viscosity to resists segregation and bleeding and must maintain its homogeneity during transportation, placing and curing to ensure adequate structural performance and long term durability. Self-compacting concrete (SCC) can be defined as a fresh concrete which possesses superior flow ability under maintained stability (i.e. no segregation) thus allowing self-compaction that is, material consolidation without addition of energy. Self-compacting concrete is a fluid mixture suitable for placing in structures with Congested reinforcement without vibration and it helps in achieving higher quality of surface finishes. However utilization of high reactive Metakaolin and Flyash asan admixtures as an effective pozzolan which causes great improvement in the porestructure. The relative proportions of key components are considered by volumerather than by mass.
Impact and Performance of Linen Fiber Reinforced Concrete in Slender ColumnsAJSERJournal
This study was consisted of two phases, revealed the behavior of Self-Compacting Concrete (SCC)
specimens of small-diameter slender column to achieve high quality concrete properties without using concrete
vibrator. The first phase investigated the effect of linen fiber on the rheological properties of SCC using two mixes types:
type I mix: without lime powder, and type II mix: with 20% lime as a replacement of cement content. The linen fiber was
contented of 0, 2, and 4 Kg/m³. In the second phase, the type II mix was used to cast three columns; one with plain SCC
and the other two with 2 and 4 Kg/m³ fiber contents. These columns were cured and cut in a certain manner to obtain 7
cylinders 150 × 300 mm and 8 slices 20 mm thickness. The cylinders were used to measure the distribution of unit
weight, compressive strength, and ultrasonic pulse velocity (UPV) along the column height. The rheological properties
of SCC were reduced with the additives of fibers to the mix constituents, but the properties of Fiber reinforced SelfCompacted Concrete (FSCC) were tested at 4 Kg/m³ fiber content. The distribution of unit weight, compressive strength,
and UPV provided good compaction of concrete. Also, the distribution of coarse aggregate at bottom, middle and top
sections of columns were uniformly distributed.
Analysis of Microstructural Behaviour of Rice Husk Ash Blended Cement MortarIRJET Journal
1) The document analyzes the microstructural properties of rice husk ash (RHA) and the effects of replacing cement with RHA at levels from 0-25% in cement mortar.
2) Testing showed compressive strength initially increased with RHA up to 15% but declined above that, while consistency continuously increased with RHA.
3) Analysis using XRD, TGA and DSC showed RHA contains quartzite, coesite and amorphous silica which impacts properties. SEM and EDS examination showed phase changes in calcium silicate hydrate with curing.
4) Partial cement replacement by RHA could reduce environmental impacts from cement production while maintaining or improving mechanical
Study of Macro level Properties of SCC using GGBS and Lime stone powderIJERD Editor
The document summarizes a study on the use of ground granulated blast furnace slag (GGBS) and limestone powder to replace cement in self-compacting concrete (SCC). Tests were conducted on SCC mixes with 0-50% replacement of cement with GGBS and 0-20% replacement with limestone powder. The results showed that replacing 30% of cement with GGBS and 15% with limestone powder produced SCC with the highest compressive strength of 46MPa, meeting fresh property requirements. The study concluded that this ternary blend of cement, GGBS and limestone powder can improve SCC properties while reducing costs.
Analysis of Admixtures and Their Effects of Silica Fumes, Metakaolin and PFA...IJMER
This paper presents a review of the properties of fresh concrete including workability, heat
of hydration, setting time, bleeding, and reactivity by using mineral admixtures fly ash (FA), silica
fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK), and rice husk ash (RHA).
Comparison of normal and high strength concrete in which cement has been partially supplemented
by mineral admixture has been considered. It has been concluded that mineral admixtures may be
categorized into two groups: chemically active mineral admixtures and microfiller mineral
admixtures. Chemically active mineral admixtures decrease workability and setting time of concrete
but increase the heat of hydration and reactivity. On the other hand, micro filler mineral admixtures
increase workability and setting time of concrete but decrease the heat of hydration and reactivity. In
general, small particle size and higher specific surface area of mineral admixture are favourable to
produce highly dense and impermeable concrete; however, they cause low workability and demand
more water which may be offset by adding effective super plasticizer.
This document summarizes a study that assessed the fresh and hardened properties of self-consolidating concrete (SCC) containing steel, polypropylene, and hybrid fibers at various high temperatures. Four SCC mixtures were tested: a control without fibers, one with 1% polypropylene fibers, one with 1% steel fibers, and one with 0.5% of each steel and polypropylene fibers. All mixtures met standards for workability and passing ability. The inclusion of fibers slightly reduced workability. Mechanical properties generally increased with temperature up to 200°C then decreased at higher temperatures. Fiber-reinforced SCC exhibited improved spalling resistance compared to plain SCC.
This document reviews the development and use of supplementary cementitious materials (SCMs) in self-compacting concrete (SCC). It summarizes past literature on how various calcium-rich and silica-rich SCMs have been used to improve the properties of SCC. The review focuses on the effects of ultra-fine fly ash (UFFA) on the plastic and hardened properties of SCC. It notes that prior studies have examined the use of SCMs like fly ash, slag, and silica fume to enhance workability and strength but that no comprehensive study has looked at the impact of UFFA specifically. The review proposes that future work should examine how UFFA influences SCC properties using an artificial
This document evaluates the strength parameters of self-compacting concrete incorporated with carbon and glass fibres. It discusses how the concrete was made with various percentages of micro silica and fibres as a replacement for cement. The compressive, tensile, and flexural strength of the concrete mixtures were tested at 7 and 28 days. The results showed that the concrete achieved the highest strength at 0.6% addition of carbon or glass fibres, with carbon fibres performing slightly better. In conclusion, the compressive strength increased by 12% for carbon fibre and 8% for glass fibre mixtures at the 0.6% fibre level.
This document discusses the effect of rheological active additives on the properties of self-compacting concrete. Stone powders from local mountain rocks were used to increase the rheological matrix and fluidity of self-compacting concrete mixtures. Plasticizers were used to regulate the properties of cement-based mixtures. The flow rate of cement suspensions and spread of mortars and concretes were evaluated with different testing methods. Results showed that limestone powder was more effective than other stone powders at improving compressive strength when added at 40% to concrete mixtures. The optimal quantities of rheological additives and plasticizers were identified to produce high-strength self-compacting concrete.
This document is the proceedings of the 2nd International Professional Doctorate and Postgraduate Symposium held at Universiti Teknologi Malaysia on September 25, 2021. It contains abstracts from various papers presented at the symposium covering topics such as machine learning, architecture, occupational health and safety, education, supply chain management, and more. The proceedings were organized by the School of Graduate Studies and Postgraduate Student Society of Universiti Teknologi Malaysia.
View of Synergetic Effect of Met kaolin for Developing Fast Setting Early Str...Muthumari Ganesan
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
The document discusses the use of copper slag as a supplementary cementitious material in high strength self-compacting concrete. Twelve concrete mixes were prepared with 0-20% fly ash replacement of cement and 10-100% copper slag replacement of fine aggregate. The fresh and mechanical properties of the mixes were evaluated up to 180 days. The results showed that workability improved with increasing copper slag content due to its glassy texture. The 40% copper slag mix achieved the maximum compressive strength. Copper slag also reduced chloride penetration and improved concrete quality according to tests. However, sulfate immersion increased weight but reduced strength over time. Overall, the study found that copper slag can be used as a sustainable material to develop high performance self-
The document presents an experimental study that evaluated the residual compressive behavior of self-compacting concrete (SCC) mixes exposed to high temperatures up to 600°C. Ten SCC mixes were tested that varied the type and amount of mineral additives used as partial replacements for cement by weight, including metakaolin (5-15%), fly ash (20-30%), and limestone (5-15%). Testing of the mixes included compressive strength, stress-strain behavior, modulus of elasticity, and strain at peak stress at room temperature and after high temperature exposure. The results showed a significant decrease in mechanical properties for all mixes after 200°C, with the mineral additives affecting the variations in residual strength by 24%
The document summarizes research into developing sustainable high-performance self-compacting concrete using ladle slag as a cement replacement. Ladle slag, a steel industry waste material, was used to replace cement at levels of 5%, 10%, 15% and 25% in self-compacting concrete mixtures. The fresh properties, mechanical properties such as compressive and splitting tensile strength, and simple durability properties of the mixtures were evaluated based on standard tests and compared to a control mixture without ladle slag. The results generally showed improvements in properties for replacements up to 15% ladle slag compared to the control mixture. The research aims to evaluate the performance of ladle slag as a supplementary cementitious material in producing sustainable high-performance
This document discusses a research study on developing high-strength self-compacting concrete using supplementary cementitious materials. The study aims to produce self-compacting concrete with high compressive strength using silica fume and fly ash as partial replacements for cement. The laboratory tests evaluated the fresh and hardened properties of self-compacting concrete mixes with binary and ternary combinations of silica fume and fly ash at different replacement levels. The results showed that both the fresh and hardened properties depended on the use of supplementary cementitious materials. Compressive, split tensile and flexural strengths significantly increased for mixes containing supplementary cementitious materials. The optimum replacement levels for high strength self-compacting concrete were found to be 10%
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
ACEP Magazine edition 4th launched on 05.06.2024Rahul
This document provides information about the third edition of the magazine "Sthapatya" published by the Association of Civil Engineers (Practicing) Aurangabad. It includes messages from current and past presidents of ACEP, memories and photos from past ACEP events, information on life time achievement awards given by ACEP, and a technical article on concrete maintenance, repairs and strengthening. The document highlights activities of ACEP and provides a technical educational article for members.
A SYSTEMATIC RISK ASSESSMENT APPROACH FOR SECURING THE SMART IRRIGATION SYSTEMSIJNSA Journal
The smart irrigation system represents an innovative approach to optimize water usage in agricultural and landscaping practices. The integration of cutting-edge technologies, including sensors, actuators, and data analysis, empowers this system to provide accurate monitoring and control of irrigation processes by leveraging real-time environmental conditions. The main objective of a smart irrigation system is to optimize water efficiency, minimize expenses, and foster the adoption of sustainable water management methods. This paper conducts a systematic risk assessment by exploring the key components/assets and their functionalities in the smart irrigation system. The crucial role of sensors in gathering data on soil moisture, weather patterns, and plant well-being is emphasized in this system. These sensors enable intelligent decision-making in irrigation scheduling and water distribution, leading to enhanced water efficiency and sustainable water management practices. Actuators enable automated control of irrigation devices, ensuring precise and targeted water delivery to plants. Additionally, the paper addresses the potential threat and vulnerabilities associated with smart irrigation systems. It discusses limitations of the system, such as power constraints and computational capabilities, and calculates the potential security risks. The paper suggests possible risk treatment methods for effective secure system operation. In conclusion, the paper emphasizes the significant benefits of implementing smart irrigation systems, including improved water conservation, increased crop yield, and reduced environmental impact. Additionally, based on the security analysis conducted, the paper recommends the implementation of countermeasures and security approaches to address vulnerabilities and ensure the integrity and reliability of the system. By incorporating these measures, smart irrigation technology can revolutionize water management practices in agriculture, promoting sustainability, resource efficiency, and safeguarding against potential security threats.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
CHINA’S GEO-ECONOMIC OUTREACH IN CENTRAL ASIAN COUNTRIES AND FUTURE PROSPECTjpsjournal1
The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
reserves and the ancient silk trade route, along with China's diplomatic endeavours in the area, has been
referred to as the "New Great Game." This research centres on the power struggle, considering
geopolitical, geostrategic, and geoeconomic variables. Topics including trade, political hegemony, oil
politics, and conventional and nontraditional security are all explored and explained by the researcher.
Using Mackinder's Heartland, Spykman Rimland, and Hegemonic Stability theories, examines China's role
in Central Asia. This study adheres to the empirical epistemological method and has taken care of
objectivity. This study analyze primary and secondary research documents critically to elaborate role of
china’s geo economic outreach in central Asian countries and its future prospect. China is thriving in trade,
pipeline politics, and winning states, according to this study, thanks to important instruments like the
Shanghai Cooperation Organisation and the Belt and Road Economic Initiative. According to this study,
China is seeing significant success in commerce, pipeline politics, and gaining influence on other
governments. This success may be attributed to the effective utilisation of key tools such as the Shanghai
Cooperation Organisation and the Belt and Road Economic Initiative.
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
2. Crystals 2021, 11, 915 2 of 14
as already emphasized in the literature [14–16]. Different industrial by-products and ashes
from coal and agricultural wastes burning can be utilized in SCC because it requires more
powder material and superplasticizer to improve its properties [17,18]. Self-compacting
mortars (SCMs) incorporating limestone powder, fly ash, rice husk ash, and blends of
fly ash with silica fume and rice husk ash have already been studied [12,19,20]. Broadly
speaking, there is no widely accepted effect of SRMs, due to interlinked actions. Thus it is
not easy to generalize their behavior [7].
Fly ash is a residue of coal burning. It is pozzolanic, and as such, can be added to SCMs
for improving their properties. Class F fly ash is a combustion residue of bituminous coal
and has pozzolanic properties [17,21,22]. SCC systems in which ordinary Portland cement
(OPC) is replaced by fly ash reduce the high-range water-reducing admixture (HRWRA)
quantity by lowering the water demand [12,17,23]. Usually, fly ash ranging from 15% to
25% by mass of binder is used in concrete [24]. Certain SCC parameters, like viscosity, yield
stress, flow rate, and spread, can be enhanced by adding high fly ash content [25]. Water
requirement for concrete can be reduced by using ultra-fine fly ash; each 10% addition
of fly ash lowers the water demand by 3% [24,26]. If concrete is continuously cured for a
prolonged period, there will be a continuous increase in strength due to the pozzolanic
activity of fly ash [27]. Fly ash is a substitute viscosity-modifying agent in SCCs [28].
Ultra-fine particles of fly ash can enhance the viscosity and compressive strength of the
SCC systems without affecting the rheological properties [29]. The principal reaction of
fly ash with portlandite and alkali is analogous to OPC hydration, i.e., secondary C-S-H
gel formation. The microstructure of the fly ash reaction product is more gel-like and
compacted as compared with that of OPC [30]. The use of fly ash as fine aggregates in the
SCC system reduces workability, unit weight, and compressive strength drastically [31].
Silica fume is an excellent amorphous powder obtained as a by-product in electric
arc furnaces. It has a particle size ranging from 0.1 to 0.2 µm. It is reported that, annually,
approximately 900,000 metric tons of silica fume are produced [19]. Silica fume enhances
the hydration reaction rate by releasing OH- ions and alkalis [32]. Silica fume improves
the rheological, mechanical, and chemical properties by mitigating corrosion in reinforcing
steel. It is beneficial for the durability of the concrete. Using varying amounts of different
mineral additives, the durability of the cementitious composite can be improved [33,34].
It has been well-established that fly ash results used in grouts and mortar are analogous
when used in concrete [35,36]. Due to specific particle morphology and less specific gravity,
the use of fly ash mitigates bleeding, enhances flowability, and limits segregation in
SCC [37,38]. Workability properties of SCC are assessed by evaluating self-compacting
mortars and are an essential part of SCC design [39,40]. Different researchers have used
SRMs to enhance the fresh and hardened properties of the SCC system [4]. Fly ash and silica
fume blend was recommended to produce composites with ultra-high-strength and good
rheological properties [12]. However, silica fume increases the HRWRA demand to achieve
the target flow. The use of silica fume hinders the flowability of the SCC system due to its
large surface area, which requires more water for lubrication [41]. It is reported that fly ash,
when used alone in large quantities, retards the strength gain of SCC systems considerably.
In contrast, the blend of fly ash and silica fume enhances the overall response [12]. The
fresh properties of the SCC system are affected by the water-to-binder ratio and quantity
of different admixtures in many ways. Accurate proportioning of these parameters is
essential for the achievement of self-compacting properties. Zeta potential is the potential
difference between dispersed particles and the layer of liquid attached to them. Fly ash
has zeta potential −38.7 mv, while that of silica fume and OPC is −21 mv and +5.5 mv,
respectively. This difference in zeta potential is beneficial for enhancing the rheological
characteristics of SCMs [7,42].
Based on the past research, it is revealed that instead of using fly ash alone, an SRM
combination of fly ash with silica fume is beneficial to enhance the overall response of
the SCM system [12]. High-strength mortar composites containing various proportions of
silica fume and fly ash can provide a fair balance between flowability and strength [43].
3. Crystals 2021, 11, 915 3 of 14
In the current study, the effect of fly ash replacement with silica fume at different levels
is carried out. Seven mix proportions were used, replacing fly ash with silica fume in
the range of 0 to 30%, at increments of 5%. In this study, the only variable was the
replacement level of fly ash with silica fume, while all the other ingredients were kept
constant. Rheological properties like flow spread, flow time, and v-funnel time were
measured, while the hardened properties, including compressive strength and flexural
strength at 3, 7, 14, 21, 28, and 56 days were also determined. Mechanical properties are
confirmed by ultrasonic pulse velocity test. This test method is used to investigate the
quality, homogeneity, presence of voids and cracks. This technique is an assessment of
the effectiveness of the crack repairing technique. Many researchers suggested different
criteria to evaluate concrete quality [44–46]. According to a study [46], a cementitious
composite with UPV 4.5 km/s is considered excellent quality. Most of the results meet
this distinction. The microstructure was also studied by high-resolution SEM images that
validate the mechanical properties and ultrasonic pulse velocity results.
2. Materials and Methods
2.1. Materials Characterization and Mix Proportions
Seven mix proportions were prepared by using ordinary Portland cement (grade
52.5N) as binder. The initial and final setting time for cement was determined as per ASTM
C191 [47], and it conforms to ASTM C150 [48] specifications. Locally available natural sand
(Lawrancepur sand), conforming to ASTM C33 [49] with fineness modulus (FM) of 2.44
and specific gravity of 2.53, was used as fine aggregate to prepare the mortar mixes.
The grain size distribution (GSD) of the fine aggregate is presented in Figure 1. The
GSD curve shows that the sand is well-graded and possesses particles of different sizes.
Class F fly ash, conforming to ASTM C618 [50], was used. The salient characteristics and
oxide composition of fly ash and silica fume are presented in Table 1. The oxide composition
of fly ash reveals that the total composition of SiO2, Al2O3, and Fe2O3 is 88.35%, which is
far more than that required for a pozzolanic material [51]. Slightly high SO3 content was
observed, which indicates that bituminous coal with high sulfur content was burnt, which
resulted in such fly ash. The high SO3 content might lead to efflorescence in hardened
mortars and concrete. It is also observed that fly ash has a high LOI. Even though the LOI
of fly ash is slightly high, it is considered usable in this study. This allowance is provided
by ASTM C 618 [52], where it is mentioned that “use of Class F pozzolan containing up
to 12.0% loss on ignition may be approved by the user if either acceptable performance
records or laboratory test results are made available”. The high value of LOI reduces
air entrainment [51]. Air entrainment is beneficial for the flowability of self-compacting
mortar/concrete; due to high LOI, a greater superplasticizer dosage will be required to
surpass target flow spread [51].
Crystals 2021, 11, x FOR PEER REVIEW 4 of 15
Figure 1. Grain size distribution curve for fine aggregate.
The presence of amorphous silica in silica fume is primarily responsible for its reac-
tivity in alkaline cementitious systems, which leads to secondary hydrates formation and
subsequent higher matrix strength due to greater gel-space ratio [53]. The amounts of
CaO, SiO2, and Al2O3 are the most important in determining the reactivity and behavior
of the mineral admixtures in the cementitious matrix. Both early-age and long-term prop-
erties are, thus, affected.
Figure 1. Grain size distribution curve for fine aggregate.
The presence of amorphous silica in silica fume is primarily responsible for its reac-
tivity in alkaline cementitious systems, which leads to secondary hydrates formation and
4. Crystals 2021, 11, 915 4 of 14
subsequent higher matrix strength due to greater gel-space ratio [53]. The amounts of CaO,
SiO2, and Al2O3 are the most important in determining the reactivity and behavior of the
mineral admixtures in the cementitious matrix. Both early-age and long-term properties
are, thus, affected.
In the mix proportions, the cement content and total powder content were fixed to
750 kg/m3 and 940 kg/m3, respectively. A w/c of 0.3 was used for all the mixes. Lower
w/p was used to ensure resistance against segregation. Superplasticizer (BASF Master gle-
nium ACE 30), which is a polycarboxylate ether with a specific gravity of 1.06g/cc, pH of 6,
and total solid content of 30% by weight), was used for attaining suitable flowability. The
admixture was selected following ASTM C494 Type F [54] and EN 934-2 T3.1/3 [55].
Table 1. XRF of fly ash and silica fume (oxide composition expressed in %age).
Description Fly Ash Silica Fume OPC *
silicon dioxide 39.45 92.31 18.92
aluminum oxide 24.81 2.29 5.09
iron oxide 24.09 1.97 2.27
calcium oxide 4.03 1.14 63.18
sulfur oxide 5.08 0.25 3.48
minor constituents 2.54 2.04 3.84
loi 6.71 1.6 1.35
moisture 1.71 - -
% passing #325 sieve 96.5 100 95
specific gravity 2.36 2.20 3.17
* Typical values [56].
2.2. Sample Preparation
A self-compacting mortar system with a combination of 1:1.5:0.25 (cement sand Fly
ash + silica fume) by weight was prepared using a mixer of capacity 5.0 L (M/S Controls
Italy Model 65-L005) conforming to EN 196-1 standard [57]. The mixer moves in two ways;
one about its axis and the other in an oscillatory way. The mixing sequence adopted in this
study comprises the initial mixing of all the dry materials at a slow speed for 60 s. Then
70% of used water was added and further mixed for 90 s at a slow speed. The mixing was
paused for 30 s, and the mixer walls were scraped with a hard rubber scraper. Then, the
remaining 30% of used water, along with a superplasticizer, was added and mixed for 150 s
at high speed. The total mixing time was 300 s.
The detailed composition of the mortar samples is given in Table 2.
Table 2. Proportion of fly ash and silica fume *.
Mix Designation
Fly Ash Content g,
(% by Weight of Cement)
Silica Fume Content, g
(% by Weight of Cement)
T0 225.00 (25.00) 00.00 (0.00)
T1 213.75 (23.75) 11.25 (1.25)
T2 202.50 (22.50) 22.50 (2.50)
T3 191.25 (21.25) 33.75 (3.75)
T4 180.00 (20.00) 45.00 (5.00)
T5 168.75 (18.75) 56.25 (6.25)
T6 157.50 (17.5) 67.50 (7.50)
* For each mix, 900 g cement, 1350 g sand, 22.5 g superplasticizer, and 270 g water were used (for casting
03 specimens).
2.3. Methodology
The testing was carried out in three phases. Initially, the fresh mortar composites
were evaluated for their rheological characteristics. The hardened mortar composites were
tested for their mechanical properties, and in the third phase of the investigation, the
microstructural characteristics of hardened material were studied in detail.
5. Crystals 2021, 11, 915 5 of 14
2.3.1. Rheological Characterization
The deformability and segregation resistance of self-compacting cementitious systems
are assessed by slump cone spread and V-funnel time [58,59]. The superplasticizer content
was adjusted in the mortar mixes to achieve a target flow of 260 mm by Hagerman’s
mini-slump cone. The superplasticizer content was fixed as 2.50% by the weight of cement
for all mix proportions after several trials to surpass the minimum flow spread as required
by EFNARC 2002 [60].
The flow spread and V-funnel time were determined using the standard method
described in EFNARC 2002 [61]. Similar to T500, which is the time of SCC to achieve a
spread of 500 mm, some researchers [12] reported measuring the time corresponding to
flow diameter of 250mm in case of using a mini-slump cone [62]. Each test is repeated at
least three times, and an average of the observation is reported.
2.3.2. Mechanical Strength
Mortar Specimens of 40 mm × 40 mm × 160 mm were cast, cured, and tested per
EN196-1 standard [57]. The samples were placed in the moist cabinet (CURACEM M/S
Controls Italy Model 65-L0013/D), capable of maintaining the temperature at 20 ◦C and 95%
humidity immediately after casting. After 24 hours, the samples were demolded and placed
in CURACEM for curing at 20 ◦C till the day of testing. The samples tested for compression
and flexure, in saturated surface dry condition, in a compression testing machine (Flexure
frame model M/S Controls Italy 50-C1601/B attached with MCC8 Console) capable of
controlling load rate up to 1 N/s at the age of 3, 7, 14, 21, 28 and 56 days. Three specimens
were tested for flexure at each testing age and four specimens in compression for each
mix proportion.
2.3.3. Ultrasonic Pulse Velocity
Ultrasonic pulse velocities of the mortar specimens were recorded at the age of 3, 7,
14, 21, 28, and 56 days using an ultrasonic pulse velocity tester (M/S Controls Italy Model
58-E4800). During measurement of ultrasonic pulse velocity, compressive strength, and
flexural strength tests, working conditions (temperature, humidity, mix regime, filling)
were kept the same.
2.3.4. Microstructural Characterization
Scanning electron microscopy (SEM) is an advanced technique to elaborate the mi-
crostructure and phase composition of the cementitious hydration products [63–66]. In
this study, SEM was done by JSM-6390 and JSM-6700F (ultra-high resolution SEM; 1 nm
at 15 kV and 2.2 nm at 1 kV) (Jeol USA Inc., Peabody, MA, USA) [67,68]. For scanning
electron microscopy, small chips of mortar composite samples were obtained from the
broken pieces of the prism samples after their compression tests. The small chips were
coated with a layer of gold particles before the SEM observations. Several images for each
sample are taken to elaborate on different phases such as fully or partially hydrated or
residue raw materials, porosity interface between different hydration products, etc.
3. Results and Discussions
3.1. Rheological Properties
The results obtained from the experiments with their respective standard deviations
(SD) are reported in Table 3. The flow results indicate that all the formulations have
surpassed the targeted flow of 260 mm and exhibited maximum spread for the mortar
formulation containing 80% fly ash and 20% silica fume. All the mixed proportions with
silica fume exhibit no segregation and lixiviation. While T0 was well cohesive, but a little
bit of lixiviation was observed. As W/C and superplasticizer, the content was kept constant
for all mix proportions. Mix proportions with silica fume engaged water more efficiently.
The total spread of the mortar formulations represents the strong influence of relative
quantities of included SRMs in the mix (referred to Figure 2).
6. Crystals 2021, 11, 915 6 of 14
Table 3. Total flow spread, T250 time, and V-funnel times.
Mix Designation
Flow Spread T250 Time V-Funnel Time
mm SD s SD s SD
T0 285 3.61 22.1 1.56 31.7 2.14
T1 290 4.36 21.7 1.59 31.0 1.22
T2 330 5.29 11.3 1.33 25.2 1.91
T3 335 4.36 12.5 2.07 22.3 1.83
T4 345 3.61 12.5 0.64 19.3 1.52
T5 330 4.36 13.7 1.68 14.7 2.04
T6 290 7.21 15.2 1.88 10.5 1.41
Crystals 2021, 11, x FOR PEER REVIEW 7 of 15
Figure 2. Variation of flow spread with SF content.
The results of T250 indicate a sharp decrease in the flow time between 5% and 10%
silica fume replacement levels. Afterward, there is a slight increase in flow time. As silica
fume content increases from 5% to 10%, it increases the ball bearing effect; thus, the time
required to touch 250 mm circles reduces. Afterward, this effect is reduced due to the
increased viscosity of the mortar.
The relationship between T250 and V-funnel time for all the mortar formulations
with varying replacement levels of silica fume is presented in Figure 3. V-funnel time de-
creases with an increase in silica fume content. This may be attributed to the reduction in
internal friction and shear stress with the inclusion of silica fume.
Figure 3. Relationship of V-funnel time with T25 with varying silica fume content.
3.2. Mechanical Properties
The compressive strength results of the mortar formulations are presented in Figure
4. The total strength gain of mortar composites containing silica fume and fly ash is higher
than the control mix. This may be due to the pozzolanic activity of silica fume at the early
Figure 2. Variation of flow spread with SF content.
The mini-slump flow, which is a direct function of the yield stress of the formulation,
exhibited an increasing trend in the total flow with a small quantity of silica fume inclusion.
After 20% content, the total spread indicated a sharp reduction in the total flow. The
enhanced flow obtained from 20% inclusion of silica fume is attributed to the packing effect
achieved from the inclusion of ultra-fine particles of silica fume in the matrix of fly ash
particles and similarly filling effect of fly ash particles in the matrix of fine aggregates [69].
Further, the packing effect was more pronounced due to the spherical shape of sil-
ica fume and fly ash particles producing a ball-bearing effect. The lubricated spherical
particles produced efficient rolling with reduced intra-particle friction. The water and
superplasticizer contents were kept constant throughout the formulations; therefore, up to
20% replacement level lubrication was enough to achieve the rolling effect. After that, the
overall surface area of the powder content increased, requiring a higher amount of water
and superplasticizer for achieving the same workability level. Due to this effect, the total
spread gradually decreases after the replacement level of 20%. This phenomenon is also
evident from the T250 time.
The results of T250 indicate a sharp decrease in the flow time between 5% and 10%
silica fume replacement levels. Afterward, there is a slight increase in flow time. As silica
fume content increases from 5% to 10%, it increases the ball bearing effect; thus, the time
required to touch 250 mm circles reduces. Afterward, this effect is reduced due to the
increased viscosity of the mortar.
The relationship between T250 and V-funnel time for all the mortar formulations with
varying replacement levels of silica fume is presented in Figure 3. V-funnel time decreases
with an increase in silica fume content. This may be attributed to the reduction in internal
friction and shear stress with the inclusion of silica fume.
7. Crystals 2021, 11, 915 7 of 14
fume content increases from 5% to 10%, it increases the ball bearing effect; thus, the time
required to touch 250 mm circles reduces. Afterward, this effect is reduced due to the
increased viscosity of the mortar.
The relationship between T250 and V-funnel time for all the mortar formulations
with varying replacement levels of silica fume is presented in Figure 3. V-funnel time de-
creases with an increase in silica fume content. This may be attributed to the reduction in
internal friction and shear stress with the inclusion of silica fume.
Figure 3. Relationship of V-funnel time with T25 with varying silica fume content.
3.2. Mechanical Properties
The compressive strength results of the mortar formulations are presented in Figure
4. The total strength gain of mortar composites containing silica fume and fly ash is higher
than the control mix. This may be due to the pozzolanic activity of silica fume at the early
stage. However, the contribution of fly ash is less, and it only acts as a pore sealer. At a
later stage, the fly ash significantly contributes to the strength by reacting with free Ca
(OH)2 and converting it into calcium silicate hydrate. Strength for mix proportion T2 is
the highest for all ages, and it corresponds to 10% replacement of fly ash with silica fume.
This is the optimum value for the replacement of fly ash with silica fume. There is signif-
icant increase in strength from 28 to 56 days i.e., 15.9, 19.6%, 15.2%, 5.7%, 4.6%, 5.4%, and
10.16% from T0 to T6, respectively. A gain in delayed strength reduces with increasing the
Figure 3. Relationship of V-funnel time with T25 with varying silica fume content.
3.2. Mechanical Properties
The compressive strength results of the mortar formulations are presented in Figure 4.
The total strength gain of mortar composites containing silica fume and fly ash is higher
than the control mix. This may be due to the pozzolanic activity of silica fume at the early
stage. However, the contribution of fly ash is less, and it only acts as a pore sealer. At a
later stage, the fly ash significantly contributes to the strength by reacting with free Ca
(OH)2 and converting it into calcium silicate hydrate. Strength for mix proportion T2 is the
highest for all ages, and it corresponds to 10% replacement of fly ash with silica fume. This
is the optimum value for the replacement of fly ash with silica fume. There is significant
increase in strength from 28 to 56 days i.e., 15.9, 19.6%, 15.2%, 5.7%, 4.6%, 5.4%, and 10.16%
from T0 to T6, respectively. A gain in delayed strength reduces with increasing the level of
fly ash replacement. The possible reason is that the subsequent decrease in fly ash contents
limits the pozzolanic activity (known as the delayed effect of fly ash). The continuous
pozzolanic activity strengthens the interfacial transition zone by reducing pore sizes and
the packing effect phenomena by the excess unreacted fly ash particles and silica fume [3].
Crystals 2021, 11, x FOR PEER REVIEW 8 of 15
level of fly ash replacement. The possible reason is that the subsequent decrease in fly ash
contents limits the pozzolanic activity (known as the delayed effect of fly ash). The con-
tinuous pozzolanic activity strengthens the interfacial transition zone by reducing pore
sizes and the packing effect phenomena by the excess unreacted fly ash particles and silica
fume [3].
The flexural strength test results of the mortar formulations are reported in Figure 5
below. Usually, cementitious composites are extraordinarily strong in compression and
weak in flexure, i.e., ten times weaker than compressive strength. In the present investi-
gation, the flexural strength patterns are much like results of compressive strength.
Maximum flexural strength was obtained with the mix proportion T2. Maximum
flexural strengths were achieved at 28 and 56 days, at 19.15+ and 20.86 + 0.5 MPa, respec-
tively, which is about 19% and 18% of their corresponding compressive strengths. The
relationship between compressive strength and flexural strength of cementitious compo-
sites is a matter of interest for researchers and structural designers. Different relationships
for various cementitious composites are proposed by many researchers and adopted by
the code forming committees. A famous relationship as adopted by ACI is given as fol-
lows [70].
= × (1)
Figure 4. Compressive strength of mortar composites with varying fly ash and silica fume content.
Figure 4. Compressive strength of mortar composites with varying fly ash and silica fume content.
The flexural strength test results of the mortar formulations are reported in Figure 5 be-
low. Usually, cementitious composites are extraordinarily strong in compression and weak
in flexure, i.e., ten times weaker than compressive strength. In the present investigation,
the flexural strength patterns are much like results of compressive strength.
8. Crystals 2021, 11, 915 8 of 14
Figure 4. Compressive strength of mortar composites with varying fly ash and silica fume content.
Figure 5. Flexural strength of mortar composites with varying fly ash and silica fume content.
Figure 5. Flexural strength of mortar composites with varying fly ash and silica fume content.
Maximum flexural strength was obtained with the mix proportion T2. Maximum flex-
ural strengths were achieved at 28 and 56 days, at 19.15+ and 20.86 + 0.5 MPa, respectively,
which is about 19% and 18% of their corresponding compressive strengths. The relationship
between compressive strength and flexural strength of cementitious composites is a matter
of interest for researchers and structural designers. Different relationships for various
cementitious composites are proposed by many researchers and adopted by the code
forming committees. A famous relationship as adopted by ACI is given as follows [70].
fr = n ×
p
f 0
c (1)
The linear regression analysis of the mortar composites samples indicates that the ACI
relationship for predicting the flexural strength holds good for the present research (refer
to the supplementary data for linear regression analysis).
3.3. Ultrasonic Pulse Velocity (UPV)
UPV is an innovative non-destructive technique to measure the mechanical properties
of cementitious composites. The results of ultrasonic pulse velocity for a few mix propor-
tions are shown in Figure 6. It was observed that the specimens with only fly ash have the
lowest UPV, and samples with a 10% replacement level have a maximum. These results are
in close agreement with the mechanical properties. The difference between samples with
and without silica fume narrows down at the age of 56 days because hydration products
fill voids due to the delayed pozzolanic activity of fly ash [71,72]. The compressive and
flexural strength of the SCM composite can be correlated with UPV by an exponential
function. Two different models were proposed after analysis of data, one for estimation of
compressive strength and the other for flexural strength.
3.3.1. Mathematical Model for Estimation of Compressive Strength
The proposed model for the estimation of compressive strength from UPV is shown in
Equation (2). This model is valid for all mix proportions with silica fume at 28 and 56 days.
The maximum error is 4.93 + 0.65% and 8.94+0.30% at 28 and 56 days, respectively.
fc = 1.68 e0.92(UPV)
(2)
For mix proportion without silica fume up to an age of 28 days, the error is relatively
high, more than 50%, but at the age of 56 days, this error reduces to 14.7 + 4.4%. It is
due to the delayed pozzolanic activity of fly ash. These hydration products have filled up
the micro and nanosized pores, and UPV is comparable with mix proportions containing
silica fume.
9. Crystals 2021, 11, 915 9 of 14
3.3.1. Mathematical Model for Estimation of Compressive Strength
The proposed model for the estimation of compressive strength from UPV is shown
in equation 2. This model is valid for all mix proportions with silica fume at 28 and 56
days. The maximum error is 4.93 + 0.65% and 8.94+0.30% at 28 and 56 days, respectively.
fc = 1.68 e0.92(UPV)
(2)
Figure 6. UPV for various mix proportions.
For mix proportion without silica fume up to an age of 28 days, the error is relatively
high, more than 50%, but at the age of 56 days, this error reduces to 14.7 + 4.4%. It is due
to the delayed pozzolanic activity of fly ash. These hydration products have filled up the
micro and nanosized pores, and UPV is comparable with mix proportions containing sil-
ica fume.
3.3.2. Mathematical Model for Estimation of Flexural Strength
The proposed model for the estimation of flexural strength from UPV is shown in
equation 3. This model is valid for all mix proportions with silica fume at 28 and 56 days.
The maximum error is 5.5 ± 0.76% and 9.1 ± 0.87% at 28 and 56 days, respectively.
fr = 0.042 e1.37(UPV) (3)
Figure 6. UPV for various mix proportions.
3.3.2. Mathematical Model for Estimation of Flexural Strength
The proposed model for the estimation of flexural strength from UPV is shown in
Equation (3). This model is valid for all mix proportions with silica fume at 28 and 56 days.
The maximum error is 5.5 ± 0.76% and 9.1 ± 0.87% at 28 and 56 days, respectively.
fr = 0.042 e1.37(UPV)
(3)
For mix proportion without silica fume up to 28 days, the error is relatively high—
more than 35%—but at the age of 56 days, this error reduces to 1.2 ± 0.3%. The reason has
already been explained in the case of compressive strength.
3.4. Microstructural Characterization
The micrographs for the mix proportions T0 to T6 are presented in Figure 7a–g,
respectively. The SEM micrographs show various hydration products as well as partially
reacted and unreacted fly ash particles. Typical hydration products, including calcium-
silicate-hydrate (CSH) gel and calcium hydroxide (CH), have been identified in the SEM
images. Figure 7a is a micrograph for mix proportion T0, which contains only fly ash as
SRM. The micrograph shows a flocculent and porous structure with unreacted fly ash
particles as well. CSH gel and CH are present as hydration products. Many pores are
present within the cementitious matrix.
Figure 7b is the micrograph of mix proportion T1, which corresponds to 95% of fly
ash and 5% of silica fume as SRM. The micrograph shows a denser microstructure as
compared to T0. The dense microstructure of the composites with silica fume incorporation
is attributed to the pore filling effect (due to the smaller particle size of silica fume than
OPC) and secondary hydrates formation [21]. The presence of high amounts of amorphous
silica (as shown in Table 1 in the XRF results) is responsible for reaction with calcium
hydroxide crystals at a later age. Reduced portlandite amount and increased gel formation
are, thus, expected, which leads to lower total porosity and higher compressive strength.
Figure 7c is the micrograph for mix proportion T2, which corresponds to 90% FA and 10%
SF as SRMs. The microstructure is dense and well compacted, with a few minor cracks
indicating strong interface contact between the hydration products. This indicates the
pozzolanic reaction; secondary hydration products have filled the pores and improved the
interfacial properties. It is also evident from compressive and flexural strength results. The
highest strength results are related to this mix proportion. Figure 7d corresponds to the
mix proportion T3, which contained 85% of fly ash and 15% of silica fume. Even denser
microstructure in T2 is seen. Interfacial separation is also observed. Figure 7e–g correspond
to the mix proportion T4 (which contains 80% FA and 20% SF), T5 (which contains 75% FA
10. Crystals 2021, 11, 915 10 of 14
and 25% of SF), and T6 (which has 70% FA and 30% SF. At some points, large voids with a
weak interface between hydration products have been observed.
Crystals 2021, 11, x FOR PEER REVIEW 11 of 15
Figure 7. Scanning electron micrographs of mortar composites (a) T0, (b) T1, (c) T2, (d) T3, (e) T4, (f)
T5 and (g) T6.
Figure 7b is the micrograph of mix proportion T1, which corresponds to 95% of fly
ash and 5% of silica fume as SRM. The micrograph shows a denser microstructure as com-
pared to T0. The dense microstructure of the composites with silica fume incorporation is
attributed to the pore filling effect (due to the smaller particle size of silica fume than OPC)
and secondary hydrates formation [21]. The presence of high amounts of amorphous silica
(as shown in Table 1 in the XRF results) is responsible for reaction with calcium hydroxide
crystals at a later age. Reduced portlandite amount and increased gel formation are, thus,
Figure 7. Scanning electron micrographs of mortar composites (a) T0, (b) T1, (c) T2, (d) T3, (e) T4,
(f) T5 and (g) T6.
4. Conclusions
In this study, the role of fly ash replacement with silica fume on fresh and hardened
properties of SCM with a moderate volume of fly ash is presented. From the results of this
study, the following conclusions may be drawn.
11. Crystals 2021, 11, 915 11 of 14
• Replacing fly ash with silica fume gradually increases the flow spread up to 20%
replacement level. After that, a decline is observed. Therefore, the optimum blend for
maximum spread is 20% silica fume with 80% fly ash content.
• Superplasticizer used in this study was polycarboxylate-based and suitable for in-
creasing the workability of SCMs.
• It is concluded that with the high dosage of silica fume, cement content and super-
plasticizer may be increased to achieve the target flow.
• T250 time gradually decreases up to 20% replacement level and then starts increasing.
This result is in line with the results of flow spread and indicates that the flow spread
and the rate of flow decrease after 20% replacement level.
• V- funnel’s time gradually decreases with the increase of silica fume content, indicating
that increase of silica fume content enhances the vertical movement of particles by
reducing air bubbles, which interfere with the vertical movement of paste. This result
complements the results of flow spread and T25 time.
• Proposed models for estimation of compressive and flexure strength from UPV are
valid for all mix proportions containing silica fume at the age of 28 and 56 days. For
mix proportion containing only fly ash, these are valid for 56 days only. These models
can be used to predict the strength of high-strength self-compacting mortar containing
fly ash and silica fume.
• The optimum powder content to obtain maximum compressive and flexural strength
is 80% of OPC, 18% fly ash, and 2% silica fume.
• Flexural strength follows the compressive strength trend, i.e., the optimum replace-
ment level of fly ash is 10%. Highest achieved flexural strength was 20.86 ± 0.5MPa
for mix proportion T2, i.e., 90% FA and 10% SF. Same as compressive strength results
gain in flexural strength can be correlated by a power law.
High-strength mortar developed in this study can be used for repair, maintenance,
retrofitting, and strengthening of existing reinforced concrete and structures. It can also
be used as the matrix for ferrocement and laminated cementitious composites. Studies on
optimal amounts of ternary and quaternary blends containing new SRMs [73–75] should
be further investigated.
Author Contributions: Conceptualization, M.T.A.; Methodology, M.T.A.; Format analysis, M.T.A.
and A.K.; Investigation, M.T.A.; Writing-Original draft preparation, M.T.A.; Partial resources, M.T.A.
and S.A.; Validation of Results, S.A.; Supervision, S.A.; Writing-Review and editing, A.K. and A.H.;
Data curation, A.K. and A.H.; Project administration, A.H.; Funding acquisition, A.H. All authors
have read and agreed to the published version of the manuscript.
Funding: Funding support from China National Key RD Program—Intergovernmental Interna-
tional Scientific and Technological Innovation Cooperation Key Project, “Research on the application
and demonstration of the green construction materials for the post-disaster reconstruction in Pakistan
and Nepal”, Grant No. 2018YFE0106300, 2019.07-2022.06, is gratefully acknowledged.
Acknowledgments: The authors acknowledge the support of laboratory staff of Department of
Civil Engineering at Mirpur university of Science and Technology (MUST), Mirpur, AJK, and
University of Engineering and Technology (UET), Taxila during experimentations. In addition,
technical help in doing the SEM imaging from HKUST, Hong Kong by Pavithra Parthasarathy is
gratefully acknowledged.
Conflicts of Interest: The authors declare no conflict of interest of any kind.
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