Shotcrete is a cement-based concrete that is pneumatically projected at high velocity onto underground excavation surfaces for rock support. There are two main types - dry mix, where materials are conveyed dry to the nozzle and water added, and wet mix, where materials are pre-mixed with water. Recent developments include adding steel fibers for reinforcement and microsilica for strength. Shotcrete provides effective support in mining when applied correctly using proper equipment and experienced operators. It is increasingly used for permanent openings and offers advantages over traditional rockbolt and mesh support.
Standalone Vertical Roller Mills Without HGGLOESCHE
This document summarizes a new vertical roller mill technology for cement grinding that can operate without the need for water injection or a hot gas generator. The technology was implemented in two cement grinding stations in India built by Ambuja Cement. Key features of the new technology include a grinding system using a 'S' support roller and 'M' master roller to stabilize the grinding bed without water. Initial performance results for the Dadri station met or exceeded guarantees for production rate, fineness, and product moisture content without requiring permanent operation of a hot gas generator.
The first six-roller Loesche mill for grinding cement raw material was successfully put into operation in July 2008 (see Figure 1). The grinding plant is part of the new production line in the Tadipatri works of the second largest cement manufacturer in India, Grasim Industries Ltd, Mumbai and its subsidiary UltraTech Cement Ltd. Around 16,000t of cement raw material must be ground every day to supply the new kiln which has a cement clinker capacity of 10,000tpd.
The EZstrip™ Cake Pump features a specially designed feed chamber that can easily be disconnected allowing access to the rotating assembly. The rotor can be separated from the conveyor allowing removal of the rotor and stator all within its own assembled length. This process can take as little as 6 minutes!
This document provides information on concrete additives from the company ISOMAT. It discusses several of their additive products, including ADIUM brands of polycarboxylate-based additives that improve properties like water reduction and flowability. The document provides descriptions, applications, consumption guidelines and packaging details for specific additives like ADIUM 110, 130, 132, 145, and 150. It also compares the performance of reference concrete mixes to mixes using these additives, showing improvements in slump retention and compressive strength.
The document discusses hose pumps called King Cobra pumps that can handle tough fluid transfer needs. They have a simple seal-free design that is dry-run capable and reliable. They can discharge pressures up to 15 bar, making them ideal for applications like ceramics that require higher pressures. They are durable, easy to maintain, and suitable for dosing and transferring abrasive or sensitive materials.
Molykote Cu 7439 Plus is an anti-seize lubricating paste designed for steel mill applications. It is copper-based with synthetic oil and corrosion inhibitors. It provides long-term lubrication up to 300C and dry lubrication up to 650C. It is highly adhesive, resistant to water and corrosion, and maintains lubrication in harsh environments with high temperatures, pressures, and water exposure. As a single product, it can be used for lubrication and anti-seize needs in various steel mill components.
Pigs Unlimited International, Inc. is dedicated to serving the pipeline industry by solving the pigging needs of our customers. We not only strive to meet the expectations of our customers, but exceed them. We are constantly striving to find new ways to offer the best pig at the best price, coupled with unsurpassed service.
Twin shaft mixers are equipped with double synchronized mixing spiral. This structure allow excellent concrete mixing with short mixing and discharge times.
Standalone Vertical Roller Mills Without HGGLOESCHE
This document summarizes a new vertical roller mill technology for cement grinding that can operate without the need for water injection or a hot gas generator. The technology was implemented in two cement grinding stations in India built by Ambuja Cement. Key features of the new technology include a grinding system using a 'S' support roller and 'M' master roller to stabilize the grinding bed without water. Initial performance results for the Dadri station met or exceeded guarantees for production rate, fineness, and product moisture content without requiring permanent operation of a hot gas generator.
The first six-roller Loesche mill for grinding cement raw material was successfully put into operation in July 2008 (see Figure 1). The grinding plant is part of the new production line in the Tadipatri works of the second largest cement manufacturer in India, Grasim Industries Ltd, Mumbai and its subsidiary UltraTech Cement Ltd. Around 16,000t of cement raw material must be ground every day to supply the new kiln which has a cement clinker capacity of 10,000tpd.
The EZstrip™ Cake Pump features a specially designed feed chamber that can easily be disconnected allowing access to the rotating assembly. The rotor can be separated from the conveyor allowing removal of the rotor and stator all within its own assembled length. This process can take as little as 6 minutes!
This document provides information on concrete additives from the company ISOMAT. It discusses several of their additive products, including ADIUM brands of polycarboxylate-based additives that improve properties like water reduction and flowability. The document provides descriptions, applications, consumption guidelines and packaging details for specific additives like ADIUM 110, 130, 132, 145, and 150. It also compares the performance of reference concrete mixes to mixes using these additives, showing improvements in slump retention and compressive strength.
The document discusses hose pumps called King Cobra pumps that can handle tough fluid transfer needs. They have a simple seal-free design that is dry-run capable and reliable. They can discharge pressures up to 15 bar, making them ideal for applications like ceramics that require higher pressures. They are durable, easy to maintain, and suitable for dosing and transferring abrasive or sensitive materials.
Molykote Cu 7439 Plus is an anti-seize lubricating paste designed for steel mill applications. It is copper-based with synthetic oil and corrosion inhibitors. It provides long-term lubrication up to 300C and dry lubrication up to 650C. It is highly adhesive, resistant to water and corrosion, and maintains lubrication in harsh environments with high temperatures, pressures, and water exposure. As a single product, it can be used for lubrication and anti-seize needs in various steel mill components.
Pigs Unlimited International, Inc. is dedicated to serving the pipeline industry by solving the pigging needs of our customers. We not only strive to meet the expectations of our customers, but exceed them. We are constantly striving to find new ways to offer the best pig at the best price, coupled with unsurpassed service.
Twin shaft mixers are equipped with double synchronized mixing spiral. This structure allow excellent concrete mixing with short mixing and discharge times.
FMT, Inc. is a 100+ employee company that designs and manufactures integrated parts cleaning systems. They have 7 divisions and serve industries such as aerospace, automotive, appliances, and more. They have an in-house engineering team that designs custom cleaning solutions. Their standard washers include belt/chain, rotary basket, rotary table, rotary drum, engine block, monorail, immersion/agitation, and ultrasonic washers.
Molykote® Greases in action in India, email sales@projectsalescorp.comProject Sales Corp
No matter how harsh the environment or how extreme the temperature, you’re sure to find a Molykote® brand lubricant worthy of the challenge. When you specify maintenance products from Dow Corning, you’re specifying the results of more than 60 years of innovations by a world leader in lubrication technology. With dedicated global research and development operations, Molykote brand lubricants from Dow Corning bring you the best in assembly and maintenance technology from around the world. Our knowledgeable sales professionals will help you choose the right lubricating product for your unique maintenance needs.
Now get Molykote products from India'a leading distributor for Molykote products - Project Sales Corporation.
The Universal Mag Drive pump by Viking provides a dimensionally interchangeable footprint with Viking's Universal Seal and Heavy Duty Bracketed pumps, allowing for an easy upgrade from packing or mechanical seals to a sealless Mag Drive design. This sealless design eliminates pump seal maintenance issues and provides the highest level of liquid containment available. The Mag Drive is suitable for pumping hard-to-seal, hazardous, and reactive liquids in continuous processing applications.
CS Unitec offers a line of portable mixers and mixing stations for construction jobsites. Their mixers are designed for reliability and power to blend various construction materials. Larger mixers can mix quantities up to 200 pounds, while portable mixing stations allow one person to mix, transport, and pour materials directly onto the floor. CS Unitec also provides dust extraction vacuums and concrete grinders to work with their mixers for complete mixing and surface preparation solutions.
This document provides technical specifications and application details for RV Rubber Reclaiming Agent, which is used to revive vulcanized rubber through a process called RV revived rubber technique. The agent works by reducing the bond energy of sulfur-sulfur crosslinks without destroying other bonds, restoring the rubber's activity. The revived rubber can then be vulcanized without additional agents. The RV agent is applicable to various rubber types, has advantages like being non-toxic and reducing costs, and provides recycled rubber with better properties than other reclaiming methods. A second generation agent was also developed that uses mechanochemical chain scission to depolymerize the rubber.
Centrifugal Pump Different Medium(Water or acid water, corrosive slurry pump)...Marina Xu
This document provides information on pump models and specifications from Hebei Yifan Industry Pump Co., Ltd. They produce 15 series and 358 models of slurry pumps, sewage pumps, gravel pumps, and desulfurization pumps. The pumps are used in industries like mining, metallurgy, power plants, sewage treatment, and dredging. The company has capabilities for casting various materials and strict quality control systems. Key pump series described include YH horizontal slurry pumps, SP vertical slurry pumps, ZJ slurry pumps, and desulfurization pump models. Specifications like size ranges, flow rates, heads, and materials are provided for several pump types.
Shortcreting has proved to be the best method for construction of curved surfaces. Domes are now much easier to construct with the advent of shotcrete technology. Tunnel linings are also becoming easy with this technology. Not only are these but there a wide range of applications where this technology has been a leading one. This technical paper includes the concept of shotcrete and how it differs from conventional concrete. It also enumerates the different types of process involved in shotcreting i.e. dry mix process and wet mix process. Advantages of shotcrete and its applications in various fields like tunneling, canals, buildings etc. are specified in detail. This paper presents an overview of shotcreting technology along with its applications.
DEFINITION OF SHOTCRETE:-
Shotcrete is a mortar or high performance concrete conveyed through a hose and pneumatically projected at high velocity onto a backing surface. It is the force of this spraying action that leads to compaction of the concrete or mortar which then forms layers of concrete to the required thickness. Shotcreting has been an acceptable way of placing cementitious material in a variety of applications.
Usually patented polypropylene fibers are included in the shotcrete which increases the cohesive nature of the shotcrete through mechanically binding the cementitious materials together. This mechanism reduces the rebound waste that occurs through the shotcreting process and these fibers also resist plastic shrinkage and cracking through their ability to enhance the early stage tensile strength of concrete.
Shotcrete also gives better surface finishes and reduces surface tearing on non- linear sections. Cementitious material containing the poly propylene fibers resist cycles of freezing and thawing and also reduces the chances of water and chemical penetrations.
Shotcrete is a concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a backing surface. It was invented in the early 1900s and has emerged as the preferred industry term to describe pneumatically applied concrete. There are two main processes - dry mix and wet mix. Dry mix involves pre-blended dry or semi-damp materials conveyed via air to the nozzle, while wet mix fully mixes all ingredients before projection. Shotcrete provides benefits over conventional concrete like density, homogeneity, strength, and ability to apply to any surface. It is widely used for rehabilitation of subway tunnels, domed roofs, highway culvert repair, and new concrete construction.
Shotcrete is a concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a surface. It was invented in the early 1900s and has emerged as the preferred industry term to describe pneumatically applied concrete. There are two main processes for shotcrete - dry mix and wet mix. The dry mix process involves pre-blended dry materials added to water at the nozzle, while the wet mix fully mixes all materials beforehand. Shotcrete provides benefits over traditional cast-in-place concrete like better density, homogeneity, strength, and ability to be used on complex surfaces. Its use for new construction and repair of structures continues to grow due to its versatility.
Shotcrete is concrete projected through a hose at high velocity using compressed air. It was invented in 1910 by Carl Ethan Akeley to reproduce dinosaur fossils in concrete. Shotcrete is mainly used in underground construction and can be applied either dry or wet. It offers benefits over traditional cast-in-place concrete like speed of construction, ability to build complex shapes, cost-effectiveness, and suitability for areas with limited access. However, proper planning, supervision, and skilled application are needed for successful shotcrete projects.
Shotcrete, or sprayed concrete, was first used in 1907 and involves pneumatically projecting a concrete or mortar mixture at high velocity onto a surface. There are two main processes - dry process involves adding water at the nozzle, while wet process fully mixes all ingredients beforehand. Shotcrete provides advantages for constructing curved surfaces like domes and tunnels efficiently due to its ability to be sprayed onto irregular surfaces with little formwork needed. It allows for material placement in hard to access areas.
Este documento proporciona información sobre shotcrete o concreto proyectado, incluyendo su definición, historia, ventajas, materiales necesarios, proceso de aplicación, usos comunes y patologías potenciales. El shotcrete es un proceso en el que el concreto se proyecta a alta velocidad sobre una superficie usando aire comprimido. Se usa comúnmente para estabilizar taludes, construir túneles y como soporte estructural temporal o permanente. La calidad del shotcrete depende de factores como la técnica
A Review Paper on Re-vibration of Fly Ash ConcreteIRJET Journal
This document summarizes a research paper that studied the effect of re-vibration on fly ash concrete. It found that re-vibrating concrete after initial vibration at time intervals between 30 minutes to 2 hours improved properties like compressive strength, surface hardness, and permeability. The maximum compressive strength was achieved with re-vibration after 2 hours. Re-vibration helps fill voids, removes air, and rearranges aggregates, leading to stronger, denser concrete. While re-vibration is beneficial if done properly, disturbing partially set concrete can reduce strength. The study concluded that fly ash concrete can provide environmental and strength benefits when re-vibrated at an early age.
Studying the Influence of Polycarboxylic Ether on Properties of ConcreteIRJET Journal
This document discusses how polycarboxylic ether affects the properties of concrete. It studies the influence of different dosages of polycarboxylic ether superplasticizer on the compressive strength and slump loss of M30 grade concrete with a 0.35 water-cement ratio. The optimal dosage is reported as the amount that produces the highest compressive strength after 7 and 28 days, and minimum slump loss. The results showed that polycarboxylic ether was most effective at dosages of 0.8% for compressive strength and 0.9% by cement weight for slump loss.
This document discusses the components, composition, and application of shotcrete used in NATM tunnel construction. It describes the requirements for shotcrete mixes, including low water permeability and minimum early strength. Early strength can be achieved through the use of spray bonding agents or alkali-free accelerating admixtures. Shotcrete is typically applied using either a dry-mix or wet-mix method. Wet-mix shotcrete is now preferred over dry-mix due to lower rebound, dust, and higher application rates. The document also discusses achieving different early strength classes and final strengths of 28-40MPa through the use of alkali-free additives.
Partial Replacement of Cement by Fly ash in Concrete Mix DesignIRJET Journal
This document discusses the partial replacement of cement with fly ash in concrete mix design. It begins with an abstract stating that concrete is an important construction material and that adding other materials can change its properties. The document then discusses how fly ash is a byproduct of coal combustion that can be used to partially substitute cement. When used in concrete, fly ash improves strength properties while requiring less energy to produce than ordinary Portland cement. The document provides details on fly ash classification, properties, advantages of using fly ash in concrete, and provides an example mix design showing the reduced quantities of cement, water and fine aggregate needed when partially substituting cement with fly ash.
This document summarizes a seminar on utilizing industrial waste in self-compacting concrete. It defines concrete and self-compacting concrete. Self-compacting concrete was developed in Japan in the 1980s to improve quality and flows under its own weight without vibration. The document discusses types of self-compacting concrete and advantages like improved filling and reduced labor. Tests to check suitability include slump flow, V-funnel, L-box, and U-box. Red mud and foundry sand were used to replace cement in mixtures and provided strength gains. Test results showed compressive strength up to 44 MPa and tensile strength up to 4.62 MPa with red mud additions of 2%. Foundry sand
IRJET- An Experimental Study on Air Entrained Mortar by Utilising Lather AgentIRJET Journal
This document presents research on producing an air-entrained mortar utilizing sugarcane ash and a lather agent. Mortar samples were produced with 10%, 30%, and 50% cement replaced by sugarcane ash. The samples were tested for compressive strength and water absorption at 7, 14, and 28 days. Results showed compressive strengths of 11.2 MPa, 8.5 MPa, and 7.3 MPa respectively for the 10%, 30%, and 50% sugarcane ash replacements compared to 12.5 MPa for a conventional mortar. Water absorption also increased with higher sugarcane ash content. The study concludes the mortar produced is beneficial due to lower cost and weight while being
Millet Husk Ash as Partial Replacement of Cement in Sandcrete BlockIRJET Journal
This document summarizes a study that investigated using millet husk ash (MHA) as a partial replacement for cement in sandcrete blocks. The study examined the physical and chemical properties of locally sourced MHA and found it met requirements to be considered a pozzolanic material. Sandcrete blocks were produced with 0%, 10%, 20%, 30%, and 40% replacements of cement with MHA. Testing found blocks with 10% and 20% replacements met minimum strength requirements while higher replacements reduced strength. The 20% replacement was determined to be optimal as it provided sufficient strength while reducing cement usage.
IRJET - Experimental Investigation on No-Fines Concrete with Tyre as a Partia...IRJET Journal
This document summarizes an experimental investigation on no-fines concrete with tire rubber as a partial replacement for coarse aggregate and sodium silicate as an admixture. No-fines concrete is a lightweight concrete that does not contain fine aggregates. The study aims to determine the optimum mix of no-fines concrete for partial replacement of coarse aggregate with tire rubber based on compressive, split tensile, and flexural strength testing. Various mix designs were tested where coarse aggregate was replaced by tire rubber at rates of 2.5%, 5%, and 7.5% by weight. The specimens were tested after 7, 14, and 28 days of curing and results were compared to conventional no-fines concrete. The results showed
Effect of Steel Fibre and Marble Dust on the Mechanical Properties of High St...IRJET Journal
This document discusses a study on the effect of adding steel fibers and marble dust to high-strength concrete. The researchers tested concrete mixtures with 0%, 15%, 30%, 45%, and 60% marble dust replacing sand and 0.8% steel fibers added. Based on the results, replacing up to 45% of the sand with marble dust and adding 0.8% steel fibers improved the compressive, flexural, and split tensile strengths of the concrete compared to the control mixture. Compressive strength and split tensile strength started decreasing when the marble dust replacement exceeded 15%. Therefore, the study concluded that replacing up to 45% marble dust and adding 0.8% steel fibers is an appropriate amount to improve mechanical properties of
I-sand: An Environmental Friendly Sand used in Reinforced Cement Concrete Con...IRJET Journal
This document discusses the use of iron sand (I-sand) as a partial replacement for river sand in reinforced cement concrete construction. It aims to provide an overview of research on utilizing iron sand to improve the performance of concrete while reducing the environmental impact of river sand extraction.
The key points discussed are:
1) River sand extraction has environmental concerns while demand is high, so alternative materials are needed. Iron sand is being researched as it can benefit construction and waste recycling.
2) Experimental concrete mixes were prepared with 0-30% river sand replaced by iron sand. Compressive strength generally increased with higher iron sand content, exceeding controls with over 10% replacement.
3) Workability decreased
FMT, Inc. is a 100+ employee company that designs and manufactures integrated parts cleaning systems. They have 7 divisions and serve industries such as aerospace, automotive, appliances, and more. They have an in-house engineering team that designs custom cleaning solutions. Their standard washers include belt/chain, rotary basket, rotary table, rotary drum, engine block, monorail, immersion/agitation, and ultrasonic washers.
Molykote® Greases in action in India, email sales@projectsalescorp.comProject Sales Corp
No matter how harsh the environment or how extreme the temperature, you’re sure to find a Molykote® brand lubricant worthy of the challenge. When you specify maintenance products from Dow Corning, you’re specifying the results of more than 60 years of innovations by a world leader in lubrication technology. With dedicated global research and development operations, Molykote brand lubricants from Dow Corning bring you the best in assembly and maintenance technology from around the world. Our knowledgeable sales professionals will help you choose the right lubricating product for your unique maintenance needs.
Now get Molykote products from India'a leading distributor for Molykote products - Project Sales Corporation.
The Universal Mag Drive pump by Viking provides a dimensionally interchangeable footprint with Viking's Universal Seal and Heavy Duty Bracketed pumps, allowing for an easy upgrade from packing or mechanical seals to a sealless Mag Drive design. This sealless design eliminates pump seal maintenance issues and provides the highest level of liquid containment available. The Mag Drive is suitable for pumping hard-to-seal, hazardous, and reactive liquids in continuous processing applications.
CS Unitec offers a line of portable mixers and mixing stations for construction jobsites. Their mixers are designed for reliability and power to blend various construction materials. Larger mixers can mix quantities up to 200 pounds, while portable mixing stations allow one person to mix, transport, and pour materials directly onto the floor. CS Unitec also provides dust extraction vacuums and concrete grinders to work with their mixers for complete mixing and surface preparation solutions.
This document provides technical specifications and application details for RV Rubber Reclaiming Agent, which is used to revive vulcanized rubber through a process called RV revived rubber technique. The agent works by reducing the bond energy of sulfur-sulfur crosslinks without destroying other bonds, restoring the rubber's activity. The revived rubber can then be vulcanized without additional agents. The RV agent is applicable to various rubber types, has advantages like being non-toxic and reducing costs, and provides recycled rubber with better properties than other reclaiming methods. A second generation agent was also developed that uses mechanochemical chain scission to depolymerize the rubber.
Centrifugal Pump Different Medium(Water or acid water, corrosive slurry pump)...Marina Xu
This document provides information on pump models and specifications from Hebei Yifan Industry Pump Co., Ltd. They produce 15 series and 358 models of slurry pumps, sewage pumps, gravel pumps, and desulfurization pumps. The pumps are used in industries like mining, metallurgy, power plants, sewage treatment, and dredging. The company has capabilities for casting various materials and strict quality control systems. Key pump series described include YH horizontal slurry pumps, SP vertical slurry pumps, ZJ slurry pumps, and desulfurization pump models. Specifications like size ranges, flow rates, heads, and materials are provided for several pump types.
Shortcreting has proved to be the best method for construction of curved surfaces. Domes are now much easier to construct with the advent of shotcrete technology. Tunnel linings are also becoming easy with this technology. Not only are these but there a wide range of applications where this technology has been a leading one. This technical paper includes the concept of shotcrete and how it differs from conventional concrete. It also enumerates the different types of process involved in shotcreting i.e. dry mix process and wet mix process. Advantages of shotcrete and its applications in various fields like tunneling, canals, buildings etc. are specified in detail. This paper presents an overview of shotcreting technology along with its applications.
DEFINITION OF SHOTCRETE:-
Shotcrete is a mortar or high performance concrete conveyed through a hose and pneumatically projected at high velocity onto a backing surface. It is the force of this spraying action that leads to compaction of the concrete or mortar which then forms layers of concrete to the required thickness. Shotcreting has been an acceptable way of placing cementitious material in a variety of applications.
Usually patented polypropylene fibers are included in the shotcrete which increases the cohesive nature of the shotcrete through mechanically binding the cementitious materials together. This mechanism reduces the rebound waste that occurs through the shotcreting process and these fibers also resist plastic shrinkage and cracking through their ability to enhance the early stage tensile strength of concrete.
Shotcrete also gives better surface finishes and reduces surface tearing on non- linear sections. Cementitious material containing the poly propylene fibers resist cycles of freezing and thawing and also reduces the chances of water and chemical penetrations.
Shotcrete is a concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a backing surface. It was invented in the early 1900s and has emerged as the preferred industry term to describe pneumatically applied concrete. There are two main processes - dry mix and wet mix. Dry mix involves pre-blended dry or semi-damp materials conveyed via air to the nozzle, while wet mix fully mixes all ingredients before projection. Shotcrete provides benefits over conventional concrete like density, homogeneity, strength, and ability to apply to any surface. It is widely used for rehabilitation of subway tunnels, domed roofs, highway culvert repair, and new concrete construction.
Shotcrete is a concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a surface. It was invented in the early 1900s and has emerged as the preferred industry term to describe pneumatically applied concrete. There are two main processes for shotcrete - dry mix and wet mix. The dry mix process involves pre-blended dry materials added to water at the nozzle, while the wet mix fully mixes all materials beforehand. Shotcrete provides benefits over traditional cast-in-place concrete like better density, homogeneity, strength, and ability to be used on complex surfaces. Its use for new construction and repair of structures continues to grow due to its versatility.
Shotcrete is concrete projected through a hose at high velocity using compressed air. It was invented in 1910 by Carl Ethan Akeley to reproduce dinosaur fossils in concrete. Shotcrete is mainly used in underground construction and can be applied either dry or wet. It offers benefits over traditional cast-in-place concrete like speed of construction, ability to build complex shapes, cost-effectiveness, and suitability for areas with limited access. However, proper planning, supervision, and skilled application are needed for successful shotcrete projects.
Shotcrete, or sprayed concrete, was first used in 1907 and involves pneumatically projecting a concrete or mortar mixture at high velocity onto a surface. There are two main processes - dry process involves adding water at the nozzle, while wet process fully mixes all ingredients beforehand. Shotcrete provides advantages for constructing curved surfaces like domes and tunnels efficiently due to its ability to be sprayed onto irregular surfaces with little formwork needed. It allows for material placement in hard to access areas.
Este documento proporciona información sobre shotcrete o concreto proyectado, incluyendo su definición, historia, ventajas, materiales necesarios, proceso de aplicación, usos comunes y patologías potenciales. El shotcrete es un proceso en el que el concreto se proyecta a alta velocidad sobre una superficie usando aire comprimido. Se usa comúnmente para estabilizar taludes, construir túneles y como soporte estructural temporal o permanente. La calidad del shotcrete depende de factores como la técnica
A Review Paper on Re-vibration of Fly Ash ConcreteIRJET Journal
This document summarizes a research paper that studied the effect of re-vibration on fly ash concrete. It found that re-vibrating concrete after initial vibration at time intervals between 30 minutes to 2 hours improved properties like compressive strength, surface hardness, and permeability. The maximum compressive strength was achieved with re-vibration after 2 hours. Re-vibration helps fill voids, removes air, and rearranges aggregates, leading to stronger, denser concrete. While re-vibration is beneficial if done properly, disturbing partially set concrete can reduce strength. The study concluded that fly ash concrete can provide environmental and strength benefits when re-vibrated at an early age.
Studying the Influence of Polycarboxylic Ether on Properties of ConcreteIRJET Journal
This document discusses how polycarboxylic ether affects the properties of concrete. It studies the influence of different dosages of polycarboxylic ether superplasticizer on the compressive strength and slump loss of M30 grade concrete with a 0.35 water-cement ratio. The optimal dosage is reported as the amount that produces the highest compressive strength after 7 and 28 days, and minimum slump loss. The results showed that polycarboxylic ether was most effective at dosages of 0.8% for compressive strength and 0.9% by cement weight for slump loss.
This document discusses the components, composition, and application of shotcrete used in NATM tunnel construction. It describes the requirements for shotcrete mixes, including low water permeability and minimum early strength. Early strength can be achieved through the use of spray bonding agents or alkali-free accelerating admixtures. Shotcrete is typically applied using either a dry-mix or wet-mix method. Wet-mix shotcrete is now preferred over dry-mix due to lower rebound, dust, and higher application rates. The document also discusses achieving different early strength classes and final strengths of 28-40MPa through the use of alkali-free additives.
Partial Replacement of Cement by Fly ash in Concrete Mix DesignIRJET Journal
This document discusses the partial replacement of cement with fly ash in concrete mix design. It begins with an abstract stating that concrete is an important construction material and that adding other materials can change its properties. The document then discusses how fly ash is a byproduct of coal combustion that can be used to partially substitute cement. When used in concrete, fly ash improves strength properties while requiring less energy to produce than ordinary Portland cement. The document provides details on fly ash classification, properties, advantages of using fly ash in concrete, and provides an example mix design showing the reduced quantities of cement, water and fine aggregate needed when partially substituting cement with fly ash.
This document summarizes a seminar on utilizing industrial waste in self-compacting concrete. It defines concrete and self-compacting concrete. Self-compacting concrete was developed in Japan in the 1980s to improve quality and flows under its own weight without vibration. The document discusses types of self-compacting concrete and advantages like improved filling and reduced labor. Tests to check suitability include slump flow, V-funnel, L-box, and U-box. Red mud and foundry sand were used to replace cement in mixtures and provided strength gains. Test results showed compressive strength up to 44 MPa and tensile strength up to 4.62 MPa with red mud additions of 2%. Foundry sand
IRJET- An Experimental Study on Air Entrained Mortar by Utilising Lather AgentIRJET Journal
This document presents research on producing an air-entrained mortar utilizing sugarcane ash and a lather agent. Mortar samples were produced with 10%, 30%, and 50% cement replaced by sugarcane ash. The samples were tested for compressive strength and water absorption at 7, 14, and 28 days. Results showed compressive strengths of 11.2 MPa, 8.5 MPa, and 7.3 MPa respectively for the 10%, 30%, and 50% sugarcane ash replacements compared to 12.5 MPa for a conventional mortar. Water absorption also increased with higher sugarcane ash content. The study concludes the mortar produced is beneficial due to lower cost and weight while being
Millet Husk Ash as Partial Replacement of Cement in Sandcrete BlockIRJET Journal
This document summarizes a study that investigated using millet husk ash (MHA) as a partial replacement for cement in sandcrete blocks. The study examined the physical and chemical properties of locally sourced MHA and found it met requirements to be considered a pozzolanic material. Sandcrete blocks were produced with 0%, 10%, 20%, 30%, and 40% replacements of cement with MHA. Testing found blocks with 10% and 20% replacements met minimum strength requirements while higher replacements reduced strength. The 20% replacement was determined to be optimal as it provided sufficient strength while reducing cement usage.
IRJET - Experimental Investigation on No-Fines Concrete with Tyre as a Partia...IRJET Journal
This document summarizes an experimental investigation on no-fines concrete with tire rubber as a partial replacement for coarse aggregate and sodium silicate as an admixture. No-fines concrete is a lightweight concrete that does not contain fine aggregates. The study aims to determine the optimum mix of no-fines concrete for partial replacement of coarse aggregate with tire rubber based on compressive, split tensile, and flexural strength testing. Various mix designs were tested where coarse aggregate was replaced by tire rubber at rates of 2.5%, 5%, and 7.5% by weight. The specimens were tested after 7, 14, and 28 days of curing and results were compared to conventional no-fines concrete. The results showed
Effect of Steel Fibre and Marble Dust on the Mechanical Properties of High St...IRJET Journal
This document discusses a study on the effect of adding steel fibers and marble dust to high-strength concrete. The researchers tested concrete mixtures with 0%, 15%, 30%, 45%, and 60% marble dust replacing sand and 0.8% steel fibers added. Based on the results, replacing up to 45% of the sand with marble dust and adding 0.8% steel fibers improved the compressive, flexural, and split tensile strengths of the concrete compared to the control mixture. Compressive strength and split tensile strength started decreasing when the marble dust replacement exceeded 15%. Therefore, the study concluded that replacing up to 45% marble dust and adding 0.8% steel fibers is an appropriate amount to improve mechanical properties of
I-sand: An Environmental Friendly Sand used in Reinforced Cement Concrete Con...IRJET Journal
This document discusses the use of iron sand (I-sand) as a partial replacement for river sand in reinforced cement concrete construction. It aims to provide an overview of research on utilizing iron sand to improve the performance of concrete while reducing the environmental impact of river sand extraction.
The key points discussed are:
1) River sand extraction has environmental concerns while demand is high, so alternative materials are needed. Iron sand is being researched as it can benefit construction and waste recycling.
2) Experimental concrete mixes were prepared with 0-30% river sand replaced by iron sand. Compressive strength generally increased with higher iron sand content, exceeding controls with over 10% replacement.
3) Workability decreased
Study of partial replacement of cement by barite powder and silica fume in se...IRJET Journal
The document studies the effect of partially replacing cement with barite powder and silica fume on the mechanical properties of self-compacting concrete. Specimens of M30 grade self-compacting concrete were prepared by replacing cement at 0%, 5%, 10%, 15%, 20%, and 25% levels with barite powder and silica fume added at one-fourth the barite powder level. The compressive strength and split tensile strength of the specimens were tested after 7 and 28 days of curing and compared with a control specimen. The results showed that compressive strength generally increased up to 15% replacement, beyond which it started decreasing, while split tensile strength followed a similar trend.
IRJET- Experimental Investigation on Partial Replacement of Fine Aggregate by...IRJET Journal
- The document experimentally investigates partially replacing fine aggregate with foundry sand in concrete mixtures.
- Tests were performed on concrete mixtures with 0-50% replacement of fine aggregate by foundry sand. Results showed compressive strength increased up to 30% replacement for M20 concrete and 40% replacement for M25 concrete.
- Higher replacements led to strength decreases. Therefore, foundry sand can partially replace fine aggregate in concrete, improving strength and providing an outlet for the waste foundry sand.
IRJET- Effect of Manufacturing Sand on Durability of ConcreteIRJET Journal
This document discusses a study on the effect of manufacturing sand on the durability of concrete. Concrete mixtures of M20 and M40 grade were produced by replacing natural sand with 0%, 50%, 70%, and 100% manufacturing sand. Various tests were performed to determine the hardened properties and durability of the concrete mixtures. The compressive strength of the concrete mixtures was tested at curing ages of 3, 7, and 28 days. The results showed that 100% replacement of natural sand with manufacturing sand increased the 28-day compressive strength of M20 grade concrete by over 30%. For M40 grade concrete, 50% replacement of natural sand with manufacturing sand increased the compressive strength at all ages compared to the control mixture. In
This document provides an overview of shotcrete technology. It defines shotcrete as cement, sand and fine aggregate concretes applied pneumatically under high velocity. Shotcrete can be classified as dry process or wet process based on how the materials are mixed and delivered. Some key advantages of shotcrete include its ability to form irregular surfaces and provide reinforcement. Shotcrete has various applications in construction, tunneling and retaining walls. It provides a strong, durable concrete material when applied correctly.
IRJET - Effect of Alccofine and Silica Fume on Strength Properties of ConcreteIRJET Journal
The document evaluates the effect of Alccofine and silica fume on the compressive strength, flexural strength, and split tensile strength of concrete. Concrete samples containing Alccofine or silica fume were tested at 3, 7, and 28 days to determine their strengths. The results showed that at 28 days, compressive strength increased by 16% with Alccofine compared to silica fume. Flexural strength increased by 11.11% with Alccofine, and split tensile strength increased by 33.93% with Alccofine compared to silica fume.
IRJET- Utilization of Rice Husk Ash and Foundry Sand as Partial Replaceme...IRJET Journal
The document summarizes a study on utilizing rice husk ash and foundry sand as partial replacements for cement and river sand in fiber reinforced concrete. Testing was conducted to determine the optimum fiber content and then evaluate how replacing cement with 5-20% rice husk ash and sand with 10-40% foundry sand impacted the compressive, split tensile, and flexural strengths of the concrete. The results showed that a mixture with 0.5% fibers and 10% rice husk ash and 20% foundry sand replacements achieved the highest strengths.
Study on flexural behaviour of Self compacting concrete using alccofineIRJET Journal
This document summarizes a study on the flexural behavior of self-compacting concrete using Alccofine, an ultrafine mineral admixture. Cement in self-compacting concrete mixes was partially replaced with 10% Alccofine. Beams made with the Alccofine mix showed similar load-deflection behavior and achieved failure loads comparable to control beams made with conventional self-compacting concrete. The results indicate that Alccofine can be effectively used to partially replace cement in self-compacting concrete with similar flexural performance.
Cold-in-place recycling with foamed asphalt (CIR-EAM) is a pavement rehabilitation technique where existing asphalt and base materials are recycled in place using foamed asphalt as a binding agent. Foamed asphalt is produced by injecting water and air into hot liquid asphalt, causing it to expand up to 20 times its original volume. The foamed asphalt is mixed with reclaimed asphalt and base materials to create a new stabilized base layer with high strength and durability. CIR-EAM can be used to rehabilitate 3-6 inches of an existing pavement and reduces costs, material waste, and CO2 emissions compared to conventional removal and replacement of asph
Experimental investigation on concrete by replacing crusher dust as fine aggr...eSAT Journals
Abstract In this present work we identified and investigated the use of crusher dust and granite floor slab chips in concrete as an alternative fine aggregate and coarse aggregate respectively, the tests were conducted on standard concrete cubes (150 mm x 150 mm x 150 mm), cylinders (150 mm x 300 mm) and prisms (100 mm x 100 mm x 500 mm). Tests on the physical properties of crusher dust, granite chips and its influence on the strength of fresh and hardened state, along with a comparative study with the concrete of river sand are made. The properties investigated were specific gravity, fineness modulus, water absorption, free surface moisture, bulk density and grading zone. Tests were conducted on 6 cubes, 6 cylinders and 6 prisms for M20 grade mix design with sand and crusher dust as fine aggregates, granite metal and granite floor slab chips as coarse aggregates. The strength parameters compressive strength, Split-Tensile strength and flexural strength were compared at 7 days and 28 days respectively. Mix design procedure in accordance with IS 10262-2009, IS 456-2000 and Sp 23-1982 using 20mm coarse aggregate was adopted for investigation. The investigation indicates that crushed stone dust has vast potential as fine aggregate in concrete construction. Crusher dust not only reduces the cost of construction but also helps reduce the impact on environment by consuming the material hitherto considered as a waste product with few applications. Keywords: Crusher Dust, Granite Floor Slab Chips, Concrete Mix.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document discusses a marketing solution involving Facebook message marketing. It will utilize Facebook mobile, desktop, and profile data as well as page, company and group information to target potential customers. The solution aims to engage customers through personalized messages.
This document describes Edition 3.1 of the Association of Geotechnical and Geoenvironmental Specialists' (AGS) format for the electronic transfer of geotechnical and geoenvironmental data. The AGS format was created to standardize the electronic transfer of subsurface investigation data between different software programs and users. This updated edition includes new groups, fields, pick lists, and determinand codes added based on user suggestions. It aims to incorporate commonly used additions to the format while maintaining compatibility with previous versions.
This document contains 17 references related to rock mechanics and rock engineering. The references span from 1931 to 1994 and include journal articles, conference proceedings, books, theses, and reports. The references cover topics such as rock mass classification systems, shear strength of rock joints, rockfall analysis, tunnel support, and case histories of rock engineering projects.
The document discusses blasting damage in rock excavations and methods to control it. It begins with a brief history of blasting and how the understanding of its effects on rock stability has lagged behind other areas of rock mechanics. Blasting can damage rock through dynamic stresses, gas pressure, and fracturing from the release of compressed rock. Precisely controlling blasting techniques from the initial cut through the full blast sequence is necessary to minimize damage extending several meters into the surrounding rock. Methods discussed include pre-splitting, smooth blasting, and the use of delays to allow broken rock to clear before subsequent holes detonate. Proper blasting design is crucial for ensuring the stability of underground excavations and rock slopes.
This document discusses design considerations for large underground caverns excavated in weak rock at depths of 100-300m below the surface for hydroelectric projects. It addresses the stability of caverns and surrounding rock mass given in situ stress conditions, effects of nearby slopes, and determining appropriate pillar sizes between excavations. The key design factors are the strength of the rock mass, influence of structural features like joints and bedding planes, sequence of excavation and support, and stress changes induced by nearby slopes and excavations. Pillar size between caverns must consider stresses imposed and stability of the rock mass.
The document discusses rock mass properties and the Hoek-Brown failure criterion for estimating the strength of jointed rock masses. It presents the generalized Hoek-Brown criterion equation and describes how to determine the intact rock properties of uniaxial compressive strength (σci) and the Hoek-Brown constant (mi) from triaxial test data or estimates. It also discusses estimating the Geological Strength Index (GSI) of the rock mass.
This document discusses rockfall hazards and analysis. It begins with an introduction noting that rockfalls are a major hazard for mountainous transportation routes and have resulted in numerous deaths. It then discusses the mechanics of rockfalls, noting that slope geometry and surface materials are most important in determining rockfall trajectories. Various measures to reduce rockfall hazards are discussed, including identification of problems, reducing energy from excavation, installing physical barriers like nets and ditches, and the Rockfall Hazard Rating System used to assess slopes.
The document introduces factor of safety and probability of failure in engineering design. It discusses using sensitivity studies to systematically vary parameters over their credible ranges to determine the influence on factor of safety. This allows a more rational assessment of design risks than relying on a single calculated factor of safety. The document then provides an introduction to probability theory and statistical concepts used in probabilistic analyses, including random variables, probability distributions, sampling techniques, and calculating the probability of failure for a slope design example.
The document describes a slope stability analysis of a steep rock slope in Hong Kong located near apartment buildings. Due to heavy rains causing landslides in the 1970s, the stability of this slope was analyzed. A simple limit equilibrium model was used to calculate the factor of safety under normal conditions and during earthquakes or heavy rains. The analysis found that instability could occur if the slope became fully saturated during an earthquake. However, as earthquakes and heavy rains are unlikely to occur simultaneously, it was concluded there was no serious short-term threat to stability. Evacuation of nearby apartments was deemed unnecessary based on this short-term stability assessment.
The Rio Grande project involves a 1000 MW pumped storage hydroelectric plant located in Argentina. It provides electrical storage for the local power grid. The main underground facilities are located within high quality gneiss rock. Support requirements were assessed during excavation and minimal support was needed due to the excellent rock quality. Rockbolts and shotcrete were used as needed based on geotechnical inspection. The UNWEDGE program was utilized to analyze wedge failures and determine support requirements.
The document discusses the shear strength of discontinuities in rock masses. It defines key terms like basic friction angle (φb), residual friction angle (φr), cohesion (c), and introduces Barton's method for estimating shear strength which accounts for joint roughness coefficient (JRC) and joint compressive strength (JCS). Small scale laboratory tests are used to determine φb, while JRC and JCS are estimated visually in the field. The shear strength of rough surfaces is higher than smooth surfaces due to surface asperities. Shear strength decreases if discontinuities are filled with soft materials like clay.
This document discusses when a rock engineering design can be considered acceptable. It notes that there are no universal rules and that each design is unique based on the site conditions, loads, and intended use. Acceptability is based on engineering judgment guided by analyses and studies. Tables provide examples of typical problems, parameters, analysis methods, and acceptability criteria for different rock structures. Case histories are also discussed to illustrate the factors considered and criteria used to determine acceptability, including ensuring stability and reducing deformation. One case examines slope drainage works to improve stability of landslides in a reservoir area. Another evaluates deformation control for a power tunnel by locating a replacement in a zone of small movements.
1. The development of rock engineering began in the late 18th century, but it was not established as a formal discipline until the 1960s after several catastrophic dam failures that demonstrated limitations in predicting rock mass behavior.
2. Early contributors to rock mechanics came from various fields like soil mechanics, mining, and geology. They made important contributions to understanding rock failure even if they did not consider themselves "rock mechanics engineers".
3. Major events like dam failures and mine collapses in the 1950s and 1960s highlighted the need for rock mechanics as a discipline and led to rapid advances in methods for designing rock structures and underground excavations.
This document provides guidance on ensuring geotechnical slope stability for post-mining landforms. It discusses designing stable slopes for landforms such as low wall spoil, out-of-pit dumps, and final void batters. It emphasizes the importance of geotechnical investigations and slope design to prevent issues like lost production, safety risks, and remediation costs. Data collection should consider factors like foundation strength, slope stability, and drainage for dumped materials.
This document summarizes three articles related to previous topics in Geotechnical Instrumentation News (GIN). The first article discusses distributed optical fiber sensing, which allows continuous strain measurement along an optical fiber cable. This is useful for geotechnical applications where soil loading is non-uniform. The second article compares different technologies for strain monitoring, including distributed optical fiber sensing. The third article provides examples of using distributed optical fiber sensing to monitor strain in pile foundations and detect cracks.
This study aimed to map forest fire risk zones in Quang Ninh province, Vietnam using remote sensing and GIS. Forest fire data from MODIS and field surveys were compared to validate the analysis. Factors like forest type, proximity to roads and settlements, slope, and aspect were used as inputs to a weighted overlay analysis. This generated a risk map classifying the area into very low to very high risk zones. Most fire locations fell within high or very high risk areas, validating the model. Improving input data resolution and incorporating additional social and weather factors could enhance future analyses. The study effectively mapped forest fire risk to aid decision-making for forest management in Quang Ninh province.
1. 15
Shotcrete support
15.1 Introduction
The use of shotcrete for the support of underground excavations was pioneered by the
civil engineering industry. Reviews of the development of shotcrete technology have
been presented by Rose (1985), Morgan (1992) and Franzén (1992). Rabcewicz
(1969) was largely responsible for the introduction of the use of shotcrete for tunnel
support in the 1930s, and for the development of the New Austrian Tunnelling
Method for excavating in weak ground.
In recent years the mining industry has become a major user of shotcrete for
underground support. It can be expected to make its own contributions to this field as
it has in other areas of underground support. The simultaneous working of multiple
headings, difficulty of access and unusual loading conditions are some of the
problems which are peculiar to underground mining and which require new and
innovative applications of shotcrete technology.
An important area of shotcrete application in underground mining is in the support of
'permanent' openings such as ramps, haulages, shaft stations and crusher chambers.
Rehabilitation of conventional rockbolt and mesh support can be very disruptive and
expensive. Increasing numbers of these excavations are being shotcreted immediately
after excavation. The incorporation of steel fibre reinforcement into the shotcrete is
an important factor in this escalating use, since it minimises the labour intensive
process of mesh installation.
Recent trials and observations suggest that shotcrete can provide effective support in
mild rockburst conditions (McCreath and Kaiser, 1992, Langille and Burtney, 1992).
While the results from these studies are still too limited to permit definite conclusions
to be drawn, the indications are encouraging enough that more serious attention will
probably be paid to this application in the future.
15.2 Shotcrete technology
Shotcrete is the generic name for cement, sand and fine aggregate concretes which are
applied pneumatically and compacted dynamically under high velocity.
15.2.1 Dry mix shotcrete
As illustrated in Figure 15.1, the dry shotcrete components, which may be slightly
pre-dampened to reduce dust, are fed into a hopper with continuous agitation.
Compressed air is introduced through a rotating barrel or feed bowl to convey the
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3. Shotcrete technology 277
materials in a continuous stream through the delivery hose. Water is added to the mix
at the nozzle. Gunite, a proprietary name for dry-sprayed mortar used in the early
1900's, has fallen into disuse in favour of the more general term shotcrete.
pre-dampened shotcrete mix
compressed air
water injection
compressed air
Figure 15.1: Simplified sketch of a typical dry mix shotcrete system.
After Mahar et al (1975).
Vacuum helps to restore pumping air and accelerator
tube to normal shape
air pipe
rotating rollers
rubber nozzle tip
wet mix shotcrete
roller rotating blades
suction
pumping tube
Figure 15.2: One typical type of wet mix shotcrete machine. After Mahar et
al (1975).
15.2.2 Wet mix shotcrete
In this case the shotcrete components and the water are mixed (usually in a truck
mounted mixer) before delivery into a positive displacement pumping unit, which
then delivers the mix hydraulically to the nozzle where air is added to project the
material onto the rock surface.
4. 278 Chapter 15: Shotcrete support
The final product of either the dry or wet shotcrete process is very similar. The dry
mix system tends to be more widely used in mining, because of inaccessibility for
large transit mix trucks and because it generally uses smaller and more compact
equipment. This can be moved around relatively easily in an underground mine
environment. The wet mix system is ideal for high production applications in mining
and civil engineering, where a deep shaft or long tunnel is being driven and where
access allows the application equipment and delivery trucks to operate on a more or
less continuous basis. Decisions to use the dry or wet mix shotcrete process are
usually made on a site-by-site basis.
15.2.3 Steel fibre reinforced micro silica shotcrete
Of the many developments in shotcrete technology in recent years, two of the most
significant were the introduction of silica fume, used as a cementitious admixture, and
steel fibre reinforcement.
Silica fume or micro silica is a by-product of the ferro silicon metal industry and is an
extremely fine pozzolan. Pozzolans are cementitious materials which react with the
calcium hydroxide produced during cement hydration. Silica fume, added in
quantities of 8 to 13% by weight of cement, can allow shotcrete to achieve
compressive strengths which are double or triple the value of plain shotcrete mixes.
The result is an extremely strong, impermeable and durable shotcrete. Other benefits
include reduced rebound, improved flexural strength, improved bond with the rock
mass and the ability to place layers of up to 200 mm thick in a single pass because of
the shotcrete's 'stickiness'. However, when using wet mix shotcrete, this stickiness
decreases the workability of the material and superplaticizers are required to restore
this workability.
Steel fibre reinforced shotcrete was introduced in the 1970s and has since gained
world-wide acceptance as a replacement for traditional wire mesh reinforced plain
shotcrete. The main role that reinforcement plays in shotcrete is to impart ductility to
an otherwise brittle material. As pointed out earlier, rock support is only called upon
to carry significant loads once the rock surrounding an underground excavation
deforms. This means that unevenly distributed non-elastic deformations of significant
magnitude may overload and lead to failure of the support system, unless that system
has sufficient ductility to accommodate these deformations.
Typical steel fibre reinforced, silica fume shotcrete mix designs are summarised in
Table 15.1. These mixes can be used as a starting point when embarking on a
shotcrete programme, but it may be necessary to seek expert assistance to 'fine tune'
the mix designs to suit site specific requirements. For many dry mix applications it
may be advantageous to purchase pre-mixed shotcrete in bags of up to 1,500 kg
capacity, as illustrated in Figure 15.3.
Figure 15.4 shows the steel fibre types which are currently available on the north
American market. In addition to their use in shotcrete, these fibres are also widely
used in concrete floor slabs for buildings, in airport runways and in similar concrete
applications.
Wood et al (1993) have reported the results of a comprehensive comparative study in
which all of the fibres shown in Figure 15.4 were used to reinforce shotcrete samples,
which were then subjected to a range of tests. Plain and fibre reinforced silica fume
5. Shotcrete technology 279
shotcrete samples were prepared by shooting onto vertical panels, using both wet and
dry mix processes. The fibre reinforced samples all contained the same steel fibre
dosage of 60 kg/m3 (see Table 15.1). All the samples were cured under controlled
relative humidity conditions and all were tested seven days after shooting.
Table 15.1: Typical steel fibre reinforced silica fume shotcrete mix designs (After Wood, 1992)
Components Dry mix Wet mix
kg./m3 % dry kg./m3 % wet
materials materials
Cement 420 19.0 420 18.1
Silica fume additive 50 2.2 40 1.7
Blended aggregate 1,670 75.5 1,600 68.9
Steel fibres 60 2.7 60 2.6
Accelerator 13 0.6 13 0.6
Superplasticizer - - 6 litres 0.3
Water reducer - - 2 litres 0.1
Air entraining admixture - - if required
Water controlled at nozzle 180 7.7
Total 2,213 100 2,321 100
Figure 15.3: Bagged pre-mixed
dry shotcrete components being
delivered into a hopper feeding a
screw conveyor, fitted with a pre-
dampener, which discharges into
the hopper of a shotcrete machine
6. 280 Chapter 15: Shotcrete support
28 mm
d=0.5
0.45
25 mm
0.53
0.50
32.5 mm
1.35
0.50
32.5 mm
2.75
0.25
25.5 mm
.1.12
Figure 15.4. Steel fibre types available on the north American market. After
Wood et al (1993). (Note: all dimensions are in mm).
These tests showed that the addition of steel fibres to silica fume shotcrete enhances
both the compressive and flexural strength of the hardened shotcrete by up to 20%. A
significant increase in ductility was also obtained in all the tests on fibre reinforced
samples, compared with plain samples. While different fibres gave different degrees
of improvement, all of the fibres tested were found to exceed the levels of
performance commonly specified in north America (i.e. 7-day compressive strength
of 30 MPa for dry mix, 25 MPa for wet mix and 7-day flexural strength of 4 MPa).
Kompen (1989) carried out bending tests on slabs of unreinforced shotcrete and
shotcrete reinforced with ‘Dramix’1 steel fibres, shown in Figure 15.5. The shotcrete
had an unconfined compressive strength, determined from tests on cubes, of 50 MPa.
The results of these tests are reproduced in Figure 15.6. The peak strength of these
slabs increased by approximately 85% and 185% for 1.0 and 1.5 volume % of fibres,
respectively. The ductility of the fibre reinforced slabs increased by approximately 20
and 30 times for the 1.0 and 1.5 volume % of fibres, respectively.
Figure 15.5: ‘Dramix’ steel fibres used in slab
bending tests by Kompen (1989). The fibres are
glued together in bundles with a water soluble
glue to facilitate handling and homogeneous
distribution of the fibres in the shotcrete.
1
Manufactured by N.V. Bekaert S.A., B-8550 Zwevegem, Belgium.
7. Shotcrete technology 281
Figure 15.6: Load deflection curves for unreinforced and steel fibre reinforced shotcrete
slabs tested in bending. After Kompen (1989).
15.2.4 Mesh reinforced shotcrete
While steel fibre reinforced shotcrete has been widely accepted in both civil and
mining engineering, mesh reinforced shotcrete is still widely used and is preferred in
some applications. In very poor quality, loose rock masses, where adhesion of the
shotcrete to the rock surface is poor, the mesh provides a significant amount of
reinforcement, even without shotcrete. Therefore, when stabilising slopes in very
poor quality rock masses or when building bulkheads for underground fill, weldmesh
is frequently used to stabilise the surface or to provide reinforcement. In such cases,
plain shotcrete is applied later to provide additional support and to protect the mesh
against corrosion.
Kirsten (1992, 1993) carried out a comprehensive set of laboratory bending tests
on both mesh and fibre reinforced shotcrete slabs. The load versus deflection curves,
that he obtained, were similar to those reported by Kompen, reproduced in Figure
15.6. He found that the load carrying capacity of the mesh and fibre reinforced
shotcrete samples were not significantly different, but that the mesh reinforced
samples were superior in bending with both point loads and uniformly distributed
loads. He concluded that this was due to the more favourable location of the mesh
reinforcement in the slabs subjected to bending.
Kirsten also concluded that the quality control, required to obtain a consistent
dosage and uniform distribution of fibres in shotcrete, is more easily achieved in civil
engineering than in mining applications. This is a reflection of the multiple working
headings and the difficulties of access that are common problems associated with
many mines. Under these circumstances, more reliable reinforcement will be obtained
with mesh reinforced rather than fibre reinforced shotcrete. However, in large mines,
in which many of the ‘permanent’ openings are similar to those on large civil
engineering sites, these problems of quality control should not arise.
8. 282 Chapter 15: Shotcrete support
Chainlink mesh, used in many underground mining excavations to support loose
rock, is not usually suitable for shotcrete reinforcement. This is because penetration
of the shotcrete is inhibited by the twisted joints as illustrated in Figure 15.7. This
allows air cavities to form behind the mesh and these may allow water to enter and
cause corrosion of the mesh.
On the other hand, weldmesh, tightly pinned against the rock face as illuatrated in
Figure 15.8, is generally ideal for shotcrete applications. Typically the weldmesh
should be made from 4 mm diameter wire welded into a 100 mm x 100 mm grid. This
type of mesh is strong enough for most underground applications and the sheets are
light enough to he handled by one man.
Figure 15.7: Chainlink mesh, while
very strong and flexible, is not ideal
for shotcrete application because it is
difficult for the shotcrete to penetrate
the mesh.
Figure 15.8: Welded wire mesh,
firmly attached to the rock surface,
provides excellent reinforcement
for shotcrete.
9. Shotcrete applications 283
15.3 Shotcrete applications
The quality of the final shotcrete product is closely related to the application
procedures used. These procedures include: surface preparation, nozzling technique,
lighting, ventilation, communications, and crew training.
Shotcrete should not be applied directly to a dry, dusty or frozen rock surface. The
work area is usually sprayed with an air-water jet to remove loose rock and dust from
the surface to be shot. The damp rock will create a good surface on which to bond the
initial layer of shotcrete paste. The nozzleman commonly starts low on the wall and
moves the nozzle in small circles working his way up towards the back, or roof. Care
must be taken to avoid applying fresh materials on top of rebound or oversprayed
shotcrete. It is essential that the air supply is consistent and has sufficient capacity to
ensure the delivery of a steady stream of high velocity shotcrete to the rock face.
Shooting distances are ideally about 1 to 1.5 metres. Holding the nozzle further from
the rock face will result in a lower velocity flow of materials which leads to poor
compaction and a higher proportion of rebound.
A well-trained operator can produce excellent quality shotcrete manually, when
the work area is well-lit and well-ventilated, and when the crew members are in good
communication with each other using prescribed hand signals or voice activated FM
radio headsets. However, this is a very tiring and uncomfortable job, especially for
overhead shooting, and compact robotic systems are increasingly being used to permit
the operator to control the nozzle remotely. Typical robotic spray booms, used for
shotcrete application in underground excavations, are illustrated in Figures 15.9,
15.10 and 15.11.
Figure 15.9: A truck mounted shotcrete robot being used in a large civil engineering tunnel.
Note that the distance between the nozzle and the rock surface is approximately one metre.
10. 284 Chapter 15: Shotcrete support
Figure 15.10: Compact trailer-mounted robot unit for remote controlled
shotcrete application.
Figure 15.11: Shotcrete operator using a remotely
controlled unit to apply shotcrete to a rock face in a
large civil engineering excavation.
11. Design of shotcrete support 285
Figure 15.12: Plastic pipes used to provide drainage for a
shotcrete layer applied to a rock mass with water-bearing
joints.
When shotcrete is applied to rock masses with well-defined water-bearing joints, it is
important to provide drainage through the shotcrete layer in order to relieve high
water pressures. Drain holes, fitted with plastic pipes as illustrated in Figure 15.12,
are commonly used for this purpose. Where the water inflow is not restricted to a few
specific features, a porous fibre mat can be attached to the rock surface before the
shotcrete layer is applied. When practical to do so, the water from these drains should
be collected and directed into a drainage ditch or sump.
15.4 Design of shotcrete support
The design of shotcrete support for underground excavations is a very imprecise
process. However, one observation, which is commonly made by practical engineers
with years of experience in using shotcrete underground, is that it almost always
performs better than anticipated. There are many examples (very few of which are
documented) where shotcrete has been used as a last act of desperation in an effort to
stabilise the failing rock around a tunnel and, to most people's surprise, it has worked.
The complex interaction between the failing rock mass around an underground
opening, and a layer of shotcrete of varying thickness with properties which change
as it hardens, defies most attempts at theoretical analysis. It is only in recent years,
12. 286 Chapter 15: Shotcrete support
with the development of powerful numerical tools, that it has been possible to
contemplate realistic analyses, which will explore the possible support-interaction
behaviour of shotcrete. A clear understanding of shotcrete behaviour will require
many more years of experience in the use of and in the interpretation of the results
obtained from these programs. It is also important to recognise that shotcrete is very
seldom used alone and its use in combination with rockbolts, cablebolts, lattice
girders or steel sets further complicates the problem of analysing its contribution to
support.
Current shotcrete support 'design' methodology relies very heavily upon rules of
thumb and precedent experience. Wickham et al (1972) related the thickness of a
shotcrete tunnel lining to their Rock Structure Rating (RSR). Bieniawski (1989) gave
recommendations on shotcrete thicknesses (in conjunction with rockbolts or steel
sets) for different Rock Mass Ratings (RMR) for a 10 m span opening. Grimstad and
Barton (1993) have published an updated relating different support systems, including
shotcrete and fibre reinforced shotcrete, to the Tunnelling Quality Index Q.
Vandewalle (1990) collected various rules of thumb from a variety of sources and
included them in his monograph.
Table 15.2 is a compilation of current shotcrete practice by the present author,
combining all of these empirical rules and adding in my own practical experience.
The reader is warned, that this table can only be used as an approximate guide when
deciding upon the type and thickness of shotcrete to be applied in a specific
application. Modifications will almost certainly be required to deal with local
variations in rock conditions and shotcrete quality.
Table 15.2: Summary of recommended shotcrete applications in underground mining, for
different rock mass conditions.
Rock mass Rock mass Support Shotcrete application
description behaviour requirements
Massive No spalling, None. None.
metamorphic or slabbing or failure.
igneous rock .
Low stress
conditions.
Massive Surfaces of some Sealing surface to Apply 25 mm thickness of plain
sedimentary rock. shales, siltstones, or prevent slaking. shotcrete to permanent surfaces as
Low stress claystones may soon as possible after excavation.
conditions. slake as a result of Repair shotcrete damage due to
moisture content blasting.
change.
Massive rock with Fault gouge may be Provision of support Remove weak material to a depth
single wide fault or weak and erodible and surface sealing in equal to width of fault or shear zone
shear zone. and may cause vicinity of weak fault and grout rebar into adjacent sound
stability problems in of shear zone. rock. Weldmesh can be used if
adjacent jointed required to provide temporary rockfall
rock. support. Fill void with plain shotcrete.
Extend steel fibre reinforced shotcrete
laterally for at least width of gouge
zone.
13. Design of shotcrete support 287
Massive Surface slabbing, Retention of broken Apply 50 mm shotcrete over weldmesh
metamorphic or spalling and rock and control of anchored behind bolt faceplates, or
igneous rock. possible rockburst rock mass dilation. apply 50 mm of steel fibre reinforced
High stress damage. shotcrete on rock and install rockbolts
conditions. with faceplates; then apply second 25
mm shotcrete layer.
Extend shotcrete application down
sidewalls where required.
Massive Surface slabbing, Retention of broken Apply 75 mm layer of fibre reinforced
sedimentary rock. spalling and rock and control of shotcrete directly on clean rock.
High stress possible squeezing squeezing. Rockbolts or dowels are also needed
conditions. in shales and soft for additional support.
rocks.
Metamorphic or Potential for wedges Provision of support Apply 50 mm of steel fibre reinforced
igneous rock with a or blocks to fall or in addition to that shotcrete to rock surfaces on which
few widely spaced slide due to gravity available from joint traces are exposed.
joints. loading. rockbolts or cables.
Low stress
conditions.
Sedimentary rock Potential for wedges Provision of support Apply 50 mm of steel fibre reinforced
with a few widely or blocks to fall or in addition to that shotcrete on rock surface on which
spaced bedding slide due to gravity available from discontinuity traces are exposed, with
planes and joints. loading. rockbolts or cables. particular attention to bedding plane
Low stress Bedding plane Sealing of weak traces.
conditions. exposures may bedding plane
deteriorate in time. exposures.
Jointed Combined structural Retention of broken Apply 75 mm plain shotcrete over
metamorphic or and stress controlled rock and control of weldmesh anchored behind bolt
igneous rock. failures around rock mass dilation. faceplates or apply 75 mm of steel
High stress opening boundary. fibre reinforced shotcrete on rock,
conditions. install rockbolts with faceplates and
then apply second 25 mm shotcrete
layer
Thicker shotcrete layers may be
required at high stress concentrations.
Bedded and jointed Slabbing, spalling Control of rock mass Apply 75 mm of steel fibre reinforced
weak sedimentary and possibly failure and shotcrete to clean rock surfaces as soon
rock. squeezing. squeezing. as possible, install rockbolts, with
High stress faceplates, through shotcrete, apply
conditions. second 75 mm shotcrete layer.
Highly jointed Ravelling of small Prevention of Apply 50 mm of steel fibre reinforced
metamorphic or wedges and blocks progressive ravelling. shotcrete on clean rock surface in roof
igneous rock. defined by of excavation.
Low stress intersecting joints. Rockbolts or dowels may be needed
conditions. for additional support for large blocks.
Highly jointed and Bed separation in Control of bed Rockbolts or dowels required to
bedded sedimentary wide span separation and control bed separation.
rock. excavations and ravelling. Apply 75 mm of fibre reinforced
Low stress ravelling of bedding shotcrete to bedding plane traces
conditions. traces in inclined before bolting.
faces.
Heavily jointed Squeezing and Control of rock mass Apply 100 mm of steel fibre reinforced
igneous or 'plastic' flow of rock failure and dilation. shotcrete as soon as possible and
metamorphic rock, mass around install rockbolts, with face-plates,
conglomerates or opening. through shotcrete. Apply additional 50
cemented rockfill. mm of shotcrete if required. Extend
High stress support down sidewalls if necessary.
conditions.
14. 288 Chapter 15: Shotcrete support
Heavily jointed Squeezing and Control of rock mass Apply 50 mm of steel fibre reinforced
sedimentary rock 'plastic' flow of rock failure and dilation. shotcrete as soon as possible, install
with clay coated mass around lattice girders or light steel sets, with
surfaces. opening. Clay rich invert struts where required, then more
High stress rocks may swell. steel fibre reinforced shotcrete to cover
conditions. sets or girders. Forepoling or spiling
may be required to stabilise face ahead
of excavation. Gaps may be left in
final shotcrete to allow for movement
resulting from squeezing or swelling.
Gap should be closed once opening is
stable.
Mild rockburst Spalling, slabbing Retention of broken Apply 50 to 100 mm of shotcrete over
conditions in and mild rockbursts. rock and control of mesh or cable lacing which is firmly
massive rock failure propagation. attached to the rock surface by means
subjected to high of yielding rockbolts or cablebolts.
stress conditions.