This document summarizes a study on using photocatalytic paving blocks containing titanium dioxide to remove nitrous oxide from the air. The blocks were made with recycled materials like glass cullet and furnace bottom ash. Factors studied included the porosity of blocks, types of waste materials used, and percentages of different types of titanium dioxide added. The results showed that blocks with higher porosity and those containing recycled glass had greater nitrous oxide removal abilities. Three types of titanium dioxide powders were also tested and their effects on removal quantified. An optimum mix design was selected based on the results.
IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) is an open access international journal that provides rapid publication (within a month) of articles in all areas of mechanical and civil engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in mechanical and civil engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) is an open access international journal that provides rapid publication (within a month) of articles in all areas of mechanical and civil engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in mechanical and civil engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Experimental investigation on studying the flexural behaviour of geopolymer c...eSAT Journals
Abstract
Geo polymer concrete is one of the emerging construction material as a substitute for conventional cement concrete, eliminating
the usage of OPC. This work is aimed to cast and testing of geopolymer slab elements with restrained edge condition. The size of
slab panel is 1m x 1m x 0.05 m. By using yield line theory, the moment of resistance and maximum deflection under flexural
loading are calculated for the of GPC slabs. Reinforcement details of these slabs are calculated using ultimate load method as
per IS code provisions. As the slab element is a composite material the experimental work is carried for determination of
mechanical properties GPC matrix and casting and testing of slab elements under UDL. Test results are compared with the
theoretical computations for bending moment and maximum deflections. The crack pattern of slabs in experimental work is also
compared with yield line patterns ( Developed for RCC).From the test results it is observed that the behaviour of GPC slabs
under flexural loading is similar to conventional concrete slabs
KeyWords: Geo Polymer Concrete, Slabs, Flexural Behavior, Yield Line Patterns , Load vs Deflections
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
An experimental investigation on properties of ggbs based geopolymer concrete...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Influence of Micro additives on Macrostructure of Autoclavedaerated Concreteinventionjournals
Autoclaved aerated concrete (AAC) is a construction material with porous macrostructure prepared of finely milled siliceous aggregate, lime, water and Portland cement with the addition of aluminium powder and being steam-cured under the pressure in an autoclave. Today AAC (light construction material) is a widely used in the constructions as a material that is compared to concrete or conventional stone material, which has a high insulation properties and fireresistant. Previous studies have shown that application of microadditives in AAC enhances physical-mechanical properties of AAC samples. Most of these changes are duo to an even distribution of pores. The influence of such additives, as amorphous SiO2 (AS) and carbon fibres (CF), reduced to microsizeparticles, on formation of AAC macrostructure was investigated. The investigations were carried out with AAC forming mixture where 10% lime was replaced by equivalent content of Portland cement. Research results have showed, that the optimal replacement of sand by AS was 1.0% and by CF – 0.1%, and resulted in an equal distribution of pores and optimal macrostructure formation (higher amount of small pores, lower amount of merged pores) which leads to highest compressive and flexural strengths of modified AAC samples
STRENGTH PROPERTIES ON FLY ASH BASED GEO POLYMER CONCRETE WITH ADMIXTURESIAEME Publication
Due to increase in environmental problems of the construction industry alternative technologies are emerging. A concrete is used around the world is second only to water. The making of ordinary Portland cement support 5 to 7 percent of total green house gas emission. It also takes large amount of energy .Hence it is necessary to find alternative to cement .Fly ash is a product of coal procured from thermal power plant. It is also good in silicon and alumina. In this experiment the fly ash is used to prepare the geo polymer concrete.geopolymer is a material resulting from the reaction of source materials that is rich in aluminum and silicon. One such material is GEOPOLYMER CONCRETE. It uses a material like fly ash as binding material in place of cement.
Study on Characteristics of Geopolymer Concrete with E-WasteIOSRJMCE
The usage of industrial by-products in construction industry can be reduced the pollution effects on environment. Geopolymer concrete is a concrete in which Portland cement is fully replaced by fly ash and GGBS (Ground granulated blast furnace slag). The present study covers the use of E-Waste as partial replacement of fine aggregate in Geopolymer concrete. Sand is replaced with E-Waste at 10, 20 and 30 percentage.Alkaline liquids used in this study are the solutions of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Molarity of sodium hydroxide (12M) is considered. Fly ash and GGBS were used in the combination of 90 and 10 percent respectively. This study conducted to know the compressive and tensile strengths of Geopolymer concrete with E-waste and to compare the same with Geopolymer concrete. It has been revealed that 20 percentage replacement with E-Waste attained higher strength than the normal Geopolymer concrete of M40 grade
Synthesis of geopolymer from indonesian kaolin and fly ash as a green constru...Pambudi Pajar Pratama
The cement industry is a substantial contributor to the global greenhouse gases emissions, accounting for approximatley 6% of the total global CO2 emission. Geopolymer, an inorganic polymer consisting primarily of Si-Al-O covalent chains, is an attractive alternative to the conventional portland cement due to its much smaller carbon footprint. This research is an early work aimed at elucidating the techno-economic feasibility of geopolymer production in Indonesia, utilizing domestic aluminosilicate minerals and waste materials as feedstocks. Kaolin from the Belitung island and Class F coal fly ash from an electric powerplant in East Java were selected as the geopolymer precursors. The kaolin was initially calcined at 750 oC for 6 hours to convert it to the much more reactive metakaolin phase. Besides the type of aluminosilicate raw materials, the type of alkali solution was also varied between NaOH and KOH. The aluminosilicate materials were each reacted with 10.0 M alkali hydroxide solution at a solid-to-liquid mass ratio of 1.2 and 2.8 for the case of metakaolin and fly ash, respectively. The effect of these variables was evaluated on mortars prepared by using the obtained geopolymers, which involved the measurement of settling time in accordance to an Indonesian standard Vicat apparatus method, and compressive strength according to the ASTM C 109-80 method. The setting time of fly ash - KOH/NaOH geopolymer mortars is shorter than those obtained using metakaolin, due to the higher reactivity of the amorphous fly ash. The higher reactivity of fly ash also promotes better crosslinking of the Si-Al-O bonds, resulting in a higher compressive strength compared to the metakaolin-based geopolymer samples.
Experimental investigation on studying the flexural behaviour of geopolymer c...eSAT Journals
Abstract
Geo polymer concrete is one of the emerging construction material as a substitute for conventional cement concrete, eliminating
the usage of OPC. This work is aimed to cast and testing of geopolymer slab elements with restrained edge condition. The size of
slab panel is 1m x 1m x 0.05 m. By using yield line theory, the moment of resistance and maximum deflection under flexural
loading are calculated for the of GPC slabs. Reinforcement details of these slabs are calculated using ultimate load method as
per IS code provisions. As the slab element is a composite material the experimental work is carried for determination of
mechanical properties GPC matrix and casting and testing of slab elements under UDL. Test results are compared with the
theoretical computations for bending moment and maximum deflections. The crack pattern of slabs in experimental work is also
compared with yield line patterns ( Developed for RCC).From the test results it is observed that the behaviour of GPC slabs
under flexural loading is similar to conventional concrete slabs
KeyWords: Geo Polymer Concrete, Slabs, Flexural Behavior, Yield Line Patterns , Load vs Deflections
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
An experimental investigation on properties of ggbs based geopolymer concrete...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Influence of Micro additives on Macrostructure of Autoclavedaerated Concreteinventionjournals
Autoclaved aerated concrete (AAC) is a construction material with porous macrostructure prepared of finely milled siliceous aggregate, lime, water and Portland cement with the addition of aluminium powder and being steam-cured under the pressure in an autoclave. Today AAC (light construction material) is a widely used in the constructions as a material that is compared to concrete or conventional stone material, which has a high insulation properties and fireresistant. Previous studies have shown that application of microadditives in AAC enhances physical-mechanical properties of AAC samples. Most of these changes are duo to an even distribution of pores. The influence of such additives, as amorphous SiO2 (AS) and carbon fibres (CF), reduced to microsizeparticles, on formation of AAC macrostructure was investigated. The investigations were carried out with AAC forming mixture where 10% lime was replaced by equivalent content of Portland cement. Research results have showed, that the optimal replacement of sand by AS was 1.0% and by CF – 0.1%, and resulted in an equal distribution of pores and optimal macrostructure formation (higher amount of small pores, lower amount of merged pores) which leads to highest compressive and flexural strengths of modified AAC samples
STRENGTH PROPERTIES ON FLY ASH BASED GEO POLYMER CONCRETE WITH ADMIXTURESIAEME Publication
Due to increase in environmental problems of the construction industry alternative technologies are emerging. A concrete is used around the world is second only to water. The making of ordinary Portland cement support 5 to 7 percent of total green house gas emission. It also takes large amount of energy .Hence it is necessary to find alternative to cement .Fly ash is a product of coal procured from thermal power plant. It is also good in silicon and alumina. In this experiment the fly ash is used to prepare the geo polymer concrete.geopolymer is a material resulting from the reaction of source materials that is rich in aluminum and silicon. One such material is GEOPOLYMER CONCRETE. It uses a material like fly ash as binding material in place of cement.
Study on Characteristics of Geopolymer Concrete with E-WasteIOSRJMCE
The usage of industrial by-products in construction industry can be reduced the pollution effects on environment. Geopolymer concrete is a concrete in which Portland cement is fully replaced by fly ash and GGBS (Ground granulated blast furnace slag). The present study covers the use of E-Waste as partial replacement of fine aggregate in Geopolymer concrete. Sand is replaced with E-Waste at 10, 20 and 30 percentage.Alkaline liquids used in this study are the solutions of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Molarity of sodium hydroxide (12M) is considered. Fly ash and GGBS were used in the combination of 90 and 10 percent respectively. This study conducted to know the compressive and tensile strengths of Geopolymer concrete with E-waste and to compare the same with Geopolymer concrete. It has been revealed that 20 percentage replacement with E-Waste attained higher strength than the normal Geopolymer concrete of M40 grade
Synthesis of geopolymer from indonesian kaolin and fly ash as a green constru...Pambudi Pajar Pratama
The cement industry is a substantial contributor to the global greenhouse gases emissions, accounting for approximatley 6% of the total global CO2 emission. Geopolymer, an inorganic polymer consisting primarily of Si-Al-O covalent chains, is an attractive alternative to the conventional portland cement due to its much smaller carbon footprint. This research is an early work aimed at elucidating the techno-economic feasibility of geopolymer production in Indonesia, utilizing domestic aluminosilicate minerals and waste materials as feedstocks. Kaolin from the Belitung island and Class F coal fly ash from an electric powerplant in East Java were selected as the geopolymer precursors. The kaolin was initially calcined at 750 oC for 6 hours to convert it to the much more reactive metakaolin phase. Besides the type of aluminosilicate raw materials, the type of alkali solution was also varied between NaOH and KOH. The aluminosilicate materials were each reacted with 10.0 M alkali hydroxide solution at a solid-to-liquid mass ratio of 1.2 and 2.8 for the case of metakaolin and fly ash, respectively. The effect of these variables was evaluated on mortars prepared by using the obtained geopolymers, which involved the measurement of settling time in accordance to an Indonesian standard Vicat apparatus method, and compressive strength according to the ASTM C 109-80 method. The setting time of fly ash - KOH/NaOH geopolymer mortars is shorter than those obtained using metakaolin, due to the higher reactivity of the amorphous fly ash. The higher reactivity of fly ash also promotes better crosslinking of the Si-Al-O bonds, resulting in a higher compressive strength compared to the metakaolin-based geopolymer samples.
A Documentation on Construction and Demolition wasteRohanDas52
Despite being an ancient activity, the management of waste produced in construction activities
did not get much attention until the last decade. Construction and demolition waste (CDW) is not
subjected to management practices as with municipal solid waste (MSW), perhaps due to the
higher toxicity of the latter as compared with the former. Recently, rapid urban expansion,
stringent environmental regulations, and the scarcity of land filling areas as well as the natural
resources over-exploitation led to the need of using CDW as aggregate for construction purposes.
CDW contains significant amounts of inert materials whose properties are being investigated and
which have been recognized for use as aggregate, although significant differences exist when
compared to conventional natural aggregates (NA). The use of recycled concrete waste-based
aggregates in new concrete is a way of maximizing the economic benefits of CDW and, even
though it has been the subject of study for a long time, opinions are still not consensual. As
expected, concrete made with recycled aggregates (RA) has different characteristics from those
of conventional concrete, and these differences are strongly dependent on the type and quality of
the aggregates used.
Experimental Study of using Pond Ash as Partial Replacement for Fine Aggregat...YogeshIJTSRD
Production of one ton of Portland cement emits one ton of CO2 and different greenhouse gases main to atmospheric pollution. Hence the want arises to exchange cement with some different cementitious material. Disposal of Pond ash which is combination of Fly ash andamp Bottom ash into massive lakes reasons land air pollution and different environmental effects. The cause of this find out about is to locate the suitability of silica fume as a alternative cloth for cement and pond ash as a alternative fabric for first rate combination in concrete except compromising the power andamp sturdiness of traditional concrete. The bodily and chemical property of silica fume and pond ash is to be studied and each the industrial wastes are used to substitute the cement and great aggregate. Pond ash is in part changed for fantastic mixture with the aid of various percentages 10 to 30 , additionally silica fume is introduced by way of 10 to 20 by way of the weight of cement. The specimens will be examined for its mechanical houses such as compressive strength, cut up tensile energy and flexural electricity on 7, 28 andamp 56 days. After identifying the houses of the concrete mixes, the foremost share of alternative tiers of silica fume and pond ash will be carried out and Reinforced Concrete Beams had been forged to decide the flexural behaviour for the optimized concrete Mix. Mr. K. Soundirarajan | Telem Shidartha "Experimental Study of using Pond Ash as Partial Replacement for Fine Aggregate in a Silica Fume Based Concrete" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-5 , August 2021, URL: https://www.ijtsrd.com/papers/ijtsrd45048.pdf Paper URL: https://www.ijtsrd.com/engineering/civil-engineering/45048/experimental-study-of-using-pond-ash-as-partial-replacement-for-fine-aggregate-in-a-silica-fume-based-concrete/mr-k-soundirarajan
Concrete is one of the reliable, durable, economical and acceptable construction materials among the building and construction stakeholders worldwide. Performance of concrete could be threatened especially reinforced concrete by some processes such as corrosion, sulfate attack among others. Corrosion of reinforcement in reinforced concrete can be induced by carbonation process. Even though carbonation initiates corrosion, it has been gathered that carbonation could still be of immense benefits to building and construction industries if its mechanism of operation is understudied. This research work has therefore investigated the effect of carbonation on some selected mechanical properties of concrete such as compressive strength, flexural strength, water absorption and weight changes. Concrete cubes and beams of M15 grade with 0.5 % water-cement ratio were prepared and subjected to accelerated carbonation. Their compressive strength, flexural strength, water absorption and weight changes were determined in accordance with the relevant standards. The outcomes show that carbonation improves all the mechanical properties investigated. The use of carbonation can be positively explored in reinforced concrete provided there is adequate nominal cover.
ASSESSING THE REDUCTION OF CARBON DIOXIDE EMISSIONS THROUGH APPLYING HIGH-STR...IAEME Publication
The construction industry accounts for approximately 23% of the national energy
consumption per year. Considering the production and transportation of construction
materials, the ratio of energy consumption increases up to 40 % in this industry.
Recently, several studies established effective strategies for reducing the carbon
dioxide emissions such as utilisation of low-carbon materials, material recycling,
minimisation of materials input, and selection of optimal structural systems. Along with
such approaches, there are various studies examined the application of high-strength
materials for minimum utilisation of construction materials. Despite this approach to
calculate CO2 emissions of structural materials, it is necessary to study the effectiveness
and relationships between the implementation of high-strength re-bars and normal rebars.
In order to fill this gap, this study examines the reduction of reinforcement bars
and CO2 emissions by the implementation of high-strength re-bars in a practical
approach. In this study, an office complex building was selected to assess the quantity
variation over the normal re-bars. The office complex building is a rigid-frame
structure which has 25 storeys above the ground level and one storey in the
underground. Based on the analysed data, this study concluded that the application of
SD500 and SD600 high-strength re-bars would lead the quantity reduction of about
25% and 50% respectively compared to the structural system designed with SD400.
Generally, applications to high-strength materials, especially high-strength re-bars in
the study is potentially beneficial in both reducing the input amount of materials and
carbon dioxide emissions in the rigid-frame structure.
NO removal efficiency of photocatalytic paving blocks prepared with recycled materials
1. Construction
and Building
Construction and Building Materials 21 (2007) 1746–1753
MATERIALS
www.elsevier.com/locate/conbuildmat
NO removal efficiency of photocatalytic paving blocks
prepared with recycled materials
C.S. Poon *, E. Cheung
Department of Civil and Structural Engineering, The Hong Kong, Polytechnic University, Hung Hom, Hong Kong
Received 30 August 2005; received in revised form 18 April 2006; accepted 30 May 2006
Available online 27 September 2006
Abstract
This paper presents the results of a study on the effectiveness of incorporating air cleaning agents such as titanium dioxide (TiO2) into
the technique of producing concrete paving blocks, using local waste materials to remove nitrous oxide (NO). Factors which would affect
the performance of the blocks were studied including the porosity of blocks, the type of waste materials used within the mix design, the
types and percentage of TiO2 added within the mix design.
The results show that the photodegradation of NO is related to the porosity of the blocks. When the porosity of the block was
increased so was the NO removal ability. Hence the choice, size and content of aggregate material used in the mix design are important.
In addition, crushed recycled glass cullet was used to place part of the aggregates in the blocks and was found to benefit the NO removal
ability due to its light transmitting characteristic. Three types of TiO2 were tested in this study and their influence on NO removal was
quantified. Based on the experimental results, an optimum mix design was selected which incorporates recycled glass, sand, cement and
TiO2.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Photocatalyst; Titanium dioxide; Nitrogen oxides; Recycled aggregates
1. Introduction lion people [3]. The numerous tall buildings, particularly
in the urban area, hinder and prevent the dispersion of
The construction industry is the major solid waste gen- air pollutants generated by a high concentration of vehicles
erator in Hong Kong [1]. The extensive building and infra- at the street level. It is apparent that there is a need to
structure development projects as well as redevelopment of remove pollutants, such as nitrogen oxides (NOX) and sul-
old districts have led to an increase in construction and phur dioxide (SO2) from the atmosphere. Not only do these
demolition waste (C&DW) generation in the last decade. gases pose a threat to health, they are also causing degra-
This has caused the disposal of the wastes to become a dation to many inner city buildings. Despite attempts to
severe social and environmental problem in the territory. lower these emissions by using cleaner vehicles, it appears
Up to present this problem has been dealt with by dispos- that a way of removing such pollutants once in the atmo-
ing the waste at landfills and public filling areas locally. sphere needs to be sought.
There is an increasing interest to explore new ways to Photocatalysis, such as titanium dioxide, have already
recycle aggregates derived from C&D waste [2]. been tested in Japan for concrete paving materials that
Additionally, Hong Kong also faces a growing concern can facilitate a photocatalytic reaction converting the more
of air pollution due to having to provide habitats and toxic forms of air pollutants to less toxic forms (e.g. NOX
transportation for a high population density of seven mil- to HNO3) [4–7]. Under the illumination of ultraviolet light,
photocatalysis shows diverse functions, such as the decom-
*
Corresponding author. Tel.: +852 2766 6024; fax: +852 2334 6389. position of air and water contaminants and deodorization,
E-mail address: cecspoon@polyu.edu.hk (C.S. Poon). as well as self cleaning, antifogging, and antibacterial
0950-0618/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.conbuildmat.2006.05.018
2. C.S. Poon, E. Cheung / Construction and Building Materials 21 (2007) 1746–1753 1747
two other types of TiO2 were sourced from an industrial
source in Mainland China due to their low prices compared
to P25. The two types of TiO2 included one in the form of
anatase crystal structure and the other in the rutile crystal
structure. The two types of TiO2 are referenced as anatase
and rutile respectively in this paper. The properties of the
TiO2 powders used are shown in Figs. 2 and 3, and Table
1.
Fig. 2 shows that the particle size decreased in the order
Fig. 1. The design of the photocatalytic paving block. of P-25, followed by the rutile form and then the anatase
form. Fig. 3 show that P25 possessed TiO2 in the forms
of anatase and rutile. Whereas the anatase form of TiO2
actions [8–11]. Practical applications of photocatalysts contained only the anatase form and the rutile form of
have rapidly expanded in recent years. Photocatalytic TiO2 contained only the rutile form.
materials for outdoor purification are in urgent demand Furnace bottom ash (FBA) used is a by-product of coal-
because energy and labour saving advantages have been fired electricity generation. FBA is the coarser material that
realized when applied to building or road construction falls to the bottom of the furnace during the burning of
materials in large cities where urban air pollution is very coal. Chemically, it is very similar to pulverized fly ash
serious [11]. but due to its coarse grain size, it is not commonly used
Based on the current environmental problems the main in cement and concrete applications [14,15]. In Hong
objective of this study is to analyze the effectiveness of Kong, the produced FBA is currently dumped at an ash
incorporating air cleaning agents such as TiO2 into the lagoon as waste. FBA used in this study was obtained from
technique of producing concrete paving blocks using local the Castle Peak Power Station and sieved in the laboratory.
waste materials. The paving block consists of a concrete Only the portion that passed through a 2.36 mm sieve was
base layer made from cement and recycled aggregates, used for making the surface layer.
and a thin surface layer made of cement, various aggregate
materials and a small amount of titanium dioxide. The
design of this photocatalytic block is shown in Fig. 1. In 16
this paper, the focus is on optimizing the surface layer P25 Rutile Anatase
14
design of the block. To achieve this, surface layers were
produced using different material combinations, and tested 12
Distribution (%)
for their NO removal abilities. The followings were studied: 10
8
Compare natural aggregates with recycled aggregates
and decide which benefits the pollutant removal ability 6
of the paving blocks. 4
Study the factors affecting the NO photodegradation of 2
the blocks. These include porosity, cement content, dif-
0
ferent particle size of aggregates and curing time of the
.84
.69
4
.68
05
15
23
35
53
81
23
86
83
52
91
3
80
.0
4.
blocks.
0.
0.
0.
0.
1.
1.
2.
9.
0.
0.
6.
22
34
15
52
Particle diameter (micrometre)
Compare different sources of TiO2 and their effects
towards pollutant removal ability. Fig. 2. Particle size distribution of TiO2 powders.
Anatase Rutile P25
2. Experimental details A
R R
R A A A A R A
2.1. Materials R R
Intensity (a.u.)
The cementitious material used in this study was an
Ordinary Portland Cement (OPC) commercially available
in Hong Kong, complying with BS 12 [12] and ASTM Type
I [13].
Three sources of titanium dioxide (TiO2) were used. The
first was P-25 sourced from Degussa, which was used due
to its high purity and accurate specifications. It is com- 10 20 30 40 50 60 70 80 90 100
2 theta (degree)
monly used in the industry and research community, hence
would be useful for comparison with works of others. The Fig. 3. XRD spectrum of TiO2 powders (A: anatase, R: rutile).
3. 1748 C.S. Poon, E. Cheung / Construction and Building Materials 21 (2007) 1746–1753
Table 1 Table 3
Properties of TiO2 Mixes prepared with RA, FBA and sand
Properties P25 Anatase Rutile Mix notation Relative proportions (by weight)
Moisture (%) 1.5 0.04 0.46 Cement RA Sand FBA P25 TiO2 Water
Water solubility (%) – 0.05 0.03
R1:2 1 2 – – 0.06 0.28
Ignition loss (%) 2.0 0.01 0.17 R1:2.5 1 2.5 – – 0.07 0.30
pH 3.0–4.0 7.5 6.7
R1:3 1 3 – – 0.08 0.32
Oil adsorption (g/g) – 22/100 23/100
R*1:2 1 2 – – 0.06 0.28
Color eliminating capacity (per min) – 100 100
R*1:2.5 1 2.5 – – 0.07 0.30
Sieve residue, Mocker 45 (%) 0.05 0.05 0.05
R*1:3 1 3 – – 0.08 0.32
TiO2 (%) 99.5 98.5 91
S1:2 1 – 2 – 0.06 0.24
S1:2.5 1 – 2.5 – 0.07 0.26
S1:3 1 – 3 – 0.08 0.28
The recycled aggregate (RA) used in this study was a S*1:2 1 – 2 – 0.06 0.24
crushed CD waste sourced from a temporary recycling S*1:2.5 1 – 2.5 – 0.07 0.26
facility in Hong Kong. In the plant the CD waste under- S*1:3 1 – 3 – 0.08 0.28
RF1:2 1 1.5 – 0.50 0.06 0.32
went a process of mechanized sorting, crushing and sieving RF1:2.5 1 1.88 – 0.63 0.07 0.34
to produce both fine and coarse aggregates according to RF1:3 1 2.25 – 0.75 0.08 0.36
the particle size requirements of BS 812 [16]. Only the smal- RF*1:2 1 1.5 – 0.50 0.06 0.32
ler fine aggregate proportion was used for making the sur- RF*1:2.5 1 1.88 – 0.63 0.07 0.34
face layer of the blocks in this study. The maximum size of RF*1:3 1 2.25 – 0.75 0.08 0.36
SF1:2 1 – 1.5 0.50 0.06 0.28
the recycled fine aggregate used was 2.36 mm. The proper- SF1:2.5 1 – 1.88 0.63 0.07 0.30
ties of the RA are shown in Table 2. SF1:3 1 – 2.25 0.75 0.08 0.32
The recycled glass (RG) used in this study was mainly SF*1:2 1 – 1.5 0.50 0.06 0.28
post-consumer beverage bottles sourced locally. The glass SF*1:2.5 1 – 1.88 0.63 0.07 0.30
bottles were washed and crushed by mechanical equipment. SF*1:3 1 – 2.25 0.75 0.08 0.32
The RG was sieved in the laboratory to pass though the
2.36 mm sieve. The properties of the RG are shown in
Table 2.
Table 4
The sand used was fine natural river sand commercially Mixes prepared with recycled glass
available in Hong Kong. The properties of sand are shown
Mix notation Relative proportions (by weight)
in Table 2.
Cement RG Sand P25 TiO2 Water
2.2. Mix proportions GS100 1 3 – 0.08 0.28
GS75 1 2.25 0.75 0.08 0.28
GS50 1 1.5 1.5 0.08 0.28
2.2.1. Mixes prepared with RA, FBA and sand GS25 1 0.75 2.25 0.08 0.28
This study focused on utilizing recycled materials, so a GS0 1 – 3 0.08 0.28
series of mixes (as shown in Table 3) were prepared to find
out the effects of different materials and proportions on NO
removal efficiency. Mixes with different cement to aggre-
gate ratios, ranging from 1:2, 1:2.5 and 1:3 were prepared. 2.2.3. Mixes prepared with varying amount and types of
Most of the mixes were prepared using aggregate sizes from TiO2
0 to 2.36 mm. But selected mixes (those identified by ‘*’) The effects of varying the amount and types TiO2 were
were prepared with aggregate sizes only between 300 and studied by preparing specimens with the TiO2 (P-25) con-
2.36 mm with the À300 lm portion removed. tent ranging from 0% to 10% at 2% intervals (Table 5)
and different sources of TiO2 (Table 6).
2.2.2. Mixes prepared with RG
The light transmitting characteristic of glass was
thought to benefit NO photodegradation when used in
Table 5
the mix design of the surface layers. Hence mix proportions Mixes prepared with varying TiO2 content
prepared with recycled glass were designed (Table 4).
Mix notation (%) Relative proportions (by weight)
Cement Glass Sand P25 TiO2 Water
Table 2 0 1 1.5 1.5 0 0.26
Properties of RA, RG and sand 2 1 1.5 1.5 0.08 0.28
4 1 1.5 1.5 0.16 0.36
RA (fine) RG Sand
6 1 1.5 1.5 0.24 0.40
Density (kg/m3) 2093 2531 2651 8 1 1.5 1.5 0.32 0.48
Water absorption (%) 10.28 0 0.87 10 1 1.5 1.5 0.40 0.64
4. C.S. Poon, E. Cheung / Construction and Building Materials 21 (2007) 1746–1753 1749
Table 6
Mixes prepared with different sources of TiO2
Mix notation Relative proportions (by weight)
Cement Glass Sand P-25 TiO2 Anatase TiO2 Rutile TiO2 Water
P-25 1 1.5 1.5 0.08 – – 0.26
Anatase 1 1.5 1.5 – 0.08 – 0.26
Rutile 1 1.5 1.5 – – 0.08 0.26
2.3. Sample preparation the specimen, which is expressed as the approximate indica-
tion of the porosity of the specimens.
Surface layers for the different mix designs were pre-
pared to test for their ability to remove NO. The surface 2.5. Test of photodegradation of NO
layers were fabricated in steel moulds with internal dimen-
sions of 200 · 100 · 5 mm. The wet mixed materials 2.5.1. Equipment
weighed between 220 and 280 g for each surface layer The testing equipment used was a self-designed flow
depending on the different materials. The steel moulds were reactor adapted from an existing design [17], but with alter-
over filled by hand compaction, and then further com- ations. The reactor provides a physical boundary to enable
pressed using a compression machine at a rate of a photocatalytic material, in our case a photocatalytic sur-
600 KN/min twice, first to 500 KN and secondly to face layer of a paving block, to be examined for its pollu-
600 KN. After 1 day, the surface layers were removed from tant removal capability. The dimensions of the chamber
their moulds and cured in a chamber with a controlled reactor were 700 mm in length, 400 mm in width and
humidity of 75% and temperature of 25 °C until testing. 130 mm in height. The reactor consists of a sampling inlet
The surface layers were tested for NO photodegradation and outlet. Two 10 W UV-A fluorescent lamps (black
at 28, 56 and 90 days. lights), which emit primary UV light wavelengths at
365 nm were used to provide photoirradiation to activate
2.4. Determination of physical properties the photocatalyst. The intensity was measured using a
UV meter (Spectroline DRC-100X) to be 10 W mÀ2 at
2.4.1. Porosity the centre of the reactor which was also where the test sam-
The method requires the specimens to be crushed into ples were placed. The light source was positioned outside
approximately 10 mm diameter sizes and then oven dried the reactor and the distance from the reactor was adjusted
at 105 °C for 24 h. Hundred grams of the prepared speci- till the required intensity was achieved. The design enables
mens were soaked in acetone in a sealed container for the reactor to be used as a continuous flow reactor or a
24 h. The specimens were then removed from the acetone batch flow reactor. The reactor needed to be constructed
and the specimen surfaces were dried by an acetone wetted with materials of low adsorption ability and resistance to
tissue paper. The weights of the specimens were then ultraviolet irradiation, hence stainless steel was used. Rub-
weighed and the difference between the original weights ber was used as sealant for the reactor. The lid of the reac-
indicated the amount of acetone that can be absorbed by tor was designed using transparent glass rimmed with
Light source
2 x 10 W UV-A lamps
(Intensity = 10 Wm-2 at centre of sample surface)
Standard gas
(NO)
with flow
controller
Reactor
NO analyzer Computer
Humidity = 10 %
Zero air with
flow
controller
Fig. 4. Schematic diagram of the experimental setup.
5. 1750 C.S. Poon, E. Cheung / Construction and Building Materials 21 (2007) 1746–1753
stainless steel. A temperature sensor, humidity sensor, fan due to the porous nature of RA compared to that of sand.
(for circulation), and adjustable rack to support the speci- The results also indicate that the NO removal slightly
mens were placed inside the reactor. Fig. 4 further illus- increased when FBA was included in the mix design. This
trates the equipment setup described. is believed to be due to the higher porosity of FBA particles
which was exemplified by its relatively low specific density
2.5.2. Testing procedure compared to those of sand and RA.
The reactor was connected to a supply of standard gas
(NO) and a zero air generator (Thermo Environmental 3.1.2. Effect of cement/aggregate ratio on NO
Inc. Model 111). The standard gas was obtained from a photodegradation
compressed gas cylinder with nitrogen as the balanced With different cement to aggregate ratios, the results
gas (NIST certified). A humidity of 10% was achieved for (Fig. 6) show that the NO removal increased when the
the reactor by passing the reactant stream and the zero cement content decreased. An increase in NO removal of
air stream directly through the reactor. It is possible to approximately 30% was experienced for specimens when
achieve a higher humidity by passing the zero air stream the cement to aggregate ratio dropped from 1:2 to 1:3.
through a water bath, but in the procedure the humidity The increase in NO removal due to the change in cement
was kept at 10% as at this humidity level observation pat- content was a result of the fine particle size of cement
terns can be more easily interpreted. Also for comparison grains and hydrated cement particles could easily fill up
purposes this is believed to be reasonable. The gas streams the voids within the specimens, the surface area available
were then adjusted by the flow controllers to achieve an ini- for pollutants was reduced. Although reducing the cement
tial NO concentration of 1000 ppb and a flowrate of content was favourable towards NO removal, the adopted
6 L minÀ1, these testing conditions in a similar set-up have cement content of the surface layers should also consider
also been used by Yu [18] and are believed to be the most the necessary mechanical strength required for paving
ideal from trial. After the inlet and the outlet NO concen- applications. Preliminary studies showed that a minimum
trations reached equilibrium (1/2 h), the UV lamps were cement to aggregate ratio of 1:3 should be used in the sur-
turned on to begin the removal process (1 h). The NO con- face layer [19].
centration was continuously measured by the NO analyzer
(Thermo Environmental Instruments Inc. Model 42c). To 3.1.3. Effect of curing age on NO photodegradation
complete the experimental procedure the lamps were then All specimens prepared were tested at the curing ages of
turned off and the supply gas changed to zero air only 28, 56 and 90 days to investigate the influence of curing age
(1/2 h). on the NO removal. The results displayed in Fig. 7 only
show some of the selected mixes, all with a cement to aggre-
3. Results and discussion gate ratio of 1:3. The results show that NO removal
decreased with increasing age from 28 to 90 days by
3.1. Factors affecting the NO photodegradation approximately 8%. This drop was a result of the reduction
in the number of active sites due to the closing up of pores
3.1.1. Effect of aggregate material on NO photodegradation as a result of the continuous hydration and carbonization
The results of NO photodegradation as shown in Fig. 5 of the hydrated cement particles. Lackhoff et al. [20] inves-
indicate that the RA mixes achieved a much higher NO tigated the possibility of using photocatalyst modified
removal compared to the sand mixes. This is probably cement samples for the degradation of pollutants and they
3
3
S* SF* R* RF*
2.5 2.8
NO removal (mg hr m )
NO removal (mghr -1m-2)
-2
2.6
-1
2
2.4
1.5 2.2
2
1
1.8
0.5
1.6
0 1.4
S* 1:3 R* 1:3 SF* 1:3 RF* 1:3 1:2 1:2.5 1:3
Mixes Cement to aggregate ratio
Fig. 5. Comparison of different materials to remove NO at 90 days Fig. 6. A comparison of NO removal for mixes prepared with different
testing. cement contents at 90 days testing (Table 3).
6. C.S. Poon, E. Cheung / Construction and Building Materials 21 (2007) 1746–1753 1751
3.4 2.8
3.2
NO removal (mghr m )
2.7
-2
NO removal (mghr m )
-2
3
-1
-1
2.6
2.8
2.5
2.6
2.4 2.4
2.2
2.3
2
28 56 90
2.2
Days 7 8 9 10 11 12 13
R1:3 R*1:3 S1:3 S*1:3 RF1:3 RF*1:3 SF1:3 SF*1:3 Acetone absorbed per 100g of dry specimen
Fig. 7. NO removal of specimens tested at different curing ages (Table 2). Fig. 9. Comparison of NO removal and porosity for selected mixes.
also demonstrated that photocatalytic activity decreased
during the ageing of the hardened cement pastes. 3.2. Effect of incorporating recycled crushed glass cullet
3.1.4. Effect of particle size of aggregates on NO The results as shown in Fig. 10 indicate that when recy-
photodegradation cled glass was used as aggregates the NO removal ability
The specimens prepared with different aggregate sizes was enhanced. This is believed to be related to the high
was believed to affect their ability to remove NO as altering light transmitting characteristic of the recycled glass parti-
the particle size distribution of aggregates would effectively cles. Light could be carried to a greater depth activating the
change the porosity of the specimens. The specimens were TiO2 on the surface as well as within the surface layer. This
divided into to two groups, one was prepared with all was also supported by Murata et al. [6] when they utilized
aggregate sizes below 2.36 mm included and the other with glass beads in the design of photocatalytical paving blocks.
aggregate sizes only between 300 lm and 2.36 mm The results in Fig. 11 also show quite clearly that NO
included. Fig. 8 shows the specimens tested at 90 days with removal increased with increasing amounts of recycled
a cement to aggregate ratio of 1:3. The results indicate that glass. As alkali aggregate reaction has been recognized as
the specimens prepared with aggregate sizes between a limiting factor in using crushed glass in concrete mixes,
300 lm and 2.36 mm (the more porous specimens) a replacement level of 50% of sand by recycled glass was
achieved approximately 4% higher NO removal. chosen as the optimal mix based on our separate study.
3.1.5. Effect of porosity on NO photodegradation 3.3. Effect of different contents and sources of TiO2
The factors affecting the NO removal discussed above
were all associated with porosity. Fig. 9 shows the mea- The results as shown in Fig. 12 indicate that there was a
sured porosity compared with NO removal of some of significant increase in NO removal with an increase in TiO2
the selected mixes. An obvious trend can be observed content. At 90 days, NO removal increased from
showing NO removal increased with increase in porosity. 2.56 mg hÀ1 mÀ2 for specimens with 2% TiO2 to
3.5
SF
3
NO removal (mghr-1m-2 )
2.5
RF
2
1.5
S
1
R 0.5
0
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
GS100 (Glass) R1:3 (RA) S1:3 (Sand) RF1:3 (RA+FBA) SF1:3 (S+FBA)
-1 -2
NO removal (mghr m ) Mix notation
2.36mm 300-2.36um
Fig. 10. Effect of recycled glass in the mix towards NO photodegradation
Fig. 8. NO removal of specimens with different aggregate sizes (Table 3). when compared to other materials at 90 days curing age (Table 3 and 4).
7. 1752 C.S. Poon, E. Cheung / Construction and Building Materials 21 (2007) 1746–1753
3.5 3.5
3.3
3
NO removal (mghr-1m-2 )
NO removal (mghr m )
3.1
-2
2.5
-1
2.9
2.7 2
2.5
1.5
2.3
2.1 1
1.9 0.5
1.7
0
1.5 28 56 90
0 25 50 75 100 Days
Days
P25 Rutile Anatase
Fig. 11. NO removal of mixes with different recycled glass contents at
Fig. 13. NO removal of specimens containing different sources of TiO2
90 days curing age.
(Table 6).
4.5 [22]. In addition, Deng et al. [23] showed that the activities
4 28 56 90 Days of pure anatase TiO2 and pure rutile TiO2 catalysts with
almost the same surface area for photocatalytic oxidation
NO removal (mg hr m )
-2
3.5
of hexane were similar.
-1
3
The TiO2 powder Degussa P-25 consists of both the ana-
2.5 tase and rutile forms at a ratio of 70:30. P-25 has often been
2 considered as one of the best and most frequently used
1.5 TiO2 photocatalysts. Ohno et al. [24] explained the excel-
1
lent ability of P-25 was due to a synergy effect as a result
of the anatase and rutile particles in contact. It was sug-
0.5
gested that anatase and rutile TiO2 particles exist sepa-
0
0% 2% 4% 6% 8% 10%
rately by forming agglomerates in P-25. Therefore
TiO2 (% of whole weight) electron transfer was feasible via the agglomerates which
lead to the high activity of P-25.
Fig. 12. The effect of NO removal at different TiO2 contents (Table 6). There are a wide range of factors which could possibly
affect the activity of TiO2 used in this study. These included
4.01 mg hÀ1 mÀ2 for specimens with 10% TiO2. The corre- the crystalline forms, surface area, particle size, porosity,
sponding increase was 57%. Although NO removal surface acidity and density of surface adsorbed water and
increases as the TiO2 content increases up to 10% by weight hydroxyl groups [25]. It seems that the larger P-25 TiO2
of the whole mix, the effectiveness of the use of higher TiO2 particles were more beneficial to the photocatalytic activity
content on the NO removal needs to be verified by future in the current study. Small TiO2 particles have often been
studies. believed to benefit photoactivity due to the increased sur-
Three types of commercially available TiO2 powders face area. The apparent contrary results might be attrib-
were compared. Specimens of the same mix design were uted to the presence of other small sized materials such
produced in which the only variable was the source of as the cement in the production of the surface layers which
TiO2 (Table 6). The results as shown in Fig. 13 indicate covered the TiO2 particles. Further research is required to
that, at all test ages, P-25 showed the best removal ability, conclude this finding.
followed by the rutile form of TiO2 and the anatase form of
TiO2. Indeed, the NO removal for P-25 and the rutile form 4. Conclusion
of TiO2 was very close. At 90 days, the NO removal of P-25
was higher by only 8% compared to the removal of the This paper reports on the findings on assessing the fac-
rutile form. On the other hand the NO removal for the ana- tors which would affect the ability of the prepared surface
tase form of TiO2 was 53% lower compared to that of P-25. layer of the paving blocks to remove NO by photocatalytic
The rutile form of TiO2 performed better photocatalyt- activities. The results indicate that porosity of the surface
ically when used in the mix design compared to the anatase layer is important which effectively increased the area avail-
form despite the anatase form is generally believed to be able to reacting with the pollutants. The porosity of the
more photoactive [21]. But it has also been reported in a surface layer was affected by the type of materials with
previous study that the rutile form can perform more which they were prepared. Materials with a lower density
actively or as well as the anatase form in certain situation. led to a higher porosity of the blocks. The particle size
8. C.S. Poon, E. Cheung / Construction and Building Materials 21 (2007) 1746–1753 1753
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[10] Fujushima A, Hashimoto K, Watanabe T. TiO2 photocatalysis
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Acknowledgement environmental protection department of HKSAR E183413. Hong
Kong. 2003.
[19] Poon CS, Cheung E. Air pollutant removing paving blocks produced
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