Dielectric permittivity is a promising technique for making non-destructive measurements of the setting and hydration behavior of cementitious systems. In this paper, preliminary work has been done to investigate the link between the dielectric permittivity behavior of a series of mortars of varying W/C and the setting and hydration behavior in the same mortars as observed using isothermal calorimetry and penetration resistance measurements. The dielectric permittivity of these mortars measured at a frequency of 2.45 GHz appears to be sensitive to the chemical changes experienced during setting. Regions in the dielectric behavior have been tentatively linked to the dormant period of cement hydration, the initial time of set and the peaks in isothermal calorimetry associated with C3S reaction and monosulphoaluminate formation. Dielectric permittivity also shows promise in determining the moisture content of portland cement-based systems.
{"title":"Monitoring Setting and Early Hydration of Cement Using Dielectric Spectroscopy","authors":"S. Ng, G. Shapiro, S. Mak","doi":"10.14359/10578","DOIUrl":"https://doi.org/10.14359/10578","url":null,"abstract":"Dielectric permittivity is a promising technique for making non-destructive measurements of the setting and hydration behavior of cementitious systems. In this paper, preliminary work has been done to investigate the link between the dielectric permittivity behavior of a series of mortars of varying W/C and the setting and hydration behavior in the same mortars as observed using isothermal calorimetry and penetration resistance measurements. The dielectric permittivity of these mortars measured at a frequency of 2.45 GHz appears to be sensitive to the chemical changes experienced during setting. Regions in the dielectric behavior have been tentatively linked to the dormant period of cement hydration, the initial time of set and the peaks in isothermal calorimetry associated with C3S reaction and monosulphoaluminate formation. Dielectric permittivity also shows promise in determining the moisture content of portland cement-based systems.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123944491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The speed of curing is often a critical issue in the manufacture of precast concrete elements. For some products, the curing cycle consumes up to 70% of the total production cycle. To improve the speed of production, heat curing is often used to accelerate the hardening of precast concrete. Conventional heating techniques rely on thermal conduction. Microwave energy offers potential to increase the rate of bulk heating in precast concrete through its relatively deeper penetration, which allows quicker through-depth heating and maturing. Research on microwave curing of concrete has been ad hoc in the past and a wide range of issues remain unresolved. These encompass materials-microwave interactions, process design and control, hardware and logistics as well as the impact of microwave curing on concrete properties. In this paper, progress on research on microwave curing is described with reference to work carried out at CSIRO. In particular, results from pilot-scale heating of slab-type elements are discussed in relation to heating characteristics, process control, set acceleration, strength development and process efficiency. The authors' results show that for the same bulk heating rates, microwave heating produces significantly lower temperature gradients when compared to steam heating. Using rapid curing cycles of less than six hours, compressive strengths in excess of 25 MPa can be achieved in high quality precast concrete. Doubling the bulk heating rate using microwaves does not result in any deterioration in near-surface quality as was the case with conventional steam heating.
{"title":"Rapid Microwave Curing of Precast Concrete Slab Elements","authors":"S. Mak, D. Ritchie, G. Shapiro, R. W. Banks","doi":"10.14359/10600","DOIUrl":"https://doi.org/10.14359/10600","url":null,"abstract":"The speed of curing is often a critical issue in the manufacture of precast concrete elements. For some products, the curing cycle consumes up to 70% of the total production cycle. To improve the speed of production, heat curing is often used to accelerate the hardening of precast concrete. Conventional heating techniques rely on thermal conduction. Microwave energy offers potential to increase the rate of bulk heating in precast concrete through its relatively deeper penetration, which allows quicker through-depth heating and maturing. Research on microwave curing of concrete has been ad hoc in the past and a wide range of issues remain unresolved. These encompass materials-microwave interactions, process design and control, hardware and logistics as well as the impact of microwave curing on concrete properties. In this paper, progress on research on microwave curing is described with reference to work carried out at CSIRO. In particular, results from pilot-scale heating of slab-type elements are discussed in relation to heating characteristics, process control, set acceleration, strength development and process efficiency. The authors' results show that for the same bulk heating rates, microwave heating produces significantly lower temperature gradients when compared to steam heating. Using rapid curing cycles of less than six hours, compressive strengths in excess of 25 MPa can be achieved in high quality precast concrete. Doubling the bulk heating rate using microwaves does not result in any deterioration in near-surface quality as was the case with conventional steam heating.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124999619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Maeda, I. Wada, M. Kawakami, T. Ueda, G. Pushpalal
Effect of rice husk ash addition on the chloride diffusivity of concrete is investigated in the present paper. The concrete specimens, having water-cementitious materials ratio of 0.30, 0.36 and 0.53, with and without rice husk ash are subjected to accelerated chloride penetration using the following two methods: i) Immersion in saturated NaCl at 20 degrees C, ii) Exposure to alternate cycles of 3 days immersion in 3% NaCl solution at 20 degrees C and 4 days drying at 50% R.H. After the accelerated chloride penetration, the total chloride content of concrete specimens at various depths was determined. Consequently, using the chloride content distributions, the chloride diffusion coefficient of concrete is evaluated by applying Fick's second law. In addition, the pore size distribution of concrete is determined in order to assess the effect of concrete microstructure on chloride diffusivity. From the experimental results, the total chloride content of concrete incorporating rice husk ash was shown to be lower than that of the control concrete after accelerated chloride penetration. The concrete specimens incorporating rice husk ash had chloride diffusion coefficients 57% to 25% lower than the control concrete. The effect of rice husk ash on pore refinement in concrete was observed, especially in the pore radii larger than 50nm. The pore size distribution of concrete tended to shift towards the smaller pores with the addition of rice husk ash. The decrease of the chloride diffusion coefficient of concrete incorporating RHA may therefore be attributed to the pore-refinement effect.
{"title":"Chloride Diffusivity of Concrete Incorporating Rice Husk Ash","authors":"N. Maeda, I. Wada, M. Kawakami, T. Ueda, G. Pushpalal","doi":"10.14359/10585","DOIUrl":"https://doi.org/10.14359/10585","url":null,"abstract":"Effect of rice husk ash addition on the chloride diffusivity of concrete is investigated in the present paper. The concrete specimens, having water-cementitious materials ratio of 0.30, 0.36 and 0.53, with and without rice husk ash are subjected to accelerated chloride penetration using the following two methods: i) Immersion in saturated NaCl at 20 degrees C, ii) Exposure to alternate cycles of 3 days immersion in 3% NaCl solution at 20 degrees C and 4 days drying at 50% R.H. After the accelerated chloride penetration, the total chloride content of concrete specimens at various depths was determined. Consequently, using the chloride content distributions, the chloride diffusion coefficient of concrete is evaluated by applying Fick's second law. In addition, the pore size distribution of concrete is determined in order to assess the effect of concrete microstructure on chloride diffusivity. From the experimental results, the total chloride content of concrete incorporating rice husk ash was shown to be lower than that of the control concrete after accelerated chloride penetration. The concrete specimens incorporating rice husk ash had chloride diffusion coefficients 57% to 25% lower than the control concrete. The effect of rice husk ash on pore refinement in concrete was observed, especially in the pore radii larger than 50nm. The pore size distribution of concrete tended to shift towards the smaller pores with the addition of rice husk ash. The decrease of the chloride diffusion coefficient of concrete incorporating RHA may therefore be attributed to the pore-refinement effect.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129608465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work was conducted to develop two types of controlled low strength materials (CLSM) or flowable slurry utilizing post-consumer glass (broken glass or glass cullet) aggregate and fly ash. Type A CLSM consisted of glass, fly ash, cement, and water; and Type B CLSM consisted of glass, sand, cement, and water. All mixtures were proportioned to achieve the 28-day compressive strength of 0.7 MPa (100 psi). The type A CLSM mixtures consisted of a control mixture (100% fly ash without glass) and five other mixtures with glass, as a replacement of fly ash in the range of 20% to 80%. The Type B CLSM mixtures were composed of a control mixture (without glass) and two other mixtures at 30% to 75% replacement of sand with glass. The flowable slurry developed in this project satisfied the ACI Committee 229 definition of CLSM. Decreasing the amount of fly ash and increasing the glass content led to increased bleeding and segregation at high replacement levels of 60% and 80%. Permeability of Type A CLSM remained essentially unchanged, except at high glass contents it was lower. For Type B CLSM, the permeability was about the same.
{"title":"Use of Glass and Fly Ash in Manufacture of Controlled low Strength Materials","authors":"T. Naik, R. N. Kraus, Shiw S. Singh","doi":"10.14359/10588","DOIUrl":"https://doi.org/10.14359/10588","url":null,"abstract":"This work was conducted to develop two types of controlled low strength materials (CLSM) or flowable slurry utilizing post-consumer glass (broken glass or glass cullet) aggregate and fly ash. Type A CLSM consisted of glass, fly ash, cement, and water; and Type B CLSM consisted of glass, sand, cement, and water. All mixtures were proportioned to achieve the 28-day compressive strength of 0.7 MPa (100 psi). The type A CLSM mixtures consisted of a control mixture (100% fly ash without glass) and five other mixtures with glass, as a replacement of fly ash in the range of 20% to 80%. The Type B CLSM mixtures were composed of a control mixture (without glass) and two other mixtures at 30% to 75% replacement of sand with glass. The flowable slurry developed in this project satisfied the ACI Committee 229 definition of CLSM. Decreasing the amount of fly ash and increasing the glass content led to increased bleeding and segregation at high replacement levels of 60% and 80%. Permeability of Type A CLSM remained essentially unchanged, except at high glass contents it was lower. For Type B CLSM, the permeability was about the same.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"42 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126214337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents the test results on the study of reinforced concrete (R/C) columns strengthened with carbon fiber sheets (CFS). The purpose of this research was the evaluation of the CFS confinement characteristics of square reinforced concrete columns. The test specimens consisted of seventeen square columns (200x200mm cross-section and 400mm height). The test columns were fabricated with different lateral reinforcement ratios. The tests were performed with different CFS reinforcement ratios and reinforcing methods to investigate the effects on the strength and deformation characteristics of concrete columns. Test results were characterized according to failure patterns, maximum loads, and strain distribution along the column longitudinal axes.
{"title":"Axial Compressive Behavior of Reinforced Concrete Short Columns Strengthened with Carbon Fiber Sheets","authors":"J. Hwang, K. S. Lee, B. Bahn, S. Shin","doi":"10.14359/10595","DOIUrl":"https://doi.org/10.14359/10595","url":null,"abstract":"This paper presents the test results on the study of reinforced concrete (R/C) columns strengthened with carbon fiber sheets (CFS). The purpose of this research was the evaluation of the CFS confinement characteristics of square reinforced concrete columns. The test specimens consisted of seventeen square columns (200x200mm cross-section and 400mm height). The test columns were fabricated with different lateral reinforcement ratios. The tests were performed with different CFS reinforcement ratios and reinforcing methods to investigate the effects on the strength and deformation characteristics of concrete columns. Test results were characterized according to failure patterns, maximum loads, and strain distribution along the column longitudinal axes.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125889734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes a five-year Electric Power Research Institute (EPRI) program directed toward increasing ash utilization in the cement and concrete market within the United States, in the face of the impacts on ash quality due to more aggressive NOx controls. EPRI is undertaking this program to provide the technical basis for protecting the bulk sale of coal ash in high-volume applications in cement and concrete and other high volume civil engineering applications. In addition to higher carbon levels in ash from NOx control systems, problems associated with ammoniated ash have become a major concern for coal-fired facilities in recent years as a result of the increased use of ammonia-based environmental control technologies. Many coal-fired power producers have become concerned that post-combustion NOx controls could lead to fly ash containing high levels of ammonia. Therefore, EPRI conducted a research program designed to assist power producers to evaluate and mitigate the impacts of high carbon and ammoniated ash.
{"title":"The U.S. Power Industry’s Activities to Expand Coal Ash Utilization in Face of lower Ash Quality","authors":"D. Golden","doi":"10.14359/10584","DOIUrl":"https://doi.org/10.14359/10584","url":null,"abstract":"This paper describes a five-year Electric Power Research Institute (EPRI) program directed toward increasing ash utilization in the cement and concrete market within the United States, in the face of the impacts on ash quality due to more aggressive NOx controls. EPRI is undertaking this program to provide the technical basis for protecting the bulk sale of coal ash in high-volume applications in cement and concrete and other high volume civil engineering applications. In addition to higher carbon levels in ash from NOx control systems, problems associated with ammoniated ash have become a major concern for coal-fired facilities in recent years as a result of the increased use of ammonia-based environmental control technologies. Many coal-fired power producers have become concerned that post-combustion NOx controls could lead to fly ash containing high levels of ammonia. Therefore, EPRI conducted a research program designed to assist power producers to evaluate and mitigate the impacts of high carbon and ammoniated ash.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128557437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matte, M. Cheyrezy, M. Moranville, C. Richet, J. Torrenti
The Reactive Powder Concretes (RPC) are well known for their high strength, but they also present good performances regarding durability aspect due to their very dense microstructure. Studies were made to evaluate the durability of RPC to: freeze-thaw scaling, carbonation, chloride ions diffusion, abrasion coefficient and shrinkage. Their very good performance characteristics have led to a specific research program to evaluate the long-term durability of RPC for nuclear waste containment. Several kinds of potential degradation are studied, but here only the attack by de-ionized water, a very severe leaching test, will be presented. After pre-determined periods, the material was analyzed regarding its microstructure (altered depth, composition and mineralogical changes), porosity and ion transport properties. The results of SEM, X-ray diffraction, mercury intrusion porosimetry, BET pore-size and tritium diffusion coefficient analyses are presented.
{"title":"Durability of Reactive Powder Concrete When Subjected to a leaching Test","authors":"Matte, M. Cheyrezy, M. Moranville, C. Richet, J. Torrenti","doi":"10.14359/10593","DOIUrl":"https://doi.org/10.14359/10593","url":null,"abstract":"The Reactive Powder Concretes (RPC) are well known for their high strength, but they also present good performances regarding durability aspect due to their very dense microstructure. Studies were made to evaluate the durability of RPC to: freeze-thaw scaling, carbonation, chloride ions diffusion, abrasion coefficient and shrinkage. Their very good performance characteristics have led to a specific research program to evaluate the long-term durability of RPC for nuclear waste containment. Several kinds of potential degradation are studied, but here only the attack by de-ionized water, a very severe leaching test, will be presented. After pre-determined periods, the material was analyzed regarding its microstructure (altered depth, composition and mineralogical changes), porosity and ion transport properties. The results of SEM, X-ray diffraction, mercury intrusion porosimetry, BET pore-size and tritium diffusion coefficient analyses are presented.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128350009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Although 37 million tons of concrete wastes have been generated annually in Japan, the use of recycled aggregate for concrete is limited because of low density and high absorption due to adhered cement paste and mortar. A new method to produce high quality recycled aggregate by heating and grinding concrete rubbles to separate cement portions adhering to aggregate was developed recently. In this process, by-product powder with the fineness of 400 m2/kg is generated. By-product recycled concrete powder consists of fine particles of hydrated cement and crushed aggregate. To utilize the recycled concrete powder as concrete additives two series of experiments were performed to make clear the effect of recycled powder. Self-compacting concrete with recycled concrete powder, ground blast-furnace slag and ground limestone were tested for slump-flow, compressive strength, modulus of elasticity and drying shrinkage. Reduction in superplasticizing effect of high-range water reducer was found for concrete with recycled concrete powder. Compressive strength of concrete with recycled concrete powder was the same as those with ground limestone, and lower than those with ground slag. Concrete with recycled concrete powder showed lower elastic modulus and higher drying shrinkage than those with ground slag and ground limestone. The recycled concrete powder is usable for self-compacting concrete without further processing, despite the possible increase in dosage of high-range water reducer for a given slump-flow and in drying shrinkage. The addition of ground blast-furnace slag together with recycled concrete powder to self-compacting concrete improved superplasticizing effect of high-range water reducer and properties of concrete.
{"title":"Use of Recycled Concrete Powder in Self-Compacting Concrete","authors":"H. Kasami, M. Hosino, T. Arasima, H. Tateyasiki","doi":"10.14359/10590","DOIUrl":"https://doi.org/10.14359/10590","url":null,"abstract":"Although 37 million tons of concrete wastes have been generated annually in Japan, the use of recycled aggregate for concrete is limited because of low density and high absorption due to adhered cement paste and mortar. A new method to produce high quality recycled aggregate by heating and grinding concrete rubbles to separate cement portions adhering to aggregate was developed recently. In this process, by-product powder with the fineness of 400 m2/kg is generated. By-product recycled concrete powder consists of fine particles of hydrated cement and crushed aggregate. To utilize the recycled concrete powder as concrete additives two series of experiments were performed to make clear the effect of recycled powder. Self-compacting concrete with recycled concrete powder, ground blast-furnace slag and ground limestone were tested for slump-flow, compressive strength, modulus of elasticity and drying shrinkage. Reduction in superplasticizing effect of high-range water reducer was found for concrete with recycled concrete powder. Compressive strength of concrete with recycled concrete powder was the same as those with ground limestone, and lower than those with ground slag. Concrete with recycled concrete powder showed lower elastic modulus and higher drying shrinkage than those with ground slag and ground limestone. The recycled concrete powder is usable for self-compacting concrete without further processing, despite the possible increase in dosage of high-range water reducer for a given slump-flow and in drying shrinkage. The addition of ground blast-furnace slag together with recycled concrete powder to self-compacting concrete improved superplasticizing effect of high-range water reducer and properties of concrete.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"65 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131775810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The properties of concrete containing foundry sand as a partial replacement of fine aggregate were investigated. Three types of sand used in foundries were considered, the white fine sand without the addition of clay and coal, the foundry sand before casting (blended), and the foundry sand after casting (spent). The standard sand (Class M) was partially replaced by (0%, 25%, 50%, 75%, and 100%) these types of sand. Thirteen concrete mixtures were employed to conduct this study. Concrete strength up to 90 days and length change (drying shrinkage and expansion) up to 60 days were determined. As the replacement level of standard sand with sand used in foundries increased, the strength of concrete decreased. Concrete containing white sand showed somewhat similar strength to those containing spent sand at all replacement levels. The presence of high percentage of blended sand in the concrete mixture caused a reduction in strength as compared with concrete incorporating white sand or spent sand. The increase in strength was not observed at low replacement levels (less than 50%). The length change of concrete increased as the replacement level of standard sand with the three types of sand increased. Drying shrinkage values were higher in concrete containing spent sand and lower in concrete containing white sand. Expansion was generally lower in concrete containing white sand as compared with the other two types (blended and spent) at a low sand replacement level of 25%; and, a different trend was obtained at higher levels.
{"title":"Mechanical Properties of Concrete Containing Foundry Sand","authors":"J. Khatib, D. J. Ellis","doi":"10.14359/10612","DOIUrl":"https://doi.org/10.14359/10612","url":null,"abstract":"The properties of concrete containing foundry sand as a partial replacement of fine aggregate were investigated. Three types of sand used in foundries were considered, the white fine sand without the addition of clay and coal, the foundry sand before casting (blended), and the foundry sand after casting (spent). The standard sand (Class M) was partially replaced by (0%, 25%, 50%, 75%, and 100%) these types of sand. Thirteen concrete mixtures were employed to conduct this study. Concrete strength up to 90 days and length change (drying shrinkage and expansion) up to 60 days were determined. As the replacement level of standard sand with sand used in foundries increased, the strength of concrete decreased. Concrete containing white sand showed somewhat similar strength to those containing spent sand at all replacement levels. The presence of high percentage of blended sand in the concrete mixture caused a reduction in strength as compared with concrete incorporating white sand or spent sand. The increase in strength was not observed at low replacement levels (less than 50%). The length change of concrete increased as the replacement level of standard sand with the three types of sand increased. Drying shrinkage values were higher in concrete containing spent sand and lower in concrete containing white sand. Expansion was generally lower in concrete containing white sand as compared with the other two types (blended and spent) at a low sand replacement level of 25%; and, a different trend was obtained at higher levels.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126026551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alkali-aggregate reactivity, a reaction between the alkalies in the concrete pore fluid and certain siliceous aggregates was identified as a cause of disruptive expansion in concrete in Nova Scotia in 1962. Powerhouse structures, constructed with concrete containing meta-sediments and biotite schists, which are commonly used as concrete aggregate in Nova Scotia, caused expansion which created problems with the operation of the plants within 10 years after construction. Extensive studies in the mid 1960's and late 1980's of operating quarries and deteriorated structures, indicated that the reactive aggregates were widespread. Studies in the 1980's on the use of low calcium fly ash as a replacement or addition for portland cement showed conclusively that the reaction could be ameliorated with 15 to 30 percent fly ash replacement of the cement. Low calcium fly ash is now used systematically to lessen the potential for alkali-aggregate reaction.
{"title":"Expansion of Powerhouse Structures Due to Alkali-Aggregate Reaction and the Use of low Calcium Fly Ash to Ameliorate the Reaction in Future Construction","authors":"W. Langley, E. Brown","doi":"10.14359/10576","DOIUrl":"https://doi.org/10.14359/10576","url":null,"abstract":"Alkali-aggregate reactivity, a reaction between the alkalies in the concrete pore fluid and certain siliceous aggregates was identified as a cause of disruptive expansion in concrete in Nova Scotia in 1962. Powerhouse structures, constructed with concrete containing meta-sediments and biotite schists, which are commonly used as concrete aggregate in Nova Scotia, caused expansion which created problems with the operation of the plants within 10 years after construction. Extensive studies in the mid 1960's and late 1980's of operating quarries and deteriorated structures, indicated that the reactive aggregates were widespread. Studies in the 1980's on the use of low calcium fly ash as a replacement or addition for portland cement showed conclusively that the reaction could be ameliorated with 15 to 30 percent fly ash replacement of the cement. Low calcium fly ash is now used systematically to lessen the potential for alkali-aggregate reaction.","PeriodicalId":184301,"journal":{"name":"\"SP-200: Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology-Proceeding, Fifth International Conference\"","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125075434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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