A series of viscosity agents, some of which have no tendancy to absorb onto cement particles, has been studied for self-compacting concrete. It was found that the mortar rheology of self-compacting concrete is controlled by the adsorption nature of viscosity agents. The adsorptive viscosity agents such as cellulose derivatives from bridge structures and compete with the superplasticizers (SP) to occupy at adsorption sites once the agents adsorb on the surface of the cmeent particles in the mortar.This reduces the fluidity of the mortar. A use of the non-adsorptive viscosity agents, on the other hand, accomplishes the adequate fluidity and viscosity of the mortar. In addition, the adsorption sites on the cement particles are reserved for the SP even such agents are used. In order to understand how the viscosity agents work, the adsorption amounts, the zeta potentials and the particle size distributions were observed, while the interaction between the admixtures were examined.
{"title":"Study of Non-Adsorptive Viscosity Agents Applied to Self-Compacting Concrete","authors":"H. Yammamuro, T. Izumi, T. Mizunuma","doi":"10.14359/6196","DOIUrl":"https://doi.org/10.14359/6196","url":null,"abstract":"A series of viscosity agents, some of which have no tendancy to absorb onto cement particles, has been studied for self-compacting concrete. It was found that the mortar rheology of self-compacting concrete is controlled by the adsorption nature of viscosity agents. The adsorptive viscosity agents such as cellulose derivatives from bridge structures and compete with the superplasticizers (SP) to occupy at adsorption sites once the agents adsorb on the surface of the cmeent particles in the mortar.This reduces the fluidity of the mortar. A use of the non-adsorptive viscosity agents, on the other hand, accomplishes the adequate fluidity and viscosity of the mortar. In addition, the adsorption sites on the cement particles are reserved for the SP even such agents are used. In order to understand how the viscosity agents work, the adsorption amounts, the zeta potentials and the particle size distributions were observed, while the interaction between the admixtures were examined.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84610712","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}
A super workable concrete is defined as the concrete which has excellent deformability, high resistance to segregation, and can be filled into heavily reinforced areas without applying vibration. High deformability and high resistance to segregation are important properties of super workable concrete. Since these properties are essentially opposite in nature, they have a tendency to be sensitive to quality fluctuations of materials in comparison to conventional concrete when manufactured at ready mixed concrete plants. For improvement of manufacturing and handling, the authors developed the super workable concrete using B-1, 3-Glucan (Curdlan) which is produced by a fermentation process as a viscosity agent. The purpose of this study is to investigate the properties of B-1, 3-Glucan which gives a super workable concrete and the mechanism by which it produces such effects. The results confirm that B-1, 3-Glucan exists in the form of independent swollen particles, calcium complex gel which have negative electric charge on their surface. They also indicate that B-1, 3-Glucan has the ability to increase the viscosity of cement slurry. Thus, B-1, 3-Glucan gives and effect to increase plastic viscosity without changing yield value of a mortar, which was obtained by wet-screening a concrete.
{"title":"\"Property of p-1, 3-Glucan (Curdlan) as a Viscosity Agent for Super-Workable Concrete\"","authors":"Y. Matsuoka, T. Shindoh, K. Yakota, S. Kusui","doi":"10.14359/6198","DOIUrl":"https://doi.org/10.14359/6198","url":null,"abstract":"A super workable concrete is defined as the concrete which has excellent deformability, high resistance to segregation, and can be filled into heavily reinforced areas without applying vibration. High deformability and high resistance to segregation are important properties of super workable concrete. Since these properties are essentially opposite in nature, they have a tendency to be sensitive to quality fluctuations of materials in comparison to conventional concrete when manufactured at ready mixed concrete plants. For improvement of manufacturing and handling, the authors developed the super workable concrete using B-1, 3-Glucan (Curdlan) which is produced by a fermentation process as a viscosity agent. The purpose of this study is to investigate the properties of B-1, 3-Glucan which gives a super workable concrete and the mechanism by which it produces such effects. The results confirm that B-1, 3-Glucan exists in the form of independent swollen particles, calcium complex gel which have negative electric charge on their surface. They also indicate that B-1, 3-Glucan has the ability to increase the viscosity of cement slurry. Thus, B-1, 3-Glucan gives and effect to increase plastic viscosity without changing yield value of a mortar, which was obtained by wet-screening a concrete.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78283356","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}
A. Jeknavorian, L. Roberts, H. K. L. Jardine, D. Darwin
A new family of comb polymers has been developed that have been found to overcome many performance shortcomings typically exhibited by conventional high range water reducing agents, commonly referred to as superplasticizers. This paper discusses some theoretical considerations associated with comb polymer type superplasticizers, and reports on several key performance advantages such as extended slump life without prolonged set time, minimal variation in slump and air performance as a function of cement brand, and linear dosage response in mortar flow tests.
{"title":"Condensed Polyacrylic Acid-Aminated Polyet her Polymers as Superplasticizers for Concrete","authors":"A. Jeknavorian, L. Roberts, H. K. L. Jardine, D. Darwin","doi":"10.14359/6178","DOIUrl":"https://doi.org/10.14359/6178","url":null,"abstract":"A new family of comb polymers has been developed that have been found to overcome many performance shortcomings typically exhibited by conventional high range water reducing agents, commonly referred to as superplasticizers. This paper discusses some theoretical considerations associated with comb polymer type superplasticizers, and reports on several key performance advantages such as extended slump life without prolonged set time, minimal variation in slump and air performance as a function of cement brand, and linear dosage response in mortar flow tests.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78618997","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}
R. Fratesi, G. Moriconi, R. Tittarelli, M. Collepardi
The influence of silane-based hydrophobic products - used as concrete chemical admixtures - on the corrosion of steel rebars was studied. Reinforced concrete specimens with and without a silane admixture were exposed to seawater or to aqueous solutions of de-icing salts containing chlorides. Sound and uncracked or deliberately pre-cracked concrete specimens were manufactured and cured before the exposure to aggressive environments. In the pre-cracked specimens the concrete crack tip was in contact with the steel reinforcement. The results - in terms of corrosion observed on the steel reinforcement - were compared with those obtained on the corresponding uncracked specimens. In uncracked specimens any corrosion process was completely blocked independently of the water to cement ratio and concrete cover provided that hydrophobized concrete was used. This effect was due to lack of water penetration, and then of the chloride ingress, through the pores of the hydrophobized cement matrix. In uncracked specimens without the silane admixture, there was corrosion risk when high water to cement ratio and/or thin concrete cover were adopted. On the other hand, corrosion of steel rebars was surprisingly more severe in cracked specimens manufactured by hydrophobized concrete rather than in the corresponding reference concrete specimens without the hydrophobic admixture. These results can be interpreted by admitting that oxygen diffusion - which is needed to feed the corrosion process - can occur directly as a gaseous phase through the open concrete voids in hydrophobized concrete, whereas in concrete without silane oxygen can diffuse much more slowly only through the water filled concrete voids.
{"title":"The Influence of Hydrophobized Concrete on the Corrosion of Rebars","authors":"R. Fratesi, G. Moriconi, R. Tittarelli, M. Collepardi","doi":"10.14359/6180","DOIUrl":"https://doi.org/10.14359/6180","url":null,"abstract":"The influence of silane-based hydrophobic products - used as concrete chemical admixtures - on the corrosion of steel rebars was studied. Reinforced concrete specimens with and without a silane admixture were exposed to seawater or to aqueous solutions of de-icing salts containing chlorides. Sound and uncracked or deliberately pre-cracked concrete specimens were manufactured and cured before the exposure to aggressive environments. In the pre-cracked specimens the concrete crack tip was in contact with the steel reinforcement. The results - in terms of corrosion observed on the steel reinforcement - were compared with those obtained on the corresponding uncracked specimens. In uncracked specimens any corrosion process was completely blocked independently of the water to cement ratio and concrete cover provided that hydrophobized concrete was used. This effect was due to lack of water penetration, and then of the chloride ingress, through the pores of the hydrophobized cement matrix. In uncracked specimens without the silane admixture, there was corrosion risk when high water to cement ratio and/or thin concrete cover were adopted. On the other hand, corrosion of steel rebars was surprisingly more severe in cracked specimens manufactured by hydrophobized concrete rather than in the corresponding reference concrete specimens without the hydrophobic admixture. These results can be interpreted by admitting that oxygen diffusion - which is needed to feed the corrosion process - can occur directly as a gaseous phase through the open concrete voids in hydrophobized concrete, whereas in concrete without silane oxygen can diffuse much more slowly only through the water filled concrete voids.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79032650","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}
H. Wang, K. Eubanks, B. Fitch, C. Manissero, F. Marin
This paper describes the development and applications of several lithium-based chemical admixtures for set control of cementitious based construction and building materials. Comparative evaluations show the effect of these admixtures on the set time of (1) calcium aluminate cement; (2) portland cement; and (3) blended systems of calcium aluminate cement and portland cement. General information is provided to address the principles of material selection, dosage rate and application of cementitious systems.
{"title":"Effective Use of Lithium-Based Admixtures for Set Control of Cementitious Systems","authors":"H. Wang, K. Eubanks, B. Fitch, C. Manissero, F. Marin","doi":"10.14359/6218","DOIUrl":"https://doi.org/10.14359/6218","url":null,"abstract":"This paper describes the development and applications of several lithium-based chemical admixtures for set control of cementitious based construction and building materials. Comparative evaluations show the effect of these admixtures on the set time of (1) calcium aluminate cement; (2) portland cement; and (3) blended systems of calcium aluminate cement and portland cement. General information is provided to address the principles of material selection, dosage rate and application of cementitious systems.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87040735","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}
In the presence of silica fume (SF), the hydration of high alumina cement (HAC) produces hexagonal hydrates (CaH10 and C2AH8) which do not convert into the cubic hydrate (C3AH6) and therefore the related strength loss does not occur: this is due to the formation of C2ASH8 which blocks the conversion process. However, due to the presence of SF, the required mixing water significantly increases. Therefore, an effective water reducing admixture is needed to compensate for the presence of SF and to allow the mixture to attain the same strength level of pure HAC at early and later ages. Two alternative admixtures - sodium tripolyphosphate (TPP) and/or acrylic polymer (AP)< instead of other traditional superplasticizers - were studied as water reducers for the blended HAC-SF binder. Both were very effective in reducing the amount of mixing water. However, in the presence of TPP there was a quick fluidity loss after about 45 min. This was a sort of flash set of the binder followed by a sudden heat development. Due to the restrained thermal expansion of the hotter nucleus with respect to the colder surface areas, microcracks formed. Upon contact with liquid water microcracks changed to macrocracks. This severe distress caused a strength failure of the specimens. This change was produced by the pressure exerted by crystal growth of hexagonal hydrates in the water-filled microcracks. By reducing the fluidity loss - for instance by using AP instead of TPP - the heat development became more gradual and therefore microcracks as well as macrocracks disappeared. Consequently any strength loss was removed in the blended HAC-SF binder.
{"title":"High Alumina Cement-Silica Fume Mixtures in the Presence of Superplasticizers","authors":"S. Monosi, R. Troli, M. Collepardi","doi":"10.14359/6205","DOIUrl":"https://doi.org/10.14359/6205","url":null,"abstract":"In the presence of silica fume (SF), the hydration of high alumina cement (HAC) produces hexagonal hydrates (CaH10 and C2AH8) which do not convert into the cubic hydrate (C3AH6) and therefore the related strength loss does not occur: this is due to the formation of C2ASH8 which blocks the conversion process. However, due to the presence of SF, the required mixing water significantly increases. Therefore, an effective water reducing admixture is needed to compensate for the presence of SF and to allow the mixture to attain the same strength level of pure HAC at early and later ages. Two alternative admixtures - sodium tripolyphosphate (TPP) and/or acrylic polymer (AP)< instead of other traditional superplasticizers - were studied as water reducers for the blended HAC-SF binder. Both were very effective in reducing the amount of mixing water. However, in the presence of TPP there was a quick fluidity loss after about 45 min. This was a sort of flash set of the binder followed by a sudden heat development. Due to the restrained thermal expansion of the hotter nucleus with respect to the colder surface areas, microcracks formed. Upon contact with liquid water microcracks changed to macrocracks. This severe distress caused a strength failure of the specimens. This change was produced by the pressure exerted by crystal growth of hexagonal hydrates in the water-filled microcracks. By reducing the fluidity loss - for instance by using AP instead of TPP - the heat development became more gradual and therefore microcracks as well as macrocracks disappeared. Consequently any strength loss was removed in the blended HAC-SF binder.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87972970","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}
Very little has been known about the relationship between the specific properties of particles and the viscosity of suspensions containing them, although it seems very important for the reliable design of quality in the actual use. After the introduction of new rheological theory by Hattori and Izumi (HI theory) based on the DLVO theory and on the structural viscosity theory, it became possible to estimate the time-dependent viscosity of suspension either agitated or unagitated by the calculation. Based on the HI theory, the time-dependent viscosity of unagitated cement paste, for which the completely dispersed state was assumed as the initial condition, was calculated and results of calculations for the estimation of viscosity increase of cement pastes are presented by the curves showing effects of various properties of cement powders and the condition of use.
{"title":"Estimation of Effects of the Specific Properies of Particles on the Viscosities of Cement Pastes","authors":"K. Hattori, K. lzumi","doi":"10.14359/6200","DOIUrl":"https://doi.org/10.14359/6200","url":null,"abstract":"Very little has been known about the relationship between the specific properties of particles and the viscosity of suspensions containing them, although it seems very important for the reliable design of quality in the actual use. After the introduction of new rheological theory by Hattori and Izumi (HI theory) based on the DLVO theory and on the structural viscosity theory, it became possible to estimate the time-dependent viscosity of suspension either agitated or unagitated by the calculation. Based on the HI theory, the time-dependent viscosity of unagitated cement paste, for which the completely dispersed state was assumed as the initial condition, was calculated and results of calculations for the estimation of viscosity increase of cement pastes are presented by the curves showing effects of various properties of cement powders and the condition of use.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88457963","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 reports the properties of cement paste, mortar and fresh and hardened concrete using superplasticizers with electric repulsion, steric barrier and those possessing both dispersing mechanisms and their interaction with cementitious materials having pozzolanic properties and those without pozzolanic properties prepared by different mixing methods. It was found that there is an optimum W/C for the primary water (W1/C) where bleeding is minimum and thus dispersion state is optimum. The fresh properties of concrete prepared by double mixing method are different from those by conventional mixing method (Single mixing). Also, when superplasticizers are added in primary water (W1), fresh properties of concrete are different from those when added in secondary water (W2). The effect of dosing method of superplasticizers and replacement of cement with different cementitious materials, varies greatly with the type of superplasticizers.
{"title":"Effect . . MIXI: of Types of Superplasticizers and ng Methods on the Properties of Cementitious Systems","authors":"E. Tazwa, B. Mtasiwa, M. Takahasi","doi":"10.14359/6206","DOIUrl":"https://doi.org/10.14359/6206","url":null,"abstract":"This paper reports the properties of cement paste, mortar and fresh and hardened concrete using superplasticizers with electric repulsion, steric barrier and those possessing both dispersing mechanisms and their interaction with cementitious materials having pozzolanic properties and those without pozzolanic properties prepared by different mixing methods. It was found that there is an optimum W/C for the primary water (W1/C) where bleeding is minimum and thus dispersion state is optimum. The fresh properties of concrete prepared by double mixing method are different from those by conventional mixing method (Single mixing). Also, when superplasticizers are added in primary water (W1), fresh properties of concrete are different from those when added in secondary water (W2). The effect of dosing method of superplasticizers and replacement of cement with different cementitious materials, varies greatly with the type of superplasticizers.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82152082","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}
Concrete tiles were produced according to a new technology based on a vacuum treatment combined with a vibro-compacting placement of superplasticized mixture. Three concrete mixtures (all vibro-compacted according to this technique) were manufactured with different water-cement ratio (0.50 or 0.32) and in the absence or in the presence of the vacuum treatment. Measurements of flexural strength, dimensional stability, SEM, image analysis and particle size distribution of anhydrous cement in concrete tiles were carried out. The vacuum treatment, which removed entrapped air voids from the fresh mixture during the vibro-compacting placement, increased flexural strength but did not change the dimensional stability. The reduction in the W/C from 0.50 to 0.32 significantly increased flexural strength. It is also improved the dimensional stability in terms of a lower curling effect caused by different humidity exposures of the two opposite faces of the concrete tile. The combination of vacuum treatment with low W/C produces a macro-defect free and low micro-porosity cement matrix which is responsible for the high strength and low curling effect of these concrete tiles.
{"title":"Improved Superplasticized Precast Concrete Tiles","authors":"G. Ferrari, V. Riunno, D. Salvioni, P. Tassone","doi":"10.14359/6221","DOIUrl":"https://doi.org/10.14359/6221","url":null,"abstract":"Concrete tiles were produced according to a new technology based on a vacuum treatment combined with a vibro-compacting placement of superplasticized mixture. Three concrete mixtures (all vibro-compacted according to this technique) were manufactured with different water-cement ratio (0.50 or 0.32) and in the absence or in the presence of the vacuum treatment. Measurements of flexural strength, dimensional stability, SEM, image analysis and particle size distribution of anhydrous cement in concrete tiles were carried out. The vacuum treatment, which removed entrapped air voids from the fresh mixture during the vibro-compacting placement, increased flexural strength but did not change the dimensional stability. The reduction in the W/C from 0.50 to 0.32 significantly increased flexural strength. It is also improved the dimensional stability in terms of a lower curling effect caused by different humidity exposures of the two opposite faces of the concrete tile. The combination of vacuum treatment with low W/C produces a macro-defect free and low micro-porosity cement matrix which is responsible for the high strength and low curling effect of these concrete tiles.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75273510","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}
Anti-washout admixtures are used to enhance stability of cement-based systems, such as in the case of concrete intended for underwater repair of marine structures, self-leveling and segregation-free concrete for above-water placement, and for shotcrete. Mixtures modified with an anti-washout admixture can also incorporate silica fume or fly ash to enhance fresh and hardened properties. Anti-washout admixtures are relatively new, and there is a lack of systematic data comparing the efficiency, advantages, and limitations of using them in concrete, especially in silica fume or fly ash concrete. A laboratory investigation was undertaken to evaluate the effect of cementitious material combinations on fresh and hardened properties of fluid concrete made with three commonly used anti-washout admixtures. Each anti-washout admixture was used at two concentrations corresponding to relatively low and medium dosages that are typically used in concrete. The anti-washout admixtures included a power-based product, a liquid-based cellulosic material, and a liquid-based microbial polysaccharide. The mixtures were prepared with 100% of a Type 10 cement, a blended silica fume cement containing 8% silica fume, as well as a Class F fly ash used at 20% replacement. All mixtures were made with a 0.41 water-to-cementitious materials ratio and had initial slump values of 230+_ 5 mm (9.1 +_0.2 in.). The influence of fly ash and silica fume incorporation on slump retention, washout resistance, bleeding, segregation, surface settlement, setting time, compressive and splitting-tensile strength developments was evaluated for the fluid mixtures. The paper summarizes the results of the experimental study that involved the comparison of data obtained from 21 concrete mixtures.
{"title":"Effect of Silica Fume and Fly Ash Replacement on Stability and Strength of Fluid Concrete Containing Anti-Washout Admixture","authors":"K. Khayat, M. E. Gattioui, C. Nmai","doi":"10.14359/6209","DOIUrl":"https://doi.org/10.14359/6209","url":null,"abstract":"Anti-washout admixtures are used to enhance stability of cement-based systems, such as in the case of concrete intended for underwater repair of marine structures, self-leveling and segregation-free concrete for above-water placement, and for shotcrete. Mixtures modified with an anti-washout admixture can also incorporate silica fume or fly ash to enhance fresh and hardened properties. Anti-washout admixtures are relatively new, and there is a lack of systematic data comparing the efficiency, advantages, and limitations of using them in concrete, especially in silica fume or fly ash concrete. A laboratory investigation was undertaken to evaluate the effect of cementitious material combinations on fresh and hardened properties of fluid concrete made with three commonly used anti-washout admixtures. Each anti-washout admixture was used at two concentrations corresponding to relatively low and medium dosages that are typically used in concrete. The anti-washout admixtures included a power-based product, a liquid-based cellulosic material, and a liquid-based microbial polysaccharide. The mixtures were prepared with 100% of a Type 10 cement, a blended silica fume cement containing 8% silica fume, as well as a Class F fly ash used at 20% replacement. All mixtures were made with a 0.41 water-to-cementitious materials ratio and had initial slump values of 230+_ 5 mm (9.1 +_0.2 in.). The influence of fly ash and silica fume incorporation on slump retention, washout resistance, bleeding, segregation, surface settlement, setting time, compressive and splitting-tensile strength developments was evaluated for the fluid mixtures. The paper summarizes the results of the experimental study that involved the comparison of data obtained from 21 concrete mixtures.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75687224","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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