The importance of molecular weight as a parameter influencing the performance of water-reducing admixture in cement paste was investigated. The sulphomorthlolated ALCELL lignin sample was divided into four fractions of different molecular weight. The fractionation was performed by membrane ultrafiltration on a small laboratory unit. Advanced hydrophilic membranes with a I, qo and 50 kd nominal MW cut-off and effective area of 63 cm2 were used. Molecular weight distribution, average molecular weights (Mn, Mw, Mz and Mz+1), and polydispersity of the original sample and its fractions were determined by high-performance aqueous size-exclusion chromatography. The five samples, prepared as 20% aqueous solutions, were used as water-reducing admixtures. Their influence on fresh cement pastes was examined using the torque and mini-slump tests. The torque test was performed to investigate the fluidifying and retarding effects of the samples. Changes in torque resistance were monitored by a computerized system, giving an indication of the degree of dispersion and set retardation. The mini-slump test was used to determine the workability and air-entrainment of the fresh cement paste . The dependence of the properties of the fresh cement pastes on the lignosulphonate molecular weight was studied. It was found that the lower the molecular weight of the lignosulphonate sample the higher the set retardation of the cement paste. The highest fluidication and lowest air-entrainment were observed when the immediate molecular weight samples were used. The optimum molecular weight fraction in each particular experiment was always more effective than the original unfractionated sample. Fractions with extremely low efficiency were also identified. The data obtained can be utilized in optimization of lignosulphonate admixture performance.
{"title":"Regularities of Hydration and Structure Formation of Cement Pastes in the Presence of Superplasticizers with Different Molecular Mass","authors":"A. Vovk, G. Vovk, A. Usherov-Marshak","doi":"10.14359/6212","DOIUrl":"https://doi.org/10.14359/6212","url":null,"abstract":"The importance of molecular weight as a parameter influencing the performance of water-reducing admixture in cement paste was investigated. The sulphomorthlolated ALCELL lignin sample was divided into four fractions of different molecular weight. The fractionation was performed by membrane ultrafiltration on a small laboratory unit. Advanced hydrophilic membranes with a I, qo and 50 kd nominal MW cut-off and effective area of 63 cm2 were used. Molecular weight distribution, average molecular weights (Mn, Mw, Mz and Mz+1), and polydispersity of the original sample and its fractions were determined by high-performance aqueous size-exclusion chromatography. The five samples, prepared as 20% aqueous solutions, were used as water-reducing admixtures. Their influence on fresh cement pastes was examined using the torque and mini-slump tests. The torque test was performed to investigate the fluidifying and retarding effects of the samples. Changes in torque resistance were monitored by a computerized system, giving an indication of the degree of dispersion and set retardation. The mini-slump test was used to determine the workability and air-entrainment of the fresh cement paste . The dependence of the properties of the fresh cement pastes on the lignosulphonate molecular weight was studied. It was found that the lower the molecular weight of the lignosulphonate sample the higher the set retardation of the cement paste. The highest fluidication and lowest air-entrainment were observed when the immediate molecular weight samples were used. The optimum molecular weight fraction in each particular experiment was always more effective than the original unfractionated sample. Fractions with extremely low efficiency were also identified. The data obtained can be utilized in optimization of lignosulphonate admixture performance.","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":"75425653","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. Flatt, Y. F. Houst, P. Bowen, H. Hofmann, J. Widmer, U. Sulser, U. Mäder, T. A. Bürge
Synopsis: It is broadly recognized that the adsorption of superplasticizers on cement particles is a key factor in determining the rheology of concrete. In order to avoid the problems linked to the hydration of cement, the adsorption of superplasticizers is often studied on unreactive model powders. However, in order for the model system to remain as close as possible to cement, the surface should have a similar charge and a similar chemical nature. Furthermore, the pH of the solution should be close to that of the hydrating cement (about 12.5). Under these conditions, cement has been shown to have a positively charged surface. The model powders used in this study were Mg(OH) 2 and dead burnt MgO, which have nominal isoelectric points of 12.0 and 12.4 respectively, and which are chemically similar to Ca(OH) 2 and CaO. The surface charge of such model suspensions was studied as a function of added superplasticizer. These were either commercially available or currently under development, ranging from strongly to very weakly ionic. Adsorption isotherms for two polymeric superplasticizers, with similar structures but with different ionic group spacing, have been measured for both MgO and Mg(OH) 2 at pH 12 and 11.3 respectively and between 10 and 40°C. Results showed a strong temperature dependence for the adsorption of the less ionic polymer on MgO.
{"title":"Interaction of Superplasticizers with Model Powders in a Highly Alkaline Medium","authors":"R. Flatt, Y. F. Houst, P. Bowen, H. Hofmann, J. Widmer, U. Sulser, U. Mäder, T. A. Bürge","doi":"10.14359/6211","DOIUrl":"https://doi.org/10.14359/6211","url":null,"abstract":"Synopsis: It is broadly recognized that the adsorption of superplasticizers on cement particles is a key factor in determining the rheology of concrete. In order to avoid the problems linked to the hydration of cement, the adsorption of superplasticizers is often studied on unreactive model powders. However, in order for the model system to remain as close as possible to cement, the surface should have a similar charge and a similar chemical nature. Furthermore, the pH of the solution should be close to that of the hydrating cement (about 12.5). Under these conditions, cement has been shown to have a positively charged surface. The model powders used in this study were Mg(OH) 2 and dead burnt MgO, which have nominal isoelectric points of 12.0 and 12.4 respectively, and which are chemically similar to Ca(OH) 2 and CaO. The surface charge of such model suspensions was studied as a function of added superplasticizer. These were either commercially available or currently under development, ranging from strongly to very weakly ionic. Adsorption isotherms for two polymeric superplasticizers, with similar structures but with different ionic group spacing, have been measured for both MgO and Mg(OH) 2 at pH 12 and 11.3 respectively and between 10 and 40°C. Results showed a strong temperature dependence for the adsorption of the less ionic polymer on MgO.","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":"75791080","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}
S. Amey, J. Buffenbarger, J. Daczko, D. A. Johnson
An investigation is presented to evaluate the effect an ester-amine admixture (EA) has on the durability of concrete exposed to sulfate and sulfuric acid solutions traditionally detrimental to concrete. Prisms were exposed to a MgSO4 environment under cyclic wet/dry conditions for 336 days. Other prisms were exposed to a H2SO4 environment at pH=1 for 100 days. During the sulfate exposures, the concrete specimens were evaluated by appearance and length change over time. During the sulfuric acid exposures, the concrete specimens were evaluated by the pH changes of the test solution. The ester-amine admixture was shown to be beneficial in reducing the initial susceptibility of concrete exposed to both environments. This benefit was also observed to improve the resistance of already low permeability concrete containing pozzolans such as fly ash and silica fume. The behavior was explained by the admixture's reaction products which line the concrete pore matrix. A mechanism that differentiates the action of the EA from other permeability reducing materials (e.g., pozzolans) is proposed.
{"title":"Durability of Concrete Containing an Ester-Amine Admixture Exposed to Sulfate and Sulfuric Acid Solutions","authors":"S. Amey, J. Buffenbarger, J. Daczko, D. A. Johnson","doi":"10.14359/6223","DOIUrl":"https://doi.org/10.14359/6223","url":null,"abstract":"An investigation is presented to evaluate the effect an ester-amine admixture (EA) has on the durability of concrete exposed to sulfate and sulfuric acid solutions traditionally detrimental to concrete. Prisms were exposed to a MgSO4 environment under cyclic wet/dry conditions for 336 days. Other prisms were exposed to a H2SO4 environment at pH=1 for 100 days. During the sulfate exposures, the concrete specimens were evaluated by appearance and length change over time. During the sulfuric acid exposures, the concrete specimens were evaluated by the pH changes of the test solution. The ester-amine admixture was shown to be beneficial in reducing the initial susceptibility of concrete exposed to both environments. This benefit was also observed to improve the resistance of already low permeability concrete containing pozzolans such as fly ash and silica fume. The behavior was explained by the admixture's reaction products which line the concrete pore matrix. A mechanism that differentiates the action of the EA from other permeability reducing materials (e.g., pozzolans) is proposed.","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":"79417592","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 present paper a new analytical method for measuring the adsorption of naphthalene sulfonate formaldehyde condensate superplasticizers (NSFC) onto cement is described. By this method, based on the application of Gel Permeation Chromatography (GPC), it is possible to estimate the selective adsorption of the different components of these admixtures (B-naphthalene sulfonate, naphthalene disulfonates, polymer fraction). The results indicate that B-naphthalene sulfonate and naphthalene disulfonates are not substantially adsorbed onto the cement particles, independently on the cement used and the dosage of admixture. The polymeric fractions are adsorbed at different extent according to the dosage of superplasticizer and the cement used. Adsorption tests with two NSFC samples of different molecular weight indicate that the high molecular weight polymer fractions are preferably adsorbed over the low molecular weight fractions. The adsorption isotherms of the polymeric fraction of NSFC superplasticizers with different cements indicate that the saturation dosage depends on the chemical composition, the particle size and the specific surface area of the cements. Moreover, these results indicate that the NSFC polymer fraction is totally adsorbed on different cements up to a certain dosage of superplasticizer. This critical value seems to be related with the minimum dosage of superplasticizer to reach the optimum fluidity of cement mixtures. This observation could be put in relation with the preferred adsorption of the higher molecular weight fractions on NSFC, which exhibit a better superplasticizing effect.
{"title":"Adsorption of Naphthalene Sulfonate Superplasticizers by Cement Particles Through Gel Permeation Chromatography","authors":"G. Ferrari, T. Cerulli, P. Clemente, M. Dragoni","doi":"10.14359/6217","DOIUrl":"https://doi.org/10.14359/6217","url":null,"abstract":"In the present paper a new analytical method for measuring the adsorption of naphthalene sulfonate formaldehyde condensate superplasticizers (NSFC) onto cement is described. By this method, based on the application of Gel Permeation Chromatography (GPC), it is possible to estimate the selective adsorption of the different components of these admixtures (B-naphthalene sulfonate, naphthalene disulfonates, polymer fraction). The results indicate that B-naphthalene sulfonate and naphthalene disulfonates are not substantially adsorbed onto the cement particles, independently on the cement used and the dosage of admixture. The polymeric fractions are adsorbed at different extent according to the dosage of superplasticizer and the cement used. Adsorption tests with two NSFC samples of different molecular weight indicate that the high molecular weight polymer fractions are preferably adsorbed over the low molecular weight fractions. The adsorption isotherms of the polymeric fraction of NSFC superplasticizers with different cements indicate that the saturation dosage depends on the chemical composition, the particle size and the specific surface area of the cements. Moreover, these results indicate that the NSFC polymer fraction is totally adsorbed on different cements up to a certain dosage of superplasticizer. This critical value seems to be related with the minimum dosage of superplasticizer to reach the optimum fluidity of cement mixtures. This observation could be put in relation with the preferred adsorption of the higher molecular weight fractions on NSFC, which exhibit a better superplasticizing effect.","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":"81441875","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}
M. Shonaka, K. Kitagawa, H. Satoh, T. lzumi, T. Mizunuma
High range water reducing agents (superplasticizers), in general, adsorb the surface of cement particles and disperse the particles by means of electric force. Recently, there has been a development of a new type of high range water reducing agents which have characteristically long chains of polyethylene oxides (EO) as branches. When the new molecules adsorb on the particles, it is considered that long EO chains are expanded in the water/cement mixture and that each particle disperse due to their steric repulsion instead of electric. So, it can bring good workability to the concrete mix and retain fluidity for a longer period without retarding on the setting. Therefore, it can be applied to various concrete, such as high and ultra high strength concrete.
{"title":"Chemical Structures and Performance of New High-Range Water-Reducing and Air-Entraining Agents","authors":"M. Shonaka, K. Kitagawa, H. Satoh, T. lzumi, T. Mizunuma","doi":"10.14359/6204","DOIUrl":"https://doi.org/10.14359/6204","url":null,"abstract":"High range water reducing agents (superplasticizers), in general, adsorb the surface of cement particles and disperse the particles by means of electric force. Recently, there has been a development of a new type of high range water reducing agents which have characteristically long chains of polyethylene oxides (EO) as branches. When the new molecules adsorb on the particles, it is considered that long EO chains are expanded in the water/cement mixture and that each particle disperse due to their steric repulsion instead of electric. So, it can bring good workability to the concrete mix and retain fluidity for a longer period without retarding on the setting. Therefore, it can be applied to various concrete, such as high and ultra high strength 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":"78509932","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 consequence of drying shrinkage is intrinsic cracking due to some form of restraint. In thick sections of concrete, drying from the surface causes differential shrinkage and such internal restraint can be responsible for surface cracking because of the induced tensile stress. When thin drying concrete members are restrained externally, a time-dependant failure is likely unless drying shrinkage is minimized. Besides drying shrinkage, the potential for cracking depends on tensile creep and tensile strength or tensile strain capacity and such properties are not normally measured in the laboratory. The possible effects of chemical admixtures on the forgoing properties is also largely unknown. The current research is investigating the role of tensile creep in relieving the tensile stress induced by fully restraining the drying shrinkage of concrete with and without chemical and mineral admixtures. All the relevant properties contributing to the time-dependant strength are being measured using bobbin-shaped specimens previously developed for uniaxial creep determination. The present paper presents the findings for concretes with and without plasticizer and a new shrinkage reducing admixture. While the plasticizer has little influence on properties, the shrinkage reducing admixture significantly lowers the strength, elastic modulus, free drying shrinkage and creep. When restrained from the age of seven days all the concretes failed between 4 and 13 days, the concrete with the shrinkage reducing admixture failing at the lowest stress but after the longest time.
{"title":"The Influence of Chemical Admixtures on Restrained Drying Shrinkage of Concrete","authors":"J. Brooks, X. H. Jiang","doi":"10.14359/6187","DOIUrl":"https://doi.org/10.14359/6187","url":null,"abstract":"A consequence of drying shrinkage is intrinsic cracking due to some form of restraint. In thick sections of concrete, drying from the surface causes differential shrinkage and such internal restraint can be responsible for surface cracking because of the induced tensile stress. When thin drying concrete members are restrained externally, a time-dependant failure is likely unless drying shrinkage is minimized. Besides drying shrinkage, the potential for cracking depends on tensile creep and tensile strength or tensile strain capacity and such properties are not normally measured in the laboratory. The possible effects of chemical admixtures on the forgoing properties is also largely unknown. The current research is investigating the role of tensile creep in relieving the tensile stress induced by fully restraining the drying shrinkage of concrete with and without chemical and mineral admixtures. All the relevant properties contributing to the time-dependant strength are being measured using bobbin-shaped specimens previously developed for uniaxial creep determination. The present paper presents the findings for concretes with and without plasticizer and a new shrinkage reducing admixture. While the plasticizer has little influence on properties, the shrinkage reducing admixture significantly lowers the strength, elastic modulus, free drying shrinkage and creep. When restrained from the age of seven days all the concretes failed between 4 and 13 days, the concrete with the shrinkage reducing admixture failing at the lowest stress but after the longest time.","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":"72899957","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 is one of the most widely used construction materials in the world. In applications where appearance, durability, and permeability are of concern, reduction of cracking is a key need. A common cause of cracking is restrained drying shrinkage. Until very recently, drying shrinkage cracking has been controlled by reducing joint spacing, increasing reinforcement, and using expansive cements and admixtures. In this paper a new shrinkage-reducing admixture (SRA) is discussed. SRAs provide a convenient means of reducing drying as they are added during batching and mix easily into the concrete, The SRA material discussed in this paper improved workability and finishing as an added benefit. The effects of mixture proportioning, curing conditions, and SRA content on the long-term drying shrinkage reductions of 50% can be achieved, and that there is a significant improvement in restrained shrinkage performance. Even though the lowest absolute values for drying shrinkage occur with proper curing, there is still a substantial reduction in drying shrinkage for specimens cured for short times. It is shown that shrinkage reduction is directly related to the SRA addition rate as a percentage of the mixing water. Furthermore, data on large-scale field experiments show that substantial reduction in cracking is obtained for concretes treated with SRA.
{"title":"New Deveopments in Shrinkage-Reducing Admixtures","authors":"N. Berke, P. DallaireMichael, M. Hicks, A. Kerkar","doi":"10.14359/6222","DOIUrl":"https://doi.org/10.14359/6222","url":null,"abstract":"Concrete is one of the most widely used construction materials in the world. In applications where appearance, durability, and permeability are of concern, reduction of cracking is a key need. A common cause of cracking is restrained drying shrinkage. Until very recently, drying shrinkage cracking has been controlled by reducing joint spacing, increasing reinforcement, and using expansive cements and admixtures. In this paper a new shrinkage-reducing admixture (SRA) is discussed. SRAs provide a convenient means of reducing drying as they are added during batching and mix easily into the concrete, The SRA material discussed in this paper improved workability and finishing as an added benefit. The effects of mixture proportioning, curing conditions, and SRA content on the long-term drying shrinkage reductions of 50% can be achieved, and that there is a significant improvement in restrained shrinkage performance. Even though the lowest absolute values for drying shrinkage occur with proper curing, there is still a substantial reduction in drying shrinkage for specimens cured for short times. It is shown that shrinkage reduction is directly related to the SRA addition rate as a percentage of the mixing water. Furthermore, data on large-scale field experiments show that substantial reduction in cracking is obtained for concretes treated with SRA.","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":"82878661","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}
C. Jolicoeur, J. Sharman, A. L. Otis, M. Simard, M. Pagé
The variation in rheological properties of normal portland cement type-10 and blended silica fume (SF) cement pastes was investigated as a function of temperature (0-40 degrees) in order to elucidate changes in concrete workability with ambient temperature. The rheological parameters measured included the Kantro mini-slump (spreading areas, S) and the dynamic viscosity (n) at various hear rates as a function of superplasticizer concentration (sodium polynaphthalene sulfonate, PNS). To interpret the changes in fluidity of the cement pastes, the concentration of the superplasticizer in the solution phase was monitored as a function of time (0-2 hours); calorimetric measurements of the early cement hydration rate (0-3 hours) in the pastes were also measured in some cases. The variations observed in paste fluidity (S, or 1/n) at a given PNS dosage exhibit significant non-linear variations with temperature; the rate of change of S and 1/n with time (i.e. slump loss rate) are also found to be non-linear, usually with a maximum value in the interval 5-20 degrees. The non-linear effects are more pronounced with the SF cement than with the type-10 cement. The observations are interpreted tentatively on the basis of coupled physico-chemical effects involving PNS adsorption on cement and on silica, and the influence of PNS on the early hydration rate.
{"title":"The Influence of Temperature on the Rheological Properties of Superplasticized Cement Pastes","authors":"C. Jolicoeur, J. Sharman, A. L. Otis, M. Simard, M. Pagé","doi":"10.14359/6194","DOIUrl":"https://doi.org/10.14359/6194","url":null,"abstract":"The variation in rheological properties of normal portland cement type-10 and blended silica fume (SF) cement pastes was investigated as a function of temperature (0-40 degrees) in order to elucidate changes in concrete workability with ambient temperature. The rheological parameters measured included the Kantro mini-slump (spreading areas, S) and the dynamic viscosity (n) at various hear rates as a function of superplasticizer concentration (sodium polynaphthalene sulfonate, PNS). To interpret the changes in fluidity of the cement pastes, the concentration of the superplasticizer in the solution phase was monitored as a function of time (0-2 hours); calorimetric measurements of the early cement hydration rate (0-3 hours) in the pastes were also measured in some cases. The variations observed in paste fluidity (S, or 1/n) at a given PNS dosage exhibit significant non-linear variations with temperature; the rate of change of S and 1/n with time (i.e. slump loss rate) are also found to be non-linear, usually with a maximum value in the interval 5-20 degrees. The non-linear effects are more pronounced with the SF cement than with the type-10 cement. The observations are interpreted tentatively on the basis of coupled physico-chemical effects involving PNS adsorption on cement and on silica, and the influence of PNS on the early hydration rate.","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":"80672391","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}
Betanaphthalene sulfonate condensate (NS) and melamine sulfonate condensate (MS) polymers based superplasticizers have been extensively used in the Precast Industry. Continuous need for improving the performance of concrete has led to the development of products with a higher water reduction and thus higher early strength, typical of melamine based superplasticizers, but without the drawback of workability loss sometimes encountered with this kind of superplasticizers. The chemistry of the new product described in this article has been specifically designed to achieve high early and long term strength maintaining the workability typical of NS products at dosages in the range commonly used with melamines. The superior performance obtained with this new product makes it a good alternative to melamine based superplasticizers when used in precast applications. The paper reports the effect of the new B-naphthalene sulfonate based superplasticizer on water reduction, air content and compressive strength in concrete prepared with different types and brands of cement conforming to the new EN 197-1 standards. The results show that significant improvements in terms of water reduction and strength development can be achieved with this new NS based product, especially when used with CEM I type cements.
{"title":"Development of a New Betanaphthaline Sulfonate-Based Superplasticizer Especially Studied for Precast Application","authors":"I. Torresan, R. Magarotto, R. Khurana","doi":"10.14359/6202","DOIUrl":"https://doi.org/10.14359/6202","url":null,"abstract":"Betanaphthalene sulfonate condensate (NS) and melamine sulfonate condensate (MS) polymers based superplasticizers have been extensively used in the Precast Industry. Continuous need for improving the performance of concrete has led to the development of products with a higher water reduction and thus higher early strength, typical of melamine based superplasticizers, but without the drawback of workability loss sometimes encountered with this kind of superplasticizers. The chemistry of the new product described in this article has been specifically designed to achieve high early and long term strength maintaining the workability typical of NS products at dosages in the range commonly used with melamines. The superior performance obtained with this new product makes it a good alternative to melamine based superplasticizers when used in precast applications. The paper reports the effect of the new B-naphthalene sulfonate based superplasticizer on water reduction, air content and compressive strength in concrete prepared with different types and brands of cement conforming to the new EN 197-1 standards. The results show that significant improvements in terms of water reduction and strength development can be achieved with this new NS based product, especially when used with CEM I type cements.","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":"84960944","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}
S. Collepardi, L. Coppola, R. Troli, M. Collepardi
Original Reactive Powder Concrete (RPC) - in form of a superplasticized cement mixture with silica fume, steel fibers and ground fine quartz was studied in comparison with a modified RPC where a graded natural aggregate (max size 8 mm) was used to replace the fine sand and/or part of the cementitious binder. Original and modified RPC were manufactured at a plastic-fluid consistency, cast by vibration and cured at three different conditions: a) room temperature; b) steam-curing at 90 C; c) high pressure steam-curing at 160C. The addition of the graded aggregate does not reduce the compressive strength provided that the quality of the cement matrix, in terms of its water-cement ratio, is not changed. This result is in contrast with the model proposed to relate to high compressive strength level of RPC (200 MPa) to the absence of coarse aggregate. Both the original and modified RPC (with coarse aggregate addition) perform better - in terms of higher strength and lower drying shrinkage or creep strain - when they are steam cured rather than cured at room temperature. This improvement was related to a more dense microstructure of the cement matrix, particularly in the RPC specimens steam cured at 160 C. The main purpose of the present investigation was to modify RPC including some coarse aggregate in the mixture and to study the influence of the coarse aggregate on the properties of cement mixtures in terms of required mixing water, compressive and flexural strength, shrinkage, swelling and creep.
{"title":"Mechanical Properties of Modified Reactive Powder Concrete","authors":"S. Collepardi, L. Coppola, R. Troli, M. Collepardi","doi":"10.14359/6175","DOIUrl":"https://doi.org/10.14359/6175","url":null,"abstract":"Original Reactive Powder Concrete (RPC) - in form of a superplasticized cement mixture with silica fume, steel fibers and ground fine quartz was studied in comparison with a modified RPC where a graded natural aggregate (max size 8 mm) was used to replace the fine sand and/or part of the cementitious binder. Original and modified RPC were manufactured at a plastic-fluid consistency, cast by vibration and cured at three different conditions: a) room temperature; b) steam-curing at 90 C; c) high pressure steam-curing at 160C. The addition of the graded aggregate does not reduce the compressive strength provided that the quality of the cement matrix, in terms of its water-cement ratio, is not changed. This result is in contrast with the model proposed to relate to high compressive strength level of RPC (200 MPa) to the absence of coarse aggregate. Both the original and modified RPC (with coarse aggregate addition) perform better - in terms of higher strength and lower drying shrinkage or creep strain - when they are steam cured rather than cured at room temperature. This improvement was related to a more dense microstructure of the cement matrix, particularly in the RPC specimens steam cured at 160 C. The main purpose of the present investigation was to modify RPC including some coarse aggregate in the mixture and to study the influence of the coarse aggregate on the properties of cement mixtures in terms of required mixing water, compressive and flexural strength, shrinkage, swelling and creep.","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":"74124813","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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