SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete最新文献_第5页

Protection of Reinforcements from Chloride Attack by the Use of Galvanized Steel and Calcium Nitrite 镀锌钢和亚硝酸钙对增强材料抗氯化物侵蚀的保护

SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete Pub Date : 1997-09-01 DOI: 10.14359/6181

C. Alonso, G. Sinibaldi, C. Andrade, R. Cigna

引用次数: 2

A Lithium-Based Admixture for ASR Control that Does Not Increase the Pore Solution pH 一种不增加孔隙溶液pH值的用于ASR控制的锂基添加剂

SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete Pub Date : 1997-09-01 DOI: 10.14359/6216

D. Stokes, H. H. Wang, S. Diamond

引用次数: 17

New Admixtures for Eliminating Steam Curing and its Negative Effects on Durability 消除蒸汽固化及其对耐久性的负面影响的新型外加剂

SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete Pub Date : 1997-09-01 DOI: 10.14359/6179

R. Khurana, I. Torresan

{"title":"New Admixtures for Eliminating Steam Curing and its Negative Effects on Durability","authors":"R. Khurana, I. Torresan","doi":"10.14359/6179","DOIUrl":"https://doi.org/10.14359/6179","url":null,"abstract":"Heat curing is the most common method used for accelerating the strength development in concrete. Accelerated curing finds large applications in the precast industry for quick turnaround of forms and casting beds. The increase in the initial strengths is simply a result of increased rate of hydration caused by higher temperature. However, later strengths are often lower than those of the same concrete cured at 20C. The causes of the strength loss are of physical and chemical nature. The physical cause results in increased porosity and cracking because the concrete constituents have different thermal expansion, (air has the highest). The chemical causes are the differences in the hydration products, microstructure and degree of hydration. Generally, physical causes are the dominating factors for strength loss in hear cured concrete. Results of extensive laboratory and field tests are presented showing that equivalent compressive strengths at 18 hours are obtained with concrete containing the new generation superplasticizers and heat cured concretes at 60C. The 28 day strengths of concretes with admixtures are substantially higher. Thus, with the use of these new generation superplasticizers it's possible to overcome the negative effects of steam curing such as strength loss, permeability, shrinkage, creep and frost resistance.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":"90 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82791075","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}

引用次数: 8

Influence of Lignosulphonate Molecular Weight Fractions on the Properties of Fresh Cement 木质素磺酸钠分子量分数对鲜水泥性能的影响

SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete Pub Date : 1997-09-01 DOI: 10.14359/6213

J. Zhor, T. Bremmer

{"title":"Influence of Lignosulphonate Molecular Weight Fractions on the Properties of Fresh Cement","authors":"J. Zhor, T. Bremmer","doi":"10.14359/6213","DOIUrl":"https://doi.org/10.14359/6213","url":null,"abstract":"The importance of molecular weight as a parameter influencing the performance of water-reducing admixture in cement paste was investigated. The sulphomethylolated 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 1, 10 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 fluidification and lowest air-entrainment were observed when the intermediate 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":"89 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81491113","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}

引用次数: 2

Development of an Admixture for Self-Leveling Concrete 自流平混凝土掺合料的研制

SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete Pub Date : 1997-09-01 DOI: 10.14359/6199

S. Rols, J. Ambroise, J. Pera

{"title":"Development of an Admixture for Self-Leveling Concrete","authors":"S. Rols, J. Ambroise, J. Pera","doi":"10.14359/6199","DOIUrl":"https://doi.org/10.14359/6199","url":null,"abstract":"In the past decade, many efforts have been undertaken to develop highly-workable concrete which consolidates under its own weight without any vibration, specially in Japan. The admixtures used in such concrete are mainly composed of high water reducing superplasticizers, fine limestone dust and viscosity agents to maintain not only high flowability but high segregation resistance of the concrete. The water to cement ratio is generally lower than 0.55. A new admixture is proposed in the present study. It is a mixture of a superplasticizer and an accelerator with plasticizing properties which also acts as a viscosity agent. The composition of the self-leveling concrete is as follows. The total amount of fine materials (cement + fly ash or cement + ground limestone) is 370kg/m^3, while the cement content (normal portland cement CEMI 52.5) is 260kg/m^3. The water to cement ratio is 0.73. The mechanical performances of the hardened concrete is better than those of a usual French building concrete. The compressive strengths at 16 hrs, 7 days, and 28 days are 8, 30, and 3 MPa, respectively. The unrestrained drying shrinkage reaches 600 to 700mm/m, at 90 days as predicted from the 28 day results.","PeriodicalId":21898,"journal":{"name":"SP-173: Fifth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88372432","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}

引用次数: 7