FLUIDITY AND WORKABILITY STUDY OF CEMENT(OPC) AND SUPER-PLASTICIZER

Abstract

Concrete incorporates a mixture of chemical and mineral admixtures in present scenario. Chemical admixtures are materials available in the form of powders or fluids that are added to concrete to give certain characteristics not obtainable with ordinary concrete mixes. An admixture‟s performance is dependent on its type and dosage, composition, specific surface area of the cement, type and proportions of the aggregate, sequence of addition of water and admixture, compatibility of admixtures, water/cement ratio, and temperature and conditions of curing. Requirement of right workability is the essence of good concrete and concrete in different situations require different degree of workability. High range water reducers referred as super plasticizers help in obtaining higher workability without use of excess water. It is very difficult to ensure that a super-plasticizer that produces all the desired effects with cement of one type and brand would do the same with cement of other type and brand. Incompatibility may exist due to different types of cement or due to different brands of cement. Users, who are unaware of compatibility issues, often suffer when the supply of cement and/or super-plasticizer is changed. In the Present work we find the optimum doses of super-plasticizers for different brands of cement (OPC 43 grade) available in the market at different water cement ratio using Marsh Cone to adjudge best combination of cement and super-plasticizer and found that different Super-plasticizers give different optimum dose with different brand of ordinary Portland cement. Also, slump retention characteristics of concrete is of great importance as workability is lost with the passage of time and the efforts are made to retain the slump with time so that concrete remains workable for long time. Slump retention depends on both, type of cement and type of super-plasticizer. So the current work is carried out to ascertain the water reduction by different combination of cement and super-plasticizer at which slump loss is minimal.