The Effect of Admixtures on Concrete Properties

In this study super plasticizers admixtures were used for the three grades of concrete 15, 25 and 40N/mm2 to improve the properties of fresh and harden concrete in hot weather to achieve these properties in the summer season of Sudan: − Increase the workability − Increase the compressive strength by adoption super plasticizers admixtures which increase the workability and hence the strength is increased through the reduction of water content. − Reduce the cement content and hence cost saving. The experimental work was divided into two phases: 1. Tests on basic materials (cement, aggregate, sand, water) and the effect of recommended dose of admixture on the properties of fresh and hardened concrete. The results of tests for the basic materials were carried to ensure that their results conforming to their standards and can be used. 2. Concrete testing program for the three grades which contain four mixes for each grade. − Ordinary reference mix − Same mix with admixture to increase strength − Same mix with admixture to reduce water content and hence increase strength. − Same mix with admixture to reduce the cement content keeping same workability and strength. The results of the second phase for the three grades indicate that admixtures can be used to: − Increase the workability of the concrete for the three grades by: Slump from 55 to 160 for grade 15. Slump from 60 to 200 for grade 25. Slump from 60 to 160 for grade 40. − Increase the compressive strength of the three grades at 28 days by: (28 – 33)% for grade15. (32 – 55)% for grade 25. (19 – 28)% for grade 40. − Reduce the cement content by 23% compared with reference mixes without reducing the compressive strength and keeping same (w/c)