Abstract:
An experimental study was conducted to understand the influence of some factors on workability and compressive strength of ready mix concrete (RMC). To conduct this study, different types of plasticizers and superplasticizers were collected from local market. Sylhet sand and boulder crushed stone chips were used as fine and coarse aggregates respectively. According to ASTM specification the test was conducted. Different concrete mixtures with different chemical admixtures and sand to total aggregate volume ratios were investigated. Slump test was carried out at 15 minutes interval till the slump is less than or equal to 3 cm after mixing of concrete. For measurement of workability in two stage admixture dosage, the second stage of admixture was added to the concrete when the slump was equal or less than 3 cm. After that the casting was done. Curing of the concrete specimen was done in two steps; primary curing and final curing. Cylindrical concrete specimens of 4 inch diameter and 8 inch in height were made to measure compressive strength at 7 days and 28 days. From the test results, it was found that plasticizers impart more compressive strength to concrete than most of the superplasticizers. However, superplasticizers give more workability than plasticizers. Concrete made with high range water reducing superplasticizer attains more strength than concrete made with retarding superplasticizer. But, retarding superplasticizers impart more workability to concrete. In this test w/c ratio was kept constant. There was variations in s/a ratio, cement content and admixture dosage. It was found that two stage dosage of admixture provide better and long-time workability. It is also found that with the increase of s/a ratio the workability of concrete decreases and with the increase of cement content the workability increases. Also the strength of the concrete increased with the addition of some of the chemical admixture compared to without admixture specimen.
Description:
Supervised by
Dr. Md. Tarek Uddin, PEng.
Professor and Head, Department of Civil and Environmental Engineering (CEE)
Islamic University of Technology (IUT)
Board Bazar, Gazipur, Bangladesh.
