Influence of fly ash as a partial cement substitution on properties of high-strength concrete

Abstract

This study evaluates the possibility of using fly ash, a by-product of coal thermal power plants, in the production of high-strength concrete. The influence of fly ash as a partial cement substitution (by 0 – 50 % with an interval of 10 %) on the engineering properties of the high-strength concrete was investigated through a test series of workability, dry density, compressive strength, water absorption, drying shrinkage, and ultrasonic pulse velocity. The experimental results show that the workability of fresh concrete mixture and water absorption of concrete samples increased as increasing fly ash content in the mixtures. Meanwhile, compressive strength and ultrasonic pulse velocity were reduced with increasing fly ash replacement levels. The replacement of cement with fly ash was effective in reducing dry density and drying shrinkage of hardened concrete. The concrete samples produced in this study achieved good quality and durability with ultrasonic pulse velocity values of above 4570 m/s. The test results also reveal that fly ash could be used to replace up to 40 % of cement in the production of high-strength concrete with compressive strength value at 28 days of ≥ 55 MPa.