Effect of using waste sludge as partial cement replacement on compressive strength and water absorption of high strength concrete

Abstract

This study focuses on evaluating a utilization of waste sludge from Thu Duc water supply plant on the engineering properties of high strength concrete, including slump, compressive strength, water absorption, and void volume. The replacements of cement by waste sludge used in the study were 0%, 5%, 10%, 15%, and 20% by mass. The objectives were to manufacture control concrete using no waste sludge with a designed compressive strength at 28 days of 70 MPa and to maintain a designed slump of 14 ± 2 cm for all mixture proportions. The experimental results showed that the compressive strength at 28 days of the control concrete reached the designed strength, while the concrete with sludge replacements of 5%, 10%, and 15% had compressive strength higher than 60 MPa, meeting a specification of high strength concrete. The higher the waste sludge replacement, the higher the water absorption and void volume of the concrete. The compressive strength of concrete was inversely proportional to the water absorption and the void volume at 28 days.