Effect of Plasticizer on Workability and Compressive Strength of Recycled Coarse Aggregate Concrete

Abstract

The construction industry faces critical challenges concerning the depletion of natural aggregate resources and the escalating volume of construction and demolition waste. This research investigates the effect of Sikament 512 PKM plasticizer dosage on the compressive strength and workability of recycled coarse aggregate concrete. Four concrete mixtures were prepared with plasticizer dosages of 0%, 1%, 3%, and 5% by weight of water, with a constant mix proportion of 1:1.5:3. Workability was evaluated using slump tests, and compressive strength was determined at 7, 14, and 28 days. The results demonstrated that 1% plasticizer dosage provided optimal performance, achieving a slump of 74 mm and a 28-day compressive strength of 30.70 MPa, representing an 11.1% improvement over the conventional concrete. Higher dosages of 3% and 5% caused segregation and bleeding, with slump values reaching 120 mm and 175 mm, respectively, and compressive strengths decreased by 1.2% and 18.9%, respectively. The enhanced performance at 1% dosage is attributed to effective dispersion of cement particles and a 10% reduction in water, which lowered the effective water-to-cement ratio from 0.59 to 0.53. This study establishes that an optimized plasticizer dosage is essential for achieving adequate workability and superior compressive strength in recycled aggregate concrete, thereby supporting sustainable construction practices by effectively utilizing demolished concrete waste.