Effect of Sodium-Silicate Treatment for Recycled Concrete Aggregate on Slump and Compressive Strength of Concrete

Abstract

The aim of the present study was to investigate effect of sodium-silicate treatment for recycled concrete aggregate (RCA) on slump and compressive strength of concretes. Replacements of crushed stone as coarse aggregate by RCA were 0, 25, and 50% by volume. RCA was treated by immersing in solution consisting of 50% sodium silicate and 50% tap water for 1 h to improve its properties. After immersion, the surface of treated RCA was dried in air before making concrete. Concrete with untreated RCA was also prepared for comparison. Results showed that the higher the RCA replacement, the lower the slump and compressive strength at 3 and 7 days of concretes regardless of the sodium-silicate treatment. With the same water content, the concrete with treated RCA had the higher slump and lower compressive strength at 3 and 7 days when compared with the concrete with untreated RCA. Gain in 30-day compressive strength compared with 3-day compressive strength of the concretes with untreated and treated RCA was more significant than that of the concrete without RCA. Consequently, this treatment reduced water absorption of RCA, resulting in an increase in slump of fresh concrete and a decrease in compressive strength at early ages of hardened concrete.