High-Strength Concrete Using Recycled Aggregate Through Carbonation Treatment.

Abstract

This research aims to investigate the compressive strength, modulus of elasticity and drying shrinkage of high-strength concrete using cement and fly ash as a binder at a ratio of 75:25 by weigh. Natural coarse aggregate (NCA) was replaced by recycled coarse aggregate (RCA) which improved its physical properties by carbonation process. There were 3 ways to enhance RCA as follows: 1.) recycled coarse aggregate was directly cured by  (RC), 2.) recycled coarse aggregate was soaked in calcium carbide solution and then cured with  (RCC), and 3.) recycled coarse aggregate was soaked in calcium carbide solution mixed with fly ash and cured with (RCCF). Aggregates from these methods were cured with  at the ages of 1, 3 and 7 days. RCA having the best physical properties from each method was used as a coarse aggregate in the concrete. The results showed that the three methods had potential for improving RCA from  curing period of 1 day whereas the curing period of 7 days exhibited the best physical properties. It is noted that RCCF method was the best process to enhance properties of RCA. The compressive strength of concrete containing treated RCA (RC, RCC and RCCF methods) at 28 days was higher than that of concrete containing untreated RCA by 6, 12 and 14% and the elastic modulus was increased by 2, 5, and 9%, respectively. Additionally, the drying shrinkage of concrete was reduced with the use of carbonation-enhanced RCA aggregates.