Compressive Strength behaviour of Recycled Aggregate Concrete

Abstract

This study explores the compressive strength of Recycled Aggregate Concrete (RAC) using Recycled Coarse Aggregate (RCA) as a partial substitute for Natural Coarse Aggregate (NCA). Four mixes were tested with RCA replacement levels of 0%, 15%, 20%, and 25%. The research involved two stages: Stage I focused on early-age compressive strength (3 days) to find the optimal replacement ratio, while Stage II assessed long-term strength at 7, 14, and 28 days. Results indicated that compressive strength declined with higher RCA content due to increased porosity, but strength reduction was minimal up to 20% replacement. The 20% RCA mix achieved about 95% of the strength of natural aggregate concrete at 28 days, confirming its structural adequacy.

Microstructural analyses supported that 20% RCA provides a good balance of sustainability, cost-effectiveness, and structural integrity.