Examining The Mechanical and Durability Properties of Concrete Containing Recycled Fine Aggregates Possessing Different Contamination Levels

Abstract

Three types of recycled fine aggregates (RFA) possessing different contamination levels (washed – unwashed) were used in the present study. RFAs were used instead of natural fine aggregate (NFA) at the concentrations of 10%, 20%, 40%, and 80%. No significant negative characteristics were observed in green and hardened characteristics of concrete when using RFA at up to 80% concentration. However, using less-washed or unwashed RFA at 10% or 20% concentration is generally appropriate. The use of less-washed or unwashed RFAs at the concentration of 40% or more negatively affects the slump values of concrete. Especially the use of unwashed RFA at 80% concentration yielded more significant damages. The non-hydrated cement particles in the RFA show insemination or hardening acceleration behavior and affected the 7-day pressure strength of concrete at a higher level. However, together with the use of RA having a weak interface transition zone, the splitting tensile strength values of concretes more significantly decreased. In conclusion, it was determined that RFAs can be used up to 80% concentration after an appropriate washing procedure. From the aspect of costs, in order to prevent durability problems, it should not be used at any concentration higher than 20% without a washing procedure. From the aspect of protecting the sustainable environment and natural sources, it is very important to increase the use of RFAs in concrete production.