Mechanical and durability properties of recycled and repeated recycled coarse aggregate concrete

Abstract

Disposal and treatment of construction and demolition (C&D) wastes are often costly and hazardous to the environment. Their recycling could lead to a greener solution to the environmental conservation and pave the way towards sustainability. This study utilizes demolished concrete as coarse aggregate often termed as recycled coarse aggregate (RCA) for producing industry quality concrete. Large scale recycling can substantially reduce the consumption of natural aggregate and help preserve the environment. However, in near future, it can raise new challenges. The use of “repeated recycled coarse aggregate” in concrete production can be a viable solution to the growing problem regarding the C&D waste disposal. During the development of new generation product like recycled and repeated recycled coarse aggregate concrete, it is essential to investigate the fresh, hardened, and durability properties of concrete to promote and escalate its application in the construction industry. This research investigates the fresh, mechanical, and durability properties of 25 MPa recycled aggregate concrete (RAC) made with different RCA replacement levels. Durability performance of 25 MPa RAC was evaluated in terms of sulphate attack and cyclic wetting and drying along with chloride exposure. Chloride propagation was evaluated after 1, 4, 9, 16, 28, 90, and 120 cycles. This study reveals that the performance of RAC is decreasing with increasing RCA replacement levels but their overall performance is comparable to natural aggregate concrete (NAC). Three different generations of repeated recycled coarse aggregate concrete were produced using 100% RCA as a replacement of natural coarse aggregate. Similar mix design was used for producing 32 MPa concrete. Along with this, their durability performance was examined under three different exposure conditions namely, freeze-thaw, sulphate, and chloride exposure. It was found that the compressive strength of different generations of repeated recycled concrete was lower than the control concrete. However, all of the mixes exceeded the target strength at 120 days. The durability performance of the different generations of repeated recycled coarse aggregate concrete was negatively affected by using different generations of such aggregates but still these findings will add a new achievement towards sustainable world.