Viability of agricultural wastes as substitute of natural aggregate in concrete: A review on the durability-related properties

Abstract

Increase in construction activities has led to rapid depletion of natural resources, particularly aggregates which are utilized in the production of concrete. At the same time, there are huge amount of solid wastes originating from the agricultural industry, particularly from the South East Asia region, such as oil palm shell (OPS), oil palm boiler clinker (OPBC) and coconut shell. Research have since been undertaken to investigate the feasibility of these waste materials as potential substitute for conventional aggregate in concrete. Durability of concretes, especially those containing recycled waste materials are often subjected to scrutiny. Therefore, this paper reviews the published findings on the durability-related properties of concrete containing these agricultural waste materials as aggregate. Due to improved binder quality (lower w/b ratio and higher binder content), concrete prepared with these wastes generally exhibit acceptable quality in terms of water absorption, sorptivity and chloride penetrability. The major drawbacks are associated with the higher drying shrinkage, susceptibility towards severe chemical attack and elevated temperature. Among these wastes, OPBC aggregate is considered to have the best performance based on the reviewed properties, while OPS aggregate and coconut shell aggregate are recommended to be used only as partial aggregate replacement. Current available studies, however, are still insufficient and more in-depth investigations are required to ascertain the suitability of these wastes to be re-used as aggregate replacement in concrete.