Oil-palm by-products as lightweight aggregate in concrete mixture: a review

The use of industrial waste as a construction material to build environmentally sustainable structures has several practical and economic advantages. Oil-palm-boiler clinker is a waste material obtained by burning off solid wastes during the process of palm oil extraction. The research performed over the last two decades concerning the use of oil-palm-boiler clinker as a lightweight aggregate to produce structural lightweight aggregate concrete is summarized in this paper. The physical, chemical and mechanical properties of oil-palm-boiler clinker aggregate and the mechanical properties and structural performance of oil-palm-boiler clinker concrete are addressed, discussed, and compared with normal weight concrete. The review of the literature showed that depending on the source of oil-palm-boiler clinker the specific gravity of this aggregate is 15-35% less than normal weight aggregates and it can be used as a lightweight aggregate for making structural lightweight aggregate concrete. Concretes containing oil-palm-boiler clinker as coarse and fine aggregates have the 28-day compressive strength in the range of 17-47 MPa, with a density in the range of 1440-1850 kg/m3. While, concretes containing oil-palm-boiler clinker as coarse aggregate and normal sand as fine aggregate have the 28-day compressive strength in the range of 15-35 MPa with a density in the range of 1800-2000 kg/m3. Partial replacement of oil palm shell with oil-palm-boiler clinker in oil palm shell lightweight concrete could significantly improve (about 40%) the compressive strength of the concrete. The research gaps are also identified in this study to explore the innovative lightweight concrete based on the financial and environmental design factors.