INFRA-LIGHTWEIGHT CONCRETE: A COMPREHENSIVE REVIEW OF STRUCTURAL AND THERMAL PERFORMANCE WITH SUSTAINABLE AGGREGATES

With the increasing concern on the issue of climate change and the increasing energy consumption within the built environment, there is the increasing need to come up with building materials that not only meet the structural requirement but also the thermal performance of the built environment. The conventional concrete, though effective structurally, has a poor thermal conductivity and thus, it consumes a lot of energy and gives discomfort especially where the ambient temperatures are very hot. Infra-lightweight concrete (ILC) is a fledgling trend in the field of sustainable building, with decreased density and better thermal insulation capacity and still possess adequate mechanical strength to be utilized as a structural material. In this review, the recent advances in ILC are thoroughly discussed with a focus on the utilization of sustainable and waste-based aggregates including palm kernel shells (PKS) and expanded polystyrene (EPS). The paper will analyze the two performance parameters of ILC involving thermal conductivity and compressive strength and the effects of their determination by the type of aggregate used, binder content, and mix design. As has been shown by previous studies, the incorporation of lightweight materials tends to decrease the strength, but with proper mix optimization, it is possible to obtain concrete with a fair structural performance and improved insulation capacity. Specifically, PKS and EPS which are agricultural and industrial by-products have potential promising low-cost and greener alternatives to traditional aggregates. Concrete incorporating PKS have demonstrated thermal conductivity values as low as 0.19 W/mK and 6MPa to 26 MPa compressive strength depending on the particle size and replacement level while concrete incorporating EPS have achieved densities as low as 300 kg/m³, thermal conductivity as low as 0.12-0.6 W/mK, and compressive strengths of 10MPa to 36 MPa at optimum replacement levels. The possible potential of ILC in fulfilling the structural requirements and energy-efficiency in contemporary buildings, particularly in hot climates, are also presented in this review. The gaps in the current studies are outlined, such as long-term durability research, optimization of mix design to use it in large amounts, and the usage of ILC in whole building energy modeling. It will be concluded that the paper has highlighted the future research directions in respect to the larger implementation of ILC as a multipurpose building substance in the environmentally friendly constructions.