Comparison Of Different Density Materials In Lightweight Concrete

Abstract

Concrete is a highly prevalent construction material in contemporary society. The quest to reduce the weight of this material has been the focus of research that has posed a challenge to both scientists and engineers. The primary difficulty in producing a lightweight concrete lies in reducing its density while preserving its strength and without negatively impacting its cost. Adding light aggregates to the mix design is a frequently used method to reduce the density of concrete. According to BS EN 206-1, lightweight concretes are characterized by an oven dry density ranging from 800kg/m3 to 2000kg/m3. This is achieved by substituting dense natural aggregates with lightweight aggregates, either completely or partially. The materials used in this study are available locally, these includes Cement, River sand, Granite, Coconut shells (CS), Sawdust (SD), Expanded polystyrene (EPS), Master Rheobuild 858, and potable water. The mixture was prepared using a ratio of 1part cement, 1.6 parts sand, and 3.2 parts aggregate, with a water-cement ratio of 0.5. There are three different mixtures which are the conventional concrete, sawdust concrete and polystyrene concrete. The conventional aggregates were replaced with SD, CS and EPS in same ratio of 0%, 10%, 20% and 30%. Master Rheobuild 858 Plasticiser 858 was then mixed with half of the water required. The concrete's performance was evaluated based on its compressive strength and hardened density. The sample underwent testing at intervals of 7, 14, and 28 days. The compressive strength of the control sample (C0) at 28 days was 34.8 N/mm2, which successfully met the desired goal strength. Additionally, the density of the sample was measured to be 2447 kg/m3. S10, S20, and S30 exhibit compressive strengths and densities of 28 N/mm2 and 2198 kg/m3, 24 N/mm2 and 2081 kg/m3, and 18.4 N/mm2 and 1980 kg/m3, respectively, after 28 days. E10, E20, and E30 have compressive strengths and densities of 25 N/mm2 and 1884 kg/m3, 18 N/mm2 and 1752 kg/m3, and 12N/mm2 and 1653 kg/m3, respectively. The study determined that there is a reduction in both compressive strength and density. Nevertheless, given the circumstances, as the replacement material increased, both the strength and density also reduced. Lightweight concrete was achieved with 10% of EPS at 1884 kg/m3. This resulted in strength of 25 N/mm2, making it appropriate for M25 concrete. While it was achieved with 30% of SD and CS which has a density of 1980 kg/m3 and strength of 18.4 N/mm2. Hydrophobic compounds can be included into sawdust to mitigate its high water absorption rate.