Influence of heavyweight aggregate on the fresh, mechanical, durability, and microstructural properties of self-compacting concrete under elevated temperatures

Abstract

Recently, attention has been drawn to the production of heavyweight self-compacting concrete which combines the benefits of heavyweight concrete (HWC) and self-compacting concrete (SCC). This paper investigates the effect of using the barite coarse aggregate (size 4–8 mm) as substitution of volume of the natural coarse aggregate (size 4–8 mm) with various percentages (0, 20, 40, 60, 80, and 100%) on self-compacting concrete (SCC) properties. Slump-flow, T500 time, V-funnel, J-ring, L-box test, and fresh density were used to evaluate the fresh SCC characteristics. However, compressive strength, flexural strength, splitting tensile strength, water absorption, dry density, sulphate attack, and ultrasonic pulse velocity were used to evaluate the mechanical and durability characteristics. In addition, the impact of elevated temperatures (600 °C and 800 °C) on SCC containing various ratios of barite was studied through the evaluation of the density and compressive strength losses. Also, using fourier transform infrared radiation (FTIR) technique, mercury intrusion porosimetry (MIP), and scanning electron microscope (SEM), a microstructural investigation was conducted on hardened SCC containing various ratios of barite to determine the behaviour of barite in comparison to the control mix. The results demonstrate a slight negative effect on fresh and hardened of SCC properties with increasing percentages of barite. However, concrete incorporating up to 80% barite fulfilled all of the EFNARC-recommended criteria for SCC and the dry density of samples containing 80% barite was 2.660 kg/m3. Therefore, the self-compacting and heavyweight concrete characteristics were met by incorporating 80% barite as coarse aggregates. Nevertheless, the rate of increment in compressive strength increased with increasing barite ratios after exposure to 15 cycles of sulphate attack compared to the non-exposed samples.