Effect of air entraining and pumice on properties of ultra-high performance lightweight concrete

This study focuses on developing the production of ultra-high-performance lightweight concrete (UHPLC) by combining pumice with an air-entraining agent. Air-entraining agents of aluminum powder (AP) and lightcrete (LC) were added in amounts of 0.1, 0.2, 0.3, 0.4, and 0.5% by weight of cement to create air bubbles. Crushed pumice has also been used as a partial sand replacement in proportions of 25% and 50% by volume, with or without the addition of AP or LC. To investigate the fresh, mechanical, and microstructural properties, seventeen UHPLC combinations were constructed. A slump flow diameter test was conducted to evaluate the characteristics of fresh UHPLC, and mechanical properties were evaluated by completing dry density, compressive strength, tensile strength, flexural strength, modulus of elasticity, and dry shrinkage tests. The effect of high temperatures of 20, 400, 600, and 800 degrees C on compressive strength was also investigated. The microstructure characteristics were analyzed using a scanning electron microscope. The research concluded that high-performance concrete with a compressive strength of 127.6 MPa and a dry density of 1970 kg/m3 could be produced after a 28-day age test. This was accomplished by including 0.1% LC by weight of cement and 25% pumice as a partial substitute for sand. The mixture with 50% pumice as a partial replacement for sand and the addition of 0.5% LC of the cement weight exhibited the least loss in compressive strength when subjected to high temperatures.