High-Temperature and Acid Resistance of Concrete with Recycled, Desert Sand, and Crumb Rubber Blends

Natural sand extraction for concrete manufacturing is a global issue for ecological balance and environmental concerns. This study introduced three mixes with three newly developed sand types to replace natural sand in concrete manufacturing. Additionally, three more mixes were made by incorporating optimized 10% silica fume. The durability of the prepared mixes was evaluated at high temperatures of (150-750 °C) at the interval of 150 °C and against immersion in a 5% sulfuric acid solution for 28, 56, 91, and 182 days, respectively. The study's results reported the stability of the samples up to 300 °C, and then the fall of the samples started at 450 °C. Severe damage in the samples was formed at about 600 °C, and finally, a total collapse was seen at 750 °C. From (150 to 750 °C), the mix TYPE-3SSFC with a sustainable sand combination (50% recycled sand + 45% desert sand + 5% crumb rubber) and 10% silica fume showed better resistance than the other mixes. The compressive strength in the mix TYPE-3SSFC was 20.6%, 16.3%, 14.7%, 21.3%, 26.5%, and 43.2% higher than the mix TYPE-3SC with 10% silica fume. The mix TYPE-3SSFC with optimized 10% silica fume content showed better resistance against 5% sulfuric acid solution than those without silica fume. By morphological analysis, the mix TYPE-3SSFC showed that the interface improved due to the dense interconnectivity of the concrete mix between the crumb rubber paste and silica fume content. A dense calcite crystal was also seen in the mixture, which confirmed the study's results. The mix with TYPE 2-Sand (100% recycled sand) revealed inferior results, low stability, and high damage. Thus, 100% recycled sand is not recommended for structural concrete.