Effect of Self-Curing Admixture and Sand Type on the Mechanical and Microstructural Properties of Concrete in Hot Climate Conditions

The performance of concrete in hot and arid regions, where summer temperatures typically range between 40 and 50℃, is critically affected by the rapid evaporation of mix water. This study systematically investigates the influence of elevated temperatures characteristic of these climates on both the fresh and hardened properties of concrete, with a focus on formulation variables. Three distinct sand types—calcareous, silico-calcareous, and siliceous—were utilized in conjunction with superplasticizers and curing agents to discern their effects under simulated hot weather conditions. These conditions replicated an ambient temperature of 50℃ for dry materials and water, a wind speed of 12 km/h, and a relative humidity of 10%, to emulate the average shaded environment in desert regions. Workability and compressive strength were evaluated, alongside a microstructural analysis conducted via Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). It was observed that mixtures containing siliceous or silico-calcareous sands exhibited enhanced fluidity, while those with calcareous sand demonstrated superior compressive strength. Microstructural examinations revealed a denser matrix in the calcareous sand-based concrete when compared to its counterparts. Notably, the incorporation of curing compounds and superplasticizers was found to augment the compressive strength, particularly in calcareous sand mixtures, under hot weather conditions. This research offers critical insights into optimizing concrete formulations to mitigate the adverse effects of hot weather concreting, providing a valuable resource for concrete technologists in similar climatic zones.