Effect of Mineral and Chemical Admixtures on the heat of hydration of Najran blended cement pastes

Objectives: This study is to investigate the influence of mineral and chemical admixtures on the hydration of cement pastes by a replacement process of 30%. Methods: Cement pastes are made in accordance with ASTM C192M. the samples were kept at a constant room temperature of 2.5 °C until reached ambient temperature, the hydration behaviour of blended cement pastes was studied at different temperatures ranging from 30 to 90°C and at constant water/solid ratios of 0.4 using an isothermal conduction calorimeter. A specific gravity 3.15, and special surface area of 410 m2/kg. Silica fume with a specific gravity of 2.20 and special surface area of 22.500 m2 /kg was employed. Fly ash with a surface area of 2900 cm2/gm and specific gravity of 2.2 were measured. Findings: The results show a high intensity of the main peaks with a lower hydration temperature range between 30°C and 40°C. In contrast, at different temperatures (60°C and 90°C), it was shown the quantity of hydration decreased. The cumulative heat of hydration of blended cement paste is reduced with an increase of mineral and chemical admixtures. The activation energy Ea obtained at different temperatures of 30,40,50, 60,80 for mineral admixtures and chemical admixtures was 69.4, 57.67, 100, 87, and 66.23, respectively, and 0.65, 0.51, 0.45, 1.00, 0,90. Novelty: The performance of each material employed in cementitious composites, both chemically and minerally, admixtures affects the composites' fresh and hardened qualities. Nevertheless, very few studies have looked at the performance of mineral and chemical admixtures. As a low-cost substitute for commercial admixtures, the results obtained by both chemical and mineral admixtures give us the following completely new points in this article They also have a strong capability of optimizing the physical and chemical behaviour of cement produced in the Najran cement industry.