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Abstract: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 behavior 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 articleThey also have a strong
capability of optimizing the physical and chemical behavior of cement produced
in the Najran cement industry. |