Experimental Comparative Study of Effect of Different Additive Materials on Concrete Mix Alkalinity and Heat Generation

Abstract

There are different methods to minimize the evolution of heat in concrete. Since the cement is the main component that generates heat, the first procedure may be to reduce its quantities by replacing cement with fine materials that do not release heat during its reaction. This paper studies the influence of different additives (fly ash, silica fume, and metakaolin) to the concrete mixture with different ratios of (0, 5, 10, 15, 20, 25, 30%) by weight of cement, with different parameters study, were presented, including impact of additives on (compressive strength, alkalinity, heat of hydration with fixed w/c ratio of 0.35, initial setting time, final setting time and impact of w/c ratio on heat of hydration with three w/c ratio of (0.3, 0.35 and 0.4)). The water cementations materials ratio was kept steady at (0.35). The heat of hydration measurement was carried out under isothermal constrain(25±0.1C°). Thermocouples were utilized to evaluate the heat of hydration of concrete by stating time from 0 to 24 hours and measured by a thermoelectric device. Concrete cubes with dimensions 100×100×100 mm for compressive strength test were used and examined at the time of 28 days, using different mix proportions resulted from different percentages of cement additives, to perform the compressive strength test. The results revealed that the Portland cement heat of hydration is retarded in the presence of additives. The decrease in pH of the concrete mix before casting and molding affects the early hydration and strength but improves the later age concrete properties.

Studying the usability of recycled aggregate to produce new concrete

“…MRCA(0) represents the control mix, while the other mixes reflect MRCA with varying percentages of recycled coarse aggregate. These percentages include 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100, which are used to replace the coarse aggregate [36][37][38]. The water quantity and water-to-cement ratios were consistent across all concrete mixtures.…”