Effect of curing and mix design parameters on durability of Portland cement and Portland cement-silica fume mortars in a hot-marine environment
This study was conducted to evaluate the effect of curing and mix design parameters, such as cement content and water to cementitious materials ratio, on the strength and durability characteristics of plain and silica fume cements exposed to a hot-marine environment. Specifically, the effect of curing and mix design parameters on chloride diffusion, shrinkage and carbonation of cement mortar specimens exposed to a hot-marine environment was evaluated. The results indicated that high water to cement ratio significantly influenced the durability performance of concrete through: (1) accelerating chloride diffusion and carbonation, (2) increasing the shrinkage and weight loss, and (3) reducing the compressive strength. Similarly, increasing the cement content increased the shrinkage for a given w/c ratio. However, the chloride diffusion and carbonation were minimized and strength was enhanced due to increasing cement content. The mix design parameters, namely, water-cement ratio and cement content significantly influenced the performance of both Type I and Type V cements, while the influence of these parameters on the performance of silica fume cements was insignificant. Although Type I cement mortars performed better than Type V cement mortars, the performance of silica fume cement was the best in terms of reduced chloride diffusion, carbonation and shrinkage, and enhanced strength. The beneficial effects of silica fume cements, were however, only evident in specimens subjected to good curing. Therefore, to extend the useful service-life of reinforced concrete structures exposed to hot-marine environments, the following mix design is recommended: (i) cement content should not be less than 350kg/m3; (ii) Type I cement with 10% silica fume; (iii) water to cementitious materials ratio of not more than 0.45; (iv) good curing.