Effect of Sand Replacement and Silica Fume Addition on Chloride Ion Permeability of Lightweight Concrete

This paper was conducted to study the behavior of lightweight concrete, incorporating local lightweight aggregate (LWA), in terms of chloride ion permeability at different ages. The effect of lightweight fine aggregate replacement by normal weight sand (0, 25, 50 and 75% by volume) was investigated. Constant level of silica fume content (10% by weight of cement) as an addition was also considered. Although results showed that the use of porous lightweight aggregate did not lower the permeability of lightweight concrete, test results indicated a decrease in chloride ion permeability as a result of increasing sand replacement for all types of mixes up to 360 days. The reduction in chloride ion permeability was attributed to the presence of the sand which appeared to decrease the porosity of LWC, the reduction in the chloride diffusion coefficient was observed to be as much as 50%. Moreover, the addition of silica fume caused further reductions in chloride ion permeability due to the progression in maturity of LWC, especially after one year of continuous hydration.