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

This paper was conducted to study the behavior oflightweight concrete, incorporating local lightweight aggregate(LWA), in terms of chloride ion permeability at different ages. Theeffect of lightweight fine aggregate replacement by normal weightsand (0, 25, 50 and 75% by volume) was investigated. Constant levelof silica fume content (10% by weight of cement) as an addition wasalso considered. Although results showed that the use of porouslightweight aggregate did not lower the permeability of lightweightconcrete, test results indicated a decrease in chloride ion permeabilityas a result of increasing sand replacement for all types of mixes up to360 days. The reduction in chloride ion permeability was attributed tothe presence of the sand which appeared to decrease the porosity ofLWC, the reduction in the chloride diffusion coefficient was observedto be as much as 50%. Moreover, the addition of silica fume causedfurther reductions in chloride ion permeability due to the progressionin maturity of LWC, especially after one year of continuous hydration.