Effect of Saturated Lightweight Sand Substitution on Shrinkage in 0.35 w/b Concrete

Abstract

This paper evaluates the effectiveness of internal curing as a method to mitigate autogenous shrinkage in high-performance concrete (HPC) having a low water binder ratio (w/b). To achieve this, the author substitutes 20% of normalweight (NW) sand by an equal mass of lightweight sand (LW) in HPC having a w/b of 0.35. Shrinkage is monitored using vibrating wire gauges cast at the center of 100 x 100 x 400 mm (4 x 4 x 16 in.) concrete samples. Results show that a 20% substitution of NW by a LW sand efficiently reduces autogenous and drying shrinkage. Moreover, the incorporation of 20% LW sand does not have a significant effect on 28-day compressive strength. Results also show low chloride ion permeability in the cementitious matrix. The author concludes that internal curing using partial replacement of NW sand by LW sand presents an efficient way to reduce autogenous and drying shrinkage in low w/b concretes, especially in cases where external water curing disallows in-depth curing of concrete.