Influence of composition and curing on drying shrinkage of aerated concrete

The process of drying of many materials is accompanied by dimensional changes, which induce cracks in the structure. This phenomenon is particularly significant in aerated concrete owing to its high total porosity and specific surface of pores. The factors influencing drying shrinkage of aerated concrete are widely different from that of normal concrete because of the presence of coarse aggregates in the latter. This paper discusses the results of statistically designed experiments conducted to ascertain the influence of composition on the drying shrinkage of non-autoclaved and autoclaved aerated concrete. Detailed single factor experiments were conducted to assess the influence of basic constituents of the mix on drying shrinkage whereas fractional factorial experiments were used for the interaction effects and the influence of some additives. It was observed that increase in lime-cement ratio and fly ash content increases drying shrinkage. Significant shrinkage reduction is obtained by autoclaving, suggesting that drying shrinkage is predominantly a function of the physical structure of the hydration product.