Relation Between the Compressive Strength and Porosity of Autoclaved Calcium Silicate Hydrates

Calcium silicate hydrates were produced by high‐pressure steam curing of compacted mixtures of hydrated lime, ground quartz, and water using various lime/silica ratios, molding pressures, and times and temperatures of curing. Compressive strengths ranged from 825 to 32,000 psi and porosities from 0.25 to 0.45. The strengths depended chiefly on total porosity and pore size distribution; phase composition was of secondary importance with certain exceptions. In general, strength decreased as the proportion of larger pores increased. Compressive strengths were best fitted by the Bal'shin relation, S=S 0 (1‐ɛ) m , or by the Ryshkewitch relation, S=S 0 e −be , where S =strength of porous material, S 0 =theoretical strength of similar nonporous material, ɛ=porosity, and b and m =empirical constants.