Creep and drying shrinkage of calcium silicate pastes III. A hypothesis of irreversible strains

Abstract Irreversible strains, measured on pastes of pure calcium silicates which were loaded without drying, dried to 53% rh without loading, or were loaded and simultaneously dried to 53% rh, are correlated with indications of structural changes occurring within the hydrated pastes. These changes are interpreted in terms of microstructural models of the hydrated pastes. It is assumed that irreversible strains are caused only by changes in the “pore component” and the “CSH component.” In young pastes irreversible shrinkage can be explained by a reduction in pores in the range 40–100 A diameter. In well-hydrated pastes structural changes in the silicate framework of the “CSH component” dominate irreversibility. Microshearing between CSH particles is thought to occur under load. An increase in degree of silicate polymerization bonding occurs on drying, and this increase is greater when drying takes place under load.

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