Disc-shaped specimen, drying plus rewetting procedure were designed to get better investiga- tion of effect of heat curing at early age on drying shrinkage of hardened cement pastes. The experimental re- sults show that the drying shrinkage as well as…
Disc-shaped specimen, drying plus rewetting procedure were designed to get better investiga- tion of effect of heat curing at early age on drying shrinkage of hardened cement pastes. The experimental re- sults show that the drying shrinkage as well as its i rreversible and reversible components of the hardened ce- ment pastes is decreased by heat curing, even only curing at 60 ℃ for the first 24 hours after mixing. The results of pore structure analysis show that the gel pore structure is optimized, that is, the volume of smaller gel pores with radius from 1.5 to 7 nm was increased and the volume of larger gel pores with radius from 7 to 100 nm was decreased, while the total volume of gel pores is little changed. The results of TG-DSC thermal analysis show that the microstructure of both calcium silicate hydrate (C-S-H) gel and Ca(OH) 2 phase in har- dened cement pastes is possibly changed by the heat curing. 1 INSTRUCTION of the effects of heat curing at early age on the shrin- kage behavior of the cement pastes. This work aims As is well known, when a hardened cement paste or to experimentally measure the drying shrinkage of concrete specimen is exposed to environmental hu- cement pastes in relation to heat curing at early age midity, which is normally lower than 100% relative and the change of microstructure, thus could give humidity (RH), the material begins to lose water and further insights and better understanding on the ef- the drying shrinkage occurs associated with the loss fect of heat curing at early age on drying shrinkage of water. When rewetting, some of the contraction is and microstructure of hardened cement pastes. regained, which is called reversible or recoverable shrinkage. Correspondingly, some of the deforma- tion of total drying shrinkage is permanent, called ir- 2 EXPERIMENTAL PROCEDURES reversible or irrecoverable shrinkage. Cracking and warping induced by drying shrinkage in concrete is 2.