2011 Volume 65 Issue 1 Pages 118-125
This paper reports the results of an investigation of effects steam heat-curing cycles on hydration of fly ash cement for the raising efficiency of precast concrete production. The steam heat-curing conditions for the investigation were varied by changing the preset curing time（time before steam curing）, temperature rise rate, maximum temperature retention time, temperature reduction rate. The Compression tests were conducted on mortars made using fly ash cement under steam heat-curing conditions. The hydrate composition was measured by thermo-gravimetric/differential thermal analyzer（TG-DTA）, selective dissolution method and X-ray diffraction（XRD）Rietveld method to clarify the influence of steam heat-curing on fly ash cement hydration. The steam heat-curing of cement incorporating fly ash accelerates the pozzolanic reaction and results in considerable increase in the one-day compressive strength. The effect of temperature reduction rate predominates over other factors of steam heat-curing condition. The optimum conditions of steam heat-curing cycles that shorten the length of the precast concrete manufacturing process within the investigated range appears to be a 4 hours consisting of a preset curing time 0.5 hour, temperature rise rate 30℃/h, maximum temperature and its retention time at 65℃ for 2 hours, quick cooling.
