Energy saving benefit, mechanical performance, volume stabilities, hydration properties and products of low heat cement-based materials

Abstract

Low heat Portland (LHP) cement is one type of environmental-friendly cements with low energy consumption. A case study of Baihetan dam in this work demonstrates that replacing Portland cement (PC) by LHP cement can lead to about 83,770 GJ of energy saving. The present study investigates the thermal and mechanical performance, drying shrinkage, hydration properties and hydration products of low heat cement-based materials. The mechanical performance of LHP mortar and concrete at the late age are superior to those of PC ones, although the hydration degree of LHP paste cured for 180 days is a bit lower than that of PC paste. In addition, LHP mortar and concrete have higher strength than PC ones blended with 20 wt% fly ash. Due to the low content of C3S and slow hydration rate of LHP cement, the maximal heat flow and accumulated hydration heat of LHP paste is obviously delayed and decrease compared with PC paste and PC paste blended with 20 wt% fly ash. Besides, XRD and TG/DTA results show that LHP paste has a less amount of calcium hydroxide (CH) than PC one. Based on NMR data, calcium silicate hydrate (C-S-H) rapidly forms at early age in LHP cement paste, and the mean silicate chain length (MCL) of C-S-H in LHP paste is longer than that in PC paste at late age. Moreover, LHP cement-based materials have smaller drying shrinkage and better crack resistance performance than those of PC ones.