高湿偏低温环境对蒸养混凝土强度发展的影响

Effect of High-Humidity and Lower-Temperature Environment on Strength Development of Steam-Cured Concrete

采用在10-14℃水中养护模拟蒸养混凝土的高湿偏低温使用环境,研究掺加矿粉、粉煤灰和硅灰的混凝土经过（80±2）℃恒温6 h的强度发展。试验结果表明：掺加矿粉、粉煤灰、硅灰可显著提高蒸养混凝土的脱模强度,提高其抗裂性;10-14℃水养至28 d龄期,混凝土出现相对抗压强度倒缩现象,且脱模抗压强度越高的混凝土强度倒缩值也越高;劈裂抗拉强度的发展与其强度高低有关,脱模劈裂抗拉强度相对较低的试件,在整个养护期间,其值缓慢增长,而脱模劈裂抗拉强度相对较高的试件,在整个养护期间,其值出现相对倒缩;蒸养混凝土内部有大量孔隙,多数孔隙中存在针片状AFm相;混凝土在高湿偏低温环境中的吸水膨胀和AFm相向AFt相的转变是造成蒸养混凝土强度倒缩的主要原因。

To imitate high-humidity and lower-temperature working environment,the demouled concrete steam-cured at（80±2）℃ for 6h is immersed in water at 10~14℃,and the strength development of those with blast furnace slag,fly ash and silica fume was studied.Experimental results show that when incorporating blast furnace slag,fly ash,and silica fume,the demoulded compressive strength and crack-resistance are improved;after cured in water at 10~14℃ for 28d,the relative compressive strength of the concrete decreases,and the higher the demoulded compressive strength,the greater the strength decreases;and the tensile-splitting strength development is related to the demoulded strength,and the tensile-splitting strength increases slowly during the whole curing age when demoulded tensile-splitting strength is relatively low,otherwise,tensile-splitting strength decreases;after steam-curing,large quantities of pores exist in the concrete,in which needle-like and flake-like AFm phases appear.It is shown that expansion caused by water absorption and phase conversion from AFm to AFt are the main reasons for the strength decrease of the steam-cured concrete in high-humidity and lower-temperature environment.