养护温度和矿物掺合料对蒸养混凝土脆性的影响

为了掌握蒸养混凝土的脆性特性,以脆性系数和冲击韧性为评价指标,研究了养护温度(20、45、55、65、75℃)及矿物掺合料对混凝土脆性的影响,并通过扫描电子显微镜和压汞仪分析了养护温度和矿物掺合料对混凝土水化产物微结构和孔结构的影响。结果表明,随着养护温度的升高或养护龄期的延长,混凝土的脆性系数增大,且蒸养降低了混凝土的冲击韧性,复掺粉煤灰和矿渣粉掺合料可以改善蒸养混凝土的脆性和抗冲击性能。较高养护温度导致水化产物结晶粗大,界面过渡区形成微裂缝和基体孔隙率增大,从而使蒸养混凝土脆性增大,复掺粉煤灰和矿渣粉掺合料改善了蒸养混凝土的孔结构和界面过渡区微结构。

Effects of Curing Temperature and Mineral Admixtures on Brittleness of Steam Cured Concrete

In order to master the brittleness characteristic of steam cured concrete, the effects of curing temperature (20, 45, 55, 65, 75 ℃)and mineral admixtures on brittleness of concretewere studied by using brittleness coefficient and impact toughness as evaluation indexes, and the effects of curing temperature and mineral admixtures on the microstructure of hydration products and pore structure of the concrete were analyzed by scanning electron microscope and mercury porosimeter. The results show that the brittleness coefficient of the steam cured concrete increases with the increase of curing temperature or curing age, and the steam curing reduces the impact toughness of concrete. When two mineral admixtures of fly ash and granulated blast furnace slag (GBFS) powder are added into concrete mixture, the brittleness coefficient and impact resistance of the steam cured concrete are improved. Higher curing temperature leads to coarse crystallization of hydration products, formation of micro cracks in the interface transition zones and increment of porosity of concrete matrix, which increases the brittleness of steam cured concrete. Fly ash and GBFS improve the pore structure and microstructure of the interface transition zone of steam cured concrete.