两种低热与中热硅酸盐水泥混凝土热力学特性对比分析

结合白鹤滩水电站大坝主体混凝土,全面对比了2种低热与中热硅酸盐水泥混凝土的抗压强度、干缩率、自生体积变形和绝热温升等热、力学特性。研究结果表明:采用相同水胶比和粉煤灰掺量时,低热硅酸盐水泥混凝土的7,28 d龄期抗压强度、劈拉强度、极限拉伸值、抗压弹模均低于中热硅酸盐水泥混凝土,90 d龄期时2种水泥混凝土的强度基本相当,180 d龄期时低热硅酸盐水泥混凝土超过中热硅酸盐水泥混凝土;2种水泥混凝土的干缩率较接近,低热硅酸盐水泥混凝土的28 d绝热温升比中热硅酸盐水泥混凝土低2.0~3.5 ℃,2种水泥混凝土的自生体积变形均表现为微膨胀。综合比较认为,该低热硅酸盐水泥混凝土的抗裂性能优于中热硅酸盐水泥混凝土。

Comparison of Thermal and Mechanical Properties Between Low-heat and Medium-heat Portland Cement Concrete

The thermal and mechanical properties of low-heat cement and medium-heat cement are compared with the concrete of Baihetan dam as a research object. The compared thermal and mechanical properties include compressive strength, drying shrinkage, autogenous volumetric deformation, and adiabatic thermal rise. Results indicate that given the same water-binder ratio and fly ash content, low-heat cement concrete possesses lower strength, ultimate tension and Young’s elastic modulus at 7 d and 28 d than medium-heat cement concrete does; with the extension of testing age, strength of low-heat cement concrete grows, approaching the strength of medium-heat cement concrete; while at the 180 d age, the strength and ultimate tension of low-heat cement concrete are larger than those of medium-heat cement concrete. No big difference was observed in terms of drying shrinkage, and both concretes exhibited micro-expansion in autogenous volume deformation. The insulated thermal rise of low-heated cement concrete at 28 d age is lower than that of medium-heat cement concrete by 2.0℃-3.5℃. Overall, low-heated cement concrete was rated better than medium-heated cement concrete in terms of crack resistance.