水泥细度对早龄期碾压混凝土综合抗裂性的影响(英文)

水泥水化热与比表面积和化学组成有关,但是相对于调整水泥的化学组成来说,通过减小水泥的比表面积来降低水泥水化热要容易得多。为了探索水泥比表面积与碾压混凝土抗裂性能的关系,采用相同熟料磨制了3种细度的水泥,研究了水泥细度对水化热、胶砂强度的影响,以及对混凝土的工作性、力学性能(抗压强度、抗拉强度和抗拉弹性模量)、极限拉伸值、绝热温升等性能的影响;同时,采用温度–应力试验机,评估了在100%约束和近似绝热条件下水泥细度对早龄期碾压混凝土综合抗裂性能的影响。结果表明:水化热与比表面积成线性关系,降低水泥比表面积是降低混凝土温升的有效、便捷的措施;粗磨水泥提高了碾压混凝土的工作性,降低了混凝土的抗压强度和弹性模量,但混凝土极限拉伸值没有明显变化;温度–应力试验表明,随着水泥比表面积的降低,混凝土第二零应力温度更低,粗磨水泥碾压混凝土综合抗裂风险更低。

INFLUENCE OF CEMENT FINENESS ON COMPLEX CRACK RESISTANCE OF EARLY AGE RCC

Hydration beat of cement is correlated to the specific surface area (SSA) and chemical components of cement. However, it is easier to reduce the hydration heat of cement by controlling the fineness rather than by adjusting the chemical components. In order to investigate the relation between cement fineness and crack resistance of roller compacted concrete (RCC), three cements with dif-ferent SSA were obtained by grinding a clinker. The effects of cement fineness on the hydration heat, mortar strength and concrete properties (such as workability), mechanical properties (compressive strength, tensile strength and tensile elastic modulus), deforma-tion properties (ultimate tensile strain) and thermal properties (adiabatic temperature rise) were investigated. Also, a temperature stress testing machine was used as a developed approach for evaluating complex crack resistance of early age concrete. The relations between cement fineness and complex crack resistance of early age RCC in the mode of 100% restraint and adiabatic environment were analyzed as well. The results show that the concrete with coarser cement has a higher capacity of crack resistance. The hydration heat was correlated to the SSA of cement. A decrease in the SSA of cement could be an effective approach for reducing temperature of concrete. The workability of the RCC could be improved by decreasing the SSA of cement. However, the compressive strength and elastic modulus of mortar/concrete were slightly decreased for the lower SSA of cement. The ultimate tensile strain of the RCC does not vary with the SSA of cement. The temperature stress tests show that the second zero stress temperature increases with increasing the SSA of cement, and the concrete with coarser cement has a lower crack risk.