温度历程对早龄期混凝土抗压强度的影响

Influence of temperature history on compressive strength of early age concrete

【目的】分析不同温度历程对混凝土早龄期抗压强度的影响,为解决实际结构中混凝土的抗压强度变化和混凝土养护条件的选择提供参考。【方法】设计变温养护系统来模拟实际结构中混凝土所经历的温度历程,测试在恒温20℃、恒温50℃和变温养护条件(由混凝土的绝热温升决定的温度制度)下4种混凝土的早龄期抗压强度,并利用等效龄期方法分析混凝土早龄期抗压强度的变化规律。【结果】3种温度环境中,同一混凝土在恒温50℃条件下养护时,24h龄期的抗压强度最高,72h龄期以后在模拟实际温度环境的变温养护条件下混凝土的抗压强度最高;与20℃养护温度相比,在恒温50℃养护条件下,672h龄期硅酸盐水泥混凝土和掺加胶凝材料质量分数10%的硅粉混凝土的抗压强度有一定下降,掺加胶凝材料质量分数20%粉煤灰和质量分数20%矿渣的混凝土的抗压强度没有下降。【结论】掺加适量粉煤灰和矿渣对高温养护的混凝土微观结构的损伤有一定修补作用,利用最小二乘法获得的等效龄期混凝土抗压强度模型参数,可以计算实际结构中变温条件下混凝土早龄期抗压强度的变化。

【Objective】The influence of different temperature histories on the compressive strength of early age concrete was studied for analysis of changes in compressive strength of concrete in real structures and selection of concrete curing conditions.【Method】Temperature tracking maintenance system was designed for simulation of concrete temperature history experienced by real structures.Compressive strengths of four early age concretes were measured in constant 20℃,constant 50℃,and changing temperature;and variations in the compressive strengths of the concretes were analyzed using equivalent age method.【Result】The compressive strengths at 24hages were the highest at the temperature of 50℃,while the concrete compressive strength at >72hage was the highest with variable temperature.The compressive strengths of 672hage portland cement concrete and concrete mixed with 10%silica were lower at 50℃compared to those at 20 ℃,while those of the other two tested concretes(mixed with 20%fly ash and20%slag)did not decrease.【Conclusion】Mixing with fly ash and slag could repair the microstructure injuries of the concrete during high temperature curing.The concrete compressive strength model can predict the variations in compressive strength of actual structures under varying temperature conditions based onparameters obtained from least squares regression method.