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针对大体积混凝土因水化热引起的早期开裂问题,以内蒙古老山沟公路大桥承台为依托,建立了大体积混凝土三维有限元模型,分析了粉煤灰掺量、浇筑温度、环境温度与养护措施对承台中心温度、里表温差与表面拉应力的影响。模拟结果表明:混凝土表面拉应力随粉煤灰掺量增大而减小,当掺量超过30%时,降幅增大,中心温度、里表温差和表面拉应力均随其掺量增大而减小,可见掺加粉煤灰可有效降低混凝土水化热,防止表面温差裂缝的产生;当浇筑温度从5℃到30℃变化时,中心最高温度从40.3℃升至58.1℃,里表最大温差从8.6℃升至19.0℃,表面最大拉应力从0.93 MPa升至1.66 MPa,且随浇筑温度的增大,中心最高温度和里表最大温差产生的时间有所提前,表面拉应力呈线性增大趋势;里表温差和表面拉应力都随环境温度增大而减小,且表面拉应力与环境温度基本呈线性关系;养护条件越好,里表温差越小,表面拉应力明显降低,且前期表面拉应力增速减慢,峰值出现时间推迟,有利于裂缝控制。
Aiming at the early cracking problem of mass concrete caused by heat of hydration, a three-dimensional finite element model of large-volume concrete was established based on the platform cap of Laoshaogou highway bridge in Inner Mongolia. The effects of fly ash dosage, pouring temperature, ambient temperature and curing Influence of measures on temperature of center of platform, surface temperature difference and surface tension stress. The simulation results show that the tensile stress of concrete decreases with the increase of fly ash content. When the content exceeds 30%, the decrease decreases, while the center temperature, surface temperature difference and surface tensile stress increase with the increase of fly ash content Decreases with the increase of fly ash, which can effectively reduce the hydration heat of concrete and prevent the surface temperature difference cracks from occurring. When the pouring temperature changes from 5 ℃ to 30 ℃, the maximum temperature in the center rises from 40.3 ℃ to 58.1 ℃, The temperature difference increased from 8.6 ℃ to 19.0 ℃, and the maximum tensile stress increased from 0.93 MPa to 1.66 MPa. With the increase of pouring temperature, the maximum temperature in the center and the maximum temperature difference in the inner surface advanced earlier, and the surface tensile stress increased linearly The surface temperature and surface tensile stress both decrease with the increase of ambient temperature, and the surface tension stress is basically linear with the ambient temperature. The better the curing conditions, the lower the surface temperature difference, the lower the surface tensile stress, Pre-surface tensile growth slowed down, the peak appears delayed, is conducive to crack control.