大温差、干寒地区日照对混凝土箱梁的影响规律

Effect of Sunlight on Concrete Box Girder in Arid and Cold Region with Large Temperature Difference

为研究大温差、干寒地区日照对保存在预制场的混凝土箱梁的影响规律,首先对原材料进行了检测,利用混凝土抗裂环,给出了日照养护与无日照养护条件下混凝土抗裂性的优劣;同时测试了在日照养护与无日照养护下混凝土的强度变化规律及强度损失,将得到的结果与标准养护下的结果进行了对比分析;然后,测试了预制箱梁在预制场保存期间的温度场变化规律,给出了不同时间段的温度变化梯度。得出结论:(1)日照可以提高混凝土的强度,但是会对混凝土的抗裂性产生不利的影响;(2)日照作用下混凝土的抗拉强度和抗压强度损失都大于无日照养护下的混凝土;(3)存放于露天梁场的混凝土箱梁一天内的日照温度梯度在不断发生变化,在下午14:00时变化幅度达到最大。

The aim of this research is to investigate the influence of sunlight on concrete box girder at precasting yard in arid and cold regions with big temperature difference. First of all the materials were tested,and concrete anti-crack ring was used to test the advantages and shortcomings of concrete in curing conditions both in the presence and in the absence of sunlight. Moreover,the variations and losses of concrete strength were also analyzed under the above mentioned curing conditions,and the obtained results were compared with those under standard curing. In addition,the changes of temperature field of precast box girders in the precast yard were tested and the temperature gradients in different time periods were acquired. The results are concluded as follows: 1) sunlight enhances the strength of concrete,but exerts adverse impact on the crack resistance of concrete; 2) the losses of tensile strength and compressive strength of concrete under sunlight curing are both larger than those in the absence of sunlight; 3)the temperature variation law of box girder in the precasting yard and the change law of temperature gradient in the same time of a day are given.