硫酸盐干湿循环作用下再生混凝土抗压与劈拉强度的关系研究

Study on relationship between compressive strength and splitting tensile strength of recycled concrete under effect of sulfate dry-wet circulation

为了建立硫酸盐干湿循环侵蚀作用下再生混凝土抗压与劈拉强度的关系,达到降低试验工作量,以及减少对实际混凝土结构测定时造成损伤的目的,设计了3种再生粗骨料取代率,共制作135组试块,并将试块放入浓度为5%的Na_2SO_4溶液中浸泡3 d,然后室内环境下晾干3 d,则设计6 d为一个干湿交替循环。分别在干湿循环侵蚀0次、30次、60次时,测定其立方体抗压强度和劈裂抗拉强度,进行回归分析,建立两者之间关系,并验证。结果表明:再生混凝土在硫酸盐干湿循环侵蚀作用下的抗压强度与劈拉强度有较好的相关性。当再生粗骨料取代率为30%、50%、70%时,对应的劈拉强度为抗压强度的1/18、1/19、1/20。当硫酸盐干湿循环侵蚀次数为0次、30次、60次时,对应的劈拉强度为抗压强度的1/17、1/18、1/19。通过验证,劈拉强度计算值与劈拉强度实测值的相对误差均在-8.0%~9.4%之间,均方根误差均小于0.25,计算值与实测值比较吻合,表明以上建立的抗压强度与劈拉强度的关系具有一定的可靠性和参考价值。

In order to establish the relationship between the compressive strength and the splitting tensile strength of the recycled concrete under the erosive effect from sulfate dry-wet circulation for getting the target of decreasing the work-load of the relevant experiment and reducing the possible damage of concrete structure during the actual measurement concerned,3 substitution rates of the recycled coarse aggregate are designed and total 135 sets of cube specimens are made,afterwards,the cube specimens are immersed in the Na2 SO4 solution with the concentration of 5%,and then soaked for 3 d and dried for 3 d,for which a 6 d drywet alternating cycle is designed. The compressive strength and the splitting tensile strength of cube specimens are respectively measured for the wet-dry erosive circulation of 0 times,30 times and 60 times,from which regression analyses are made,while the relationships between both of them are established and verified as well. The result shows that a better correlation is there between both the compressive strength and the splitting tensile strength of recycled concrete under the erosive effect from sulfate dry-wet circulation. When the substitution rates of the recycled coarse aggregate are 30%,50% and 70%,the corresponding splitting tensile strengths are 1/18,1/19,1/20 of that of the compressive strength. When the sulfate wet-dry erosive circulations are 0 times,30 times and 60 times,the corresponding splitting tensile strengths are 1/17,1/18,1/19 of that of the compressive strength. Through the relevant verification,the relative errors of the measured values of both the compressive strength and the splitting tensile strength are between-8. 0% ~ 9. 4% and the root-mean-square errors are less than 0. 25%,thus the calculated values are basically coincided with the measured ones,which indicates that the relationship between the compressive strength and the splitting tensile strength established above has a certain reliability and referential value.