橡胶混凝土轴拉破坏过程中声发射特性

Acoustic Emission Characteristics of Rubber Concrete in Axial Tension Process

为了研究橡胶掺量对单调荷载下混凝土拉伸破坏的影响,开展了不同橡胶掺量(体积分数0%、5%、10%、15%、20%)的带缺口混凝土棱柱体的单轴拉伸破坏试验,采用声发射技术监测其破坏过程,进一步分析应力-裂缝张开位移曲线、断裂能以及声发射特征参数。结果表明:随着橡胶掺量的增加,混凝土失稳荷载下降,峰值裂缝张开位移增大,橡胶混凝土断裂能大于基准混凝土,并在橡胶掺量为15%时达到最大值;声发射累计振铃计数及累计撞击次数曲线能够将混凝土破坏过程划分为3个阶段,随着橡胶掺量的增加,声发射活性有所降低,峰值频率由高频向低频转变;声发射b值能够很好地反映混凝土试件的破坏形式,可以将混凝土试件的破坏过程划分为2个阶段,试件破坏过程中b值整体呈下降趋势,随着橡胶掺量的增加,b值有所增大,主裂纹形成阶段b值最大值与最小值的差值有所减小;橡胶掺量小于20%时,强度降低速率较快,大于20%时,强度下降减缓。

In order to study the influence of rubber content on the fracture performance of concrete under monotonic force,the uniaxial tensile tests of notched concrete prisms with different volume rubber contents(0%,5%,10%,15%,20%)were carried out.Acoustic emission technology was used to monitor the failure process of rubber concrete.Based on the test results,the curve of stress-crack opening displacement,fracture energy and acoustic emission characteristic parameters were analyzed.The results show that with the increase of rubber content,the instability load of concrete decreases,and the peak crack opening displacement increases.The fracture energy of rubber concrete is greater than that of reference concrete,and reaches the maximum value when the rubber content is 15%.The curves of acoustic emission accumulate counts and hits can divide the concrete failure process into three stages.With the increase of rubber content,the acoustic emission activity decreases,and the peak frequency changes from high frequency to low frequency.The acoustic emission b value can well reflect the failure form of the concrete specimen.The failure process of concrete specimen can be divided into two stages.During the failure process of the specimen,the b value shows a downward trend.As the rubber content increases,the b value increases.During the main crack formation stage,the difference between the maximum and minimum values of b value is reduced.The strength reduction rate is high with the rubber content less than 20%,while the strength reduction rate is lower when it exceeds 20%.