炭黑与钢纤维对混凝土裂缝自监测性能的影响

Effect of carbon black and steel fibers on the concrete crack self-monitoring performance

为了研究导电相对混凝土裂缝自监测性能的影响,本文对复掺炭黑-钢纤维的智能混凝土进行了试验研究。基于四电极法,对试件在弯曲荷载作用下的电阻变化率进行了分析,对比研究了不同钢纤维掺量对试件抗弯性能、裂缝自监测性能的影响。试验表明:结构型钢纤维的掺入能够显著提高试件开裂后的抗弯性能。基于荷载-时间-电阻变化率(load-time-FCR)曲线,可实现对混凝土试件开裂时刻的实时自监测。根据试验得到的电阻变化率-裂缝扩展位移(FCR-COD)曲线,FCR随着COD的增加而增加,并且曲线的斜率逐渐减小,使用对数函数能较好拟合FCR-COD关系曲线;裂缝监测灵敏度(gauge factor G)-裂缝扩展位移(G-COD)曲线中,随着钢纤维掺量的增加,相同COD下G值逐渐减小并且减小的幅度逐渐降低;结合导电机理并且使用COMSOL软件对试件裂缝自监测性能进行了分析。

In this paper,an experimental study was conducted on smart concrete mixed with carbon black(CB)and steel fibers(SF)to study the influence of conductivity on the self-monitoring performance of concrete cracks.We used the four-probe method to analyze the fractional change in resistance(FCR)of the specimen under bending load,after which we investigated the effect of different steel fiber contents on flexural performance and self-monitoring performance.Results revealed that the flexural performance of specimens was significantly improved with the addition of structural steel fibers.The time of the occurrence of a crack in specimens can be monitored in real time according to the load-fractional change in the resistance-time(Load-FCR-Time)curve.On the basis of the FCR-crack propagation displacement(FCR-COD)curve obtained from the experiment,it was observed that FCR increased with the increase of COD,the slope of the curve gradually decreased in the FCRCOD curve,and the logarithmic function fitted well with the FCR-COD curve.In the Gauge factor-COD(G-COD)curve,the value of G decreased gradually with the increase of steel fiber content.Similarly,the reduction amplitude decreased gradually under the same COD.Finally,the smart concrete self-monitoring performance was analyzed based on the conductive mechanism and the software COMSOL.