高性能水泥基复合材料的压剪性能和破坏准则

Compression-shear performance and failure criteria of the high-performance cement-based composite

高性能水泥基复合材料(High-performance cement based composite,HPCC)是建筑领域的一种前沿性材料,其强度高、韧性强,具有很好的应用前景。高强度钢纤维通常以适当的混合比例加入HPCC中。设计并浇筑了4种不同钢纤维体积分数(0.0vol%、0.5vol%、1.0vol%、2.0vol%)的HPCC,对不同纤维含量的试件的压剪复合性能进行了深入研究。通过试验首先给出了HPCC复合应力作用下基于莫尔-库仑的压剪强度模型。研究结果表明,纤维掺量对HPCC的压剪界面摩擦系数影响较小,其平均值为2.8826,不同纤维掺入量的HPCC的摩擦系数与均值相比的差异在–1.44%~8.51%之间;黏聚力则与钢纤维体积掺量呈二次抛物线关系。而HPCC压剪位移峰值与钢纤维掺入量之间呈现先增加后减小的现象。其次,对HPCC破坏界面进行SEM形貌分析,研究钢纤维影响HPCC基体的微观机制,从SEM形态出发解释了材料压剪强度和位移变化的微观机制。最后,结合试验结果和已有文献研究,提出了基于Ottosen模型的HPCC破坏准则,并给出了具体的拟合参数,表明HPCC八面体剪应力高于普通混凝土材料。试验数据与理论分析结果吻合较好,能够反映HPCC的破坏包络面特征。

High-performance cement-based composites(HPCC)is a prospecting material in the construction field.Because of its high strength and increased toughness,the material has excellent applications prospects in the future.High-strength steel fibers are usually incorporated in HPCC with proper mixing ratios.Four kinds of HPCC with varying fibers volume fractions(0.0vol%,0.5vol%,1.0vol%,2.0vol%)were designed and fabricated to study the combined compression-shear performances of HPCC.Firstly,the Mohr-Coulomb-based model of compressionshear strength of HPCC was proposed and verified based on the experimental data.The results demonstrate that the fiber content has little effect on the friction coefficient of the compression-shear interface of HPCC,with an average value of 2.8826,and the friction coefficients of HPCC with different fiber contents varies from–1.44%to 8.51%compared with the average values.The cohesion stress exhibits a quadratic parabola relationship with the volume content of steel fiber.However,the peak displacement of HPCC under compression-shear loads increases at first and then decreases with the increasing content of steel fibers.Secondly,the SEM morphology of the failure interface of HPCC was analyzed,and the microscopic mechanism of the influence of steel fiber on the HPCC matrix was studied.The SEM morphology images explain the microscopic mechanism of the deterioration of compressive shear strength and variation of shear displacement.In the end,the Ottosen-based failure criterion of HPCC was proposed by combining the experimental results and the research data from the existing literature.And the specific fitting parameters were also presented,which predicts that the octahedral shear stress of HPCC is higher than that of the ordinary concrete.The experimental data are in good agreement with the theoretical analysis results,which can reflect the failure envelope characteristics of HPCC.The experimental data are in good agreement with the regression results,which could reflect the characteristics of the failure envelope of HPCC.