混杂纤维增强超高性能混凝土的高温性能试验研究

Experimental Study on High Temperature Performance of Hybrid Fiber Reinforced Ultra-High Performance Concrete

本文对混杂钢纤维(SF)-聚丙烯纤维(PPF)-硫酸钙晶须(CSW)增强超高性能混凝土(UHPC)进行高温试验(200~800℃),研究了混杂纤维增强UHPC高温前后的物理力学性能,并借助光学显微镜和扫描电子显微镜进行微观形貌观测,探讨了基体裂缝发展过程中多尺度纤维的作用机理。结果表明:随着温度升高,UHPC的质量损失率呈增大趋势,而超声波速则呈下降趋势,同时混杂SF-PPF-CSW对基体超声波速的降低有一定减缓作用;当温度小于400℃时,混杂SF-PPF-CSW增强UHPC的弯曲强度变化微弱(<5%),超过400℃后则迅速下降,在800℃下仅为初始强度的19.2%~24.7%;残余抗压强度随温度升高呈先上升后下降趋势,在400℃时达到峰值,较常温时提升了48.9%~62.0%;各温度下,掺加SF-PPF-CSW的UHPC物理力学性能均得到了有效提升,其中混杂1.7%(体积分数)SF、0.3%(体积分数)PPF、1.0%(体积分数)CSW对UHPC力学性能提升效果最佳。

In this work,the physical and mechanical properties of hybrid steel fiber(SF)-polypropylene fiber(PPF)-calcium sulfate whisker(CSW)reinforced ultra-high performance concrete(UHPC)were investigated before and after exposed to 200~800℃.The morphologies of hybrid SF-PPF-CSW reinforced UHPC were observed with optical microscope and scanning electron microscope,respectively.And the action mechanism of multi-scale fibers in the process of fracture development in matrix was discussed.The results show that with the increase of temperature,the mass loss of UHPC increases while the ultrasonic pulse velocity decreases.Meanwhile,the SF-PPF-CSW has a certain slowing effect on the decrease of ultrasonic pulse velocity of matrix.The hybrid SF-PPF-CSW reinforced UHPC shows slight change(<5%)in flexural strength below 400℃,while sharply decreases above 400℃.After exposure to 800℃,the residual flexural strength of UHPC is about 19.2%~24.7%of initial value.With the increase of temperature,the residual compressive strength increases first and then decreases.The residual compressive strength reaches the maximum value at 400℃,which is 48.9%~62.0%higher than that at normal temperature.The hybrid SF-PPF-CSW can effectively improve the physical and mechanical properties of UHPC at all of tested temperatures,and mechanical property enhancement is optimal with 1.7%(volume fraction)SF、0.3%(volume fraction)PPF and 1.0%(volume fraction)CSW.