再生细骨料和超细粉煤灰增强UHPC的力学性能研究

Mechanical properties of UHPC enhanced by recycled fine aggregate and ultrafine fly ash

为研究超细粉煤灰和再生细骨料对超高性能混凝土(UHPC)性能的影响,通过工作性能、轴心抗压、轴心抗拉和电镜扫描试验研究了超细粉煤灰和再生细骨料对UHPC抗压强度、抗拉强度和微观结构的影响规律,并建立了基于超细粉煤灰和再生细骨料影响的UHPC强度预测模型。结果表明:增加超细粉煤灰掺量,UHPC扩展度增加流动性较好,掺量不超过10%可改善UHPC抗压强度,达到115.36 MPa,超过后抗压强度有所降低,抗拉强度呈现上升趋势;再生细骨料掺量增加UHPC工作性能变差,但抗压强度及抗拉强度逐渐升高;电镜扫描试验发现粉煤灰消耗Ca(OH)_(2)产生更多C-H-S凝胶使得结构内部更加密集。基于改进的可压缩堆积理论模型,建立了超细粉煤灰改性再生细骨料UHPC强度预测模型。

In order to study the effects of ultrafine fly ash and recycled fine aggregate on the performance of ultra-high performance concrete(UHPC),the compressive strength,tensile strength and microstructure of UHPC studied by workability test,axial tensile strength test,axial compressive strength test and scanning electron microscopy(SEM).The UHPC strength prediction model based on the influence of ultrafine fly ash and recycled fine aggregate established.The results show that the UHPC expands and flows well,the compressive strength decreases and the tensile strength presents an upward trend with the increase of ultrafine fly ash contentThe compressive strength of UHPC could be improved to 115.36 MPa when ultrafine fly ash content is less than 10%.With the increase of recycled fine aggregate content,the working performance of UHPC becomes worsen,but the compressive strength and tensile strength increase gradually.SEM test that fly ash Ca(OH)_(2) to produce more C-H-S gel,making the structure more dense internally.Based on the improved theoretical model of compressible stacking,a UHPC strength prediction model of ultrafine fly ash modified reclaimed fine aggregate established.