复合矿物掺合料对超高性能混凝土性能的影响

Effect of Composite Mineral Admixtures on Properties of Ultra-high Performance Concrete

超高性能混凝土(ultra-high performance concrete,UHPC)不仅具有极高的力学性能,还具有良好的工作性能和耐久性能。然而,由于极低的水胶比和较高的水泥用量,UHPC面临着基体高自收缩和高成本挑战。为有效解决这一问题,利用工业副产品或废弃物取代部分水泥成为了一种可行的方法。该研究探讨了粉煤灰和偏高岭土以1∶1(质量比)比例混合作为复合矿物掺合料(composite mineral admixtures,CMA)替代UHPC中的部分水泥,对其抗压强度、微观形貌、环境效益的影响。研究结果表明,随着CMA掺量的增加,UHPC的抗压强度呈现先增大后减小的趋势,在掺加10%CMA的情况下,UHPC表现出最高的抗压强度,相较于基准组28 d抗压强度提高了7.6%;而且掺加10%CMA的UHPC具有更为紧密的微观结构,与基准组相比水化产物含量更多,符合抗压强度的发展规律;用CMA替代15%的水泥制备UHPC,可以降低UHPC生产成本、减少碳排放,有利于生产可持续环保型的UHPC。

Ultra-high performance concrete(UHPC)exhibits not only remarkable mechanical properties but also ex-cellent workability and endurance.However,UHPC confronts challenges of high self-shrinkage of the matrix and high cost due to the extremely low water-to-cement ratio and large cement quantity.In order to solve these problems effectively,a viable approach that industrial by-products or waste materials replace partial cement has emerged.The fly ash and metakaolin are mixed in 1:1 ratio to form the composite mineral admixtures(CMA).The impact of CMA replacing part of the cement in UHPC on compressive strength,micro morphology and environmental benefit are investigated.The research findings indicate that the compressive strength of UHPC exhibits a trend of initially increasing and then decreasing with the CMA content increases.When 10%CMA is mixed,UHPC has the highest compressive strength which is 7.6%higher than the 28-day compressive strength of the reference group;Further-more,the mixed UHPC possesses a denser microstructure and more content of hydration products than the reference group,which aligns with the development law of compressive strength;UHPC prepared by CMA replacing 15%ce-ment can reduce the production cost and carbon emissions,which is conducive to the production of sustainable en-vironmental protection UHPC.