废弃瓷砖粉对超高性能混凝土的抗压强度影响规律与机制

超高性能混凝土极低的水胶比和较高的水泥用量，使其在广泛应用中面临着水泥基体高自收缩和高成本等问题，而使用工业副产品或废弃物取代部分水泥是有效的解决方法之一。废品瓷砖已成为一种大宗工业废弃物，应用瓷砖粉在超高性能混凝土中可有效地解决水泥的高消耗和废弃瓷砖的堆积问题。因此，使用瓷砖粉取代水泥质量的10wt%、15wt%、20wt%和25wt%来制备新型绿色低碳超高性能混凝土，主要研究了瓷砖粉对超高性能混凝土抗压强度的影响规律，并采用修正Andreasen堆积模型、XRD分析、TG/DTG、SEM观察探讨了瓷砖粉对超高性能混凝土的改性机制，同时对瓷砖粉超高性能混凝土的环境足迹和成本进行了分析。研究结果表明，瓷砖粉的掺入对超高性能混凝土各龄期抗压影响在±10%以内，但对7~28天和28~60天的抗压强度发展影响显著，在25wt%掺量时抗压强度增长率分别达到了104.6%和51.8%。这主要是由于瓷砖粉的掺入提高了超高性能混凝土的堆积密实度，发生二次水化反应并生成了低钙硅比的水化硅酸钙凝胶，提高了水泥的水化程度，降低了界面过渡区的宽度。并且由环境影响和成本计算可知，瓷砖粉可有效降低超高性能混凝土的能耗、CO₂排放量和成本。 

Effect law and mechanism of ceramic tile powder on compressive strength of ultra high performance concrete

Ultra high performance concrete (UHPC) is faced with the problems of high cost and high self-shrinkage of cement matrix due to its extremely low water-binder ratio and high cement content in its wide application. One of the effective solutions is to replace part of cement with industrial by-products or wastes. As the waste ceramic tile has become a large amount of industrial waste, the application of ceramic tile powder in UHPC can effectively solve the problems of high consumption of cement and accumulation of waste ceramic tile. Therefore, ceramic tile powder was used to replace 10wt%, 15wt%, 20wt% and 25wt% by mass of cement to prepare a new type of green low-carbon UHPC. The effect law of ceramic tile powder on the compressive strength of UHPC was studied, and the modified Andreasen accumulation model, XRD analyses, TG/DTG, SEM observation were used to investigate the modification mechanisms, and the environmental footprint and the cost of ceramic tile powder on UHPC were also analyzed. The results show that the effect of the addition of ceramic tile powder on the compressive strength of UHPC is within ±10% at all age. Interestingly, ceramic tile powder has a significant influence on the development of compressive strength at 7-28 days and 28-60 days, and the increase rates of compressive strength of UHPC with 25wt% ceramic tile powder can reach 104.6% and 51.8%, respectively. This is mainly because that the addition of ceramic tile powder improves the packing compactness of UHPC, produces secondary hydration reaction and calcium silicate hydrate gel with low calcium-silicon ratio, improves the hydration degree of cement, and reduces the width of interface transition zone. According to environmental impact and cost calculation, ceramic tile powder can effectively reduce energy consumption, CO₂ emission and cost of UHPC.