粉煤灰掺量对喷射混凝土力学性能的影响

Influences of Fly ash Content on the Mechanical Properties of Shotcrete

喷射混凝土是新奥法施工的重要技术之一,在喷射混凝土中掺入适量的粉煤灰不仅可以起到减少裂缝、补偿收缩等作用,而且可以提高喷射混凝土的和易性、降低工程施工造价。通过一定数量的试验研究了喷射混凝土中的粉煤灰掺量对混凝土力学性能(包括抗拉、抗压、抗折强度)的影响。试验表明:喷射混凝土的各项强度指标随着粉煤灰掺量的增加而逐渐减小;当粉煤灰掺量超过28%时,喷射混凝土强度损失较为严重;对于普通喷射混凝土施工中,建议粉煤灰取代水泥的最佳掺量应该在9%左右。

As an important component of New Austria Method, the shotcrete technique has the characteristics of simple proce dure, fast installation, and wide applications. It becomes an essential tool in the tunnel excavations. Adding the adequate amount of fly ash into the shotcrete mixture can reduce the potential shrink cracks, improve the workability and optimize the construction cost. The impact of fly ash content on the mechanical properties （tensile, compressive and bending strengths） is studied in this paper through the laboratory tests. The results indicate that all indicator strengths reduce with the increase of fly ash content in the mixture. A significant strength reduction can be found at fly ash content of 28%. It is suggested that for a regular shotcrete mix design, the optimum fly ash content should be 9 %.