低温养护下矿物掺合料湿喷混凝土力学性能及配比优化研究

Mechanical Properties and Ratio Optimization of Mineral Admixture Wet Shotcrete under Low Temperature Curing

为系统研究粉煤灰掺量、硅灰掺量及养护温度对湿喷混凝土力学性能的影响规律,通过设计正交试验对湿喷混凝土抗压强度进行极差和方差分析。结果表明:湿喷混凝土抗压强度随养护龄期增加而增大,但抗压强度增幅随养护龄期延长而减弱;增加硅灰和粉煤掺量均能有效提高湿喷混凝土抗压强度,但粉煤灰掺量超过10%(质量分数,下同)后,粉煤灰掺量的增加对混凝土后期抗压强度没有显著的影响;三因素对湿喷混凝土抗压强度影响程度顺序为硅灰掺量>养护温度>粉煤灰掺量;湿喷混凝土抗压强度对矿物掺合料的敏感性与养护温度呈正相关,增大养护温度能够提高矿物掺合料对湿喷混凝土抗压强度的改善效果;随着养护温度的提高,团絮状胶凝物质大量生成,水化产物黏结得更为密实,混凝土的抗压强度和承载性能得到进一步增强;构建多元非线性回归模型能够对混凝土抗压强度进行预测,并且湿喷混凝土在硅灰掺量、粉煤灰掺量及养护温度分别为15%、15%和10℃时具有最佳的抗压强度。

To systematically study the effects of fly ash content,silica fume content and curing temperature on the mechanical properties of wet shotcrete,the range and variance analysis of the compressive strength of wet shotcrete were carried out by designing orthogonal tests.The results show that the compressive strength of wet shotcrete increases with the increase of curing age,but the increase rate slows down with the extension of curing ages.The compressive strength of wet shotcrete can be effectively improved by the increase content of silica fume and pulverized coal,but when the content of fly ash exceeds 10%(mass fraction,the same below),the increase of fly ash content has no significant influence on the later compressive strength of concrete.The order of the influence of the three factors on the compressive strength of wet shotcrete is silica fume content>curing temperature>fly ash content.The sensitivity of the compressive strength of wet shotcrete to mineral admixtures is positively correlated with the curing temperature.The improvement effect of mineral admixtures on compressive strength of wet shotcrete increases with the increase of curing temperature.With the increase of curing temperature,a large number of flocculent cementitious substances are generated.The hydration products bond more densely,and the compressive strength and bearing performance of concrete are further enhanced.The established multiple nonlinear models can predict the compressive strength of concrete,and wet shotcrete has the best compressive strength when the silica fume content,fly ash content and curing temperature are 15%,15%and 10℃,respectively.