低品质粉煤灰抹灰砂浆的干燥收缩特性研究

摘要

通过正交试验研究水胶比、粉煤灰取代率和超掺率、木质素纤维掺量对抹灰砂浆干燥收缩特性的影响,利用最小二乘法建立了抹灰砂浆干燥收缩变形的多元非线性回归模型,提出了M15抹灰砂浆的最优组合为:水胶比0.60,粉煤灰取代率40％、超掺率15％,木质素纤维掺量0.2％.结果表明:低品质粉煤灰等量取代水泥或掺加木质素纤维对砂浆的干燥收缩具有明显的抑制效应,超掺低品质粉煤灰使砂浆的收缩变形略微增大,但影响不显著;砂浆的干缩率随龄期的延长而增加,早期增加快、后期增加缓慢,28d就完成了整个龄期总收缩变形的80％以上,早期是减小砂浆干缩变形的最佳阶段;砂浆干燥收缩变形实测值与模型预测值间的偏差小,模型预测结果准确可信.%The influence of water binder ratio,replacement rate and super adding rate of fly ash,and lignin fiber content on drying shrinkage property of plastering mortar was studied by orthogonal test,and multivariate nonlinear regression model of plastering mortar drying shrinkage were established using least square method.The optimal combination of M15 plastering mortar was put forward as follow:water/binder ratio as 0.60,replacement ratio of fly ash as 40％,excess ratio of fly ash as 15％,doping ratio of lignin fiber as 0.2％.The results show that equivalent replacement of cement with fly ash or addition of lignin has obvious inhibition effect on the drying shrinkage of mortar,super addition of low quality fly ash slightly enlarges the shrinkage of mortar,however,the influence is not significant;The drying shrinkage of mortar increases with the age,which increases rapidly in the early period and slowly in the later,more than 80％ of the total shrinkage of mortar has been completed within 28 d,so that the early period is the best stage for decreasing the drying shrinkage of mortar;The deviation of mortar shrinkage between the measured value and the predicted value is small,therefore the prediction results of the model are accurate and reliable.