低品质粉煤灰抹灰砂浆的强度特性

Strength characteristics of low quality fly ash plastering mortar

为探索低品质粉煤灰对抹灰砂浆强度的影响规律,以水胶比、粉煤灰取代率、超掺率和木质素纤维掺量为因素,设计正交试验方案L16(45),研究了低品质粉煤灰抹灰砂浆的强度特性。应用正交试验理论分析了各因素的作用规律及其显著性,最小二乘法建立了抹灰砂浆力学强度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%。低品质粉煤灰等量取代水泥,对砂浆的拉伸粘结强度和抗压强度负效应显著,但对劈裂抗拉强度的负效应很小;超掺有显著的增强效应,对于抗拉强度和抗压强度,适当超掺的正效应可以补偿甚至超过取代引起的损失;木质素纤维掺量增加0.3%,砂浆的粘结强度和抗拉强度分别增大0.15 MPa和0.24 MPa,增强效应明显;建立的回归模型显著性高,相关性好。研究结果对有效利用低品质粉煤灰,改善抹灰砂浆性能具有重要的现实意义。

In order to explore the influence of low quality fly ash on strength of mortar plastering,considering factors like water binder ratio,replacement rate of fly ash,mixing ratio of fly ash and lignin fiber content,the strength characteristics of low-quality fly ash plastering mortar were studied by an orthogonal test. The effect of each factor was analyzed using the orthogonal test theory,and multivariate nonlinear regression models of plastering mortar strength were established using the least square method. The optimal mix of M15 plastering mortar,water binder ratio of which is 0. 6,replacement rate of fly ash of which is 40%,super-mixing ratio of fly ash of which is 15% and lignin fiber content of which is 0. 2% was put forward. Under experimental environment,the negative effect of equivalent replacement of cement with low quality fly ash on the tensile bonding strength and com-pressive strength of mortar is significant,while the effect on the splitting tensile strength is very small; Excessive mixing of low quality fly ash has a significant enhancement effect on the strength of mortar,and suitable excessive mixing can compensate,or even exceed the loss of tensile and compressive strength caused by equivalent replacement; When lignin fiber content is increased by0. 3%,the bond strength and tensile strength of mortar are increased by 0. 15 MPa and 0. 24 MPa respectively,and the enhancement effect is obvious. The significance of the regression model is high,and the correlation is good. The results have practical importance for effective use of low quality fly ash to improve performance of plastering mortar.