基于灰色理论的CBC单面冻融后抗压强度与孔结构参数关系研究

通过对水泥基材料(CBC)进行以NaCl溶液为冻融介质的单面冻融试验,探究CBC抗压强度及含气量、气泡间距系数、气泡比表面积、气泡平均弦长、气泡弦长大于20 μm的弦长频率等微观孔结构参数随冻融循环次数增加的变化规律,并运用灰色理论对抗压强度与各孔结构参数的内在联系进行分析。利用灰色相对关联度筛选出微观孔结构参数中与抗压强度关联最大的参数,对其进行了相关模拟和预测,并建立宏观性能与微观孔结构参数间的定量关系。结果表明:随冻融循环次数增加,CBC抗压强度逐渐降低,冻融循环后期下降速率加快; 试验过程中试件内部含气量、气泡间距系数、气泡平均弦长逐渐增大,而气泡比表面积逐渐减小; 灰色Verhulst模型相较于GM(1,1)模型更适用于气泡弦长大于20 μm的弦长频率的模拟; 采用灰靶决策模型定义的综合孔结构参数与抗压强度关联性更强,基于综合孔结构参数建立的模型精度更高。

Relationship between compressive strength and pore structure of CBC after single side freeze-thaw based on grey theory

Through the single-side freeze-thaw test of cement-based composite materials(CBC)with NaCl solution as the freeze-thaw medium, the compressive strength and micro-pore structure parameters of CBC, such as air content, bubble spacing coefficient, bubble specific surface area, bubble average chord length and chord length frequency with bubble chord length larger than 20 μm, were investigated with the increase of freeze-thaw cycles. The internal relationship between compressive strength and pore structure parameters was analyzed by grey theory. The parameters with the greatest correlation with compressive strength among the microscopic pore structure parameters were screened by grey relative correlation degree, and the related simulation and prediction were carried out, and the quantitative relationship between macroscopic properties and microscopic pore structure parameters was established. The results show that with the increase of freeze-thaw cycles, the compressive strength of CBC decreases gradually, and the rate of decline in the later stage of freeze-thaw cycles increases. During the test, the internal air content, bubble spacing coefficient and average chord length of bubbles gradually increase, while the specific surface area of bubbles gradually decrease. Compared with the GM(1,1)model, the grey Verhulst model is more suitable for the simulation of the chord length frequency of the bubble string larger than 20 μm. The comprehensive pore structure parameters defined by the grey target decision model have a stronger correlation with the compressive strength, and the model based on the comprehensive pore structure parameters has higher accuracy.