升温速率对砂浆渗透性及微观结构的影响

Effect of Heating Rate on Mortar Permeability and Microstructure

为了研究升温速率对砂浆渗透性和微观结构的影响,以3种升温速率(5、10、15℃/min)加热砂浆至500℃。通过新的实验技术允许在围压下用气体同时测量砂浆的渗透率和孔隙率,并采用核磁共振(nuclear magnetic resonance,NMR)和扫描电镜(scanning electron microscope,SEM)技术,观察损伤后试样的T_(2)谱图分布、孔径分布和裂缝演变情况。结果表明:在500℃下,随着升温速率的增大,砂浆气体渗透率与孔隙率逐渐增大。在加卸载围压的过程中,与孔隙率相比砂浆的气体渗透率对围压更敏感。不同升温速率作用后的砂浆T_(2)谱图均出现2个波峰,主波峰分布占据3个数量级。随着升温速率增大,砂浆的孔径分布向右移动,孔径增大。高温作用后,砂浆致密结构变得多孔疏松,升温速率越快,其内部裂缝宽度越大。

In order to study the effect of heating rate on the permeability and microstructure of mortar,three heating rates(5,10,15℃/min)were used to heat the mortar to 500℃.The permeability and porosity of mortar can be measured simultaneously with gas under confining pressure by a new experimental technique,and the T_(2) spectrum distribution,pore size distribution and crack evolution of damaged samples were observed by nuclear magnetic resonance(NMR)and scanning electron microscope(SEM)techniques.The results show that the gas permeability and porosity of mortar increase with the increase of heating rate at 500℃.In the process of loading and unloading confining pressure,the gas permeability of mortar is more sensitive to confining pressure than porosity.There are two peaks in the T_(2) spectra of mortar with different heating rates,and the distribution of the main peaks occupies three orders of magnitude.With the increase of heating rate,the pore size distribution of mortar moves to the right and the pore size increases.After high temperature,the dense structure of mortar becomes porous and loose,and the faster the heating rate,the larger the crack width inside it.