升温速率对砂浆渗透性及微观结构的影响

为了研究升温速率对砂浆渗透性以及微观结构的影响，现以3种升温速率（5℃/min、10℃/min、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（NMR）和扫描电镜（SEM）技术，观察损伤后试样的T2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T2谱图均出现2个波峰，主波峰的分布占据了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。

Effect of Heating Rate on Mortar Permeability and Microstructure

In order to study the effect of heating rate on mortar permeability and microstructure, the mortar is heated to 500°C at three heating rates (5°C/min, 10°C/min, 15°C/min).The new experimental technique allows the simultaneous measurement of mortar permeability and porosity with gas under perimeter pressure and the observation of T2 spectral distribution, pore size distribution and fracture evolution of the damaged specimens using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) techniques.The results showed that the mortar gas permeability and porosity gradually increased with the increase of heating rate at 500°C.During loading and unloading of surrounding pressure, the gas permeability of the mortar is more sensitive to the surrounding pressure compared to the porosity.The T2 spectra of the mortars after the action of different warming rates all showed two wave peaks, and the distribution of the main wave peak occupied three orders of magnitude.As the heating rate increases, the pore size distribution of the mortar shifts to the right and the pore size increases.After the action of high temperature, the dense structure of mortar becomes porous and loose, and the faster heating rate, the larger the width of its internal cracks.