基于不同测试方法的密封养护水泥砂浆孔隙率和饱水度变化规律

孔隙率和饱水度是影响混凝土耐久性的两个重要因素。为研究密封绝湿养护混凝土孔隙率和饱水度的变化规律,制备了不同龄期、不同水胶比的水泥砂浆试件,采用传统称重法、压汞法和核磁共振法测试孔隙率和饱水度。试验表明:3种方法测试结果的变化规律一致,但测值存在一定差异;对于孔隙率,称重法检测值最大,核磁共振法次之,压汞法检测值最小;对于饱水度,核磁共振法检测值大于称重法。在密封养护状态下,水泥砂浆孔隙率以14 d龄期为界随龄期增加表现为先增大后减小,且水胶比为0.41的试件孔隙率最大,最大孔隙率为39%;饱水度以14 d龄期为界随龄期增加表现为先减小后增大,且随水胶比增大而增大,最小饱水度为32%。压汞法检测结果具有一定随机性,传统称重法和核磁共振法检测结果更接近试件真实孔隙率。

Change Rule of Porosity and Saturation of Cement Mortar under Sealed Curing Condition Based on Different Measured Methods

Porosity and saturation are important factors affecting the durability of concrete. To study the change rule of porosity and saturation of concrete in the state of moisture insulation, cement mortar specimens with different ages and different water-binder ratios were formed and cured under sealed condition. Then the porosity and saturation of specimens were measured by weighing method (WM), mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR). The results show that the change rules measured by the three methods are consistent despite of slight differences in values. For the porosity, WM has the largest value, followed by NMR, and MIP has the smallest value. And for the degree of water saturation, the test value of NMR is higher than that of WM. The porosity of cement mortar first increases and then decreases with the age of 14 d as the boundary. The porosity of the specimen with a water-binder ratio of 0.41 is the largest and the maximum porosity is 39%. The saturation degree of cement mortar first decreases and then increases with the age of 14 d as the boundary. Higher water-binder ratio leads to higher degree of water saturation and the minimum saturation degree is 32%. Due to the randomness of the detection results of MIP, the detection results of WM and NMR are closer to the real porosity of the specimen.