低气压养护对水泥砂浆微观孔隙及抗渗性能的影响

Effect of Low Air Pressure Curing on Micropore Structure and Impermeability of Cement Mortar

利用低气压环境模拟箱对水泥砂浆进行养护,测试分析不同低气压(0.2 P_(0)、0.5 P_(0)、0.8 P_(0)、1.0 P_(0),P_(0)为标准大气压)养护条件下砂浆的力学性能、抗渗性能、气孔结构、微观形貌和水化产物,以探明低气压养护对水泥砂浆微观孔隙与抗渗性能的影响机理.结果表明:低气压养护劣化了硬化水泥砂浆的力学性能和抗渗性能,在(0.5~0.8)P_(0)范围内的力学性能衰减特别明显;低气压养护下水泥砂浆的含气量增大,气孔间距系数增大,大孔所占比例增大,气孔结构显著劣化;硬化水泥砂浆的微观气孔结构对其宏观抗渗性具有显著影响,随着养护气压的降低,硬化水泥砂浆的含气量、气孔间距系数和平均孔径提高,导致其抗渗强度降低,原因包括凝胶结构、水分蒸发、水化产物以及气泡的引入等.

To investigate the mechanism of influence of low air pressure curing on the micropore structure and impermeability of cement mortar,the low air pressure environment chamber was used in curing cement mortar,and the mechanical properties,impermeability,pore structure,micromorphology and hydration products of mortar under low air pressure(0.2 P_(0),0.5 P_(0),0.8 P_(0),1.0 P_(0),where P_(0)is the standard atmospheric pressure)were tested and analyzed.The results show that low curing air pressure degrades the impermeability and mechanical properties,and the mechanical properties decline most seriously in the range of(0.5-0.8)P_(0).Air content,pore spacing coefficient and the proportion of large pores of cement mortar cured in low air pressure increases,and the pore structure deteriorates significantly.Micropore structure of hardened cement mortar has a significant effect on its impermeability.With the decrease of curing air pressure,the air content,pore spacing coefficient and average pore aperture increase,resulting in the attenuation of impermeability.The cause of it includes the gel structure,water evaporation,hydration products and the introduction of bubbles.