改性SiO_(2)气凝胶水泥基复合砂浆性能及冻融损伤研究

Study on Properties and Freeze-thaw Deterioration of Modified SiO_(2) Aerogel Cement-based Composite Mortar

采用KH570硅烷偶联剂对SiO_(2)气凝胶颗粒进行表面改性,将其等体积置换砂后掺入水泥砂浆中,制备得到改性气凝胶水泥基复合砂浆。对不同SiO_(2)气凝胶掺量的水泥基复合砂浆的干密度、抗折抗压强度、导热系数和孔隙结构进行了测试,开展了水泥基复合砂浆快速冻融循环试验,分析了冻融循环对其抗压强度、动弹性模量、导热系数的影响规律,并采用电子扫描电镜(SEM)揭示了改性SiO_(2)气凝胶水泥基复合砂浆冻融循环后的劣化机理。结果表明:硅烷偶联剂改性后的SiO_(2)气凝胶颗粒可较为完整地嵌于水泥砂浆中,从而改善SiO_(2)气凝胶砂浆的孔隙结构;随着改性后SiO_(2)气凝胶的替换比例增加,水泥基复合砂浆的干密度、抗压抗折强度、导热系数明显下降,而孔隙率先减小后增加,当替换比例为40%时导热系数降低了46%、抗折强度降低了43%、抗压强度降低了68%、孔隙率增加了49%。SiO_(2)气凝胶能够提高水泥砂浆的抗冻性能,但随着冻融循环次数的增加,SiO_(2)气凝胶颗粒与胶凝材料的界面粘结破坏是其劣化的主要原因。

The surface modification of SiO_(2) aerogel particles was carried out by using KH570 silane coupling agent,and the modified SiO_(2) aerogel was mixed into the cement mortar by using the method of equal volume replacement sand to prepare the modified aerogel cement-based composite mortar.The dry density,flexural and compressive strength,thermal conductivity and pore structure of cementitious composite mortars with different SiO_(2) aerogel admixtures were tested.The rapid freeze-thaw cycle test of cementitious composite mortar was carried out,and the influence laws of freeze-thaw cycle on compressive strength,dynamic elastic modulus and thermal conductivity were analyzed,and the mechanism of deterioration of modified SiO_(2) aerogel cementitious composite mortar by freeze-thaw cycle was revealed by electron scanning electron microscopy(SEM).The results show that the SiO_(2) aerogel particles modified by KH570 can be more completely embedded in the cement mortar,thus improving the pore structure of SiO_(2) aerogel mortar.With the increase of the replacement ratio of modified SiO_(2) aerogel,the dry density,compressive and flexural strength,and thermal conductivity of cementitious composite mortar decreased significantly,while the porosity decreased first and then increased.When the replacement ratio was 40%,the thermal conductivity decreased by 46%,the flexural strength decreased by 43%,the compressive strength decreased by 68%,and the porosity increased by 49%.SiO_(2) aerogel can improve the frost resistance of cement mortar,but with the growth of the number of freeze-thaw cycles,the interfacial damage of SiO_(2) aerogel particles and cementitious materials is the main reason for its deterioration.