地聚物砂浆高温后抗拉和粘结性能及退化机理

Tensile and bond properties and strength degradation mechanism of geopolymer mortar after exposure to elevated temperatures

摘要:

为考察地聚物砂浆在有耐高温要求的混凝土结构加固领域的应用可行性，开展了常温下和高温后地聚物砂浆的抗拉强度试验以及地聚物砂浆与普通水泥砂浆及普通混凝土基体的粘结性能试验，并与普通水泥砂浆的抗拉及粘结性能进行试验比较；通过热重分析-差示扫描量热分析(TG-DSC)，探究了地聚物砂浆的高温强度退化机理.试验结果表明：地聚物砂浆与水泥砂浆及混凝土之间的常温粘结强度分别达2.15 MPa及1.7 MPa，经300 ℃高温后残余粘结强度仍有1.5 MPa左右，远高于普通水泥砂浆的粘结强度；超过300 ℃以后地聚物砂浆的强度急剧退化，这主要是因地聚物砂浆高温脱水、微观结构遭受破坏引起.基于上述试验结果，可将地聚物砂浆用于300 ℃以下高温环境的混凝土结构修补加固.

Abstract:

To investigate the feasibility of geopolymer mortar as a repair material for strengthening concrete structures in which fire resistance is one of the primary requirements, tensile strength and bond strength of geopolymer mortar on Portland cement mortar and concrete substrate were tested at ambient temperature and after exposure to elevated temperatures. Comparative tests were conducted on cement mortar specimens. Thermogravimetry and differential scanning calorimetry (TG-DSC) analysis were conducted on geopolymer paste to explore the strength degradation mechanism of geopolymer mortar at high temperatures. The results show that the bond strength of geopolymer mortar at ambient temperature on cement mortar and cement concrete substrate is 2.15 MPa and 1.7 MPa respectively, and the residual bond strength is about 1.5 MPa after exposure to 300 ℃, which is much higher than that of Portland cement mortar. When temperatures exceed 300 ℃, geopolymer mortar exhibits significant strength degradation, due to the microstructural damage induced by the dehydration of geopolymers at high temperatures. Based on the above test results, geopolymer mortar can be used as a repair material for concrete structures in high temperature environment below 300 ℃.