地聚物混凝土与钢筋黏结性能研究

Study on bond behavior between geopolymer concrete and steel bars

对24个钢筋-地聚物混凝土黏结试件进行中心拉拔试验,分析钢筋与地聚物混凝土的黏结破坏机理,考察地聚物混凝土抗压和劈裂抗拉强度、钢筋类型、钢筋直径、混凝土保护层厚度及钢筋黏结长度等因素对钢筋-地聚物混凝土黏结性能的影响,并与钢筋-普通水泥混凝土之间的黏结性能进行比较。实验结果表明,当钢筋的黏结长度为5d时,相对保护层厚度c/d=3.67为变形钢筋-地聚物混凝土中心拉拔试件破坏模式由拔出破坏向劈裂破坏转变的临界点;对于d=14 mm的钢筋-地聚物混凝土中心拉拔试件,9d的钢筋黏结长度可使钢筋屈服先于钢筋拔出或混凝土劈裂发生。基于实验结果,还建立了变形钢筋-地聚物混凝土的黏结-滑移本构模型,采用该模型计算得到的不同直径的变形钢筋-地聚物混凝土的黏结-滑移曲线与实测曲线接近。

Pull-out tests were carried out on 24 specimens for the bond behavior between geopolymer concrete and embedded steel bars, so that the bond failure mechanism can be analyzed. Firstly, the influences of compressive strength and splitting tensile strength of geopolymer concrete, type of steel bars, diameter of steel bars, thickness of concrete cover and anchorage length of steel bars on the bond behavior between geopolymer concrete and steel bars were investigated, and then the bond behavior was compared with that between steel bars and ordinary Portland cement concrete. The test results show that for those specimens with anchorage length of 5d, the relative thickness of concrete cover c/d= 3.67 shall be the critical point of failure modes changing from the pull-out failure to the splitting failure of geopolymer concrete. For the specimens with bar diameter of 14 mm subjected to centrally pulling out, the steel bar may yield before pulling out of steel bar or splitting of concrete if the anchorage length is 9d. The prepared geopolymer concrete exhibit similar compresside and split tensile strength with that of ordinary cement concrete, but higher bond strength with steel bars. Based on the test results, a constitutive model was established for the bond-slip behavior between deformed bars and geopolymer concrete. The bond-slip curves predicted by this model have good agreement with the measured curves of geopolymer concrete specimens embedded with steel bars.