【作者】 闫佳；

【导师】 张海燕；

【作者基本信息】 华南理工大学 ， 防灾减灾工程及防护工程， 2016， 硕士

【摘要】 钢筋与混凝土之间的粘结作用是二者共同工作的前提,二者间的粘结作用一旦失效将会给建筑物带来极其严重的后果。地聚物混凝土因绿色环保、快硬早强等优良特性在工程中有着广阔的发展前景。尽管近年来关于地聚物混凝土基本力学性能的研究已有很多,但有关钢筋与地聚物混凝土粘结性能的研究还较少,尤其是钢筋与地聚物混凝土高温粘结性能的试验数据还很缺乏。基于此,本文通过中心拉拔试验和梁式拉拔试验研究了地聚物混凝土与钢筋常温下及高温后的粘结性能。本文的主要研究内容及成果如下:1.对24个钢筋-地聚物混凝土粘结试件进行了中心拉拔试验,分析了钢筋与地聚物混凝土的粘结破坏机理,考察了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粘结长度等因素对钢筋-地聚物混凝土粘结性能的影响,并与普通水泥混凝土的粘结性能进行了比较。实验结果表明,对于粘结长度为5d(d为钢筋直径)的变形钢筋-地聚物混凝土中心拉拔试件,当相对保护层厚度(c/d)小于3.67时,可能会发生混凝土劈裂破坏;对于d=14 mm的变形钢筋,9d的粘结长度可使其在试件拔出破坏前先屈服;实验制备的地聚物混凝土与钢筋的粘结强度不低于同强度等级的普通水泥混凝土。基于实验结果,还建立了变形钢筋-地聚物混凝土的粘结-滑移本构模型,采用该模型计算得到的变形钢筋-地聚物混凝土的粘结-滑移曲线与实测曲线接近。2.开展了75个钢筋-地聚物混凝土和15个钢筋-普通水泥混凝土粘结试件的高温后中心拉拔试验,考察了钢筋类型、钢筋直径等因素对钢筋-地聚物混凝土高温后粘结性能的影响,并与钢筋-普通水泥混凝土高温后粘结性能进行了比较。实验结果表明,当温度在300℃以下时,钢筋-地聚物混凝土的粘结强度随温度变化不大,但超过300℃时,粘结强度显著降低且下降得比抗压强度更快;钢筋与地聚物混凝土的高温后粘结性能和同强度等级的普通水泥混凝土也较为接近。基于实验结果,还建立了变形钢筋-地聚物混凝土粘结强度的高温退化模型,采用该模型计算得到的高温后粘结强度与实测结果吻合较好。3.开展了10根钢筋-地聚物混凝土和2根钢筋-普通水泥混凝土全梁粘结试件的梁式拉拔试验,考察了箍筋间距、钢筋粘结长度对钢筋-地聚物混凝土粘结性能的影响,比较了真实受力状态下钢筋与地聚物混凝土和普通水泥混凝土粘结性能的差异,并与中心拉拔试验的结果进行了对比。实验结果表明,当箍筋间距大于钢筋粘结长度时,箍筋对钢筋-地聚物混凝土粘结强度的提高作用不明显,但可以显著改善试件粘结破坏时的延性;对于d=18 mm的变形钢筋梁式拉拔试件,7d的粘结长度可使钢筋在试件粘结破坏前屈服;相同条件下,梁式拉拔试验获得的钢筋与地聚物混凝土的粘结强度大于中心拉拔试验的结果。更多还原

【Abstract】 The bonding effect between reinforcement and concrete is the fundamental of the two kinds of material working together. Serious consequence will be caused once bond failure occurred between steel bars and concrete. Geopolymer concrete is regarded as a kind of promising construction material, due to its environmental-friendliness and excellent mechanical properties. Although there are a lot of researches on the basic mechanical properties of geopolymer concrete in recent years, there are few studies on the bond behavior between steel bars and geopolymer concrete, especially on the high temperature bond behavior of geopolymer concrete. To investigate the bond behavior between steel bars and geopolymer concrete at ambient temperature and after exposure to elevated temperatures, pull-out tests and beam tests were conducted on steel bar-geopolymer concrete composite specimens in this paper. The main research contents and conclusions are listed as follows:1. Pull-out tests were carried out on 24 geopolymer concrete prisms with steel bars embedded. The bond mechanism was analyzed,and the effect of compressive and split tensile strength of geopolymer concrete, steel bar type, steel bar diameter, concrete cover and steel bar anchorage length on bond properties between steel bars and geopolymer concrete was explored. Also a comparison on the bond behavior of steel bars with geopolymer concrete and ordinary cement concrete(OPC) was conducted. The test results show that, for geopolymer concrete specimens with steel bar anchorage length of 5d(d is the diameter of steel bar), splitting failure of geopolymer concrete tends to occur if the relative cover thickness(c/d) is lower than 3.67. An anchorage length of 9d is long enough for specimens with steel bar diameter of 14 mm, to make the bar yield before the bar was pulled out. Moreover, the bond strength of steel bars with geopolymer concrete is not lower than that of OPC with same strength grade. Based on the test results, a bond-slip constitutive model between deformed bars and geopolymer concrete was established. And the calculated bond-slip curves by using this model are close to that obtained from pull-out tests.2. Pull-out tests were conducted on 75 geopolymer concrete specimens and 15 ordinary cement concrete specimens with steel bars embeded after exposure to elevated temperatures. The influence of steel bar type, steel bar diameter on bond properties between steel bars and geopolymer concrete after exposure to elevated temperatures was analyzed. The experimental results indicate that no significant degradation occurred on bond strength between geopolymer concrete and steel bars when exposure temperature is lower than 300℃. However, when temperature exceeds 300℃, bond strength degrades quickly, and even at a higher rate than that of compressive strength of geopolymer concrete. After exposure to elevated temperatures, geopolymer concrete also exhibits comparable bond strength with the same strength grade OPC. Based on the test results, a regression model on bond strength degradation of geopolymer concrete specimens, as a function of exposure temperatures, was developed. The calculated curves using the regression model on bond strength-temperature relationships shows a good agreement with that from test results.3. Ten geopolymer concrete beam specimens and two OPC beam specimens with steel bars embedded were tested on static load. The influence of stirrup spacing and steel bar anchorage length on bond properties between geopolymer concrete and steel bars was studied. A comparison between bond behavior of geopolymer concrete and OPC in a real mechanical state, and a comparison between beam tests and pull-out tests were carried out. The test results show that a decrease of stirrup spacing improves the ductility of specimens greatly, but has no significant effect on bond strength, when the stirrup spacing is larger than steel bar anchorage length. For the beam specimens with a bar diameter of 18 mm, an anchorage length of 7d is long enough to make the bar yield before bond failure. Under the similar conditions, bond strength between geopolymer concrete and steel bars obtained from beam tests is higher than that from pull-out tests.更多还原