复合钢筋与早龄期海工混凝土黏结性能研究

Bond properties between bimetallic steel bar and early-age marine concrete

摘要:

为研究复合钢筋与海水海砂混凝土的工程适用性,对海水海砂素混凝土以及含聚甲醛纤维（POM）的海水海砂混凝土进行同心拔出试验,考虑不同的混凝土龄期和混凝土保护层与钢筋直径比（c/d）,研究这两个变量对黏结性能的影响,以量化黏结-滑移关系。试验结果表明:复合钢筋因其良好的性能适用于海水海砂混凝土加固；早龄期混凝土与钢筋之间的峰值黏结应力τ_u受龄期影响明显,加入POM纤维的海水海砂混凝土表现为更好的延性和黏结性能；混凝土龄期对峰值黏结应力对应的滑移值s_u和上升段形状参数α的影响整体表现为龄期越大,滑移值s_u越小,上升参数α越小；混凝土龄期越大,下降段形状参数k越大；基于试验结果提出了考虑混凝土龄期影响的复合钢筋海水海砂混凝土黏结-滑移模型,该模型与试验结果具有较好的一致性。研究表明复合钢筋和纯海水海砂混凝土可以进行工程应用,且加入聚甲醛（POM）纤维改善后的混凝土具有更好的性能。

Abstract:

To investigate the engineering applicability of bimetallic steel bars and sea water sea sand concrete, concentric pull-out tests were carried out on sea water sea sand concrete and sea water sea sand concrete containing polyoxymethylene (POM) fibers. Considering different concrete ages and ratios of concrete cover c to bar diameter d(c/d), the influences of the two variables on bond performance were studied to quantify the bond-slip relationship. Test results show that bimetallic steel bar was suitable for the reinforcement of sea water sea sand concrete because of its good performance. The peak bond stress τ_u between the early-age concrete and the steel bar was significantly affected by the age, and the sea water sea sand concrete with POM fibers added had better ductility and bonding properties. The influence of concrete age on the slip value s_u corresponding to the peak bond stress and the shape parameter α of the ascending section was generally manifested as the larger the age was, the smaller the slip value s_u was, and the smaller the parameter α was. With increasing concrete age, the shape parameter k of the descending section was increased. Based on the test results, a bond-slip model of bimetallic steel bar and sea water sea sand concrete was proposed considering the effect of concrete age, and the model was in good agreement with the test results. The research indicates that bimetallic steel bar and pure sea water sea sand concrete can be used in engineering applications, and the concrete improved by adding POM fibers has better performance.