Influence of transverse rebars on bond between steel reinforcement and cellular concrete with very low compressive strength

Abstract Cellular concrete is a lightweight concrete obtained by aerating agent, which produces air-voids into the mixture. This work deals with bond between cellular concrete and steel rebars. Pull-out tests of 4,2 mm diameter rebars partly immersed into concrete cylinders were made. Concrete unit weight variation and setting of a transverse rebar into the concrete cylinder center constitute the variables of the work. Three types of mixture were prepared: one without aerating agent (with a dry unit weight of 2255 kg/m3), and two with different aerating agent rates (with a dry unit weight equal to 1565 and 1510 kg/m3). The study revealed the large decrease of bond stress between 4,2 diameter rebars and cellular concrete, due to concrete unit weight reduction. Transverse rebar introduced into concrete cylinder center increased the ultimate pull-out force of the test: the gain of bond produced by the transverse rebar grew up when the cellular concrete unit weight had been reduced. Therefore, special anchorages (not exclusively straight), permitting bond improvement between cellular concrete and rebars could be a solution to improve the mechanical performance of cellular concrete.

摘要 泡沫混凝土（Cellular Concrete）是通过掺入引气剂在混合料中引入气孔而制备的轻质混凝土。本研究聚焦于泡沫混凝土与钢筋之间的粘结性能，开展了将直径4.2mm钢筋部分埋入混凝土圆柱试块的拉拔试验。本研究的试验变量包括两项：混凝土干表观密度变化，以及在混凝土圆柱中心增设横向钢筋。共制备了三种配合比的试件：一组未掺加引气剂，其干表观密度为2255 kg/m³；另外两组分别采用不同掺量的引气剂，干表观密度分别为1565 kg/m³与1510 kg/m³。研究结果表明，随着混凝土干表观密度降低，直径4.2mm钢筋与泡沫混凝土之间的粘结应力大幅下降。在混凝土圆柱中心增设横向钢筋可提升试件的极限拉拔承载力；且泡沫混凝土干表观密度越低，横向钢筋带来的粘结强度提升幅度越大。因此，采用可改善泡沫混凝土与钢筋间粘结性能的专用锚固构造（不限于直杆形式），可作为提升泡沫混凝土力学性能的可行方案。