CFRP筋与海水海砂混凝土黏结性能试验

为研究纤维增强塑料(FRP)筋与海水海砂混凝土(SWSSC)的黏结性能,选择4种碳纤维增强塑料(CFRP)筋材和2个强度等级的SWSSC,制作了72个试件进行拉拔试验,研究了黏结长度、筋材直径、混凝土强度和筋材表面处理等参数对黏结性能的影响; 开展了SWSSC试件与普通混凝土(NC)试件的对比试验,获取了试件的破坏形态和黏结应力-滑移曲线。基于ACI 440.1R-06公式提出了新的黏结强度计算公式。结果表明:CFRP筋与SWSSC的黏结破坏模式可以分为拔出破坏和劈裂破坏; 黏结强度随黏结长度的增加而逐步减小,且与(l_d/d_b)^-0.41呈近似关系(l_d为黏结长度,d_b为CFRP筋直径); 黏结强度随混凝土强度的提高而增大,但与CFRP筋材直径的相关性不明显; 表面喷砂能够显著提高CFRP筋与SWSSC的黏结性能,黏结强度增长系数可取为1.76; 相比于NC,CFRP筋与SWSSC的黏结强度有小幅度降低; 采用ACI 440.1R-06和CSA S806-02公式得到的预测结果与试验结果之间误差较大,均不适合直接用于估算CFRP筋与SWSSC的抗拔强度; 基于ACI 440.1R-06提出的新黏结强度计算公式计算结果与试验结果吻合程度较高,但其适用性需要进一步验证。

Experiment on Bond Performance of CFRP Bars in Seawater and Sea Sand Concrete

In order to study the bond performance of fiber reinforced polymer(FRP)bars in seawater and sea sand concrete(SWSSC), 72 specimens were made from four kinds of carbon fiber reinforced plastic(CFRP)bars and two strength grades of SWSSC. The effects of bonding length, reinforcement diameter, concrete strength and reinforcement surface treatment on bond performance were studied. The comparative tests of SWSSC specimens and normal concrete(NC)specimens were carried out, and the failure modes and bond stress-slip curves of SWSSC specimens were obtained. Based on the test results, a modified ACI 440.1R-06 method was proposed for predicting bond strength of CFRP bars with SWSSC. The results show that the bond failure modes of CFRP bars and SWSSC can be divided into pull-out failure and splitting failure; the bond strength gradually decreases with the increase of bond length, and has an approximate relationship with(l_d/d_b)^-0.41(l_d is the bond length, d_b is the diameter of CFRP bars). The bond strength increases as increasing of the compressive strength of SWSSC, while it is slightly influenced by the diameter of CFRP bars. The surface treatment of CFRP bar with coated by sand significantly improved the bond properties of CFRP bars with SWSSC. The bond enhancement factor could be taken as 1.76 in current study. Compared with NC, the bond strength between CFRP and SWSSC is slightly reduced; the error between the predicted results and the test results is large, which is not suitable for directly estimating the tensile strength of CFRP bars and SWSSC; based on ACI 440.1R-06 and CSA S806-02, the pull-out strength of CFRP bars and SWSSC cannot be directly estimated. The calculation results of the new bond strength formula proposed by ACI 440.1R-06 are in good agreement with the test results, however, the applicability of the method needs to be further investigated.