海水海砂再生混凝土与环氧涂层钢筋黏结性能

采用中心拔出试验对环氧涂层钢筋海水海砂再生混凝土的黏结性能进行了试验研究。考虑不同混凝土类型（普通混凝土、再生混凝土、海水海砂再生混凝土）、设计强度等级（C20、C25）、黏结长度（3d、5d、8d，d为钢筋直径）、钢筋种类（普通钢筋、环氧涂层钢筋）和保护层厚度（67、42mm）等参数进行拔出试验，研究其黏结强度的变化规律。结果表明：环氧涂层钢筋与海水海砂再生混凝土之间黏结性能较普通钢筋混凝土的略有降低，再生粗骨料的加入降低了试件的黏结强度，而海水、海砂减小了再生粗骨料对黏结强度的不利影响；黏结强度随着混凝土强度和保护层厚度增加而显著提高，随着黏结长度增长而降低；环氧涂层钢筋与海水海砂再生混凝土黏结滑移曲线与普通钢筋混凝土试件的相似，分为微滑移、滑移和下降三段；环氧涂层钢筋使得曲线曲率增加、下降段较缓，而海水、海砂影响与之相反。拟合得到了环氧涂层钢筋与海水海砂再生混凝土间黏结强度计算公式，计算值与相关试验数据吻合良好。

Study on bond between seawater sea sand recycled concrete and epoxy-coated steel bars

The bond behavior between seawater sea sand recycled concrete (SSRC) and epoxy-coated steel bars (ECSB) was studied through pull-out tests. The main parameters were concrete type (natural aggregate concrete, recycled aggregate concrete and SSRC), concrete strength (C20 and C25), bond length (3d, 5d and 8d), reinforcement type (ordinary steel bars and ECSB) and concrete cover thickness (67 mm and 42 mm). The bond strength of specimens were analyzed. Test results indicate that the bond strength of SSRC to ECSB is slightly lower that of natural aggregate concrete to ordinary steel bars. It is found that the recycled coarse aggregate decreased while seawater and sea sand increased the bond strength. The bond strength increases with the increase of concrete strength and cover thickness and the decrease of bond length. The bond-slip curve of SSRC to ECSB is similar to that of ordinary reinforcement concrete. It could be divided into micro-slipping, slipping and declining stages. Installation of ECSB increases the curvature while decreases the decline of the bond-slip curve. However, sea sand and seawater decreases the curvature of the curve and increases the decline of the curve. Finally, the formula for the bond strength was proposed. The calculated values are in good agreement with the measured values.