BFRP筋与分级粒径河砂ECC粘结滑移性能试验研究

通过玄武岩纤维增强复合材料(BFRP)筋/高延性水泥基复合材料(ECC)的中心拉拔试验,分析了分级粒径ECC和BFRP筋表面形式及直径对BFRP筋/ECC粘结性能及粘结-滑移曲线的影响。结果表明,BFRP筋/ECC的破坏模式分为BFRP筋拔出破坏和BFRP筋拉伸破坏。选取BFRP筋/ECC粘结-滑移曲线中的残余波浪段各峰值应力点,采用拟合直线斜率的绝对值|k|表征ECC对BFRP筋横肋的磨损程度,当|k|值≥0.144时,BFRP筋横肋会被完全磨损,当|k|值＜0.144时,BFRP筋横肋会被磨损至与填充其凹陷的ECC齐平。BFRP筋/ECC的平均粘结强度随骨料粒径的变化并不显著,分级粒径ECC可使BFRP筋/ECC的平均粘结强度提高3.2%~9.6%,采用骨料粒径为0.15~0.3 mm的BFRP筋/ECC粘结性能最优。BFRP筋的直径越大,BFRP筋/ECC的平均粘结强度越小,BFRP筋直径为12 mm的BFRP筋/ECC平均粘结强度与BFRP筋直径为8 mm、10 mm的BFRP筋/ECC相比降低分别约8.2%、4.4%。采用浅螺纹BFRP筋的BFRP筋/ECC,平均粘结强度下降83.7%,但其整体粘结应力变化较为平稳,对ECC和BFRP筋的损伤程度均最小。减小BFRP筋直径、ECC骨料粒径,或BFRP筋/ECC自由端处BFRP筋的肋深,有助于提高BFRP筋/ECC的粘结性能及稳定性。

Experimental Study on Bond-Slip Performance Between BFRP Bars and ECC with Graded Particle Size River Sand

Based on the center pull-out test of basalt fiber reinforced polymer bars/engineering cementitious composites (BFRP bars/ECC), the effects of graded particle size of ECC, surface treatment and diameter of BFRP bars on bond performance and bond-slip curve of BFRP bars/ECC were analyzed. The results show that the failure modes of the specimens are BFRP bar pull-out failure and BFRP bar rupture failure. The BFRP bars/ECC bond-slip curve is wave type. The peak point of each wave is selected and an absolute value of linear slope |k| is fitted to characterize the wear degree of ECC and tear degree of BFRP transverse rib. If the |k| ≥ 0.144, transverse rib of BFRP bar is deemed to wear completely, and if the |k| < 0.144, the transverse rib of BFRP bar is deemed to worn and flush with the ECC. The average bond strength of BFRP bars/ECC does not change significantly with the particle size. The graded particle size of ECC increases the average bond strength of BFRP bars/ECC by 3.2%~9.6%. The BFRP bars/ECC with the aggregate particle size of 0.15~0.3 mm has the best bond strength. The larger the diameter of BFRP bars is, the smaller the average bond strength of BFRP bars/ECC is. The average bond strength of BFRP bars/ECC with the diameter of 12 mm is about 8.2% and 4.4% lower than that of BFRP bars/ECC with the diameter of 8 mm and 10 mm. The average bond strength of BFRP bars/ECC with shallow thread BFRP bars decreases by 83.7%, but the overall bond stress changes stably, and the failure degree to both ECC and BFRP bars is minimal. Reducing the diameter of BFRP bars, ECC aggregate particle size, or the rib depth of BFRP bars at the free end of BFRP bars/ECC can improve the bond performance and stability of BFRP bars/ECC.