再生混凝土冻融循环后与钢筋拉拔试验研究

Pullout tests research on steel bars and recycled concrete after freeze-thaw cycles

对经过0次、50次、100次、150次、200次冻融循环的再生混凝土（粗骨料取代率100%）进行拉拔试验研究,以钢筋直径16mm和20mm、锚固长度5d和10d为变动因素,分析冻融循环次数对再生混凝土立方体抗压强度、极限拉拔荷载和极限黏结应力的影响,并采用钢筋开槽内贴应变片的方法,研究了不同冻融循环次数后钢筋锚固段内钢筋应变、局部黏结应力和极限黏结应力平均值-滑移的分布规律。结果表明,冻融循环后再生混凝土抗压强度下降,极限荷载和极限黏结应力平均值随着冻融循环次数的增加而逐渐减小;随着冻融循环次数的增加,荷载作用下钢筋应变沿锚固长度的变化曲线趋于平缓,局部黏结应力首先在加载端附近出现应力峰值,沿锚固长度逐渐向自由端传递,总体呈现减小的趋势。

The pullout test research was carried out on recycled concrete containing 100% of recycled coarse aggregate under 0,50,100,150 and 200 times of freeze-thaw cycles. Anchorage lengths of 5 d and 10 d of steel bar with diameters of16 mm and 20 mm were taken as two variable factors to analyze influences of times of freeze-thaw cycles on cubic compressive strength,ultimate pullout load and ultimate bond stress. By embedding strain-gauge inside steel rebar,the steel bar strain,local bond stress and distribution laws of ultimate average bond stress-slip in steel bar anchorage section after different freeze-thaw cycles were studied. The test results show that the compressive strength of recycled concrete descends during the process of freeze-thaw cycle,and the ultimate load and ultimate average bond stress decrease with the increase of freeze-thaw cycles. The strain curve is flat with the increase of freeze-thaw cycles along the anchorage position under the breaking load. The local bond stress peak first appears near the loading end,and gradually moves to the free end,featuring the trend of decrease in general.