表面改性重组竹筋与竹炭砂浆界面粘结性能

Bond performance between surface modified bamboo scrimber bar and bamboo biochar mortar

为研究重组竹筋与竹炭砂浆的界面粘结性能,对共85个重组竹筋-竹炭砂浆试件进行中心拉拔试验,考虑了竹筋表面改性方法、等效直径、砂浆抗压强度、粘结长度等因素对界面粘结性能的影响。观察试件的粘结破坏形态,获取了各试件的粘结-滑移曲线、粘结强度和滑移量,分析了破坏机制,提出了界面粘结-滑移本构模型,得到了重组竹筋表面有效改性方法。结果表明:在不同初始条件下,拉拔试件存在3种破坏形态,分别为砂浆劈裂破坏、竹筋拉断破坏、竹筋拔出破坏,其中砂浆劈裂破坏最常见,破坏过程分为微滑移段、滑移段、下降段和残余段。竹筋表面经改性处理,其与砂浆界面粘结强度可提高13~46倍,界面粘结性能随竹筋粘结长度和等效直径的增大而降低,而砂浆强度对粘结性能的影响效果不显著。推荐使用粘砂和涂刷环氧砂浆两种方式对竹筋改性,在保证粘结性能的基础上,可改善养护过程中竹筋吸水膨胀导致与砂浆剥离,结构提前失效等问题。根据试验粘结-滑移曲线,得到经粘砂改性的重组竹筋-竹炭砂浆界面粘结-滑移本构模型,可准确预测重组竹筋与砂浆的界面粘结行为。经验证,该模型同样适用于试验中发生界面破坏的其他竹筋改性方法。

In order to study the bonding performance of bamboo scrimber bar-bamboo biochar mortar interface,pull-out tests were carried out on 85 bamboo scrimber bar-bamboo biochar mortar specimens.The effects of surface modification methods of bamboo bar,equivalent diameter of bamboo bar,compressive strength of mortar and bond lengths on the bond properties were also taken into consideration.The different bonding failure modes of the pull-out specimens were observed.The bond-slip curve,bonding strength and slippage were obtained.The failure mechanism was analyzed.A bond-slip constitutive model of bamboo scrimber bar-bamboo biochar mortar interface was established,and the effective surface modification method of bamboo scrimber bar was obtained.The results of the study show that there are three failure modes of the specimens under different initial conditions,including mortar splitting failure,bamboo bar tensile failure and bamboo bar pulled-out failure,among which mortar splitting failure is the most common.The failure process can be divided into micro-slip stage,slip stage,descending stage and residual stage.The bonding strength of the mortar interface can be increased by 13-46 times by modifying the surface of the bamboo bar.The interfacial bonding performance decreases with the increase of bonding length and equivalent diameter,and the effect of mortar strength on bonding strength is not obvious.It is recommended to modify the bamboo scrimber bar through the two methods of sticking sand and coating epoxy mortar.On the basis of ensuring bonding performance,it can improve the peeling of water absorption and expansion of bamboo bands during the maintenance process and the problem of the structure failing in advance.According to the experimental bond-slip curve,the bond-slip constitutive model of bamboo scrimber bar-bamboo biochar mortar treated by sticking sand was proposed.The bond-slip constitutive model can accurately predict the bond behavior between bamboo scrimber bar and mortar.After verification,the model is also applicable to the bonding interface destruction in the test under the other modification of bamboo.