高温后型钢再生混凝土界面黏结性能试验研究

Experimental Research on Bond—slip Behavior between Shape Steel and Recycled Coarse Aggregate Concrete after Elevated High Temperatures

为了研究高温后型钢再生混凝土界面黏结性能,对20个型钢再生混凝土试件进行了高温后静力推出试验,设计变化参数包括再生粗骨料取代率和历经最高温度。试验获取了试件加载端与自由端的荷载-滑移曲线及特征点参数,并基于试验数据,深入分析了试件高温前后的物理力学性能变化、受力破坏过程以及各变化参数对型钢再生混凝土高温后黏结滑移性能的影响规律,探讨并提出了高温后型钢再生混凝土黏结强度计算公式。研究结果表明:加载端和自由端荷载-滑移曲线相似,但加载端比自由端滑移更早;随着历经最高温度的升高,试件表面颜色由深变浅,历经温度超过400℃后,试件表面混凝土出现裂缝,并且历经温度越高表面裂缝越多、越宽,随温度的升高,试件黏结强度显著降低;当0%≤r≤50%时,黏结强度不断增大,当50%<r≤100%时,黏结强度有所降低,且再生混凝土试件的黏结强度比普通混凝土试件大;型钢再生混凝土高温黏结损伤发展过程与历经温度有关,历经温度越高,其黏结损伤发展较迟缓,同时,历经最高温度越高,试件的耗能能力越强;高温后型钢再生混凝土黏结强度的计算公式被提出,且计算值接近试验值。

In order to study the bond-slip behavior between steel and recycled coarse aggregate concrete after exposure to high temperatures,a total of 20 steel reinforced recycled aggregate concrete(SRRAC)specimens were designed with recycled coarse aggregates replacement percentage and maximum temperatures as the variation parameters,and the static push-out test after simulated fire was carried out. The load-slip curves at the loading end and free end of the specimens and characteristic point parameters were measured before and after high temperature. The physical and mechanical properties,the failure process and the impact of various variation parameters on the bond-slip behavior of SRRAC exposed to high temperature were deeply analyzed based on test data. What’s more,the calculation formula for bond strength of SRAC subjected to high temperature was discussed and put forward. The results show that the load-slip curves at the loading end and the free end are similar,but the loading end slips earlier than the free end. As the maximum temperature rises,the surface color of specimens is getting lighter. When the temperature exceeds 400°,cracks appear on the surface of specimens,and the higher the temperature,the more and wider the surface cracks are. With the increase of temperature,the bond strength of specimens decreases significantly. When 0%≤r≤50%,the bond strength increases continuously and when 50%<r≤100%,the bond strength decreases. The bond strength of the recycled concrete specimens is larger than that of the ordinary concrete specimens. The development process of bond damage of SRRAC at high temperatures is related to the experiencing temperature,the higher the temperature,the slower the development of bond damage. At the same time,higher maximum temperature leads to stronger energy dissipation capacity of the specimens. The calculated value obtained by the bond strength formula of SRRAC subjected to high temperatures is in good agreement with the experimental one.