Adhesion Performance of Steel Bars in Recycled Concrete with Nano-materials in Cold Environments

This work investigated the adhesion performance of recycled concrete with nano-SiO2 and nano-Al2O3 and steel bars in cold environments through freeze‒thaw cycle tests and tensile tests. The results show that the nanomaterials and number of freeze-thaw cycles have no significant effect on the damage morphology of the sample, but the adhesion strength and steel bar slip of the sample are considerably affected by the nanomaterials and number of freeze-thaw cycles. After the addition of the nanomaterials, the adhesion strength increased by 10.4 % (11.2 %), and the steel slip increased, by 17.3 % (16.8 %). The impact of freeze-thaw cycles on adhesion strength and adhesion slip is significant. The adhesion strength decreases by up to 40.8 % after 55 freeze-thaw cycles, and the slip of the steel bar increases by up to 101.9 %. In addition, an adhesion performance model of recycled concrete and steel bars mixed with nanomaterials in cold environments is established. The strengthening mechanism of nanomaterials and the mechanism of freeze-thaw damage is revealed. This study provides a basis for the practical application of recycled concrete technology and promotes the recyclable use of building materials.