自密实包浆再生混凝土早期塑性开裂试验研究

为了研究包浆再生粗骨料对自密实再生混凝土早期塑性开裂性能的影响,通过正交试验得出混凝土相对最优的配比方案。在此基础上,控制其他因素不变,以包浆水泥强度等级为单一变量,采用平板约束法,进行混凝土早期塑性开裂试验。结果表明:再生粗骨料经过包浆后,混凝土抗压与抗折强度均得到一定的提高;再生混凝土单位面积总开裂面积约为普通混凝土的1.5倍,经过水泥包浆后,开裂面积有了不同程度的减少,与未包浆的相比,32.5R、42.5R、52.5R水泥包浆的混凝土开裂面积分别减少了11.1%、25.1%、13.1%,其中42.5R水泥的包浆效果最好。结合微观电镜试验发现,骨料包浆可加强混凝土的界面过渡区,提高其抗开裂能力。

Experimental Study on Early Plastic Cracking of Self-compacting Recycled Concrete with Aggregates Coated with Cement Slurry

The aim of this study is to investigate the influence of recycled aggregate with surface-coating cement slurry on the early plastic cracking performance of self-compacting recycled concrete. On the basis of optimal mix proportions obtained from orthogonal test, we conducted early plastic cracking test via slab test with the strength level of surface-coating cement as single variable and other factors remaining unchanged. Test results demonstrate that after the surface-coating of recycled coarse aggregate, the compressive strength and flexural strength of concrete both improved, and the crack area also declined to different degrees. The total crack area of recycled concrete per unit area is about 1.5 times of that of ordinary concrete; and the crack area of concrete with 32.5R, 42.5R and 52.5R cement coating reduced by 11.1%, 25.1% and 13.1% compared with that of ordinary concrete, respectively, of which 42.5R cement boasts the best surface-coating effect. SEM test also shows that the surface-coating slurry of aggregate strengthens the interface transition zone of concrete and enhances its cracking resistance.