Test of frost resistance for steel fiber rubber recycled concrete

In order to make waste concrete and recycled rubber apply in concrete engineering in northern region, the effects of recycled coarse aggregates content, strengthening method of recycled coarse aggregates, content of steel fibers as well as content of rubber on compressive strength and frost resistance of steel fiber rubber recycled concrete (C45) were investigated by orthogonal design tests. Through the scanning electron microscopy and screw CT scanning technique, the macro and micro structure and their effect mechanisms on frost resistance of steel fiber rubber recycled concrete were analyzed. The results show that the content of rubber particles is a prominent factor affecting the gas content, compressive strength and relative dynamic elastic modulus of recycled concrete, and the content of recycled coarse aggregates is also an important factor affecting the relative dynamic elastic modulus and strength loss rate. In addition, the compressive strength of concrete increases slowly with the increase of steel fibers, and strengthening method of aggregates has almost no effect on the performance of concrete. The crack width between rubber particles and mortar interface falls into 5-55 μm. Compatibility between rubber particles and mortar interface is a little bad. When the content of rubber particles is above 20% (volume ratio between rubber particles and sands), the inner hole number of concrete will rise with the increase of rubber particle content. The compressive strength of steel fiber rubber recycled concrete will drop, and frost resistance will also decrease.