Experimental Research On The Behavior Of The Resistance Of Cracking And Crack Width Of Normal Section For Recycled Concrete Beams

The use of recycled aggregates in concrete opens a whole new range of possibilities in the reuse of materials in the building industry. The basic behavior of recycled concrete has been studied intensively, while there are few studies of behavior of recycled concrete members. Based on bending experiment of twenty-seven recycled concrete beams and three natural concrete beams, the difference of the behavior of the resistance of cracking and crack width between recycled concrete beams and natural concrete beams is compared in this paper. The factors of cracking moment and crack width of recycled concrete beams were investigated. The influence of concrete strength, reinforcement percentage, the diameter of bars and the thickness of cover on crack width of beams is analyzed. And a series of formulas of cracking moment and crack width of recycled concrete beams are proposed. The main conclusions are as following:1. When the values of the cubic compressive strength are the same, the spiltting tensile strength of recycled concrete is lower 30% than that of natural aggregate concrete and the elastic modulus of recycled concrete is lower 20% than that of natural aggregate concrete.2. The resistance of cracking of recycled concrete is lower than that of natural aggregate concrete. It will be not safe if the formula of cracking moment of natural aggregate concrete is used on recycled concrete beams.3. The cracking development of recycled concrete beams is more complex. Exceptional cracks of breaking off, converging or branching off often appear in recycled concrete beams. It was shown that the crack of recycled concrete beams is more random and discrete.4. The crack spacing of recycled concrete beams is less than that of natural aggregate concrete. The crack width of recycled concrete is not larger than that of natural aggregate concrete, with some are even less.5. The reinforcement percentage is the main influence factor on crack width of recycled concrete beams. The crack width decreases with the increase of reinforcement percentage. The more the thickness of cover is, the more the crack width is. The influence of concrete strength on the crack width is not obvious.