Experimental Research On Mechanical Properties And Fracture Properties Of Steel Fiber Reinforced Recycled Concrete

With the rapid development of the construction industry, the value of construction wastes is also soaring to unprecedented to heights. Besides the handling charges construction waste is very high, it also causes a lot of environmental problems and social harmful effects. Recycled concrete is one of new type concrete that mixed with recycled aggregate at a certain proportion after cleaning, crushing, grading wasted concrete. Recycled Concrete Technology not only may resolve the environment pollution produced by the waste concrete, but also may save crude aggregates resource, and bring the prominent social benefit, economic benefit and environmental benefit. It is a sustainable development road that can save resources and energy, alleviate the earth environment load and support the ecosystem balance. Steel fibers were added to Recycled concrete and the purpose of the test is to improve the performance of recycled concrete through the enhancement of steel fibers. The main achievements are as follows:1. By the compressive strength test of 90 cube specimens of 150mm×150mm×150mm,12 of 100mm×100mm×100mm,12 of 200mm×200mm×200mm, the effects of fibers of different types, volume fractions of steel fiber, the pretreatment ways of recycled coarse aggregate and dimensional effect on compressive properties of steel fiber reinforced recycled concrete were explored. The influence coefficient of Milling Steel Fiber to compressive strength of recycled concrete considering water absorption of recycled coarse aggregate, the strength conversion coefficients of compressive strength and the calculating formulas of compressive strength were built.2. By the splitting tensile test of 90 cube specimens of 150mm×150mm×150mm,12 of 100mm×100mm×100mm,12 of 200mm×200mm×200mm, the effects of fibers of different types, volume fractions of steel fiber,the pretreatment ways of recycled coarse aggregate and dimensional effect on splitting tensile properties of steel fiber reinforced recycled concrete were explored. The influence coefficient of Milling Steel Fiber to splitting tensile strength of recycled concrete considering water absorption of recycled coarse aggregate, the strength conversion coefficients of splitting tensile strength and the calculating formulas of splitting tensile strength were built.3. By the flexural test of 90 beams of 100mm×100mm×400mm, the effects of fibers of different types,volume fractions of steel fiber and the pretreatment ways of recycled coarse aggregate on bending properties were explored. The influence coefficient of Milling Steel Fiber to compressive strength of recycled concrete considering water absorption of recycled coarse aggregate and the calculating formulas of flexural strength were built.4. The relations of compressive strength with splitting tensile strength, compressive strength with flexural strength and splitting tensile strength with flexural strength were analyzed and corresponding formulas were put forward.5. By the three-point bend beam test of 150 incision curved beams of 100mm×100mm×515mm, the effects of fibers of different types, volume fractions of steel fiber and the pretreatment ways of recycled coarse aggregate on the fracture properties of steel fiber reinforced recycled concrete were explored. The difference of the fracture properties between steel fiber reinforced recycled concrete and natural steel fiber reinforced concrete were explored. The calculating formulas of Fracture Toughness(K_IC), Fracture Energy (G_f), Critical Crack Mouth Opening Displacement as well as Critical Crack Tip Opening Displacement(CTOD_C) of steel fiber reinforced recycled concrete were put forward.