Experimental Study On The Influence Of The Recycled Concrete’s Mechanical Properties After High Temprature And Then Under A Low Temperature

As a kind of green material, Recycled Concrete has an important social and economic value. The mechanical properties of Recycled Concrete under normal temperature and a part of mechanical properties of Recycled Concrete under high temperature are researched at home and abroad, and has achieved fruitful results, that laid a soild foundation to the Recycled Concrete’popularization and application in engineering practice. According to our country’s national conditions, in winter, the outdoor temperature of the north area of China is generally too low, and the incidence of fire across our contry is on the rise year by year. This paper studies the influence of the Recycled Concrete’s mechanical properties after high temprature and then under a low temperature.(1) The test made 42 groups 100mm×100mm×100mm blocks and 21 groups 150mm×150mm×300mm blocks, water laminating curing 28 d and 80 d of natural drying, and then heat the blocks to 200℃, 400℃, 600℃, using nature and water to cool the blocks, when they cool to 20℃, freeze them in 0℃,-20℃. Observeing the damage form of strength test pilot found that the damage form of blocks appear crisp fragile in the cube compressive strength test; in the axial compressive strength, with the temperature depline, the crack development speed slow; in the splitting tensile strength, the blocks form at least one mainly through crack damage. The results showed that low temperature has effect on the mechanical properties of the Recycled Concrete.(2) Study the effect of the cooling ways when the low temperature is same, natural cooling Recycled Concrete’s cube compressive strength, axial compressive strength and splitting tensile strength are higher than water cooling.(3) Study the effect of the low temperature when the cooling way is same, under the natural cooling, the low temperature has no effect on the Recycled Concrete’s cube compressive strength; under water cooling, with the deline of the low temperature, the Recycled Concrete’s cube compressive strength increase. Under 200℃ and water cooling and-20℃, the Recycled Concrete’s cube compressive strength and splitting tensile strength are increase, significantly.(4) Established a relationship between the cubic compressive strength and temperature, the cooling way and the low temperature, and the relationship between the cube compressive strength and axial compressive strength, and splitting tension strength.