| According to the concept of "building energy conservation and green building development",copper slag is used as fine aggregate in high performance concrete(HPC).According to the design rules of high-performance concrete,the mix ratio of HPC was designed and appropriate amount of graphite and steel fiber was added to prepare HPC with excellent mechanical properties and thermal conductivity,which was organically combined with the green building energy-saving-ground source heat pump energy pile system to conduct heat transfer simulation research.Considering the strength,stability,heat transfer efficiency and other factors of the energy pile,the material of the energy pile HPC was selected,and the influence of the substitution rate of copper slag on the fluidity,compressive resistance,flexural resistance and thermal conductivity of the HPC mortar was investigated for the two cases of steel fiber and non-steel fiber.The main research contents and conclusions are as follows:(1)investigate the influence of copper slag substitution rate on the compressive and flexural properties of HPC.The compressive test of copper slag concrete specimen shows that with the increase of the substitution rate of copper slag,the destruction degree of copper slag concrete increases,and the binding force of the specimen ends decreases,and the crack resistance of steel fiber reinforced copper slag concrete is excellent,but with the increase of the substitution rate of copper slag,the crack resistance of steel fiber reinforced copper slag concrete specimen decreases.By adding steel fiber into concrete,the substitution rate of copper slag as fine aggregate instead of sand and stone is improved.For the concrete beam with copper slag,its bending strength decreases with the increase of the substitution rate of copper slag,while for the concrete beam with steel fiber copper slag,when the substitution rate of copper slag is 40%,its bending strength and damage deflection are the largest.When the replacement rate of copper slag is less than 45%,steel fiber reinforced copper slag concrete beams have better flexural performance than steel fiber reinforced concrete beams.(2)in the range of 30%~50% substitution rate of copper slag,the influences of copper slag substitution rate,steel fiber incorporation and graphite incorporation on the compressive resistance,bending resistance and thermal conductivity of HPC were investigated based on the orthogonal experimental method.The results showed that the compressive strength and flexural strength of HPC increased with the addition of steel fiber and decreased with the addition of graphite,while the thermal conductivity of HPC increased with the addition of copper slag,steel fiber and graphite,but graphite had the most significant influence on the thermal conductivity of HPC.(3)build the heat transfer model of single u-shaped heat exchange tube energy pile of HPC energy pile system.Using FULENT software to simulate the energy pile heat exchanger,analyzes the 3 d steady state conditions,HPC energy of fluid-solid coupling heat transfer characteristics of pile,import and export temperature difference and level by two dimension heat diffusion degree and the comparative analysis of conventional quartz sand HPC energy pile,copper slag HPC pile,graphite HPC energy heat conduction rule and heat transfer performance,the results show that graphite HPC energy compared with conventional quartz sand HPC pile pile horizontal heat transfer rate increased by 49.7%,inlet and outlet temperature in thermal efficiency is improved by 12.9%,has higher heat transfer performance.In conclusion,compared with ordinary energy piles,copper slag fine aggregate HPC energy piles can effectively improve heat transfer efficiency and mechanical properties of the structure.Therefore,the research results in this paper can provide technical support for the preparation of HPC with high strength and high thermal conductivity using copper slag,and the application of such HPC in the production practice of energy pile. |
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