Preparation Of High Carbon Ferrochrome Slag Based Spinel-olivine Ceramic Aggregate And Its Service Performance In Deep Ground Environmen

The main mineral phases of high-carbon ferrochrome slag are spinel and olivine,which have broad application prospects in the high ground temperature(70-80 °C)and high salinity environment of deep buried tunnels in the west due to their good high temperature resistance,wear resistance and corrosion resistance.The presence of partially unreacted chromite and low melting point phase enstatite in high carbon ferrochrome slag is the key factor limiting its application in deep earth environment.This topic from their own physical and chemical properties of high carbon ferrochrome slag and deeply in western China environment,a new method for preparing Spinel-Olivine ceramic concrete aggregate by using high carbon ferrochrome slag is proposed.Based on the theoretical basis of the Mg O-Al2O3-Si O2 ternary phase diagram,the chemical composition of the high carbon ferrochrome slag based SpinelOlivine ceramic aggregate was designed,and the effects of different mineral phase ratios,sintering temperature and holding time on high carbon ferrochrome slag based Spinel-Olivine ceramic aggregate were systematically studied.The corrosion resistance of high carbon ferrochrome slag based Spinel-Olivine ceramic aggregate in the west of high earth temperature,high salinity environment and its influence on the structure of the transition zone of concrete interface are investigated,which providing a theoretical basis for the efficient value-added of high carbon ferrochrome slag and the selection of concrete aggregates in the west of deep earth environment.The main conclusions drawn from this topic include:(1)Based on Mg O-Al2O3-Si O2 ternary phase diagram,the design and prediction of the mineral phases of high carbon ferrochrome slag based Spinel-Olivine ceramic aggregate were realized.The ceramic aggregate with crystal phases of olivine and spinel were prepared with high carbon ferrochrome slag,industrial alumina and silicon dioxide as raw materials.When the content of high carbon ferrochrome slag was 77.6%,the compressive strength was281.1MPa,the water absorption rate was 1.4%,and the apparent density was 3100kg/m3.(2)The physical properties and crystal structure of high carbon ferrochrome slag based Spinel-Olivine ceramic aggregate are affected by sintering temperature and holding time.Considering the phase content,physical properties and energy consumption of high carbon ferrochrome slag based Spinel-Olivine ceramic aggregate,the optimal process parameters are sintering temperature 1500℃ and holding for 3h.(3)Appropriate increase of spinel content can significantly improve the corrosion resistance of high carbon ferrochrome slag based Spinel-Olidine ceramic aggregate.When the relative content of spinel is 40%,the strength attenuation coefficient is 3.6% after soaking in80℃ and 5%Na Cl solution for 180 days;The strength attenuation coefficient is 5.8% after soaking in 80℃ and 5% Na2SO4 solution for 180 days.And the strength attenuation coefficient is 9.6% after soaking at 80℃ and 5%Na OH solution for 180 days.(4)When the high carbon ferrochrome slag base Spinel-Olivine ceramic aggregate with a relative content of 40% spinel was soaked in 80℃ and 5%Na OH solution for 90 days,the leaching rates of Cr ions was: 0.331 mg/L,which is far lower than the relevant provisions of GB5085.3-2007.Using it as a coarse aggregate for concrete,the concrete was prepared and cured at 80 ℃ and 5% Na OH for 28 days.Compared with ordinary aggregate concrete,the width of interfacial transition zone is improved significantly,and the microstructure is more dense.It is suitable for concrete engineering in deep ground environment in western China.