Research On The Mechanism And Application Technology Of Red Mud On The Bottom Base Layer And Base Layer Of Highway

Red mud is the industrial waste residue produced in the process of preparing alumina through bauxite,China’s existing pile stock exceeds 1 billion tons,and at an annual rate of 100 million tons of growth,and the utilization rate is only about 5.5%,domestic and foreign scholars from the chemical and physical properties of red mud,the application in highway engineering mainly focuses on cement red mud concrete,filling roadbed,modified red mud base layer,etc.,but at present there is still a relatively lack of environmental protection characteristics,mechanism of action and long-term performance and fatigue life analysis of red mud in highway engineering applications.This paper uses the red mud of Xingyang Stockyard of Chalco Henan Branch as raw material,determines the main chemical composition,micromorphology,mineral composition,particle size characteristics and environmental protection characteristics of red mud through experimental analysis,analyzes the physical and chemical basis of red mud for highway engineering,analyzes the mechanism of action of red mud,cement and lime through scanning electron microscopy,loss on ignition analysis and DSC-TGA,and takes the unconfined compressive strength,shrinkage characteristics,water stability,springback modulus,fatigue performance and estimated fatigue life under load as the index.Through indoor experiments,the pavement performance of cement lime red mud stabilized soil and cement red mud stabilized gravel was studied,and the reasons for the change of road performance were analyzed from the perspective of hydration product generation by loss on ignition test,and the main conclusions were:(1)There are more active substances Al2O3,Si O2,Ca O,etc.in red mud,the total amount is close to 50%,the red mud particles are fine,the clay content is 26.57%,the specific surface area is large,the plasticity is strong,the properties are close to silty clay,the radioactivity meets the requirements of the specification,cement,Lime can significantly reduce the toxicity of red mud leaching and make it meet environmental standards;(2)30% moisture content cured for 28 d cement red mud,lime red mud is more dense than the original red mud,after loss of ignition analysis,there are red mud and cement,lime reaction hydration products are generated,by DSC-TGA weight loss rate analysis at different temperatures,the hydrated calcium silicate,calcium aluminate hydrate,calcium hydrated calcium aluminate hydrate are significantly increased,combined with the existing research results,analyze the volcanic ash reaction mechanism of red mud and calcium hydroxide;(3)Red mud incorporation can significantly increase the early strength of cement lime red mud stabilized soil,but will reduce its later strength growth rate,reduce its dry shrinkage strain and water loss rate,reduce its water stability,cement lime red mud stabilized soil The best mixing ratio is: cement: lime: soil: red mud = 4:4.8:84:27.2,7d,28 d,90d unconfined compressive strength reaches 2.3MPa,3.2MPa,4.4MPa,compared with 7.2% red mud content increased by 15% and 6.7%,4.8%,dry shrinkage strain reduced by 8.8%;The loss on ignition has a positive correlation with strength,and there is an optimal ratio of red mud to cement and lime,which is not conducive to the formation and strength growth of hydration products.(4)With the increase of red mud content,the unconfined compressive strength of cement red mud stabilized crushed stone immersion without lateral limitation decreased,the splitting strength of water immersion first increased and then decreased,the water stability decreased,and the estimated fatigue life under load first increased and then decreased;When the red mud content is 10%,its unconfined compressive strength is slightly reduced,5.1MPa,the 7d splitting strength is 0.47 MPa,compared with the red mud content is 0,it increases by 6.8%,the later strength growth rate is reduced,the rebound modulus is slightly reduced,the bottom tensile stress of the cement red mud stabilized crushed stone base layer is slightly reduced under load,when the red mud content is 10%,the estimated fatigue life under the load increases by 2.3%,and the red mud content is 20%.The estimated fatigue life under load increased by 9.6%;When the red mud content is about 10%,it has good water stability,high strength and fatigue life.It is believed that red mud can be applied to highway construction,and an appropriate amount of red mud can improve some of its road performance,reduce highway cost and harm to the environment.