Study On Modification Of Red Mud And Its Application In Lightweight Thermal Insulating Wall Materials

The red mud is the solid waste generated by the aluminum industry, its whole amount islarge and the comprehensive utilization rate is very low, mostly stored in the open air or landfill,which has taken up a lot of land resources and has caused serious environmental pollution.Therefore, the comprehensive utilization of red mud has become an urgent issue to solve inaluminum industry. In the paper, because of complex composition, poor activity, being difficultto self-coagulation and adhesion of red mud, the basic performance tests are made. And then thered mud foam material and sintered lightweight material are prepared on the basis of a varietyof modified means, and their application in lightweight thermal insulation wall materials areexplored.The chemical composition, phase composition, microstructure and particle sizedistribution of red mud are studied by means of X-ray fluorescence spectroscopy, XRD, SEM,particle size analysis. The results showed that the main chemical composition of red mud areSiO2, Al2O3, Fe2O3, CaO; the mainly phase are composed of quartz, silicon sulfide, hematite,water calcium zeolite and calcite minerals, which has complex mineral composition and is thematerial of integral phase relatively high stability.The effect of grinding time and calcination temperature on the performance of red mud isstudied, and the mechanism is explored. The results showed that, with the increasing grindingtime, the red mud over0.2mm square mesh sieve margin decreases and then increases, theoptimal grinding time is25min; The fluctuations of setting time and mechanical strength ofcalcined red mud is not great, and has no regularity. There are only a valley value of setting timeand a peak value of compressive strength at600°C.The added lime admixture significantly improves the workability of the paste. Withquicklime dosage increases, the setting time of red mud gradually decreases and the flexural,compressive strength are along with a constantly increasing trend. The optimal lime dosage is16%; The added fly ash admixture produce a water-reducing effect and increase plastic ofcementitious material, the setting time of red mud gradually reduced with the increasing fly ash,and the flexural, compressive strength increases with increasing fly ash. The fly ash optimalcontent is15%. To some extent, the setting time and mechanical properties of modified red mud have beenimproved, which initial setting time decreases by45.5h and final setting time decreases by44.4h, the3d flexural, compressive strength increases by4.1MPa and7.8MPa,7d flexural,compressive strength increases by7.8MPa and11.6MPa.In the experiment of red mud foam lightweight materials, the foaming agent, foamstabilizer, polypropylene fiber and waterproofing agent on properties of red mud foam materialare studied, and the mechanism is discussed. The results showed that the optimal foaming agentdosage is6%, foam stabilizer is1.5%, polypropylene fiber is0.6%, and waterproofing agentdosage is2.0%. The prepared red mud foamed lightweight material owns lightweight insulation,high strength, fire-resistance, water-resistance, etc. It can be substitution for organiclightweight thermal insulating wall materials, whose application can not only consume a largeamount of red mud, but also broaden type of lightweight thermal insulating wall materials.In the experiment of red mud sintered lightweight materials, the impact of porogen,calcination temperature and heating rate on the properties of red mud sintered lightweightmaterial and its sintering mechanism is explored. The results showed that the suitability of thepore-forming agent content is10%, and the optimum calcination temperature is1150°C, andthe preferred heating rate is6°C/min. The performance of developed red mud sinteringlightweight materials basically meet the requirements of standard so that the red mud sinteringlightweight materials have broad application prospects.