Design Of Red Mud-based Cementitious Material And Its Performance Research When Used As Road Base Material

Red mud is a byproduct of the refining of bauxite into alumina,it is difficult to use,and may cause serious impact on the environment.Red mud stockpiling took up a lot of land,and its maintenance cost is high.In addition,with high content of alkali and heavy metal ions,the leaching agent of red mud may permeate through soil land and pollute underground water system,which affect the health of the residents.Therefore,an effective way to reduce red mud storage extremely urgent.In this study,to solve red mud storage problem,the Red mud-based cementitious material was prepared by adding lime powder and FGD gypsum to the main raw materials（red mud and fly ash）.First,through mixture ratio design,we get optimal ratio of red mud-based cementitious material;Then,we research the mechanical properties,penetration performance,stability,durability by modern test methods（Microcalorimeter、XRD、FTIR、TG-DSC、MIP、SEM）.Finally,not only leaching liquid of Na⁺ion and heavy metal ion dissolution characteristics of the Red mud-based cementitious material were analyzed,we also explored the stabilizing way of Na⁺ion and heavy metal ions preliminarily.The research results show that:（1）With the increase of red mud,the compressive strength and flexural strength of red mud-based cementitious material also increases,but when the content more than 60%,the mechanical properties of the material began to fall.（2）Lime powder content could improve the mechanical properties,penetration performance and durability significantly.Although the performance of red mud-based cementitious material increased with the dosage increase of lime powder,but which is obvious.（3）Adding FGD gypsum also affect the performance of the material,especially,it could improve the material’s stability because its“expansion effect”.But the dosage of FGD gypsum should not be too high,otherwise it will cause performance degradation or even strength reduction.（4）Based on alkali-activated and sulfate-activated theory,a high performance and low price red mud-based cementitious material can be got,when mix 5%lime with 5%of FGD gypsum together.（5）We study the dissolution regularity of Na⁺ions and heavy metal ions of red mud-based cementitious material.Found that adding lime powder and FDG gypsum can reduce the dissolution of Na⁺ion and heavy metal ions effectively,and when lime dosage increase,Na⁺ions and heavy metal ion concentration is reduced,but when FGD gypsum dosage increase,Na⁺ions and heavy metal ion concentration changing is not obvious.（6）Through changing fly ash of red mud-based cementitious material,we found that the lower Ca content of fly ash have better ability to solidify Na⁺ions.In addition,we also found that Pb²⁺、Cu²⁺、Cr³⁺、As³⁺can be effective curing by adding Mg-Al-CO₃ LDHs.