Study On Preparation And Properties Of Controlled Low Strength Materials Based On Red Mud

Controlled low strength material（CLSM）,as a backfill material widely recognized in the world for the purpose of using recycled aggregate,has advantages over traditional backfill materials:wide sources of materials,simple construction site requirements,multiple performance can be met through mix design,and less manpower and material requirements.With the development of society,various industrial solid wastes are piled up in large quantities and difficult to be effectively treated.It is an effective way to prepare Controlled low-strength materials.Considering that red mud is a kind of solid waste with large stacking capacity,high utilization difficulty,high treatment cost and great damage to the environment,it can be used with other auxiliary raw materials to prepare Controlled low-strength materials through design and optimization of the mix ratio,so as to increase the consumption of red mud and drive the use of other solid waste materials,and achieve the purpose of improving social and economic benefits and environmental benefits.In view of a series of problems caused by red mud,from the perspective of social and economic benefits and green sustainable development,this paper takes red mud as the main raw material,fly ash and mineral powder as auxiliary materials,NaOH and Na₂Si O₃as alkali activator to prepare Controlled low strength materials,and optimizes the material ratio,and studies the working and mechanical properties of materials with different mixing ratios of red mud,fly ash,mineral powder and additives.The main conclusions are as follows:（1）By controlling the amount of mineral powder to be 10%unchanged,the total amount of red mud and fly ash to be 90%unchanged,and the dispersant of 0.75%（external mixing method）on the basis of adaptability,the optimal water-solid ratio of the system designed in this paper is 0.35.（2）Under the same mix ratio,CLSM was prepared to analyze and compare the fluidity of red mud,fly ash and mineral powder system excited by red mud alkalinity,NaOH and Na2Si O3 respectively.By studying the change of the amount of red mud from 20%to 70%,the fluidity can be controlled by controlling the amount of red mud.The smaller the amount of red mud,the higher the fluidity.In addition,the problem of excessive bleeding rate of CLSM can also be adjusted by changing the mixing sequence of materials.The more evenly the dispersant is mixed with materials with high cohesion,the more evenly it is dispersed,and the lower the bleeding rate.（3）By studying the unconfined compressive strength of each group with45%～70%red mud content,the unconfined compressive strength of the prepared CLSM can be adjusted in the system of red mud,fly ash and mineral powder by controlling the amount of activator and the amount of red mud.The higher the amount of red mud,the lower the compressive strength;The higher the content of alkali activator,the higher the strength.（4）Through microscopic characterization,its internal structure was analyzed,and its hydration mechanism was identified as four stages:dissolution stage,hydrolysis stage,polycondensation stage,and curing stage.After this hydration process,most of the final products were interpenetrated and cemented C-S-H gel and AFt crystals,providing support for strength.（5）Red mud based CLSM has general dry and wet resistance,poor acid resistance,and excellent alkali resistance and salt resistance.