Synergistic Utilization Of Bauxite Residue Solid Waste As Cementitious Materials

Traditional construction activities have severe negative environmental impacts.The production of Portland cement（the most common binder in concrete）is an energy-intensive process that accounts for a significant portion of global CO₂ emissions and other greenhouse gas.Furthermore,various industrialization activities,such as metallurgy and chemical production,also pose tremendous greenhouse gases emissions and landfilling problems of the by-produced solid waste materials.Therefore,in the process of infrastructure construction,the use of environmental-friendly cementitious materials to achieve a great degree of green construction industry is the only way to reduce the consumption of natural resources and energy,and is essential for achieving low-carbon emission reduction.Red mud（RM）is a byproduct that is produced along with the aluminum manufacturing process.However,massively disposal and landfill of bauxite residue have posed significant negative environmental impacts.Although the exploration of recycling technologies has been investigated,low recycling efficiency is still the critical challenge of large-scale utilization of bauxite residue.To eliminate the severe negative environmental impacts of bauxite residue and decline the carbon footprint of Portland cement manufacturing,synergistic utilization of industrial solid wastes as resources to manufacture low-carbon cementitious materials is a promising approach to realize the innoxious treatment of the bauxite residue This paper studied the effective measures to simulate the red mud activity,and geopolymers with high strength,high content of red mud,and low heavy metal ions leaching are prepared.are studied through microanalysis.This paper also studied the influence of the microstructure of matrix and phase composition on mechanical properties.On the base of the above research,different silicon sources including active and low-active are introduced to expand the recycling of other solid wastes.From the research results of the RM-SL binary system,adjusting the order of adding raw materials and alkali activator,changing the stirring speed and time in each process will greatly affect the mechanical properties during molding.Under this system,Method B can stimulate the components which could provide better mechanical strength than Method A and the fracture microscopic morphology is a dense gel phase.It’s showed the leaching test of heavy metal ions of high-performance samples under freezing and thawing cycles,when the red mud content is less than 90%,the leaching amount is less.In this system,high temperature curing has a positive effect on the development of compressive strength.In the red mud-granulated ground blast furnace slag-calcined clay ternary system,the addition of calcined clay will greatly reduce the compressive strength.During this system,high-temperature curing have a negative impact on the mechanical properties.Compared with standard curing,curing at 60°C would produce more loose porous structures.It is showed from the fracture micro-topography,the reaction product of calcined clay does not provide mechanical properties and the hydration product adheres to the surface of unreacted red mud and SL to prevent the alkali-induced reaction.In this system,normal temperature is more conducive to the progress of the reaction.In the red mud-granulated ground blast furnace slag-granite powder ternary system,the strength development trend is consistent with the binary system,and temperature can promote the compressive strength to a deep extent and play a positive role.Through reasonable control of alkali concentration and molding process,low-activity granite powder has the same potential for engineering applications as red mud.Through the research of this paper,the feasibility of high performance of low activity materials such as red mud in building materials was obtained,and the reasons of different performances of the same system in different processes were clearly distinguished,it enriches the micro-mechanism of low-activity materials in alkali-activation system,and expands the idea and method for further developing high-efficiency utilization of low-activity bulk solid waste and green building materials.