Preparation And Application Of Low Carbon LC~3 Cement Based On PAC Waster Residue

Under the background of carbon peak and carbon neutrality advocated by the global circular economy,promoting energy conservation and emission reduction and making comprehensive utilization of resources are a powerful starting point for building a resource-saving and environment-friendly society.Cement industry is the main source of carbon emission in the manufacturing industry,so it is urgent to seek reasonable and effective "carbon reduction" measures.Polyaluminum chloride(PAC)waste residue is a large production of industrial solid waste.The traditional treatment methods are landfill and stacking,which will not only take up a lot of land,bue also easily cause serious environmental pollution,if it can be as auxiliary material to prepare low carbon cement,it can not only provide a new way for solid waste treatment,but also can promote the development of low carbon cement industry.This paper first studies the physico-chemical properties of PAC waste residue,Through the thermal activation treatment and the activity evaluation,The best calcination system based on carbon emission considerations is determined;Furthermore,the mix ratio of the low-carbon gelling material was optimized,Based on this,the optimal ratio of limestone calcined clay(LC3)cement based on PAC waste residue is determined,Then the life cycle evaluation of different cement systems is conducted;Finally,the LC3 cement was applied to engineered cementitious composites(ECC),By comparing the compressive strength,monomonoc strength of OPC-ECC and LC3-ECC,And evaluate its sustainable indicators in terms of carbon emissions,energy consumption and cost.The main conclusions are as follows:(1)The treated PAC waste residue,combined with micro characterization,activity evaluation and life cycle evaluation:high temperature calcination can improve its activity,different firing temperature and different constant temperature time have great influence on its activity.The activity of PAC waste residue is the best and the carbon emission is the least when the calcination temperature is 700℃ and the constant temperature time is 1 hour.(2)The high-temperature PAC waste residue replaces cement clinker in different proportions and that the compressive strength effect is best at 30%.With the increase of mixing,the fluidity gradually decreases,the condensation time is extended,and the standard consistency water consumption gradually increases.Through microscopic analysis,the early hydration reaction rate is slow and the intensity development is slow,while the late hydration structure is more dense,which is beneficial to the strength development.However,with the increase of incorporation,a large number of holes appear in the structure,and its mechanical properties are reduced.(3)This paper compares the differences in mechanical properties of different cement systems,under differed water binder ratio and conclude that the late strength of LC3 cement system is faster than the ordinary Portland cement,the system can also effectively reduce the heat of hydration;LC3 cement system has significant chloride resistance permeability and reduce dry shrinkage performance.Finally,the life cycle of different cement systems is evaluated,and it is concluded that LC3 cement has a better effect in carbon emission and energy consumption.(4)The LC3-ECC prepared using LC3 cement can meet the basic performance requirements of OPC-ECC.The microscopic analysis shows that the pore distribution refinement of the LC3-ECC matrix favors the development of intensity,while the use of LC3 cement in the ECC can reduce carbon emissions,energy consumption and cost.