Preparation And Properties Of Alkali-activated Red Brick Powder-based Cementitious Material

Alkali-activated cementing materials are eco-friendly materials to instead conventional cements.Its applications can reduce the emission of harmful gases,such as sulfur dioxide,fluoride,and carbon dioxide in producing traditional cements.Moreover,the excellent mechanical properties and durability have attracted wide attention.Alkali-activated cementitious materials productions are effective in solving solid waste problems.At present,with the demolition of old buildings,the preparation of alkali-activated cementitious materials to expend waste red bricks has been paid more attention.Therefore,based on the efficient utilization and low-cost treatment of waste red brick,this study explores the performance of red brick powder based cementitious material using calcium carbide slag as alkali activator（RCAM）.Afterwards,the benefit analyses of environment and cost were carried out.Firstly,to promote the efficient utilization of red brick powder,the effect of particle size of red brick powder on the mechanical properties of RCAM was investigated.Then,the mix design of RCAM was optimized accordingly.Since curing conditions have a significant impact on the strength development of alkali-activated materials,this study further explored the strength changes and microstructure transformation of RCAM under different curing humidity.The results show that the strength of RCAM increases with the particle size decrease.However,when the particle size of red brick powder is less than 75μm,the agglomeration phenomenon of less free water molecules in the specimen matrix particles which reduces the strength of RCAM.In addition,the strength development of RCAM does not depend on humidity significantly when curing at room temperature.Under the high temperature condition for accelerating curing,85%ambient humidity can offset the strength deterioration caused by water evaporation.In addition,the excellent high temperature stability rises the application potential of RCAM under special conditions.In this study,the residual strength of RCAM after high temperature treatment was observed by changing the content of each component.It is found that higher red brick powder content leads to high temperature stability of RCAM,which showing better high-temperature stability than ordinary Portland cement（OPC）.Besides,when controlling the content of red brick powder,substitute part of calcium carbide slag with aluminum correction material,Na Al O₂,can further improve the high temperature stability of RCAM.Finally,the environmental and economic benefits of RCAM were analyzed comprehensively.When using RCAM as a concrete binder,carbon dioxide emissions can be reduced by more than 97.7%per kilogram of concrete product.Moreover,the cost can be reduced by at least 83.8%compared to that of OPC.The raw material cost of the RCAM system would turn to negative when considering the charge of solid waste disposal.After mix design optimization,RCAM would achieve a larger critical transport radius than OPC,in any transport mode,which representing better economic benefits.