A Recycled Concrete Fines Recycling Carbonation Method And The Regulation Mechanism Research Of Carbonation Products

Recycled concrete fines（RCF）are calcium-rich and alkali-rich in huge quantities,and are an ideal material for carbon absorption and fixation with great potential for application.However,the development and application of RCF carbonation methods is hampered by high gas escape rates,low carbonation efficiency and low product activity due to the continuous aeration in conventional RCF carbonation.In this paper,two key issues,namely“RCF carbonization method”and“carbonization process regulation”,were investigated.By using advanced analytical methods such as isothermal calorimetry,XRD,TGA,SEM and MIP,the effects of carbonized RCF on the hydration and mechanical properties of cementitious materials were investigated,and the relevant mechanisms were revealed,which can provide a theoretical basis and technical basis for optimizing the carbonation method of RCF.The specific research contents and results are as follows.（1）The RCF cyclic carbonation method was proposed,with p H=7 as the single cycle suspension condition.Through the"pass-pause-pass"cyclic method,the degree of RCF carbonation is continuously increased,and the carbonation parameters formed may undergo a dissolution-recrystallization process,contributing to the formation of highly reactive CaCO₃（amorphous form）,and with the number of cycles Some C-S-H gels will be carbonized to silica as the number of cycles proceeds.（2）The effects of cyclic carbonation of RCF on the hydration,mechanical properties and microstructure of cementitious materials were investigated.The 28d compressive strength of the mortar,for example,increased with an increase in the number of cycles,and at three carbonations the compressive strength increased by12.57%relative to the blank group.Mechanistic studies showed that this strength enhancement effect was related to the high activity of CaCO₃formed.（3）Tannic acid（TA）was used as the carbonation process regulator.The study showed that TA could improve the carbonation of RCF and promote the formation of amorphous or spherical aragonite CaCO₃.RCF carbonated with 0.2%TA solution could increase the compressive strength of the prepared mortar at all ages by 29.8%（3d）,50.6%（7 d）and 38.3%（28 d）respectively,compared to the control group.Figure 38 Table 11 Reference 104...