A Study On The Effect Of Whole CO₂ Curing On Hydration And Hardening Properties Of Cement-based Materials

As we all know,a series of environmental problems caused by excessive carbon dioxide emissions in Greenhouse Effect have seriously affected our daily life,how to effectively reduce carbon emissions,to promote the sustainable development of the environment has become a major challenge facing the society today.Using carbon dioxide to conserve cement-based materials can not only recover,utilize and fix carbon dioxide,but also have a positive impact on the sustainable development of cement-based materials industry and the mitigation of global warming caused by greenhouse gas emissions.Regarding the carbon dioxide curing of cement-based materials,at present,the related researches mainly focus on the pre-curing of cement-based materials and CO₂ curing.In this study,the CO₂atmosphere is introduced into the cement-based materials stirring process.In order to further promote the hydration hardening of cement-based materials and improve the immobilization rate of cement-based materials to CO₂,the effects of CO₂ curing on the hydration and hardening properties of non-retarded and retarded cement-based materials are studied.The results show that:?1?The temperature monitoring of CO₂ curing process was carried out.By comparing the temperature curve,it was found that the reaction degree of CO₂ curing was more intense in the early stage of the reaction,and the increase of CO₂ concentration could increase the heat release rate and the first exothermic peak value in the hydration heat release curve.However,the second exothermic peak slightly decreased.?2?CO₂ curing can advance the time of the second exothermic temperature peak of cement hydration exothermic curve with sucrose,the higher the sucrose content,the more the advance time,the higher the sucrose content,the more the advance time,the higher the value of Zn?OH?₂ cement hydration first and the second exothermic temperature peak.The heat release of the reaction process was significantly increased.?3?By comparing the compressive strength of hardened cement stone cured with 33%humidity and 75%humidity,it is found that the compressive strength of hardened cement stone cured with 75%humidity is higher than that of cement stone cured with 75%humidity.The strength of cement stone with retarder can be improved by CO₂curing,but it is slightly lower than that of hardened cement stone cured by standard curing.?4?The subsequent wet curing can significantly improve the strength of cement stone after carbon dioxide curing.After 8 hours of carbonation curing,the strength of cement stone can be increased obviously,but it is of little significance to continue to increase the carbonation curing time.The combination of carbon dioxide curing and wet curing can greatly enhance the hardening performance of cement stone.?5?XRD and micromorphology analysis showed that the hydration product"ettringite"CH crystal reacted with CO₂ to form calcium carbonate.Under the condition of full CO₂ curing,the microstructure of CaCO₃ is more compact due to its well filling of pores.It can be seen that the granular material is calcium carbonate on the subsequent wet curing specimen,which can cover the hydration product surface well,fill the pores,and improve the strength of cement stone.