Effect of Mixing and Curing System on Carbon Fixation Amount and Performance of Circulating Fluidized Bed Fly Ash Cement Cementitious Material System

Abstract

The use of industrial solid waste to capture and fix CO2 is a promising technology for CO2 sequestration. A thermogravimetric analyzer and CO2 cement hydration mixing device were used to study the effects of mixing method, curing system, temperature, CO2 concentration and other factors on the carbon fixation amount and performance of the circulating fluidized bed fly ash cement-based material system. The results showed that the carbon fixation and early strength of the cementitious materials could be improved by adding CO2 in the stirring process and making CO2 directly participate in the process reaction. The cementing materials samples prepared with CO2 were cured in a standard curing box for 2 days and a carbon atmosphere for 1 day, the carbon fixation amount of the cementing material was increased by 33% and the compressive strength of the cementing material was also improved. This is because under the combined action of carbon mixing and carbon curing, the prepared binding materials produced more Ca(OH)2 in the early stage, and it reacts with the introduced CO2 to form CaCO3. The strength of the calcium carbonate crystals is higher than the strength of the earlier stage of cement, and at the same time, the samples would solidify more CO2. Considering the carbon fixation amount, sample performance and solid waste utilization rate, the best conditions for the cementing materials are as follows: the content of the circulating fluidized bed fly ash (CFA) was 35%, the concentration of carbon curing was 30%, the curing temperature was 40 ℃, the water-binder ratio was 0.4, and the carbon fixation amount of the cementing material could reach about 20%. The use of CFBFA to solidify and storge CO2 is not only a new way to utilize high value-added fly ash resources, but also beneficial for reducing industrial carbon dioxide emissions.