Carbonation Curing Solid Waste Non-burning Brick Formula Optimization Research And Industrial Demonstration

The COVID-19 pandemic has caused the largest decline in carbon emissions since 1900,but it still cannot meet the 1.5°C global warming target in Paris Agreement.It is recognized that Carbon Capture,Utilization and Storage（CCUS）technology can be an important countermeasure to solve the problem of global warming.However,CO₂captured by Direct Air Capture（DAC）,chemical adsorption methods,etc.requires large-scale and economic using approaches.Carbonation curing light-weight building materials can not only recycle vast quantities of solid waste from industrials,but also produce green building materials as well as achieve negative carbon emissions;it can also replace the existing autoclave curing technology in the concrete industry with high energy consumption,shorten the long-term natural curing process,reduce energy consumption input,and obtain high economic value added.However,the existing research on carbonation curing concentrates on one or two kinds of solid waste formulations,but lacks an effective combination of various industrial solid wastes to further optimize the cementitious material system.At the same time,there’s also a lack of process optimization and industrial demonstration verification for large-scale carbonation curing concrete in China.In view of the above-mentioned problems,this paper has carried out the development of new cementitious materials based on recycled industrial solid wastes,the optimization of carbonation curing process and the 10,000-ton industrial demonstration project.First of all,two cementitious material systems have been developed.For the paste system with a high proportion of cement（≤40%）,the mechanical properties and carbon fixation performances of the specimens were higher,even could reach MU30and 8%carbon fixation rate.After screening and optimization,the best preparation and remaining water-to-solid ratio w/s have been found out,as well as the best mixing ratio of steel slag and fly ash（50wt.%steel slag-10wt.%fly ash）.The microscopic structures’changes of the specimens were detected through XRD,SEM and other characterization methods.The filling effect and distribution changes of pores before and after mineralization,as well as the corresponding mechanism of microstructure-macro performance correlation were analyzed from the crystal structure of carbonation products.In addition,developed the composite mortar cementing system.First,explored the formula adjustment law of steel slag-fly ash-bottom slag-calcium carbide slag-cement composite solid waste solid concrete.Also,aiming at the types and performances of local solid wastes in Henan province,focused on the molding pressure,pre-curing time and remaining w/s under the industrial environment,and the impact on the final compressive strength of subsequent curing conditions.Experimental results showed that the suitable preparation water-solid ratio of composite mortar cementing system concrete was 13wt.%～18wt.%,and the perfect water-solid ratio before carbonation was about 10wt.%.The curves of water loss rate and carbon fixation rate in the pre-curing process presented consistent.Increasing molding pressure and increasing subsequent hydration curing process can be an effective supplement for strength growth.At the same time,this paper also completed the design of a large-scale CO₂ deep carbonation of building materials demonstration device design,and carried out the transformation,construction and pre-experiments of the industrial vertification device.The parameters of the mixing system and the brick machine were adjusted,a CO₂vaporization device and supporting pipelines were added to the original autoclaved curing equipment,and solved the problems exposed in the single tank test,laying the foundation for the 10,000-ton test.For the continuous operation of 10,000 tons,a cascade equalizing pressure carbonation curing system was designed.The total amount of materials used in the 72-hour continuous operation was 1,909 tons,and 36 tons were lost in transportation and screening though data calculation.The production of lightweight concrete bricks was1,700 tons;the CO₂ intake was 100.08 tons,and the final emissions 1.04 tons,the CO₂absorption rate was 98.97%.The average CO₂ sequestration rate obtained by the tanker weighing method and weighing method of samples were 5.88%and 6.74%,respectively.The average compressive strength of concrete after carbonation curing was 15.8MPa,which was 41.07%higher than that under natural curing,and reached the MU15standard.In addition,the temperature and pressure data of the demonstration project showed that the large-scale carbonaiton reaction rate was a special apparent kinetics controlled by the CO₂ intake process.The entire reaction lasted about 7 hours.The reaction was extremely rapid in the the pressure equalization stage（the first 30 minutes）,which showed that the temperature and pressure curves were at a plateau at this stage.The pressure of the four curing chambers was only about 0.05 MPa at equilibrium,which meaned the CO₂ emitted into the atmosphere was only 1%of the total consumption.The curves began to rise rapidly after about 2 hours,but the starting point of the temperature rise was 30 minutes later than the that of the pressure rise.After that,due to the huge volume of concrete to be cured,there was no constant pressure stage during the carbonation curing process.The curing temperature reached up to 144℃.Analyzing results of the morphology and pore structure showed that when the time was relatively long enough for pre-curing,the carbonation product tended to form aragonite and vaterite crystals with higher energy rather than the most stable calcite.Economic analysis showed that the overall economic benefits of carbonation curing was 326.42yuan per ton of CO₂ captured.If the flue gas emitted from the chemical or cement industries replacing industrial carbon dioxide is used for carbonation curing,the cost can be further reduced.