Study On Preparation Of Porous Brick By Quicklime Carbonization Bonded Construction Waste

With the acceleration of urbanization,China produces more than one billion tons of construction waste every year,causing great pollution to the environment.Carbon dioxide emissions have always been a tricky issue.The use of construction waste to make porous bricks and use carbon dioxide gas for curing is an effective method to turn waste into treasure;on the one hand,it can effectively utilize construction waste and carbon dioxide to reduce their pollution pressure on the environment;The prepared porous brick has good economic value and can be widely applied in fields such as construction,and has broad application prospects.In this study,construction waste was used as aggregate,calcium hydroxide and magnesium hydroxide as binders,dolomite and steel slag powder as coagulant to prepare porous bricks,and carbon dioxide was used to maintain the samples.This study mainly discusses the effects of coagulant addition,magnesium-calcium molar ratio,curing pressure,curing time on binder sample carbonization,phase composition and morphology,as well as binder content and water consumption on porous brick samples.The impact of performance.The experimental results show that the mass gain rate of the dolomite group is 21.08% at 1.3 wt%,and the highest is 23.83% at 0.6 wt% in the steel slag group.In the dolomite group,the carbonization degree reached 26.34% when the curing pressure was 0.7 MPa,and the steel slag group reached 25.39% at 0.5 MPa.The mass gain rate increased first and then stabilized with the increase of curing time;the carbonization degree of the dolomite group began to stabilize at 4h,while the steel slag group was at 8 h.It can be observed by scanning electron microscopy of two systems that calcium hydroxide and magnesium hydroxide are first adsorbed on the surface of the coagulant,and then fused into a single sheet to form a two-dimensional growth,and then the sheet begins to superimpose,and then the sheet surface begins to have a convex shape.It builds up and gradually grows into cubes,starts three-dimensional growth,and stacks layers.In the dolomite group,when the binder is added at 14 wt%,the compressive strength reaches 32.33 MPa,and the porosity reaches 31.85%.In the steel slag group,the compressive strength reaches 37.83 MPa when the binder is added at 14 wt%,the porosity reached 33.51%,all meet the requirements of use.When the water consumption of the dolomite group is 50wt%,the compressive strength reaches a maximum of 32.24 MPa.When the water consumption of the steel slag group is 40 wt%,the compressive strength reaches a maximum of 39.22 MPa.Dolomite and steel slag powder play a template induction role in the carbonization process of calcium hydroxide,thereby promoting carbonization.The interface between the construction waste and the binder and the interface between the binder and the accelerator,the existing calcium carbonate component will induce the carbonation and crystallization of calcium hydroxide,and the unevenness of the surface of the construction waste increases and bonds.The contact area of the agent provides a better "point of focus" for interfacial bonding.Steel slag exhibits better carbonization performance;compared with dolomite as a coagulant,the addition amount is small,the water consumption is small,the curing pressure is small,the sample carbonization degree is higher,and the compressive strength after bonding with construction waste is better.Porosity is also higher;however,steel slag as a coagulant requires longer curing times to achieve the highest degree of carbonization.