Preparation And Properties Of Lightweight Wall Materials With High Content Of Solid Waste EPS

As a new type of building material,EPS lightweight wall material has the advantages of light weight,high strength,heat preservation and heat insulation.During the preparation process,EPS particles will float up,resulting in uneven distribution of cementitious materials and large pores in the wall structure.Therefore,in this thesis,cellulose ether,redispersible latex powder and polyvinyl alcohol solution were used to modify the surface of EPS particles.At the same time,in order to improve the mechanical properties of EPS lightweight wall materials and promote the resource utilization and high added value transformation of bulk industrial solid waste,a gypsum-based composite cementitious material was prepared by using desulfurized gypsum,fly ash and slag to replace cement.The influence of each component on its physical and mechanical properties was analyzed by orthogonal test.The performance of cementitious materials was optimized by selecting water reducing agent,retarder and iron tailings,and the synergistic hydration reaction mechanism of gypsum-based composite cementitious materials was explored by means of XRD,SEM and TG-DTG.The main research contents and conclusions are as follows:（1）Taking the mechanical strength,dry density,softening coefficient and water absorption rate as the expected target,the influence of each component on the performance of gypsum-based composite cementitious materials was analyzed by orthogonal test,and the optimal ratio was obtained.The results show that the water-binder ratio is the main factor affecting the performance of cementitious materials.When the cement content is 20%,the desulfurization gypsum content is 56%,the fly ash content is 19.2%,the slag content is 4.8%and the water-binder ratio is 0.55,the 28d flexural strength of the sample is 5.35MPa,and the 28d compressive strength is 23.96MPa.（2）XRD,SEM and TG-DTG tests were carried out on specimens of different cementitious materials at various ages to analyse their co-hydration mechanism.The results show that the hydration reaction between desulphurisation gypsum and cement can synergise with each other,with C-A-H further generating AFt under the action of SO4^2-,and at the same time can play the role of alkali-salt joint excitation for coal ash-slag,generating a large amount of cementitious substances,filling the pores of gypsum crystal structure and forming a more dense microstructure.（3）The effect of water reducing agent,retarder and iron tailing powder on the performance of cementitious material was analyzed by flow rate,setting time and compressive strength,etc.The results showed that:when the water reducing agent was increased to 0.5%,the initial expansion of the slurry could reach 36cm,a relative increase of56.5%;when the retarder was mixed with 0.5%,the initial and final setting time of the cementitious material was the longest,110min When the mechanical activation of iron tailing was 1.5h,the specific surface area of iron tailing powder was the largest,with a specific surface area of 1360m²/kg,and the 28d strength of the specimen reached the maximum,with a flexural strength of 5.85MPa and a compressive strength of 23.89MPa.（4）By mixing with cellulose ether,redispersible emulsion powder and polyvinyl alcohol solution to modify the surface of the EPS particles,making it hydrophilic,conducive to better infiltration of the cementitious material slurry,to avoid the suspension of EPS particles in layers,the formation of a uniform and dense structural skeleton,thus improving the overall performance of EPS lightweight wall materials.