Preparation Of Phosphogypsum Slag Foam Concrete And Optimization Of Carbonation Resistance

The research content of this topic is mainly divided into two parts: Firstly,the phosphogypsum slag foam concrete was prepared using the persulphated phosphogypsum-slag cement(PPSC)as the base material,and the effects of matrix formulation,type and amount of blowing agent,viscosity of slurry on dry apparent density and mechanical properties of phosphogypsum slag foam concrete were investigated,then study on the Thermal Conductivity,Carbonation Resistance,Microscopic Morphology and Composition of Phosphogypsum Slag Foam Concrete at the Best Mixing Ratio;Secondly,focus on the disadvantages of the lack of carbonation resistance of the PPSC,we investigate the effects of additional substances(salt,alum,water glass),curing temperature,water-cement ratio,and fineness of modified phosphogypsum slurry on the depth of carbonation and strength after carbonization of PPSC,looking for ways to improve the anti-carbonation performance of PPSC and study its mechanism.The results indicate:(1)The optimum mix ratio of phosphogypsum slag foam concrete is: 35%-45% modified phosphorus gypsum slurry,50%-60% slag,3%-4% clinker,2% sulphoaluminate cement,slurry viscosity control above 5.90 Pa·S,1.0%-1.5% hydrogen peroxide according to the dry apparent density,then foam concrete products can be prepared to meet the requirements of the national standard.(2)The purpose of controlling the viscosity of the slurry can be achieved by controlling the amount of water reducer and adjusting the amount of water added.By reducing the amount of water and increasing the amount of water reducer,the viscosity of the slurry can be increased while keeping the fluidity of the slurry constant,which helps to reduce the phenomenon of crosslinked pores created by hydrogen peroxide foaming and increase the strength of foamed concrete.(3)The phosphogypsum slag foamed concrete is poor in carbonation resistance and is fully carbonized in 7 days.On the one hand because of the large porosity and crosslinked pores of the test block.The natural shortage of the anti-carbonization properties of the base material is the other reason.(4)Increase the fineness of phosphogypsum slurry,gypsum crystal grains in cement stone become smaller and more evenly distributed in the slurry,which improve the compactness of cement stone and reduced the average pore diameter of cement stone after carbonization,the carbonization resistance of PPSC is thus improved.(5)Without adding water-reducing agent,the strength of PPSC mortar is significantly reduced after 28 days of carbonization;Use of superplasticizers,reducing the water-cement ratio of PPSC,can significantly increase the density of cement stone,reduce the porosity,increase the strength,and significantly increase the strength of PPSC mortar after carbonization for 28 days.(6)Using high-efficiency water-reducing agent and increasing the fineness of phosphogypsum can further increase the density of PPSC mortar,improve the strength of 28 d mortar,increase the strength after carbonization for 28 days,and significantly reduce the carbonization rate of mortar,it can effectively improve the anti-carbonization performance of PPSC.