Research On Preparation And Properties Of Phosphogypsum Ceramsite Foam Concrete And Block

With the continuous improvement of living standards,building energy consumption continues to increase,bringing huge energy burden to the society.As a green and environmentfriendly wall building material,gypsum block has been popularized and applied in building energy conservation in China.The annual output and historical stock of industrial waste phosphogypsum are huge,but the overall utilization rate is low,and the environmental risk is increasingly prominent.Phosphogypsum can be widely used in the production of gypsum blocks,which is highly in line with the policy of energy conservation and environmental protection in China and has a broad development prospect.In this article,phosphogypsum was pretreated by grinding to improve the particle morphology and size distribution of phosphogypsum.Phosphogypsum ceramsite foamed concrete（Referred to as PCFC）was prepared by physical foaming method.The effects of phosphogypsum ceramsite dosage,phosphogypsum ceramsite pre-wetting time,fiber dosage,metakaolin dosage and water-proofing agent on the properties of PCFC were investigated.PCFC block is prepared,which meets the requirements of JC/T 698-2010 "Gypsum Block".The main conclusions are as follows:（1）The particle size of phosphogypsum was refined by grinding.When grinding time was between 15 and 20min,the mechanical properties of phosphogypsum hardened body were better.Cement can effectively enhance the mechanical strength of gypsum base material and improve its water resistance.When the cement content is 50%,it can effectively improve the mechanical strength of phosphogypsum cement binder.The optimum grinding time was 15min,and the median diameter of phosphogypsum was about 29 μm.（2）After the addition of phosphogypsum ceramicite,the proportion of small holes in the PCFC decreases,the proportion of large holes increases,and the average aperture increases.The compressive strength of the PCFC decreases,the water absorption rate decreases,the softening coefficient increases,and the drying shrinkage rate decreases.Finally,the dosage of phosphogypsum ceramicite is 0.2 m3/m3.With phosphorus gypsum ceramsite prewetting the extension of time,PCFC internal large aperture ratio decreases,the proportion of small aperture increased,stomatal aperture showed a trend of decrease of the whole,the compressive strength first increases then decreases,bibulous rate is lower,fell slightly after rose first,softening coefficient,dry shrinkage rate decreases,and the phosphorus gypsum the prewetting haydite time control in 1 h is more appropriate.（3）Incorporation of polypropylene fiber can greatly refine PCFC internal aperture,but too much fiber dosage can cause pore size is increased,the compressive strength increases with the increase of fiber content first,after absorbing water,after takes the lead in reducing softening coefficient down after rising first,but the overall changes much,drying shrinkage is effectively suppressed,coefficient of thermal conductivity is reduced.The thermal insulation performance is improved,and the optimal fiber content is 0.3%.With the increase of dosage of metakaolin,PCFC internal small aperture ratio increases after the first decreases,and the proportion of large aperture increased after decreased first,the average aperture slightly decreased after the first increases,the compressive strength first increases then decreases,absorbing water,after takes the lead in reducing softening coefficient down after rising first,drying shrinkage increase with the decrease of the first.The thermal conductivity is not affected by metakaolin,and the optimum dosage of metakaolin is 7.5%.The water-repellent agent can effectively reduce the volumetric water absorption of PCFC,and the water absorption of 2 h decreases obviously,and the softening coefficient increases gradually.（4）Selection of optimal material composition:phosphogypsum 50.0%,cement 42.5%,metakaolin 7.5%,phosphogypsum ceramsite 0.2 m3/m3,polypropylene fiber 0.3%,water reducing agent 0.03%,water-binder ratio 0.3,the preparation of PCFC block,the block apparent density 924 kg/m3,fracture load 2684.67 N,softening coefficient 0.71,meet the requirements of JC/T 698-2010 "Gypsum Block".