The Application Of Phosphogypsum In Autoclaved Aerated Concrete

Phosphogypsum(PG)is the main industrial by-product in the process of wet phosphoric acid preparation.Due to the large number of impurities in PG,the utilization rate of PG is very low at present.Most of PG is stored in the open environment,and some are even near densely populated residential areas.This occupies land resources,but also the impurities in PG will penetrate into the soil and rivers,causing environmental pollution around.Therefore,how to efficiently utilize PG is the main research direction of PG resource reclamation in the future.Autoclaved aerated concrete is a kind of green building material,which has many excellent properties,among which the biggest advantage is that it can use industrial solid waste as an alternative raw material to produce related products.This paper explores the influence of PG on the performance of autoclaved aerated concrete,also analyzes the influence of discarded Zeolite Socony Mobile-5(ZSM-5)on the performance of PG-based autoclaved aerated concrete,and finally uses PG to completely replace fly ash to prepare autoclaved aerated concrete products with large dosage of PG.The test of strength and bulk density,mineral composition analysis,Fourier infrared spectrum change analysis,thermogravimetric analysis,pore structure characterization,and scanning electron microscope analysis were carried out.The contents are mainly as follows:(1)The effect of PG on the properties of autoclaved aerated concrete.The results showed that the addition of PG reduced the p H value of slurry,increased the viscosity and inhibited the foaming process.Before autoclaving,the addition of PG promotes the formation of ettringite.After autoclaving,the gypsum converted into anhydrite.When the content of PG is 15%,the bulk density of the product is 715 kg/m~3,and the strength is 7.5 MPa.The bulk density and strength of the product reach the national standards(GB/T11968-2020)B07 and A5.0,respectively.(2)The influence of waste ZSM-5 on the performance of PG-based autoclaved aerated concrete is studied.The results show that:Adding the waste ZSM-5 to the autoclaved aerated concrete of PG will significantly reduce the dry density of the product.When the content of the waste ZSM-5 is 37.5%and the content of PG is 20%,the bulk density of the product is 518 kg/cm~3and the strength is 2.8 MPa.The bulk density and strength of the product meet the national standard B05 and A2.5,respectively.(3)Using the good foaming effect of waste ZSM-5,the experimental ratio is adjusted,and the autoclaved aerated concrete sample with PG as the main raw material was prepared.Finally,PG was used to completely replace fly ash.The results show that when the content of PG is 54%,the bulk density of the product is 622 kg/cm~3and the strength is 4.9 MPa.The bulk density and strength of the product meet the national standard B06 and A3.5,respectively.