Study On Modification Of Phosphorous Building Gypsum By Nanomaterials

Phosphogypsum(PG)is a by-product of the phosphate fertilizer industry,which is a solid waste produced during the production of phosphoric acid in industry.At present,the annual output of PG in my country is still very large,storage is the main disposal method and the utilization rate is very low.Its accumulation not only occupies a lot of land,but also causes great pollution to the surrounding ecological environment.Therefore,PG needs to be used on a large scale.There are many ways to use PG,among them,using it in the building materials industry is one of the important methods to use PG on a large scale.There are many approaches to utilize PG in the building materials industry,using it to produce building gypsum and its products not only can consume a large amount of PG but also can turn waste into treasure,which will achieve the purpose of comprehensive utilization.Due to the common problems of low strength and poor water resistance in gypsum products,many scholars have explored the modification of phosphorous building gypsum(PBG)and have achieved some results.With the development of nanotechnology,the application of nanomaterials in the field of construction materials has gradually increased,especially the application of nanomaterials in cement-based materials,which has improved the performance of cement-based materials.Nanomaterials are expected to improve the strength and water resistance of hardened building gypsum due to their extremely small size,which can effectively fill the pores of gypsum matrix and compact its structure.However,there are few related researches on the application of nanomaterials in building gypsum.Therefore,this article explores the modification effect of nano-materials on PBG by adding nano-Si O₂,carbon nanofibers(CNF)and graphene to PBG,hoping to obtain a new modification method and improve the utilization rate of PG.In this paper,by adding different amounts of nano-Si O₂,carbon nanofibers and graphene to explore the effects of the three on the workability,mechanical properties and water resistance of PBG.The phase composition,the process of hydration and the morphology of the modified hydration product were analyzed,and trying to find out the modification mechanism.First,PG is heated at a certain temperature and time and ball milled to obtain PBG,then,nanomaterials are added to the PBG and a series of performance tests are carried out.The results show that the addition of the three kinds of nanomaterials has no effect on the water consumption of standard consistency of the PBG,but has different effects on the setting time.The addition of nano-Si O₂ and graphene can shorten the setting time of PBG,while the addition of CNF can prolong the setting time.The addition of three kinds of nanomaterials can improve the strength of the hardened paste after hydration of PBG to some extent.In the aspect of water resistance,the addition of nano-Si O₂ and graphene can improve the water resistance of the hardened paste of PBG,while the addition of CNF has no effect on the improvement of water resistance.In this study,X-ray diffraction analysis was used to analyze the phase composition of the hydration product,and it was found that the addition of three kinds of nanomaterials had no effect on the phase composition of the hydration product;an 8-channel calorimeter was used to analyze the heat release rate and total heat release of the hydration process,and the results show that the addition of nano-Si O₂ and graphene can accelerate the hydration and make the hydration more thorough,which is consistent with the result of setting time.The SEM analysis was used to analyze the morphology of the hydration products,the results showed that the addition of nano-Si O₂ and graphene can optimize the morphology of the gypsum crystals and thus the strength was increased,however,there is not obvious features of the effects of the addition of CNF on the crystal morphology of hydration products of PBG,and the influence mechanism of CNF cannot be determined by the difference of morphology.