A Study On Modification Of Phosphogypsum And Preparation Of Light Plastering Gypsum Mortar

The "14th Five-Year Plan" emphasizes the need to achieve coordinated development and green and low-carbon transformation,and comprehensively improve the efficiency of resource utilization.Therefore,this paper will study the preparation of modified lightweight plastering gypsum mortar by using phosphogypsum,a solid waste produced in the industrial production of phosphoric acid,to improve its mechanical properties and water resistance.The research contents of this paper are as follows:1.By adding retarder,water retention agent,thixotropic lubricant and light aggregate vitrified microbeads,the effects of admixtures and light aggregates on the physical properties of plastering gypsum under different dosages were explored.XRD and SEM were used to analyze the action mechanism of retarder on phosphorus building gypsum.The results show that the addition of admixtures and light aggregates delays the setting time,increases the water retention rate,and achieves light weight,but the addition of admixtures and light aggregates will affect the strength;the addition of retarders changes the dihydrate The morphology of the gypsum crystals reduces the strength of the hardened body.2.The modification of phosphorus building gypsum was studied by single and double mixing of cement and slag,and the hydration products of modified plastering gypsum were analyzed by XRD and SEM.The experimental results show that the single mixing of slag and cement can improve the water resistance,and the single mixing of cement is better than the single mixing of slag.Gypsum: slag: cement = 72.7%: 17.3%: 10%,the compressive strength of the hardened body of modified plastering gypsum is 14.3MPa,the softening coefficient is 0.75,the compressive strength of the hardened body of phosphorus building gypsum is 8.9MPa,and the softening coefficient is 0.5 respectively.The increase of 60.6% and 50%;the filling of vulcanite and the encapsulation of dihydrate gypsum crystals by calcium silicate gel are the main reasons for the improvement of its mechanical strength and water resistance.3.Under the optimal ratio,the effects of various admixtures and light aggregates on the physical properties of modified plastering gypsum were investigated.The results show that the effect of admixtures and light aggregates on the modified plastering gypsum is the same as that of phosphorus plastering gypsum,but the mechanical properties of the hardened body of the modified plastering gypsum are better than those of the unmodified plaster.4.The modified light base plastering gypsum mortar was prepared,the hydration products and microscopic morphology of the modified light base plastering gypsum mortar were analyzed by XRD and SEM,and the modified light base plastering plaster was analyzed by finite element Ansys The thermal insulation performance of gypsum mortar was analyzed.The results show that the improvement of the mechanical properties and water resistance of the modified light plastering gypsum mortar is because the slag exerts the pozzolanic effect under the alkaline excitation of the cement to generate calcium silicate gel to encapsulate the vorvanite and dihydrate gypsum crystals,making the crystal structure more stable.Compared with the traditional cement mortar,the modified lightweight bottom plastering gypsum mortar has better thermal insulation performance,lower heat flux density,and the temperature difference between the inner and outer surfaces is 6.405℃,which is 1.211℃ higher than that of cement mortar plastering.