Research On The Performance Of Desulfurized Gypsum-based Self-leveling Morta

As China’s economy and industrialization accelerates,thermal power generation generates a large amount of harmful gases such as sulfur dioxide gas,and desulfurization gypsum（Ca SO₄-2H₂O as the main component）becomes an industrial by-product to eliminate gases such as SO₂and SO₃generated during coal combustion.Converting FGD gypsum into a self-leveling material based on FGD gypsum improves the overall utilization of gypsum as an industrial byproduct.As a floor leveling layer,FGD gypsum-based self-leveling material is breathable,lightweight,high-temperature resistant,low-carbon,environmentally friendly,volume-stable,and has high leveling performance.The development and rational utilization of desulfurization gypsum self-leveling material is of great significance,which paves a new way for the large-scale utilization of industrial by-product gypsum and promotes the sustainable,circular and green development of China’s economy and society.The main research contents and conclusions of this thesis are as follows:The effects of different admixtures on the flowability,setting time and strength of FGD gypsum-based self-leveling mortar were studied,and the hydration products and morphology were analyzed by combining X-ray diffraction and scanning electron microscopy.The results showed that the redispersible emulsion powder could improve the flowability of FGD gypsum-based self-leveling mortar,improve the toughness and crack resistance of mortar,and reduce the strength of hardened body,with the maximum flowability of 153 mm at 1%,the lowest strength at 2%,1d flexural and compressive strengths of 1.82 MPa and 3.49 MPa,and adiabatic flexural and compressive strengths of 4.98 MPa and 12.16 MPa.The use of ordinary silicate cement with an optimum addition of 7%improved the fluidity,prolonged setting time,strength and water resistance of the FGD gypsum-based self-leveling mortar,with 1d flexural and compressive strengths of 3.14 MPa and 7.91 MPa,respectively,and absolute dry flexural and compressive strengths of 9.52 MPa and 22.27 MPa.The effects of mixing the two retarders alone and both in combination on the FGD gypsum-based self-leveling mortar,the effect of the flow rate:plant protein retarder>compounding>citric acid;setting time:plant protein retarder>compounding>citric acid;strength loss:citric acid>plant protein retarder>compounding,in this test,the retarder is selected as the most suitable plant protein,with 0.1%,followed by compounding,and the worst is citric acid.With the increase of cellulose dosing or the larger molecular weight,the poorer the fluidity,the longer the setting time and the poorer the strength of the FGD gypsum-based self-leveling mortar.The doping amount in this experiment was 0.05%.The effects of chloride ions on the strength,water absorption and softening coefficient of the desulfurization gypsum-based self-leveling mortar were studied,and the hydration products and morphology were analyzed by combining X-ray diffraction and scanning electron microscopy.The results showed that the flexural and compressive strengths of the desulfurized gypsum-based self-leveling mortar gradually decreased with the increase of chloride ion admixture.The 1d flexural and compressive strengths of the blank group were3.25 MPa and 8.53 MPa,and the adiabatic flexural and compressive strengths were 9.64 MPa and 22.6 MPa,respectively.the 1d flexural and compressive strengths of the group with the highest chloride ion doping were 2.28 MPa and 7.77 MPa,and the adiabatic flexural and compressive strengths were 8.61 MPa and 21.63 MPa,respectively.The higher the chloride ion content in the self-leveling mortar,the greater the water absorption and better the water absorption of the final hardened body,and the smaller the softening coefficient,the poorer the dewatering ability and the poorer the water resistance.The water absorption rate of the blank group is 0.12%and softening coefficient is 0.8;the water absorption rate of the group with the highest chloride ion doping is 0.21%and softening coefficient is 0.65.The effect of the curing mechanism on the performance of desulfurization gypsum-based self-leveling mortar was investigated,and the hydration products and morphology were analyzed by combining X-ray diffraction and scanning electron microscopy.The results showed that the curing temperature of 60±2%℃reached the maximum,1d compressive strength 9.11MPa,1d flexural strength 3.15MPa,absolute dry compressive strength 22.31MPa,absolute dry flexural strength 8.42MPa.curing humidity of 60±2%RH reached the maximum,1d compressive strength 9.24MPa,1d flexural strength 3.25MPa,absolute dry compressive strength The curing time was 24±0.5h,and the maximum value was reached,the absolute dry compressive strength was 22.35MPa and the absolute dry flexural strength was 8.37MPa.