Study On Preparation Of Calcium Sulfoaluminate Expansive Agent From Electrolytic Manganese Residue And Its Performance

Electrolytic manganese residue is an industrial waste residue after acid leaching of manganese ore.Because of its high sulfur content,heavy metal ions,and complex composition,it has become the primary problem facing the electrolytic manganese industry.Therefore,it has important significance to research the resource utilization and approach of electrolytic manganese residue.Electrolytic manganese residue contains many components,such as sulfate and hematite,which is common component of calcium sulfoaluminate and iron phase in the preparation of iron phase-rich calcium sulfoaluminate expansive agent.Therfore,the effects of different proportions,sintering process?sintering temperature,holding time?,gypsum content,curing system,and particle gradation on the performance of calcium sulfoaluminate expansive agent were systematically investigated,and their hydration properties were analyzed.The main research results are as follows:?1?Because electrolytic manganese residue contains a large amount of soluble manganese,which adversely affects the burning of expanded clinker minerals,this article uses sulfuric acid as an acidolysis agent to remove soluble manganese in electrolytic manganese residue by water bath.The results show that the use of sulfuric acid to remove soluble manganese in electrolytic manganese residue is feasible.With the constant increase of solid-liquid ratio,sulfuric acid concentration,water bath temperature and water bath time,the manganese content in the manganese residue is continuously decreasing,but the decreasing trend tends to stable.The best conditions for the acid leaching treatment of electrolytic manganese residue are manganese residue:sulfuric acid=1:10,sulfuric acid concentration of 1.5 mol/L,and water bath at 80?for 2 h.?2?Using the electrolytic manganese residue after acid leaching,bauxite,calcium carbonate and gypsum as raw materials,the solid phase sintering method is used to prepare the calcium sulfoaluminate expansive clinker.Under the condition that the sintering temperature is1300?for 60 min,the effect of composition on the phase,microstructure and properties of the calcium sulfoaluminate expansive were investigated.It was found that when the C_m was0.82⁰.95,P is 2.5².8,F is 3.53⁵.01,the performance satified the performance requirements of the national standard GB/T 23439-2017"Concrete Expansive Agent".Manganese residue:bauxite:calcium carbonate:gypsum=16:21:57:6 as the experimental basis,the effect of the sintering process on the microstructure,early hydration behavior,pore structure and properties of the calcium sulfoaluminate expansive clinker was studied.It was determined that when the sintering temperature range was 1250?¹325?and the holding time range was 15 min¹20 min,the performance satfised the national standard.Which made a good foundation for the subsequent experiments.?3?Based on the experimental results obtained in?2?,the mutual influence of factors such as composition and sintering process was studied through orthogonal experiments.The results show that the main phases of clinker are C₄A₃S,C₂?A,F?and C₂S and C_m is the main factor affecting the 7 d restricted expansion rate,followed by the P,holding time,F,and sintering temperature.the best clinker sintering conditions is the C_m is 0.89,P is 2.6,F is 4.01,the sintering temperature is 1275?,and the holding time is 60 min.Under the better experimental conditions,the hydration performance of the calcium sulfoaluminate expansive clinker was studied.The results showed that the calcium sulfoaluminate expansive clinker hydration mainly generates AFm phase,hydrated calcium iron aluminate,iron glue and aluminum glue.When calcium sulfoaluminate expansion clinker is mixed with portland cement for hydration,portland cement contains gypsum,which leads to AFm phase,hydrated calcium iron aluminate,iron glue,aluminum glue and gypsum in Ca?OH?₂,the reaction generates the AFt phase.?4?The effect of particle gradation on the properties of calcium sulfoaluminate expansive clinker was studied.The results show that when the proportion of particle size of less than 40?m is 30%,and the proportion of particle size of between 40?m and 250?m is 65%,the proportion of particle size of bigger than 250?m is 5%,the strength and expansion performance of calcium sulfoaluminate expansive clinker are coordinated,the 7 d compressive strength and 28 d compressive strength are 29.09 MPa and 46.27 Mpa,the 7 d restricted expansion rate and 28 d restricted expansion rate are 0.052%and 0.005%.?5?The effects of gypsum dosage and curing system on the properties of calcium sulfoaluminate expansive clinker were studied.The microstructure of cement stone was determined by XRD and SEM,and the pore structure inside cement stone was tested by mercury intrusion method.The results show that with the increase of the amount of gypsum,which promotes the formation of AFt and the transformation of AFm to AFt phase,and improves the expansion energy and mechanical properties of the mortar test block.When the amount of gypsum is 10%,the cement stone has lower pore size and porosity,and the compressive strength,flexural strength and restricted expansion rate of the mortar test block are higher.,the 7 d compressive strength and 28 d compressive strength are 34.34 MPa and54.92 Mpa,the 7 d restricted expansion rate and 28 d restricted expansion rate are 0.043%and 0.005%.As the relative humidity in the maintenance system decreases,the restricted expansion rate continues to decrease.The single curing method has a small pore size and low porosity,but due to the occurrence of the"pan-alkali"phenomenon,the mechanical properties do not reach the national standard.With the increase of curing temperature,the hydration speed is accelerated,and the transition from AFt to AFm phase is promoted.When the curing temperature is 40?,it has a higher limiting expansion rate.Seriously,the compressive strength keeps decreasing,and the national standard performance requirements are not satisfied.