Study On The Hydration Characteristics And Corrosion Resistance Of Steel Slag-Red Mud-Manganese Slag Based Composite Mortar

Cement-based cementitious materials are the most important components of offshore concrete,and their performance directly determines the durability and service life of concrete structures.At present,in view of the low utilization rate of industrial solid waste and the poor corrosion resistance of silicate cement,this paper intends to use converter steel slag,Bayer red mud and electrolytic manganese slag to replace part of the silicate cement to prepare multi-functional solid waste-based cementitious materials with better mechanical properties and excellent corrosion resistance,mainly studied the influence of pretreatment process on the physical and chemical properties of converter steel slag,Bayer red mud and electrolytic manganese slag,and explored the mechanical strength,hydration behavior,physical phase composition and microstructure changes of steel slag-red mud-manganese slag-based composite The changes of mechanical strength,hydration behavior,physical composition and microstructure of steel slag-red mud-manganese slag-based composite colloidal sand were investigated,and the deterioration mechanism of microstructure and properties of composite colloidal sand under the erosion of Cl^-and SO₄^2-ions was elucidated.The main results are as follows:（1）After vertical mill grinding and sieving,the activity indices of 800 mesh steel slag micronized powder increased by 25.7%,13.4%and 10.8%at 3 d,7 d and 28 d of age,respectively,compared with 600 mesh steel slag micronized powder.Although the ball mill modification can optimize the specific surface area and particle size of steel slag micronized powder,its activity enhancement is limited;with the increase of thermal activation temperature,the activity and leachate PH of red mud show a trend of increasing first and then decreasing,and the optimal thermal activation temperature of red mud is 700°C;with the increase of Ca O doping,the better the effect on the removal of NH₄⁺and the solidification of Mn²⁺in manganese slag.When the Ca O doping amount was 5%,the removal rate of NH₄⁺from manganese slag reached 96.75%and the curing rate of Mn²⁺reached 97.75%.（2）The admixture of red mud and manganese slag can promote the hydration of steel slag,resulting in the shortening of the induction period of the composite mortar system and the increase of the accumulated heat release.The mechanical properties of the composite mortar with 12%red mud and 3%manganese slag are the best when steel slag is mixed at 15%,and the 28 d flexural and compressive strengths were 7.2 MPa and 41.4 MPa,respectively.this is mainly because the admixture of red mud and manganese slag can not only fill the pores,but also promote the hydration reaction of the slurry and produce more hydration products which are beneficial to the development of mechanical properties AFt and C-S（A）-H gel.As a result,the percentage of harmful pores and multi-harmful pores decreased,the percentage of harmless pores and less harmful pores increased,and the compactness of the material improved compared with the 30%steel slag blended alone.（3）When steel slag is 25%,red mud is 2%and manganese slag is 3%,the 30 d and 60 d fluxes of the composite sand are significantly reduced,the flexural erosion coefficient K and compressive erosion coefficient Kc are significantly increased,and the erosion resistance is excellent.This is mainly because the appropriate amount of steel slag,red mud and manganese slag can not only improve the density of the material,but also promote the hydration of the slurry and generate more hydration products.At the same time,in the process of Cl^-ion erosion,the admixture will promote the formation of Friedel salt,and the products can not only fill the pores,but also solidify Cl^-ions;in the process of SO₄^2-ion erosion,the admixture will promote the formation of AFt and Ca SO₄·2H₂O,which also play the role of filling the pores,both of which hinder the erosion to a certain extent.ion diffusion,improving the corrosion resistance of the composite mortar system.