Study And Influence Of Chemical Pretreatment Of Silicon Manganese Slag Fine Aggregate On Strength And Salt Freeze Resistance Of UHPC

Silicon manganese slag is a type of heavy metal-containing,acidic and porous industrial solid waste discharged during the smelting process of silicon manganese alloy.Its stacking not only occupies land resources,but also pollutes the environment.Due to the high price of refined quartz sand,the preparation cost of UHPC increases,which hinders the application of UHPC in projects with limited budget.With the development of economy and society,the supply of sand and stone will be difficult to meet the development needs of various industries,which will hinder the application and development of UHPC.Water glass pretreatment means that the sodium silicate gel and calcium silicate colloid hardened and precipitated by the water glass solution under the condition of CO₂can fill and glue the material with pores,thereby improving the internal structure of the material.In view of the above problems,this paper combines the porous shape of silico manganese slag,the high-pressure crushing value,the characteristics of containing certain active substances and the superiority of water glass pretreatment to explore the influence of silico manganese slag before and after pretreatment on its water absorption,and the pretreatment.Effects of fine aggregate before and after treatment on UHPC fluidity,strength,salt-freezing resistance,and microscopic mechanism.（1）After the granular silicon manganese slag is pretreated by soaking with different concentrations of water glass solution and different time,the water absorption rate gradually decrease with the increase of water glass concentration and the prolongation of pretreatment time.Among them,when the concentration increase to 8%and the time is extended to 48h,the water absorption rate decrease by 11.1%and 8%,respectively.（2）The effects of different silicon manganese slag content,water glass concentration and pretreatment time on the fluidity and strength of UHPC configuration are investigated.The results show that the proper amount of silica sand is replaced by silico manganese slag,which improves the fluidity and strength of UHPC;the appropriate water glass concentration and pretreatment time reduce the water absorption of silicon manganese slag,increase the amount of free water between particles,and improve the water-cement ratio in the transition zone of the silicon manganese slag interface is improved,and the fluidity and strength of UHPC are improved.Among them,S50-2-24 has the best performance.（3）In allusion to the harsh environment of the Northwest Salt Lake area,the salt-freezing resistance of UHPC doped with silicon manganese slag in sodium sulfate solution with a mass fraction of 5%is explored.The study found that the appropriate content of silicon manganese slag,water glass concentration and pretreatment time are all beneficial to improve the salt-freezing resistance of UHPC.It is verified that an appropriate amount of silico manganese slag can fill the gaps between quartz sand and other particles,making the UHPC matrix more compact;appropriate pretreatment of water glass can make the interface transition zone of silicon manganese slag more compact;the higher the strength of the test group,the Its resistance to salt freezing is better.（4）The microscopic morphology and mechanism of UHPC doped silicon manganese slag are explored.The test shows that a large amount of hydration products such as calcium silicate hydrate and calcite are generated in UHPC;the smaller and fewer pores in the UHPC matrix,the denser the distribution of hydration products,the higher the strength of the test group and the better the resistance to salt freezing;Appropriate dosage of silicon manganese slag,water glass concentration and pretreatment time are all beneficial to improve the density and thickness of the interface transition zone of silicon manganese slag,make the bond between silicon manganese slag and UHPC matrix more compact,and weaken the UHPC matrix as a whole.The weakness of the transition zone makes the mechanical properties and durability of UHPC more excellent.