Preparation And Properties Of Alkali-Activated Lightweight Steel Slag Block

Steel slag is a solid waste produced in the process of steel production.In 2019,the global crude steel output will reach 1.87 billion tons.The production of 1 ton of steel requires the discharge of 0.1 to 0.3 tons of steel slag.In recent years,the state departments concerned are paying more and more attention to the rational treatment and utilization of steel slag.However,the comprehensive utilization rate of steel slag is only 30%due to its high hardness,low cementing activity and poor stability.Compared with 85%comprehensive utilization rate of slag and 75%comprehensive utilization rate of fly ash,the utilization rate of steel slag is lower.In this study,the cementing activity of steel slag was stimulated by alkali excitation according to the mineral components with cementing activity such as C₃S and C₂S contained in the steel slag with high alkalinity.At the same time,to solve the problem of poor stability of steel slag,it is prepared with silica material fly ash and slag into lightweight porous steel slag block,which can be used as heat insulation material.In this study,steel slag,fly ash and steel slag,slag as the main raw materials,module 1.4 sodium silicate as the excitation agent,hydrogen peroxide as the gas agent to prepare two kinds of alkali activated lightweight steel slag block.According to GB/T 11969-2008"autoclaved aerated concrete performance test method"test block strength grade.By means of XRD,SEM,FTIR and TG-DTG,the hydration reaction mechanism was analyzed.The following results are obtained:?1?In the first part of the test,steel slag,fly ash,alkali activator and hydrogen peroxide were used as raw materials to prepare alkali activated steel slag-fly ash lightweight block.The optimal ratio of steel slag 50%,fly ash 50%,water-binder ratio0.32,alkali content 6%,hydrogen peroxide 3%,block dry density 501.3 kg/m³,the compressive strength of 2.34 MPa,this data is close to GB/T 11969-2008"autoclastic aerated concrete performance test method"B05 strength level standard.The low activity of steel slag and fly ash in the early stage leads to the low compressive strength of alkali-activated steel slag and fly ash lightweight block.Microanalysis shows that N-A-S-H gel is the main gel product of alkali activated steel slag-fly ash lightweight block,and there are some C-?A?-S-H gel.?2?Alkali excitation experiment preparation of steel slag,slag of lightweight block,this paper discusses the steel slag content,water-binder ratio,alkali content,hydrogen peroxide content and the effect of alkaline excitation agent type on the block,the block the optimal proportion for 50%steel slag,slag,50%water-binder ratio of 0.32,alkali content of 6%,3%hydrogen peroxide,the light weight steel slag block the dry density of 557 kg/m³,the compressive strength is 3.54 MPa,GB/T 11969-2008 the autoclaved aerated concrete performance test method of B06 strength level standard.Microanalysis shows that the hydration gel products of alkali-activated steel slag-slag lightweight block are mainly C-A-S-H gel,and some C-S-H gels.The early Ca²⁺activity in the steel slag is poor and the reaction is slow.The steel slag does not fully react when the block is 28 days old,and the block strength is increased by the state of fine aggregate?3?In this experiment,a small amount of Ca?OH?₂ was added into the alkali-activated steel slag-slag lightweight block,and the results showed that the 28d compressive strength of the test block with 2%Ca?OH?₂ was 29.7%higher than that of the blank sample.Microanalysis shows that C-A-S-H gel is the main hydration gel product of alkaloid-activated steel slag-slag lightweight block.The introduction of active Ca²⁺by Ca?OH?₂ promotes the generation of hydration products,and the content of C-S-H gel in the system increases and the compressive strength increases.?4?The results show that the alkali-activated steel slag-slag lightweight block has higher strength and higher degree of hydration than the alkali-activated steel slag-slag lightweight block and the alkali-activated steel slag-fly ash lightweight block.The analysis shows that the early Ca²⁺activity in steel slag is relatively low,which is not suitable for mass application in building materials,and it should be used in combination with materials with high early Ca²⁺activity?such as slag?.