Preparation And Properties Of Slag-tailing Based Artificial Reefs

The slag-tailing based artificial reef is a low-alkali artificial reef made of alkali-activated slag as a cementing material and gold tailings as an aggregate.Due to its low cost and excellent performance,it can replace cement concrete artificial reef.This paper mainly studies the effects of seawater mixing and seawater curing on the hydration reaction characteristics and hydration products of slag activated under different activation systems.Also,the preparation of artificial reef materials was optimized by changing the slag specific surface area and the gold tailings blending amount.Under standard curing conditions,the alkali-activated slag system and the mixing water quality have different effects on the hydration reaction of the slag.In the CaO-CaSO4 and P.042.5 cement-CaSO4 activation systems,the addition of seawater effectively promotes the hydration of slag,and consumes Ca(OH)2 while producing a large amount of ettringite phase and Ht phase.The needle-like and rod-shaped ettringite crystals overlap each other,and the particles in the sample are connected to each other,so that the early compressive strength of the artificial reef is significantly increased.As the curing age is extended,a large amount of network-like CSH gel is formed and filled into In the frame structure formed by the ettringite crystal,a dense structure is formed,the density of the test piece is further increased,and the compressive strength is further developed.In the NaOH activation system,due to the strong alkalinity of NaOH,the hydration of the slag is promoted,thereby obtaining a higher-strength artificial reef.At the same time,the addition of seawater also significantly increases the compressive strength of the artificial reef.The C-S-H gel is the main hydration product in which a small amount of Ht phase is also formed.In the water glass activation system,the addition of seawater is also an increase in the compressive strength of artificial reefs,but the degree of increase is not as obvious as other alkali activation systems.The main hydration product in this system is C-S-H gel.Seawater immersion curing also has a significant impact on the compressive strength of artificial reefs under conditions of seawater mixing.In the CaO-CaSO4 activation system,in the early stage of the hydration reaction,the slag hydration reaction accelerates due to the infiltration of seawater;with the extension of the curing age,the structure of the hydration product has changed due to the filling effect of seawater and the continuous dissolution of alkaline substances in the artificial reef,and finally the compressive strength of the artificial reef has decreased.In other activation systems,seawater immersion curing reduces the compressive strength of artificial reefs in different curing ages,this is due to the filling effect caused by the infiltration of seawater and the continuous dissolution of alkaline substances in artificial reefs,which changes the structure of hydration products,and has a softening effect on artificial reefs,which ultimately affects the strength of artificial reefs.By changing the specific surface area of the slag,the hydration reaction can be effectively promoted and the hydration product can be formed,and the compressive strength of the artificial reef is significantly increased.The increase of specific surface area of slag increases the content of particles less than 5?m and 20?m in slag.The increase of fine slag content can promote the hydration reaction rate and increase the reaction degree of slag.At the same time,the fine slag can also be filled into the pores inside the artificial reef.Under the combined effect of the two,the artificial reef has increased compactness and the compressive strength has also increased.When the amount of gold mine tailings in artificial reefs is increased to 70%,the artificial reefs have a compressive strength of 16.88 MPa for 28 days,which fully meets the design requirements of artificial reefs and maximizes the use of gold mine tailings.Based on the test results,The CaO-CaSO4 composite activated slag was used as the cementing material,and the gold mine tailings were used as the aggregate.The slag-tailing based artificial reef was prepared according to the ratio of cementitious material:gold mine tailings=3:7.While meeting the design requirements of artificial reefs,it has opened up a new way for the utilization of gold mine tailings.