Performance of foam lightweight soil with large amount of steel slag powder-cement
Objective To enhance the utilization efficiency of steel slag solid waste,a method was devised to prepare steel slag powder-cement foam lightweight soil by replacing part of cement with steel slag.The road performance of the foamed lightweight soil was then analyzed after the incorporation of steel slag powder to develop economically viable,high-performance foamed lightweight soil.Methods The PO42.5 ordinary Portland cement and steel slag micro-powder were used as the main materials,complemented by sodium carbonate,triethanolamine agents,and a composite foaming agent.During the experimental process,the materials were weighed using an electronic balance and then mixed in a blender according to the specified proportions.Subsequently,diluted foaming agent was added to water to generate fine and dense foam,which was thoroughly mixed with the steel slag micro-powder-cement slurry and poured into cubic molds with its surface leveled.Regarding its performance,the flowability,water absorption rate,water stability,and freeze-thaw stability were assessed based on referenced standards.Additionally,settlement distance and compressive strength were measured at different ages.Furthermore,an anti-sulfate corrosion test was performed by immers-ing specimens in solutions with varying sulfate concentrations to assess changes in compressive strength over time.This work investigated the impact of varying steel slag powder content(40％to 70％),water-cement ratio(0.60 to 0.75),wet density grade(600 kg/m3 to 900 kg/m3),and curing time on the flow value,water absorption,settlement distance,compressive strength,water stability,freeze-thaw stability,and sulfate corrosion resistance of foamed lightweight soil.Results and Discussion As the steel slag powder content increased,the water absorption rate and flow value of the steel slag powder-cement foam lightweight soil gradually increased.Simultaneously,the settlement distance increased with a higher water-cement ratio.Compressive strength initially increased and then decreased with the elevation of the water-cement ratio,as water played a pivotal role as a raw material in hydration reaction between steel slag powder and cement.Insufficient water content at low water-cement ratios impeded full hydration of the slurry material,causing the agglomeration of steel slag powder and cement particles.Consequently,the generated hydration products inadequately filled the pores or adhered to the pore walls,reducing the compressive strength of the specimens.At a water-cement ratio of 0.7,the compressive strength of 28 days peaked at 0.9 MPa,satisfying the specification requirements.At the same age,an increase in steel slag powder content significantly decreasd the compressive strength of the specimens.This decline occurred because the gradual replacement of cement by steel slag powder resulted in a reduction of material actively participating in the overall reaction,leading to decreased hydration product formation and a looser structure.Furthermore,with an increase in steel slag powder content,its settlement distance exhibited an upward trend and then accompanied by a decrease.This phenomenon happened because that the activator enhanced the activity of steel slag,which promoted its synergistic reactions with cement,therefore rapidly elevating the early strength of the foam lightweight soil.This acceleration of the hydration reaction rates consequently reduced the settlement distance.Notably,steel slag powder had mini-mal impact on the fluidity of the foam lightweight soil.The wet density grade exerted a significant influence on the compressive strength and flow value.With an increase in wet density,there was a notable improvement in compressive strength and flow value,accompanied by a reduction in water absorp-tion rate.This enhancement was attributed to the increased proportion of cement and steel slag powder,reducing foam content and pores.Concurrently,the settlement distance exhibited an increasing trend with the rise in wet density due to the decreased foam content,leading to slurry thinning and increased setting time.Steel slag powder-cement foam lightweight soil demonstrated favorable water stability and freeze-thaw stability.Although dry-wet cycles diminished the compressive strength,the loss was minimal.Similarly,the compressive strength of the specimens decreased under the influence of freeze-thaw cycles,with insignificant strength loss.For specimens with a steel slag powder content of 50％,water-cement ratio of 0.70,and wet density grade of 600 kg/m3,the compressive strength in 5％,10％,and 15％sodium sulfate solutions were 0.76 MPa,0.79 MPa,and 0.83 MPa,respec-tively.Compared to the 7-day compressive strength of the G2 test group,these values represented increases of 11.76％,16.18％,and 22.05％,respectively.However,at 28 days,its compressive strength remained unchanged with the concentra-tion of sodium sulfate solution of 15％.After 60 days,a significant decrease in compressive strength occurred,due to excessive ettringite crystals filling the pores,causing internal stress-induced cracking.When the stress surpassed the ultimate tensile stress,plastic deformation occurred,leading to surface peeling.Conclusion The incorporation of steel slag powder and alkaline activator proves to be an effective strategy in enhancing the utili-zation efficiency of steel slag.The mechanical properties of 50％high volume steel slag powder-cement foam lightweight soil are guaranteed.
万方数据
维普
