Cementing Behavior Of Pozzolan Cementing Materials For Fine-grained Soil In Geotechnical Engineering

Blast furnace slag(BFS)is a kind of waste from the iron smelting process,and a huge amount of waste has been produced from the blast furnace every year.These solid wastes have occupied a large amount of land and polluted the environment.The BFS has experienced the procedure of heat treatment similar to cement clinker in the process of formation and has the chemical composition same to cement as well.The BFS is typically a kind of artificial pozzolan materials,and it is expected to produce good economic,social and environmental benefits through the preparation of new green cementing materials from BFS and the application of it to instead the cement as the inorganic soil curing agent.For this purpose,a new type of environment-friendly slag-based cementing material(SBCM)was prepared by using the BFS as the main raw material,and using the steel slag,desulfurization gypsum,and cement as adjuvant material.The resulting SBCM specimens were used to solidify fine-grained soil for the strengthening of soft foundation such as silty soil,construction waste residue,etc.It was systematically discussed for the dependances of the properties of solidified soil on the water-cement ratio and on the ratio of cementing material to dry soil.In this paper,another pozzolan cementing material(PCM)was also prepared by using natural pozzolan as the main raw material,which was applied to solidify tailings slurry to fill the wasted mine,and the the curing mechanism of PCM to bind tailings was also discussed.Firstly,the solidified silty soil specimens were prepared by using the SBCM and silty soil as raw materials.The compressive strength and softening coefficient of the resulting solidified silty soil specimens(with water/cement ratio of 0.5)were decreased with the decrease of the ratio of SBCM mass/dry soil mass.As the ratio of SBCM mass/dry soil mass being more than 1:4,the compressive strength and softening coefficiency of 28 d curing age of the resulting solidified soil specimens were more than 3.7 MPa and 0.85,respectively.The solidified soil structure was formed via a three-dimensional skeleton of hydration products of cementing materials.Secondly,the specimens of mould bag solidified clay(MBSC)were prepared by filling the fluid mixture into mould bags,and the fluid mixture included the SBCM,the engineering waste residue,and water at their required ratio.The compressive strength of the resulting MBSC specimens was decreased with the increase of water/cement ratio.As the ratio of water/cement being 0.6,the compressive strength of the resulting MBSC specimens was decreased with the increase of the amount of dry residue.As the mass ratio of SBCM to dry engineering residue being 1:3,the compressive strength of 28 d curing age of the resulting MBSC specimen was 5.82 MPa,and its softening coefficient was more than 0.85,which means it belonging to the solid soil materials with the excellent resistance to water.Finally,solidified tailings specimens for the wasted mine filling were prepared using PCM as the binder of tailings slurry,and the compressive strength of them was decreased with the decrease of the ratio of PCM mass to tailings mass.The best excited temperature for natural pozzolan was 600? for the optimal PCM specimen.With it as the binder and with the increase of addition of plasticizer,the resulting solidified tailings specimens had the decreased compressive strength and dry shrinkage rate.As the ratio of PCM mass to tailings mass being ? 1:10,the compressive strength of resulting specimens of solidified tailings at each curing ages can meet the requirements of mining industry.