Study On Preparation Of Blast Furnace Slag Based Geopolymer Dry Powder Materials

Blast furnace slag based geopolymer is a kind of three-dimensional network gel material generated by aluminum silicate minerals which consist of slag or fly ash and so on according to the reaction of depolymerization-polycondensation with water-glass.The material shows a excellent performance characteristics such as rapid hardening,corrosion resistance,low-cost and green environmental protection,all of those compared with the traditional Portland cement present a better effect which could be applied to traffic emergency repair,nuclear waste enclosed,inorganic coating,high-strength building material,etc.In this paper,the slag,fly ash and silicon fume powder were chose as the main raw material,and actived by instant sodium silicate(molar ratio of SiO2/Na2O was 2.0)to prepare a kind of ecological cementing material with high performance and low-cost.The single-factor analysis was adopted,the mechanical performance,the setting time and the erosion resistance of seawater were put as the main evaluation index,and the influence of the exciting agent dosage,dosage of fly ash and silicon fume powder,cement water ratio,dosage of retarder and water reducing agent on the blast furnace slag based geopolymer powder materials properties was studied,and then the optimum process parameters were determined;Then the XRF,XRD,SEM,BET and other characterization methods were used to show the influence of the phase composition of blast furnace slag based on geopolymer powder materials and different curing conditions on the microstructure,pore structure and mechanical properties.The main conclusions were as follows:1)The optimum process parameters of blast furnace slag based geopolymer powder materials was shown,the mass ratio of slag/fly ash was 4:1,the quality of silicon fume powder accounted for 7%of the total mass of fly ash and slag,the mass ratio of the mixture which made by instant sodium silicate and slag and the fly ash was 20%,the water-binder ratio was 0.24,the mass ratio of retarder/instant sodium silicate was 4%to 6%,the water reducing agent accounted for 0.4%of the total mass.Under the process parameters,the initial and final setting time of the blast furnace slag based geopolymer powder materials need 55-68 min and 66-82 min.The compressive strength of samples were respectively 81 MPa,105 MPa and 128 MPa after curing 3 day,7 day,28 day under standard conditions,the coefficient of erosion resistance was up to 0.97,which illustrated that the mechanical performance of samples almost remained the same in the curing environment of seawater dry-wet alternating.2)NaH2PO4 was chosen as the retarder of the blast furnace slag based geopolymer dry powder materials,when the weight was 0.04-0.06 of instant sodium silicate,the quality of the retarding effect was good and the setting time was stable and controllable.3)Ploycarboxylate water reducer was as admixture,when the weight was 0.4%of the total mass of powder(slag,fly ash and silica fume powder),the mechanical properties and working performance of the blast furnace slag based geopolymer dry powder materials came to the fore.4)Characterized by XRD,SEM and BET and other methods,combining with the phase composition,microstructure,pore structure and other factors,this paper gave a systematic analysis on the different curing system about the mechanical properties of the blast furnace slag based geopolymer dry powder materials.The study found that with the improvement of the steam curing temperature,the compressive strength of samples increased gradually,when curing condition of the steam was at 100℃ for 4 hour,up to the compressive strength of the standard curing after 28 days.Compared with the steam curing,the autoclaved curing could stimulate the more potential of powder.As the temperature of autoclaved curing raised,the compressive strength of sample firstly increased and then decreased,when the curing condition was at 150℃for 4 hour,the compressive strength of samples was up to 175 MPa,and resulting in the density microstructure,less unreacted massive particles,larger specific surface area,the more good microporous(less than 20 nm)instead of the less harmful macroporous(more than 100 nm)and higher compressive strength of samples.