| As a porous material,foam concrete plays an important role in the field of architecture because of its advantages of light weight,good heat preservation effect,good buffer energy absorption and so on However,conventional foam concrete also has some problems such as low green degree and low early strength Therefore,green geopolymer foam concrete(GFC)came into being,but it is easy to shrink,crack and difficult to form In this paper,the fluidity,mechanical properties,ultrasonic wave velocity drying,shrinkage,thermal conductivity,frost resistance,high temperature resistance and pore structure properties of slag-based geopolymer foam concrete(SGFC)with different coal gangue substitution rates were studied by physically activating coal gangue into micropowder On this basis,the toughening modification of coal gangue-slag base geopolymer foam concrete(GSGFC)was studied by using basalt fiber nano-Al2O3.The main research contents are as follows:Firstly,the foam ratio with high stability GFC was determined,and the modification of foam by the type and amount of foaming agent and foam stabilizer were designed by orthogonal experiments.The results show that the foaming agent is LG-2258 diluted with 50 times water,the foaming stabilizer is modified silicone resin polyether microemulsion,and the dosage is 16%of the mass of the foaming agent,the foam density is 119kg/m3,the sedimentation distance is 14.5mm,and the water secretion rate is 65.4%,which can meet the requirements of performance and economy at the same time.Secondly,the change law of gangue substitution rate(10%,20%,30%,40%,50%)on SGFC performance was explored.The results show that with the increase of gangue content substitution rate,the fluidity of SGFC gradually decreases,and the compressive,flexural and splitting tensile strength of SGFC decreases,but this weakening slows down with age,and it is found that there is a strong correlation between the ultrasonic wave velocity and compressive strength.The incorporation of gangue will increase the dry shrinkage value of SGFC and reduce the frost resistance,but the thermal insulation performance effect will be enhanced and the pore structure will be improved.When the substitution rate is 50%,the thermal conductivity is 0.113W/(m·K);When the replacement rate is 30%,the SGFC decreases the most,and the antifreeze performance decreases rapidly when the replacement rate exceeds 30%.Under the 30%substitution rate of gangue,the effect on the hole structure of SGFC is the best,and the 28d compressive strength of SGFC is 1.8 1MPa.Based on the consideration of performance and solid waste utilization rate,SGFC under 30%gangue substitution rate was selected for fiber toughening research.Then,the influence of basalt fiber length(6mm,12mm)and volume content(0.15%,0.30%,0.45%,0.60%)on GSGFC performance was studied.The results showed that the fluidity of GSGFC decreased with the increase of basalt fiber content of the two lengths.Its mechanical properties and thermal insulation properties are improved,showing a trend of first decreasing and then increasing.At 0.45wt%,the mechanical properties of GSGFC of both fiber lengths were the best,and the compressive,flexural and splitting tensile strength of GSGFC with a length of 12mm increased by 8.1%,3.5%and 9.7%compared with 6mm under this dosage.At 0.6wt%,the two fiber lengths had the best inhibition of GSGFC shrinkage value,and the dry-shrinkage suppression effect of 12mm was better than that of 6mm.At 0.45wt%,GSGFC insulation was the best for both fiber lengths,with a thermal conductivity of 0.106 W/(m·K).In summary,GSGFC with a fiber length of 12mm was selected for freeze resistance and high temperature resistance test,and with the increase of fiber content,its quality,compressive strength and splitting tensile loss increased first after freeze-thaw cycle.With the increase of fiber content,the quality,compressive strength and splitting tensile loss increased first after high temperature resistance,and the frost resistance and high temperature resistance of GSGFC were the best at 0.45wt%.The pore structure of GSGFC was analyzed and it was found that at 0.45wt%,GSGFC had the smallest porosity and average pore size,and the pore structure shape was closest to the circle,which had a better pore structure.Based on the overall performance,GSGFC with a volume content of 0.45%basalt fiber and a length of 12mm was selected for nano-modification research.Finally,the influence of nano-Al2O3 content(1%,2%,3%)on the performance of GSGFC was studied.The results showed that the incorporation of nano-Al2O3 could improve the ease of slurry,and the fluidity of GSGFC increased with the increase of nano-Al2O3 content.When the nano-Al2O3 content is 2%,the mechanical properties and inhibition of drying shrinkage of GSGFC are optimal,and the compressive,flexural and splitting tensile strengths of 28d are 2.55MPa,1.19MPa,0.84MPa,respectively,and the shrinkage value is 2298×10-6m.The thermal insulation performance of GSGFC is best when the nanometer Al2O3 content is 3%,and the thermal conductivity is 0.112W/(m·K).When the nano-Al2O3 content is 3%,the frost resistance and high temperature resistance of GSGFC are optimal.When the nano-Al2O3 content is 2%,the porosity and average pore size of GSGFC are the smallest,and the pore structure shape is closest to the circle,which has a better pore structure.Therefore,based on the overall performance of GSGFC,the nano-Al2O3 content of 2%is the optimal ratio. |
PDF Full Text Request