Study On Performance Of Mineral Powder-Steel Slag-Coal Gangue Mixture

Coal gangue is currently one of the largest stockpiled mining wastes,and steel slag is one of the main by-products of the steelmaking process.To achieve green and sustainable development,applying coal gangue,steel slag,and other materials to the road base can reduce engineering costs and achieve the reuse of a large amount of waste,solving environmental problems caused by accumulation.This article determines through literature review and trial testing that coal gangue,steel slag,and mineral powder are used as raw materials,and the correlation of the raw materials meets the requirements for road use.Through comprehensive analysis,the range of raw material additives is determined,and the level of experimental factors is selected.Using uniform design to design 6 different mixture ratios,mechanical performance tests were conducted.The unconfined compressive strength of the mixture at 7 days reached 2.14 MPa-6.46 MPa,the rebound modulus at 180 days reached 954 MPa-1098MPa,and the splitting tensile strength at 180 days reached 0.66 MPa-0.83 MPa.Through regression analysis,a regression model was established using Minitab software between the relative dosage of admixtures and the three mechanical properties of the mixture,and the reasonable relative dosage of admixtures was obtained by combining the three regression models.Based on the research results of mechanical properties,ratio 1 and ratio 6 were selected for freeze-thaw cycle test and dry-wet cycle test to verify the durability of the mixture.The results met the standard requirement of residual compressive strength ratio greater than 70%after 5 freeze-thaw cycles after 28 days of curing.After 15 dry wet cycles,the unconfined compressive strength shows an overall upward trend.Conduct water immersion expansion rate test on 6 groups of mixtures.The test shows that the frost resistance of the mixture meets the requirements of road use,and it has good water stability when used as a pavement base.An unconfined compressive strength variation test was conducted,and XRD and SEM measurements were conducted on the mixture at curing ages of 7d,28d,and 180d.The results showed that the hydration products of the mixture mainly include Ca Al₂（Si O₄）₂,C-S-H,and Ca（OH）₂,and the internal structural system of the mixture is dense.XRD testing was performed on specimens from the 28d dry wet cycle test group and control group,and SEM testing was performed on specimens from the 28d freeze-thaw cycle test group and control group.The results indicate that the dry wet cycle promotes the acceleration of the internal reaction process of the mixture.After the freeze-thaw test of the mixture,some fault damage marks and exposed voids between the aggregates appear,but the internal dense structure remains unchanged.Field test section paving was carried out in Guangping County,Handan City to verify the actual engineering application of the mixture,and the precautions in paving were proposed.The application status of the experimental section is good,and the mixture of mineral powder,steel slag,and coal gangue can be promoted and used in road engineering.