Composition Design Of Steel Slag-Based Solid Waste Cementitious Material And Its Semi-Rigidity Application Research In Grassroots

Steel slag,slag powder,fly ash and desulfurization gypsum are typical industrial solid wastes.The disposal of them not only occupies space resources,but also has a serious impact on the environment.The use of industrial solid waste to prepare cementitious materials instead of cement in the field of road building materials can not only achieve the purpose of resource utilization of solid waste,but also reduce the consumption of cement materials and achieve the effect of energy saving and emission reduction.It has both economic and environmental benefits and has a broad application prospect.In this paper,steel slag-based solid waste cementitious materials were prepared by grinding steel slag powder,S95 ore powder,fly ash and desulfurization gypsum.The effects of each component on the mechanical properties of solid waste mortar were analyzed by compressive and flexural strength tests.The microscopic mechanism of strength formation of steel slag-based cementitious materials was analyzed by XRD,FT-IR and TG methods.At the same time,combined with the strength and shrinkage properties of the rubber sand,the composition ratio of steel slag-based solid waste cementitious materials was determined,and the feasibility of applying steel slag-based solid waste cementitious materials in semi-rigid substrates was explored through the mechanical properties,shrinkage properties and frost resistance tests of the mixture.The main work and conclusions are as follows:Based on the simplex centroid method of mixture,the mechanical properties test of steel slag-based solid waste mortar was designed.By balancing the strength and shrinkage characteristics of mortar,the ratio of steel slag-based solid waste cementitious material was determined as steel slag powder 31%,S95 ore powder 38%,fly ash 27%,desulfurization gypsum 4%.In addition,in order to explore the influence of each component on the mechanical properties of rubber sand,the gray correlation degree analysis method was used to determine the influence of steel slag powder and S95 ore powder on the mechanical properties of rubber sand.According to XRD analysis,S95 slag and fly ash as mineral admixtures reduce the early hydration activity of cement,and the incorporation of desulfurized gypsum has no significant effect on hydration products.The incorporation of steel slag powder can promote the early hydration reaction of the cementitious system,and the presence of desulfurization gypsum can promote the synergistic hydration reaction of steel slag powder-S95 ore powder-fly ash system.FT-IR analysis showed that both fly ash and S95 ore powder reduced the formation of C-S-H in the early hydration stage,which was manifested by the weakening of the stretching vibration peak of Si-O in C-S-H at 1467.64 cm^-1.The incorporation of desulfurization gypsum promoted the formation of ettringite,which provided strength,so that the stretching vibration peak of Si-O in ettringite appeared at 1150～1200 cm^-1.TG analysis can also show that the C-S-H of the steel slag-based solid waste cementitious system has the most weight loss,the hydration reaction is more thorough,and the solid waste materials have a good synergistic reaction effect.Through the road performance test of the mixture,it is found that the early unconfined compressive strength of the steel slag-based solid waste material stabilized gravel mixture is lower than that of the cement gravel mixture,but its strength continues to increase during the curing process.The results of splitting strength and flexural strength tests show that the mechanical properties of steel slag-based solid waste cementitious material stabilized gravel mixture develop better with the increase of age,especially in the later stage of curing.The dry shrinkage test results show that the steel slag-based solid waste cementitious material mixture has lower shrinkage characteristics than the cement stabilized material,and has stronger adaptability in high humidity environment.The frost resistance test shows that the steel slag-based solid waste cementitious material mixture shows better frost resistance durability in the later stage,which is higher than that of cement stabilized gravel mixture.Through the on-site inspection of the solid waste cementitious material base layer test road paved by the S215 maintenance project,it was found that the test road section was not significantly different from the cement-stabilized crushed stone base layer in terms of construction technology,and the construction quality met the relevant specifications.The shape integrity of the core sample is good,and the unconfined compressive strength of the core sample meets the design strength requirements.After the construction,the condition of the test section was continuously observed.It was found that the development of cracks in the cement stabilized macadam base was more obvious under the same conditions,while the steel slag-based solid waste cementitious material stabilized base had a significant effect on inhibiting the development of early cracks.