Study On Mechanical Properties And Durability Of Modified Pisha Sandstone Composites

The Pisha sandstone is a special interbedded rock composed of sandstone,sand shale and argillaceous sandstone.Because of its characteristics of mud formation by water and sand formation by wind,soil erosion in the Yellow River Basin is extremely serious.At the same time,large-scale long-term siltation of sediment also poses a severe test to flood control safety.The Pisha sandstone belongs to the category of yellow mud and sediment.It can not only alleviate the problem of sediment deposition and promote the full utilization of resources,but also has important social and economic significance for the comprehensive treatment of the Yellow River sediment by means of modification.Based on the sixth project of the national key R&D project "Pisha Sandstone Resources Utilization and Eco-industrial Technology and Experimental Demonstration"(Project No.2017YFC0504506),this paper studies the mechanical and durability of Pisha sandstone under different mix ratio conditions and their influencing factors,aiming at modifying Pisha sandstone into a building material with certain strength.The main research contents are as follows:(1)The mechanical strength of modified Pisha sandstone was treated by alkali activation modification.The results showed that the strength of Pisha sandstone was low under the condition of no admixture.The compressive strength of Pisha sandstone was improved by the addition of activator.and the compressive strength of the modified Pisha sandstone tends to decrease with the increase of water consumption.(2)The mechanical properties of modified Pisha sandstone composites were studied by mixing fly ash and slag powder with Pisha sandstone.The results show that the compressive strength of the specimens increases with the increase of fly ash and slag powder content.Compared with fly ash,slag powder has a more significant effect on the strength of Pisha sandstone,and the strength of the modified specimens increases with the increase of activator content.When the slag powder content is 40%,the activator content is 5%,and the water consumption is 8%,the 28-day strength of the modified specimen reaches 22.34 MPa,which can meet the strength requirement of the artificial flood control stone.(3)The effect of curing age and specimen density on the compressive strength of modified Pisha sandstone-slag powder composites and its mechanism were studied.The results show that age has a significant effect on the early strength of modified Pisha sandstone.The strength of the specimens increases with age,but increases slightly after 28 days.The internal hydration reaction of Pisha sandstone mainly takes place in the early stage,and the later hydration reaction is slow.With the increase of specimen density,the strength of modified Pisha sandstone increases evenly.(4)The frost resistance and sulfate corrosion resistance of the modified Pisha sandstone-slag powder composite were studied.The results show that the strength and quality of the modified specimens decrease with the increase of freeze-thaw cycles,and the freeze-thaw resistance of Pisha sandstone increased with the increase of slag powder dosage.When the content of slag powder is less than 20%,the strength of specimens can still be maintained above 10 MPa after 25 cycles of test.With the increase of slag powder content,the sulfate corrosion resistance of the modified specimens is slightly enhanced.Generally speaking,the Pisha sandstone is less affected by sulfate erosion and has a certain resistance to sulfate erosion.