Influence of Mechanical and Microscopic Properties of Red Sandstone Modified by Different Solid Waste Materials

To improve the strength of red sandstone roadbed and elevate the utilization rate of solid waste materials, this study explored the enhancement of red sandstone using three types of solid waste materials: slag-micronized powder, fly ash, and waste incineration bottom ash. The mechanical properties of various solid waste materials, including compaction, unconfined compressive strength, and disintegration test results, were evaluated to assess the enhancement of red sandstone. Additionally, scanning electron microscopy was employed to analyze the microstructural alterations induced by these materials. The results indicated that the optimal moisture content of fly ash-improved soil and slag micropowder-improved soil gradually increased, whereas the maximum dry density decreased with an increase in the solid waste material admixture. At an 11% dosage of waste incineration bottom ash, the maximum unconfined compressive strength reached 2,386 kPa. The soil–water characteristic curves for the different solid waste materials exhibited a similar overall trend. Notably, the disintegration rate significantly slowed at a 9% dosage of fly ash, whereas at 11% dosage of waste incineration bottom ash, the disintegration rate nearly reached 0%, demonstrating optimal improvement effects. This suggested that the bottom ash effectively enhanced the water stability performance of red sandstone and increased its resistance to disintegration. Microscopic analysis revealed that slag micropowder and fly ash were comparatively less effective in enhancing red sandstone. The waste incineration bottom ash efficiently generated substantial cementitious material to fill pores. In summary, employing 11% waste incineration bottom ash was recommended to enhance red sandstone in practical roadbed improvement projects.