Coal ash as a natural additive for subgrade stabilization in the construction of low-volume traffic roads

Abstract

The road network in Colombia, as reported by the National Roads Institute of Colombia (INVIAS), comprises a total of 206,708 kilometers, with 142,284 kilometers falling under the rural roads with low traffic volume network category. Sadly, an estimated of 96% of these roads are in poor condition. The primary reason behind this issue is the presence of subgrades that exhibit inadequate mechanical performance, largely due to the lack of proper stabilization methods. Moreover, these roads often serve as the sole access and exit routes for rural communities, significantly impacting their connectivity with nearby urban centers. Recognizing this critical issue, this article proposes the use of coal ash for subgrade stabilization during the construction of low-traffic-volume roads. The study conducted demonstrates that coal ash can enhance the mechanical properties of subgrades, leading to an increase in strength and load-bearing capacity. The improved mechanical properties are attributed to the binding and reactive characteristics displayed by the coal ashes, which greatly contribute to soil stabilization. To verify these claims, a series of physical, mechanical, and strength characterization tests were conducted on both natural and treated clayey sand samples obtained from a rural population in Colombia. The detailed analysis of the results shows an improvement in the mechanical properties of the soil due to the use of coal ash as a stabilizing agent.