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.
Honeycomb coal ash was selected as phosphorus adsorbent to explore the influence of different factors on phosphorus adsorption performance for phosphorus containing wastewater. The structural, physical and chemical properties of coal ash were determined by SEM, BET and XRF analysis methods. The response surface methodology (RSM) was applied for experimental design of phosphorus adsorbent. The effect of five independent variables including initial concentration of phosphorus, coal ash dosage, coal ash particle size, adsorption time and pH on the phosphorus removal efficiency (R (%)) was studied in the ranges of 5-7 mg/L, 6-10 g, 180-220 mesh, 20-30 min and 6.12-6.92 respectively. 46 runs of experiments were designed by the Design-Expert software. The optimum conditions for initial concentration of phosphorus, coal ash dosage, coal ash particle size, adsorption time and pH were found as 6.34 mg/L, 8.17 g, 207.97 mesh, 23.33 min and 6.64, respectively. At these conditions, removal efficiency and desirability function were found to be 96% and 1.000, respectively. The results of kinetic model reveals that the adsorption process conforms to Pseudo-first-order kinetics Equation (R2 =0.9991). The briquette ash has a good application prospect for the actual treatment of phosphorus containing wastewater, which provides a certain treatment strategy for the restoration of damaged water environment.