Use of rice husk ash as a stabilizer to reduce soil loss and runoff rates on sub-base materials of forest roads from rainfall simulation tests

The impact of rice husk ash (RHA) as a stabilizer to reduce soil loss and surface runoff rates on sub-base materials of forest roads has been studied using a portable rainfall simulator at an intensity of 52 mmh-1. Thirty rainfall simulations were carried out on different combinations of materials: on the natural sub-base soils (5), on the materials stabilized with pure lime (5), and on the materials stabilized with different percent of RHA and lime (20). Results indicated that on natural sub-base soils, the runoff coefficient was 53.6% and mean time to runoff was 87 s. On the materials stabilized with pure lime, the runoff coefficient and mean time to runoff were measured 58.7% and 63 s, respectively. The lowest runoff coefficient was measured 36.6% on the combination of soil + 6% lime + 9% RHA. However, the highest mean time to runoff was recorded 198 son the combination of soil + 4% lime + 9% RHA. The maximum and minimum soil loss rates were found on the natural sub-base soils (212.2 g m(-2)) and on the combination of soil + 6% lime + 9% RHA (162.4 g m(-2)), mainly due to changes in maximum dry density (MDD), plasticity index (PI), optimum moisture content (OMC) and CBR of materials. On the basis of the results, we concluded that the rice husk ash not only increases the materials quality in soil stabilization methods with lime, but also reduces the runoff and soil loss rates on unpaved forest roads. (C) 2016 Published by Elsevier B.V.