Assessment of the Effect of Fly Ash and Nanosilica on the Geotechnical Properties of Forest Road Subgrade

This study aims to investigate the effect of nanosilica on the geotechnical parameters of soil stabilized with class C fly ash. For this purpose, the soil of a forest road subgrade in northern Iran was studied, and tests of Atterberg limits, standard compaction, unconfined compressive strength, and California bearing ratio were performed on the soil stabilized with class C fly ash. The optimal amount of fly ash to improve soil strength was found to be ۲۵%. Subsequently, experiments were conducted on soil-fly ash mixtures containing ۰.۵%, ۱%, and ۲% nanosilica. The results showed that adding up to ۱% nanosilica improves strength, while a further increase in nanosilica leads to a decrease in strength. With ۱% nanosilica, the compressive strength and soaked California bearing ratio of the sample containing ۲۵% fly ash increased from ۷۴۱ kPa to ۹۲۶ kPa and from ۲۷.۴% to ۳۶.۲% after ۲۸ days of curing, respectively. The reactivity and high specific surface area of nanosilica lead to accelerated hydration and an increase in cementitious products, which enhance the strength of the samples. The results also show that fly ash and nanosilica improve soil stiffness.

کلیدواژه ها:

Forest Road Subgrade ، Soil stabilization ، Geotechnical Properties ، Class C Fly Ash ، nanosilica ، Strength parameters