The Influence of Nanosilica on Unconfined Compressive Strength of Frost-Susceptible Soil

Abstract

In engineering practice there are numerous methods to improve the mechanical properties of subsoil. The paper presents the analysis of changes in the unconfined compressive strength of frost-susceptible soils stabilised with nanosilica (NS). Tests were conducted on samples of fine-grained soil at the maximum dry density (MDD) and optimum moisture content (OMC). Four variants of samples were prepared: soil without additive, soil with 1% NS, soil with 3% NS and soil with 5% NS. Due to the frost-susceptible character of the soil, tests were conducted on non-frozen samples and on samples subjected to ten cycles of freezing and thawing. Cyclic freezing and thawing of soil mixtures allowed for determination of the additive effectiveness in the temperature conditions encountered during the winter season. Based on the research results of unfrozen samples, it was determined that the addition of nanosilica leads to the increase in their unconfined compressive strength. On the other hand, the strength of pure soil samples after ten cycles of freezing and thawing decreased. This is a commonly known trend that results from the soil and soil mixtures freezing. However, in the same conditions, the unconfined compressive strength of samples stabilised with nanosilica demonstrated a significant increase with the increase of the additive content. The highest values were noted for samples stabilised with 5% addition of nanosilica. In order to explain the obtained results, further tests are required. However, the preliminary research has shown the effectiveness of nanosilica as an independent additive stabilising frost-susceptible soils, although it is not commonly used in engineering practice.