Biopolymeric microcapsules and their evaluation as additives in sand improvement

Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China

^* Corresponding author: lourenco@hku.hk

Abstract

Microcapsule-based self-healing methods show great promise to extend the lifespan of ground infrastructure. This study builds upon the initial success of applying microcapsules to granular materials to enhance their strength. To expand the practical applications of this approach, this study designed and manufactured microcapsules with gelatin and gum Arabic shell, containing distinct cargo materials – tung oil, sodium silicate, and colloidal silica. These are newly developed microcapsules specifically for geotechnical applications. The physical properties of these microcapsules were characterized, and their effectiveness in shear strength recovery was evaluated through direct shear tests. The results demonstrate that sand improved with these microcapsules exhibited a significant increase in both peak and end of shearing strength. The mechanism behind soil strengthening with microcapsules lies in the hardening of released cargo from ruptured microcapsules, which bond soil particles and enhance soil cohesion. After a 28-day curing period, cohesion in sand improved with tung oil, sodium silicate, and colloidal silica microcapsules. Through a comparative analysis of microcapsule characteristics and their contribution to soil strength recovery, this study offers insights into the practical implementation of microcapsules in geotechnical engineering.