Controllable hydrophobization of sands with self-healing polymeric microcapsules

• Published in: Acta geotechnica Vol. 19; no. 9; pp. 6427 - 6442
• Main Authors: Qi, Rui, Chen, Ke, Lin, Hongjie, Lourenço, Sérgio D. N., Kanellopoulos, Antonios
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2024; Springer Nature B.V
• Subjects: Alginic acid; Calcium; Calcium alginate; Cargo; Complex Fluids and Microfluidics; Contact angle; Controllability; Degradation; Drying; Effectiveness; Encapsulation; Engineering; External stimuli; Foundations; Geoengineering; Geotechnical Engineering & Applied Earth Sciences; Granular materials; Hydraulics; Hydrophobicity; Microcapsules; Microencapsulation; Parameter identification; Polydimethylsiloxane; Research Paper; Sand; Seaweed meal; Self healing materials; Soft and Granular Matter; Soil; Soil degradation; Soil investigations; Soil properties; Soil Science & Conservation; Soil stresses; Soil water; Soils; Solid Mechanics; Time measurement; Water drops; Water infiltration; Sands; Microcapsules; Hydrophobicity; Release behavior; Polydimethylsiloxane; Calcium alginate
• ISSN: 1861-1125; 1861-1133
• DOI: 10.1007/s11440-024-02294-z

Hydrophobized soils have functional hydrophobic coatings to delay or restrict water infiltration and thus prevent infrastructure failure and long-term degradation. Over time, hydrophobized soils will be subjected to degradation under the action of external stresses, leading to the loss of its functional properties. Microencapsulation approaches, initially developed for self-healing applications emerge as a potential solution to enhance, switch (from hydrophilic) or prolong the longevity of hydrophobized soils. The aim of this study is to produce and investigate the effectiveness of microencapsulation to impart hydrophobicity in granular materials in response to external stimuli. In this research, polydimethylsiloxane (PDMS), with hydrophobic properties, is encapsulated in calcium alginate microcapsules with the ionic gelation method. The effectiveness of the microcapsules to induce hydrophobicity is investigated by mixing sand with microcapsules and quantifying the change of the contact angle and water drop penetration time (measures of hydrophobicity) under an external trigger, i.e., under drying and consecutive wetting–drying cycles. The results show that microcapsules release the hydrophobic cargo (PDMS) during shrinkage. After drying, the PDMS content in sand increased to 0.1–0.8% by mass of sand. The released hydrophobic cargo (PDMS) induced hydrophobicity in sands, reflected by a contact angle increase from 29.7° to at least 87.7°. The amount of polydimethylsiloxane encapsulated is a key parameter controlling the release of hydrophobic cargo. In addition, 4% capsule content in sands is identified as an effective microcapsule content in inducing hydrophobicity.