Surface Treatment for Recycled Plastic Aggregate in Concrete: A Review

Abstract

The use of recycled plastic aggregate in cement-based materials has emerged as a promising strategy to reduce plastic waste and promote sustainable construction. However, the inherent hydrophobicity of plastic surfaces poses a significant challenge by limiting their bonding with the cement matrix. This review critically examines five major surface treatment methods—coating, oxidation, silane, plasma, and radiation—to enhance the compatibility of recycled plastic aggregates in cementitious composites. Coating with materials such as water glass, slag powder, or acrylic resins improved compressive strength by up to 78%, depending on the coating type. Oxidation using hydrogen peroxide or calcium hypochlorite increased hydrophilicity and improved strength by approximately 10 to 30%, while excessive treatment with NaOHhypochlorite mixtures reduced strength by up to 60%. Silane treatment significantly enhanced surface bonding, resulting in improved mechanical properties. Plasma treatment demonstrated high efficiency, reducing contact angles from ~108 to 44.0 degrees within 30 seconds. Radiation treatment using gamma rays and microwaves increased surface roughness and strength, with gamma irradiation at 100 to 200 kGy leading to substantial improvements in compressive strength and surface morphology. To the authors' knowledge, this is the first review to systematically compare the effectiveness, mechanisms, and limitations of these surface treatments specifically for recycled plastic aggregates in cement-based materials. This review also highlights the practical challenges of scaling such treatments, including energy demand, chemical handling, and cost, and identifies future directions, such as bio-based coatings and nanomaterial functionalization. The findings provide critical insight into optimizing surface treatments to improve the mechanical performance, durability, and sustainability of concrete incorporating plastic aggregates, supporting their broader adoption in sustainable construction practices.

Department(s)

Civil, Architectural and Environmental Engineering

Keywords and Phrases

hydrophilicity; plastic aggregate concrete; plastic waste; surface treatment

International Standard Serial Number (ISSN)

0889-325X

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 American Concrete Institute, All rights reserved.

Publication Date

01 Mar 2026

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