Date of Award

2024

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Civil Engineering (MS)

Administrative Home Department

Department of Civil, Environmental, and Geospatial Engineering

Advisor 1

Qingli Dai

Committee Member 1

Zhanping You

Committee Member 2

Quang Ngoc Vinh Tran

Abstract

RCA typically exhibits weak interfacial transition zones (ITZ), high porosity, and micro-cracks due to residual mortar layers, resulting in suboptimal performance when reused in structural applications. To address these challenges, this study developed a wet carbonation process using glycine acid as an inducer. Glycine acid, containing carboxyl and amino functional groups, forms stable complexes with Ca²⁺ ions in RCA, increasing calcium ion solubility and thereby accelerating carbonation. RCA samples underwent carbonation in a glycine acid solution, followed by characterization using X-ray diffraction and scanning electron microscopy to evaluate mineralogical transformations and microstructural enhancements. The carbonation process promoted the formation of vaterite, a reactive polymorph of calcium carbonate, on RCA surfaces, which improved ITZ density and bonding strength with the cement matrix. As results, abrasion loss was achieved to 45.71% lower than 53.82% of untreated RCA, and California Bearing Ratio values increased by 28% at 5 mm penetration, indicating improved aggregate physical durability properties. Leachate analysis showed that carbonated RCA exhibited reduced to pH 8.47 and lower total dissolved solids at 0.263 mS, as the formations of calcium carbonate. Furthermore, recycled concrete mechanical tests indicated gains of 13% in compressive, 15% in tensile, and 12% flexural strength compared to untreated RCA concrete, reflecting increased strength gained and reduced porosity. These results demonstrate that glycine acid-induced carbonation enhances RCA properties and possibly offering a promising pathway for mitigating construction and demolition waste.

Available for download on Wednesday, December 31, 2025

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