Author ORCID Identifier

https://orcid.org/0000-0002-0926-6986

Date of Award

17-8-2025

Document Type

Thesis

School

School of Civil Engineering

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.P.Bhuvaneshwari

Keywords

Fiber Reinforced Polymer, Organic Binder, Inorganic Binders, FEGC, Confinement Sustainability

Abstract

Retrofitting fire-damaged columns is essential for restoring structural integrity. This study evaluates the effectiveness of BFRP based Basalt fiber Engineered Geopolymer Composites (BFEGC). The performance of basalt fiber wrapping and BFEGC was tested for fire protection system and retrofitted system. An optimal BFEGC mix achieved a compressive strength of 55.34 MPa, with split tensile strength, flexural strength, and strain hardening behaviour of 15.5 MPa, 5.13 MPa, and 6% respectively.

Microstructural analysis was accessed for the optimum mix. Durability tests include water absorption, sorptivity, and RCPT which confirmed compliance with standards. Thermo gravimetry analysis (TGA) shows the minimal weight loss of 2-5%. BFEGC also demonstrated significant environmental benefits, reducing carbon emissions and embodied energy compared to conventional cement binders. Machine Learning (ML) models were utilized to estimate the compressive strength of concrete, proving more reliable than conventional methods.

Cylindrical and column specimens of normal and high-grade concrete were tested under axial loading after exposure to 300°C (30 minutes), 600°C (20 minutes), and 900°C (15 minutes), followed by gradual (GC) or rapid cooling (RC). Specimens were left unwrapped (GC-NW, RC-NW), wrapped as a fire protection system (GC-WBF, RC-WBF), and wrapped as a retrofitted system (GC-WAF, RC-WAF) before axial loading. BFEGC wrapping significantly improved the mechanical performance of fire-damaged columns, particularly in NS_600RC and HS_300GC specimens.

Enhancements were observed in ultimate load, confinement coefficient, energy absorption, and ductility index. Microstructural analysis confirmed key hydration products' formation at elevated temperatures. A thermo-structural analysis using ANSYS Workbench 2023 showed that BFEGC effectively functioned as an insulator, regardless of the cooling pattern. Implementing a repair technique before wrapping would further improve column performance under high intensity of temperature. BFEGC shows significant reduction in carbon emissions and embodied energy, compared to conventional cement-based binders for fiber-reinforced polymer systems. These findings underscore the importance of a sustainable BFRP-BFEGC (fire protection, retrofitted system) for RC columns under elevated temperature.

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