PhD Oral Exam - Ahmed Khaled Ahmed, Civil Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

The increasing urgency of mitigating climate change has accelerated the shift toward sustainable construction materials with reduced carbon emissions. Alkali-activated materials (AAMs) have emerged as a promising alternative to Portland cement, offering significant CO2 reduction while maintaining comparable mechanical and durability properties. However, similar to conventional binders, AAMs remain vulnerable to cracking and deterioration under extreme conditions, such as fire exposure. This research aims to develop a low-carbon, high-resilience construction material by enhancing the post-fire autogenous self-healing ability of alkali-activated slag (AAS). The study investigates the self-healing potential of AAS exposed to elevated temperatures (200°C, 400°C, 600°C, and 800°C) under different curing conditions, including water, ambient air, and sodium hydroxide solution. Furthermore, the incorporation of self-healing agents such as crystalline admixtures (CA) will be explored to maximize self-healing efficiency. The experimental program, including compressive strength tests, ultrasonic pulse velocity (UPV), water sorptivity, rapid chloride penetration test (RCPT), scanning electron microscopy (SEM), and X-ray diffraction (XRD) reveals a notable recovery in both mechanical and durability properties after self-healing. By leveraging the inherent reactivity of un-hydrated slag and promoting the crystallization of healing products, this study advances the development of fire-resistant, self-repairing, and environmentally sustainable construction materials. The findings contribute to a more resilient built environment, ensuring improved structural performance and sustainability amid evolving climate challenges.