PhD Oral Exam - Nourhan Ali, 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

Canada has committed to reach net zero greenhouse gas emissions by 2050, and there are many ways to achieve that in the construction sector. Hence, there is a rising preference to replace traditional Ordinary Portland cement (OPC) with more sustainable and eco-friendly materials such as alkali-activated materials (AAMs) to reduce the total carbon emissions and energy consumption in concrete production. One-part AAMs ("just add water AAMs") have become promising binders with a low carbon footprint. It relies on activating industrial by-products, and one of the most promising is slag due to its high reactivity, which results in high strength and the absence of a need for heat curing. However, low workability, high workability loss rate, and rapid setting time of AAS are the most significant challenges hindering its implementation and halting the reliance on AAS. Many studies investigated the effects of various chemical admixtures on various AAMs to enhance workability without harming other mechanical properties. However, the information on the workability of one-part AAS is still limited. Furthermore, there has been limited investigation into the effects of mixing times, speeds, and styles (both continuous and discrete), retarders, and viscosity modifier admixture on the fresh, hardened, and rheological behavior of one-part AAMs, particularly when slag is used as the sole binder. Hence, a comprehensive investigation of these variables is essential to extend the use of one-part AAS in on-site applications. This research specifically aims to clarify the potential of producing high-strength ready-mix AAS by determining the behavior under long mixing times and using different retarders to enhance workability and slump life. Furthermore, the effect of viscosity modifier admixture on the behavior of AAS.