خطاب نوايا لدكتوراه في الهندسة المدنية

Most of the buildings I have assessed over the past two years will have to come down, and their concrete will become rubble. Crushed and screened, much of it could become aggregate for new concrete. Whether it can go into beams and columns, rather than only into roads and fill, depends on one question: how to predict and control the quality of recycled aggregate1 when the rubble it comes from is mixed and of unknown origin. That is the question I want to study in a PhD.

My MSc thesis at the Islamic University of Gaza asked a narrower version of it. I cast 96 concrete cubes with 0, 25, 50 and 100% of the coarse aggregate replaced by crushed rubble, and tested their compressive strength and water absorption at 7, 28 and 90 days. At 25% replacement the concrete kept 94% of the reference strength; at 100% it lost more than a third. What the averages hid was the spread2: cubes made from different batches of the same rubble varied more than cubes with different replacement levels. When I presented these results at a conference in 2023, someone in the audience asked the question I could not answer3: how would a contractor know, before casting, which batch they had?

Since then my work has moved from the laboratory to the field. After three years as a site engineer with a building contractor, I spent 2024 to 2026 as a field engineer in a shelter programme, assessing about 600 damaged buildings4 and deciding which could be repaired safely. The work gave me a practical sense of what rubble actually contains: plaster, steel, tiles, plastics, and concrete of very different ages and strengths. In the laboratory I am at home with aggregate testing and mix design, and I analyse my results in R. For two semesters, from 2022 to 2023, I was also a teaching assistant in the concrete technology laboratory.

KU Leuven’s research on concrete with recycled aggregates and on durability testing is where I could turn this practical knowledge into method. I would like to begin by testing whether quick measurements on the aggregate itself, such as water absorption and density, can predict the strength and durability of the concrete made from it well enough to grade rubble at the crushing site. That is a first step rather than a full proposal5, and I would expect to shape it with my supervisor.