Structural Deterioration of Reinforced Concrete Roofs in Marine Environments Due to Improper Rehabilitation Practices: A Case Study of the Central Bank of Yemen Building, Aden
This case study of the Central Bank of Yemen in Aden demonstrates that improper roof rehabilitation, specifically the accumulation of excessive superimposed layers, significantly accelerated structural deterioration in a marine environment, but strategic load reduction through material removal and drainage improvement successfully mitigated these risks by decreasing the column load by nearly 59%.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Imagine a building's roof not just as a shelter from the rain, but as a giant, invisible backpack strapped to the shoulders of the entire structure. In the world of civil engineering, this "backpack" is called the dead load—the permanent weight of the roof itself, including concrete, tiles, and any layers added over time. Now, picture this backpack being worn in a place where the air itself is salty and wet, like a beach town. In these marine environments, the salt acts like a tiny, invisible rust monster that eats away at the steel bars hidden inside the concrete, while the constant wetting and drying cycles make the concrete crack and flake. When engineers try to fix a leaky roof, they often add more layers to make it slope better or waterproof it. But if they do this without checking the math, they might accidentally make the backpack too heavy, causing the building's "shoulders" (its columns) to buckle under the strain. This is the delicate dance between keeping a building dry and keeping it from collapsing under its own extra weight.
This story takes place in Aden, Yemen, at the Central Bank building, where a team led by Abubaker M. Ba Rahim investigated a roof that was in serious trouble. The building sits just 600 meters from the ocean, meaning it is constantly pummeled by salty winds and high humidity. The roof was suffering from cracks, peeling concrete, and rusty steel bars. The big question was: Was the building just old and worn out, or had someone made a mistake while trying to fix it? The researchers found that the roof had become a victim of "over-rehabilitation." Before the study began, the roof was covered in a massive, 53-centimeter-thick stack of extra concrete and materials added over the years to fix drainage issues. This stack was so heavy that it was crushing the building.
The team decided to measure exactly how much weight this "backpack" was adding. They discovered that before they did anything, the roof was carrying a dead load of 9.759 kN/m². To put that in perspective, for one specific support column (called Column C20), this extra weight meant it was holding up an additional 375.53 kN (which is roughly 38.28 tons). That is like adding a small elephant on top of a single pillar! The researchers noted that because the original blueprints were missing, they couldn't say for sure if the building was supposed to hold that much, but they could see the damage: vertical cracks and rust were spreading because the column was overloaded and the salty air was eating the steel.
The solution was to take the heavy backpack off. The team carefully removed the excessive layers of concrete and replaced them with a much lighter, smarter system. They stripped away the heavy slope-forming concrete and ordinary concrete layers, swapping them for lighter materials like foam concrete and better waterproofing. The result was dramatic. After the renovation, the roof's dead load dropped to 4.003 kN/m². For Column C20, the weight it had to carry plummeted from 375.53 kN down to 154.10 kN. That is a massive reduction of 58.96%, meaning the column was suddenly relieved of nearly 22.56 tons of pressure.
The paper concludes that the damage wasn't just because the building was near the sea; it was because the previous repairs had made the roof too heavy for the structure to handle. The study suggests that fixing a roof in a salty, coastal area isn't just about slapping on a new waterproof coat; it is a structural engineering challenge. If you add too much weight without checking the math, you risk cracking the building's bones. By removing the unnecessary layers and using lighter materials, the team didn't just stop the leaks; they saved the building from being crushed by its own repairs. The key takeaway is that in coastal cities, every time you fix a roof, you must treat it like a structural surgery, not just a cosmetic patch-up, ensuring you don't accidentally strap a heavier backpack onto the building's back.
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