Construction company Motheo Infrastructure Contractors is carrying out repair work at the grain silos at the Port of East London’s State-owned freight utility Transnet terminals as result of the spalling of the concrete, owing to constant exposure to damp, salty air from the Indian Ocean.
Spalling refers to corrosion of the steel reinforcement in the concrete, owing to the ingress of water and oxygen through minute cracks that develop over time. Scales of rust form as a result, which expand, causing the concrete layer covering the steel to crack and fall away.
If allowed to continue unabated, the steel reinforcement rusts away to the point where the structural integrity of the structure is compromised. Motheo Infrastructure Contractors has a concrete division specialising in all forms of structural concrete work, explains Motheo site foreman Roger Kirkby.
“The first step is to remove the degraded concrete to expose the affected rebar, which can then be repaired. We remove all traces of rust, and then apply a primer and a final seal with a rust-resistant coating.”
He explains that, in severe instances where the steel has rusted away to the point where its function is compromised, the rebar is removed completely and replaced with new steel that is either spliced or epoxied to the existing concrete. Once the rebar has been repaired, a high-strength, non-shrink grout is applied to the spalled areas.
“This is a highly specialised process requiring care, skill and experience,” he highlights.
A particular challenge posed by the project is that some of the concrete slabs that need to be inspected and repaired are at the top of the grain silos themselves, which are about 40 m high. The windy conditions experienced at the coast are a major factor when erecting the scaffolding needed to be able to work at height.
The fast-track project has proceeded without any complications or delays to date, which Kirkby attributes to the experience and expertise of the Motheo crew on-site. Apart from the concrete-repair work itself, Motheo Infrastructure Contractors is responsible for the mechanical design portion of the project.
Motheo MD Archie Rutherford comments that this contract is an ideal showcase for Motheo Infrastructure Contractors – the civils division of the Motheo Construction Group. It specialises in roads and earthworks, as well as installation of services such as water, sewer and stormwater reticulation. It has also established a formidable concrete division specialising in all forms of structural concrete work.
“The vision is to build a truly empowered, all-encompassing, black-owned construction company. Over the next five to seven years, we want to develop into a diversified construction group, covering civils, building and housing,” Rutherford concludes.