(15 May 2017)

Motheo Infrastructure Contractors is carrying out repair work at the grain silos at the Port of East London for Transnet Port Terminals (TPT). The grain silos are a mere 50 m from the Indian Ocean, which has resulted in spalling of the concrete due to constant exposure from the damp, salty air.

Spalling refers to corrosion of the steel reinforcement in the concrete due 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, Site Foreman Roger Kirkby explains. 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,” Kirkby stresses.

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,” Kirkby highlights.

A particular challenge posed by the project is that some of the concrete slabs that needed to be inspected and repaired are at the top of the grain silos themselves, which are about 40 m high. Here the windy conditions experienced on the coast played a major factor in 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 was also responsible for the mechanical design portion of the project.

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 of Motheo 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.

View the full articel on the Concrete TV website

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