4 minute read
State-of-the-art concrete repair
Cutting-edge Spraylock Concrete Protection’s SCP technology was deployed in the successful repair of five concrete silos at Rio Tinto’s Richards Bay Minerals (RBM) operation, SA’s largest minerals sands producer.
SCP 743 was specified as part of the repair design by LNW Consulting Engineers, a leading provider of multidisciplinary engineering and project management services to the heavy industrial engineering and commercial sectors. On the company’s previous projects, SCP 743 enhanced concrete remediation practices. It fills the concrete capillaries and pores to waterproof the construction material. Tests have shown that concrete treated with SCP 743 can withstand 100m of negative head pressure. Depending on the mix designs, SCP 743 purges and/or encapsulates contaminants within the concrete capillary and pore structure, eliminating their contribution to reinforced concrete distress.
Enhanced concrete remediation
LNW Consulting Engineers also supervised the repairs, which were undertaken by Rodcol Contracts, a concrete repair specialist with a solid track record providing quality services to all industries in the Zululand area, Swaziland, the Natal Midlands, Mozambique and the Eastern Cape.
Walter Muhl, CEO of Rodcol Contracts, says a total of 4 725m2 of concrete was treated with SCP. “SCP is an extremely effective product, in terms of its ability to purge concrete of contaminants and provide permanent protection. While initially costlier than other available products on the market, it significantly reduces the maintenance of reinforced concrete structures, saving time and money over the long term,” he says.
Rodcol Contracts mobilised to site at the end of 2019. The repairs to the five structures, including Char Silo 1 and 2, Ore Silo 4, Magnetite Silo and Lime Silo, were successfully completed at the end of 2020.
Monstrous and time-consuming
Considering the sheer size of the silos, it was an extensive undertaking. Ore Silo 4 is 20m in diameter and 34m high; the Char Silos are 12m in diameter and 25m high, and the Lime and Magnetite Silos are each 7m in diameter and 17m high.
The most onerous and time-consuming
process entailed first erecting scaffolding inside and outside the structures to provide access to the work areas, the largest of which was Ore Silo 4, where SCP was applied over 2 095m2 .
The external repairs first entailed removing the spalled and cracked concrete and then cleaning and treating the exposed reinforcing bar with an epoxy coating. SCP 743 was then applied to the opened concrete area to neutralise the concrete and bring it back to an acceptable level. Once the repair was completed, SCP 743 was applied to the repaired concrete and the surrounding areas. A Sika repair system and protective coating was then applied to complete the repairs.
(Top): SCP 743 was specified for the repair of five concrete silos at Rio Tinto’s Richards Bay Minerals Operation by LNW Consulting Engineers.
A first for Africa
Considering that this was the first time Rodcol Contracts had used SCP technologies, the company received training in the correct application of the technology from Spraylock Africa, the exclusive African distributor for Spraylock Concrete Protection based in Chattanooga, Tennessee, USA.
A total of 0,25L of SCP 743 is applied to a square metre of concrete using an airless spray machine. SCP 743 penetrates deeply into the capillaries and pores of the concrete, conditioning it and improving the pH levels to help protect the embedded reinforcing steel. In addition to contamination, the technology successfully addresses de-icing salts and freeze-thaw damage, as well as moisture migration, while also addressing concrete permeability and carbonation. Moreover, SCP 743 locks in free alkali to mitigate efflorescence.
(Right): The petrochemical sector depends on fastacting, effective concrete repair.
Inside the structures, Rodcol Contracts repaired the cracked and spalling concrete and provided a new 50mm gunite layer.
“Spraylock Africa is proud to be associated with LNW Consulting and Rodcol Contracts, both of which are reputable experts in concrete repairs. We look forward to working with these companies on future projects,” says Carl White, MD of Spraylock Africa.
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