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, South Africa’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.
LNW Consulting Engineers also supervised the repairs, which were undertaken by Rodcol Contracts, a reputable concrete repair specialist with a solid track record providing quality services to all industries in the Zululand area, Swaziland, Natal Midlands, Mozambique and the Eastern Cape.
Walter Muhl, Chief Executive Officer 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, SCP significantly reduces the maintenance of reinforced concrete structures, saving time and money over the long term,” Muhl 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.
Considering the sheer size of the silos, it was an extensive undertaking. Ore Silo 4 is 20m is diameter and 34m high; Char Silo 1 12m in diameter and 25m high; and the Lime and Magnetite Silos 7m in diameter and 17m high.
The most onerous and time-consuming process entailed first erecting scaffolding inside and outside of the structures to provide access to the work areas, the largest of which was Ore Silo 4 where SCP was applied over 2095m2.
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.
Considering that this was the first time that Rodcol Contracts used SCP technologies, the company received training on the correct application of the technology from Spraylock Africa. Spraylock Africa is the exclusive African distributor for Spraylock Concrete Protection based in Chattanooga, Tennessee in the 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; moisture migration; as well as addressing concrete permeability and carbonation. Moreover, SCP 743 locks in free alkali to mitigate efflorescence.
Inside the structures, Rodcol Contracts repaired the cracked and spalling concrete and a provided a new 50mm gunite layer.
“Spraylock Africa is proud to be associated with LNW Consulting and Rodcol Contracts, both reputable experts in concrete repairs. We look forward to working with these companies on future projects,” Carl White, Managing Director of Spraylock Africa, concludes.