Hindle Mason Projects, a leading structural rehabilitation and corrosive/erosive specialist, is forging ahead with internal and external repairs to the refrigeration cooling towers No. 1 & 2 at Sibanye-Stillwater’s Beatrix 4 Shaft in Welkom, Free State.
The company continues to build on an impressive legacy providing specialist civil-engineering construction services to mines. This includes an in-depth understanding of the causes of structural failures and an ability to provide the best solutions available to restore their critical assets.
Mark Whiteman, a Hindle Mason Projects’ Construction Manager, says that the project is progressing according to schedule. “Work commenced on this project in September 2022, following extensive preparatory work in August. We have already completed the first cell with work now progressing on the second. At this rate, we are on track to finalise the work scope by the contract completion date. By this time, we will have restored the asset to its original state so that it can continue adding value for many more years. Notably, this work is being undertaken while again maintaining an impeccable health and safety track record throughout. We have not had single incident since we commenced working at the mine,” Whiteman says.
The project entails sound upfront planning considering the extensive preparatory work that needs to take place before Hindle Mason Projects can commence with structural repairs.
It can take up to a week to erect tons of scaffolding on one side of the structure. The scaffolding platforms are up to four storeys in height to enable Hindle Mason Projects to gain access to all the work areas. Access scaffolding is provided by the principal contractor.
Before scaffolding can be erected inside the structure, all mechanical and electrical installations need to be removed by the mine – also an onerous and time-consuming process.
A state-of-the-art solution was devised to repair areas of the structure where concrete has failed or spalled to a state of corroded reinforcing being exposed.
The team first breaks back the concrete to expose the 50mm diameter uncorroded rebar. Thereafter, edges are cut and prepared to avoid feather edging. Wet grit blasting is then undertaken to the reinforcing steel to SA2 standard before it is treated with a Sikamonotop 610. Reinforcing steel that has corroded beyond 10% of its original section is replaced with new steel that is lapped and tied in place.
The team hand patches repairs less than 50mm in depth with Sikamonotop 412 NFG, a fibre-reinforced, low shrinkage repair mortar. Larger areas are repaired with a proprietary shotcrete mix. Those areas that are difficult to access, such as the rims of the fan ducts and bunded areas, are repaired with Skikacrete 214 free flowing structural repair mortar using shutters.
As part of the work scope, the tower rooftop will receive a new polymer modified screed with a coat of Sikalastic 150, applied at a rate of 3,5kg/mշ.
High pressure water jet cleaning is undertaken to all substrates and surfaces, including the roof and structure, before application.
A Skim coat is also applied to uniform profiled areas with Sikamonotop 612 polymer modified fibre reinforced mortar and to reprofile areas from 5mm to 30mm in thickness. Sikamonotop 620 is used to reprofile areas of less than 5mm in thickness.
A protective coating, comprising two coats of Sikalastic 150, is then applied to the entire structure. Thereafter, the colour of the repaired areas is matched with the existing concrete to provide an aesthetically pleasing finish.
Whiteman describes the project as fairly straightforward considering the company’s wealth of experience providing cutting-edge concrete repair solutions to the mining industry.
“Our competitive edge remains the ability to provide reliable, cost-effective and time efficient concrete repair and corrosion protection solutions that are in line with the ISO 9001:2008 Construction Quality Assurance Programme. This is achieved while adhering to stringent health and safety standards as is demonstrated by our ‘Five Shield’ Dekra ratings. Our work for this client again demonstrates that we are committed to not only being good but the best at what we do,” he concludes.
