Concor, the leading black-owned construction company, in partnership with OptiPower, is building the foundations and infrastructure for 20 more dishes for the pioneering MeerKAT radio telescope. A precursor to the Square Kilometre Array (SKA) – which will be the world’s largest radio telescope – the MeerKAT project has already allowed astronomers to deliver unprecedented results.
Its remote location in an arid area about 90 km from the town of Carnarvon is perfect for its purpose, providing a ‘radio controlled ’ backdrop for the mid-frequency array that enables the SKA’s work. According to Concor contracts manager Stephan Venter, the team commenced with the construction works on site in September 2021.
“With the piling rig on site, October saw our first piles drilled and concrete poured,” says Venter. “Soft soil and sandy conditions require that the 20 foundations will be based on piles with a concrete cap; each of these foundations has eight piles of 750 mm diameter and between seven and eleven metres deep.”
He highlights that precision is critical to the foundation construction, particularly the positioning of the bolt cage onto which each antenna pedestal is secured. These have to be accurate within fractions of a millimetre, to avoid any deflection when the dish ‘looks’ millions of light years into space.
“In addition to the accuracy, the foundations must ensure that the antennas are able to resist the force of winds, especially as the dish has a wide surface area,” he says. “There is also no room for any vibration of the dish.”
The 1,7 metre-tall, galvanised bolt cages – constructed to specification locally – are carefully positioned on the blinding of the foundation cap before the rebar armature is assembled, the shuttering is installed and the concrete is poured. After the pour, the top of the bolt cage extends from the foundation for securing the dish pedestal or tower.
Among the specific challenges of this project is the strict requirement to limit any radio frequency interference (RFI) in the vicinity of the MeerKAT telescope array. The highly sensitive radio telescope equipment is designed to detect extremely weak radio signals from astrophysical sources, and can be easily damaged by RFI from vehicle electronics, cellular phones and a wide range of other tools and equipment. Concor’s offices, workshops and laboratory are therefore in Carnarvon, and site personnel must travel each day.
“We have tested and modified all our on-site equipment to comply with the RFI limitations,” he says. “This includes excavators, trucks, graders, compactors, telehandlers, water bowsers, TLBs and our specialised concrete batching truck.”
The Reimer concrete truck is a self-batching unit chosen to do the work of a conventional batching plant, which in this instance was not justified by the relatively small volumes of concrete required. With 19 mm aggregate and crusher dust transported from De Aar, cement from PPC and tested water from local boreholes, concrete can be mixed in the truck on each foundation platform. The 20 smaller, piled foundations each take 60 cubic metres of concrete, while the larger four foundations each consume 144 cubic metres.
“We are also employing a recycler on this project to prepare the wearing course layer for much of the 40 km of gravel access roads,” says Venter. “This allows us to save water in this dry area, as the recycler introduces water into the layer and then closes it up – keeping the moisture in for longer.”
The machine can cover long, straight sections of road efficiently, preparing the way for the grader to level the surface before final compaction. Concor will also excavate and fill 70 km of trenching, for electrical and data cables to run from the antennae to the Karoo Array Processor Building (KAPB). The project is due for completion by September 2022.
The MeerKAT project is situated about 90 km from Carnarvon with its remote location in an arid area. (Photograph courtesy of South African Radio Astronomy Observatory (SARAO))
Construction works commenced in September 2021.
Clearing for borrow pit 2 underway at the MeerKAT project.
Soft soil and sandy conditions required foundations to be piled.
Each dish foundation will have eight piles, which will be between seven and eight metres deep.
Pre-fixed pile steel in the laydown area.
Concor, in partnership with OptiPower, is building the foundations and infrastructure for 20 more dishes for the pioneering MeerKAT radio telescope.