A mix of concrete for MeerKAT extension

The precursor to the trailblazing Square Kilometre Array (SKA) mid-frequency radio telescope project, the MeerKAT radio telescope is being further expanded with another 20 dishes. Concor was awarded the project to provide the civil engineering elements for the extension earlier this year and is now on site and busy with the construction of roads, dish foundations and other infrastructure.

An astronomical project

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. The SKA will be the world’s largest radio telescope and the MeerKAT project has already allowed astronomers to deliver unprecedented results.

Its remote location in an arid area about 90km from the town of Carnarvon is ideal 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 work on site in September 2021.

Piling it on

“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 are based on piles with a concrete cap. Each of these foundations has eight piles of 750mm diameter and 7-11m depth.”

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 antennae are able to resist the force of winds, especially as the dish has a wide surface area,” says Venter. “There’s also no room for any vibration of the dish.”

The 1,7m-tall galvanised bolt cages – constructed to specifications locally – are carefully positioned on the blinding of the foundation cap before the rebar armature is

Each dish foundation will have eight piles that are 7-11m deep.

A mix of concrete FOR THE MEERKAT EXTENSION PROJECT

assembled, the shuttering installed and the concrete poured. After the pour, the top of the bolt cage extends from the foundation for securing the dish pedestal or tower.

Pre-tests and modifications

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 telescopic equipment is designed to detect extremely weak radio signals from astrophysical sources and can easily be damaged by RFI from vehicle electronics, cellular phones and a wide range of other tools

(Above): Pre-fixed pile steel in the laydown area. (Right): Concor, in partnership with OptiPower, is building the foundations and infrastructure for 20 more dishes for the pioneering MeerKAT radio telescope.

and equipment. For this reason, Concor’s offices, workshops and laboratory are in Carnarvon and personnel must commute to and from the site each day.

“We’ve tested and modified all our on-site equipment to comply with the RFI limitations,” says Venter. “This includes excavators, trucks, graders, compactors, telehandlers, water bowsers, tractor-loaderbackhoes and our specialised concrete batching truck.”

Self-batching concrete trucks

The Reimer concrete truck is a selfbatching 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 19mm 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 60m³ of concrete, while the larger four foundations each consume 144m³.

“We’re also employing a recycler on this project to prepare the wearing course layer for much of the 40km 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 70km of trenching, for electrical and data cables to run from the antennae to the Karoo Array Processor Building.

The project is due for completion by September 2022.

(Above): The MeerKAT project is situated about 90km from Carnarvon, with its remote location in an arid area. (Photograph courtesy of the SA Radio Astronomy Observatory)

(Above): Clearing for borrow pit 2 underway at the MeerKAT project.

“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.”