Representatives from Tango’s Consultants recently visited one of Corestruc’s factories to see the high quality standards that the precast-concrete specialist deploys in its production lines.

The factory is essentially the “heart” of two new reservoir construction projects that the consulting engineering firm is undertaking on behalf of the City of Ekurhuleni Metropolitan Municipality in Springs, Gauteng.

Tango’s Consultants, a division of the Tango’s Group, was appointed the design engineer and is now supervising the construction works.

Lee Anne Dippenaar is the Engineer’s Representative (ER) for the construction of the reservoir in Selcourt and Mojela Thamae the ER stationed at the project site in Pam Brink. They are being supported on site by Wayne Wentworth, Tango’s Consultants’ Resident Engineer.

Anita Building is the principal contractor that will work alongside Corestruc which was also appointed to install the precast concrete system that signficantly accelerates construction by enabling the simultaneous construction of the floor, walls and roof.

The engineers were extremely impressed with the extent of local innovation by Corestruc, as well as quality controls in place at the factory.

They also noted the role that Corestruc was playing in creating long-term employment opportunities, in addition to its intense focus on skills development and training, which is complementing municipalities’ focus on labour-based construction via Expanded Public Works Programme projects. 

Manufactured while the principle contractor completes the earthworks, the reservoir system comprises a prefabricated roof structure, consisting of columns, beams and hollow-core slabs, as well as precast concrete wall panels and buttresses.

Corestruc first installs the centre portion of the roof system, starting with the placement of the columns onto the in-situ bases once they have been built by the principal contractor. 

The main contractor also ensures that the same high levels of precision are achieved throughout the construction of the ring beam by maintaining constant contact with Corestruc’s design and manufacturing teams.

Transported to site on just-in-time basis, the wall panels are lifted directly from the truck trailers and placed on top of the ring beam using a mobile crane. The first panel is supported

by props that are removed once it has set and the remaining precast-concrete elements are then placed against the other to complete the reservoir wall without the use of any support to free up space.

Similar to the erection of the roof structure, Corestruc’s installation team uses a Total Station to precisely install each panel, maintaining tolerances of about 5 mm.

The holes at the bottom of the wall panels align with the bolts grouted into the ring beam, as do the steel plates at the top with the voids in adjacent slabs and the holes that traverse the full width of the panels through which the post-tensioning strands are threaded.

Corestruc also invested many hours into refining the design of the buttress panels, which are used to reinforce the precast-concrete structure and therefore contain numerous cast-in components.

Notably, Corestruc uses vertical and horizontal tensioning to resist applied forces.

Kilometres of post-tensioning ducts and cables, as well as many three-dimensional printed components that are used to secure the temporary rubber shutter are installed by hand between the joints of the wall panels in preparation for the grouting.

The grout reaches a compressive strength of 100 MPa within four days and further reacts when the medium comes into contact with water when the reservoir is being filled.

Extremely flowable, the grout is pumped through all the post-tensioning ducts from a single position using two pumps, while the working time is extended by cooling the grout down to seven degrees Celsius.

Corestruc has a steady pipeline of reservoir projects, reflecting the efficacy and quality of its system.

Willie de Jager, Managing Director of Corestruc, says that impressed that so many young engineers from Tango’s Consulting also took time out of their busy schedule to visit the factory.

“They are the future of a profession that has come under increasing pressure to find more effective ways of delivering important infrastructure. The young professionals were exposed to home grown innovation early on their careers that will help them solve some of the service delivery challenges municipalities are currently facing,” De Jager concludes.