CORESTRUC SCOOPS AWARD FOR EXCELLENCE IN PRECAST CONCRETE
Corestruc was one of the joint winners in the Specialist Contractor and Suppliers category of Construction World’s Best Projects of the Year Awards 2019.
The company received the award for its participation in the construction of a new 10Ml reservoir in Bundu on behalf of the Thembisile Hani Local Municipality.
Thembisile Hani Local Municipality is the first municipality in South Africa to use the company’s new precast concrete system, which accelerates construction of reservoirs.
“This achievement would not have been possible without the immense support from Thembisile Hani Local Municipality. This is in addition to its highly competent professional team, comprising consulting engineers, Ceenex Consulting Engineers and Mondeo Consulting, and main contractor, Mbako Projects & Trading,” Willie de Jager, MD of Corestruc, says.
A 10Ml reservoir can be completed in only six weeks versus the four to six months to only construct reservoir walls using conventional in-situ techniques, and this is without the risk of having to redo the work, considering the technically complex nature of these construction projects.
Reservoirs are complicated and time-consuming structures to build. Wall construction demands absolute precision to ensure water-tightness. This is followed by construction of the roof, which entails erecting and installing tons of scaffolding and formwork inside the structure. On most of these projects, work can, therefore, only take place at one or two faces at any time.
Alternatively, Corestruc’s system enables the construction of the floor, walls and roof simultaneously to significantly accelerate the process.
The company builds the roof and wall at its factories while the principle contractor completes the earthworks and the reservoir floor. This means that the critical path of the programme runs through the earthworks and foundations.
Perfecting the design of the system took over five years from conception. It is based on best international practice adapted for the unique African conditions.
Corestruc uses both vertical and horizontal tensioning to resist applied forces. This is opposed to conventional construction methods where reinforcing and post-tensioning is used to control applied forces.
About 6,6 km of post-tensioning ducts and cables were installed by hand between the joints of the wall panels in preparation for the grouting on this project. This is in addition to the numerous three-dimensional printed components that were used to secure the rubber cast that acts as the temporary shutter.
The grout, designed to reach a compressive strength of 100 MPa within four days, will react when the medium comes into contact with water when filling the reservoir.
It also must extremely flowable so that it can be pumped through all the post-tensioning ducts from a single position using two static pumps. The pumps deployed at Bundu could be quickly slowed down and accelerated to ensure that the correct quantity of grout was applied between the various panels. The working time of the grout was extended by cooling it to 7°C and took up to 40 hours in a continuous process to pump it around the entire circumference of the two reservoirs.
The company then completed the construction of the outer section of the roof and ended with the stitching of the hollow-core slabs with a 35 MPa concrete to form a durable monolithic slab structure.
Corestruc is now preparing to manufacture another two 10 Ml precast-concrete reservoirs, and is hoping to be appointed to work on a 25 Ml reservoir project shortly.
More information at www.corestruc.co.za
