Civil Engineering March 2022 | Vol 30 No 2

44 March 2022 Civil Engineering the reservoir and to supervise the works programme. With more than a decade of experience in precast concrete technology and municipal services delivery infra- structure, Infinite Consulting Engineers also played a critical role in the design of the system. As an extension of the principal engineering consultant’s office on this project, Infinite Consulting Engineers also provided professional project input. This is in addition to collaborating with Tango’s Consultants to ensure that the various aspects of the work scope integrate seamlessly so as to avoid delays. Infinite Consulting Engineers also ap- proves and accepts liability for the final precast concrete structure. These skills and experiences are being complemented by those of Corestruc, which brings to the project extensive concrete design and application, as well as significant rigging and erection expertise and capabilities. REDUCED CONSTRUCTION TIME The roof and walls were erected in as little as three months after the cast-in-situ floor and bases for the precast concrete roof structure and ring-foundation for the prefabricated wall was completed by the principal contractor, Anita Building. Anita Building was also tasked with the earthworks and site terracing, as well as the construction of the inlet and outlet chambers and all inter-related pipe work. Moreover, the company was responsible for training a large group of sub-contractors and locals from poor communities located within the project footprint to work on less onerous aspects of the works programme. Up to 30% of the contract value has been set aside for socio-economic development. By harnessing precast concrete tech- nology, the various trades are able to work simultaneously to save on construction time. Using conventional methods, work commenced with the construction of the concrete floor slab and then the walls. The most complex and time-consuming aspect of the build, namely the reservoir roof, was left as one of the last items in the construction programme, with work on its supporting columns only commencing once the wall had reached a predeter- mined height. PRECAST CONCRETE An approved manufacturer produces the various precast concrete elements during the earthworks and construction of the floor on behalf of Corestruc. On this project, Corestruc worked with CoreSlab, which was also the approved manufacturer of the precast concrete systems that were used to build the other three reservoirs for the City of Ekurhuleni’s Department of Water and Sanitation. The factory is the heart of the project and extensive innovation has been implemented to ensure both efficiency of the production process and quality of the various precast concrete elements that make up the reservoir system. For example, self-compacting concrete is used to manu- facture elements that contain significant reinforcing and where conventional vibrating pokers cannot be used effectively. Trial mixes were prepared and tested for strength and durability, while also taking into consideration the workability of the concrete. Working in a controlled environment, Coreslab is also able to ensure the perfect dosages of admixtures. This is to avoid overdosing that may delay early strength development, imperative for uninterrupted production. Another sig- nificant focus in the factory is to maintain the perfect water-to-cement ratio to ensure concrete strength. Aggregates from suit- able suppliers are also graded appropriately to avoid early concrete shrinkage. The prefabricated elements are inspected and approved for dispatch to ensure the accuracy of the placement of the cast-in components. Reinforcement By harnessing precast concrete technology, the various trades are able to work simultaneously to save on construction time The roof and walls were erected in as little as three months after the cast-in-situ floor and the bases and ring-foundation were completed