AfriSam’s responsiveness and ability to deliver according to specification made this leading construction material supplier the preferred readymix concrete partner for the new Brakpan reservoir being constructed by Superway Construction.

According to Xolani Mbatha, technical product team leader at AfriSam, the company’s quality readymix creates concrete possibilities for the production of durable infrastructure.

“Productive collaboration between AfriSam and contractors is critical for the successful execution of any project, and this is especially so when it comes to defining and meeting product specifications and facilitating delivery within construction programme scheduling,” he says.

An excellent example of the success of such a cooperative partnership is clearly visible at the site of the reservoir currently under construction at Sallies Village in Brakpan.

The City of Ekurhuleni, as part of a commitment to address water capacity constraints within its region, has embarked on building 29 reservoirs during the period 2018 to 2021. This will see a combined storage capacity of 550 megalitres being added to the infrastructure.

Superway Construction won the contract for the construction of a new reservoir adjacent to the existing Brakpan reservoir amid fierce tender competition. Contract manager, Eugene Gibbard, acknowledges that being awarded this contract is gratifying for Superway Construction and recognises the contractor’s experience in a wide variety of construction and infrastructure projects.

The scope of this project includes the construction of the reservoir and all ancillary works including the perimeter fence, new access road, chambers and guardhouse. Elements where concrete is specifically required include the strip footings, walls, column bases, columns, column heads and roof.

The implementing agent, the Development Bank of Southern Africa, issued detailed project specifications and when completed, the 18-megalitre reservoir will be 8.2-metre-high with a diameter of 60 metres and will have a slightly sloped concrete roof.

AfriSam secured the contract to supply 2 500 m3 of readymix concrete based on its ability to meet the stringent quality specifications. All concrete supplied will be as per the consulting engineers’ material specification for an impermeable water retaining structure.

“Previous experience with AfriSam’s professional technical team and their responsiveness and ability to deliver according to client specification made them the preferred readymix concrete partner for this reservoir project,” Jurie Moolman, Superway Construction site manager, says.

SANS 2001-CC1-2012, the specification for structural concrete that is being used for this project, calls for fly ash as a supplementary cementitious material (SCM). As the standard operational mix supplied by AfriSam’s Sub-Nigel plant contains slagment, the operations team had to be pro-active in introducing a customised concrete mix changing from using slagment to fly ash in order to meet the project requirement.

The slump was initially specified at very low levels between 10 mm and 60 mm. This was of concern considering the high minimum binder content specified, ambient temperatures and the need to pump the concrete. Close consultation between AfriSam’s technical team, Superway Construction and the consulting engineers resulted in an agreed slump on 125 mm in conformance with SANS 878.

The careful calculation of the water:cement ratio to not exceed 0,5 ensured that the tight shrinkage specification of between 0.3 and 0.45 mm will be met. A crystalline waterproofer is incorporated into the mix to further enhance permeability properties while a CHRYSO curing compound will allow adequate cementing reactions to aid strength gain, impermeability, abrasion resistance and durability. A well-graded aggregate is used for this special application.

This custom mix underpins AfriSam's capability in designing and supplying a fit-for-purpose readymix concrete; in this case a workable mix which accommodates placing techniques and meets the project specification.

The reservoir will be constructed in three lifts for the full circumference, ensuring stability for the reservoir walls. This necessitated a continuous supply of readymix concrete and AfriSam allocated seven readymix trucks to each pour, and when required this was increased to 12 trucks.

Initial planning has already commenced for the roof to be poured in one pour. Moolman says that while this will be a daunting single pour of 630 m3, the volume of the pour will not be the biggest challenge; this will be to ensure an acceptable finish over such a large area. Detailed planning will be done to ensure all the required resources are available to achieve this milestone.

Queen Mabunda, territory sales manager at AfriSam, says that AfriSam has been able to contribute positively to maintaining the integrity of the project. “Our extensive experience and knowledge within the readymix sector and access to resources within the company, including the Centre of Product Excellence, allowed us to provide Superway Construction with the readymix solution it needed on this project. Further, our stringent quality control measures at AfriSam’s Sub-Nigel plant provided the assurance that the customer needed when it came to consistent product quality.”

AfriSam has supplied readymix concrete and technical advice successfully to a number of reservoirs constructed in the Ekurhuleni region. Mabunda says that the timely response of using fly ash to meet the project requirement will position AfriSam well in the market to supply other similar projects.

Work on site commenced in May 2019 with a contract completion date set for June 2020. Prior to the lockdown, Superway Construction was on track to hand over the project by the end of May, ahead of time and on budget.