Construction World December 2022

COVER STORY

The office block will comprise four basement levels and five office levels.

Yet another Green Star rated building is underway at Intaprop’s busy Oxford Parks precinct in Rosebank, Johannesburg, with black-owned contractor Concor working with construction materials leader AfriSam on 5 Parks Boulevard. AFRISAMCREATING CONCRETE POSSIBILITIES AT CONCOR’S 7 TH OXFORDPARKS BUILDING

C oncor has been active on this mixed-use precinct for many years, where the modern structure at 5 Parks Boulevard is now its seventh project. The company’s focus has been to ensure the completion of environmentally sustainable buildings on time and in line with the stringent requirements of the Green Buildings Council South Africa (GBCSA). Overseeing the project is Concor contract manager Martin Muller, who explains that the team has been on site since July 2022 – taking the process from the bulk earthworks contractor on four platforms with about 80 piles. The elegant office block – which combines a glazed and stone façade for enhancing the use of natural light – will comprise four basement levels and five office levels. It will provide about 7 300 m 2 of gross leasable area (GLA). “The design includes a triple-volume atrium in the reception area, extending from the ground floor through to the second floor,” he says. “There is also a double-volume area on the third and fourth floors.” The basic structure will comprise conventional reinforced concrete slabs from the basements to the roof, with a lift core to accommodate three lifts down to the lowest basement. Each level of slab consumes between 150 m 3 and 250 m 3 of 25 MPa readymix concrete, with the bulk supply of all readymix concrete being provided by AfriSam. The slab on each

level is placed in four pours, and the schedule calls for about two pours a week. Higher strengths of concrete – ranging from 35 MPa to 60 MPa – are used for the columns and verticals. “As a Green Star building, all the concrete mix designs are Green Star approved,” he says. “This ensures that the produced cement content reduces the overall CO 2 footprint of the structure.” The cement content in the various strengths of concrete is reduced through the use of 70-30 Green Star mixes, which allows 30% less cement by augmenting the mix with fly ash. “With its advanced concrete technology and extensive R&D, AfriSam is certainly one of the leading readymix suppliers in the industry,” he says. “Our experience is that their concrete strength over the curing period is very consistent, which reflects the quality of their mixes.” In addition to the quality assurance testing that AfriSam conducts, Concor conducts its own cube tests through an external company after every concrete pour. For the conventional slabs, these cubes are crushed to test their strength after seven days, 14 days and 28 days. “The consistency of AfriSam’s concrete strengths at each interval – which align with South African National Standards (SANS) – allows us to timeously de-stress the slab and recycle formwork to the next level,” he says. “This is particularly

4 21 st Best Project Awards 2022