Construction of the Illovo Central mixed-use development, near Sandton, is on track for completion by March 2020.

The 15-floor building, which is being built by Concor Buildings, will offer a combination of office space and residential units.

The living units, from floors 9 to 15, will comprise 80 studio apartments, 36 one-bedroom units, 43 two-bedroom units and 12 three-bedroom units.

Floors one to five will comprise parking space and floors six to eight office space.

Bulk earthworks for Illovo Central started in May 2018, when 27 800 m³ of soil was removed for the first three levels.

Concor Buildings contract manager Fanie Stadler says this phase required the removal of considerable quantities of rock. In the southern corner of the property, the rock layers almost protruded at ground level.

Given the close proximity to other buildings in this well-developed suburb, Concor Buildings conducted smaller, controlled blasts to ensure the highest levels of safety. The planning and monitoring of these blasts also considered a Gautrain servitude tunnel below and a school across the road.

“Dust control was also a key issue, which we implemented and monitored closely in line with our stringent health and safety standards,” Stadler states.

The concrete structure has been built around a lift core for four passenger lifts and a fireman’s lift. Two tower cranes have been a feature of the skyline on this project, improving efficiencies on a site that is severely space-constrained.

One tower crane with its 60 m jib has focused its lifting on horizontal decking, while the other, with a 55 m jib, provided additional hoisting for column and the shaft core formwork and concrete.

“An interesting innovation that Concor Buildings has applied in constructing inner walls has been the use of Everite Hebel autoclaved aerated concrete (AAC) blocks. This lightweight building block has a number of benefits for modern buildings,” Stadler notes.

He adds that the lighter load on the concrete slabs meant that these slabs could be designed slightly thinner and with less reinforcing bar.

While a typical brick and mortar wall is about 350 kg/m², an AAC block wall load is closer to 90 kg/m².

The uniform surface of an AAC wall also allows for a thinner skim coat finish, rather than the usual 12 mm of mortar required for a normal brick wall. This has positive material and logistical implications as less water, sand and cement need to be transported to and around the site. Mortar is also mixed on site which makes for a generally cleaner site, with less dust.

Stadler highlights that the inclusion of AAC blocks has allowed Concor Buildings to demonstrate its building expertise and precision, while also further developing the skills of its subcontractors.

“With the benefits of these lightweight blocks come the demands of accuracy and attention to detail. Added skill is required in the block laying, as well as in the plastering.”

As part of Concor Buildings’ development programme, the company worked with the block supplier to train and mentor subcontractors in working smarter and enhancing their skill levels with new techniques. This delivered the exact tolerances demanded to closely match the building’s structure with the blockwork and the glazing.

The performance glass on the outside of the building is low-e, reflecting long-wave infrared energy to keep the inside of the building cool and reduce load on the air conditioning system.

A Marmoran wall coating is applied as a protective and aesthetic layer.

The project’s location on Rivonia road has demanded meticulous coordination of materials delivery by Concor Buildings, while council bylaws have meant no overtime can be worked in the suburb.

The construction team has, therefore, had to maintain tight working efficiencies to keep the project on track.