The N12 highway is one of the South African National Roads Agency’s strategic priorities and it is for the N12 that civil engineering contractor Raubex Construction has been awarded the contract to implement a complete overhaul on Section 19 of the Gauteng Freeway Improvement Project.
The contract includes an intensive 30-month programme and calls for an emulsion and cement stabilisation mix for the subbase layers.
Three major new interchanges, successive bridge widenings and an east-and west- bound three-lane highway in either direction will replace the existing N12 dual-carriage- way system for about 10 km between the current Tom Jones and Daveyton on- and off-ramps.
For both the existing and new lanes, full depth reclamation and soil stabilisation will be carried out by Raubex’s recently acquired Cat RM500 rotary mixer. The RM500’s design incorporates separate water and emulsion pumps, which are simultaneously monitored in the cab through two separate flowmeters.
With an operating weight of 28 145 kg, the RM500’s Cat C15 Acert engine has a gross power output of 403 kW. Its width of cut is 243.8 cm, while the maximum depth of cut is 4.57 cm.
“We needed a high power-to-weight ratio on the N12 to cope with the existing varied premix materials, and the dual-mix stabilisation design makes the RM500 the optimal choice,” says Raubex Construction operations manager Wouter van der Merwe.
With the RM500, Raubex will reclaim and stabilise the 300 mm subbase in one go along the demarcated sections, he adds.
The equipment will comprise the Cat RM500, in addition to a Cat fleet that includes the latest-generation Cat 140K motor grader, as well as the Cat CS76 single-drum 20 t vibratory rollers.
This will be a construction road train with the RM500 pushing ahead two tankers, one carrying 18 000 ℓ of emulsion and the other 18 000 ℓ of water for the subbase phase. The emulsion ratio will be between 2% and 3% and cement 1.5% to 2%.
“What makes the N12 project particularly noteworthy is that all materials will be worked in place or sourced from cuttings that will make way for the new lanes and interchanges along the route,” Van der Merwe says.