Capital Equipment News January 2017

With its large receiving hopper that can hold more than 16 t, the Vögele MT 3000-2 Offset ensures continuous paving, doing away with stop/starts of the paver.

ROAD TO QUALITY PAVEMENTS The conventional methodology of having a truck tipping directly into the paver constitutes many quality flaws that translate into excessive maintenance costs over the lifecycle of the pavement. To address this setback, in 2012, Sanral compelled the use of a material transfer vehicle on most of its road contracts, and this technology weighs in with key benefits that translate into reduced maintenance costs over the lifespan of a pavement, writes Munesu Shoko .

asphalt mix, causing material segregation. When segregated material is laid down on the pavement, it is compacted with poor structure or texture and eventually the mat lacks uniform density, causing the pavement to fail prematurely. The gradation of the aggregate and uniformity of the asphalt mix are both very important considerations for mix stability and road mat structure. To deal with these challenges, in 2012, the South African National Roads Agency (Sanral) decided to specify a material transfer vehicle on all its road contracts of 2 000m² and more. The road principal reasoned that the conventional method of having a truck feeding directly into the paver constituted many quality flaws that

I t is proven that aggregate and temperature segregation in hot mix asphalt is mostly the root of poor quality roads. In circumstanc- es where the mix has material or temperature segregation, the pavement will have areas with poor structure and texture. Large temperature differentials within the mix are prevalent during long hauls from the batching plant to the site or during colder days. As a result of long haul distances from a batching plant to a site, the top layer of the asphalt mix in the truck bed can have temperature variances of up to 50oC when compared with the rest of the material. Non-uniform compaction, ravelling, stripping and potholes can all be traced back to these temperature differen- tials in the mat.

Studiesinpavementfailurehavealsoshown that a major cause is material segregation. In conventional road construction a truck dumps material directly into the hopper of the paver. As the truck dumps the hot mix asphalt directly into the paver hopper, aggregates in the mix separate, changing the overall

“Most of the contractors we carried out trials with have since purchased our material transfer vehicle. This was also aided by our ability to meet and exceed Sanral’s expectations as far as the specifications are concerned.”

CAPITAL EQUIPMENT NEWS JANUARY 2017 16