VÖGELE InLine Pave for Placing Asphalt “Hot on Hot” at a Width of 7m
Horb is a picturesque German town on the upper reaches of the Neckar river, 437m above sea level, at the northern edge of the Black Forest. When securing a slope below the B 14 trunk road between two parts of Horb – Dettingen and Ihlingen – the roadway also had to be renewed. In its invitation to tender, the regional authority in Karlsruhe specified that the binder course and surface course must be built “hot on hot” as a compact asphalt pavement in accordance with regulation ZTV Asphalt-StB 07 (German terms and guidelines for the construction of asphalt roadways). This meant using either one module paver or two pavers. Contractor Reif from Baiersbronn won the day with its tender, based on the use of an InLine Pave train comprising three machines: a VÖGELE PowerFeeder MT 3000-2i Offset, a VÖGELE SUPER 2100-2 IP with AB 600 TP2 Extending Screed for the binder course and a VÖGELE SUPER 1800-3i with AB 500 TV Extending Screed for the surface course.
“InLine Pave was the obvious choice for rehabilitating the B 14,” explains Thomas Nagel of Reif. “Firstly, ’hot on hot’ was specified by the customer. Secondly, our experience has shown that InLine Pave ensures an absolutely perfect layer structure and an intensive bond between the layers – two essential prerequisites for more durable roads. What’s more, the machines making up our InLine Pave train can also be used for normal construction projects. This is because these are conventional machines which have only been slightly modified. In other words, we have killed two birds with one stone by investing in InLine Pave. As a medium-sized enterprise, that improves our chances of responding to invitations to tender for two-layer asphalt pavements.”
The method for more durable roads
InLine Pave is a particularly efficient means of building durable roads. Paving the binder and surface courses “hot on hot” offers several advantages. Instead of the usual 8cm binder course and 4cm surface course, for instance, a different ratio can be selected for the thickness of the individual layers. When using InLine Pave, the hot binder course prevents the surface course cooling too quickly. The higher temperature of the pavement makes it possible to pave thinner surfacings. In Horb, for instance, the surface course was just 2cm thick. The higher temperature of the surface course means that a higher density with fewer voids can be achieved during the subsequent final compaction by rolling.
The most important issue when paving the wearing course of stone mastic asphalt on the B 14 trunk road was to ensure that the amount of binder complied with the German terms and guidelines for the construction of asphalt roadways (ZTV Asphalt-StB 07) and the voids content in the surface course did not exceed 5 % by volume. A lower content of voids counteracts pavement ageing due to oxidation. High compaction increases the pavement’s permeability to water and its thermal stability, very effectively counteracting the formation of rutting.
The InLine Pave train
For the binder course, the contractor used a SUPER 2100-2 IP paver with transfer module which transferred the surface course mix supplied by the feeder directly into the material hopper of the paver placing the surface course. The transfer module has a heated conveyor to prevent the mix from sticking.
The SUPER 1800-3i used to pave the surface course near Horb is an all-rounder with an incredible range of potential applications. With a maximum pave width of 10m and a machine length of just 6m, it can handle motorway sites and trunk roads just as easily as tight traffic roundabouts. For “hot on hot” paving, the SUPER 1800-3i was additionally equipped with a water spraying attachment for the crawler tracks, as well as with a particularly large, insulated extra material hopper for 25t of mix.
The third machine – or more accurately the first machine – in the InLine Pave train was a VÖGELE PowerFeeder MT 3000-2i Offset. It receives the binder and surface course mixes supplied by feed vehicles and alternately transfers the mix with its pivoting conveyor directly into the large extra material hopper of the paver for the binder course or to the transfer module for the paver placing the surface course. The paver operator uses a system of lights to signal to the driver of the feed lorry whether binder course mix or surface course mix is required. The height and distance of the conveyor are adjusted automatically, for instance when the operator changes the position of the distance control switch from binder course mix to surface course mix. The feeder concept of the MT 3000-2i Offset means that the complete system comprising material feeder and paver can stock up to 45t and transfer up to 1,200t of mix per hour. Thanks to VÖGELE technology, a 25t feed lorry can be emptied completely in 60 seconds flat.
InLine Pave creates pavements of unrivalled evenness. This is based on the following principle: road construction by conventional methods is ideal for producing an even pavement. The base course, binder course and surface course are paved in three passes. The paver’s “auto-levelling properties” ensure that the evenness improves from layer to layer.
This principle is utilized to optimum effect by the InLine Pave process. By using two mutually independent pavers with floating screeds, any unevenness is levelled out to the same degree as during conventional paving. For InLine Pave, there are no special requirements made on the evenness of the base course. When using InLine Pave, the usual tolerance of up to 10mm is absolutely acceptable for producing a final surface course with maximum evenness.