Hünxe, 2 October 2020 – Pave 20 kilometres of two-layer compact asphalt in eight days – to achieve such demanding and unprecedented feats in asphalt , PORR Verkehrswegebau relies on the use of LEAN management and real-time support from digital tools such as the logistics control system Smart Site One, comprehensive compaction control and continuous surface temperature measurement.

In a joint venture, PORR Verkehrswegebau, the PORR subsidiary G-S Straßenbau, Bunte and Eurovia have been working since April 2024 to renew the carriageway of the BAB 3 motorway between the Hünxe and Emmerich junctions in the direction of Arnhem over a length of 39 kilometres in five construction phases, mostly with the motorway closed to traffic. The motorway is one of the most important transport links in Europe. In order to minimise the disruption on the diversion routes and to reduce the costs of the renovation, the client, Autobahn GmbH des Bundes, Rhineland branch, and the contractors have set themselves the goal of achieving new record times.

In 2022, PORR Verkehrswegebau had already rehabilitated ten kilometres of road surface in seven days on the BAB 3 between Emmerich-Ost and the Dutch border as part of a joint venture. ‘At the time, we thought that was the maximum. Now Autobahn GmbH has upped the ante and we have accepted the challenge,’ said Marcel Hemker, head of asphalt technology at PORR Verkehrswegebau, two years later.

In April 2024, the joint venture team had already completed 13.6 kilometres in the third and longest construction phase of what, according to the client, is ‘the largest road surface renewal project in Germany this year’. Work continued around the clock without interruption in several shifts in the direction of Arnhem between the Hamminkeln and Rees junctions. One hundred thousand tonnes of old asphalt were milled off, removed and taken for recycling before the same amount of hot mix was immediately re-laid. Each shift, 75 lorries transported asphalt from five mixing plants to the construction site. Two large milling machines, twelve rollers, an Inline Pave train and two material feeders were in operation around the clock to complete the motorway on schedule.

No reduction in construction time without digitalisation

‘The third construction phase was the warm-up for the freestyle,’ adds Luca Dreger, technical manager of the Münster/Dortmund branch of PORR Verkehrswegebau. After a long break in construction due to the European Football Championship and the summer holidays, as well as the postponement of one construction phase until September, the last three construction phases of the project in the direction of the Netherlands will be combined. This means that the asphalt paving work alone will have to be completed on 20 kilometres in 140 hours, i.e. in just under six days. This is a first on German motorways and is only possible thanks to a combination of innovative compact asphalt construction, lean-clocked processes and digital tools for logistics planning and ongoing quality assurance.

‘The coordination effort is truly enormous,’ continues Dreger. The paving processes, material planning, the timing for the removal of the milled material with subsequent recycling, the delivery of the mix and the handover to the next layers must run like clockwork. A plan B has been worked out for every eventuality, so that staff, machine or transport truck failures can be compensated for immediately.

The material milled off the 12-centimetre-thick old surface course is processed in the asphalt mixing plants and reused on the construction site. Asphalt binder and surface courses are paved in a single pass, ‘hot on hot’, using the so-called InLine Pave process. Since, in contrast to the conventional, three-layer asphalt construction method, the route is not driven on several times and no cooling times have to be observed between the application of the layers, this innovative process is almost twice as fast. A further advantage is the reduced consumption of materials. The surface layer does not cool down as quickly due to the hot binder layer below, so it can be applied at a height of up to 2.5 centimetres instead of the usual four centimetres. Calculated over the total length of 39 kilometres, this saves around 12,000 tonnes of asphalt mix. The hot-on-hot installation also requires less rolling pressure and ensures a good layer bond. After just 24 hours of cooling of the surface course, the markings can be applied.

Digital optimisation of material scheduling and transport

As large quantities of mix have to be paved at the same time, meticulous planning of production quantities and job site logistics is crucial. The project management team is using the SSO (Smart Site One) software for the resurfacing work on the A3 motorway. ‘I can see in the programme where the nearest mixing plants are in the area, I can create geometries and get real-time calculations of how much mix and how many transport trucks I need for continuous paving,’ explains Hemker. The site or project management can communicate directly with the mixing plant from the construction site and store delivery notes. The foreman at the paver can see how much mix is on its way, how much has already been paved and how much still needs to be paved in the current layer. Since the asphalt pavers communicate with the software via GPS, each mix delivery by the trucks is recorded and documented. ‘As a user, I can check at any time whether my quantity planning was correct, whether I need to re-plan and whether the actual loading cycle matches the original cycle planning,’ says Hemker. The SSO also serves as a central platform for collecting and linking data from other digital tools, such as the VÖLKEL company's comprehensive compaction control system. The data was supplemented with an infrared measurement of the surface temperatures directly after the compact asphalt was laid.

Real-time minimisation of sources of error during laying

The quality of the asphalt mix's compaction is crucial for the load-bearing capacity, grip and lifespan of a road surface. Until a few years ago, it could only be checked afterwards by taking core samples. There was no way of detecting uncompacted cracks and subsidence during the rolling process and making immediate improvements. That is why PORR Traffic Route Construction uses an electronic, comprehensive compaction control system to support roller drivers. It records data such as the position of the roller, the rolling speed and the number of passes. Vibration and temperature sensors detect whether the roller is compacting statically or dynamically. The in-house construction materials laboratory also communicates with the CCC and the rolling scheme is fed directly into the cockpit based on the latest measurements of the subsoil. In addition, the project management can document to the client that the entire paved area has been compacted equally well, which means security for the client.

The surface temperatures measured immediately after asphalt paving are also recorded in the SSO. Non-contact, full-surface infrared measurement behind the paver's screed is standard equipment for PORR traffic route construction. The paver operator or foreman monitor the paving temperature on a display and, since the infrared cameras are equipped with a GPS receiver, it can be verified that the specified paving temperature was maintained for the entire length and across the entire width, with a maximum deviation of two percent.

‘High-quality road construction will always depend on the commitment and expertise of the people involved. However, digitalisation has given us decisive advantages that go far beyond mere efficiency gains. The new tools enable us to push the boundaries of what is possible in road construction further. Furthermore, asphalt paving is a high-performance sport that requires extreme concentration under challenging conditions. With electronic live measurements of compaction quality and surface temperatures, we provide our clients with the necessary certainty and at the same time we noticeably relieve the teams on the construction site and especially in the cockpit,’ explains Hemker in conclusion.