Wirtgen Slipform Paver SP 94i in the USA: A perfectly even runway

The new Wirtgen SP 94i slipform paver excels in the reconstruction of a runway in Missouri/USA.

With more than 30,000 take-offs and landings a year, Jefferson City Memorial Airport (JEF) is one of the most heavily frequented airports in the US state of Missouri. Thousands of visitors travel through it every day on their way to the government and congress offices in the state capital on the Missouri River. At the end of April 2016, work commenced on the reconstruction of a runway approximately 1800 m in length. It marked the premiere of one of the first type SP 94i slipform pavers to be delivered.

„The evenness that the SP 94i achieves is outstanding. That comes down to the innovative technological features of the new slipform paver. The uniform spreading of the concrete by the spreader plough and the slab paving kit with wear-resistant pad also play an important role.“ Adam Carroll, Head of Department, Lehman Construction Company

„The evenness that the SP 94i achieves is outstanding. That comes down to the innovative technological features of the new slipform paver. The uniform spreading of the concrete by the spreader plough and the slab paving kit with wear-resistant pad also play an important role.“ Adam Carroll, Head of Department, Lehman Construction Company

Precision work after just two days of set-up

The owner of the slipform paver, the Lehman Construction Company, got to work on the site as soon as the two days required for set-up of the machine were over. The 25cm-thick concrete layer was paved on a prepared base course which was also 25cm thick. Apart from dowel bars spaced at transverse intervals of 45cm and longitudinal intervals of 3.8 m, the runway does not have any continuous reinforcement. Some 20,000 m³ of concrete in total was laid on the runway, which is 1.8 km long and 30 m wide.

Inset pavers such as the SP 94i are ideal for the cost-efficient building of large concrete pavements, for instance on highly resilient motorways and runways.

Inset pavers such as the SP 94i are ideal for the cost-efficient building of large concrete pavements, for instance on highly resilient motorways and runways.

“The specification for surface evenness allowed for a maximum permitted deviation of 7.0 in per mile (18 cm per 1.61 km)”, explains Tim Nash, Director Concrete Products Wirtgen at Wirtgen America. “Since the machine first went into operation, we have not had a deviation of more than 1.0 in / mile (2.54 cm per 1.61 km) on any paving job. Usually, in fact, it was 0.0 in.”

Lehman achieved this high standard of evenness with practically unchanged factory settings, i.e. with no major modifications on the job site. The productivity was also impressive: each day the SP 94i paved concrete over an area up to 750 m long and 7.50 m wide. Due to high daytime temperatures of over 30°C, paving largely took place during the night hours.

Edges at 90° angle

The authorities also had stringent requirements on how the edges of the runway were shaped – the angle was to be exactly 90°. “The representatives of the construction inspection authority confirmed to us that they had never yet seen such precise edges,” Tim Nash recalls. “A vertical concrete edge is crucial for laying the next slab,” confirms John Gibson, Test Engineer at Burns & McDonnell, the company responsible for inspecting the construction work. “And this machine delivered a very good edge”.

The latest generation of machine control system automatically recognizes the machine configuration and sets the optimum machine parameters.

The latest generation of machine control system automatically recognizes the machine configuration and sets the optimum machine parameters.

Construction expert impressed by the quality

The SP 94i performed impressively in every respect: „The weight of the machine and the well-thought-out design ensure an outstanding surface. The quality is more or less built in, you can see that even in the tiniest details. It’s very impressive.”

The authorities also had stringent requirements on how the edges of the runway were shaped – the angle was to be exactly 90°.

The authorities also had stringent requirements on how the edges of the runway were shaped – the angle was to be exactly 90°.

Investment in leading technology pays off

Lehman’s decision to buy the new Wirtgen SP 94i slipform paver has been thoroughly vindicated. Kenny Lehman, Owner and Director of the Lehman Construction Company, put it this way: “We wanted to try out something new, because I’d heard that this machine could achieve a smoother surface than machines of competitors. With the SP 94ik we’re actually achieving even better surface accuracy than we had expected.” The process of setting the concrete paver up at the job site – which includes positioning and zeroing the crawler tracks and the swivel arms – is quick and easy with the SP 94i. “The crawler units work very well and the set-up time for the sensor system is short. All the settings can be done very quickly,” says Lehman.

While in Jefferson City the dowel bars had been placed in a reinforcement cage beforehand, the SP 94i also offers the option of inserting dowel bars and longitudinal joint bars in one operation during the concrete paving process. The dowel bar inserter (DBI) integrated in the frame on the machine inserts the dowel bars in the correct position in order to secure the height of adjacent slabs.

While in Jefferson City the dowel bars had been placed in a reinforcement cage beforehand, the SP 94i also offers the option of inserting dowel bars and longitudinal joint bars in one operation during the concrete paving process. The dowel bar inserter (DBI) integrated in the frame on the machine inserts the dowel bars in the correct position in order to secure the height of adjacent slabs.

Boosting competitiveness with the SP 94i

“The specifications in our contracts are frequently very strict, so everything has to be just so,” the owner added. “This machine will boost our competitiveness. The requirements on motorways can be met much more easily with the SP 94i. We’re really happy with this slipform paver.” The first project was already a complete success – Lehman delivered a first-class runway. Now the pilots taking off and landing at Jefferson City Memorial Airport can put this to the test.

Inserted automatically, the longitudinal joint bars prevent pavement slabs from moving apart.

Inserted automatically, the longitudinal joint bars prevent pavement slabs from moving apart.