At the Naval Air Station Keflavik, the military air base on the international airport at the port of Keflavik, about 50 km from Iceland’s capital, Reykjavik, contractor HIB Iceland Ehf constructed operational facilities covering an area of around 75,000 m² by concrete paving. As the overall project was commissioned by the U.S. government, all measurements usaed during the paving project were in imperial units. The contractor had to overcome a number of challenges to assure the success of the project for the extension of the parking aprons and an upgrade of the hazardous cargo pad at Keflavik Air Base.
Paving with the SP 62i: 900 m³ of concrete per day
Paving was carried out in a single layer over a width of 7.62 m (25 ft) with a thickness of between 41 cm (16 in) and 45 cm (18 in) by a Wirtgen SP 62i slipform paver. On average, the team from HIB Iceland was able to pave 900 m³ of concrete every day. In total, the SP 62i paved around 35,000 m³ of concrete.
Given the climatic conditions on the Reykjanesskagi peninsula, in order to make the most of the time available a it was decided to do without fixed formwork for the individual lanes. To squeeze the work into this timeframe, the decision was made to do without prior placement of fixed formwork for the individual strips. Despite the tight deadline, the paving team was able to deliver highest quality results, not least due to state-of-the-art machine technology like the high-precision steering and levelling system and the automatic super smoother.
The SP 62i produces precise edges to ensure perfect surfaces and optimal drainage. Operational areas on airfields and airports generally have only a very slight cross-slope. In the case of the airfield project in Keflavik, the maximum permissible cross-slope specified was only 1%. Surface water drains off across the full width of the parking apron, in this case, 235 meters. The area was paved in 31 separate strips that were connected to one another by tie bars inserted along the sides to ensure the correct height of the individual sections. The outer edges of the strips posed a particular challenge for paving with the slipform method. They had to be precisely perpendicular from end to end and faultlessly paved with absolutely no fall. Only this can ensure that rainwater is drains away as it should during future operations, and that no water collects in the expansion joints.
The SP 62i: a precision tool
Perfectly perpendicular edges are essential for ensuring the quality of the butt joints between adjacent strips. The two-track SP 62i slipform paver once again proved to be the ideal choice for the job. The perfectly perpendicular edges speak for themselves.
The assistance with the formulation of the concrete mix provided by the Wirtgen application engineers contributes to the success of the project. Essentially, concrete is always a mixture of cement, water and variously sized aggregates. However, in order to fulfil the future load-bearing and wear-resistance properties of the construction in question, a number of other additives and a more precise consideration of the above-mentioned main ingredients is needed. The required properties for the extension work at Keflavik Air Base included, for example, a concrete with the compressive strength class C35/45. In order to achieve the desired compressive strength of 45 N/mm² (cubic concrete specimen), the ideal formula for the concrete mix was determined with the assistance of Wirtgen application engineers and optimised for paving with the slipform paver. In situ paving of the first pilot strips was able to begin immediately without trial areas. From the word go, these showed outstanding quality in all quality parameters such as density, compressive strength, profile-compliant placement and surface roughness, i.e. grip characteristics.
