Composite flooring solution for Patershof Hotel: steel deck & extra light concrete

The site of the Martin's Patershof Hotel – the result of renovating and transforming a church into a four star hotel – was the first to implement an innovative solution combining composite flooring with lightweight concrete, namely Cofraplus® 77 LS, with Argex concrete consisting of expanded clay aggregates. This project was the culmination of nearly two years of research and development by ArcelorMittal Research Centre and the close attention paid by the engineers to Arval’s prescription to meet the needs of the builder-promoter.

The aim of the Martin’s Patershof Hotel project was unique: to create, within the heart of a nineteenth century church in Mechelen, Belgium - a five-storeyed hotel with 77 rooms in a single framework. The renovation and transformation of the site was the first to apply composite flooring with lightweight concrete. 

Composite flooring

Composite floor slab is a mixed construction system consisting of a steel sheet which serves as shuttering for concrete and reinforces the slab, totally or partially replacing the tensile reinforcements.

It is essential to achieve a bond between the steel and concrete that is stronger than the horizontal stresses to which the slab is exposed.

In this system, the concrete-steel bonding is achieved thanks to the special design of the steel sheets. These sheets are embossed with frustum-shaped projections, repeated indefinitely, both on their horizontal surfaces and on the sloping sides.

During assembly and concrete grouting, the self supporting steel deck constitutes a working platform.

A new solution for renovation

In new constructions, light flooring is particularly useful in multi-storeyed buildings because it significantly reduces the dead weight and lightens the structure and the foundations. But this product has also proved to be useful in renovation works where it is advisable not to overload the existing masonry beyond its limited bearing capacity. In addition, it enables increase in span length without forestay during the concrete grouting.

A solution suited for the Martin's Patershof Hotel project

ArcelorMittal’s decision to use Arval’s composite floor Cofraplus® 77 LS combined with Argex concrete is justified for several reasons. First, the configuration of the site required the manual transfer of all the materials through the entrance gate which was only 1.4 m wide.

Then, the thickness of the slab had to be 23 cm, taking the permissible dead weight by adding lightweight concrete up to 1.5 kN / m², which amounted to 450 tonnes for a floor space of 3000 m². The last reasoning was considered decisive by the contractor as the land on which the church is based does not allow the use of conventional composite floors.

The ultimate load bearing capacity was weak. Furthermore, the contractor wanted to avoid the use of concrete props in the middle of this dense structure with five floors.

Despite its well-known rigidity within the range of composite floors, Cofraplus® 77 did not have the permit to cross the limit of 3.2 m with 23 cm of normal concrete. The Argex concrete had the permit to do so. The project technicians used structural concrete with density ranging between 16 and 18 kN/m3 instead of 25 kN/m3. Hence, for a 15 cm thick slab, there was a reduction of about 1 kN / m².

An innovation that met all the objectives: stability and fire resistance for engineers in addition to approved planning and financial savings for the developer-contractor.

Text & photos: ©Arval by ArcelorMittal