The New Solid Slab

The Cobiax CBX system is here to stay, as a highly effective solution for building slabs! It is efficient in structural and economic terms and straightforward to coordinate with other disciplines. It is an agile solution, easily adaptable to the introduction of prestress. As designers, we have adopted it in many of our projects and will continue to use it!

José Noronha da Câmara — Prof. Engº

Principles

The COBIAX CBX system is based on principles of economic and environmental rationalisation that enable the execution of two-way hollow-core slabs with behaviour similar to a traditional solid slab. The introduction of an ellipsoidal void in the zone where concrete contributes little to the overall performance of the slab allows optimisation of the slab thickness, improvement of its behaviour, and increased efficiency in the use of resources.

In a world where the sustainability of natural resources is of growing importance, the use of recycled materials for the voids and the reduction in concrete demand allow the COBIAX CBX system to promote, in itself, a structure with a lower environmental impact and a significant reduction in CO2 emissions inherent to the construction process.

Characteristics

The COBIAX CBX system consists of 2.50 m metal grids that serve as support for the top reinforcement and house the plastic formers — made from 100% recycled material — that create the intended voids within the slab. The volume of concrete that the ellipsoids allow to be eliminated results in reductions in slab self-weight of between 1.40 kN/m² and 3.37 kN/m².

Legend

Void height between 100mm and 260mm
For slabs from 0.20m to 0.40m

Design

The consideration of a COBIAX CBX slab at design stage should follow the procedures and criteria inherent to the definition, calculation, and detailing of a solid slab, with the introduction of inertia and shear resistance reduction factors in the voided zones and accounting for the load reduction resulting from the elimination of the respective concrete volume.

By considering the use of the COBIAX CBX system in the early stages of design, it is possible to immediately optimise seismic behaviour, vertical elements, and the loads transferred to the foundations, increasing the structural flexibility and reducing the costs of the overall building solution.

Ferca makes available on its website the Technical Manual "COBIAX CBX System" with a more detailed explanation of the calculation considerations and detailing requirements inherent to the system, and is equally available to provide support in the calculation, layout, and detailing process for your project.

Advantages

Structural Performance

Self-weight reduction of up to 32%
Reduced deflection
Improved seismic performance
Two-way load distribution
Possibility of reducing slab thickness
Possibility of eliminating beams and/or increasing spans
Fire resistance, thermal and acoustic behaviour similar to a solid slab

Economy

Reduced concrete and steel consumption
Savings on vertical elements and foundations
Elimination of top mesh supports
Faster execution compared to other voiding solutions

Sustainability

Reduction of CO2 emissions
Use of 100% recycled material
Greater efficiency in the use of natural resources

Effectiveness

Execution

Supply

The COBIAX CBX system is supplied ready to install on the slab according to a just-in-time logic, avoiding large storage volumes and unnecessary handling on site.

Special Export

For external markets, the Slim-Line range allows the components to be supplied separately for local assembly through a simple process, making it possible to transport up to 1,900 m² of COBIAX CBX per container — sufficient for approximately 2,500 m² of finished slab.

Installation

The COBIAX CBX system modules are composed of metal grids incorporating polypropylene ellipsoids. Their placement on site must comply with the specified spacing, maintaining orthogonality in the perpendicular direction.

Since the installation process is identical to that of a solid slab, it should begin with the placement of the bottom reinforcement mesh, on which the system grids are supported. The grids should be tied to the bottom mesh (2 to 3 points per grid). The top reinforcement mesh is placed directly on the grids, thereby eliminating the need for traditional bar chairs. Concreting should take place in two phases separated by 1 to 2 hours to allow the grids to anchor into the first concrete layer.

Configure your slab!