Solution Features and Benefits

• A Fast-track Suspended Slab solution for poor soil
• Allows benefits of a Laser Screed floor
• Proprietary Design required – based on full scale testing
• Design and Construction is complicated
• No reinforcement bars required = time and cost savings
• High dosage of Steel Fibres provides good Crack Control

Design and Specification

Industrial Facilities are increasingly being constructed on reclaimed land and poor ground resulting in more Suspended Ground slabs being required.  Construction of conventionally reinforced Suspended Slabs is costly and time-consuming, with a high risk of random cracking.  In 1980’s and 1990’s full scale testing was done to establish design criteria for Steel Fibre reinforced Pile Supported slabs, and the design has been proved globally since the 1990’s..

Using a Pile Grid of between 3.0 x 3.0 m and 5.0 x 5.0 m and a heavy dosage of high quality Steel Fibres, heavily loaded concrete ground slabs can be designed and constructed without requiring reinforcement bars.  However a proprietary design is required from the Steel Fibre supplier and the Client should confirm that the Steel Fibre supplier or floor designer has the suitable Professional Liability insurance.  Early involvement of the Flooring Designer is critical with input into the type       of Piles and pile grid.  The aspect ratio of the panels must not be more than 1.25 and   ratio of span to slab thickness should be less than 20 to minimise the risk of excessive deflection.

Depending on loading and Punching Shear which is critical to the design, the slab can be supported directly on the Pileheads or on Slab Thickenings.  Either way, the slab should be fully isolated from the Sub-Base and other fixed structures to allow the majority of Drying Shrinkage to occur at Free Movement joints spaced up to 50 m apart and avoid mid panel cracking due to restraint.  Edge beams and columns may be required to support some of the slab loading so detailed discussions between all parties involved is critical at the early stages of the project design.

In order to provide the necessary Ultimate Flexural Strength of the concrete and maximum Fibre Spacing required to fully saturate the matrix, a high dosage of 45-50 Kg/ m3 of Steel Fibres is required.  It is recommended that high quality Steel Fibres specially designed for Structural applications are utilised, preferably having a high tensile strength of 1450 N/ mm3 and undulating shape to provide excellent crack control and pull out strength.  Some Steel Fibre suppliers apply designs incorporating reinforcement bars installed as effective beams connecting Pile heads, in addition to Steel Fibres, in order to reduce slab thickness.  However Clients must be weary of designs which are used to reduce the slab thickness to the minimum structurally acceptable, as often serviceability factors such as crack control and deflection are compromised.

Utilising the global resources of the CoGri Group, with the SR-SOP solution, CoGri Korea can give its’ Clients ‘Peace of Mind’ by providing a total Design-Build-Insure package.  The SR-SOP is a safe, modern and Fast-track solution for slabs on poor soil.

Construction Methodology

Although the Sub-Base is not required to transfer loads to the Sub-Grade soil, a Sub-Base layer of well compacted, well graded material is required to provide a solid working platform during floor construction and must be placed to a high tolerance of +0, -25 mm in order to prevent any restraint to shrinkage in the slab.  The Pile Heads and Slab Thickenings should also be trimmed or formed to a tolerance of +/- 10 mm.  The concrete mix design is even more important that normal for SR-SOP floors as the high dosage of fibres reduces workability and random cracking due to Drying Shrinkage is expected and must be minimised.  A high strength concrete of grade G30/ 37 is recommended.

The slab must be fully isolated from all fixed structures as with a SOG although edge beams and columns may need to be used as slab supports.  Details can be provided by CoGri Korea on request.  As with the JF-SOG solution, the Free Movement construction joints can be expected to open up by up to 25 mm.  Therefore Armoured Joints with heavy duty, individual Plate Dowels are essential to the long term durability of the slab.  As with all Suspended Slabs the location of any construction joints must be carefully planned in accordance with the floor designers requirements.

The floor will be constructed by Laser Screed with a Dry Shake Topping applied by Automated Topping Spreader and Power Trowelled to a burnished finish.  Curing is critical to provide the necessary strength and reduce any shrinkage cracking, as always.