UK’s Biggest-Ever SFRC Flooring Project

By Eddy, Darryl

Specialist contractor Twintec Industrial Flooring has completed the UK’s biggest ever steel-fibre-reinforced concrete (SFRC) flooring project for Teseo in Livingston, Scotland. Taylor Woodrow Construction was appointed as main contractor for this multi- million pound investment by Teseo, with WA Fairhurst as project engineers. The project followed the Twintec tried-and-tested DBI formula – Design, Build, Insure – and was constructed by a highly skilled and experienced workforce who laid almost 250,000m2 of concrete flooring, contributing to a total project value in excess of Pounds 7 million.

Taylor Woodrow placed the order for the flooring works at a very early stage in the contract, which allowed detailed design development to take place with all parties involved. The exact requirements of the client, the main contractor and associated trades were therefore clarified during this process and incorporated into the project in good time. Coordination with other elements of the works ensured that the project ran smoothly and to programme.

Internal floor slab

Jointless ground-bearing SFRC floor slabs were designed and constructed in the chilled and freezer warehouses, an area totalling in excess of 40,000m^sup 2^. However, the mining history of dus area of Scotland required the ground under the very heavily loaded ambient warehouse slab to be fully suspended on driven precast concrete piles and this area took the total main building footprint to over 80,000m^sup 2^.

The choice of steel fibres as reinforcement provided a ‘jointless’ and very versatile surface that, combined with a fully compliant FM2 special flatness, is ideally suited to the intensive wear that occurs in modern heavily trafficked and heavily loaded distribution warehouses. A standard pallet racking configuration was to be installed in the ambient warehouse with individual racking leg loads of 85kN and a blanket uniformly distributed load of 50kN/ m^sup 2^.

To match these requirements, Twintec used a groundbearing, joindess SFRC design, 150mm-thick 40MPa concrete reinforced with 40kg/m^sup 3^ of AFT 1/50 undulated steel fibres in the chilled and freezer zones and a 240mm SFRC slab in the ambient area reinforced with 45kg/m^sup 3^ of AFT +1/60 undulated steel fibres.

External paving

The external paved area on the project totalled 148,000m^sup 2^ and needed to cope with huge vehicle movements. For this element of the works, Twintec used its standard jointless SFRC design and large pour placing system with a few modifications to suit the more changeable external environment within which the paving would need to operate. The proposal generated a 75% reduction in the amount of joints required and therefore fewer opportunities for joint breakdown and associated costs and disruption for the operation of the facility. The paving benefits from improved ductility and the reduced possibility of standing water is also a sttong safety benefit.

The Twintec solution was a ground-bearing, jointless SFRC design, 180mm-thick, having galvanised omega consttuction joints, 40MPa air entrained concrete reinforced with 40kg/m^sup 3^ of AFT 1/50 undulated steel fibres, levelled and compacted by laser screed or copperhead and finished by light panning and then brushing.

Delivery requirements

The local availability of large volumes of concrete, together with the need for a guaranteed delivery rate and consistent quality of product was a major problem that required a radical solution. Twintec chose to produce the concrete itself, with batching carried out by a partner company, Sitebatch Technologies, using a continuous mixing plant that is capable of outputs of up to 70m^sup 3^/hour. This provided Twintec with total control over the entire process, from specification of mix design and selection and procurement of aggregates, to delivery rates to the workface. The delivery rate (in excess of 600m^sup 3^ of concrete per day) to the workface also made it the ideal solution for the fasttrack nature of the works.

All of the internal floor slabs were specified as FM2 Special (Concrete Society Technical Report 34, 3rd edition^) and the survey results were outstanding; the tolerance has been verified by independent floor survey specialist and UKAS-accredited Face Consultants.

Concluding remarks

The project consumed 50,000m^sup 3^ of concrete, 2000 tonnes of ‘AFT’ steel fibres, 75,000 litres of Twinflow superplasticiser, 700 tonnes of Twintop dry-shake topping and 24,000 litres of Twinseal 90 curing agent/sealer. Twintec produced the 100,000m^sup 2^ of internal floor slabs (including vehicle maintenance unit, office pods and resource recovery unit in just 54 casting days and the 150,000m^sup 2^ of external paving in 130 casting days over a nine- month period. The surface of the floor slab is virtually fibre- free, and the survey results for flatness are outstanding.

Twintec was very proud to be part of the Teseo and Taylor Woodrow team involved on this highly successful project, where the commitment of all parties on-site was instrumental to the finished quality of the floor slabs. It believes that the project demonstrates the suitability of SFRC to the demands of the modern distribution centre and offers yet further evidence tiiat this technology is now widely accepted and increasingly popular for both groundbearing and suspended ground floor slabs.

Reference:

1. CONCRETE SOCIETY. Concrete industrial ground floors -A guide to design and construction. Technical Report 34, Third Edition, The Concrete Society, Camberiey, 2003, 138pp.

DARRYL EDDY, TWINTEC INDUSTRIAL FLOORING

Copyright The Concrete Society Mar 2008

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