Only experienced and competent companies master the specific application methods of steel fibre reinforced concrete. Specialist sub-contractor Twintec is one such company and has added another outstanding floor slab to their impressive product portfolio.
Twintec Industrial Flooring of Rugby, UK part of the Twintec International Group of Companies has designed and installed a steel fibre reinforced concrete (SFRC) ground floor slab for Al Azizia Panda United at their brand new regional distribution facility in Riyadh, Kingdom of Saudi Arabia. WSP Middle East Ltd was Project Managers with Davis Langdon Project QS. The facility will be fully automated, with the design of the handling systems managed by ILS of South Africa.
The slab was ground bearing with individual leg loads from pallet racking of 100kN and a UDL of 50kN/m². The flatness tolerance for the whole of the floor area was FM2 Special to the 2003 edition of TR34.
Solution To overcome the challenges presented by the project , Twintec utilised the following;
1. Design. Twintec's solution for this project was a jointless, steel fibre reinforced concrete (SFRC) slab, 190mm thick and reinforced with 40kg/m³ of AFT 1/60 steel fibres. The floor utilised a C35 concrete with a 0.5 water cement ratio and a flexural strength of 4.6N/mm².
2. Concrete. The size of the panels meant that a concrete volume of 400m³ was required on a daily basis. This, together with the need for guaranteed delivery rate and consistent quality of product was a major issue that required a carefully planned solution. Twintec chose to work with Al Falwa Ready Mix Company as they were geographically well positioned and able to guarantee sufficient resources to truck the project. 11 concrete mixer trucks were used to supply the site with capacities of 6 and 9m³. Al Falwa & Twintec kept good control over the quality, consistency and workability of the concrete and also the rate of production.
Key to the quality was the technical assistance of BASF who were fully engaged along with Twintec, Al Falwa & WSP in carrying out trial mixes until the optimum mix was selected. BASF supplied all the admixtures for the project and also the dry shake topping and curing agent.
3. Steel Fibre Reinforcement. High tensile undulated steel fibres, (60mm long and 1mm diameter) were used to reinforce the concrete and were supplied by Propex. Proper mixing of the fibres is essential, ensuring that a uniform distribution of the fibres takes place throughout the batch. In our experience, the most effective way of incorporating the steel fibres is with a pneumatic integration machine, as seen in picture 2.
4. Flatness. For operational purposes, the client was determined to create a flexible and versatile floor, and so specified FM2 Special. Twintec were consistently able to work to the specified tolerances, creating one of the flattest floors ever constructed in the Kingdom.
5. Design Co-ordination. This was perhaps the key to success on this contract; with the Twintec design team fully able to understand the specific needs of the structure and the fast track nature of the project. The floor slab was constructed to programme and within budget. Twintec carry out all aspects of the work from budget proposals through to detailed design along with full supply and installation. Twintec's team is entirely “in house” and includes structural engineers with over 20 years experience of designing concrete floor slabs reinforced traditionally and with SFRC.
6. Skilled Workers. Twintec carry a healthy reputation and their directly employed work force are renowned for producing floors laid to the highest standards of flatness in large area jointless pours without the need for remedial grinding. Whilst they have developed a few special tools and some unique techniques, it is essentially a question of the attitude and commitment of the workforce. To this end, the project is planned well, managed effectively, resourced correctly and the men are properly trained and supervised.
7. Site Co-operation. Vital to the finished quality of any floor slab is the commitment of all parties on site to a shared goal. Twintec were pleased to be part of the team involved on this project, where all concerned realised the vital importance of the floor slab to the long-term success of Panda
Using 13,000m3 of concrete, 550 tonnes of steel fibres, 250 tonnes of “Mastertop 300” dry shake topping and 7,000 litres of “Masterkure 181″curing agent / sealer, Twintec produced the floor slab in just 38 casting days over 3 visits. The surface of the floor slab is virtually fibre free, and the survey results for flatness are outstanding.
Twintec are pleased to discuss directly with design teams, clients and operators the most appropriate choice of floor type and flatness tolerance. The commercial and design teams at Twintec are happy to enter into very early negotiations with fund holders or their project teams and to provide design information and budget proposals; this service is available without charge.
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