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Concrete In Australia : September 2011
36 Concrete in Australia Vol 37 No 3 Using SFRC also reduces slab thickness, saves on excavation and cartaway costs and reduces the demand for cement and aggregates needed for the concrete. e most significant benefit of this technology is that it allows the use of the laser screed and other high performance machines which have transformed the concrete flooring industry, increasing output from a few hundred square metres per day to outputs in excess of 3000 m2 per day and allowing superior flatness tolerance to be achieved. e benefits of this technology to a contractor are summarised below: • reduced program time • improved quality • improved productivity • elimination of steel fixing • improved H&S (reduced tripping and handling hazards). 5.2 End user For the operator of a modern distribution facility, down time to repair the floor slab, or MHE damaged by a poor quality floor slab can be very disruptive. In addition, the curling of sawn joints in a traditional system can cause major disruption for MHE in terms of picking speed. A further potential problem is the need to respect the designer s criteria regarding proximity of racking legs to floor joints; the more joints there are, the greater the likelihood that conflicts could arise. A SFRC "joint-free" slab totally eliminates the need for any sawn induced contraction joints, thus eliminating all of these potential problems. Adopting a SFRC system will not only minimise these problems but also improve the flexibility of the building in terms of "future-proofing" it. Many clients in Europe specify "joint-free" floors in all of their facilities (ground bearing and pile supported) for just such a reason. 6.0 CONCLUSION e quality and durability of a modern industrial floor slab is key to the success and efficiency of a modern logistics facility. Technical Report No 34 section 2.1 1 says that "an ideal floor would be perfectly flat and level and have no joints". is is more achievable with SFRC than with lightly reinforced floor slabs as it allows the elimination of saw-cut joints, and therefore ensures better long term flatness. However, joint-less SFRC slabs are not suitable for every type of building, but they are ideal for distribution warehouse and factories that have intense forklift traffic or require high impact and abrasion resistance. If the building owners, consulting engineers, architects and general contractors have decided to opt for a "joint-free" SFRC slab, they must take precautions in choosing the right concrete contractor for the job by carefully reviewing the following items: • the contractor s track record in joint-less SFRC floors • visit "joint-free" reference floors and ask the opinion of their users • check the site quality control procedures proposed by the concrete contractor • ensure that adequate site conditions will be in place before, during and after the works • ensure early co-ordination takes place with the contractor to optimise the detailed design and particularly adjoining interfaces • limit the number of split responsibilities within the contract • be aware of and accept the possibilities of controlled cracks. Building owners are increasingly aware of the problems of saw-cut joints; therefore "joint-free" industrial flooring systems including SFRC are becoming more frequently specified and have proven to be a successful solution. Due to advances in equipment, material technology and design methodology, designers, clients and contractors are now able to consider more than just the traditional options when deciding upon a specification for any one scheme. Of equal importance to the design methodology are the skills and experience of the practitioners involved in the design and construction of the scheme, as often the limiting factor in terms of quality are those imposed by the supervisors and workers themselves. If these factors are carefully considered, if the planning and design process is integrated carefully with the building and the logistics systems and if the correct contractor and supply chain is selected, then the end result will be that everyone gets exactly what is best for the project. 7.0 ACKNOWLEDGEMENT e authors would like to acknowledge the assistance received from omas Beco of Twintec International and Ruth Waugh of Twintec Australia. REFERENCES 1. UK Concrete Society Technical Report No 34. Concrete Industrial Ground Floors -- A Guide to design and construction. Section 2.1 2. ACIFC Steel Fibre reinforced Concrete Industrial Ground Floors - An Introductory Guide (ACIFC 1999). 3. UK Concrete Society Technical Report No 63. Guidance for the design of steel-fibre-reinforced concrete. Section 9.1 4. ASTM C1550-05, Standard Test Method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panel), 2005. 5. I. LÖFGREN, Chalmers University Of Technology, Gothenburg, Sweden, Fibre-reinforced Concrete for Industrial Construction -- a fracture mechanics approach to material testing and structural analysis, 2005, p.52 6. British Standards Institution, BS EN 14845. Test methods for fibres in concrete, Part 1: Reference concretes, Part 2: Effect on strength, BSI, London, 2006. 7. British Standards Institution, BS EN 14651. Test method for metallic fibered concrete -- measuring the flexural tensile strength (limit of proportionality (LOP), residual), BSI, London, 2005. 8. ASTM C1018-97, Standard Test Method for Flexural toughness and first-crack strength fiber-reinforced concrete (using beam with third-point loading), 1997.