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8 concrete Recycled Crushed Concrete for New Christchurch Southern Motorway A New Zealand Transport Agency (NZTA) decision to use recycled crushed concrete in the construction of the new Southern Motorway is designed to have a wide range of positive environmental benefits. Work on the $180 million Christchurch Southern Motorway project is scheduled to begin in March 2010. The project will be one of the most significant roading projects to be undertaken in the greater Christchurch area over the last 5-years. A key component of the project will be the use of recycled crushed concrete as aggregate. NZTA State Highways Manager for Canterbury-West Coast Region, Colin Knaggs, says there are real pressures on construction aggregate sources within greater Christchurch, with reports suggesting that there is only around 10 years supply remaining. In developing the Christchurch Southern Motorway project the NZTA looked at more sustainable supply alternatives, rather than being totally dependent on importing aggregate from traditional sources such as riverbeds and quarries. Using Recycled Crushed Concrete (RCC) will cost approximately the same as obtaining the same quantity of virgin aggregate from usual sources. Furthermore, as much of the concrete will be sourced from several significant demolition projects planned for Christchurch in the next few years, the reuse of concrete that would have otherwise been disposed of in local landfills makes real environmental sense. In 2007 the NZTA was granted consents to stockpile CO2 Footprint of RCC for New Christchurch Southern Motorway As part of the preliminary planning stages for the new Christchurch Southern Motorway project, the New Zealand Transport Agency (NZTA), then Land Transport New Zealand, commissioned Opus International Consultants to determine the carbon footprint of different methods of obtaining 60,000m³ of AP65 subbase for use in construction. The cases modeled by John Patrick, Opus International Consultants’ Research Manager (Pavements), were aggregate from the Waimakariri riverbed to placement, and the use of Recycled Crushed Concrete (RCC) to stockpile, and then placement. The research demonstrated that when the energy consumed in transporting riverbed aggregate from source (50 km round trip) and processing it using electricity, is measured against the energy consumed in transporting in RCC from source (15 km round trip) and processing it using diesel, the CO2 emissions per tonne of material were essentailly comparable. However, when the CO2 uptake of crushed concrete (4% of the mass of concrete) was considered along with the emissions associated with transporting the demolition concrete to waste, then the use of RCC offered significant advantages over riverbed aggregate. Recycled Crushed Concrete at Christchurch stockpile 60,000 m3 of RCC at locations near the site of the new Southern Motorway. Site preparation works for the storage site have been completed, and RCC material is being stockpiled as it becomes available from demolition sites around Christchurch. Mr Knaggs says that locating these stockpiles near the new Southern Motorway construction area will mean less heavy vehicle noise, exhaust emissions and traffic congestion that would inevitably result from the transportation of aggregate from traditional sources further afield. Recycling Concrete Pavements - American Concrete Pavement Association (ACPA) This comprehensive guide addresses facts about recycling concrete for use in new concrete pavement structures. It describes concrete pavement recycling as a proven technology that offers an alternative aggregate resource that is both economic and sustainable. Concrete recycling is a relatively simple process that involves breaking, removing and crushing hardened concrete from an acceptable source to produce recycled concrete aggregate, a granular material that can be produced for any application for which virgin aggregate might be used. To borrow this item email library@cca.org.nz
FRC – Not All Fibres Are the Same As a result of developments in fibres and Fibre Reinforced Concrete (FRC) <strong>CCANZ</strong> Information Bulletin IB 39 Fibre Concrete is currently being revised. By outlining the different fibre types and different fibre reinforced concretes commonly available in New Zealand, this summary article seeks to address various points of confusion about FRC technology and design. What is the purpose of using fibres in concrete? Unreinforced concrete has excellent compressive strength but is a brittle material that deforms elastically under tension until it cracks. At this point it rapidly loses its load carrying capacity, i.e. it does not have any post-crack ductility. Steel reinforcement bars or mesh usually provides this ductility, but it can also be provided by fibres. The basic concept of FRC is that fibres arrest the growth of micro cracking and/ or provide post-crack ductility in concrete. Steel and macro synthetic fibre reinforcement, like conventional reinforcement, only become effective after the concrete has cracked. It is how and at what stage this cracking is controlled that differentiates fibre types. Micro and cellulous fibres help in preventing plastic shrinkage cracking. Fibres range in type based on their base material (e.g. steel, synthetic, or cellulose), their size, and their shape. Steel and macro synthetic fibres enhance the toughness, ductility, and energy absorption capacity of hardened concrete. However, in the case of macro synthetic fibres, these properties may only be realised at crack widths approaching or exceeding those recommended at the serviceability limit state, and long-term performance should be considered1 , 2 . Both fibre types can be used to contribute to the load bearing capacity of a concrete member3 , 4 . They do not contribute significantly to reducing or eliminating plastic shrinkage cracking. At normal dosages they do not affect the flexural strength of concrete, but they do control drying shrinkage cracking. Micro synthetic fibres and cellulose fibres at appropriate dosages are particularly useful at limiting the widths of micro cracking in concrete in its plastic state. These fibres also lower the permeability of concrete and improve its impact and abrasion resistance. Micro synthetic fibres in concrete are used to improve fire performance because they melt at about 150-160°C leaving voids for the passage of moisture vapour that would otherwise lead to explosive spalling. Generally, these products provide no level of capacity / crack control if the concrete cracks in its hardened state. NRMCA publication CIP 24 cautions against the use of micro synthetic fibres for the control of cracking as a result of external forces, replacing any moment-resisting or structural steel reinforcement, decreasing the thickness of slabs on grade, or increasing ACI or PCA control joint guidelines5 . Blends of steel or macro synthetic fibres and micro or cellulose fibres can be used to provide a combination of benefits to plastic and hardened concrete. When considering FRC it is important to note: No two fibres are the same, and a fibre should be selected for a particular application and designs based on the properties of the FRC pertaining to the selected fibre. The effects of fibres on the concretes that they reinforce depend on a number of factors – the fibre type, its dimensions, its properties, the dosage of fibres used in the concrete, and the properties of the matrix the fibres are contained in. Empirical design guides e.g. CSTR 636 , ACI 544.4R7 and NZS 31018 have been developed and published for steel reinforced concrete. However, these guides may not necessarily be suitable for macro synthetic fibres in consideration of their different longterm performance. concrete The unloading tunnel and rail track support slab at Fonterra’s Te Rapa storehouse made extensive use of steel fibre technology. Test reports or certification, from reputable independent testing authorities, should either be provided or the FRC should be tested to verify that it satisfies the properties required of it, e.g. the ultimate and serviceability states of NZS 3101 Concrete Structures Standard. It is imperative to recognise that a FRC designed and tested with a particular type and brand of fibre cannot be assumed to have the same properties as a FRC made from different fibres. This includes fibres that may look the same but come from different manufacturers or suppliers. The revised IB 39 Fibre Concrete will be available via the <strong>CCANZ</strong> website shortly. 1 Concrete Society, Technical Report 34 Concrete industrial ground fl oors – a guide to their design and construction, 3rd edition, The Concrete Society, Camberley. 2003. 2 Concrete Society, Technical Report 65 Guidance on the use of macro-synthetic fi bre reinforced concrete, Concrete Society, Camberley. 2007. 3 British Standards Institution, BS EN 14889-1:2006, Fibres for concrete. Steel fi bres. Defi nitions, specifi cations and conformity, British Standards Institution, London, UK. 4 British Standards Institution, BS EN 14889-2: 2006, Fibres for concrete. Polymer fi bres. Defi nitions, specifi cations and conformity, British Standards Institution, London, UK. 5 NRMCA, Concrete in Practice: What, why &how, CIP 24 Synthetic fi bers for concrete, National Ready Mixed Concrete Association, silver spring, MD, USA. 6 Concrete Society, Technical Report 63 Guidance for the design of steel-fi bre reinforced concrete, Concrete Society, Camberley. 2007. 7 American Concrete Institute, ACI 544.4R-88 Design considerations for steel fi bre reinforced concrete (Reapproved 1999), American Concrete Institute, Farmington Hills, MI, USA. 8 NZS 3101: 2006 Concrete structures standard. Standards New Zealand, Wellington. 9
Page 1 and 2: Volume 53 Issue No.3 September 2009
Page 3 and 4: CCANZ-PR03958 International concret
Page 5 and 6: concrete Standards New Zealand UPDA
Page 7: Standard tests exist for many such
Page 11 and 12: The visual appeal of the General Ac
Page 13 and 14: concrete NZ Permeable Pavement Stud
Page 15 and 16: INTERNATIONAL STORY concrete 15
Page 17 and 18: concrete Push Over - When Art Meets
Page 19 and 20: News from the Associations PRESSS D

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