220 likes | 361 Vues
Sustainability & Slag Contractor’s Issues. James Trezona 4 th May 2007. Lend Lease and Sustainability.
E N D
Sustainability & Slag Contractor’s Issues James Trezona 4th May 2007
Lend Lease and Sustainability “ Profits are not the only yardstick by which to judge performance… The time is not far off when companies will have to justify their worth to society, as indeed increasingly major public and private investments have to do now, with greater emphasis being placed on environmental and social impact than straight economics.” Dick Dusseldorp, Chairman’s address 1973
Commercial Application of Sustainability GreenStar is the main tool: • Only widely accepted rating tool measuring materials • Clients understand it • Australia wide system Alternatives • LCA: not a commercial proposition at present • Simplified LCA tools: useful for decision making • Victorian EPA Retail Eco-footprint calculator
BLL and GreenStar BLL has built 5 GreenStar rated projects BLL has provided GreenStar Accredited Professional consulting services to a further 2 GreenStar rated projects BLL is currently working on 14 projects that will receive a GreenStar rating BLL has 28 GreenStar Accredited Professionals
BLL GreenStar Projects The Bond, Sydney • First building in Australia to be certified 5 star GreenStar As-Built • First office building to sign a 5 star ABGR commitment agreement
BLL GreenStar Projects 500 Collins Street, Melbourne • 5 star GreenStar • Office Design
BLL GreenStar Projects Quad 4, Sydney • 4 stars GreenStar • Office Design
BLL GreenStar Projects Lend Lease Melbourne • Goal: 6 stars GreenStar • Chilled beams • Black-water recycling • Co-generation plant
BLL GreenStar Projects Investa (5 stars GreenStar) • Office Interiors Morgan Stanley (5 stars GreenStar)
GreenStar Score Card – Concrete Credit All GreenStar Rated Buildings: 17 rated buildings eligible for concrete credit 2 buildings awarded 3 points 4 buildings awarded 1 point Bovis Lend Lease GreenStar Buildings: 2 rated buildings eligible for concrete credit 0 points awarded
GreenStar Concrete Credit 1 Point: 20% of all aggregate used is recycled concrete aggregate 1 Point: 20% of cement used for in-situ concrete and 15% of cement used for pre-cast concrete is replaced with industrial waste product 2 Points: 40% of cement used for in-situ concrete and 30% of cement used for pre-cast concrete is replaced with industrial waste product
Basis of GreenStar Concrete Credits GOAL: Minimise CO2 emissions, embodied energy and resource use • METHOD: Rules of thumb: • Binder to have specified proportion of industrial waste product (SCM’s) • Recycled concrete aggregate • REASONING: More involved analysis (eg LCA) prohibitive • Time consuming analysis • Hard to benchmark: lack of research
Should Concrete be Part of GreenStar? Absolutely: • Next to water, concrete is the most used material in the world • World cement demand provides about 5% of all CO2 emissions • Australian cement demand equates to about 1% of Australian CO2 emissions • Portland Cement has the highest CO2 emissions of any building material. About 0.8 t of CO2 produced for every 1.0 t of cement. • Concrete represents a significant proportion of the mass, embodied energy and CO2 emissions of a building.
Reduce, Reuse, Recycle INCREASING BENEFIT
Post-Tensioning Dilemma • Most concrete framed buildings have floors that are post tensioned due to cost efficiencies of this form of construction. • Cost effective because even though labour intensive, reduces concrete by approx. 20% and steel by approx. 50%. • PT is an optimal solution for sustainability (REDUCE) • Floors make up about two thirds of a building’s total concrete (concrete frame). • PT requires concrete with a high early strength • Limits the opportunity to use SCM’s and hence gain GreenStar credits.
Concrete Mix Specification Current best practice advocated by the Concrete Industry • Non-prescriptive specification • GreenStar is a prescriptive specification • Not met with enthusiasm by Concrete Industry • Reduces potential for innovation Implication is that concrete mix design is more sophisticated than structural engineers or GBC are giving it credit for.
Embodied Energy and CO2-e Does specifying a percentage of Portland cement replacement with SCM’s produce a mix with the lowest embodied energy or CO2-e? • This is a ratio of cementitious material • Provides scope for artificial manipulation of mix to satisfy the GreenStar specification
Prescriptive Specification of CO2-e or Embodied Energy Should credit instead control the absolute value of either: • Embodied energy • CO2-e Requires research to establish benchmarks
Recycled Aggregate – Problems and Limitations • RCA has quality control issues • RCA difficult to establish reliable supply • RCA use may affect concrete durability • RCA use increases concrete shrinkage • RCA use may affect workability • RCA use may require higher cement contents – defeats objectives of reduced environmental impact? • Why is slag aggregate excluded?
Recycled Aggregate – Waste or Resource? Is RCA really a waste product? • Globally, construction and demolition waste has the potential to provide only 5% of the total consumption of sand and rock • In the USA, if all C&D waste rubble was use for base-course applications, it could only supply 20% of total consumption • RCA can in some cases be a superior product for base-course than natural stone due to the presence of unhydrated cement • Why does GreenStar promote RCA in concrete for engineered structures when it can be fully utilized in applications where there are not detrimental side effects or compromises?
Conclusion • Can we use GreenStar to REDUCE first and RECYCLE second? • If RCA is to be recognized in GreenStar, Slag Aggregates should be too • Can embodied energy and CO2-e be directly measured or specified rather than indirectly specified through a prescriptive specification of Portland cement replacement • Further research required to allow benchmarking • Recycled content should be encouraged only if it diverts material away from being a waste product, rather than diverting it from more appropriate alternative uses where it is already recognized as a resource • In design consider REUSE: long life, adaptive reuse, durability
Conclusion • GreenStar will likely continue to be the main vehicle for commercial application of Sustainability in buildings in the short to medium term • The treatment of concrete and steel in GreenStar is quite basic compared with the treatment of energy and water • To improve the practical application of Sustainability the construction industry should seek to improve GreenStar • More interaction required between Concrete Industry and GBC • Close liaison required between builder and sub-contractors or material suppliers required to achieve sustainability in practice. New ways of doing business.