Sustainability 1

The Definition of Sustainability

What is Sustainability?

What Does Sustainable Mean?

The terms Sustainable and Sustainability are used to describe many different approaches toward improving our way of life.

Three pillars of sustainability

Sustainable Agriculture

SUSTAINABILITY – RC DESIGN

Concrete is a versatile building material that can provide many sustainablebenefits by virtue of its economic, thermal mass, durability, fire resistance,acoustic performance, adaptability and recyclability. Thus, the design of r.c must ensure these benefits are utilised to deliver the most sustainable outcome.

SocialStructural integrity aspect

SOCIALSTRUCTURAL INTEGRITY

The collapse of a bridge over the Mississippi river -2/8/2007

a design flaw - the likely cause of the collapse - additional weight on the bridge

Without structural integrity…………….

Originally, the building was designed to be an office block of 4 storey, but due to economic boom in 1980’s and it was changed to become an open-plan department store of 5 storey. The addition of a fifth floor to the structure and the dragging of air conditioners along the roof overloaded the structure.

29/7/1995-Sampoong department store collapse –killing over 500 peoples and injured 937 people

Traffic, machinery, HVAC systems, elevators, weather, and natural frequencies, leads to vibration .

The additional cost to for relatively high mass of concrete floors to meet vibration criteria is small compared to lightweight construction.

SOCIALVIBRATION

Social Weather protection aspect

For a building with external reinforced vertical elements exposed to rain, XC is selected (exposure class XC3/4 to BS 8500) with an intended working life of at least 50 years, a range of designed concretes are appropriate depending on the minimum cover to the reinforcement.

The selection of appropriate concrete cover and concrete density yield high quality concrete, and can contribute to a durable weather-proof building envelope. Thus design considers the environmental conditions the concrete will be exposed to. The five main exposure classes defined in BS 8500 are listed below

SOCIALWEATHER PROTECTION

SOCIALFIRE RESISTANCE ASPECT

Note: Concrete does not burn and does not emit any toxic fumes when subjected to fire - 'fireproof'. Concrete structures generally do not require fire protection if appropriately designed, because of their inherent fire resistance. This removes the time, cost, additional materials and labour required to provide separate fire protection measures.

The fire resistance requirements are specified in EC2/MS EN. It is regulated using the thickness of elements. Eg. A 120-mm-thick concrete slab can provide two hours fire resistance . Thicker slabs provide greater resistance. Similarly, concrete beams and columns can also be designed to adequately comply with fire-resistance requirements specified in EC2, without requiring specialised fire protective measures.

SOCIALFIRE RESISTANCE

SOCIALACOUSTIC PERFORMANCE

Good sound insulation and acoustic performance of homes and offices, has now grown in importance. Eg. The appropriate thickness of floor provide good airbond or impact sound insulation eg. 180 mm-thick..

LIVING ROOM, BED ROOM -30 TO 40 DBA. OFFICE & MEETGdBA ROOM – 30 TO 40dBA .

SOCIALACOUSTIC PERFORMANCE

(1) wall insulation. (2) nsulation under floors. (3) partition insulation. (4) roof insulation. (5) ceiling insulation.

EnvironmentDesign building with less embodied CO2 emission (ECO2) concrete grade

ECO2 is the carbon emissions associated with the production and manufacture of a product (cradle to gate)-tend to trap heat in our atmosphere.

According to BS8500, gred concrete for a building with external reinforced vertical elements exposed to rain (exposure class XC3/4 to BS 8500) with an intended working life of at least 50 years design life can be found below

With minimum cement content and the use of water reducing or high range water reducing admixtures., a reduction in concrete strength class will typically offer immediate savings in terms of ECO2 (reduced cement/combination content)

ENVIRONMENTDESIGN BUILDING WITH LESS EMBODIED CO2 EMISSION (ECO2) CONCRETE GRADE

Further, MPA assists designers in optimising the sustainable credentials of concrete through specification. This guide focuses on concrete, its constituent materials including admixtures and how the variation of the specification can influence the sustainability performance of the concrete. Sustainable credentials with greatest scope for influence through specification include: the performance of fresh and hardened concrete (e.g. strength gain, durability); embodied CO2 (ECO2); CO2 associated with transportation; responsible sourcing or otherwise; and use of recycled materials

Title: Specifying Sustainable Concrete ISBN:978-1-908257-01-7Published: 2011 Publisher: MPA - The Concrete Centre Price: FREE

http://www.concretecentre.com/online_services/publication_library/publication_details.aspx?PublicationId=758


Aggregates are the major component of concrete by volume and are inherently a low carbon product. Most are naturally occurring materials requiring little processing and are usually locally sourced, with the associated benefit of low transport CO2 emissions.

Aggregate size can have a significant impact on the cement content of concrete; larger aggregate sizes generally requiring lower cement contents.

BS 8500-2: 2006 limits mix design requirements for designated concretes. Each designation class is assigned minimum cement contents (kg/m3) for different maximum aggregate sizes. For an RC32/40 designation, for example, the minimum cement content for concrete with maximum aggregate sizes of 10mm and 20mm is 340 and 300kg/m3 respectively. Where possible, therefore, reduced ECO2 levels will be achievable by specifying increasing maximum aggregate sizes.


Aggregate – avoid size 10mm

Recycle aggregate and recycle concrete aggregate

In addition to natural aggregates, suitable materials for use in concrete include recycled aggregate (RA), recycled concrete aggregate (RCA), blast furnace and zinc slag, foundry sand, slate aggregate and china clay sand or stent.


Permit the use of recycled or secondary aggregates but do not over specify. Recycled aggregates should only be specified when they are locally available, otherwise transportation impacts exceed benefits. When specifying recycled and secondary aggregates, the factors to balance are resource depletion, transportation CO2 impacts and implications on mix design. These are all impacted by availability, and concrete producers are well placed to ensure the most sustainable aggregates for each project are used.


Woopa building in Vaulx-en-Velin, nearby Lyon, France (2011) . An office complex with a shopping centre, a car park and 92 social housing apartments . A CO2-neutral and energy positive design with sustainable use of materials, such as walls of recycled reinforced concrete and recycle glass .

optimum lighting and heat from the sun allows the residents to enjoy unimpeded views.


Cementitious additions - recommended

Specify that concrete should always contain cementitious additions as it can reduce the embodied CO2 (ECO2) of concrete and influence its visual appearance. When aesthetics are critical, specify the cement/combination to ensure colour consistency

The cementitious component of concrete represents the majority of the embodied CO2 (ECO2) of concrete (96%)


Admixtures

Admixtures can be used to enhance sustainability credentials and reduce the ECO2 of concrete, as well as modifying its physical properties.

Admixtures are defined in EN 934-2 [12] as ‘material added during the mixing process of concrete in a quantity not more than 5% by mass of the cement content of the concrete, to modify the properties of the mix in the fresh and /or hardened state’. In the hardened state admixtures can significantly improve the durability of the concrete to a range of aggressive environments, extending the maintenance free service life.


Although the higher strength class increases in ECO2 but this would have to be offset against a more slender, high strength structural solution offering potential economic, environmental and social benefits to the design team, contractor and client alike.

The design using of high-strength concrete lead to reduction in column size and result in increase of the net lettable area of a building.

Eg. a typical concrete column scenario (applied load of 24000kN and moment of 500kNm), the higher strength class would afford element size reductions of around 30% (from around 900 x 900mm to750 x 750mm) and corresponding reinforcement content reductions of about a third. In addition, there may be potential reductions in foundation size.

ECONOMICINCREASE LETTABLE AREA

EXAMPLE 1 : Footing. Footings typically represent 3% of a building’s cost. For the heaviest reinforced concrete solutions, the footings will be more expensive, but, in relative terms, this represents only a small cost. The use of post-tensioned slabs, which are typically 15% lighter than other forms of construction, can minimise this cost.

ECONOMICMINIMISE THE COST

ECONOMICMINIMISE THE COSTEXAMPLE 2Floor system. The current trend in commercial buildings for open plan floors and minimum columns makes long-span floors attractive. Using Post-tensioned band beams with one-way flat slabs provide the most economical long-span floor systems.

post-tensioning to the car Park flat slabs.

Sustainability 1

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