Materiaux Final

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  • 8/8/2019 Materiaux Final



    Sustainable architecture is a general term that describes environmentally

    conscious design techniques in the field of architecture. Sustainable architecture is

    framed by the larger discussion ofsustainability and the pressing economic and

    political issues of our world. In the broad context, sustainable architecture seeks tominimize the negative environmental impact of buildings by enhancing efficiency

    and moderation in the use of materials, energy, and development space. Most

    simply, the idea of sustainability, or ecological design, is to ensure that our actions

    and decisions today do not inhibit the opportunities of future generations. This term

    can be used to describe an energy and ecologically conscious approach to the

    design of the built environment.

    Sustainable building materials


    The use of bricks in the Modern period stems from a revival of brick making in the late 13th early 14th centuries inresponse to a combination of a shortage of local stone and the influence of Europe where brick was used extensively.

    By the middle of the 16th century, brick making had become a distinct industry competing with stone as a structural


    As the industry grew, bricks became cheaper leading to its travelling downwards through the social spectrum. With

    the introduction of the railways in the 19th century, significant consignments of brick could for the first time be

    transported from the brickfields, such as those in Bedfordshire, to the conurbations of London, the Midlands and the

    industrial North where they were used to build terraces for housing a rapidly expanding working class.

    In the 20th century, mechanisation largely replaced making bricks by hand and this with other innovations helped fuel

    the building booms of the inter-war years and again in the 1960s and 70s following the rise in post war population.
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    Brick is a traditional building material. Heed is still paid to its almost unique quality of conveying a genius locii upon

    any building built from local clay. Brick construction itself continues to be regarded and taught as one of the

    fundamental construction types of contemporary building, and the industry itself continues to flourish.

    If the last few decades have brought opportunities through technological development, so too have they brought anew scrutiny in which fired clay bricks are examined against their environmental impact. Within the current debate

    concerning sustainable materials, brick is lined-up against a range of traditional and new materials. The brick industry

    will be hoping to match its strong credentials of durability with tradition against alternative forms of construction

    offering, particularly, reduced embodied energy.

    Types of brick

    Reclaimed bricks

    With an estimated 2.5bn bricks1 resulting from demolition each year, it is not surprising that there is a healthy market

    in reclaimed bricks. More of a surprise might be in the knowledge that only 5% of the 2.5bn are actually reclaimed

    50% are crushed and used in hardcore and fill.

    The Demolition Protocol states that bricks have a recovery potential of 10% - rising to 100% in some buildings.

    But what restricts the current recovery of usable bricks is complicated, though two factors are salient: the

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    The manufacturing process can be loosely divided into 4 stages.

    Extraction (or Clay Winning)Clay is removed from quarries and transported to the factory (though traditionally factories were usually adjacent to

    the quarries). Once it has reached the factory the clay is ground down using rollers into fine powder before being

    mixed with water.

    FormingBricks can be formed by one of two basic processes:

    Extrusion Clay is forced through an extruder and out through a die into a continuous brick-shaped column. The

    column is cut into single bricks ready for the dryers. Extruded bricks are generally perforated but cannot be frogged.

    Soft mud moulding Clay is thrown into a mould which has been pre-lined with a releasing agent such as sand, oil

    or water. The excess clay is removed from the top and the brick released from the mould. Prior to mechanisation, this

    was all undertaken by hand but the labour-intensive nature of the process and its consequential expense means

    that in modern time hand made bricks tend to be reserved for niche applications and specials.

    DryingTo prevent moisture from causing bricks to explode in the kilns, they are first dried before being fired. Drying takes

    place in conditions of between 80-120C, lasts for between 18 40 hours and can cause shrinkage of up to 10% on

    each dimension.

    FiringThe dried clay is fired to fuse clay particles and impurities (vitrification) to produce the hard brick in its completed

    form and livery. Bricks can be fired in either small batches in Intermittant kilns or the more energy efficient and

    larger capacity Continuous kilns. On completion of firing the bricks are selected and packaged a process that can

    be either manual or automated.

    Reusable if used with lime mortar

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    Downcyclable into low-grade fill / aggregate


    Large reserves

    Un-reclaimable if used with Portland cement mortar

    High embodied energy

    High output of CO2

    The firing of bricks can produce a bag of pollutants including fluorides, chlorides and oxides of nitrogen andsulphur. Strict limits are placed on emissions in the UK.

    Clay extraction has a long-term environmental impact on the landscape

    Transportation can add considerably to the embodied energy

    Thermal conductivity2

    - Density 1200 kgm3: 0.36 W/mK (Protected); 0.36 W/mK (Unprotected);

    - Density 1600 kgm3: 0.52 W/mK (Protected); 0.71 W/mK (Unprotected);

    - Density 2000 kgm3: 0.70 W/mK (Protected); 0.96 W/mK (Unprotected);

    Embodied energy

    - General bricks: 3 (+/-1) MJ / kg (3) or 2.67 MJ / kg (excluding transport to site) (7)

    - Facing bricks: 8.2 MJ / kg (very small sample size)(3)

    Calcium Silicate bricks

    Despite the method of using steam under pressure to cure sand and lime being patented in England in 1886, much of

    the subsequent development and eventual use of calcium silicate bricks has prospered more in Europe than the UK.

    Notable uses of the brick in London include Battersea Power Station and the RIBA building in Portland Place.

    Calcium silicate (sandlime or flintlime) bricks are made by mixing quicklime or hydrated lime with silica sand

    together with enough water to allow the mixture to be moulded. The mixture is left until the lime is completely

    hydrated when it is pressed into moulds and cured in a high-pressure autoclave for two to three hours. In this process

    the lime reacts with silica to form hydrated calcium silicates, producing a durable strong brick. The finished bricks are

    very accurate and uniform, although the sharp arrises need careful handling to avoid damage to brick.

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    Through use of less energy and without the air pollutants associated with firing clay, calcium silicate bricks are

    considered to render significantly less impact on the environment than clay bricks.

    Reusable if used with lime mortar

    Old bricks can be crushed and recycled into new bricks without loss of quality


    Large reserves

    Extraction of sand can cause landscape degradation

    Transportation can add considerably to the embodied energy

    Thermal conductivity2:

    - Density 1700 kgm3: 1.04 W/mK (Protected); 1.12 W/mK (Unprotected);

    - Density 2000 kgm3: 1.16 W/mK (Protected); 1.58 W/mK (Unprotected);

    - Density 2200 kgm3: 1.51 W/mK (Protected); 2.06 W/mK (Unprotected)

    Embodied energy3:

    8.2 MJ / kg

    Unfired Clay bricks (generally non-load bearing)

    Unfired clay is one of civilisations oldest form of building material with origins located as far back as 14000 BC

    around the Lower Nile.

    Following in the wake of the widespread use of unfired clay in, particularly, Germany, UK architects are increasingly

    attracted to the use of unfired clay in construction because of its perceived benefits to indoor air quality as well as its

    very low environmental impact.

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    Commercially available unfired clay bricks are commonly made of an extruded mixture of clay, sand and water with

    sawdust added as a binder, which is then air-dried.

    Reusable and recyclable

    Very low embodied energy

    Very low waste

    Large reserves

    No emissions during manufacture

    Can help to regulate humidity

    Generally non load-bearing

    Will degrade with prolonged exposure to water

    Transportation can add considerably to the embodied energy

    Can place restrictions on internal decoration



    Rammed Earth

    Rammed earth walls (aka pise) are constructed by the compacting (ramming) of moistened subsoil into place

    between temporary formwork panels. When dried, the result is a dense, hard monolithic wall.

    Rammed earth is an ancient form of construction, usually associated with arid areas. There remain plentiful

    examples of the