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Concrete

Generally Accepted Process

Concrete has by far the highest embodied energy of any other building material – more than twice that of masonry. It also has far and away the lowest value when it comes to recycling at the end of its life. However, concrete has substantial thermal and structural benefits which can sometimes make it the only practical choice.  The decision to use concrete must be made with due respect to the issues involved. Careful and informed design decisions must be employed to minimise its use to building elements which maximise its strengths and cannot be substituted with alternative materials.

It is possible to make improved environmental choices with each ingredient in concrete – cement, sand, aggregate, water and steel reinforcement.

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Choices For Bull Street

Concrete has been chosen for the ground floor of the Bull Street Terraces for its strength as a footing system and its thermal mass quality as part of the passive solar design system. Consideration has been given to its placement and structural design to minimise the quantities needed. A bored pier design reduced the original beam size by over 50%.

Crosby Architects are working with industry to utilise exciting new developments in carbon negative cement, which absorbs more carbon than it produces. We will update as this progresses.

Damp Proof Course

Termite control: Kordon Termite Barrier will be applied to any slab penetrations before slab pour & to perimeter of slab after pour.

National Polystyrene Systems 50mm SL grade Expanded Polystyrene to slab edge perimeter to continue full depth of external edge. (Manufacturer & supplier: NPS Sunshine – Paul 03 8326 8080. N.B. Seconds may be available)

A separating film to be placed between the polystyrene and the cement to make future recycling possible.

Reinforcement to be supplied by One Steel Metal Land, Bendigo (Rob 03 5442 2288). One Steel have their own steel recycling plants and about 70% of their reinforcing steel is recycled content. Most other companies have to buy their coil in from overseas.

Cement can be replaced with 20 – 70% fly ash/slag component, depending on the ambient temperature. Fly ash is a group of materials that can vary significantly in composition. It is residue left from burning coal, which is collected on an electrostatic precipitator or in a baghouse. It mixes with flue gases that result when powdered coal is used to produce electric power. The use of fly ash can result in better workability, pumpability, cohesiveness, finish, ultimate strength, and durability. The fine particles in fly ash help to reduce bleeding and segregation and improve pumpability and finishing, especially in lean mixes. (ref: NPCA)

Sand. Naturally occurring washed sand is a non-renewable resource. Manufactured sand is a quarry dust by-product of the crushing of rock.

Aggregate can be replaced with recycled crushed screened concrete, half 20mm, half 14mm, if available and considered to be of good quality.

Water. To be recycled (as standard practice).

‘Carbometum’ is an interesting admix which claims to improve the bio-energetic properties of mineral building materials (concrete).

Any remaining Carbon Footprint to be offset by purchasing Carbon Credits.