AIRCRETE

3.1

Chapter 3. Properties

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3.5.2

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Properties given in this chapter are for Aircrete as a material unless stated to be for a block or for blockwork.

3.1 Acoustic
The combination of the internal structure and the stiffness characteristics of Aircrete enable sound reduction performance for walls and partitions superior to the results predicted by the general Mass Law curve for masonry.

The Mass Law curve for Aircrete is:
Sound Reduction Index R= 22.9 log (m) – 4.2 dB
(average for the range 100-3150Hz)
Where m = superficial mass in kilograms per square metre

3.1.1 Sound absorption
Sound absorption is a property relevant to particular applications. When it is exposed, the aerated internal structure of Aircrete provides good sound absorption properties. However, painting reduces the sound absorption.
Specialist finishes, which are outside the scope of this code, provide superior sound absorption.

3.2 Air permeability
Air permeability of Aircrete is approximately 0.12m

measured at 50 pascals.

The corresponding value is 1.04m

1 m

for Aircrete blockwork in general purpose mortar.

3.3 Chemical
Alkalinity is between pH 9 and 10.5.

3.4 Density
Densities are in the range of 400 to 900kg/m

.

3.5 Durability

3.5.1 Chemical
The resistance to attack from sulfates likely to be found in soils and ground water is high. The degree of resistance is dependant on the strength and density.

3.5.2 Frost
The resistance to frost is superior to that of many stronger denser masonry materials although the degree of resistance is to some extent dependant on
strength and density. The high freeze thaw resistance is due to the aerated internal structure of the material.

3.6 Environmental
The inherent insulation properties of Aircrete reduce the emission of CO2 from the building compared with other heavier structural materials. The conservation of fuel
and power requirements of building regulations can be met or exceeded with either no or minimum addition of non-structural insulation materials to the Aircrete fabric of the building.

Process off cuts and recycled materials are used in the manufacture of Aircrete so that manufacturing waste is eliminated or minimised.

3.7 Embodied energy
Embodied energy in Aircrete is relatively low and the environmental impact is low.
Details of a range of environmental impact ratings for Aircrete are included in the BRE "UK Database of Environmental Profiles of Construction Materials and
Components" available at www.bre.co.uk/envprofiles. Aircrete achieves ‘A’ status (where ‘A’ is low and ‘Z’ is high) as part of the EcoHomes rating and contributes a
number of credits towards the overall environmental rating for homes.

Similarly Aircrete achieves a high performance rating in the Construction Products Industry Key Performance Indicator for: Environmental - use of recycled material -
based on the percentage of the total material which is secondary/recycled.

3.8 Fire
Combustibility and surface spread of flame
Aircrete is non-combustible and has Class O surface spread of flame.

3.9 Movement
Aircrete is subject to thermal and moisture movements.
Coefficient of linear expansion is 8x10

/K.
Drying shrinkage is less than 0.09% (when measured in accordance with BS 6073).

3.10 Sizes
Aircrete blocks are produced in a range of thickness from 60mm to 355mm with a range of face dimensions. The most common work face dimensions are 440 or
610/620mm long by 215mm high. Other work face dimensions are also available ranging from coursing bricks 215mm long by 65mm high to large format blocks 620mm long by 440mm high. Some sizes are available with tongue and groove perpend joints, with and without hand holds, in the perpends.

Dimensional tolerances
(measured in accordance with BS 6073)

For use with general purpose mortars:

Length and height: + 3mm - 5mm
Thickness: ± 2mm average, ± 4mm any point

For use with thin layer mortars:
(Measured in accordance with EN771-4 for "Thin layer mortar A" classification)

Length: ± 3mm
Thickness: ± 2mm
Height: ± 2mm