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thermalProperties.htm
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Masonry Thermal Properties
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The Annex D (informative) of prEN1996-1-2 (2003)
provides the thermal properties of thermal elongation, heat conductivity
and specific heat capacity and the density at elevated temperatures
for some types of masonry unit.
The most significant material property characterising
the fire performance of masonry is the density rather than the
type of brick, as the density is a measure of the porosity of
the brick which will govern the thermal properties of masonry
at elevated temperatures (Purkiss 1996).
Table 1 gives data on the density and coefficient
of linear thermal expansion of masonry units and mortar at ambient
temperature. Basically, the British Standard and Eurocode provide
close values for various masonry units, except calcium silicate
unit.
Table 1: Coefficient
of Thermal Expansion of Masonry Units and Mortar
|
Material
|
Density
(kg/m3)
|
Thermal expansion
coefficient (×10-6 per °C)
|
ENV
1996-1-1
|
BS5628-3
|
BRE-Digests
|
| Clay |
900-2400
|
4 to 8
|
4 to 8
|
5 to 8
|
| Calcium silicate |
1600-2000
|
7 to 11
|
11 to 15
|
5 to 12
|
Dense aggregate concret
Gravel aggregate
Crushed rock
Limestone
Lightweight aggregate
concrete
AAC |
400-2400 |
6 to 12 |
7 to 14 |
|
12 to 14
|
10 to 13
|
7 to 8
|
600-1000
|
8 to 12
|
8 to 12
|
8 to 12
|
400-750
|
7 to 9
|
8
|
| Mortar |
1500-1750
|
10-13
|
11 to 13
|
11 to 13
|
Figure
1 compares the variation of thermal strains for various
types of masonry unit at elevated temperatures included in
Annex D (informative) of prEN1996-1-2. The design data shows
that not all masonry units will expand under heating. The AAC
and lightweight aggregate concrete units shrink at elevated
temperatures.
Figures
2 to 5 show the variation of heat conductivity, specific
hear capacity and density with temperature for various types
of masonry units.
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