Fire Safety and Concrete Structures - Febelcem

Resistance to fire applies to structural elements. It is a measure
of their ability to perform the role assigned them despite the
action of a fire.
These two notions are therefore completely different. The first
concerns the birth and development of the fire, while the second
occurs in the full intensity phase. Neither area can be neglected
in fire prevention. The instructions therefore include
requirements relating to both aspects.
Thus, wood [5] is a material that does not react well to fire –
wood burns – while wooden beams and columns are structural
elements with a significant resistance to fire.
Conversely, steel is a material with a good reaction to fire, while
steel elements are structural elements with a very poor
resistance to fire.
Finally, concrete combines the two qualities. This is why it is
“the” preferred material for structural elements where good fire
behaviour is sought.
Because they are more permanent, the choices that improve the
fire resistance of structural elements offer greater safety for
preventing fires. Each modification (renovation, enlargement) is
subject to a new building permit or a revision of the operating
licence where the fire services are consulted.
The same is not true of finishes, especially in residential
buildings, where the owner/tenant of the property can alter the
content of the building and the nature of the claddings to such
an extent that the load and risk of fire are fundamentally
changed.
2.4.1. The reaction to fire of construction
products - Classification
With regard to the reaction to fire mentioned in CE marks, every
construction professional owes it to himself to get to grips with a
minimum of European language to understand the new tests
and classification standards.
This system of classification [40] was the subject of decisions by
the European Commission on 08‐02‐2000 [61], [63] and
26‐08‐2003. As the decrees implementing this marking appear,
manufacturers have to check that their products comply with the
new European requirements and if necessary modify these
products.
The number of classes, the logic which enabled their
construction and some of the tests used differ from current
Belgian practice, so much so that there is no correspondence
between current Belgian classification and the system of
Euroclasses.
Construction products are separated into two main families [12]:
that of floor coverings and that of other products. This
distinction is explained by the fact that the scenarios of exposure
to fire and the behaviour of the materials differ in both cases. In
each of these groups, the Euroclasses, which number seven,
defined in NBN EN 13501‐1:2002 [105], are as follows:
−
−
A1 Fl
, A2 Fl
, B Fl
, C Fl
, D Fl
, E Fl
, and F Fl
for floor coverings (Fl
for “floor” )
A1, A2, B, C, D, E, and F for other construction products.
Classes A1 and A2 (or A1 Fl
, A2 Fl
) are assigned to products with a
low or very low organic fraction which are therefore hardly or
not very combustible.
Classes B to E (or B Fl
, E Fl
) are assigned to combustible products
which contribute significantly to fire development, for both floor
coverings and other products. Class E applies to products that
meet the minimum German marketing criterion and class F
applies to unclassified products or those that have failed the
least severe test.
Alongside the reaction itself, some construction products are
given two additional qualifications:
−
−
s1, s2 or s3 for the production of smoke (s = ’smoke’: the
higher the number, the more smoke is emitted):
• s3: no limit for smoke emission;
• s2: the total emission of smoke and the speed of
emission are limited;
• s1: stricter requirements than for s2.
d0, d1 or d2 for behaviour faced with falling droplets and
burning particles: (d = ’drop’: the higher the number, the
more drops are produced):
• d2: no limit;
• d1: production of droplets / incandescent particles
over a specific period;
• d0: no production of droplets / incandescent
particles
The table [51] below allows reaction to fire classes to be
transposed between the old French classification and the new
European classification (EN 13501‐1):
Classes to NF EN 13501‐1 new
classification
Requirement of old
classification
A1 ‐ ‐ Incombustible
A2 s1 d0 M0
A2 s1 d1
s2 d0
A2
s3 d1
M1
s1 d0
B s2 d1
s3
s1 d0
C s2 d1
M2
s3
s1 d0 M3
D s2 d1
s3
M4 (non‐dripping)
All classes other than E‐d2 and
F
M4
In 1996, the European Commission published a regulatory list of
construction materials [34], [61] which may be grouped together
18