Fire Performance
Questions and Answers
Question: What determines fire endurance of blocks?
Answer: There are two major items that fire endurance
is dependant on: The type of Aggregate used and the equavalent thickness
of the block.
Question: There are different types of concrete and/or aggregates so how do I tell?
Answer: Yes, there are four types of concrete: Type N which has
limestone or calcareous gravel as aggregate, Type S which has granite,
quartz or siliceous gravel as aggregate, Type L (1) 20S that has shale
as course aggregate and Type L (2) 20S that has Slag as coarse
aggregate.
Question: What type does Day & Campbell use?
Answer: We use Type N for concrete and L (2) 20S on our lightweight block.
Question: Why L (2) 20S ?
Answer: Because it has much better fire rating and
being the steel capital of Canada slag is readily available unlike many
other manufacturers’ who don’t have immediate access to this product of
steel.
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Performance Properties
Introduction
Fire ratings for metric concrete masonry units are interpreted for
Supplement No. 2 to the National Building Code of Canada, titled “Fire
Performance Ratings - 1977″. The ratings given in Supplement No. 2 are
based on those that would be obtained from standard laboratory methods
of test, which are essentially a means of comparing the fire performance
of one building component with another.
The fire endurance of concrete masonry is dependent on the type of aggregate of which the unit is composed and the equivalent thickness of the unit.
Equivalent Thickness
The actual thickness of a solid unit or the equivalent solid thickness
of a hollow unit determines its fire endurance. The equivalent thickness
of a hollow unit is equal to the actual overall thickness of the unit
multiplied by the net volume and divided by the gross volume. For
example, a 190 mm wide unit that is 50% solid would have an equivalent
thickness of 95 mm.
Types of Concrete
Types of concrete available in Ontario have been considered in Table 5.1.
Type N concrete. The coarse aggregate is limestone, calcareous gravel, or similar dense material.
Type S concrete. The coarse aggregate is granite, quartzite, siliceous gravel or similar dense material.
Type L (2) 20S concrete. The coarse aggregate is expanded slag, and the
fine aggregate is sand and lightweight aggregate in which the sand does
not exceed 20% of the total volume of all the aggregates in the
concrete.
It should be noted that lightweight units exhibit better fire
performance and therefore a higher rating is assigned for he same
equivalent thickness of normal weight block.
Fire Endurance Ratings
Table 5.1 lists the fire endurance ratings of standard hollow, 75%
solid, and 100% solid metric concrete masonry units in three different
aggregate types. The information provided is representative of minimum
standards of units manufactured by the various Ontario producers and is
provided in this section as a guideline for the designers, to be used in
conjunction with Supplement No.2
Table 5.1
Fire Endurance Ratings in Hours of Concrete Masonry Units
STANDARD (HOLLOW)
|
SIZE |
EQUIVALENT |
TYPE S or N |
L(2) 20S |
|
cm |
mm |
HOURS |
|
|
10 |
66 |
0.8 |
1.1 |
|
15 |
81 |
1.1 |
1.5 |
|
20 |
106 |
1.8 |
2.5 |
|
25 |
127 |
2.4 |
3.5 |
|
30 |
148 |
3.2 |
4 + |
75% SOLID STANDARD
|
SIZE |
EQUIVALENT |
TYPE S or N |
L(2) 20S |
|
cm |
mm |
HOURS |
|
|
10 |
74 |
1.1 |
1.3 |
|
15 |
112 |
2.0 |
2.8 |
|
20 |
148 |
3.2 |
4 + |
|
25 |
187 |
4 + |
4 + |
|
30 |
227 |
4 + |
4 + |
100% SOLID
|
SIZE |
EQUIVALENT |
TYPE S or N |
L(2) 20S |
|
cm |
mm |
HOURS |
|
|
10 |
90 |
1.4 |
1.8 |
|
15 |
140 |
2.9 |
4 + |
|
20 |
190 |
4 + |
4 + |
|
25 |
240 |
4 + |
4 + |
|
30 |
290 |
4 + |
4 + |
Contribution of Plaster and Wallboard Finish
Improved fire endurance may be achieved in concrete masonry walls by the use of plaster or gypsum or wallboard, applied directly to the masonry wall. Reference should be made to Subsection 1.6 No 2 for pertinent details.
For requirements not covered in this section consult a local producer.
Fire Resistance Protection for Steel Columns
The minimum equivalent thickness of concrete masonry protection for steel columns is given in Table 2.6A of Supplement No. 2. The minimum thicknesses for concrete masonry, taken from Table 2.6.A are as follows;
1.5 Hours 2 Hours 3 Hours 4 Hours
Type S Concrete 50 mm 64 mm 89 mm 115 mm
Type N or L Concrete 50 mm 50 mm 77 mm 102 mm
An additional requirement when using concrete masonry units as fire protection for steel columns is for joint reinforcement of at least 5.20 mm wire to be laid in every second coarse. The space between the masonry protection and the steel column need not be filled.
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