Home  »  Fire Performance

Fire Performance

• Questions and Answers
• Performance Properties

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.

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

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.