Fire Performance

Fire Ratings for concrete block are based on equivalent thickness as found in table d-2.11 formerly located in the supplement to the National Building Code of Canada.

MINIMUM FIRE RESISTANCE RATING OF DAY & CAMPBELL LTD. ARCHITECTURAL BLOCK.  
Results acquired through independent testing.

Fire Performance Properties

Introduction

Fire ratings for metric concrete masonry units are derived from the Supplementary Guidelines to the 1997 Ontario Building Code and the National Building Code of Canada. The ratings given in the Guidelines are based on those that would be obtained from standard laboratory testing; 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 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. 
Example:  A CMU that is 190mm wide and 50% solid would have and equivalent thickness of 95mm.

Types of Concrete - the types of concrete available in Ontario have been considered in the Table 5.1 (below)

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 – 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 aggregates.

Lightweight CMU’s exhibit better fire performance resulting in a higher resistance rating than that for a normal weight block with the same equivalent thickness.

Fire Endurance Ratings

Table 5.1 (below) lists the fire 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 sections as a guideline for the designers, to be used in conjunction with Supplement No. 2.

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