I have received test data from the manufacturer of the brick I selected for a new building. How do I read the test data? What is important and what isn't important?
There are several items that I would examine on the brick test data. In freeze/thaw environments the units should be Grade SW. A Grade SW brick must have an average maximum cold water absorption of 17% with a maximum individual value of 20%. The maximum average saturation coefficient is 0.78 with the maximum individual value of 0.80. Saturation coefficient is sometimes referred to as C/B because it represents the ratio of the cold water absorption divided by the absorption after 5 hours of boiling. In areas not normally subjected to freeze/thaw deterioration, Grade MW bricks can be used. The above values are increased for MW brick to an average maximum absorption of 22% and maximum individual value of 25% and an average maximum saturation coefficient of 0.88 and a maximum individual value of 0.90. The saturation coefficient can be waived if the average cold water absorption is less than 8% with at most one unit between 8% to 10%. The requirements for both water absorption and saturation coefficient can be waived if the units pass the freezing and thawing test described in ASTM C 67. Minimum compressive strength values also are set for durability. SW units must have a minimum average strength of 3000 psi with all units greater than 2500 psi. MW units must have a minimum average of 2500 psi with all units greater than 2200 psi. For most units sold in the United States, however, compressive strength is only important where masonry is used structurally. In these cases the compressive strength of the units must be greater than that required by the structural engineer for the project. Another important piece of information is the initial rate of absorption or IRA. This is a measure of how quickly the bedding surface of the brick will absorb water. If this value is too low, the brick units may float on the mortar and not achieve proper contact or bond. If the value is too high, units will draw too much water from the mortar and also have poor contact and bond. Knowing the IRA can help you select a mortar mix that is compatible with the units. Whenever possible, I recommend choosing units having an IRA between 5 and 20. Units outside this range can also perform well depending on the mortar type and weather conditions. If the units have an IRA greater than 30, they can be wetted by placing a hose over the brick pile a day before they are used to reduce the IRA. Wetting the brick, however, can cause increased efflorescence and should be avoided during winter construction as the units are more likely to freeze. Finally, check the date of the report. If the report is more than one year old, I recommend having tests performed on the units you plan to use.