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Control Joints | Compressive Strength | Weight Classifications | Integral colored CMU
Weight Classifications and Aggregates
Concrete Masonry Units (Blocks) are divided into three different classifications based on the density of the concrete used in their manufacture. Light Weight units are manufactured from concrete that has a cubic foot weight of <105 pounds. Medium Weight units are manufactured from concrete that has a cubic foot weight between 105 and <125 pounds. The concrete used in the production of Normal Weight units must have a density >125 lbs per cubic foot. Central Premix can manufacture all three types, although our standard inventory is Medium Weight block.
Two other important requirements to consider are compressive strength and absorption. The minimum compressive strength requirement for all three classifications is identical, 1900 psi net are strength. Sometimes normal weight block are specified under the impression that the customer will get a stronger block, which is not the requirement. If high compressive strength units are required, the strength must be specified. Normal Weight block must meet a higher standard in regards to absorption per cubic foot.
Lightweight block have the highest fire rating, the lowest labor rate for installation, the highest R value and have better sound absorption rating than the other two classifications, but because of the specialty aggregate needed to obtain the Light Weight classification, are generally the more expensive units. Because of their weight, the labor rates for installing normal weight block are higher than the other two classifications, but also because of their weight they are more effective in curbing sound transmission resulting in a higher sound transmission class rating.
The most common lightweight aggregate available in our area is Pumice, which is very commonly used. Central Premix does have the ability to produce block with other specialty aggregate as well such as Light Weight Expanded Shale and colored aggregates upon special request.
Contact a Central Premix representative to find out more about specialty products available from our production facility.
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Central Pre-Mix Concrete Products Co
E 16310 Marietta Ave, Spokane WA, 99216
Phone: 800-950-6290
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