Page 101 - Masonry and Concrete

Understanding Masonry
100 CHAPTER FOUR

variety of colors and textures. Most manu-
facturers now produce “split-face” or
“rock-face” units which resemble a nat-
ural stone texture, as well as ribbed block,
fluted block, scored block, and units with
raised geometric patterns or smooth
ground faces (Figure 4-12). Architectural
block colors range from creams, buffs, and
browns to reds, pinks, and even greens.
Some colors are produced by using col-
ored aggregates, while others are made by
adding natural or synthetic pigments.
Units made with colored aggregates are
often brighter, and the color will not fade
in the sun. Those made with pigments
come in a greater variety of colors, but
some may fade a little with time.

4.3.4 CMU Properties

FIGURE 4-12A
Unit Strength: Aggregate type, size, and
Split-face block.
gradation as well as water-cement ratio are
important in determining the compressive
strength of concrete masonry units. Manufacturers determine opti-
mum ingredient proportions to obtain a balance among moldability,
handling, breakage, and strength. For non-loadbearing CMU, compres-
sive strength may be as little as 500 psi and still adequately serve its
purpose. For loadbearing applications, CMU should have a minimum
average compressive strength of 1,900 psi. Typically, compressive
strengths range from about 1,000 to 3,000 psi.

Unit Weight: Concrete block can be made with aggregates that are
light, medium, or heavy in weight. The heavy block are made with sand
and gravel or crushed stone and can weigh more than 40 lbs. each.
Lightweight units made with coal cinders, slag, and other aggregates
may weigh as little as 22 lbs. apiece. The lightweight block have higher
thermal and fire resistance but also have higher moisture absorption.

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