Page 102 - Masonry and Concrete

Understanding Masonry
101
UNDERSTANDING MASONRY

4.3.5 Concrete Pavers
Concrete masonry pavers are popular for
residential applications but are strong and
durable enough to be used in commercial
and even municipal paving. Concrete
pavers come in a number of shapes (Figure
4-13) and are designed to be laid on a sand
bed with no mortar between units. The
small units interlock for stability under
traffic loads. The openings in the grid
pavers are filled with gravel, or with soil
and grass, and allow rainwater to percolate
into the ground with virtually no runoff.
Concrete pavers are much stronger and
more dense than ordinary concrete block,
so they will absorb little moisture and not
be damaged by repeated freezing and
thawing. For residential driveways, a
1
thickness of about 3- 8 in. is usually used.
3
For patios and sidewalks, a 2- 8-in. thick-
FIGURE 4-12B
ness is adequate.
Ribbed block.
4.3.6 Coatings for Concrete
Masonry

All concrete and masonry surfaces absorb moisture, some to a greater
or lesser degree than others. A troweled concrete slab or a fired clay
brick, for instance, are more dense and therefore less absorbent than
concrete block. Coatings can be applied to concrete and masonry to
increase resistance to water absorption. Although new brick con-
struction does not usually require such treatment because of the den-
sity of the brick, concrete block is often treated with paint, plaster, or
clear water repellents, particularly in climates with large amounts of
rainfall or cold weather. Light-colored stone is also sometimes treated
with a clear water repellent to help keep dirt from discoloring the sur-
face. Concrete slabs are often treated with clear water repellents to
reduce staining and to reduce freeze-thaw damage from absorbed
water. Clear coatings are thin and do not have any elasticity, so they

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