MASONRY - Materials for Civil and Construction Engineers - page 309

W s - W d

Absorption % = * 100 (8.3)

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W d

W r - W d

Moisture content as a percent of total absorption = * 100 (8.4)

W s - W d

where

weight of specimen, kg (lb)
weight of unit, kg (lb),
weight of specimen, kg (lb), and
of specimen as received

W s = saturated

W d = oven-dry

W i = immersed

W r = weight

Table 8.1 shows the allowable maximum water absorption for load-bearing
concrete masonry units.

Sample Problem 8.2

A concrete masonry unit was tested according to ASTM C140 procedure and pro-
duced the following results:

mass of unit as
saturated mass of
oven-dry mass of

received = 10,354 g

unit = 11,089 g

unit = 9893 g

Calculate the percent absorption and moisture content of the unit as a percent of total
absorption.

Solution

11,089 - 9893

Absorption % = * 100 = 12.1 %

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9893

Moisture content as a percent of total absorption

10,354 - 9893

1 2

= * 100 = 38.5 %

11,089 - 9893

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Concrete masonry units are available in different sizes, colors, shapes,
and textures. Concrete masonry units are specified by their nominal di-
mensions. The nominal dimension is greater than its specified (or modular )
dimension by the thickness of the mortar joint, usually 10 mm (3/8 in.). For ex-
ample, a block has
an actual width of 190 mm (7-5/8 in.), height of 190 mm (7-5/8 in.), and
length of 390 mm (15-5/8 in.), as illustrated in Figure 8.3. Load-bearing concrete

200 mm * 200 mm * 400 mm 8 in. * 8 in. * 16 in.

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