MASONRY - Materials for Civil and Construction Engineers - page 317

8.8 A concrete masonry unit has actual gross dimensions of

The unit is tested in a compression ma-
chine with the following results:

7-5/8-*7-5/8-*7-5/8-.

Max. Failure Load
Net volume

= 83 kips

312.7 in 3

=

a. Is the unit categorized as solid or hollow? Why?
b. Calculate the gross area compressive strength.
c. Calculate the net area compressive strength.

8.9 a. Why it is important that, the concrete masonry units meet certain

absorption requirements?
b. A portion of a normal-weight concrete masonry unit was tested
for absorption and moisture content and produced the following
weights:

weight of unit as received
saturated weight of unit
oven-dry weight of unit
immersed weight of unit

= 3.605 lb

= 3.939 lb

= 3.524 lb

= 1.684 lb

lb/ft 3

Calculate the absorption in and the moisture content of the
unit as a percent of total absorption. Does the absorption meet the
ASTM C90 requirement for absorption?
8.10 A portion of a medium-weight concrete masonry unit was tested for
absorption and moisture content and produced the following weights:

weight of unit as received
saturated weight of unit
oven-dry weight of unit
immersed weight of unit

= 5435 g

= 5776 g

= 5091 g

= 2973 g

kg/m 3

Calculate the absorption in and the moisture content of the
unit as a percent of total absorption. Does the absorption meet the
ASTM C90 requirement for absorption?
8.11 A portion of a concrete masonry unit was tested for absorption and
moisture content according to ASTM C140 procedure and produced
the following weights:

weight of unit as received
saturated weight of unit
oven-dry weight of unit
immersed weight of unit

= 7805 g

= 8223 g

= 7684 g

= 4027 g

Determine the following:
a. percent absorption
b. moisture content of the unit as a percent of total absorption
c. density
d. weight classification according to ASTM C90 (lightweight, medium
weight, or normal weight).