Masonry Magazine April 1966 Page. 25
AIA 10-C
An Information
series from
NCMA TEK 4
National
Concrete
Masonry
Association
✔Concrete Masonry Retaining Walls
16, National Concrete Masonry Association
general
The purpose of a retaining wall is to
mold back a mass of earth or other
naterial. Two common types are the
"gravity" and "cantilever" designs. A
gravity type depends primarily upon its
own weight to hold back the earth,
while a cantilever type utilizes the weight
of the soil together with its strength to
ccomplish the same end. For walls ex-
eeding three feet in height, the canti-
ever type setaining wall of reinforced
oncrete masonry provides a most eco-
omical and attractive construction.
The cantilever retaining walls discussed
ere are of reinforced concrete masonry
onstruction. Reinforced concrete
masonry reacts in much the same man-
mer as reinforced concrete-the masonry
nits, the steel reinforcement, and the
mortar or grout which surrounds the
teel all work together to resist stresses.
By following the design tables herein,
antilever type reinforced concrete
masonry retaining walls can be built
imply and effectively to heights of nine
ect.
2% parts of sand and 4 parts of gravel.
Gravel should be well graded and not
exceed 1/½ inches in size. Amount of
water used for each bag of cement
should not exceed 5½ gallons unless the
sand is very dry.
TABLE I-MORTAR PROPORTIONS BY VOLUME
Mortar Type
Parts by
Volume of
Portland
Coment
or Portland
Blast-
Furnace
Slag Cement
Parts by
Volume of
Type II
Masonry
Cement
Parts by
Volume of
Hydrated Fine Aggregate Measured in a Damp, Loose
Lime or
Lime
Putty
Condition
PM.
1
1
PL
1
36 to 3½
2% to 3 times the sum of the volumes of
the cementitious materials.
TABLE II-GROUT PROPORTIONS BY VOLUME
Type
Parts by Vol-
une of Portland
Cement
or Portland
Blast-Furnace
Slag Cement
Parts by
Volume of
Hydrated
Lime or
Lime Putty
Aggregate, Measured in a Damp, Loose Condition
Fine
Coarse
Fine grout
1
0 to 1/10 25% to 3 times the sum of
the volumes of the
cementitious materials
materials
Concrete Masonry Units-Concrete
nasonry units for retaining wall con-
truction should comply with the re-
quirements of "Specifications for Hollow
Load Bearing Concrete Masonry Units,"
ASTM C90-64T. Units having two or
hree hollow cells are used, the former
Being more popular because the larger
ells facilitate placement of steel and
grout in the spaces.
Concrete-Concrete for footings should
e mixed in the following approximate
roportions: 1 part of portland cement,
Coarse grout.
1
0 to 1/10 26 to 3 times the sum of 1 to 2 times the sum of
the volumes of the
cementitious materials
Mortar and Grout-Mortar and grout
for use in reinforced block retaining
walls should comply with the require-
ments of "Specifications for Mortar and
Grout for Reinforced Masonry," ASTM
C476-63. Tables I and II list the propor-
tion requirements of this specification.
Use fine grout where grout space is less
than three inches in its least dimension.
Coarse grout is used where the least
the volumes of the
cementitious materials
dimension of the grout space is three
inches or more. You'll find requirements
for aggregates in ASTM C404-61,
"Standard Specifications for Aggregates
for Masonry Grout."
Reinforcement-Steel reinforcement
should be clean, free from harmful rust,
and should comply with pertinent ASTM
specifications for deformed bars and
steel wire.