The block weight per unit face area is listed as an
index statistic to limit pore area and face
thickness. Blocks with thin faces and large pore
spaces can be damaged by traffic or debris hitting
the wall and are less durable. The face thickness
and/or pore area can be specified, but the weight
per face area is more readily available.
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The blocks shall be manufactured to the requirements of ASTM C 1372, except
for the following modifications:
a. Minimum 28-day compressive strength of 31 MPa 4500 psi, based on
net area in accordance with ASTM C 140.
b. A maximum moisture absorption rate of 145 kg/m3 9 pcf, in
accordance with ASTM C 140.
The minimum oven dry density of concrete shall be 2000 kg/m3 125 pcf.
c.
d. The blocks shall provide a minimum of 400 kg/square meter 80 psf of
wall face area (determined without void filling).
e. For freeze-thaw durability tested in accordance with ASTM C 1262,
specimens shall comply with either of the following: (1) the weight
loss of each of 5 specimens after 100 cycles shall not exceed 1
percent; or (2) the weight loss of each of 5 specimens after 150 cycles
shall not exceed 1.5 percent. [ when tested in a 3 percent saline
solution: (1) the weight loss of each of 5 specimens after 40 cycles
shall not exceed 1 percent; or (2) the weight loss of 4 out of 5
specimens after 50 cycles shall not exceed 1.5 percent.]
f. The shear strength between blocks determined in accordance with
NCMA TR127 shall have shear strength meeting the following minimum
requirements:
Minimum Peak Shear Capacity = [_____] kN/m lbs/ft
Friction Angle for Peak Shear Capacity = [_____] degrees
[Minimum Service State Shear Capacity = [_____] kN/m lbs/ft
Friction Angle for Service State Shear Capacity = [_____] degrees]
2.1.3
Wall Caps
Segmental concrete block units shall be placed as caps on top of all
segmental concrete retaining walls. The cap blocks shall have a color and
texture on exposed faces to match that of the other blocks and meet the
requirements for the other blocks except that the minimum height shall be
75 mm 3 inches. Each cap block shall have abutting edges saw cut or formed
to provide tight, flush abutting joints with no gaps in the joints when
placed end to end in the alignment shown on the drawings.
2.2
REINFORCEMENT
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NOTE: Polyester is susceptible to hydrolysis in
alkaline conditions. A high molecular weight and
low carboxyl end group number limit the hydrolysis.
Normally, a mill certificate or certification of
these properties is adequate. The molecular weight
SECTION 02832
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