restriction.
Use of blocks with a sculptured face (uneven,
beveled, or rounded) usually requires maintaining a
half-bond (stacking the vertical joint at the
midpoint of the underlying block) for architectural
reasons. Wall batter on curves changes the wall
(arc) length between courses. Straight face blocks
may be laid without maintaining half-bond and are
better suited for curved walls. Steep wall batter
curves.
The NCMA design manual is only applicable to wall
batter between 0 and 15 degrees (about 1H:4V).
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a.
Face color - [Tan/Grey/Brown/Natural Limestone].
b.
Face Texture - [split face typical of broken mortar/brick face].
c. Face Appearance - [straight, single-surface face/sculptured with
3-surface beveled face/rounded, smooth-curved face].
d. Batter - Blocks shall be engaged to the block below by use of keys,
lips, pins, clips, or other reliable mechanism to provide a consistent
wall batter [between 1H:6V and 1H:16V].
e. Block Size - a minimum of 0.06 square meters 2/3 square feet of
face area, and minimum 150 mm 6 inch height.
f. Bond configuration - No bond configuration is required for straight
face blocks. Beveled or sculptured face blocks shall be designed to
stack with a half-bond (joints located at midpoint of vertically
adjacent blocks). The block edges shall be finished so that vertical
joints are flush.
2.1.2
Structural requirements
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NOTES: Durability - AASHTO has proposed
specifications for blocks that include: minimum
compressive strength = 28 MPa (4000 psi) and
absorption not exceeding 5 percent (Ref. 1997
Interim Revisions to the Standard Specifications for
Highway Bridges). Additional options to increase
resistance to chloride attack along roads includes a
sloped cap block, surface sealing the completed
wall, and higher compressive strength.
Freeze-thaw Testing - The first choice is the
default requirement in ASTM C 1372, but is not
required by the ASTM test (1997) unless testing is
required by the specifier. The second choice for 3
percent saline solution is used by the Minnesota
Department of Transportation. The specifier should
edit this based on the project's location since
other states may have different requirements.
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