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Mortar Patching Holes In Stone Masonry
MORTAR PATCHING HOLES IN STONE MASONRY
PART 1---GENERAL
1.01 SUMMARY
A. This procedure includes guidance on mortar patching holes
in stone masonry where fastenings have been removed by
other trades or damage has occurred for some other
reason.
B. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:
1. Safety Precautions
2. Historic Structures Precautions
3. Submittals
4. Quality Assurance
5. Delivery, Storage and Handling
6. Project/Site Conditions
7. Sequencing and Scheduling
8. General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).
1.02 REFERENCES
A. American Society for Testing and Materials (ASTM)
www.astm.org
PART 2---PRODUCTS
2.01 MATERIALS
A. Patching Mortar:
1. Portland cement: Type I, ASTM C150, white and/or
gray as necessary to match mortar color to adjacent
limestone color.
2. Hydrated masons lime: ASTM C207.
3. Aggregate: Clean sharp sand free of loam, silt,
soluble salts and organic matter.
a. For limestone, aggregate shall conform to the
following size gradations:
Sieve Size Percent Passing
No. 4 100
No. 8 100
No. 16 97
No. 30 76
No. 50 17
No. 100 6
No. 200 0
b. For granite, aggregate shall conform to the
following size gradations:
Sieve Size Percent Passing
No. 4 100
No. 8 97
No. 16 85
No. 30 65
No. 50 28
No. 100 13
No. 200 2
Color and size of aggregate to match existing,
based on RHPO approval.
4. Clean, potable water
C. Anchor dowels, studs
D. Wire armature reinforcing - 16 gauge
E. Epoxy cement or grout
2.02 EQUIPMENT
A. Masonry drill
B. Stiff bristle brushes (non-metallic)
C. Steel trowel
D. Pneumatic or hand tools
2.03 MIXES
A. Proportions for Limestone Patching Mortar:
1. Portland cement: 1 part by volume
2. Lime: 2 parts by volume
3. Aggregate: 9 parts by volume
4. Water: to form a workable consistency
B. Proportions for Granite Patching Mortar:
1. Portland cement: 1 part by volume
2. Lime: 1 part by volume
3. Aggregate: 6 parts by volume
4. Water: to form a workable consistency
C. Mixing Procedures:
1. Measure materials by volume or equivalent weight.
USE A KNOWN MEASURE. DO NOT MEASURE BY SHOVEL.
2. Mix ingredients in clean mechanical batcher for 5-10 minutes.
3. Let mortar sit for 1 hour prior to use to allow for
initial shrinkage. Remix mortar to workable
consistency. Use mortar within 1.5 hours of
initial remixing. Discard left-over mortar. DO
NOT REMIX.
PART 3---EXECUTION
3.01 PREPARATION
A. Protection:
1. Prevent grout or mortar used in repointing and
repair work from staining face of surrounding
masonry and other surfaces. Remove immediately
grout and mortar in contact with exposed masonry
and other surfaces.
2. Protect sills, ledges and projections from mortar
droppings.
B. Surface Preparation:
1. Remove loose particles, soil, debris, oil and other
contaminants from existing stone units at locations
indicated by cleaning with stiff brush.
2. Prepare the patch substrate by carving with
pneumatic stone working tools, "Barre" short stroke
or by hand tools to make a clean surface, roughened
to bond with patch material, and with edges at
least 3/8-inch thick (1 cm), no feather edges, and
undercut to provide a mechanical key for the patch.
3.02 ERECTION, INSTALLATION AND APPLICATION
A. Clean any exposed anchors of corrosion by scraping and
brushing with stiff bristle brushes. Replace any unsound
anchors as necessary with new stainless steel anchors of
same approximate size and shape. Bed new anchors in
epoxy grout.
B. Clean all stone areas to be patched of all debris, dust,
oil, etc. by brushing with a stiff fiber bristle brush.
C. Provide mechanical keys or create wire reinforcing
armature to hold and attach mortar patch.
D. Place patching mortar in layers no thicker than 1/2".
Roughen surface of each layer to provide key for next.
E. Keep each layer damp for 72 hours or until mortar has
set.
F. Dry pack and firmly compact patching mortar in the patch
area, fully embedding reinforcing, free from voids, to
fill the patch area slightly over full for smoothing and
finishing when partially set.
G. Work and finish the patch when mortar has achieved its
initial set and is firm, to match adjacent surfaces and
finishes.
H. Form patches on edge of masonry units to restore the
original unit's line and to maintain clear mortar joint
lines, without bridging any mortar joint, so each stone
unit is separate and not joined to the next one; joints
to be filled by repointing, not mortar patches.
I. Unacceptable patches are defined as those with hairline
cracks or showing separation from stone at edges. Remove
patches and refill to provide patches free of those
defects.
END OF SECTION
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