Patching Minor Chips And Cracks In Terrazzo With Cement Grout
- Procedure code:
- J. Weinberger US Cthouse/San Diego, CA - Hallenbeck Chamorro
- Last Modified:
PATCHING MINOR CHIPS AND CRACKS IN TERRAZZO WITH CEMENT GROUT
A. This procedure includes guidance on repairing small
cracks in terrazzo floors by patching with cement grout.
B. Minor chips and cracking in terrazzo require patching
ONLY when surface irregularities present safety hazards
or when it is necessary to prevent further deterioration
to the terrazzo.
C. 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
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).
A. NTMA Standards: Comply with specified provisions and
recommendations of the National Terrazzo and Mosaic
Association, Inc. (NTMA)
A. Portland Cement: ASTM C150, Type I, except as modified
to comply with NTMA requirements for compressive
strength. Obtain cement from a single source for each
1. Provide non-staining white cement for terrazzo
B. Sand: ASTM C33
C. Clean, potable water
D. Aggregate: Natural, sound, crushed marble chips without
excessive flats or flakes, complying with NTMA
1. Colors and gradation of aggregate sizes as required
to match original existing intact materials and
patterns. Original plans often contain the exact
2. Aggregate colors should be matched after cleaning
or taken from the interior of core samples
depending upon scope of work.
E. Matrix Pigments: Pure mineral or synthetic pigments,
resistant to alkalies and non-fading. Mix pigments with
matrix to provide required colors.
F. Curing Compound: Liquid-membrane-forming compound, ASTM
C309, Type 1.
G. Grout: A cement acrylic grout with color added to match
the matrix of the original terrazzo.
H. Interior Floor Sealer: Colorless, slip and stain
resistant penetrating sealer with Ph factor between 7 and
10, that does not affect color or physical properties of
I. Plastic Sheeting
A. Grinding Stones: Fine grit emery stones manufactured
specifically for restorative type grinding and surfacing
of terrazzo surfaces (#40 and #80 grit stones).
B. Power Saw and Hand Tools
C. Resurfacing Screens: A fine grit screen manufactured
specifically for restorative type grinding and
resurfacing terrazzo surfaces.
A. Surface Preparation:
1. With a power saw or hand tools, cut a vertical
perimeter wall around the area to be patched. If
the patch is smaller than an inch square, slightly
undercut this edge.
2. Clean surface of debris. Saturate void with water
to prevent quick surface drying. Ensure that water
penetrates into the surface in order to achieve a
proper bond. Clean surfaces until any obstructing
material has been removed.
3. Apply cement paste and work into the surface. Do
not allow cement paste to dry before placing
3.02 ERECTION, INSTALLATION AND APPLICATION
NOTE: Match marble chips and matrix for existing terrazzo by
size, mineral content and color. Colors should be matched
after cleaning or taken from the interior of core samples
depending upon scope of work.
A. Mix two parts blended marble chips with one part Portland
Cement and add enough water to make this mix plastic.
B. Place mixture over chip or crack and level with a trowel.
C. Seed additional marble chips of the same blend over the
patch, as required to establish a uniform coverage.
D. Compact patch, removing all excess water and cement from
E. Cover the patch with paper or polyethylene sheeting to
prevent quick hydration. Cure until topping develops
sufficient strength to prevent lifting or pulling of
terrazzo chips during grinding.
F. Sand surface with a hand sander or small grinding tool,
using fine stones to achieve desired finish.
1. Use a #40 or finer grit stone for the initial
grinding, exposing the marble chips. Follow with a
fine #80 grit stone before grouting with cement to
fill all pinholes.
CAUTION: DIVIDER STRIPS MAY BE COATED INSTEAD OF
SOLID COMPOSITION. COATED STRIPS SHOULD NOT BE
GROUND. GRINDING MAY CAUSE COATED DIVIDER STRIPS
TO LOSE THEIR COATING AND DISCOLOR.
2. Cover grouted surface with paper or polyethylene
for at least 72 hours.
3. Thoroughly rinse the surface with clean, clear
4. Remove excess rinse water and machine or hand apply
grout using identical portland cement, color and
pigments as used in topping taking care to fill all
5. Final polish with a #80 or finer grit stone. Care
should be taken to limit grinding and polishing to
a small distance beyond the perimeter of the patch.
G. Seal patch with a penetrating type terrazzo sealer.
END OF SECTION