Geotechnical News • September 2018
33
THE GROUT LINE
The final mix had a UCS of 9,000 PSI
at 28 days.
The custom mix design resulted in sig-
nificant savings as compared to using
pre-confectioned grout mixes.
Mixing and
injecting the
grout
The grout mix
was prepared
and injected with
a ChemGrout
CG-600 Colloi-
dal Mixing Grout
Plant. The plant’s
13-cubic-foot
colloidal mixer
and agitation
tank and positive
displacement
piston pump
allowed workers to mix material and
inject at the pre-existing points. A
telehandler was used to deliver cement
pallets to the CG-600 to keep the grout
flowing. Much like concrete, the grout
had to be injected
immediately after
it was mixed.
A total of 460
cubic feet of
grout was
prepared and
injected into the
fountain.
Drilling or cut-
ting through
the granite and
marble was not
permitted, so
finding suitable
existing open-
ings for injection
ports was key. In
those areas with
smaller holes, the
team altered the
mix design, used
smaller diameter
injection ports,
and adjusted the
flow to achieve
adequate cover-
age with the
lower strength
mix. It was also important to consult
with the owner and design team to
make sure this revised approach was
acceptable to support the restoration
effort. The more flowable mix was
generally 1-94 lbs of cement, 5 gallons
of water, water reducing and flow
enhancement admixtures, as needed.
The injection locations were pre-
determined; however, there were areas
such as the granite blocks from the top
row of stairs that had to be temporar-
ily removed to accommodate injection
ports.
The crew had to stay aware of chang-
ing conditions and respond as needed.
This meant observing the joint for
moisture and watching for unwanted
structural movement. The finished
joints were then plugged with oakum,
burlap, and a stick.
The historic nature of the fountain
required the grouting contractor to
exercise extreme caution to prevent
damage. The hardest thing was to use
the PVC pipe and not get the primer or
glue on the statue.
Two weeks to correct a 141-
year old problem
Despite the complexity of the process,
the grouting work was completed on
schedule in two weeks during August,
October, and November of 2016 with
logistical challenges. Perhaps even
more fascinating is the fact that the
grouting helped to correct problems
that unfolded over 141 years in less
than 14 days. All parties are in agree-
ment when it comes to hoping that the
City of Philadelphia will not be issu-
ing another RFP until at least 2158!
As usual I conclude with the same
request, asking you to send me your
grouting comments or grouting stories
or case histories. My coordinates
remain:
Paolo Gazzarrini,
,
or
Ciao! Cheers!
Grout Fairmount Fountain.
Grout Fairmount Fountain.
