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NOTES
ON FISH PONDS & TANKS
SHEATHING IN GRP (Glassfibre Reinforced Plastic) of Concrete Fish Ponds.
The advantages of a GRP Sheathing over coating the concrete with
"G4" Polyurethane Varnish, for which four coats are used is
that concrete can crack in the winter frosts but the GRP will not crack
and has a glass smooth surface.
TOXICITY Under cured GRP will emanate Styrene (40% content of most
resins). With drinking water tanks this would not be toxic to humans
despite unpleasant taint but would be toxic to fish as they breathe
water. Our final surface coating resin (top coat or flowcoat) is a
quality Isophthalic Gel Coat to which wax has been added at time of
manufacture so that the user does not have to add the tack free solution
which has been added to all initial Gel Coats (which are wax-free) if
they are to be used as Top Coat.
ERECTION OF TENT For Fish Ponds in the open it is essential to erect a
tent: a tarpaulin sheet stretched over horizontal pole and pegged to the
ground. Both ends of the tent must be left open so that the Styrene
fumes can freely escape. If emanation were restricted hardening and cure
would be inhibited. The tent must be longer than the pond to avoid
driving rain entering the open ends at an angle. The tent should be
erected 14 days before commencing work to allow the concrete to
thoroughly dry.
PREPARATION OF THE CONCRETE All corners, vertical and horizontal, must
be rounded with sand and cement as leaks are apt to occur when
dovetailing glassfibre into internal 90 degree angles. The concrete
should be reasonably smooth but not billiard ball smooth as the initial
barrier coat of "G4" would not penetrate as well as it should.
Do not use 'Unibond' as it contains ammonia. There must be no trace of
bitumen as this attacks polyester resin and inhibits hardening. Allow 14
days for sand/cement to dry.
INITIAL BARRIER COAT OF "G4" POLYURETHANE VARNISH The purpose of this is to act as a barrier preventing alkali
in the cement attacking the resin and the dampness striking through the
concrete inhibiting hardening and cure of the resin. The "G4"
is applied in one coat at 210g /sq.metres (10.76 sq.ft). The
"G4" hardens upon contact with air, so tins should be promptly
re-sealed each time "G4" is decanted. It goes tacky-hard in
one hour and continues to cure for 12 hours, but when "G4" is
used in this application the laminating resin
must be applied with a maximum of two hours or sooner after the
"G4" has gone tacky-hard. Delay will inhibit the degree of
adhesion of resin to "G4". The "G4" must be brush
applied: NOT with spray gun as inhalation of fumes must be avoided.
APPLICATION OF GRP SHEATHING
The concrete must be strong, especially the bottom where the weight of
water bears. For ponds up to 5' depth two laminations of medium
thickness Chopped Strand Mat (CSM) described as density 1½ oz per sq.ft. Two
laminations is 3oz. sq.ft. The
sheathing must be carried outwards horizontally over the top of the wall
and 2" down the other side. If
terminated on the horizontal the top edge would be searched by water and
start to de-laminate. Both laminations can be applied without waiting for the
underlying lamination to harden, as also the final surface tissue.
The preferred roller is the aluminium Paddle Roller 6" x 1½" o.d. which has a plastic handle with a socket into which a broom handle
will fit, which eases the work. Always overlap pieces of CSM by 2".
Do not lay edge to edge. The final surface tissue cannot be rolled with
metal roller which would 'pick it up'. It is applied with a brush
stippling action. The CSM and tissue are applied with laminating resin.
As soon as the tissue is hard then the final topcoat (flowcoat)
is applied at spread rate of
2½ oz. per sq.ft. This
can be pigmented with polyester colour paste added to the gel in ratio
not exceeding 10% by weight. Pigmented
gels cure more positively than non-pigmented as UV light inhibits
cure of non pigmented resins. The
usual colour in fish ponds is Super Black.
FINAL CURE Allow a minimum 14 days after work is completed with tent
still erected. Introduction of heat will expedite cure. After this flush
out with hot water, steam or several changes of water. Under cure is
visible if a white sheen appears on the surface of the laminate after
water is introduced.
WORKING TEMPERATURE This
should be not less than 16C = 60F throughout the work. If work has to be
interrupted it may be found that the finished edge of laminate has
curled up away from concrete due to 6% shrinkage of resins as they
harden and cure. Cut this out and overlap 3" onto extant laminate
with the subsequent laminate.
Unit 4, Millbuck way,
Springvale ind estate, Sandbach, Cheshire CW11 3HT
Tel/Fax:(01270)766685
www.resin-supplies.co.uk
Email:
enquiries@resin-supplies.co.uk
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