ACCIO NES

The epoxy resins for use in the mortar form shall confirm to the following requirements: i) Pot life: 90 minutes at 25 deg C

60 minutes at 30 deg C 45 minutes at 35 deg C ii) Bond to stone masonry: min 12 Mpa iii) Tensile strength: min 16 Mpa

BS sieve % retained 36 10 52 25 72 20 100 10 150 15 240 20

Article II. 3.0 SOLVENT-LESS EPOXY COATING SYSTEM:

Solvent free transparent epoxy coating system has been proposed since it is characterized by thick non-porous and highly resistant films compared to the conventional solvent containing paints which give thin films with inherent porosity. Silica flour upto 20pbw shall be added in the top coats to increase the abrasion resistance. A flow control agent like butylated urea formaldehyde resin can be used in the top coats to ensure proper spreading of the system without any surface defects like cratering or fish eyes. In order to prevent sagging or flowing off the vertical surface , a thixotropic agent like Aerosil ( DT 075 or XY 36 ) may be incorporated to the extent of 1-3 % of the total binder. The primer & top coat shall satisfy the following requirements at 25deg C & 65 % RH :-

3.1.1 Primer coat:

Viscosity 10000mPa s. Pot life 3hours. Curing time ( touch dry ) about 8 hours. 3.1.2 Top coat:

Viscosity 11000 – 17000 m Pa s. Pot Life 2 hours.

Curing time about 6 hours.

The pot life of the system depends upon the ratio of the hardeners to the resin and may be adjusted to suit the ambient temperature.

The top coat shall have the following characteristics :- Accelerated Weathering : Passes 500 hours. ( ASTM E-42-57 )

Corrosion salt spray : Passes 100 hours. ( ASTM E-117-61 )

Stain resistance : After 10 minute lamp black in oil completely removed. Hot water @ 90 deg C for 10 minutes: No effect.

Following formulations are suggested for trial at site and adoption. Article III. 3.2 PRIMER:

One brush coat of the following system is recommended as primer on the pretreated surface :

• Name of manufacturer : HUNTSMAN OR APPROVED EQUIVALENT. • Product recommended : i) Araldite GY 257 = 100 pbw.

ii) Hardener HY 840 = 50 pbw.

The primer should be allowed to be just tack free prior to the application of the top coats. Article IV. 3.3 TOP COATS:

• Name of manufacturer :- HUNTSMAN OR APPROVED EQUIVALENT. • Product recommended :-

(a) For chemical resistance

i) Araldite GY 250 = 100pbw. ii) Hardener HY 830 = 45 pbw. iii) Hardener HY 850 = 15 pbw. iv) Silica fluor = 20 pbw. v) Flow control agent = 2 pbw.

(a) For other than chemical resistance

i) Araldite GY 257 = 100pbw. ii) Hardener HY 840 = 50 pbw. iv) Silica fluor = 20 pbw. v) Flow control agent = 5 pbw.

Silica fluor upto 10-20 pbw may be added in the above to reinforce the coating and abrasion resistance.

Flow control agent shall be used depending on the site requirement.

The DFT of primer and 2 top coats shall not be less than 400 microns.The temporary protection against corrosion shall be provided by the contractor in an approved manner and which will not hinder the bond with epoxy coating.

4.0 SPECIFICATION FOR EPOXY MORTAR & APPLICATION:

4.1 Proportioning and Mixing:

The resin and hardener shall be mixed before adding the dry filler. The mixed ready to use mortar should not contain lumps of un-wetted filler and should be uniform in colour. For a total weight of 1kg or less, hand mixing will be sufficient. For quantities in excess of 1kg the component shall be mixed for 3 minutes with slow speed 400- 600 rpm. electric drill with a Jiffy mixer. The stirrer shall be moved up and down and along the sides until an even streak free color is obtained. Whipping in an excessive amount of air shall be avoided. If no power is available, a flat putty knife may be used to reach into the corners of the can and hand mixing done for at-least 5 minutes.

4.2 Surface preparation:

Surface upon which epoxy is to be placed shall be free of rust, grease, oil, paint, asphalt, loose materials, unsound concrete, dust or any other deleterious materials. Since cured epoxy does not provide adequate bond with any material, all overlay, whether epoxy or cement based, shall be carried out within pot life of the base epoxy layer. Contaminants, such as oil, grease, tar, asphalt, paint, wax, curing compounds or surface impregnants like linceed oil or silicons, including laitance and weak or loose concrete shall be removed. When bonding to asphalt, the surface should be roughened so that clean aggregate is exposed. Epoxy bonding agents shall not be applied when it rains, or in standing water. The surface must be dry.

Two general methods of surface preparation shall be followed:

a) Mechanical that includes grinding, grit blasting, water blasting and scarification, impact and vibration on the structure shall be avoided.

b) Chemical that includes acid etching with 15% by weight of hydrochloric solution, followed by repeated flushing with high pressure stream of water.

4.3 Application:

Epoxy primer coat shall be applied with the help of stiff nylon bristle brushes or hard rubber rollers or spray gun depending upon nature of surface and extent of work area. As far as possible, the coating shall be uniformly thick.

Before the primer coat is fully cured, epoxy mortar shall be applied by means of trowels and floats. The interval between the application of primer coat and epoxy mortar shall be approximately 15/ 30 minutes depending upon the ambient temperature.

Seal coat shall be applied after 24 hours curing, after mild roughening of the surface of the mortar. Seal coat shall be applied on area, which are not to be covered with liner plate.

4.4 Products Recommended:

• Name of manufacturer :- HUNTSMAN OR APPROVED EQUIVALENT. • Formulation for Bond coat between old concrete and epoxy mortar

i) Resin Araldite GY 250 = 100pbw. ii) Hardener HY 840 = 50pbw. • Formulation for epoxy mortar :-

i) Resin Araldite GY 257 = 100pbw. ii) Hardener HY 840 = 50pbw.

iii) Quartz Sand Mix No 10 = 800pbw.

Formulation for seal coat over epoxy mortar : • Primer / Bond coat

i) Resin Araldite GY 257 = 100pbw. ii) Hardener HY 840 = 50pbw.

• Seal Coat ( One coat )

i) Resin Araldite GY 250 = 100pbw ii) Hardener HY 840 = 50pbw. iii) Hardener HY 850 = 15pbw. iv) Silica Flour = 20pbw.