This Section Requires Effective Proof Reading and Altered As Deemed Necessary. It Also

19.  Epoxy Resins

[This section requires effective proof reading and altered as deemed necessary. It also requires a critical review in the light of more current practice, codes and specifications.]

19.1  General

This Specification applies to epoxy resins as coatings, adhesives and structural systems in the construction, maintenance and repair of concrete structures.

The Contractor shall employ, or seek the advice of personnel, experienced in the use and application of epoxy materials in the construction of the works, and shall provide the Superintendent with evidence of such experience before work is commenced.

Epoxy resins may be modified by the use of flexibilizers, plasticisers, dilutants, fillers and pigments, subject to the approval of the Superintendent. The choice of the correct system for a given application shall be based on modulus of elasticity, creep characteristics, rate of heat development, and quantity of heat developed during cure. The Contractor shall seek the manufacturer's guidance as to the most suitable system for the required application and shall abide by the manufacturer's recommendations as to properties of the materials to be used.

It is brought to the attention of the Contractor that adverse environmental conditions will severely affect the performance of the epoxy resin, and the Contractor shall schedule his work to coincide with suitable environmental conditions or provide a favourable artificial environment at his own expense.

The Contractor shall be solely responsible for the performance of the epoxy resin and its conformance to the Specification and Drawings.

19.2  Standards

Conform to the following standards unless specified otherwise:

Comply with the additional requirements of this Specification.

Comply with the requirements of this Specification if they contradict clauses in the above Standards.

19.3  Materials

19.3.1  Definitions

For the purpose of this Specification the following definitions will apply.

Adhesive / : / An adhesive is a substance capable of holding solid materials together by surface attachment.
Epoxy Resin / : / A resinous polymer containing more than one epoxide group per molecule and which is capable of being converted to a useful thermoset form by reaction with a second component called a hardener. The converted material is also referred to as epoxy resin.
Hardener / : / Chemicals resinous in form capable of reacting with epoxide groups in epoxy resins to produce a cross-linked polymer. They usually contain amine or amide groups.
Flexibilizers and Plasticisers / : / These are usually long chain liquid compounds added to the epoxy resin. Some react during cure to impart a degree of resilience and toughness to a normally rather rigid system. Others are non reactive and are commonly described as plasticisers.
Fillers, Extenders and Pigments / : / These are finely divided, non-reactive inert materials, added to epoxy resins to modify certain properties such as consistency, density and colour.
Aggregates / : / Stable, non-reactive minerals of specified size grading, which have adequate hardness and strength. Aggregates and sands used for portland cement concrete are usually satisfactory, but must be dust free and oven dry.

19.3.2  Physical Requirements

The epoxy resin shall not react chemically with the environment in which it is placed and shall remain stable. The curing period of the epoxy shall be such as to allow adequate time to complete the required operations at the maximum operating temperature.

The epoxy resin used for a particular job shall have properties suited for the job application as recommended by the manufacturer and approved by the Superintendent.

19.3.3  Sampling and Testing

At least six weeks prior to using an epoxy resin and on request at any other time during the Contract, the Contractor shall make available to the Superintendent two litres of each component of each type of epoxy proposed to be used on the Contract. No epoxy shall be used until the results of the tests on the samples are known and the Superintendent gives his permission to proceed.

The Superintendent may, at his discretion arrange to take samples from each separate batch of the delivered epoxy resin. These samples shall be submitted to such tests as are deemed to be necessary by the Superintendent to prove their conformity with the manufacturer's advance samples and with the details given in the manufacturer's product data sheets.

19.3.4  Information to be Provided by the Supplier

-  Mixing directions for the base/hardener components of the system.

-  Surface preparation needed or other conditions for use.

-  Minimum and maximum application temperature in degrees C.

-  Curing conditions including maximum and minimum curing temperature in degrees C.

-  Percentage by weight of volatile material in the mixed resin system.

-  Percentage by weight of volatile material in the mixed resin system.

-  Modulus of elasticity.

-  Viscosity.

-  Batch number and date of manufacture.

-  Port or working time in relation to variable air temperature.

-  Safety precautions.

-  Storage temperature of epoxy resin.

-  Shelf life.

19.3.5  Rejection and Replacement

If, in the opinion of the Superintendent, the samples taken from the epoxy resin delivered to the work are of inferior quality to the advanced sample, the Superintendent may reject all material delivered to the work which, in his opinion, is represented by the samples. Rejected material shall be replaced by the Contractor at his own cost, or the Superintendent may elect as an alternative to reject that material for further supply to the Contract.

19.3.6  Test Method

The basic properties of the epoxy resin shall be tested by the manufacturer in accordance with the following Test Methods:

-  Making and Curing Concrete Test Cylinders.

-  Preparation of Epoxy Mortars.

-  Making and Curing Epoxy Mortar Test Specimens for determining compressive strength and Flexural Strength.

-  Inspection and Capping of Epoxy Resin Mortar Compression Test Specimens.

-  Composite cylinder test for Evaluation of hydrophilic concrete adhesive.

-  Tensile Bond Strength of Epoxy Resin Mortar.

-  Compressive strength of Epoxy Resin Mortar Specimens.

On request to the Superintendent, details of the above standard Test Methods will be made available to the Contractor and Manufacturer.

19.3.7  Properties in the Uncured State

SHELF LIFE - The two part epoxy components shall comply with all properties specified for a minimum period of 18 months after delivery. The expiry date of the shelf life shall be marked on each container.

WORK TIME - After blending of both component parts of a mix at 23°C + or - 20°C, the viscosity of the mixture shall remain within a workable range for at least 30 minutes.

HARDENING TIME - When mixed in the proportions recommended for a project, the compressive strength of epoxy resin mortar or concrete at 24 hours after mixing and curing at 23 deg. C + or - 20 deg. C shall be not less than 75% of the strength developed in 7 days at 23 °C + or -20 °C.

19.3.8  Properties in the Cured State

ADHESION - When tested in accordance with Test Method No 5, strength of the composite cylinders shall be at least 90% of the control specimens at 14 days after preparation of composite specimens.

COMPRESSIVE STRENGTH - when tested in accordance with Test Method No 7, the compressive strength shall be not less than 70 MPa at 7 days.

19.3.9  Supply

The material shall be packed in standard commercial containers so constructed as to protect the product from contamination and ensure acceptance by common or other carriers for safe transportation to the point of delivery.

The quantities of resin and hardener packed in their separate containers shall be such that when the contents of the containers are mixed the epoxy materials shall be in their required reacting ratio.

19.3.10  Safety Precautions

Before using the epoxy compound, the manufacturer's technical data shall be read with particular reference to information on protective measures.

All personnel shall be fully instructed in the potential hazards of the material, correct use of equipment, protective clothing, washing procedures, washing materials and barrier creams.

Particular care shall be taken to prevent the material from coming into contact with the skin.

Hands shall be washed prior to use and a protective cream (Barrier Cream) applied. Long sleeves and rubber gloves (preferably disposable plastic gloves) shall be worn and the insides of the gloves kept scrupulously clean. After use, hands must be washed in soapy water.

Should epoxy material contact the skin or eyes, the removal of epoxy from the skin shall be done only by washing thoroughly with soap and water, and eyes shall be flushed for ten minutes or more with water and secure immediate medical aid.

The use of barrier substances shall not be regarded as a substitute for wearing protective gloves.

19.3.11  Storage

Components of epoxy resin shall be stored at a temperature recommended by the manufacturer. Components shall not be kept for more than one year and shall be checked before use for signs of crystallisation.

19.3.12  Mixing

All materials and equipment required for mixing the epoxy shall be approved by the Superintendent.

Mixing shall be done in accordance with the manufacturer's directions and as approved by the Superintendent.

To ensure optimum properties, the epoxy resin shall be thoroughly mixed with the correct amount of hardener as specified by the manufacturer. Mixing shall be done in a manner which will prevent frothing or air entrainment and prevent reduction in strength of the finished product. Mechanical mixing is preferable to hand mixing. Minimum time of mixing is five minutes.

19.4  Surface Preparation

Surface preparation shall remove all dust, scale, oil, grease, dirt or any foreign matter that could prevent the adhesive contacting a solid surface. When removal of concrete is required this shall be achieved by grinding, abrasive blasting, jackhammering, hand chipping, compressed air and water, or high pressure water jet. The use of hydrochloric acid may be permitted by the Superintendent for selected applications.

The Contractor shall adopt methods of surface preparation in accordance with the relevant methods A to H inclusive of this Specification and to the Superintendent's approval.

The Contractor shall be wholly responsible for adequate surface preparation prior to the application of epoxy resins.

19.4.1  Method A - Solvent Degreasing Refer AS 1627

This method shall be used to remove oil, grease, wax, tar and other solvent soluble contaminants from the surface of non-porous materials. Large quantities of contamination shall be removed by hand or power tools prior to solvent cleaning.

Suitable solvents are:

PETROLEUM SOLVENTS - Such as white spirits or mineral turps. Petrol shall not be used because of its highly flammable nature and the danger of lead poisoning. Other low boiling point petroleum solvents such as Shell X55 and Shell X2 are also extremely flammable.

AROMATIC SOLVENTS - Such as Xylol or Solvent Naphtha. Benzol shall not be used because of its extreme toxicity.

CHLORINATED SOLVENTS - Such as Trichlor-ethylene. To be used only in equipment and by methods approved by the manufacturer. Carbon tetrachloride shall not be used because of its extreme toxicity. "No Smoking" shall be enforced when using chlorinated solvents, because although non-flammable, they are converted to highly dangerous phosgene when inhaled through a burning cigarette.

Surfaces may be cleaned by solvents using several techniques:

-  Immersion in the solvent.

-  Spraying with the solvent.

-  Swabbing with rags or cloths.

-  Immersion in boiling solvent vapour (Trichlorethylene) using suitable equipment.

Except for the last method repeated cleaning using fresh solvent shall be done for a completely clean surface.

After cleaning, surface preparation shall proceed as specified below. Methods B, C, D or F shall be adopted when long term strength is required.

19.4.2  Method B - Abrasive Blast Cleaning Refer AS 1627

Abrasive blast cleaning shall be used for steel surfaces to a Clause 3 standard as specified in the current AS 1627. Degreasing of steel surfaces shall be undertaken before abrasive blast cleaning commences. The abrasive used shall be approved by the Superintendent. Abrasive blast cleaning may also be used on galvanised steel, concrete, plastics and ceramics.

Before abrasive blasting a surface, heavy rust, weld spatter or major irregularities which would interfere with close contact between mating surfaces shall be removed by mechanical means. Heavy deposits of oil, grease, wax, or tar shall be removed by solvent cleaning (Method A) before abrasive blasting.

After abrasive blasting the surface shall be cleaned of any traces of blast products by clean brushing, blowing with clean dry air or vacuum cleaning. After cleaning the surface should be promptly coated with the adhesive before contaminations can occur.

19.4.3  Method C - Ferric Chloride Etching

This method shall be used to prepare copper, brass and bronze. These metals are subject to rapid surface tarnishing and shall be coated with adhesive immediately after preparation. Abrasive blasting provided a surface roughness which gives improved adhesion.

The surface shall first be degreased by solvent washing (see Method A).

Ferric chloride solution is made from:

Ferric Chloride : 300 g

Distilled Water : 1000g (1 Litre)

70 percent Nitric Acid : 200 g (140 ml)

IMPORTANT - The ferric chloride shall be dissolved in the water and then the nitric acid added with stirring. A glass or glazed earthenware container shall be used to hold the solution.

The surface to be etched shall be immersed in the bath at 25 deg. C for 1 to 2 minutes, washed thoroughly with clean water and finally rinsed with Distilled water.

19.4.4  Method D - Chromic Acid Etching

This method shall be used to prepare aluminium surfaces which have a tightly adherent film of inert aluminium oxide which shall be removed to make a successful adhesive joint.

The aluminium shall first be degreased by solvent washing (Method A), followed by the chromic acid etching.

Glass or glazed earthenware containers shall be used to hold the chromic acid solution. Eye protection and protective clothing shall be worn at all times when using chromic acid.

The chromic acid solution is made from:

Water : 7500 g (7.5 litres)

Sodium di-chromate@ : 500 g

98 percent Sulphuric Acid : 5000 g (2.25 litres)

IMPORTANT - The sodium di-chromate shall be dissolved in the water and then the sulphuric acid added slowly with stirring. Water shall not be added to sulphuric acid as violent reaction will result.