Industrial Waterproofing and Fluid-Applied Membrane Systems

Article 12 of 24

Material Storage, Conditioning, Mixing, and Proportioning

A properly selected membrane can still fail when its components are frozen, overheated, contaminated, mixed at the wrong ratio, inadequately blended, or applied after the usable working time has expired. Material control begins when the shipment arrives—not when application starts.

Learning Objectives

After completing this article, the reader should be able to:

• Inspect and document waterproofing materials when they arrive at the project.
• Store and condition components within the manufacturer’s temperature limitations.
• Distinguish mixing ratio by volume from mixing ratio by weight.
• Mix one-component and multicomponent materials using controlled procedures.
• Manage induction time, pot life, exotherm, and batch size.
• Verify plural-component equipment ratio and material delivery.
• Maintain lot, batch, quantity, and application traceability.
• Recognize materials that should be quarantined rather than applied.

Material Control Begins at Delivery

Every shipment should be inspected before it is accepted and moved into storage. Damaged, leaking, frozen, overheated, incorrectly labeled, or expired materials should be separated from usable stock until their disposition is determined.

Verify and record:

• Manufacturer and exact product name.
• Component designation, such as Part A, Part B, resin, hardener, or catalyst.
• Container size and quantity received.
• Color or formulation when applicable.
• Lot, batch, and manufacturing numbers.
• Manufacturing date and expiration or use-by date.
• Container seals, lids, labels, and physical condition.
• Required and observed shipment temperature when applicable.
• Consistency with the approved submittal and purchase order.
• Availability of current technical data sheets and safety data sheets.

Never Use an Unidentified Material

Do not use material from an unlabeled container, an improvised container without traceability, or a container whose label no longer identifies the product, component, lot, and hazards.

Color, odor, viscosity, or packaging appearance cannot establish product identity. Quarantine questionable material until the manufacturer or supplier provides written identification and disposition.

Storage Conditions Matter

Waterproofing materials must be stored within the manufacturer’s published temperature range and protected from water, direct sunlight, freezing, excessive heat, ignition sources, physical damage, and contamination.

A controlled storage plan should address:

• Minimum and maximum storage temperature.
• Weatherproof and secure storage.
• Ventilation and fire-protection requirements.
• Segregation of incompatible chemicals.
• Protection of moisture-sensitive components from humid air.
• Secondary containment for leaking containers.
• Spill-control materials and emergency procedures.
• First-in, first-out inventory rotation.
• Daily recording of storage temperature when required.

Freeze-Sensitive Materials

Water-based primers and membranes may be permanently damaged by freezing. Thawed material may appear usable while containing coagulated polymer, separated ingredients, altered viscosity, or reduced film-forming ability.

Do not assume that warming a frozen container restores the product. Mark and quarantine any material known or suspected to have frozen.

Obtain the manufacturer’s written disposition before using freeze-exposed material.

Heat Exposure and Shelf Life

Excessive heat can shorten shelf life, increase container pressure, accelerate reaction, change viscosity, cause skinning, or damage catalysts and reactive components. Materials stored in trailers, trucks, shipping containers, or direct sunlight may reach temperatures far above the surrounding air temperature.

Shelf life normally assumes storage under specified conditions in unopened original containers. A product may not remain acceptable through its printed shelf life if it was stored improperly.

Expired material should not be used merely because it appears normal. Obtain written manufacturer authorization supported by the required testing or replacement documentation.

Storage Temperature and Application Temperature Are Different

A product can be stored within its permitted range and still be too cold or too warm for application. Material temperature affects viscosity, pumping, atomization, mixing, pot life, sag resistance, leveling, coverage, reaction speed, and cure.

Condition all components to the manufacturer’s required application range before mixing. Measure the material itself rather than relying only on room or outside-air temperature.

Material Conditioning

Move materials into a controlled conditioning area early enough for the complete container to reach the specified temperature. Warming only the outer portion of a drum or pail can create large internal temperature and viscosity differences.

Use only manufacturer-approved conditioning methods. Avoid:

• Open flames or improvised burners.
• Uncontrolled space heaters directed at containers.
• Heating above the published limit.
• Allowing water to enter around lids, vents, or drum openings.
• Using heaters not approved for the hazardous location or material.
• Heating one component while leaving the matching component cold.

Review the Instructions Before Opening Containers

Confirm the following for each product:

• Whether each component requires premixing.
• Mixing ratio and whether it is stated by volume or by weight.
• Required mixer, blade, speed, and mixing time.
• Whether the container sides and bottom must be scraped.
• Whether double mixing or box mixing is required.
• Required induction time.
• Pot life at the anticipated material temperature.
• Whether thinning is prohibited or permitted only with a named thinner.
• Application and recoat limitations.
• Required personal protective equipment and ventilation.

Premixing Individual Components

Pigments, fillers, catalysts, and other ingredients may settle during storage. Some resin components must be thoroughly premixed before any material is removed or combined with another component.

Premix using the specified blade and speed until the component is uniform from the top to the bottom of the container. Avoid excessive speed that introduces air, creates a vortex, overheats the material, or splashes hazardous product.

Do not premix reactive hardeners or moisture-sensitive components unless the manufacturer specifically requires it.

Volume Ratio and Weight Ratio Are Not Interchangeable

A product mixed at two parts resin to one part hardener by volume is not necessarily mixed two to one by weight. Components commonly have different densities.

Converting a volumetric ratio to a weight ratio requires the manufacturer-approved density of each component and the correct calculation. Density can vary by formulation, color, lot, temperature, and measurement method.

Use the ratio exactly as stated. Do not create a field conversion unless the manufacturer provides or approves the weight ratio in writing.

Understanding Mixing Ratios

Partial-Kit Mixing

Partial kits increase the risk of ratio errors, inadequate component premixing, contamination, and loss of traceability. Use complete factory-proportioned kits whenever practical.

When partial kits are expressly permitted:

• Premix the required components before removing material.
• Use calibrated measuring containers or a verified scale.
• Use the manufacturer’s approved ratio and calculation.
• Do not estimate quantities using marks on an irregular container.
• Use clean tools dedicated to the appropriate component.
• Reseal remaining material immediately.
• Record the amount removed and remaining inventory.
• Preserve the original product, lot, and hazard identification.

Select the Correct Mixer

The mixing blade must move the complete batch without drawing excessive air into it. Blade diameter, shape, speed, container geometry, material viscosity, and batch size all affect mixing quality.

Avoid:

• A small blade that mixes only the center of the container.
• A high-speed blade that creates a deep vortex.
• A dirty blade carrying cured material or another product.
• Mixers contaminated with oil, water, solvent, or cleaning residue.
• Mixing equipment capable of generating an ignition source where flammable vapors may be present.

Controlled Batch-Mixing Procedure

1. Verify the product, component, lot number, expiration date, and required ratio.
2. Measure and record material temperature.
3. Premix individual components when required.
4. Measure the components accurately or combine complete factory-proportioned kits.
5. Mix using the approved blade, speed, and duration.
6. Move the mixer throughout the container without striking the sides or introducing excessive air.
7. Scrape the sides and bottom only as directed by the manufacturer.
8. Transfer to a clean container and remix when double mixing is required.
9. Add aggregate, powder, catalyst, or other material only in the specified sequence.
10. Observe the required induction time.
11. Mark the container with batch number, mixing time, and discard time.
12. Move the mixed material promptly to the application area.

Double Mixing

Double mixing, sometimes called boxing, reduces the risk that unmixed material remains on the sides or bottom of the original mixing container.

After the initial mix, transfer the material into a clean container and mix again for the specified time. Do not scrape unmixed residue from the original container into the application area.

Use double mixing whenever the manufacturer requires it or when the approved project procedure includes it.

Induction Time

Some multicomponent materials require a waiting period after mixing and before application. This induction time allows the chemical reaction to begin and may be necessary for proper application, cure, and performance.

Induction time is not optional downtime. Record the mixing time and the earliest permitted application time for every batch.

Pot Life

Pot life is the usable period after reactive components are combined under stated conditions. It is not necessarily the time until the material becomes solid.

A material can exceed its pot life while remaining liquid. Its viscosity, wetting, adhesion, leveling, cure, and mechanical properties may already be changing.

Pot life is influenced by:

• Material temperature.
• Ambient temperature.
• Mixed mass and container shape.
• Component ratio and mixing accuracy.
• Product formulation and catalyst level.

Mark a clear discard time on every mixed container. Dispose of expired material according to the safety data sheet and project waste procedure.

Never Add Solvent to Extend Pot Life

Adding solvent, water, fresh material, or another component does not reverse the chemical reaction of an expired batch. It changes the formulation and can reduce solids, alter cure, create porosity, change viscosity, and damage membrane performance.

Thin material only when the manufacturer’s written instructions permit it, using the exact named thinner and stated quantity for the stated purpose.

Exothermic Reaction

Some multicomponent materials release heat as they react. A large mass retained in a pail can become much hotter and cure much faster than the same material spread across the substrate.

Excessive exotherm can shorten working time, generate fumes, deform containers, damage the material, or create a burn and fire hazard.

Mix only the quantity the crew can apply within the usable period. Follow the safety data sheet and manufacturer’s instructions for handling reacting or abandoned material.

Adding Powder or Aggregate

Cementitious membranes, reinforced mortars, fillers, and certain broadcast systems may require powder, aggregate, or another dry material to be added to liquid components.

Control:

• The exact liquid-to-powder ratio.
• The order and rate of addition.
• Mixer speed and blade location.
• Dust collection and respiratory protection.
• Mixing time and required lump-free consistency.
• Slake or induction time when required.
• Prohibition against adding extra water to improve workability.

Plural-Component Proportioning

Fast-reacting polyurethane, polyurea, and hybrid membranes may be supplied through heated plural-component proportioning equipment. The equipment meters separate components, heats them, delivers them through separate hose passages, and combines them at or near the spray gun.

Controlled operation requires:

• Correct feed-pump operation and adequate inlet supply.
• Clean inlet screens and filters.
• Correct component temperature and viscosity.
• Functioning heaters, temperature sensors, and heated hoses.
• Correct proportioner displacement and ratio configuration.
• Balanced and stable dynamic pressures.
• Properly sized gun mixing chamber or static mixer.
• A documented ratio-verification procedure.
• Defined shutdown, flushing, and maintenance procedures.

Ratio Verification

Gauge pressures alone do not prove that the correct component volumes are reaching the gun. Pressure imbalance can indicate restrictions, temperature differences, depleted supply, pump wear, filter blockage, or other problems, but apparently balanced pressures do not guarantee accurate ratio.

Use the equipment and material manufacturer’s approved ratio-verification method. This may include:

• Separate timed component-output collection.
• Volume comparison using calibrated containers.
• Weight comparison using approved component densities.
• Machine-generated ratio or flow monitoring.
• Daily material-usage reconciliation.

Record the test method, temperature, pressure, collected quantity, acceptance range, date, time, and person performing the verification.

Density Can Support Ratio Verification

When components have different densities, equal volumes will not have equal weights. ASTM D1475 provides a laboratory method for determining the density of liquid coatings and their components.

Density information may be used as part of an approved weight-based ratio check, but only when the component densities, temperature corrections, calculations, equipment, and acceptance limits are established.

Do not improvise a field weight ratio from a volumetric ratio without written manufacturer guidance.

Warning Signs of Off-Ratio Material

• Unusual color or visible streaking.
• Soft, sticky, brittle, oily, or uncured membrane.
• Abnormal odor, smoke, or reaction heat.
• Unexpectedly slow or fast cure.
• Material pulling away, blistering, or separating.
• Irregular spray pattern or poor atomization.
• Large pressure difference between components.
• Repeated equipment shutdown or crossover.
• Component consumption inconsistent with the specified ratio.
• Unusual buildup at the gun or mixing chamber.

Stop When Ratio Is Questionable

Continuing to apply material after an alarm, pressure imbalance, temperature failure, empty component container, pump problem, or abnormal cure can expand a small equipment issue into a large removal and replacement project.

Stop application, mark the last known acceptable location, identify the potentially affected area, verify equipment operation and ratio, document the event, and obtain the required corrective direction before restarting.

Contamination Between Components

Keep pumps, transfer hoses, measuring tools, lids, mixing blades, and containers dedicated to the correct component. Even a small quantity of the opposite reactive component can cure inside a drum, pump, valve, hose, or container.

Protect moisture-sensitive components from humid air and water. Use desiccant dryers, nitrogen blankets, sealed vents, or other controls when required by the equipment or material manufacturer.

Never return unused mixed material to an original component container.

Batch Size and Crew Production

Batch size should match the crew’s actual placement rate under current project conditions. Corners, penetrations, reinforcement, vertical surfaces, limited access, and hot weather reduce the quantity that can be placed within pot life.

Smaller controlled batches generally produce less waste and better workmanship than large batches that force the crew to rush.

Conduct a production trial or mockup before setting the full batch size and mixing interval.

Batch Traceability

Every mixed batch should be traceable to the material lots and installation area where it was used. If a product or mixing problem is discovered later, traceability helps define the affected work instead of placing the entire project under suspicion.

Assign a batch number and record:

• Product and component names.
• Lot numbers.
• Quantity of each component.
• Mixing ratio and method.
• Material temperature.
• Mixing, induction, application, and discard times.
• Exact installation area.
• Crew member who performed the mixing.
• Observed problems and corrective actions.

Material-Control Checklist

Quarantine Conditions

Do not apply material when:

• The product or component cannot be positively identified.
• The original label or lot number is missing.
• The container is leaking, swollen, damaged, rusted through, or previously opened without control.
• The material is expired.
• The material may have frozen or exceeded storage-temperature limits.
• Unexpected skinning, gel, sediment, lumps, crystallization, or separation is present.
• The wrong component, catalyst, aggregate, or thinner was supplied.
• The correct mixing ratio cannot be confirmed.
• Water, oil, solvent, or another product may have contaminated the material.
• Manufacturer instructions or safety documentation are unavailable.

Worker Protection and Hazard Communication

Waterproofing materials may contain isocyanates, amines, solvents, reactive diluents, acrylic monomers, catalysts, cement, silica, or other hazardous ingredients. Hazards vary by product and task.

The employer must establish the required controls, which may include:

• A written hazard-communication program.
• Accessible current safety data sheets.
• Properly labeled original and secondary containers.
• Employee hazard and task training.
• Ventilation and exposure controls.
• Appropriate gloves, clothing, eye, face, and respiratory protection.
• Medical evaluation, fit testing, and respiratory-program requirements where respirators are used.
• Spill, fire, first-aid, decontamination, and emergency procedures.
• Proper waste handling and disposal.

Field Principle: The Applied Membrane Begins in the Container

Storage, conditioning, ratio, mixing, pot life, and proportioning determine what material reaches the substrate. Once an off-ratio or damaged product is installed, surface appearance alone cannot restore the intended chemistry. Control every component and document every batch before application.

Technical References

• ASTM D1475-13(2025): Standard Test Method for Density of Liquid Coatings, Inks, and Related Products. ASTM International
• ASTM D562-10(2023): Standard Test Method for Consistency of Paints Measuring Krebs Unit Viscosity Using a Stormer-Type Viscometer. ASTM International
• ASTM D2369-24: Standard Test Method for Volatile Content of Coatings. ASTM International
• OSHA 29 CFR 1910.1200: Hazard Communication. Occupational Safety and Health Administration
• OSHA 29 CFR 1910.134: Respiratory Protection. Occupational Safety and Health Administration
• The membrane manufacturer’s current technical data sheets, safety data sheets, mixing instructions, catalyst charts, component-density information, storage requirements, equipment instructions, ratio tolerances, pot-life data, and written project recommendations.

Professional responsibility: Follow the contract documents, current manufacturer instructions, equipment manuals, safety data sheets, applicable fire and environmental requirements, and OSHA regulations. Do not change a mixing ratio, catalyst quantity, component, thinner, storage condition, or proportioning procedure without written manufacturer authorization.

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