512 Treating Concrete

Description (512.01)

This item deals with a variety of concrete treatments, including concrete surface sealing, horizontal crack sealing, vertical crack sealing, and waterproofing.

Materials (512.02)

For sealing of concrete surfaces, the Contractor must use products from the Qualified Product List (QPL) listed on the Office of Materials Management’s (OMM) website for Epoxy-Urethane sealers per C&MS 705.23A and Non-Epoxy sealers per 705.23B.

For sealing concrete bridge decks, the Contractor must use products on the QPL for High Molecular Weight Methacrylate (HMWM) Resin per 705.15, for Soluble Reactive Silicate (SRS) per 705.24, and Gravity Fed Resin per 705.25.

For sealing concrete cracks, the Contractor must use products on the QPL for Epoxy Injection per 705.26.

For waterproofing concrete surfaces, the Contractor must use products on the QPL for fabric and membrane material per the applicable sections of 711 and for asphalt primers and sealers from the applicable sections of 702 and 705.

Sealing of Concrete Surfaces (512.03)

Equipment (512.03.A)

The Contractor must follow the manufacturers’ recommendation for applying the sealer. Although spraying methods allow for higher production rates and cover profiled surfaces more easily than rollers, over –spraying must be contained and respirators and personal protection will be required. The sealer is commonly applied with rollers. When using rollers, brushes may also be required to apply the sealer to bug holes and joints. The equipment must be clean, free of contaminants, oil, and water.

Mixing (512.03.B)

The Contractor must mix the sealer according to the manufacturer’s recommended procedures. Mixing paddles must be jiffy type, not wire whips. The mixer should be run at 400 to 600 rpm and be able to efficiently move the material for blending and not incorporate air into the mix. Material should be mixed to a consistent color for not less than three minutes.

Materials cannot be extended or thinned. Improper mixing may cause poor or no hardening and inconsistent color. Induction or rest periods impact the materials viscosity and pot life. Do not use material beyond its pot life.

Figure 512.A – Poorly Mixed Material

Figure 512.B – Remnants of Material Applied Beyond Pot Life

Storage (512.03.C)

The sealer needs to be stored in a location where the temperature stays within the manufacturer’s recommended range. It should not be stored in direct sun light or allowed to freeze. A thermometer should be provided by the Contractor. Do not use material beyond its shelf life.

Surface Condition (512.03.E)

Improper surface preparation is one of the main reason we see sealer failures. When the sealer is applied to a damp, dusty, or laitance laden surface, the sealer cannot gain the proper adhesion and will peel off, normally in sheets.

Figure 512.C – Sealers not Properly Bonded

All surfaces must be cleaned of dust, dirt, oil, grease, wax, curing compounds, efflorescence, laitance, coatings, and other foreign materials. All unsound areas should be repaired prior to surface profiling. Patched areas should air dry for ten days prior to sealer application. All concrete should attain its 28 day strength prior to sealer application. Do not apply sealer to joint sealants that have not cured to the manufacturers’ instructions. Check for dust contamination prior to applying the sealer.

Surface Preparation (512.03.F)

The purposes of surface preparation are to remove dust, dirt, oil, grease, wax, curing compounds, efflorescence, laitance, coatings and other foreign materials from the concrete surface and to leave the concrete with an open, absorptive surface, exposing the sand matrix of the concrete. The concrete surface which is to be sealed should look and feel like 100 grit sandpaper or coarser (surface profile). An inadequate surface profile will not provide the anchor pattern needed for proper bonding. The Contractor is required to supply 100 grit sandpaper for comparison.

If the concrete surface had curing compound applied, the surface must be acid tested after blasting to check if the curing compound was completely removed. Perform the acid test for every 500 square feet.

1. Use a solution of one part 20 degrees Baume muriatic acid and two parts water.

2. Apply four to five drops to the concrete surface. (If foaming/fizzing occurs, the curing compound was removed).

3. If foaming/fizzing does not occur, use products approved by the sealer manufacturer to remove the curing compound.

4. Rinse the tested location with an ammonia solution to neutralize the concrete surface.

The manufacturers of the sealer materials recommend the complete removal of existing coatings from the concrete in order for their sealer to adhere to the concrete.

There is now a separate pay item for the removal of existing coatings.

Figure 512.D – Right Side of Barrier Properly Prepared

Figure 512.E – Barrier after Surface Preparation

Surface preparation of concrete surfaces can be done by water, abrasive blasting, or a combination of both.

Water blast at a 7,000 psi minimum. The blasting equipment should have a gauge to verify the pressure.

Abrasive blasting needs to be followed by air brooming or power sweeping to remove dust and abrasive from the surface of the opened pores.

Ensure all wastes from the surface preparation operation are managed in accordance with C&MS 107.19. The Contractor must control fugitive dust and waste water. They must contain, collect, and properly dispose of all wastes.

Figure 512.F – Containment for Blasting Debris Waste

Make sure the Contractor is standing a reasonable distance away from the surface being blasted, typically 18 inches. Using a 7,000 psi water blast from 6 feet away does not gain the level of cleanliness needed to correctly apply the sealer.

Figure 512.G – Combination Water/Abrasive Blaster

Figure 512.H – Abrasive Blaster

Application and Coverage (512.03.G)

If using water blasting methods, the Contractor must apply the sealer between 12 and 48 hours after surface preparation.

If using abrasive blasting methods, the Contractor must apply the sealer within 48 hours after surface preparation.

There must be no rain within 6 hours of sealer application. The ambient temperature must be above 50 ºF within 6 hours of sealer application. Time between coats shall meet manufacturer’s written recommendations. Sealer must be applied at the approved coverage rate in a continuous, unbroken film.

Epoxy-Urethane Sealers (512.03.G.1)

Epoxy-Urethane sealers must be applied at the approved application rates listed on the Qualified Product List (QPL) listed on the Office of Materials Management’s (OMM) website. Application rate for Epoxy is 120 square feet per gallon (150 square feet per gallon if authorized), for Urethane, it is 200 square feet per gallon. Application rates for sealers will vary for form liner surfaces. Application areas should be marked to confirm coverage rates.

For sealed sidewalks, or other non-skid horizontal surfaces, sand is broadcast and the sealer backrolled to encapsulate the sand.

Sags, runs, drips, holidays, and discolorations are not acceptable.

Non-epoxy sealers (512.03.G.2)

Non-Epoxy sealers must be applied at the manufacturer’s recommended mode of application. Do not apply non-epoxy sealer if the ambient temperature is below 40 ºF or will fall below 32 ºF within 12 hours after application. Application rate for Non-Epoxy is 100 square feet per gallon for decks and sidewalks, 125 square feet per gallon on vertical surfaces, and 150 square feet per gallon on parapets, abutments, pier caps and median dividers.

These sealers are clear by nature, but are to be tinted with a vanishing dye; therefore, it will be difficult to see where progress ended on the preceding day. Establish a method to mark the stop point that will not permanently be visible in the completed work.

Test Site/Application (512.03.H)

Ensure that test sites include a variety of surfaces: horizontal, vertical, inverted, steel formed finish, troweled, floated, rubbed, etc.

Sealing Concrete Bridge Decks with HMWM Resin (512.04)

HMWM stands for High Molecular Weight Methacrylate.

If the Contractor supplies 3-part HWWM, which means the promoter, resin, and initiator are supplied separately, be aware that the promoter and initiator will react violently with each other. This chemical reaction is so violent that these components normally arrive to the job site on different trucks.

Poor surface cleanliness is a major problem encountered in the field. Dust and debris clog up the cracks and do not allow the HMWM to penetrate effectively. The temperatures of the concrete surface to be treated must be the range from 50 ºF to 120 ºF. Do not apply the HMWM resin within 24 hours after rain or when rain is forecast within 12 hours of application. The application rate should be approximately 100 square feet per gallon.

Be sure to insist that the Contractor coordinate his initial application on the project with the presence of a manufacturer’s representative. This representative should be a technical representative in lieu of a sales representative.

The application of sand is required to give the sealed surface a rough texture to assist with traction. If the sand is applied after the resin begins to harden, it will not become embedded and will merely brush off with the first wave of traffic leaving a potentially slick surface.

Traffic should not be permitted on the treated deck until it is tack free for a minimum of 6 hours.

There is a Qualified Product List (QPL) for this material which is maintained by the Office of Materials Management (OMM) located under 705.15.

Soluble Reactive Silicate (SRS) Concrete Treatment (512.05)

Proper surface preparation is essential for SRS to perform properly. The manufacturer’s representative must be on-site and sign off that the surface preparation is adequate.

The Contractor is required to perform a test section(s). This section(s) should incorporate all of the surface types to be treated, since test sections are to confirm application rates and appearance which will depend on the orientation and porosity of the concrete.

The temperature of the concrete surface to be treated must be above 35 ºF.

After the treatment has cured, and prior to opening to traffic, the treated surfaces that experience vehicular or pedestrian traffic should be washed down with water. In some instances, the SRS treated surfaces have become very slick when first exposed to water. It is better to have this initial exposure in a controlled scenario versus allowing the first water exposure to the surface, such as rain, occur with traffic running on it.

There is a Qualified Product List (QPL) for this material which is maintained by the Office of Materials Management (OMM) located under 705.24.

Treating Concrete Bridge Decks with Gravity-Fed Resin (512.06)

Proper surface preparation is essential for Gravity Fed Resin to perform properly. Remove all dirt and debris and all traces of asphalt or petroleum products from the deck to be treated.

The temperatures of the concrete surface to be treated must be the range from 40 ºF to 100 ºF. Do not apply the Gravity Fed resin within 24 hours after rain or when rain is forecast within 12 hours of application. The application rate should be approximately 100 to 150 square feet per gallon.

Broadcast sand over the sealed areas of the bridge deck by mechanical means.

Traffic should not be permitted on the treated deck until it is tack free for a minimum of 6 hours.

There is a Qualified Product List (QPL) for this material which is maintained by the Office of Materials Management (OMM) located under 705.25.

Sealing Cracks by Epoxy Injection (512.07)

Epoxy Injection is a process to repair cracks or fractures in reinforced concrete that are 2 to 100 miles wide. Make sure the requirement for the presence of the manufacturer’s representative is enforced even if the Contractor has vast experience with this feature of work.

Note: The Contractor may refer to the injection ports as “straws.”

The Contractor must establish injection procedures and the depths and spacing of holes at injection ports or tees. The Contractor must remove the injection ports or tees flush with the concrete surface after the fracture has been filled and the epoxy has cured. Take core samples as soon as the epoxy has cured. This is more critical on large jobs as the method of epoxy injection may have to be altered if it is not achieving adequate penetration. On small, one-day type jobs, this will not be possible.

There is a Qualified Product List (QPL) for this material which is maintained by the Office of Materials Management (OMM) located under 705.26.

Waterproofing (512.08)

Waterproofing material is applied on vertical and horizontal concrete surfaces. The waterproofing needs to be applied carefully to adhere to the concrete surfaces. Care should be taken while placing backfill or paving against and over areas that have received waterproofing. The waterproofing can be damaged by either direct contact of the equipment or by use of backfill materials which contain large sharp edged rocks. Do not apply waterproofing fabric or membranes over attachments and hardware. Seal the discontinuities with asphalt per C&MS 702.06 or hot applied joint sealer per C&MS 705.04.

Follow the manufacturer’s recommendations for the application of prime coats, (rate of 0.10 to 0.20 gallon per square yard), prior to the application of fabric types, A, B, or C waterproofing. Follow the manufacturer’s recommendations for the application of the Types 2 and 3 membrane waterproofing.

If asphalt pavement is to be placed directly over the water proofing membrane, the Contractor must first apply tack coat as specified in C&MS 407 without damaging the membrane.

There are Qualified Product Lists (QPL) for the membrane and fabric materials which are maintained by the Office of Materials Management (OMM) located under 711.24, 711.25, and 711.29.

Documentation Requirements – 512 Treating Concrete

1. General.

a. Document type of material used (make and model).

b. Quantity of material used and application rate.

c. Area treated or sealed in square yards and/or lineal feet of crack repaired.

d. Contact information for manufacturer’s representative that is on-site (where required).

e. Atmospheric conditions and substrate temperatures.

2. Sealing of Concrete Surfaces (512.03) (Use CA-S-21- Sealing of Concrete Surfaces Checklist Form).

a. Copy of Superintendent’s Work Type 57 – Sealing of Concrete Surfaces certificate (class taken within last 4 years).

b. Material Safety Data Sheet and application data from Sealer Manufacturer.

c. Proper equipment for surface preparation (7,000 psi minimum water blaster).

d. Concrete surface clean and free of all contaminants.

e. 100 grit sandpaper for surface preparation comparison.

f. Containment for blasting waste water and debris.

g. While stored, sealer not exposed to sun or frozen.

h. Proper mixing equipment.

i. Document atmospheric conditions and temperatures.

j. Check application coverage and rates. Document quantity of material used.

3. Waterproofing (512.08).

a. All surfaces clean and dry prior to placing waterproofing.

i. Type A, B, and D.

1. Amount of primer used.

2. Temperature of bituminous material.

3. Document amount of bituminous required and amount used.

4. Document lap of fabric.

ii. Type 2 and 3 membrane.

1. Temperature at time of application.

2. Document lap of membrane.

3. Type 3 surface joints sealed.