concrete coatings

The NTPEP Concrete Coatings and Sealers Evaluation Program

The National Transportation Product Evaluation Program (NTPEP) is a public-private partnership that prevents duplication of efforts among the 52 state departments of transportation. NTPEP provides product evaluations and facility audits for different products used in the transportation industry ranging from asphalt release agents to geotextiles. The product evaluation portion of the program provides single-source testing of common products used by state DOTs manufactured to AASHTO standards. One of the newer programs within NTPEP is a standardized evaluation for the performance of concrete coatings and sealers (CCS). This article provides the history and improvements made to the program since its inception, and an overview of the newly revised testing protocol.

As seen in the January 2020 Edition of the Journal of Protective Coatings and Linings (JPCL) and on Paintsquare.com

THE HISTORY OF THE PROGRAM

The CCS program began evaluating products in 2014. Ongoing concerns during technical committee calls and discussions at the annual meetings prompted the committee to review the Project Work Plan in 2016. The Project Work Plan is a consensus-based document and includes peer review and input from industry experts; it is the basis for host states to conduct their testing and evaluation. The primary reasons for the review included inquiries from states to add concrete sealers and antigraffiti coatings to the program, as well as issues experienced by the testing lab with the concrete mix design and test specimens deteriorating during testing.

The CCS technical committee formed a task force to review the Project Work Plan and research the best practices in the field of concrete coating and sealer evaluation. Among those surveyed during this effort were SSPC, industry partners and state DOTs. States were also asked about their needs in the area of concrete coatings and sealers. The test lab for the evaluations performed in 2014–2016 was contacted to discuss issues with the Project Work Plan and recommend any improvements. In addition, industry was approached to determine the relevant testing performed by the manufacturers to determine coating and sealer performance.

Photo courtesy of KTA-Tator, Inc.

The task force found that AASHTO TP 96, “Standard Method of Test for Protective Sealers for Portland Cement Concrete,” was successfully being used by other agencies to evaluate concrete coatings and sealers. AASHTO TP 96 was replaced in 2019 by AASHTO T 384, “Standard Method of Test for Protective Sealers for Portland Cement Concrete.” In addition, other agencies have in-house test methods that include freeze-thaw and scaling resistance as well as a chloride-ion-penetration testing. The in-house methods were found to be very similar in nature to the AASHTO TP 96 procedures.

The issue with antigraffiti coatings is the challenge of testing the coating’s performance as it relates to the ability to repel graffiti or remove graffiti. The task force opted to focus efforts on the sealer and coating testing and hopes to add antigraffiti coating performance testing in later iterations.

The key concepts that the task force needed to address in the revision of the Project Work Plan were to find a freeze-thaw-stable mix design, fabricate standardized-sized prisms for testing procedures and combine those two elements to prepare a sample specimen that would hold up to the rigors of the testing and allow the performance of the coating or sealer to be evaluated—not the quality of the concrete and/or the weakness of the specimen fabricated.

DEVELOPMENT OF THE NEW PROJECT WORK PLAN

The task force chose to use AASHTO TP 96 as the backbone of the new concrete coatings and sealers Project Work Plan. Due to its successful use by other agencies, it was considered a tried-and-tested methodology from which to build the new Project Work Plan. TP 96 classifies sealers into two types: film-forming (coatings that remain on the surface of the concrete) and penetrating materials that enter the concrete to some measurable depth. The program was formerly called “Concrete Coating Systems,” but with the introduction of concrete sealers to the program, it is now called “Concrete Coatings and Sealers.” The Project Work Plan includes coating systems that can be applied individually or as a system of multiple coatings.

TP 96 includes the following testing protocol:

  • Sealer characterization;
  • Water-vapor transmission;
  • Saltwater absorption;
  • Chloride permeability;
  • Sealer penetration depth or coating thickness;
  • UV weathering and cyclic saltwater ponding; and
  • Resistance to alkali.

Concrete coatings and sealers are intended to provide the universal properties of reducing water and chloride ion penetration, extend the service life of concrete and be resistant to traffic wear and the various environmental conditions to which the concrete coatings and sealers may be exposed. The task force was made aware of industry concerns regarding the quantity of tests performed and the relevance of those tests to expected field performance. The task force attempted to streamline the testing to focus on the most relevant tests. The streamlining of the Project Work Plan reduced the testing time and lowered the overall cost of the program.

The task force reviewed manufacturers’ technical data sheets (TDSs) for a variety of different materials that fall under the concrete coating and sealer categories to identify the test methods routinely used and reported. The task force cross-referenced many of those typical methods found on the TDSs with TP 96, and many of the same ASTM and AASHTO methods were employed. This further substantiated the move to AASHTO TP 96 as the backbone of the new CCS Project Work Plan. After extensive research and review, the task force identified the following goals and moved forward to:

  • Rewrite the current CCS Project Work Plan;
  • Use AASHTO TP 96 as the backbone;
  • Standardize the concrete mix design;
  • Standardize the test prisms; and
  • Work with industry, states and testing labs to review and edit.

The Current Project Work Plan

The current CCS Project Work Plan can be found at the NTPEP website: bit.ly/2RkWXoi. The Project Work Plan has eight sections. The first four include the Introduction and Scope, Referenced Documents, Terminology and Program Overview.

Section 5, Coating Identification Testing, begins the technical aspects of the program (Table 1). This section outlines the testing performed by the manufacturer and the test facility. The testing is separated by generic category of product: concrete sealers and concrete coatings.

Table 1: Coating Identification Testing.

Section 6, Performance Tests (to be performed by the testing facility) includes the heart of the program where agencies will gain the most value (Table 2). This group of performance tests includes standardized procedures used to evaluate concrete coatings and sealers.

Table 2: Performance Testing.

Section 7, Test Specimen Requirements, is a key update to the Project Work Plan. This section improves upon the mix design guidelines and provides a concrete mix that can withstand the testing extremes. It also now utilizes standardized specimen sizes known to perform well under the test conditions.

Table 3 outlines the mix design guidelines found in TP 96. During the task force research, survey responses indicated that agencies using these guidelines were able to produce a concrete mix that successfully held up to the testing conditions. These guidelines were reviewed by other agencies with freeze-thaw-tolerant mixes and found to be similar. The task force decided to move forward with these guidelines. 

Table 3: Panel Preparation Requirements.

Section 8, Testing Protocol, provides the application procedure, the tests to be performed, the type of specimens, number of tests and duration of the tests. The Project Work Plan uses tables instead of descriptions to summarize the details and provide clear, concise direction. Specimen types include:

  • Cubes (4 inches square). MVT, waterproofing, chloride, coating thickness, dry time;
  • Slabs (4-by-6-by-2 inches). Adhesion, immersion, skid resistance, UV; and
  • Prisms (16-by-3-by-4 inches). Freeze-thaw.

Three specimens are fabricated for each test. The surfaces are lightly blasted to remove loose or friable material. The samples are blown-off with clean compressed air, and the moisture content is adjusted to 50% for slabs and prisms, and 70% for cubes. Coatings are applied according to the manufacturer’s instructions to all sides of the specimens. Sealers are applied by immersion or brush and coatings are applied by airless spray with tip sizes, pressure and hose length recorded. Successive coating layers are applied at the minimum recoat time.

The dry-film thickness is then measured per ASTM D6132, “Standard Test Method for Nondestructive Measurement of Dry Film Thickness of Applied Organic Coatings Using an Ultrasonic Coating Thickness Gauge,” for coatings, and coated samples are cured for 30–45 days at 25 C and 50% RH unless otherwise required by a specific test. Specimens are photographed prior to testing.

An entire submission requires 32 weeks for coatings and 29 weeks for sealers. Testing data and results are maintained in an online database, NTPEP DataMine: data.ntpep.org. Access to restricted data in DataMine requires a login; public data does not. Vendor data is kept confidential between vendors. DOTs have access to all data. When implemented by state DOTs, their own state standard specifications may supersede the NTPEP Project Work Plan. Industry is advised that state-level requirements may supersede basic NTPEP testing. Manufacturers can find information on testing fees at NTPEP’s website, and can contact Vince Glick (vglick@aashto.org) if interested in submitting a product.

CONCLUSION

The request for a standardized, one-stop shop for evaluating concrete coatings and sealers has been fulfilled. This new Project Work Plan includes current best practices (AASHTO TP 96) and has been used successfully by agencies since 2013. Industry has been a part of this review and revision and concerns with the former Project Work Plan have been addressed. Now is the time to implement the new CCS program. The benefit to manufacturers is that they have one place to send material for evaluation and those results can be shared via DataMine by agencies to compare to their own specifications and verify compliance. The benefit to agencies is the ability to have a clearinghouse of testing data, gathered using standardized test methods on materials widely used in construction and maintenance. The next step is for agencies to begin requiring the CCS NTPEP program and to recommend use of this program to concrete coating and sealer manufacturers. The product submission cycle is now open to manufacturers.

The Concrete Coatings and Sealers NTPEP technical committee follows and can be accessed at bit.ly/2PcTcia: Chair: Todd Bennett, MODOT; Vice-Chair: Kelly Morse, ILDOT; Vice-Chair: Francisco Guidiel, LADOT; NTPEP Liaison: Vince Glick, AASHTO and Testing Laboratory: KTA-Tator, Carly McGee.

ABOUT THE AUTHORS

Carly McGee is the Technical Manager of the Physical Laboratory for KTA-Tator, Inc. where she has been employed since 2001. She is an SSPC-certified Protective Coatings Specialist, a member of the Pittsburgh chapter of the American Concrete Institute (ACI), an ACI-certified Concrete Field Testing Technician Grade 1, a member of ASTM Committees G01 (Corrosion of Metals) and C09 (Concrete and Concrete Aggregates), and a Director for the Research Council on Structural Connections.

Kelly Morse is Chief Chemist for the Illinois Department of Transportation, Bureau of Materials. She has 25 years of experience working as a chemist in the Chemical Test Unit of IDOT’s Central Bureau of Materials. Morse actively participates with AASHTO and NTPEP as the Vice Chair of the Concrete Coatings and High Friction Thin Overlay committees. She is Chair or Co-Chair of various national- and state-sponsored research projects on a wide range of highway construction and maintenance materials.

Todd Bennett is the Chemical Laboratory Director for the Missouri Department of Transportation. He currently serves as the Midwest Region III Representative for the Steering Committee of NTPEP, and Technical Committee Chair for the Structural Steel and Concrete Coatings Committees of NTPEP. He is an SSPC-certified Bridge Coatings Inspector and a NACE Coating Inspector, Level II. Bennett holds a B.S. in chemistry from Missouri State University.

Since joining AASHTO in 2015, Vince Glick’s background in program management and supply-chain analysis has defined his current role as the top requirements analyst for NTPEP DataMine development/deployment. A graduate of Virginia Tech with a Bachelor of Science in Apparel and Textile Manufacturing, he is the liaison for the Structural Steel Coatings/Concrete Coating Systems (SSC/CCS), PCC Joint Sealants (JS) and Hot Mix Asphalt Crack Sealant (CS) and Geosynthetics (GTX & REGEO) AASHTO NTPEP Technical Service Committees. 

Leave a Reply

Your email address will not be published. Required fields are marked *