Research Projects

Antimicrobial Formulations to Reduce Mold Intrusion on Airfield Markings and Pavements

The reoccurring growth of mold and continued maintenance required to prevent discoloration of airfield paint markings poses a continued problem that draws money that would otherwise be used for pavement improvements. This research will employ recent innovations in antimicrobial research to develop a quaternary ammonium compound that can be applied as a top-coat to markings and pavement surfaces whereby the modified surface will become non-leaching and exhibit contact-killing, highly-effective antimicrobial activity capable of reducing or eliminating the growth of mold on airfield safety markings and pavements.

Background (Describe the current situation or problem in the industry, and how your idea would address it.)

Recently, an increased presence of mold on airfield pavement markings has been observed throughout southern US states and poses a significant safety concern for aircraft and airfield vehicular operation. Mold of pavement markings has been noted in the Southern U.S. including the states of Florida, Georgia, and North Carolina. The FAA Headquarters, the FAA Atlantic City Technical Center, the FAA's New England, Southern and Northwest Mountain Regions, and state Departments of Transportation in New Hampshire (NH), Massachusetts, Maine, and Minnesota have all experienced staining problems. While methods of cleaning pavement markings have been performed, the growth of mold has become reoccurring at an added maintenance and operation expense for many airports. Because of the hot weather and humid environment of airports throughout Georgia and other southern US states, the intrusion of mold has resulted in the fading and discoloration of pavement markings, as a result of the mold growth, causing the potential for error when aircraft are approaching or departing the runway, navigating the taxiways, and parking. Research is needed to evaluate the current conditions leading to widespread and reoccurring growth of mold and develop innovative and real solutions to reduce or eliminate the mold from pavement markings. Because this phenomenon is not an isolated problem, the solutions and recommendations from this study will be relevant to airport owners throughout the US and beyond. Ultimately, this research will produce an immediate tangible outcome that will provide airport owners with information and a practical implementation plan on treatments for their airfield marking projects that will reduce or eliminate the growth of mold on airfield paint.

Objective (What is the desired product or result that will help the airport industry?)

The primary objective of this project is to research and develop solutions for reducing or eliminating mold growth on airfield pavement markings. The solution(s) will be such that the treatment method is effective and economical in providing clean and well-visible pavement markings while maintaining a durable and abrasion resistant surface. Outcomes of this study are expected to include a draft treatment recommendations document that will be presented for potential inclusion in FAA Advisory Circular that address identified solution(s) from this study and provide guidance to airport owners.

Approach (Describe in general terms the steps you think are needed to achieve the objective.)

First the research will investigate the cause and types of mold by performing site visits that include the sampling of materials (paint, mold, etc…) and a thorough review of the existing construction conditions with the identification of trends related to mold growth and mold-resistant products and applicability to this project. Second, the research will develop antimicrobial top-coat formulations that can be directly applied to current paints used on airfield pavements and compared with applicable current commercially available products. Laboratory test specimens of concrete will be fabricated, painted, dried, and then coated with the antimicrobial formulations using spray application from a commercial paint sprayer. The antimicrobial efficacy of the formulations as well as other products, deemed appropriate, will be performed using a variety of ASTM and AATCC methods. It is anticipated that antimicrobial coating will be transparent, but all of the optical properties of the paints will be examined (brightness, reflection, color specifications) to ensure that the coatings do not negatively affect these properties. Once the coatings have been applied to the painted test specimens, antimicrobial and friction/weathering/durability testing will be performed. The antimicrobial formulation and/or alternative formulations will be applied to both newly painted and existing/aged pavement surfaces. The objective will be to evaluate the coating's effectiveness on markings of different ages and conditions. Scanning Electron Microscope and Energy Dispersive X-Ray Spectroscopy techniques will be used to analyze paint chips with mold. The purpose of these tests is to positively identify the cause of the paint mold and continuously monitor the coating's effectiveness on markings along with time and environmental conditions.

Cost Estimate and Backup (Provide a cost estimate and support for how you arrived at the estimate.)

A budget amount of $350,000 is estimated for this study for period of 30 months. These costs include research team salary, fringe benefits, materials and supplies, travel, tuition and overhead. It is anticipated that salaries for the research team including professional (Principal Investigators) and technical (Research Assistants) to be $140,000 with fringe benefits costs of $20,000. Tuition for the graduate research assistants will be approximately $50,000 during the course of the study. Materials, supplies and equipment is estimated at $30,000 and travel to present the research findings at workshops and conferences at $10,000. The project overhead costs are estimated to be $100,000.

Related Research - List related ACRP and other industry research; describe gaps (see link to Research Roadmaps above), and describe how your idea would address these gaps. This is a critical element of a synthesis topic submission.

The FAA Advisory Circular 150-5370-10G (2016) provides an extensive list of materials and test methods (e.g., accelerated weathering, abrasion resistance, and environmental resistance) that must be used for the construction on airport runway and taxiway markings. Limited studies are conducted on pavement coating or markings. The Airfield Marking Handbook (2008) provides measurable criteria that affect the quality of airfield markings (curing compound, rust discoloration, loose and poorly bonded materials, oils, jet blast, and other contaminants, rubber deposits, and algae/mold growth). Mold or fungal growth is a common problem on concrete bridge decks when a urethane-based surface treatment is applied (NCHRP 220, 1995). It is commonly understood that mold grows on the surface of resin/paint containing organic compounds. However, limited information is available on airport pavement marking treatments. The Airfield Marking Handbook (2008) describes an algae-resistant paint formulation provided by Rohm and Haas, Inc. This product appears to provide an algae-free surface over 18 months. However, the performance of the markings beyond the observation period is unknown

Despite the commonly observed mold growth problem on airport pavement and paint markings, very little research findings address the issue of eliminating the growth of mold on the top surface of markings, particularly when utilizing the mold-resistant paint formulation. That is, there are additional factors (e.g., surface treatment/coating) that may affect the mold growth. Most paint products contain a biocide; however, the limited amount (1-5%) of a biocide in the paint formulation could also mean that most of the biocide may not be present on the surface of paint coating. A large number of commercially available paint products exist; however, few to no paint products provide solutions to eliminate or significantly reduce mold growth on the surface of pavement markings. And to date, there has been no top-coat formulation for airfield markings and pavement that can be applied directly to paint that has been studied to prevent the growth of surface molds.

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Idea No. 192