NJDOT Project I-280 Retaining Wall

Demonstration Project

 The geopolymer-based coating CeramycShieldTM was used for a demonstration project with the New Jersey Department of Transportation (NJDOT) on Route I-280 at Garden State Parkway, South Orange, New Jersey in May 2008.

The major steps of application procedure were:

  1. The surface was cleaned by pressure washing the concrete.
  2. The coating material was mixed in the field and applied using a roller and brush. The application process of the coating is shown in Figure 1.
  3. The finished wall and a picture taken after 5 Years are shown in Figures 2 and 3.
  4. This same wall is shown in image 5 and 6 after 10 years.

Key Problem Elements

  1. Proper maintenance of concrete provides extended life and good aesthetic appearance. As the concrete ages, maintaining the structures built with concrete (e.g. bridges, tunnels, buildings, dams) becomes expensive and time-consuming.
  2. It is well known that the best way to protect concrete structures is to prevent water, chemical, and chloride ingress that starts the carbonation and subsequent deterioration process.
  3. Further, external sources of sulfates in soil and water can cause sulfate attack, leading to the deterioration of in-ground and sub-grade concrete assets.
  4. Liquid ingress can be reduced considerably with a coating. However, this coating should allow vapor pressure release for it to be durable, and also preserve steel reinforcement.
  5. Inorganic pigments should be used that do not fade with UV exposure
  6. Photocatalytic properties will deter biological growth

Solution: Geopolymer-based Ceramic Surface Treatment – CeramycShieldTM

  1. Use a thin inorganic geopolymer-based Ceramic Surface Treatment (CST) that prevents the ingress of chemicals that will deteriorate concrete while also allowing water vapor pressure release.
  2. Create a durable coating that is chemically compatible with concrete.

The cementing part of the coating to be used, called geopolymer, was originally developed as a bulk mortar and subsequently modified for use as a coating material for concrete and cementitious surfaces. The cementing part is a potassium alumina-silicate, or polysialate-silox with the general chemical structure:

Kn { – ( SiO2 z – AlO2 )n } ·wH2O

The resin hardens to an amorphous (glassy) structure at moderate temperatures of 55 to 85°F. Hardeners have been developed to obtain a room temperature cure in 24 hours or less.

The unique features of the CeramycShield are as follows:

  1. The resin is prepared by mixing a liquid component with silica powder. Fillers and hardening agents can be added to the powder component. The components can be mixed to a paint consistency.
  2. Common application procedures such as brushing and spraying can be used for the application.
  3. All of the components are non-toxic, and no fumes are emitted during mixing or curing.
  4. Since the matrix is water-based, tools and spills can be cleaned with water.
  5. The excess material or material removed from the old application can be discarded as general waste.

Performance After 10 Years

The coating was monitored for 10 years to assess the long-term performance. The pictures taken after 10 years are shown in Figures 5 and 6.

  1. The coating has performed very well and looks substantially similar to the day it was coated.
  2. The pigmented “brick wall” appearance shows no fading or deterioration from exposure after 10 years of UV sunlight radiation.
  3. Concrete and coating surface shows no deterioration from exposure to weathering, freeze-thaw, or carbonic acids in rain.
  4. The surface of the concrete wall and coating show no deterioration from salts and other deicing chemicals used in winter months.
  5. The surface is void of biological growth (e.g., algae, fungi) common to other concrete surfaces in the area.

Side note: The wall was scraped by semi-trucks at 2 locations, and pieces of the wall at the surfaces were broken off. Even in the edges of the impact locations, the coating did not tear, delaminate or otherwise deteriorate form the concrete surface. A piece of the broken wall is shown in Figure 4.

Conclusion

The surface of the wall was coated successfully in real-world field conditions and has shown excellent performance for 10 years.  There are no signs of spalling, cracking or other deterioration from carbonating related to atmospheric exposure.