Author: Lorella Angelini, Angelini Consulting Services, LLC
It is well-known that innovation represents one of the key elements for a successful bridge preservation strategy. An interesting innovation technology for bridge deck protection entails the so called healer-sealers. These are very low viscosity liquid-applied resins that penetrate by gravity into the hairline cracks and surface pores of concrete with the result of preventing infiltration of water and contamination by chlorides.
Different healer-sealer technologies are available, such as, Methyl Methacrylate (MMA), High Molecular Weight Methacrylate (HMWM ), epoxy and polyurethane. They all have in common an application method that consists in cleaning and opening the concrete surface, flooding it with the resin, and broadcasting aggregate (mainly sacrificial) before the resin starts setting. Performance properties vary between the different technologies as outlined in the snapshot information reported below. This information, which provides a general guideline about the technologies, is taken from technical data guides of a selection of brands that are present in the bridge preservation environment.
In comparison with other bridge deck protection solutions, healer-sealers are economical technologies both in terms of material and labor. This affordability should make it easy to apply healer-sealers over new decks. However, in the majority of cases, they are applied on an already contaminated deck after a few years following the completion of bridge deck construction, which in turn generally reduces their effectiveness.. For best performances, healer-sealers should also be re-applied periodically, on average every 5-10 years depending on the rate of of deck surface deterioration by traffic.
High Molecular Weight Methacrylate (HMWM)
- Viscosity: <25 cPs
- 100% solids
- Elongation: 5 – 30%
- Compressive strength: 3,000 – 8,000 psi
- Tensile strength: 500 – 1500 psi
- Aggregate should be placed within 15 – 20 minutes of resin application
- Application temperature (ambient): 50 ℉ – 100 ℉
- Traffic reopening: 4 – 8 hrs. after application (depending on ambient temperature)
- Flash Point > 200 °F
Methyl methacrylate (MMA)
- Viscosity: <5 – 10 cPs
- 100% solids
- Elongation: 4.5 – 5%
- Compressive strength: >12000 psi
- Tensile strength: > 8000 psi
- Aggregate should be placed within minutes of resin application
- Application temperature (ambient): 20℉ – 105℉ (with accelerator for low temperatures)
- Traffic reopening: 1 hr after application (depending on ambient temperature)
- Flash Point >50 °F
Very Low Viscosity Epoxy
- Viscosity: 100 cPs
- 100% solids
- Elongation: 10%
- Compressive strength: 8000 – 12000 psi
- Tensile strength: > 7000 psi
- Aggregate should be placed within 20 – 30 minutes of the resin application
- Application temperature (ambient): 40℉ – 90℉
- Traffic reopening: 6 hrs after application (depending on ambient temperature)
- Flash Point >200 °F
Ultra-Low Viscosity Epoxy
- Viscosity: 40 cPs
- 75% solids
- Elongation: 50%
- Tensile strength: 2500 psi
- Aggregate should be placed within 15 minutes of resin application
- Application temperature (ambient): > 50 ℉
- Traffic reopening: 4 hrs. after application (depending on ambient temperature)
- Flash Point: > 100 ℉
Polyurethane / Polyurethane- hybrid
- Viscosity: 12-16 cPs
- Elongation: < 10%
- Compressive strength: 3000 psi
- Tensile strength: 4500 psi
- Aggregate should be placed immediately after resin application
- Traffic reopening: 10 – 90 minutes after application (depending on ambient temperature)
- Application temperature (ambient): 20℉ – 100℉
- Flash Point : >200°F
There a number of publications and research reports about healer-sealers. Some of them include a comparison with silane sealers. A few links are reported below.
From Minnesota DOT:
http://www.dot.state.mn.us/research/TS/2014/201434.pdf
From Oregon DOT:
https://www.oregon.gov/ODOT/TD/TP_RES/docs/reports/2010/crack_sealer.pdf
From Colorado DOT:
https://www.codot.gov/programs/research/pdfs/2014/sealers.pdf/
From Kansas DOT: