It is vital to choose the right approach to culvert repair no matter the budget
By Joe Royer, Ph.D.
The appropriate solution to your specific culvert repair may be a difficult answer to find, initially.
Your solution depends on the type of deterioration, the root cause of the problem, and the extent to which the failing culvert allows you to rehabilitate instead of needing a full replacement. A complete rehabilitation solution could also depend on your ability, or budget, to correct failed conditions both inside the culvert as well as at the inlet and outlet.There are several solutions to repair or rehabilitate a variety of problems seen in corrugated metal (CMP) and concrete culverts. Some solutions can be used individually to solve a specific issue, or combined to fully rehabilitate a culvert with a range of problems. Some of the most effective solutions to consider would include either a geosynthetic cementitious composite mat (GCCM) or a spray-on geopolymer mortar system due to their ease of installation, total project cost, and lack of disruption to the surrounding area. GCCMs generally function as a new wear surface for culvert inverts and as an erosion control measure for culvert surrounds, but they are not a structural repair. Spray-on geopolymer mortar systems, however, can provide structural repair options for more severe culvert conditions. Example cases and solutions are detailed below.
The use of GCCMs would be the most effective for the following problems:
- Scouring or pitting of the invert in a CMP
- Inlet or outlet erosion in all culverts
The use of a spray-on geopolymer mortar system would be the most effective for the following problems:
- Scouring or pitting of the invert in a concrete culvert
- Shape deformations in a CMP
- Joint failures or misalignments in a CMP or concrete culvert
- Cracks in a concrete pipe culvert
- Deterioration such as rebar corrosion in a concrete pipe culvert
- Complete corrosion and separation of a CMP invert
In the mid-1980s, the Federal Highway Administration (FHWA) developed a 10-point scale (nine to zero) that can be used as a guideline for assessing the condition of your culvert. In this scale, nine represents a culvert in new condition, and zero represents a totally failed culvert. From a rating of two to seven, GCCMs or spray-on geopolymer mortar systems provide acceptable solutions for culvert rehabilitation and repair, but ratings of one and zero are generally beyond repair.
For a CMP culvert that has a condition rating of six or seven, a GCCM would be a good, cost-effective repair option. These conditions are generally good to fair at the top half of the pipe, which maintains a smooth curvature, but minor flattening has occurred at the bottom of the culvert. There may be minor cracking at the bolt holes, minor joint or seam openings with the potential for backfill infiltration and minor to significant corrosion of the invert. The steel will have moderate to fairly heavy rust with slight to moderate pitting.
A culvert with a condition rating of five could use either a GCCM or spray-on geopolymer mortar system depending on budget and the extent of structural damage. A GCCM would be ideal for when the CMP has slight to moderate corrosion with heavy rust pitting and the crown is still intact. However, the geopolymer mortar system is more appropriate for the cases that include deformations or signs of structural issues.
In condition ratings of two to four, all full structural repairs are typically required and a spray-on geopolymer mortar system solution might be the most effective. These culverts will have marginal to critical distortion in their shape with flattening and other significant defects at the crown. Extensive corrosion with significant, often large, perforations or section loss could be found at the invert.
When you have determined the condition of your culvert, consider how its problems align with the capabilities of GCCMs and spray-on geopolymer mortar systems and choose an effective repair or rehabilitation method accordingly.
For questions or advice on what method is right for you, contact Milliken Infrastructure Solutions at infrastructure.milliken.com/contact-us/.
Joe Royer, PhD is currently the Development Manager for Geopolymers. Joe moved into this position after GeoTree Technologies, Inc was acquired by Milliken & Company, now part of the newly formed Milliken Infrastructure Solutions. He was the former Director of Innovation for the Performance Products Division at Milliken & Company, a role he has held since 2010. For more information, please visit infrastructure.milliken.com