Purpose of Asphaltic Bitumastic Coating on Manholes
Purpose of Asphaltic Bitumastic Coating on Manholes
(OP)
Quick question for some of you experienced engineers out there.
What is the purpose of asphalt bitumastic coatings on manholes? In my experience, I've noticed that this coating is only specified on sanitary sewer manholes, and typically not on storm sewer manholes. This leads me to believe that the reason for this is because the coating adds an extra level of seal protection from having septic substances mixing with ground water. Does anyone have any ideas regarding this? I practice primarily in NY.
Thanks in advance.
What is the purpose of asphalt bitumastic coatings on manholes? In my experience, I've noticed that this coating is only specified on sanitary sewer manholes, and typically not on storm sewer manholes. This leads me to believe that the reason for this is because the coating adds an extra level of seal protection from having septic substances mixing with ground water. Does anyone have any ideas regarding this? I practice primarily in NY.
Thanks in advance.





RE: Purpose of Asphaltic Bitumastic Coating on Manholes
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
Thanks again.
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
coating onto the manhole. These coatings come in different types: spray-on cementitious, epoxy, or polyurethane; shrink-wrap plastic; and/or adhesive rubber tapes.
The exterior coatings are mainly for water proofing although ther may be some conditions where the soil is corrosive. Another water proofing consideration is that the concrete may crack and the exterior coating is considered more flexible than the concrete which should allow the coating to seal the crack somewhat.
Bitumastic is also used with concrete plugs to seal the lift holes on precast elements.
Some utilities also do not use coatings on the exterior of the manholes.
In addition, coatings such as coal-tar epoxies have a history of poor performance where hydrogen sulfide attack can occur. PVC or HDPE liners are more effective.
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
Waterproofing and joint sealing is usually only required on sanitary manholes and generally on the interior only. This is preferable because the hydrogen sulfide is on the inside of the manhole and the inside can also be inspected and re-coated if necessary. Waterproofing the outside with bituminous coating to prevent infiltration of groundwater would be minimally effective at best.
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
Corrosion experts have moved away from specifying interior bitumastic linings because of the historically poor performance. The best option for corrosion protection where you know hydrogen sulfide to be present is internal linings made from HDPE, PVC, FRP, etc.
Concrete is not a water proof material and concrete may crack. That is one of the reasons that the bitumastic is specified on the manhole exterior. This is especially true in areas with high groundwater. A similar asphalt-based coating is used on foundation walls of houses for the same reason, waterproofing.
In addition, if you are in a marine environment, seawater submergence conditions, or estuarine areas, the effect of elevated sulfate and chloride concentrations should be carefully considered. High sulfate concentrations will spall concrete, while chlorides will penetrate through the concrete and induce accelerated corrosion of reinforced steel.
Bitumastic is also used for spot sealing repairs on the exterior of manholes.
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
Coating a manhole on the inside is to protect the concrete from direct attack by sulphates in the wastewater and to reduce the incidence of permeation of the concrete to the rebar levels. Since the rebar is closer to the outside, this is less of an issue than the attack on the concrete matrix itself.
When you use asphaltic coatings, remember that the concrete must be primed before the asphalt mastic or coating. If you are using a coal tar based material (Bitumastic for instance) you do not need to prime the concrete before application.
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
RE: Purpose of Asphaltic Bitumastic Coating on Manholes
AWWA C-210-92 for exterior
SSPC-Paint 16
Most specifications are require manhole waterproofing not protection of steel reinforcement. Here are examples:
3.2.7 Manholes – Bitumastic Coatings
A. The entire exterior surface of all masonry and concrete (whether precast or cast-in-place) structures associated with sewerage systems, such as: manholes, grease traps, holding tanks, tight tanks, septic tanks, aeration tanks, pump stations, valve pits, etc., shall receive two coats of
waterproofing such as Carboline Bitumastic 300M as manufactured by SOMAY Products, Inc., Miami, FL; Sonnoshield HLM 5000 as manufactured by Sonneborn, Shakopee, MN at a minimum thickness of 7 mils per coat and a total thickness of 14 mils; however, in no case shall the
thickness per coat be less than that recommended by the manufacturer.
Bitumastic is a century-old trade name that is often associated with long-term protection from water penetration. Typically made from coal tars and blends of resins such as epoxy, these products have been used as tank linings, to coat the interior and exterior of buried pipe, and to protect equipment subjected to water immersion.
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E. Waterproofing:
1. Apply coal-tar coating to exterior walls on all manholes from base to finish grade:
a. Carboline - Bitumastic 300M.
b. International - Intertuf 100.
c. Tnemec - HB Tnemecol 46-465.
2. Apply coating in two coats to minimum 0.3 mm (12-mil) dry-film thickness per coat.
19. Exterior waterproof coating: Manholes shall receive a two coat application of Koppers Super Service Black waterproof bitumastic coating or approved equal.
3. Manholes shall have a water proof Bituminous Coating on the exterior & interior. Koppers bitumastic black solution 300M, or Proco EP-214.
N. The exterior surfaces of all Precast Concrete Manhole Barrel Sections shall be waterproofed. Waterproof coating shall be two coats bitomastic material or