What Is Necessary For Manhole Rehabilitation Success? Correct Application, Use Of Manhole Rehab Technologies

By Gerhard “Gerry” P. Muenchmeyer, P.E., NASSCO Technical Director | October 2011, Vol. 66 No. 10

Haessig: Surface preparation is a very important part of the process in order to have a successful installation or application. The level of surface preparation for our chimney seal is dependent on the age, condition and type of construction used for any given manhole. Upper and lower sealing surfaces must be reasonably smooth, circular and free of any loose material or excessive voids. Surface preparation will generally require wire brushing the lower three inches of the manhole frame casing to remove any loose rust or scale. If the seal is to be installed in a brick manhole, the surface of the brick will require the use of a non-shrink, polymer modified repair mortar. On precast manholes, form offsets and any excess honeycombing in the area that the band will compress against should be repaired using the same non-shrink repair mortar to provide a uniform sealing surface on the manhole cone. If the manhole is a candidate for relining with a cementitious material, the surface area directly below the casting can be made vertical and circular by the cement applicator, which reduces or eliminates the need for additional surface preparation on the masonry.

Kiest: Surface preparation is key to allowing mechanical bonding of the thermo-set resins. All structure surfaces should be clean and free from debris. High pressure blasting, with grease dissolving additives are used to remove debris, fats, oils, and grease.

Johnson: As with all spray applied resin chemistries, a clean dry substrate is best. Generally this is done by high pressure power washing with water and/or degreasing agents, if needed. The wash should expose good, stable (i.e. no corrosion byproduct) substrate. Sometimes at this stage dry, hot air is blown into the structure to enhance drying.

Warren: Surface preparation is very important. High-pressure water blasting with a diluted solution of HCL and/or detergent, followed by correction of the surface pH is recommended for brick and concrete substrates.

One of the key properties of each coating and lining system, is the ability to chemically bond, mechanically bond or not bond at all to the existing structure. Both types of products are used in the industry to rehabilitate manholes.

Does your product bond to a host structure, or does it form a structure within a structure?

Shook: Cor+Gard, is a coating that adheres well to the properly prepared substrate. Permacast and Cor+Roc structurally reinforce the existing manhole to which it bonds. The Permaform system is a totally independent structure within the old one.

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