Cementitious Performance Testing: Liner Thickness Verification
Cementitious Manhole Liner Thickness Verification
Many municipal owners and/or consulting engineers want to ensure that the manhole restoration contractor is providing a minimum cementitious manhole liner thickness that is in accordance with project and/or the owner's technical specifications. Fortunately, this is one QA/QC measure that is relatively easy to validate.
First, the cementitious manhole liner thickness can be easily checked during the installation phase by simply having the contractor, in the presence of the project inspector, conduct a physical depth check of the liner material immediately upon product application. The simplest means of physically verifying the liner thickness is by using a small diameter, yet sufficiently rigid wire or metal rod to penetrate the liner material. The test instrument is bent/configured (as depicted in the photographs and diagram) to scale the minimum specified liner thickness (i.e. 0.5-inches, 1-inch, etc.). The operator simply inserts the test instrument into the wet mortar at various locations and depth intervals within manhole. Test areas that do not meet the minimum specified thickness simply receive an additional application of liner material until the minimum desired thickness is achieved.
Secondly, and as an added means of validating liner thickness, the project inspector can monitor the contractor's product usage for any given manhole. Using this method, the inspector simply confirms the depth and physical dimensions of the pre-lined manhole, and then cross references this information against the contractor's product usage for any given structure. The product yield per bag is a known volume, which typically equates in actual coverage to 1 bag of product per vertical linear foot in a 48-inch diameter manhole in order to achieve a 0.5 inch liner thickness. Should the specification require a 1-inch liner thickness (same 48-inch diameter manhole), the minimum product usage requirement would simply be doubled to 2 bags of product per vertical linear fo ot of manhole depth.
Please contact your local Quadex representative for more information regarding cementitious manhole liner thickness verification..
