The purpose of the air barrier field inspection and test procedure is to measure the adhesive strength of a material to determine whether the installation has been completed properly. In this blog post, we will dive into the why the test is important, one of the most common failures, provide the material needed for the test, and cover step-by-step on how to perform the test out in the field.
Release or separation during the test will occur along the weakest part of the material, or bond between the material and the substrate. Poor adhesion may be caused by poor substrate preparation, the surface being contaminated by water or dirt, not properly cured, or improper primer application just to name a few. For an air barrier to function properly over the service life of the building, there must be proper adhesion.
The most common cause of failures is a low/high pressure on the material over a long period of time. To determine whether proper adhesion has been achieved, on-site testing needs to be conducted. The tools and materials needed for the test include:
Magnet (min. 20 lbs. pull) with eye bolt
Scale with carabiner or locking clip (min. 20 lbs. capacity) Ultimate 54 Portable Digital Scale
1” x 1” steel coupon. Near white blast finish (free all visible oil, grease, dust, dirt, mill scale, rust, coatings, oxides, corrosion products and other foreign matter)
We recommend: Pecora XL-Flash Liquid Flashing
The basic principle is very simple – attach a 2 ¼” to 4” steel or plywood disc to the air barrier membrane, cut around the material so you are pulling on a specific area of the material. Do not damage more material around the area of the test. When attaching the adhesion tester (test dolly) to the pad adhered (adhesive) to the air barrier material (coating), ensure that the specimen is not being pre-stressed by bumping or bending. For non-horizontal surfaces, support the adhesion tester so its weight is not added to the force exerted on the sample.
You may slightly abrade the surface of the material to remove any surface film that could interfere with the adhesion to the material. Make sure you clean the abraded area with a cleaning agent as to not affect the material or leave residue. When working with our Pecora air barrier products, make sure to use a Pecora recommended cleaning agent.
Before conducting your pull test, make sure the material is fully cured. For a Pecora air barrier membrane, we suggest about 7 days. It is very important the material be flat as to achieve proper adhesion to the disk. When choosing your epoxy (adhesive) make sure it bonds to plastic to ensure it will work with a fluid applied material. Apply the adhesive to the pad and the surface of the air barrier material, removing any excess adhesive form the sides of the pad. Allow the adhesive to cure in accordance to the manufacturer’s instructions.
During the initial cure of the adhesive, apply constant pressure using either your hands or a clamping system. Do not twist or move the pad as that could result in incorrect values during testing. When a bearing ring is required, place it evenly around the pad so there is equal support being applied to the tester. TO ensure the correct amount of force is being used, apply it in a smooth continuous manner. The force shall be applied to the pay by turning the handle not more than one revolution per minute (rpm) in accordance with ASTM D4541, method B. The gauge will display the force being applied and the limit stop dial will register the peak force just before there is a separation.
Once the test is complete, you will need to analyze the material for maximum force achieved, the type of release, the surface in which the release occurred, and the percentage of release on each surface. This information should be noted in a test report using lbs. from the gauge. The pull-off value calculation is provided below.
Use table provided by test apparatus manufacturer.
In the absence of test jig calculation recommendations use the following:
Measure diameter of disc utilized.
Record lbs. force from dial indicator at failure.
Use the following calculation to determine max pull off value in PSI
Max force from dial indicator / (3.14 * (diameter/2)2 = force in PSI
Ex.: Pull off value (PSI) = Max Force (130) = 10.35 PSI pull off value 3.14 * (4/2)2
NOTE: A minimum of 16 psi is required for warranty purposes.
Any errors in the test should be examined to find its cause. If you discover that this error was caused from improper test procedures, do not include it on your report and perform another test. Any material that was damaged in the pull test needs to be replaced in accordance to the manufacturer’s instructions.
For more information on the testing procedures for our XL Perm Ultra VP, please visit the Resources section of our website and select Technical Bulletins. There you will find the two Technical Bulletins (PEC191 & PEC193) that cover this topic. Check back at the end of this month for our blog post highlighting the Barrel Yards project. We will discuss how to ensure the quality control of traffic coatings through application testing.