Core testing methods for evaluating concrete: The following are some of the more common tests that are to be performed or offered to the customer by the applicator prior to the preparation of the slab for any given project. These tests require a sample, (drilled core), be taken and sent to a testing laboratory for analysis.
1. Infrared spectroscopy analysis: This test checks the sample for organic contaminates in the concrete such as hydrocarbons, oils, fats, etc. This is a test that is recommended for all coatings applications and is inexpensive.
2. Ion chromatography analysis: This test is primarily used to check the concrete cap for silicates from curing or hardening agents applied to the slab after it was poured. If these silicates are not identified and a coating is applied, the silicates act as a bond breaker and the coating will delaminate from the substrate. This is a very inexpensive, but critical test, and should be offered in all projects where it is not known weather the concrete contractor used an after-pour treatment.
3. X-ray diffraction (XRD): This test is to determine the inorganic makeup of the concrete. The results of this test are used to determine any deleterious constituents in the concrete and will give the applicator warning of potential problems. He can then plan a strategy of alternative coatings or restoration procedures to remedy the problem. This test is also recommended for all coating projects.
4. Energy Dispersive X-Ray (EDXA): Determines mineralogical composition of the concrete cap and usually used in conjunction with the XRD.
5. Thin Section Petrographic analysis: (ASR analysis). This test is usually performed on older concrete slabs to check for ASR (Alkali Silica Reaction) activity. ASR is not common to the entire USA but seems to be found in certain areas only, primarily the aggregate used in a particular pour of concrete. The culprits are fossilized aggregates which are unique to these areas. When it does occur it is a very destructive process that will deteriorate both the concrete and any coating system applied to it. However there are physical signs of this activity that manifest on the surface of a given slab undergoing active ASR. The applicator should become knowledgeable enough on this subject to be able to at least recognize some of these signs and then recommend that testing be done to determine if ASR is present. This test is not a commonly performed test, but ASR is being found in more and more slabs, (in the effected regions), as professionals become more aware of the symptoms and causes of ASR. This is usually a more expensive and thorough test procedure and not usually recommended for every project.
In most cases the test sample for these tests will be a drilled core sample. These are usually 3" in diameter by 2",(called a 3X2), or through the entire slab depending on what is being checked. A 3"X 2" core is the usual size required unless the lab requests a deeper core for further testing. As far as cost is concerned, the cost of performing these tests on 3 or 4 core samples is very small compared to all the possible costs involved in a coating failure down the road. Usually the facility owner will pay for these tests to be performed but, if not, this is a relatively inexpensive insurance policy that will go a long way to assuring a more successful job.
There are many private-testing laboratories located around the country that can handle concrete sample and core testing. The following two labs are ones Koester America can recommend when sending samples and cores. They are quick, inexpensive and very knowledgeable of concrete and the coatings industry. Some of these are:
Mineralogy, Inc. 3228 E. 15th St. , Tulsa, OK 74104-5252 Phone: 800-804-7788.
Materials and Process Solutions, Inc. Golden, CO Phone: 303-277-1941
Both these labs are very knowledgeable
in concrete moisture problems, from simple vapor and PH transmission to ASR and cellular level moisture/gel chemical activity
of concrete and aggregates. Both of these labs current ASTM testing practices and procedures offer all the necessary testing
that the applicator may need to provide both preventive, (pro-active), and forensic, (after the fact), testing for future
jobs or problems with existing or past flooring projects.
Enter supporting content here