Masonry Magazine August 2000 Page. 7
PRESIDENT'S MESSAGE
by Richard M. Johnston,
President MCAA
Making the Grade With Testing
Education in every facet of life is becoming accepted as necessary for survival. It certainly is in order to be successful and profitable in our masonry industry. As contractors, we need to know the rules, regulations and codes (with local variations) regarding the testing and inspections of our work.
Our hope is that all the technicians sent out to do the field tests are properly trained, but in an industry that is stretching its capacity, that is not always what we get. If a test is improperly taken, the result may be an order to replace a wall at your expense when you have, in fact, done nothing wrong at all. Armed with the proper knowledge of how the mortar and grout samples should be taken, and why they could possibly show a low break, you could quite possibly save the expense and inconvenience of rebuilding a wall. Even if the field test fails, core drilling actual wall samples and testing those samples might preclude your tearing down a wall and rebuilding it. My local concrete supplier has had notice of only four or five failed test cylinders in over more than twenty years in concrete sales, but in each case consequent re-testing exonerated both the contractor and the supplier. Test samples need to be properly taken. It is also important to note that subsequent handling, transporting, storage and curing can affect the test results.
In this month's MASONRY, author Bob Nelson gives us an in depth discussion on field tests of mortar. I suggest you not only read it, but also copy and share it with your foreman. MCAA will be providing you with another chance to educate yourself and your staff by attending a seminar we have planned on this subject at our next annual convention and Masonry Showcase in Orlando next February. It is unfortunate that many building officials, and even engineers, fail to fully understand the inherent strength of masonry and all the proper design and testing criteria. This is certainly an area that our industry can do more in the way of educational opportunities. We even need to educate our customers as to what performance they should expect from our walls.
Historically, there have been cases of improper masonry installations (i.e... leaving out a portion of the rebar) which left a stigma we need to overcome. With the advent of more sophisticated seismic design, and more educated mason contractors, I believe many of these worries are behind us. We do, however, need to do all that we can to give our customers and the design community confidence that we can be trusted to provide products and workmanship that will perform consistently.
To earn this respect and deal with the code issues associated with high lift grouting, we ask our bricklayers to be diligent about providing cleanouts, using rebar positioners to preclude displacement of bars, removing mortar fins, placing all steel before grouting, sealing cleanouts, vibrating during placement and reconsolidation. If this procedure is followed, you not only should be assured of a quality project, but you will also impress the inspecting agents by proving that you know what you are doing.
Regarding mortar and grout testing, it has become even more clear that our MACS (Masonry Alliance for Codes & Standards) program is important. The Code 2000 is the MACS goal which should eliminate the fact that different areas of the country operate under different building code regulations and inspection criteria. As Bob Nelson indicates in his article, the composition and other various properties of the mortar are the controlling criteria under some code requirements, whereas in other parts of the nation, compressive strength is the primary requirement. We all base our standards on ASTM, but various parts of the country place emphasis on different sections.
Under the UBC (Unified Building Code), which is used in the west and which I am subject to, compressive testing is often the only test taken and its results govern the decisions as to whether the wall will perform adequately. Accordingly, that test then must be dependable and accurately simulate the actual mortar or grout in the wall and be subject to the same absorption rates.
A proper mortar sample is taken by spreading mortar about a half inch thick on the masonry unit as used in the wall, allowed to sit for a minute and then put into the cylinders. Likewise, proper grout samples are taken by providing a square prism space three or four inches square and twice as high formed by typical units used in the construction and lined with paper towel to prevent bonding to the units but allow the water to transfer. It is apparent that it's either proportion or compressive strength-based testing.
Having personal experience with this issue, I can't stress how important it is that you and your employees fully understand the importance of proper testing, especially if full allowable stresses are used in the structural design. Once again, we come to the same old conclusion: we are the contractor and we are the responsible party let's deal with it from a knowledge base!