New and improved ANSI Standards

by Leigh Hightower (Technical Services Department at MAPEI Corporation)

Since the introduction of latex modification to dry-set mortars in the 1960s and drypolymer modification in the 1980s, latex Portland-cement mortars meeting the ANSI A118.4 standard have become the staples of the ceramic tile and stone industry for most applications. When these products were first introduced, they were very robust with high polymer content that could meet the needs of most installations utilizing cementitious setting materials.
Over the years, new polymers have been developed and incorporated into the formulations and, due to marketing positioning and the demand for lower-priced polymer-modified dry-set mortars, formulations exhibiting far less polymer content than the original products have entered the market. In this same time frame, ANSI A118.4 was changed by the ANSI A108 Committee, and some of the testing methods that required these materials to have high polymer content to pass the standard were dropped. This allowed products in the market to have very little polymer in them and still pass the ANSI A118.4 standard.
These circumstances made it very difficult for architects to specify polymer-modified setting materials generically using only ANSI specifications. Architects had to research and specify specific manufacturers’ products to ensure the performance characteristics they needed for a successful installation system. If architects simply specified setting materials that met ANSI A118.4, they could not be certain of getting materials that would provide a satisfactory installation.
This dilemma also made bidding the project very difficult for contractors who were trying to provide high-quality work.
If they bid on the job with high-quality setting materials, they might be bidding against an unscrupulous contractor who was bidding the least expensive ANSI A118.4 materials he or she could find; in that case, the quality contractor would probably lose the bid.

The influence of ISO 13007
A solution to this situation was provided by the development of ISO specification 13007. This international standard concentrated more on the performance characteristics of the products, and established standard and improved performance categories for all setting and grouting materials utilized in the ceramic industry. With these specifications, architects could not only specify higher quality products, but could specify specific characteristics of cementitious setting materials such as improved performance (C2), nonsag (T), fast-setting (F), and plywood bonding capability (P1 or P2).
Architects could further dictate performance by specifying the product’s transverse deformation capabilities (S1 or S2), which determine its ability to handle deflection and thermal expansion and contraction. With this method, generic specification was possible by a single group of letters and numbers such as C2TFS2, which would require an improved-performance, nonsag, fast-setting, highly deformable mortar.
Many testing procedures in the ISO 13007 standard required specialized equipment that many of the smaller U.S. manufacturers did not possess and had no access to through independent testing laboratories.
For this reason, MMSA was reluctant to promote this new ISO specification until independent labs such as TCNA obtained the proper equipment to provide testing for anyone needing it. Once the TCNA acquired the proper equipment, the MMSA recommended that the new ISO 13007 specifications be included with the ANSI specifications in the TCNA Methods. This major step was accomplished with the publication of the 2011 version of the TCNA Handbook.

A subcommittee updates ANSI
With the inclusion of the ISO 13007 standards in the TCNA Handbook, the MMSA decided that substantial changes in the ANSI specifications were needed if ANSI was to remain a credible method of specifying materials in the U.S. ceramic industry. This decision stemmed from the fact that the MMSA and TCNA can control what goes into the ANSI specifications for the United States. This is a powerful position compared to the “one vote” that the United States gets in the development of international specifications. With this in mind, the MMSA established a subcommittee to review and make changes to ANSI A118.1 Specifications for Dry-Set Portland Cement Mortar and ANSI A118.4 Specifications for Latex-Portland Cement Mortar with the intention that modifications should enable delineation of the performance characteristics of the different mortars available on the market and provide a means of specification by the architect similar to ISO specifications.

Changes in testing
A change in the open time test for all three specifications was implemented. The new open time test does two things.
First, it simulates real-world conditions by installing 2” x 2” (5 x 5 cm) tiles into mortar applied to an ISO 13007 concrete block. Tile is placed onto the setting material in five minute increments, and it is embedded by application of a 4.5-lb. (2,04-kg) weight for 30 seconds. It is not twisted 90°, as in the previous test method. After a 28-day curing period, tensile bond testing is performed on the specimens and open time is established when a minimum of 75 psi (0,52 MPa) is achieved. With this test, all mortars must have a minimum open time of 20 minutes – except for fast-setting mortars (designated with an “F”), where the minimum is reduced to 10 minutes. Extended open-time setting materials (designated with an “E”) must achieve the minimum tensile bond after the tile has been applied at 30 minutes. Second, this test is very significant because it is the first test in ANSI specifications that utilizes tensile bond testing instead of shear bonds.
The test for sag on vertical surfaces was also modified. It is now the same test that is in ISO 13007, which is a much more precise way of measuring the nonsag properties of mortars. Nonsag mortars use the designation “T.” In addition to all the standard test requirements contained in A118.1 and A118.4, a new test was developed for ANSI A118.15 that was called the 28-day heat-aging shear bond test. This test sets A118.15 apart because materials with low polymer content cannot easily pass the test. Products that have a high cement-to-sand ratio and a low polymer content could pass A118.4. With the 28 Day Heat Aging test in A118.15, these inferior products would not be able to pass the A118.15 specification. Though MAPEI personnel pushed hard to get the ISO transverse deformation testing into the ANSI specifications, this effort was met with too much resistance from a few other manufacturers. Transverse deformation testing or similar testing must be addressed at another time.
Substantial strides have been made in modifying ANSI specifications to delineate the performance characteristics of the various setting materials as well as in tightening the specifications to prevent inferior materials from passing the testing requirements. For now, there are improved ANSI A118.1 and A118.4 specifications, as well as a new ANSI A118.15 specification for improved modified dry-set cement mortars. Each of these specifications can specify special characteristics signified by applying the extensions E, F or T to the ANSI specification, such as A118.4FT.

Article source: Realtà Mapei Americas n.28/2013