#MAPEITechTip: How do you know you have selected the ‘right mortar’ for the ‘right tile or stone application’?

Are all tile setting mortars the same?  If you were setting tile or stone during the Roman Empire, the answer would be yes, marble set in temples and other areas were set into a mud bed made up of sand, lime and volcanic ash.  Although the exact Roman formula was lost, modern architecture evolved to encompass a similar recipe consisting of 1 part mix of cement to 5 parts of sand that could be placed up to 2” thick on floors as a mud bed and 1 part cement 7 parts sand and 1 part lime for walls reinforces with metal lathe as render coat.  

The 1970's setting tile began to change dramatically with thin-set tile systems, dry set mortars, richer in cement than the typical mud method.  These new mortars also saw the introduction of liquid latex additives added to these dry set powders, giving them better mechanical bond and flexibility.  In the 1980's these new polymer-modified mortars were more clearly defined under the ANSI 118.4 Standard.  So from the 1970’s until today, we have seen a dramatic change from traditional 1 ¼” to 2” thick mortar beds to the new thin-set method applying the polymer-modified mortar in thickness only from 3/32” to 1/8” thick—saving time and manpower without having to site mix and the added benefits of the polymers in the thin-set applied mortars. That being said, standing in the distributors warehouse, with so many choices today—ANSI A118.1. A118.14, A118.15, ISO 13007 C1/C2/S1/S2, Dry Polymer (single component) or Liquid Latex (two-component) mortars, specialty mortars, LHTM (Large & Heavy Tile Mortars from 3/32”- 1/2”)—how do I know that I have matched the right mortar to the right application?
 
With so many mortars on the market today, it can be overwhelming in choosing a mortar that will perform within the installation environment it was designed for, ie: exterior application.  Without getting lost in all of the Standards, it basically boils down to the polymer content, now that being said, there are some additional ingredients that enhance performance, ie: thixotropic properties. 
 

There are basically two types of latex polymers that are used: 1.) Dried Latex Polymer: during production the moisture is removed by a spinning process, leaving only the dried polymer powder, this is then blended with the sand and cement into a single component.  When you add water to the mix on the jobsite these are then reconstituted to create a polymer-modified mortar. 2.) Liquid Latex Polymer: these additives are part of a two-component system, the liquid latex additive with the powder on the jobsite.  Since these polymers are not dried and reconstituted, the latex is able to mix with the sand and cement particles as they begin to grow and expand—creating a stronger deformable mortar. 
 
As you will note in the photo, the two-component liquid latex polymer can twist, elongate, even be tied into a knot without failing. Whereas the dried latex polymer that is used in single-component mortars can bend and deform, yet it does not have the ability to elongate and twist like the liquid latex additive.  How does this translate into selecting a mortar?  Wherever you have the potential for increased ‘cycles’ of movement, either from thermal expansion or shrinkage, or deflection, or an impervious surface such as a porcelain tile—more polymer is required.  For example, on an exterior tile facade application in Florida—although there is high humidity (70-100% RH) and hot temperatures (75˚-95˚F), it is relatively consistent year round with few fluctuations, or extremes in thermal growth and shrinkage—a single component may perform well in these conditions.  Conversely, the same application in Minnesota, has very different requirements—extreme variations in temperatures will require a two-component liquid latex mortar that can deform in the below zero temperatures of winter to the mid 80’s of summertime.  Keeping the installation environment in mind is key to selecting the ‘right mortar’ for the ‘right application’….