Which adhesive should I use?
The second question implied by the one in the main title could also be: Why are there so many adhesives available?
There are so many adhesives available due to technical and commercial reasons. However, from a technical point of view, the most suitable adhesive system should be chosen according to the installation conditions and requirements. Let’s start by taking a look at how adhesives for ceramic materials are subdivided according to Euronorm EN 12004 and then go on to examine, in more detail, a typical application example.
How are tiling adhesives classified (EN 12004)?
1. According to the chemical nature of their binder: • C – cementitious adhesives • R – resin-based adhesives • D – ready-mixed water-based adhesives
2. According to their performance characteristics: • class 1 with adhesion strength ≥ 0.5 N/mm2 (5 Kg/cm2) • class 2 with adhesion strength ≥ 1 N/mm2 (10 Kg/cm2) • F = rapid-setting**
3. Other characteristics (not mandatory)*: • F = rapid-setting** • E - extended open time • T = non-slip • S = deformability (only for cementitious adhesives)
If we take the above into consideration, an adhesive classified according to EN 12004 standards as C2 T E S1 is cement-based (C) with improved adhesion (2), is non-slip (T) with extended open time (E) and is deformable (S). These characteristics are easily recognisable, regardless of the product’s trade name or the information given by the manufacturer or retailer, because they are supplied on the Technical Data Sheet and, often, on the packaging of the material.
Here are a few examples of products from the Mapei range: Granirapid (C2FS1), Kerabond + Isolastic (C2ES2), Ultralite S1 (C2TES1), Keralastic T (R2T), Ultramastic 3 (D2T), Elastorapid (C2TEFS2).
Would we be able to identify the characteristics and performance of these adhesives just by reading their classification?
What do they mean to us?
Let’s look at an example.
APPLICATION EXAMPLE
Let’s imagine we have to install ceramic tiles on the facade of a building, a system widely adopted in Italy. The tiles to be installed are 400 x 400 mm x 8 mm thick and will be bonded on render.
Which adhesive should I use?
I could rely on the experience I have built up over the years and choose an adhesive I already used in the past for similar work. Or, I could use an adhesive recommended by a trusted retailer or by an expert who works in this particular sector. Even though their advice may be helpful, it is not always based on empirical data or on a sufficiently large number of similar examples. In this particular case, however, for example the Italian UNI 11493-1 regarding the installation of ceramic materials, and with specific reference to the EN 12004 classification system for adhesives, would guide the choice .
It is quite clear that the successful installation of ceramic materials does not depend solely on the actual adhesive system; other factors need to be taken into consideration (the double-buttering method, adequate grout lines, UNI 11493 – Substrate preparation and characteristics). But during the design phase, or during the purchasing and application phases, the category of the most suitable adhesive required for that particular type of installation may be identified by a correct interpretation of the documentation available regarding adhesives. Having this knowledge reduces the risk of indecision or choosing the wrong product, safeguards consumers and improves the skill level of professionals operating in this sector.
Marco Albelice. Mapei SpA Technical Services Department
* See EN12004 - section 4: SPECIFICATIONS
** Note: for rapid-setting adhesives this characteristic is mandatory where present