Before starting stone or tiling works, it is important to select the correct bedding
adhesive to ensure its performance. No one single formula adhesive can be used with
all stones/tiles and substrates. The first step in choosing a tile adhesive is to consider
the location of the installation e.g. whether the stones/tiles are to be installed inside
or outside the building, to the wall or on the floor, in a wet or dry area, and the type of
receiving substrate e.g. concrete, render, screed drywall, etc.
Polymer-modified cementitious adhesives
Polymer-modified adhesives are widely accepted in the industry and often referred
to as thin-set mortars. The blended polymers interact with cement components to
improve the physical and mechanical properties such as increased adhesion, reduced
shrinkage and lower water absorption. In most cases it is suitable for wet or dry
installations. The polymer additives add strength and flexibility to the mortar, without
which the bedding can crack easily.
The polymer modified adhesives are commonly available in two types. One comes with
powdered polymer as pre-mix. Hence, during the application, only water is required to
be added to make a bed. The other type requires addition of liquid latex additive rather
than water. The second type is generally used for natural stones which are prone to
moisture ingress and also for a fast setting installation. It also reduces the effect of
back staining on natural stones and gives better shear bond strength to the bed.
5.1 CLASSIFICATION OF ADHESIVES
Based on ISO 13007 -1:2004, tile adhesives fall into three major categories:
Type C (Cementitious): Mixture of hydraulic binding agents, aggregates and
additives; to be mixed with water or other liquid just before use.
Type D (Dispersion): Ready -for-use mixture of binding agents in the form of polymer
dispersion, additives and other mineral fillers.
Type R (Reaction Resin): Single or multi-component mixture of synthetic resin,
mineral fillers and other additives in which the curing occurs by chemical reaction.
The above categories can be further divided into the following classes:
(i) Normal adhesive (Tensile strength > 0.5 N/mm 2 ) : Class 1
(ii) Improved adhesive (Tensile strength > 1.0 N/mm 2 ) : Class 2
They can be categorized according to the following characteristics:
(i) Fast-setting with early tensile strength adhesive : F
(ii) Slip-resistant adhesive : T
(iii) Adhesive with extended open time : E
(iv) Special deformable characteristic (Type C only) : S