The importance of substrate testing

PETERBOROUGH, U.K. - March 2, 2015 - PRLog -- Over recent years, the range and diversity of concrete additives and levelling screeds has hugely increased.  This is, in part, a response to new building techniques and speed requirements, but even more so in an effort to offer environmentally friendly solutions.

Traditionally, this level of change would have had little impact on resin flooring as the majority of products sold were for industrial use (where substrates tend to be of a standard concrete specification).  However, things have changed.  With resin flooring now used widely in commercial projects, the need for resin installers to understand the screeding options available, and to complete substrate testing, has never been greater.

To ensure that resin flooring projects are completed without issue, it is essential to determine substrate compatibility.  Most resin flooring companies recommend, in line with BS8204-6 (Synthetic Resin Flooring – code of practice), that cementitious substrates (or underlayment screeds) provide a compressive strength of at least 25N/mm2 and a tensile strength of at least 1.5N/mm2.  Additionally, moisture levels should be 75% RH (relative humidity) or below.

There are a number of ways in which a substrate can be tested to assess suitability, but one of the most reliable is a bond test.  This is especially true given the increasing number of quick curing, fibre reinforced, large aggregate free and dense screeds available, some of which can even be cement free.  These factors, as well as the use of concrete additives, can limit the ability of a resin to bond to the substrate.

A bond test will provide clear evidence of whether a reliable bond can be achieved.  Additionally, a bond test applied as a ‘thick pancake’ can also be used to indicate the tensile strength of the substrate.

Surface strength / compressive strength is best tested on site using a Schmidt type rebound hammer (again as defined within BS8204-6).  This method gives a reliable assessment of surface strength (as a rebound figure) and most hammer manufacturers provide a chart whereby an equivalent indicative compressive strength can be derived.

Substrate moisture content can be simply assessed in a non-invasive way by using a Tramex type moisture meter.  This technology uses a surface applied meter to test moisture levels using electrical impedance.  Whilst arguably not as accurate as an invasive method, it is fast and provides an industry wide acceptable result.

Ultimately, customers and main contractors will expect the resin flooring installer, as an expert, to assess the substrate and pass it is suitable to accept a resin floor.   Failure to test can result in early life resin flooring delamination, something that no-one wishes to see.   Therefore, and in addition to moisture and Schmidt hammer tests, Degafloor recommends that all approved installation partners complete bond tests whenever even the slightest concern exists as to the substrate type and make-up.