Product category:
Floors
News Release from: Ardex UK | Subject: Installation of bases and screeds
Edited by the Buildingtalk Editorial
Team on 07 April 2005
Bases and screeds for resin floorings
and coatings
Cyril Potter, Chief Chemist at Ardex UK gives details about the installation of bases and screeds for resin floorings and coatings
One of the requirements for resin floorings and coatings is the provision of an adequately strong and hard base so that the full potential of the flooring or coating can be achieved In most cases a good quality concrete base is the best option, providing it can be finished to the surface regularity required for the resin flooring or coating
This article was originally published on Buildingtalk on 30 Jun 2008 at 8.00am (UK)
Related stories
System Ardex for new Sports and Media Centre
Ardex UK and Cerface Limited recently provided a 2500m2 tiling and grouting solution at the newly developed Tonbridge School Centre for Sports and Media.
West Cumberland Hospital gets the Ardex treatment
Ardex worked with flooring contractors TT Flooring of Workington, who were commissioned to install the floorcoverings for the refurbished West Cumberland Hospital.
Thin resin floorings and coatings will normally require surface regularity 1 and a surface finish acceptable for the direct application of the resin flooring or coating.
In most cases the normally acceptable finish on the concrete base will not be suitable unless the appropriate finishing technique is used so that not only is the required surface regularity achieved but also the surface is 'flat' and smooth enough for the thin resin flooring or coating.
The higher standard of surface regularity may not be necessary, depending on the requirements of the resin flooring and end use, providing a smoothly undulating surface is acceptable.
Further reading
Ardex new Microtec Tile Adhesives range
Ardex UK will be at the Tile and Stone Show and will showcase and demonstrate their recently launched Microtec Tile Adhesives range.
New tile adhesive is fixing the future from Ardex
Ardex, innovator in high performance tile fixing systems announce the UK launch of its new premium tile adhesive, the Microtec range.
Call of duty answered by Ardex at Gamestation
Ardex Feather Finish to smooth over the new plywood floor at Gamestation new store in Hull.
Note that the surface preparation technique used will also affect the texture of the surface and the coating that may be used.
CONCRETE BASES.
Direct finished concrete surface designed to accept floorings should be installed in accordance with the recommendations of BS 8204-1 and a minimum grade C35 concrete with a minimum cement content of 300 kg/m3 should be used.
It is also advisable to use clean aggregates with low content of soluble salts to reduce the risk of osmotic blistering in the resin flooring.
The concrete base installed to receive resin floorings and coatings should have been cured for at least 7 days to prevent rapid surface drying and then any curing membranes should be removed to allow the concrete to dry.
Note that some spray-on curing membranes may penetrate into the concrete surface so they should be used with caution in case they inhibit the adhesion of resin floorings and coatings.
Other types can prove difficult to remove completely using only shot blasting techniques.
LEVELLING SCREEDS.
Where a levelling screed has to be applied to a concrete base to provide a suitable base for a resin flooring it should be laid normally as a bonded screed.
The concrete base should be sufficiently mature so that most of the drying shrinkage has taken place.
The guidance generally given is to cure the levelling screed for 7 days and allow air drying for sufficient time for the screed to reach an acceptable moisture level.
The bonded screed should be a polymer modified cementitious screed and be compatible with the resin flooring or coating and should also provide the required cohesive strength and load bearing capacity.
Testing for surface strength is described in clause 7.2 of BS 8204-6, the rebound hammer test requires a reading of not less than 25, whilst the surface tensile strength test (pull off) requires at least 1.5N/mm2 .
2.
In some cases there may be limitations, depending on the restraint that has to be provided, on the type and thickness of resin floorings that can be laid on levelling screeds.
The manufacturer of the resin flooring will provide advice on such limitations and usually polyurethane resin floorings and the thicker resin floorings require a higher degree of restraint and are normally installed on concrete bases.
BS 8204-3 should be consulted for the application of any polymer modified cementitious levelling screed necessary to prepare the concrete base prior to the application of the resin flooring or coating.
Cement sand screeds should be installed in accordance with the recommendations of BS 8204-1 paying particular attention to the use of suitably graded screeding sand and a forced action mixer to produce a workable and compactable mortar within the recommended cement/water ratio.
SCREED APPLICATION.
The concrete base should be prepared using mechanised equipment to remove all weak and friable surface residues, surface laitance, etc The use of scabbling equipment or contained shot blasting equipment with vacuum extraction is recommended.
The prepared concrete surface should be vacuum cleaned to remove and dust.
The screed mortar should be mixed in a forced action mixer; free fall (tumble drum) mixers are not suitable.
The prepared concrete surface should be treated with a suitable bonding grout/slurry immediately before applying the screed mortar, placing it 'fresh in fresh' on the bonding grout.
The levelling screed should be finished to the required surface regularity using either a steel trowel or wood float as appropriate for the resin flooring being applied.
If speed of installation is necessary the use of either a rapid setting, hardening and drying levelling screed with a polymer admix, or a pumped cementitious screed with rapid drying and early strength development properties can be advantageous for some resin floorings and coatings.
Compatibility of the resin flooring or coating with proprietary systems should be established at the design stage.
SURFACE PREPARATION TO RECEIVE RESIN FLOORING OR COATING.
The surface of a direct finished concrete slab or levelling screed should be suitably prepared to remove all laitance, lime bloom and cement paste, as well as residues of curing agents and other barriers to adhesion.
The use of contained shot blasting equipment is particularly useful for this operation since it is quiet and essentially dust-free, selectively removing the cohesively weak residues without unduly roughening the surface.
Surface grinding of the concrete is also an option and has some use in removing localised surface irregularities.
For resin floorings thicker than 4mm, where the surface profile of the concrete base is unlikely to show through the resin flooring, a rougher finish to the concrete may be acceptable.
Where a levelling screed has been installed the surface should be clean and dry, any surface laitance being removed by light contained shot blasting.
Priming may be required prior to application of some resin floorings on a concrete base or screed that is sufficiently mature but is too damp for direct application of the require resin flooring.
The above advice, which naturally cannot be comprehensive, should be considered in conjunction with the information from the manufacturer of the resin flooring or coating and the recommendations given in BS 8204-6. Request a free brochure from Ardex UK ...
• Ardex UK: contact details and other news
• Email this article to a colleague
• Register for the free Buildingtalk email newsletter
• Buildingtalk Home Page
Search the Pro-Talk network of sites
