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Determining Product Thickness
 
Determining the volume of product required to bridge a known crack width in masonry.
The main considerations when specifying a project with elastomeric wall coatings will be the determination of the crack widths that currently exist in the concrete and the resultant dry film thickness of the Astec elastomeric topcoat required to bridge these cracks.
 
Note: the crack bridging ability of Dirtguard IR elastic is directly related to the products dry film thickness.
 
 
Crack width determination:
As the crack bridging performance of the topcoat is directly related to dry film thickness, the size of the cracks needs to be first accurately determined.  Both the existing size is required and needs to include compensation for any cracks that are likely to form in years to come.  Once known, the crack bridging chart that forms parts of the Dirtguard IR elastic technical data sheet can be used to determine the require D.F.T. and volume of product that must be applied a given area.
 
 
Determination of required product D.F.T.:
Using the crack bridging chart included with the Energy Star Dirtguard IR Elastic Technical Bulletin to determine the required D.F.T and product volume.

For the purposes of this excessive we will assume a maximum crack width of 0.8mm
 
 
Square metres / Litre =
First with the known crack width draw a line on the chart from the bottom crack width detail to the dissection point with the graph.  Then draw a line at 90 degrees to the left and find the dry film thickness in microns required for the given crack width.

The case below is assumed to have crack width of 0.8mm and a  required D.F.T. of 320 microns.
 
Crack width 0.8mm
Coverage m2/ltr                   623.4 divided by required D.F.T. 320 microns = 1.95 m2/ltr
Wet film build                       D.F.T. 320 microns divided by 0.6234 = 514 microns wet.
 
In this case for a 0.8mm crack the product should be applied at 1.95 m2/ltr regardless of the number of coats to do so.
 
It is highly recommended that the applicator conduct a test patch to determine the most suitable form of application technique to suit the project.  The product can be brush, spray or roll applied but as all of these technique will change with applicator and equipment used once the technique has been determined it should not change throughout the entire project.

In this circumstance the applicator needs to determine how to apply the product at 1.95 m2 per litre including all coats required to do so.  Or for the purposes of a 1.0 m2 test patch the product should be applied as 513 ml to the 1 m2 area.

Once all coverage rates are determined the entire project must be specified as a given volume per specified area.  The applicator then has a constant gauge during application as to the coverage rates being achieved.  As an example with a required total coverage of 1.95 m2/ltr the applicator needs to use 25.64 litres of product on each 50 m2 area.  If the applicator went “light on” and there was materials left at the end of this section the remainder must be applied.

The reason we specify as volume per given area on masonry surfaces is that it is an accurate on site method of insuring the required D.F.T. is achieved across the entire project.  In contrast to this method the use of wet film gauges for coatings on masonry is found to me problematic due to the surface irregularity of masonry substrates.

 

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