Quikrete Course and Medium Silica Sand available at Home Depots & Lowes (round here):
Grade Predominant Size Range
US sieve number (mm)
Coarse No. 1963 #12 - #30 (1.7-0.6 mm)
Medium No. 1962 #20 - #50 (0.8-0.3 mm)
Fine No. 1961 #30 - #70 (0.6-0.2 mm)
(Quoted from a previous post by others)
I see that other list members have done a lot of work on sizing the ingredients for E/G mixes. I've had to do some of this in industry myself. Without for one minute wishing to denigrate the effort which is being put into sizing, may I make one small point please.
Any form of concrete, whether it is cement or epoxy bonded, really only shines in the strength evaluation when it is in compression.
We have all seen the tonnes of steel or whatever used to increase its strength in other modes. Where E/G shines is that all the material in the mix is bonded so much better with epoxy than is attainable with cement, thus increasing the compressive strength to heretofore unattainable levels. And has a much greater life expectancy before it fails due to fatigue!
Therefore we come back to maximising the compressive strength in much the same way as when used with cement bonding.
The basic premise with concrete, is that the small stones fill the gaps between the large stones, the coarse gravel fills the gaps between the small stones, the fine gravel fills again, the sand fills again until we arrive at the point where the Epoxy fills (and binds together) the remaining minute voids in the mix.
The only way we can properly assess the success of the mix used is to section it by cutting with a laboratory saw and assess the volume of epoxy between all the other load carrying materials in our brew. This really is a case where less (Epoxy) is better. I do this in practice by weighing the components but then the epoxy can float on top of the mix, so even that method can give ambiguous feedback
Typically, in industrial concrete, the mix ratio is somewhere about 3 parts of screenings (stone of about 20mm screen sizing) 2 parts of sand and 1 part of cement. In my experiments with E/G in volumes up to about 0.5m^3 I have typically found this ratio to be followed with the replacement of cement by Epoxy and introducing two grades of sand. Temperature also has an effect as in extreme cold the ability of the Epoxy to creep into every last crevice has been diminished considerably. An ambient temperature of about 15-19˚C I have found to be ideal. The mix is warm enough to flow and compact (using a vibrating compactor as for cement based concrete) whilst it is not too warm which would unnecessarily accelerate the the hardening cycle.
With kind regards,
Russell Dunn
Ferlach, Austria