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Posted: Mon Aug 26, 2013 12:21 am
by thehouse
When jointing compounds say the base has to be permeable (they all do), what counts as permeable?
I'm trying to rejoint the front path which is clay pavers bedded in mortar on concrete. Ridgid paving, right?
I'd like to do this with a resin or polymeric mortar, as recommended on the Rejointing a patio or driveway page, but they all say the base must be permeable. Does this rule them out for ridgid paving?
Posted: Wed Aug 28, 2013 7:18 am
by Tony McC
Not nesser celery, is the short answer.
I've had long and complicated discussions with two of the bigger manufacturers regarding just what constitutes a 'permeable' base. Most cement (Ooops, I'm supposed to call them 'hydraulically bound') mortars are, technically speaking, permeable, but nowhere near as permeable as, say, a bed of very coarse sand. So how permeable does permeable have to be when it comes to resin mortars?
My understanding of it, and I admit to struggling because my German is basic and their English is largely learned from American TV, is that a permeable bed is *preferred* because the resin mortar itself is permeable, and so surface water should be able to enter the joint and disperse into the bed. When a bed is impermeable, water in the joint becomes trapped which can, in certain cases and over the medium-long term, accelerate deterioration of the resin. It seems that particular 'blends' of resin are not as stable as the manufacturers would like when subject to near permanent immersion in slightly acidic water (rain water).
Where I really struggle to get a straight answer is on the degree of permeability. Give me a value: tell me what the cut-off limit is for permeability, something we can measure, so that we can design suitable mortars. That's when the conversation usually lapses in German and they smile at me as though I was a slightly batty elderly relative who'd just asked if the Kaiser was coming to visit.
So, I fall back on personal experience and I know from almost a decade of playing around with these resin mortars that, in the vast majority of cases, when a quality product from a recognised manufacturer is used (so a genuine resin slurry mortar and NOT a polymeric), they perform well enough when used to joint paving laid on a mortar bed.
I've been tracking a handful of jobs where resin mortars have been used on commercial projects and so far it seems that there's not much to worry about. The worst thing I've seen to date is greening (algaefication) where the water and other detritus trapped in the permeable joint provides an ideal substrate for algae and other small vegetation. I've not seen any failures that could be attributed solely to the bed being only slightly permeable, and I've not detected any softening of the resin.
So, to get back to a short answer: I wouldn't worry about using a *quality* slurry resin mortar to joint your clay pavers.
Posted: Mon Sep 23, 2013 11:43 pm
by thehouse
Tony McC wrote:Not nesser celery, is the short answer.
Thanks for your thorough reply 
Sorry I didn't see it earlier. Was relying on the forum to email me, but it didn't 
I've been tracking a handful of jobs where resin mortars have been used on commercial projects and so far it seems that there's not much to worry about. The worst thing I've seen to date is greening (algaefication) where the water and other detritus trapped in the permeable joint provides an ideal substrate for algae and other small vegetation. I've not seen any failures that could be attributed solely to the bed being only slightly permeable, and I've not detected any softening of the resin.
I got worried when I came across this review of GeoFix. Made me wonder whether they all had the same issue.
So, to get back to a short answer: I wouldn't worry about using a *quality* slurry resin mortar to joint your clay pavers.
I'm a paving newbie. Could you give some examples of what qualifies as a quality resin mortar. For instance, is GeoFix one?
Posted: Tue Sep 24, 2013 3:37 pm
by r896neo
It most certainly is not! Its real crap
Resins are 2 part mixtures which use epoxy resin to harden them. They are tough but expensive.
Polymeric's are 1 part mixtures that harden on contact with air, such as geofix, rompox easy or marshalls weatherpoint (probably the best by a stretch of the 1 parts).
Quality 2 part resins would be Rompox D1, GTFK vdw800
Then there are slurry applied cement based grouts like larsen FJM or steintec tufftop
Posted: Tue Sep 24, 2013 11:34 pm
by thehouse
Cheers guys. You've helped me a lot.