Epoxy grouted skids construction technique(s) 1

[WARose]

I do a lot of machine foundations.....and in many cases I use epoxy grout to bond the bottom of the skid to the top of mat. In some cases, we are talking some pretty cumbersome skids: maybe 60' long and having I-beams @ 10' o.c. with a lot of difficulty accessing the interior skid members due to the equipment mounted on top of the skid.

I get some complaints on this from time to time from contractors. A technique I've seen some do is a "head box" where they pour the epoxy grout into a square shaped (plywood) box several feet taller than the skid and is connected at the bottom to the epoxy form.....and it just flows right on into the form box for the skid base.

But for something 60' long.....and no access from the side, this proves difficult. So can anyone suggest a practical technique? Thanks.

 

[TLHS]

Sika and BASF (Master Builders) have always been really good at helping me with practical grout issues. Sika, specifically, has sent people out to the field to walk things through with the contractor and confirm or suggest changes to my initial work plans.

It's a good resource.

A thought would be to pregrout the interior of the skid if access is really tricky and then just grout the underside at site, but it may not be practical on a larger skid. Cutting access holes at strategic points is likely helpful, but it will depend on the grouting method and the skid layout.

 

[WARose]

Actually I talked to BASF/Master Builder's tech support on this.....and didn't get much info.

One thing I suggested to them was putting down the epoxy grout.....letting it harden.....and then adding the equipment. After all, I'm not worried that much about separation from the skid and the grout (considering I typically used bolts with lots of preload on them).....I worry more about the grout getting separated from the top of matt.

But they didn't like this idea.

 

[XR250]

One thing I suggested to them was putting down the epoxy grout.....letting it harden.....and then adding the equipment.

Isn't the purpose of the grout to conform to the irregularities of the concrete as well as the equipment? Is so, how would that work if it is already hardened?

 

[WARose]

Isn't the purpose of the grout to conform to the irregularities of the concrete as well as the equipment? Is so, how would that work if it is already hardened?

That's (essentially) what they said. But I worry more about the concrete side of things (in that situation) than the steel side of things.

In any case, they nuked it.....so I'm not sure I would try it anyway.

 

[Ingenuity]

What is the typical max/min dimensions from top mat to u/s skid - i.e. the grout thickness?

 

[WARose]

What is the typical max/min dimensions from top mat to u/s skid - i.e. the grout thickness?

I typically shoot for 2 to 5". (On the thicker side for heavy unbalanced loads and/or complicated skid pours.)

 

[canwesteng]

Won't it just flow freely around the base of the skid? Or is the cost of the excess grout what's bugging the contractors? I've seen this done with forms (not several feet tall) and flowable epoxy.

 

[WARose]

Won't it just flow freely around the base of the skid? Or is the cost of the excess grout what's bugging the contractors? I've seen this done with forms (not several feet tall) and flowable epoxy.

We are talking a long, narrow form underneath the skid (with no side access). The contractor's complaint(s) on this are well taken in that it is difficult for the grout to reach everywhere it is suppose to without lots of head on it. But for really tricky geometry, I am told by some this gets impractical. Hence my question here (i.e. looking for alternative techniques).

 

[epoxybot]

It really sounds like a pressure grouting job. Something contractors have to cobble together, since no manufacturer wants to provide equipment to pump 'mixed' epoxy. Epoxy grouts get progressively higher in viscosity and flow diminishes as they proceed towards the end of their working time. I know contractors who have used pumps similar to Chem-Grout CG-050 Grout Pump with epoxy grout, for a different application but it is tricky (the pump can scavenge resin) and clean-up needs to be meticulous or the following day the pump is a boat anchor. Chem-Grout may have some advise on pumping epoxy grout but you will have to get past the customer service people and talk to a field tech.

While I doubt they have an off-the-shelf solution, the people at Insituform might have the experience to tackle a limited access project and maybe even put together a system if they thought there was repeat work.

 

[WARose]

Good info epoxybot. I wasn't sure you could even pump epoxy grout (mechanically). BASF doesn't show it in their demos. I may ask them if it's ok. IIRC, they don't allow vibrating it.....so that may give a hint. (EDIT: The data sheet talks about it.....but they have max. recommended distances that you can pump.)

I worked with Insituform (about 20 years ago). The only epoxy I remember them using was the resin they put on the side of the pipe liners they used. Not exactly the same issue.....but I could ask them.

 

[BridgeSmith]

Epoxybot beat me to it - I was also about to suggest pressure grouting. We use it for grouting the ducts around post-tensioned bars.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[epoxybot]

Master Builders used to have a two part pumping system for pile encapsulation. A-P-E, Advanced Pile Encapsulation. It may now be part of Wabo and moth-balled because it is a rare application. The grout was specifically formulated to a 1 to 1 ratio so dual pumps delivered to a large metal static mixer and then through the hose. Those experienced with the equipment (contractors & field techs), kept a supply of 2,4-DINONYLPHENOL, an extender used in epoxy formulas, to increase the binder(mixed resin) content a bit because the pump squeezes resin from the grout as it cycles. So you mix a small batch, do a flow table test. Pump a small batch, do a flow table test and try to adjust the binder in the pumped grout upwards to match the original un-pumped flow table test. 2,4-DINONYLPHENOL is some what of a plasticizer, so it isn't a good idea to go over 5%. It can also accelerate a formula, so potlife & working time tests have to be done.

 

[WARose]

Thanks again epoxybot.