Crumbling cement floor in workshop

[MikeJhn]

I am an ex Chartered Structural Engineer and came across this problem on many many occasions, the usual reason for the surface of concrete breaking up is over watering the mix to try and make it flow when laying, usually the lorry driver's suggestion to speed up the unloading, or an amateur builder not knowing the finer details of concrete/water ratio's , what happens is the aggregate sinks to the bottom of the slab leaving a weak sand cement surface called laitance, patching with anything will not work as the underlying problem will remain, only cure is to chop out the top layer of concrete and re-lay a screed of some kind, sand and cement cheap, but labour intensive, epoxy expensive, or remove the slab and start again.

Epoxies and not Polyester resins as they shrink when curing.

 

[pe2dave]

Thanks @MikeJhn - quite likely, but too much work / cost for me I'm afraid.
Patching it is.

 

[MikeJhn]

In that case make sure you get down to a firm base and don't feather edge the patch, dig down to form a drop edge.

 

[gmgmgm]

I had a crumbly concrete floor. I used the self-levelling latex floor compound from Screwfix (with associated primer). Very easy to use, fine for foot traffic (probably not for vehicles). It doesn't "move around", it doesn't feel rubbery when it's only a few mm thick.

 

[Housey210]

I had the same problem and I did use an expoxy resin. Perfect, sealed the floor and twenty years on as good as day it was poured. Swept away all the loose stuff and followed instructions on tin. Unsure of the brand but the kit was simple, pull the plug on small tin and let that flow into the large mix, pour and brush. Slab was cast in three with two expansion strips so I went to that, 2.5 x 2mtrs, leaving a week between for area to harden before doing next. Poured into the deepest void first to level out then all over. Well impressed with product and very tough stuff. White, my choice as that helped bouncing the light around.

 

[johna.clements]

I had a crumbly concrete floor. I used the self-levelling latex floor compound from Screwfix (with associated primer). Very easy to use, fine for foot traffic (probably not for vehicles). It doesn't "move around", it doesn't feel rubbery when it's only a few mm thick.

The latex self leveling compounds are normally used under something like carpet tiles.

 

[MikeJhn]

Chemical Building Products (CBP) used to market a liquid call Lithurin and yes it is what is sounds like it was a chemical hardener that reacted with the lime in the concrete, it was found by accident when inspecting cow sheds that never had a problem with the top surface of the milking sheds dusting, use your imagination. LOL

 

[johna.clements]

Milk does not do concrete any good.

 

[pe2dave]

Milk does not do concrete any good.

Working in a byre for 4 years, concrete stands up to cows output pretty well, all 3.

 

[pe2dave]

A start. Cut clean edges, diamond edge blade.
Started (and stopped) with the grinding cup (too much dust, with mask and goggles).
Finished the rest with bolster and lump hammer.
Cleaned up (vac and compressed air).
Wetted, painted with a thin mix of the repair stuff.
Images: Prior to painting. A 'settlement' crack, cleaned out ready for filling.

Lesson: Don't use garage floor paint on ill prepared concrete!

 

[johna.clements]

A 'settlement' crack, cleaned out ready for filling.

The crack is probably from contraction of the slab shortly after it was poured. Concrete tends to contract as it cures.
The slab will be moving slightly with temperature so the crack may open up again. But it will not be a big crack judging by how it has not cracked the paint to the left of the patch.

 

[bp122]

Hey Dave

Not playing my own trumpet but this is a 1 day solution if you start early.

Thread 'Garage floor levelling' Garage floor levelling

In any case, keep us posted.

 

[pe2dave]

Hey Dave

Not playing my own trumpet but this is a 1 day solution if you start early.

Thread 'Garage floor levelling' Garage floor levelling

In any case, keep us posted.

Yes, I saw that. Sadly I'd painted the floor, so a simple covering wouldn't do, even if I was able to clear out my 'bombsite' beforehand!
Hope you've good adhesion, old to new stuff.

 

[bp122]

Yes, I saw that. Sadly I'd painted the floor, so a simple covering wouldn't do, even if I was able to clear out my 'bombsite' beforehand!
Hope you've good adhesion, old to new stuff.

Ah, understood.

 

[pe2dave]

Purchased Everbuild Jetcem Rapid Repair Cement, I'll (try to remember) to let you know
what it's like after a year.

Having used it, they ought to emphasise the 'rapid' bit. Says ten minutes? Felt more like ten seconds and it was going off. I'd say, not for a diy'er where open time (is that the right term?) is more important. I'm envious of plasterers that can lay it on and two sweeps for a good surface!
Now done (looks aweful).
Next step, 4:1 water:cementone stuff, then more garage floor paint. Despite sucking up water like a .... I'm going to leave it a couple of days to dry.

 

[baldkev]

How about epoxy floor paint?

 

[eribaMotters]

Although not exactly the same situation, I did experience issues with the concrete floor of my last workshop. It was laid by a team of cowboys. The mix was blind, the surface porous and damp. It also crumbled and I could not paint it effectively. Oh, it was also not flat. Otherwise it was perfect. [Joke]
Luck was on my side in that I could go over the top. I removed all loose paint and applied a bitumen type paint, two coats with a sand binding to the second coat. I bedded a row of 18" paving slabs down the long edges and centre of the 8 x 5m surface and left to set. This allowed me to get a level surface. I then screed between the rows with a 3 to 1 sharp sand and cement mix. After 6/8 weeks I painted the floor with Leyland oil based floor paint.
Apart from the heavy traffic loads of 350kg machines on castors the floor surface stood up well. I spot painted a few odd areas each year and repainted after 4 or 5 years.

Colin

 

[Bingy man]

Having used it, they ought to emphasise the 'rapid' bit. Says ten minutes? Felt more like ten seconds and it was going off. I'd say, not for a diy'er where open time (is that the right term?) is more important. I'm envious of plasterers that can lay it on and two sweeps for a good surface!
Now done (looks aweful).
Next step, 4:1 water:cementone stuff, then more garage floor paint. Despite sucking up water like a .... I'm going to leave it a couple of days to dry.

All comes down to the temperature when you start . If it’s a really hot day you don’t get long before it starts setting.

 

[pe2dave]

How about epoxy floor paint?

Sorry I've bought paint now. Advantage of epoxy paint please?
The old paint just flakes away from the crumbling concrete. Trying
* Remove paint
* Wire brush down to firmer stuff.
* Cementone at about 4:1
* new paint.
See if that will adhere.

 

[pe2dave]

All comes down to the temperature when you start . If it’s a really hot day you don’t get long before it starts setting.

~20. My experience: floor needs to be soaking wet, all around edges too. Mix very sloppy or it just dries almost immediately.
(For me) 'orrible stuff to work with.