Thread: Laitance on a new slab - how to approach removal/repair?

Scouse,
Just wanting to commiserate with you. I know the feeling of building a nice workshop. That first 200 out of the ground is expensive but should make you smile not frown once its done.

I would hate my workshop to have an exposed aggregate surface. Smooth and shiney that oil wipes off is for me. I would vote for surface grinding (even if you came to an arrangement with the contractor: Say you hire the conc grinder but the work is done by them. It should be relatively easy as no real clean up needed - should only cost him a days labour)

Then you arrange to surface finish it which you would have had to do anyways?

With my slab instead of sealers and epoxy I went with Resene pavement paint. I gave it a few weeks to cure, then a light acid wash and pressure clean then paint with a big roller.
Not as hard wearing as epoxy but as I do a lot of welding epoxy would die quick and be hard to resurface. The Resene is easy to clean oil off and then every couple of years push all the workshop crap to the walls, tape off the middle workfloor that has been marked/scuffed and burnt, a light acid wash, pressure blast, dry and re-coat.

Each to their own on finish but I would have a yarn with the contractor to enable you to come up with a smooth flat surface.

Steve

You are all missing the point.
Facts stated are: The contractor placed the concrete as per specified plans.
Various ISO's apply to the application of pouring a slab and its finish.
All you experts in contractual law, please show me where it is stated that the contractor is required to perform his task in inclement weather and still provide the same finished surface as detailed in the applicable standard for concrete finishes.
One fellow even assumes that this contractor was unprofessional. Big call coming from within an air con'd office with no rain falling on his desk.
Stop stirring the pot people and answer the question that was asked by the OP.
Don't give your 2 cents worth of opinion when it is not based on fact.

Grinding - it all depends on the depth of the dusty concrete..... normally the cause of dusting is the opposite - heat and evaporation of the required water ....

Many supermarkets these days just slap down their floors and then grind them to give a nice exposed aggregate but polished look. The surface is treated with a sealer as well.

Also it is important that you do the grinding before any frame erection is commenced. Otherwise you will have daggy edges all around. The grinding machines need all the room they can to move around and do their job properly.

Originally Posted by gasman

You are all missing the point.
Facts stated are: The contractor placed the concrete as per specified plans.
Various ISO's apply to the application of pouring a slab and its finish.
All you experts in contractual law, please show me where it is stated that the contractor is required to perform his task in inclement weather and still provide the same finished surface as detailed in the applicable standard for concrete finishes.
One fellow even assumes that this contractor was unprofessional. Big call coming from within an air con'd office with no rain falling on his desk.
Stop stirring the pot people and answer the question that was asked by the OP.
Don't give your 2 cents worth of opinion when it is not based on fact.

Actually you may be missing the point mate, having worked as a construction supervisor if a contractor provided a slab as described the solution always was to rip it up and do it properly. You better read those AS documents (no not ISO) a little better before making accusations against others.

I had a similar problem years ago. Laid house slab in what began as a fine day but ended quite wet. Concreter finished slab in the rain.
After curing and building house, suffered from excess dusting. Swept and vacuumed area thoroughly then sealed with paving paint. Carpet layers, when carpet eventually laid were rapt - no dust.
There was no need to blast or acid wash as the surface was already roughened to allow proper bonding/penetration of the sealer.

Originally Posted by gasman

You are all missing the point.
Facts stated are: The contractor placed the concrete as per specified plans.
Various ISO's apply to the application of pouring a slab and its finish.
All you experts in contractual law, please show me where it is stated that the contractor is required to perform his task in inclement weather and still provide the same finished surface as detailed in the applicable standard for concrete finishes.
One fellow even assumes that this contractor was unprofessional. Big call coming from within an air con'd office with no rain falling on his desk.
Stop stirring the pot people and answer the question that was asked by the OP.
Don't give your 2 cents worth of opinion when it is not based on fact.

Who are you and what do you do??? Have you ever spent more than 1/2 a day on a construction site?

The concreter had the choice to pour or not. That is their call and they should do so with a good knowldge of the weather for that day. If they choose to pour they must be prepared (i.e. plastic sheets, tarps to cover) One could only hope that you get shafted like this, becasue Id like to see you feeling towards your current stance.

I will say that it is on par with some, not all concreters, who seem more interested in getting to the pub or the next job than the results of someone ELSES home, shed etc. And yes that is coming from 20 years of dealing with them.

Scouse: Re surface finish. Im not sure what the original plan was, or if some product was going to be applied, but there is no NEED to have a sealer etc put on a normal finish slab. If the slab was finished without problem and not dusting, then yes you could choose to have a sealer etc, but do not NEED one. If now because of the dusting issues you may need some grinding or such and a sealer. I will leave that to sort out with you and shed co.

Regarding the dusting, I am taking it, it is not just very light dust, but more so that if you sweep it it keeps coming off, lots of fine powder and the slab is being erroded as you do?

Firstly, thanks for your time & commiserations regarding this. After a horror couple of years in this new house, I really thought the worst was behind us.

Originally Posted by uninformed

Scouse: Re surface finish. Im not sure what the original plan was, or if some product was going to be applied, but there is no NEED to have a sealer etc put on a normal finish slab. If the slab was finished without problem and not dusting, then yes you could choose to have a sealer etc, but do not NEED one. If now because of the dusting issues you may need some grinding or such and a sealer. I will leave that to sort out with you and shed co.

Regarding the dusting, I am taking it, it is not just very light dust, but more so that if you sweep it it keeps coming off, lots of fine powder and the slab is being erroded as you do?

In my current shed (on my Dad's property), I did the slab myself in 2 pours after the shed was up due to $$. The first part I just screeded off & suffered dusting problems. The second part I used a helicopter & had a near perfect finish. Any oil spilt wiped off easily & I didn't need to coat it with any paint/sealer.
This is what I was expecting with a professional concreter, other work by him shows he can do it.


I want a low maintenance shed. I don't want to have to paint/seal the floor every year of so & I can't afford the cost of professional epoxy type paints. A regular smooth finish is what I expected.


The dusting is severe in my book. In some spots, a few rubs with my finger & I'm down 3-4mm from the surface of the slab.




The concreter told me on the day that he tried calling off the job due to the weather but was pressured into it by the concrete pump guy. He also told me that he couldn't sleep the night after the pour as he was worried about how the slab would look the next day when they came back.
At the end of the job he told me he's never going to do a slab in those conditions again.
So, it's pretty clear to me who's responsible for this mess; I thought I'd get some advice from here about how it can be rectified before I approach the concreter (forewarned is forearmed).


I actually had 200sqm of pathways done around the house by a different concreter a week before the slab was done. He's coming around this afternoon to have a look to see how bad it is. Over the phone, he was shocked when I told him I can rub down nearly 5mm with my finger.

Originally Posted by clive22

Looked at a self leveling or other compounds they may help too? Ardit.,BASF, Parchem, Xypex. There's more than one way to skin a cat, tech reps will usually help.

Maybe grinding is the only alternative, but will be slow. How bad is it?

If is not too bad you may be best trying soemthing else, is it going to effect the functional use of the slab? You may have trouble mounting a successful argument as this is a natural process of concrete.

I suppose I'm getting to the point, there is no point entering into an argument withholding money etc unless realistically you can prove its bad.

Usually you would grind and seal the slab from the start if this was key performance characteristic of the end product. There is nothing to stop you/them doing this now

I would suggest you negotiate an outcome, withholding money can quickly descend into an expensive building dispute which may not result in a higher grade of slab.

I don't want to coat the slab with anything. Paint/sealer = maintenance. I think grinding is an option but I won't have a 100mm slab after that. It might be 95mm at best, maybe even 90mm looking at the amount I can rub away with my finger.


Withholding money is the last thing I want to do, I just threw it up as a possible option in case someone here has 'been there, done that'.