pre cast concrete paving slab problems

[Thermo]

Firstly moderators, dont move this to gardening, im after some comments from the regulars who frequent this section.

Im a bit stuck in the middle with a problem on a job, with a very nice customre who weve dfone lots of work for and a supplier who manufacters paving slabs, who weve used countless times. The scenario and problem is this:-

They live on an area of free draining chlak and have a back garden at the bottom of a hill which is probably 90% of the time in the shade. we laid a simple patio for them in may of last year, on an mot sub-base, blue circle based cement mortar bed. After about a month the york stone coloured riven slabs, started to break up in patches on the riven areas, and started to discolour. There was a fair bit of rain, but at that time of year it was still warm and mainly sunny. The manufacturers ended up coming to look at it and in the end we got them to agree to pay for the whole thing to be replaced. (which was a bit heartbreaking as it all had to come through the house!)

We replaced it in august of last year and by early november there were darker patches appearing on the concrete, similar to before. The company came to look at it again and said see how it faired for a few months. It is now in pretty much the same state, with the client telling me she can sweep of powder from the top of the slabs. The company are saying its all down to the climate in the area whhere the slabs are and not their problem. The legal wrangles are an aside and the customer has absolutley no problem with the workmanship, nor does the manufacturer.
They say they have had no problems with any of the other slabs from that or any other batches that thye have made, and i have laid thousands of their slabs and never had a problem like this. Could the damp affect a precast slab so quickly?

I just wondered if anyone has experianced anything similar or may have some views on what is causing it, if anything other than a manufacturing fault. Im goin to look at them next week and ill try and post a photo.

 

[joe-90]

Why did you lay it on a mortar bed rather than compacted stone covered in sharp sand? You have no drainage so I guess that might be something to do with it.

 

[^neo^]

Marshalls?

 

[Thermo]

Why did you lay it on a mortar bed rather than compacted stone covered in sharp sand? You have no drainage so I guess that might be something to do with it.

stop talking out your arse joe

 

[Thermo]

Marshalls?

no its a small company down this way that produces its own stuff

 

[hotrod]

It wouldn't be global stone by any chance would it Thermo?

 

[Thermo]

no and im not going to name them on here as it wouldnt be fair.

Just to add nothing has happened to the pointing in that area, which i would have thought may have if the micro climate had some eefct on the cement based product

 

[hotrod]

I know it's a long shot Thermo, but is there any possibility that the ground could be contaminated (either natural or previous usage, petrochemical, mining etc)?

Just seems very, very strange that you've done it twice and the workmanship and materials are all fit for purpose, yet it has failed twice

 

[dextrous]

Since the original stones deteriorated, it does sound like they have created a bad batch by misfortune - maybe it's the cementone they're using or a stale cement or a contaminated aggregate.

As for their claim that noone else has complained, well you have only their word for it and/or maybe nooone else has used that batch and/or customers think it's the norm. On the other hand, maybe there is some curious run-off from being at the bottom of the hill which is creating chemical breakdown.

So I think you're only option is to go down the legal wrangling side and try to get a materials refund/replacement and then it's up to you how much goodwill you're prepared to give the customer for a third-time-lucky re-lay using a different supplier or same supplier with different stone.

 

[joe-90]

Thermo. It's YOU that's done it wrong. It's not happening to anyone else is it? Doesn't that tell you something? You've created a mini swimming pool that the slabs are sitting in. Be man enough to admit it.

 

[Thermo]

i did wonder about possible contaiminents in the soil, but then its laid on a bed of mot and some of that was changed when we relaid it, so it would have to have leeched up through that.

I can understand a bad batch once, but twice seems bizarre. I agree with you about other complaints, but having said that ive been the go between with both of them, i know the company well and they have been very open and honest with me. (i think!)

As for the legal wranglings, the client is in no way pointing the finger at us, its very much between them and the supplier, with the supplier paying all our costs last time

 

[noseall]

Climate or soil conditions are not selective. They can not pick on one cement based product and not another.

Joe, you are talking utter rubbish, and like an amateur.

 

[joe-90]

Let me make it simple for you muppets.

He has dug a non-draining hole. He has filled it with a cement pruduct and set his slabs.

What he has done is make a mini swimming pool to sit his slabs in.

The proof that this is so is that the slabs discolour over time. The only way that can happen is if the slabs are absorbing water from below.

If the damage were happening from above (called rain) then this would happen all over the world and the odds are that someone would have noticed by now.

So what we have is waterlogged slabs sitting out under a frosty sky.

The top layer of the slabs freeze - and the ice crystals pop off the top layer. (In brickwork it's called spalling)

It's called erosion and it wears away whole mountain ranges.

If it were a chemical problem then the damage would occur to the base of the slabs - not the top. (and nothing would grow in his garden).

Get with it folks - it's elementary science.

 

[noseall]

Joe, a slab is an OUTDOOR product.

Riven slabs hold a bit of water that will freeze in the winter and manufacturers are aware of this fact.

Get yourself on the pro' train.

 

[joe-90]

Learn some science mate. I've told you what the problem is - you just don't have the education to realise it.