Concrete Testing

[Joseph.M]

Does anyone know much about concrete testing? There's a concrete slab that's breaking up after a few years of being laid. There's two possibilities for why it's happened. The truck that delivered the concrete was the type that mixes the concrete as it comes off the truck, and it was noted by one of the workers that the sand and cement look fully mixed. The second possibility is that it took a long time to wheelbarrow the concrete from the roadside to the site, so it could have started to set before it was spread, which would weaken it. Liability depends on which of these two reasons was the fault.

I've Googled a few testing places but they all only do destructive testing to check it's strength. They don't do analysis to see what's happened on a chemical level, though I've seen some universities that do it, but not commercially.

 

[angellonewolf]

going to be hard to prove i would think with out spending money to chase it

first cant you call the supplyer of the concreat or was the council involved at the planning office they might be a help but a long shot ?

 

[clift_d]

Normally that sort of thing is done with samples taken at the time of laying - typically a slump test for water content and a cube test for compressive strength.

Getting hardened concrete analysis done subsequently is not going to be cheap, and they will almost certainly need to take destructive cores to test.

 

[Rocketman]

Does anyone know much about concrete testing? There's a concrete slab that's breaking up after a few years of being laid. There's two possibilities for why it's happened. The truck that delivered the concrete was the type that mixes the concrete as it comes off the truck, and it was noted by one of the workers that the sand and cement look fully mixed. The second possibility is that it took a long time to wheelbarrow the concrete from the roadside to the site, so it could have started to set before it was spread, which would weaken it. Liability depends on which of these two reasons was the fault.

I've Googled a few testing places but they all only do destructive testing to check it's strength. They don't do analysis to see what's happened on a chemical level, though I've seen some universities that do it, but not commercially.

Why do you think there are two possibilities?
You could write a book on the factors that influence the performance of concrete. Was the cement off, quality of ballast, yes was the it mixed correctly, water content, correct additives used if required, environmental conditions on pouring and proceeding time to full setting, methods used pour, pre-pour sub base quality and implementation of barriers, correct implementation of any reinforcement and the list goes on and on.

 

[cocker]

Was it thick enough in the first place

 

[arther dailey]

Rocketman hit the nail on the head, was the sub base suitable,depth cast,reinforced for type of traffic,etc etc.it is I would agree an endless list.

 

[brightspark]

u haven't gave any indication of whats happening . is it crackling or crumbling. is it a road path . any expansion joints in it depth sub base etc . the list goes on

 

[Bryan Williams]

Sorry to jump on a post but I've got a bit of a concrete question myself.
Recently work got job to lay a base,its a sheetmetal company so no one had a clue apart from me and I've just done bits for myself.
Iy was 3m×4m about 25 cm deep,on hardcore.
The hardcore and shuttering had been done before I got there.
Anyway it was the kind that has a mixer hanging off the back end , it's mixed and barrowed .
I told them I wanted it stiff enough to sit in a line so we could tamp it down roughly a metre at a time working back.
They pulled a bit of a face saying that people usually want it sloppier so it kind of self levels but they did it my way ,it held them up a bit as they had to wait for us to tamp moving back.
It came out ok,no n much water floated up ,we didn't have to play around with it.
Were they right tho?
I got the feeling I was slowing .t the job down.

 

[cocker]

Sorry to jump on a post but I've got a bit of a concrete question myself.
Recently work got job to lay a base,its a sheetmetal company so no one had a clue apart from me and I've just done bits for myself.
Iy was 3m×4m about 25 cm deep,on hardcore.
The hardcore and shuttering had been done before I got there.
Anyway it was the kind that has a mixer hanging off the back end , it's mixed and barrowed .
I told them I wanted it stiff enough to sit in a line so we could tamp it down roughly a metre at a time working back.
They pulled a bit of a face saying that people usually want it sloppier so it kind of self levels but they did it my way ,it held them up a bit as they had to wait for us to tamp moving back.
It came out ok,no n much water floated up ,we didn't have to play around with it.
Were they right tho?
I got the feeling I was slowing .t the job down.

250 thick , was it reinforced ? Did you use a poker ?
Or did you just chuck a bit of conny in ,

 

[cocker]

Does anyone know much about concrete testing? There's a concrete slab that's breaking up after a few years of being laid. There's two possibilities for why it's happened. The truck that delivered the concrete was the type that mixes the concrete as it comes off the truck, and it was noted by one of the workers that the sand and cement look fully mixed. The second possibility is that it took a long time to wheelbarrow the concrete from the roadside to the site, so it could have started to set before it was spread, which would weaken it. Liability depends on which of these two reasons was the fault.

I've Googled a few testing places but they all only do destructive testing to check it's strength. They don't do analysis to see what's happened on a chemical level, though I've seen some universities that do it, but not commercially.

Was I'd designed by an engineer , or just boshed in coz any Muppet can do concreting - innit

 

[Bryan Williams]

250 thick , was it reinforced ? Did you use a poker ?
Or did you just chuck a bit of conny in ,

Nope,ten inches deepish, poured in,tamped....away with the mixer.
Base for a UU storage building.

 

[Pete.]

Concrete crush testing is fairly cheap. Usually you crush a cube of set size but for old concrete you can core a 107mm hole in it and take it to a testing service. We use Sandbergs in Clapham but you can find them all over the place. They will tell you right away what the concrete compression strength is.

 

[Dcal]

My top 4 reasons for concrete failing is
1 - adding more water than was specified for the mix (In simple terms if you want a wetter mix, you need to add more cement to get the same strength of concrete)
2 - not curing it properly, i.e not covering it with plastic or spraying a curing agent (Concure) over the exposed wet concrete, or keeping the slab wet until it cures (If you leave concrete exposed the out side of the concrete can dry before the cement hydrates and will be weaker than the core of the concrete and can flake off)
3 - not compacting the concrete, (depends on how thick the slab is - tamping might not be enough to compact it)
4 - not placing or reworking the concrete after it starts the initial set.
Then as said before there is a massive list - What was specified? Was it placed on properly compacted base? (Not a fault of the concrete but could have a massive effect on it's capacity and durability) What load and service was it designed for? What were the dimensions of the pour? Were there any expansion joints? Did the frost get at it? Did it crack because of thermal expansion? Was there any reinforcement? If so what was the re-bar cover? etc etc.
Biggest issue you will have now is proving that the company that supplied the concrete didn't give you what you paid for, or that the people that placed didn't do it as specified. If you don't have a specification and dockets showing what was ordered and delivered and confirming that you didn't add extra water on site, it is going to be very difficult to argue.
Did you carryout slump tests and take concrete cubes before the concrete was placed?
Drilling cores and crushing samples is fairly cheap and easy to do, getting concrete analysed (which will show cement content and type, water ratio, aggregate size and type, additives if any, etc.) can be done and is more expensive, but if you can't show what you asked for in the first place, what use is the information to you.

 

[gaz1]

no offense guys if you want it to set for years then you have it brought in and pay the lads for doing the job

if your a skin flint and want it hand mixed or mixed to a required amount at the end of the garden then its your own fault

mixtures are mixtures not one company makes the same mixture as what would be in a proper cement truck delivered from the cement yard

additives and mixtures are also totally different between them

what type of sand and cement they used sorry even ive gone back to the proper cement bags the other stuff is so poor its crap

 

[Pete.]

I think that's th epoint Gaz they got a proper mix-on-demand truck in. There's nothing dodgy about using those - it's all we use because there's no waste and you only pay for what you want - and we never had a cube fail yet.

 

[graffian]

I know a bloke who worked as dogs body for whoever responsible for the
concrete testing on the M25, he took samples to a lab for analysis.
But he did the cube and microwave oven tests?

So you can do some sort of test with your microwave.

 

[DaveB]

So you can do some sort of test with your microwave.

There is a test for fresh concrete, before it has set, that you can do in a microwave to see how much water has been added to the cement and aggregate.
Usually uses a more powerful microwave than most people have at home.

@Joseph.M
There are commercial labs that will do chemical and petrographic analysis of hardened concrete.
The problem is you've got to prove that the specification for the works was correct and that the concrete supplied did not meet the spec, plus show that the concrete was properly placed and has not been abused since.
Cheaper to dig it up and start again.

 

[brightspark]

no reply from op what the concrete is for and what's happened to it never to be seen again