Are my extention footings up to scratch?

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My ex-builder cast the foundation for my single story rear extention. He was dishonest so we parted ways. He gave me a 10 years warranty and an invoice for the job.
My new builder started this week he yesturday he drew my attention to the fact that a pieced of concrete 40cm long chipped of the corner of my foundations with a light knock to the concrete. The concrete feels porous and a bit crumbly. The chip broke in half in my hand with little effort. As you can imagine I'm a little posses off about that.
My current builder thinks that the offending section of the footings don't look right and he invited the building control surveyor to have a look.
Can I rely on a buildning control survayour to certify that the footings are ok? If not, what do I need to do to conclusively find out if my footings are right?
 

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how long ago was it laid? Was it ready mix or mixed on site? also do you know how much there is in cubic metres?

The wide variation of type and size of aggregate doesnt scream quality but its hard to see from a photo and that might not be indicative of the whole thing.

I think building control will offer advice but if you really want peace of mind and some comeback if it goes wrong you need to pay for a building surveyor or engineer to inspect and perhaps test it.
 
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how long ago was it laid? Was it ready mix or mixed on site? also do you know how much there is in cubic metres?

The wide variation of type and size of aggregate doesnt scream quality but its hard to see from a photo and that might not be indicative of the whole thing.

I think building control will offer advice but if you really want peace of mind and some comeback if it goes wrong you need to pay for a building surveyor or engineer to inspect and perhaps test it.
The foundation were laid in June 2015. The trench is roughly 1.6m deep, 8m long and 50cm wide. I make it roughly 6.5 cubic meters. It was mixed on site and having discussed it with my current builder i now know that means the mix is likely to be inconsistent. I arranged for my structural engineer to inspect the footings early next week and I hope to know more then.
 
The foundations must be poor, due to lack of cement for you to dislodge any of it without a sledge hammer. Years ago my Mother had an extention built by a similar crooked builder. Years afterwards were were discussing foundations, and she said how much earth are you putting in the mix? Err, none. So she gets a ten year old diary and finds the right date, " Colin filled the foundations today, one shovel of earth , one shovel of cement, one shovel of earth. . . ". There was no insulation in the walls, he just moved the batts up at the end of the day and no roof insulation..
You are wasting your time and money trying to get recompense. Just put on 6" of proper C40 concrete with rebars, your builder could do it in a day. Chase him for the money afterwards, Keep the old lump(s) of concrete, one can dissolve the cement out with acid, so by weighing it before and after, you can work out how much concrete there was in the sample.
Frank
 
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The final mix of concrete to finish the top is not necessarily indicative of the rest of it. You will need a core sample to determine if it is.

You can't rely on building control to certify any material. They rely on you doing what you said you would do, and using what you said you would use on the approved plans.
 
There is no way 6.5 cube mixed on site will be any use at alll unless there was gallons of retarders added which will badly affect the strength.

If someone is daft or tight enough to try and handmix that quantity it sounds major alarm bells over their competence.
 

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