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Posted: Thu Jan 17, 2013 11:58 am
by Grandunion
Good morning. I have been looking into building a new kennel block for my dogs & the obvious solution seems to be a concrete base. I am looking at approx 8mx3.5m with a depth of 100mm. I have done an estimate and it works out about 2.6mc. Would it need to be reinforced? It will not be bearing much load as the kennel system is prefabricated out of wooden panels & galvanised bars. I would also like a drainage channel towards the front to aid with cleaning etc...it is positioned in my rear garden with side foot access but no vehicle access so I'm guessing either a ready mix with a concrete pump or a team of lads with barrows. I hope I have made it fairly clear and would really appreciate advice about how much it should cost and whether anyone on here knows or can recommend anyone I could contact for a good price. I am located in south Hertfordshire near the M25. Many thanks James
Posted: Thu Jan 17, 2013 12:53 pm
by lutonlagerlout
hi james
PM sent but that would need to be done in 2 bays 8 M is too long for 100mm concrete
also what is the access like from the road?
is there any subbase there?
does the existing ground need removing
cheers LLL
Posted: Thu Jan 17, 2013 1:36 pm
by local patios and driveway
3 men wheelbarrows, pour that lot in an hour easy.
Posted: Thu Jan 17, 2013 2:02 pm
by Tony McC
Posted: Thu Jan 17, 2013 6:29 pm
by TheRockConcreting
Hi James,
Yes you should you steel reinforcement (A142)
If you got a pump in it would work out very costly for that little job.
Concrete C30=£85/m3 +PUMP 32M BOOM+PIPES=£380+VAT
50 Round trips with a wheelbarrow=1L of sweet and yer done. Plus you could save a little on the concrete and get a C20 mix.
Posted: Fri Jan 18, 2013 8:29 am
by Grandunion
Much appreciated for the advice, I'm going to have another good look before the snow comes down today and double check my measurements etc. thanks for the pm and will keep you all updated. I do have off street parking as I have a driveway which can hold 5/6 cars if that helps...
Posted: Fri Jan 18, 2013 9:56 am
by Tony McC
TheRockConcreting wrote:you should you steel reinforcement (A142)
Would fibre reinforcement not be adequate for a kennel base?
Posted: Fri Jan 18, 2013 2:12 pm
by TheRockConcreting
Tony McC wrote:Would fibre reinforcement not be adequate for a kennel base?
IMHO, i don't like using synthetic fibers on their own for hardened concrete crack control, i know 100's do.
I see their use as misinformed, they are great for plastic shrinkage cracking, etc. but there is noway on earth they are going to hold cracked concrete together.
Yeah its only a tiny dog run but still, 2 sheets ain't gonna cost. some firms charge an extra 20 quid a cube for fibers!
I see the fibers as something that should be used with the steel not as a replacement.
Posted: Fri Jan 18, 2013 2:17 pm
by Dave_L
We did a big concrete pour back along (floorslab) where the proposed steel was replaced with fibres - the architect and concrete supplier agreed for the substitution.
Posted: Fri Jan 18, 2013 2:46 pm
by TheRockConcreting
Dave_L wrote:We did a big concrete pour back along (floorslab) where the proposed steel was replaced with fibres - the architect and concrete supplier agreed for the substitution.
Yeah same, i just don't buy into it and always use steel when supplying.
Posted: Fri Jan 18, 2013 3:24 pm
by Brucieboy
TheRockConcreting wrote:I see their use as misinformed, they are great for plastic shrinkage cracking, etc. but there is noway on earth they are going to hold cracked concrete together.
Macro synthetic structural fibres such as Durus (Adfil) and Strux (Grace) are commonly used to replace steel reinforcement on ground supported floor slabs. The fibre supplier normally advises on the dosage, grade of concrete and slab thickness etc. The fibre dosage is usually in the range 4 to 6 kg/m3 compared to 0.6 to 0.9 kg/m3 for the monofilament synthetic fibres used largely to control plastic shrinkage cracking.
Posted: Sat Jan 19, 2013 10:21 am
by Tony McC
My gut instinct is to think "throw in a couple of sheets of 142" but on a job where I'm currently advising on drainage, the builder has put in a base for one of them shed/offices I've been considering and he's used fibres only.
Not my place to say owt to him but I just wondered if the thinking had changed since I last poured a slab, which must be over 10 years ago.
Posted: Sat Jan 19, 2013 10:29 am
by GB_Groundworks
We did that huge NHS pour with the biggest concrete pump in the country and that had metal fibres in, the k deck support, 12mm dowels tied in then 250mm c35 with inch and half long metal matchsticks type.
I always use mesh but for a dog kernel in a good base it's not going to crack if laid properly
Posted: Sat Jan 19, 2013 12:12 pm
by Brucieboy
A lot of the big sheds / warehouses now construct their ground floor slabs (and mezzanine slabs) using concrete containing steel fibres. These are often added to the truckmixer on site (by conveyor or blasting machine) along with a good splosh of superplasticiser to provide the workability needed to place it. Fibre dosages are typically in the range 30 to 40 kg/m3. Now costing about £1 to £1.25 per kg, the addition of steel fibres makes the concrete quite expensive. However, compared to the cost of buying conventional steel mesh reinforcement and the associated storage, cutting, placing etc, overall it works out very competetive for the contractor /client.
Macro synthetic (plastic) structural fibres (typically 30 to 50mm in length x 1mm diameter) are becoming more popular, particularly for the smaller type of building such as a commercial office, school, grain store etc because they're more user friendly, about half the cost of steel fibres and can be added to the truckmixer at the plant (or on site if preferred).
In both the above cases, the fibre supplier must be consulted to advise on the slab design, i.e. fibre dosage, grade of concrete, thickness etc. This service is usually "free of charge".
The main benefit of fibres, whether they be steel or plastic, is they're uniformly distributed throughout the full depth of the concrete, i.e. they're three dimensional. One of the problems of placing steel mesh is keeping it in the correct position within the slab to do it's job properly. I've visited many sites where the contractor has complained that his ground floor slab has cracked because "the concrete is crap" only to find on investigation (generally by coring or using a covermeter) that the crack control mesh is sitting a few mm from the bottom. It should be about 50mm from the top (or within the top third for third for the thicker slabs) if it's to minimise plastic shrinkage cracking.
When monofilament fibres (typically 12mm in length and very fine diameter) are used to replace steel mesh, it's often thought that curing can be neglected. This is a big no no. It's a fact - all concrete will crack. Mesh or fibres just control the width and spacing of the cracks. Plastic shrinkage cracking occurs when the "rate of water evaporatiing from the surface exceeds the rate of bleeding (water rising to the surface from within the concrete). Control this by adequate curing, i.e. spray on curing membrane, plastic sheeting etc, and you will control the cracking. Abuse this and it's likley your concrete will crack (often with widths up to 3 or 4mm), particluarly in warm, windy weather.
I stress the above reference to fibres relates to their use in ground supported or "crinkly tin" (mezzanine) supported floor slabs. Conventional steel bar reinforcement, correctly designed, must be used in unsupported floor slabs.
Posted: Sat Jan 19, 2013 2:24 pm
by Tony McC
I might nick that, Bruce, and add it to the main site, duly accredited, of course!