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Posted: Wed Feb 06, 2013 4:56 pm
by steveing
I have had a quote today to do our drive i wanted tarmac but the firm advised against due to the cost and said the concrete would be best. The reason he advised against tarmac is that i have a small recovery truck and when a car is on the truck the weight is about 3.5 tons, he claimed that the tarmac cost would be more then the concrete.
Any advice at the moment they are slabs and the total area is 125 sq mts i wont say what he quoted yet as not sure is allowed
thanks
Posted: Wed Feb 06, 2013 5:24 pm
by cookiewales
I would have said Tarmac would be the cheaper option . Maybe the font do Tarmac . Pic is not cheap . Nor setts but they would be nice
Posted: Wed Feb 06, 2013 6:34 pm
by Carberry
Post the quotes you have gotten and the area you're in, some of the guys here more knowledgeable on tarmac will tell you if it is a decent price or give you an idea of what you would expect to pay.
Posted: Wed Feb 06, 2013 6:53 pm
by steveing
We have been quoted £6900 this is for sub base of 100mm and 100mm spec says P300 and P400 , Re-inf Fibres for the concrete we are in stoke on trent
Posted: Wed Feb 06, 2013 7:03 pm
by TheRockConcreting
steveing wrote:Re-inf Fibres for the concrete
I know we have just had a chat about the use of fibres and why architects use them and the doses they use in large scale factory floors, but it was this type of use i was getting at.
The spec you have been quoted IMO is crap
for a 3.5t load spec should be more like
150mm Type 1
125mm C35 concrete (6% AEA)
A192 Steel mesh and fibres (for plastic shrinkage)
Posted: Thu Feb 07, 2013 9:25 am
by Tony McC
So, what's the diff between a P3/400 mix and a simpler C35?
For a 3.5T load, I'd definitely opt for 125mm concrete, and as it's for a recovery truck, I'd usually recommend concrete in preference to blacktop, but in terms of cost, 125m² of 'mac should be a little cheaper than reinforced concrete. There won't be a lot in it, maybe a grand, but once you go over 100m², mac is *usually* cheaper.
The mac would need to be min 100mm, either 100mm a single base/bindeer course, or 70mm binder with 30mm surface/wearing course. And that assumes you are not using trolley or bottle jacks.
Posted: Thu Feb 07, 2013 9:49 am
by TheRockConcreting
Tony McC wrote:So, what's the diff between a P3/400 mix and a simpler C35?
A P300 is a cement content of 300kg/m3
C35 has more cement 320kg/m3
Posted: Thu Feb 07, 2013 9:56 am
by TheRockConcreting
The extra 25mm of concrete from 100-125mm adds an extra 50% strength without taking into account for ground.
Posted: Thu Feb 07, 2013 10:45 am
by Tony McC
TheRockConcreting wrote:A P300 is a cement content of 300kg/m3
C35 has more cement 320kg/m3
That's what I thought - there's not a lot in it, in terms of cement content, so I wondered whether there was something about additives, entrained-air, agg type or summat else that warranted the distinction.
I really do need to update my knowledge of concrete mixes. It all started to confuse me when they switched to the Euro-codes a few years back, and exercise I felt benefitted bureaucrats more than the trade itself. We knew where we were with, say, a C35 50mm slump, but once they started with the split references, it just made me nod off!
Posted: Thu Feb 07, 2013 5:42 pm
by Brucieboy
Jay’s sound advice of a C35 concrete incorporating AEA (air entraining admixture) will give you an external slab for a house drive that should last a lifetime (obviously assuming everything is done to the book).
This exceeds the British Standard (BS 8500) requirement for such an application. For house drives and domestic parking the BS requirement is a PAV1 which is a C30 concrete incorporating AEA with a minimum cement content of 280 kg/m3 and maximum water/cement ratio of 0.60. This has been in place for many years.
However, what has been amended in the BS in the last few weeks is the requirement for a PAV2 – concrete for heavy-duty external paving with rubber tyre vehicles (basically external slabs trafficked by HGV’s). Note, it does not cover the more extreme applications such as certain scrap yards, foundries or busy public roads – in such cases specialist advice should be sought. The specification has now been upgraded to a C40 concrete (it was C35) incorporating AEA with a minimum cement content of 340 kg/m3 and maximum water/cement ratio of 0.45.
The minimum air content for both PAV1 and PAV2 has also been increased from 3.5% to 4.5% by volume for 20mm aggregate. Most ready mix suppliers will target 6.0 to 6.5% to ensure they do not fall foul of the minimum. The slump class for PAV2 has also been increased from S2 (70mm) to S3 (120mm) to cope with the mix being more difficult to lay. As a consequence of the higher specification, the batching cement content is likely to be circa 350 – 390 kg/m3 depending on cement type and quality control criteria and therefore the mix will be fairly “sticky� and prone to “go off� quite quickly, particularly in warm, windy weather.
The reason for PAV2 being upgraded is that the last few winters have been quite severe resulting in many external slab failures, particularly yards trafficked by HGV’s such as distribution warehouses etc.
The BS also states that neither RA (recycled aggregate generally originating from construction demolition waste) nor RCA (recycled concrete aggregate) can be used in any % in PAV1 or PAV2. The aggregate must also be freeze-thaw resistant.
Ps, I agree with Tony’s comment that concrete is far more complicated now than it was. When I first started in the ready mixed concrete industry many years ago there used to be about half a dozen mixes such as 1-2-4, 1-3-6, 1-1.5-3, 3000 psi (21 N/mm2) and 4500 psi (35 N/mm2). Now we have thousands!!! The only significant benefit in change is that the vast majority of concrete is now batched by computer rather than someone pulling levers or pressing buttons.
Posted: Thu Feb 07, 2013 6:51 pm
by steveing
Thanks for all the help what about the price is it about right or what anybody in the stoke on trent area you can recommend
Posted: Thu Feb 07, 2013 7:34 pm
by lutonlagerlout
if you upgrade to jays mix the concrete alone will probably cost in the region of £1300 ,plus a grand for stone, then dig out etc etc
so £6900 looks a fair price for the new spec
btw sorry to hijack this thread but saw a 50 year old groundworker yesterday , been at it for 35 years and was driving past our job
he stopped for a chat and I asked why he wasnt working?
he got out and dropped his kecks
he had 1st degree burns all over his legs apart from 2 squares where his kneepads were
he was wearing trousers and he still cannot work out why this particular batch did this
but a good warning anyway
wet concrete can burn
LLL
Posted: Thu Feb 07, 2013 8:12 pm
by TheRockConcreting
lutonlagerlout wrote:cannot work out why this particular batch did this
but a good warning anyway
wet concrete can burn
Might have been a silicon mix, nasty.
Posted: Fri Feb 08, 2013 9:34 am
by Tony McC
My favourite "concrete finishing" photie....
Posted: Fri Feb 08, 2013 9:43 am
by cookiewales
good job that was not me would have you all laugh ing :p flat on me face 