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Posted: Sat Dec 06, 2008 10:52 pm
by DNgroundworks
Hi all,
Just had an enquiry for an access road which runs against the front of a garage ( actually will be in contact ), it is about 30 cube concrete. My question is does the concrete need expansion joints even though all the other edges of the concrete are not up against anything solid ( just earth )?
Another question when concreting large areas such as farm yards etc, is it ok to leave the timber formwork (25mm x 200mm tanalised timber )in the concrete once it has set if two adjacent sections have to be concreted in the same day? i only ask due to seein a contractor doing this!
thought id ask before i quote.
Cheers
Posted: Sun Dec 07, 2008 8:14 am
by seanandruby
you will need a movement joint every 3000 metres or more depending on thickness of the intended slab. no its not ok to leave any timber in joints. are you sure it is'nt fibre board for the movement joint ??? you would normally do slabs hit and miss, or wait a day or so till one goes off. as it is a farm track he probably is'nt too bothered to take out the ply.
Posted: Sun Dec 07, 2008 10:27 am
by GB_Groundworks
remove the shuttering and pour your slabs alternatively so no two slabs butt up to each other then use an appropriate expansion joint material.
see
http://www.pavingexpert.com/concrete.htm
there was a picture on the main site that showed how to layout a big pour into alternate slabs but i cant find it. Tony?
excuse the crudeness of the drawing but this is what i meant
Posted: Sun Dec 07, 2008 12:54 pm
by DNgroundworks
cheers,
with regards to the farm yard scenario, once youve poured the concrete into alternate sections and waited for it to go off, you then concrete the other sections, ive always found this hard work due to having to tamp and screed of the adjacent concrete, any tips ( apart from trowel around the edges )
3000m? thats 3km isnt it? would the basic construction joints that tony talks about on his site be sufficient?
Posted: Sun Dec 07, 2008 4:02 pm
by GB_Groundworks
use a power screed or roller striker on the concrete and for ease trowel off the edge all the way round, if just using an aluminum tamp or wooden one its easier on the smoothed bit then apply brush finished etc depending on the spec.
Posted: Thu Dec 11, 2008 12:08 pm
by Tony McC
I suspect Sean meant 3000 millimetres (3m) rather than 3000 metres!
The usual 'rule of thumb' for movement joints is they should occur at separations not greater than 20 times the thickness of the slab. So, for a light-duty 100mm slab, joints should be not more than 20 x 100mm = 2000mm apart, while for a beefier 150mm slab, the maximum separation would increase to 20 x 150mm = 3000mm