Concrete joints

[loudog]

Hi Guys

I have done an area of concrete approx 180sqm. I have put joints in it but I am going back to fill the joints. My questioin is, I want to fill them with a mastic gun but what product would you recommend. Also, I would like to get it from screwfix as I don't really have time to go and get it, so need a quick delivery.

Cheers everyone

[local patios and driveway]

Screwfix dont sell a polysulfide sealant im afraid.

Try uniseal

[Mikey_C]

toolstation do Polysulphide Sealant, and are much the same as screwfix i.e. will post it out or collect from there trade counters

see here about 3/4 of the way down

[lutonlagerlout]

polysulphide is blinking expensive ,1 tube at 15 mm deep and 10 mm wide does about 2.5m
plus it never really sets
can you not use bitumen or something lou?
LLL

[Dave_L]

How deep are the joints? I guess they are 20mm wide? Fill the joints with a 6mm grit to almost flush, tape the joints to give neat edges and hot pour bitumen them. Job done for reasonable money.

[DNgroundworks]

Ive hot poured bitumen before where we laid a new kerb line up to existing tarmac that we cut back and left and inch or so joint.....anyhow pouring the stuff wasnt as hard as you would think but..................we did set the tar boiler on fire and couldnt put the bugger out for hours!!

in the end we found what we thought was a barge pole and lifted the lid on, then we all rushed in and piled concrete blocks on the top haha great day

[loudog]

hi, sounds like a lot of fun, the joints are still filled with the shuttering wood which the concrete plant said to leave in and then chisel about a inch out and then mastic. Seems a bit of work to me and doesnt seem right. He said the wood will rot after time. joints about 20mm wide. When i look at othe concrete works, it seems they put a grey mastic in there

[oioisonnyboy]

Sounds very dodgy to me ??? Who poured the slabs, yourself or did you get a contractor in?

Good practice is to remove shuttering and then use a compressible filler at joints between slabs...this is either polystyrene, foamrubber or bitumen impregnated cardboard/cork. These jointfillers are designed so that if properly installed the top 20mm peels off to leave a gap for mastic.

If the joints are properly formed with dowel bars and a well formed edge then you dont necessarily need joints along the length of the slab (longitudinal joints) but always advisable at the short sides (lateral joints)

Also depending on the size of the bays in which the area of 180m2 was poured, you may also need to cut some joints to induce the concrete to crack in the correct place.

The grey mastic you have seen is probably sikaflex 11 or a cheaper alternative called arbothane, your local heavys builders merchant will probably stock this but it is not cheap.

[oioisonnyboy]

oops my bad...you poured the slabs yourself. :O

Before sealing rake out all the joints, brush out with a stiff brush and warm the sealer up before you use it as its much easier.

Don;t lick your finger to smooth it, use a round nosed guaging trowel and dip it in neat fairy liquid to trowel smooth.

[lutonlagerlout]

oops my bad...you poured the slabs yourself. :O

Before sealing rake out all the joints, brush out with a stiff brush and warm the sealer up before you use it as its much easier.

Don;t lick your finger to smooth it, use a round nosed guaging trowel and dip it in neat fairy liquid to trowel smooth.

good tip,we use a marshalltown jointing iron and fairy
the finger and spit is a fail routine
LLL

[Dave_L]

Definitely take the wooden shutter out, fill with stone and then bitumen, no too hot to get a nice clean controlled pour.

Job done and not too expensive. This proper jointer is stupidly expensive!

[lutonlagerlout]

think we pay around a fiver a tube for polysulphide
that tube will do 2.5 m of 10mm by 25mm deep
EXPENSIVE!!!
LLL

[Elite Crete]

Polystyrene backer rod is standard practice. Those joints need to be honoured and you need to allow for movement in the slab or you're going to find some ugly looking cracks making an appearance in the future.