Concrete Advice

[sam8364]

Problem solved I think as the quote for option 3 the super C50 mix came in cheaper than even bog standard concrete - I even asked them to double check.

So - what is the technique for pouring the stuff? How does tamping down work? How do you finish off the top nicely?

Also I want to sink four metal fixings into the concrete before it goes off - the will be screwed into a wood board to get the spacing right - at what point do I put these in?

 

[Deluks]

Took you this long to dig the hole, were you digging with the tide in??

I thought you were going to mix by hand, or are the concrete company able to unload on the beach???

You basically chuck it all in the hole and poke it about til the air comes out. You can get a mechanical vibrating poker for this, it might be worth hiring one as you really don't want any voids in that sort of environment. See if the concrete company can supply one.

Tamping is basically tapping the top with a length of 4x2 timber or whatever with a bloke on each end, moving along slowly with a tapping/sawing motion to get it level. You'll probably manage it on your own though for such a small area. If you have a trowel then you can get a smooth(ish) finish with that.

Stick the bolts in when you've finished working the surface, with a slight wiggling motion. (The bolts that is, not your ass)

Most importantly, KEEP IT MOIST! Cover it after it's been worked to keep the moisture in. If it's a hot day, keep a watering can with sprinkler handy and give it a light shower every couple of hours.
Shrinkwrapping a sheet of polythene straight down onto the finished surface is another way to prevent it from drying out too quickly. You can peel it off after a week or so.

Lining the bottom of the hole with some empty polythene sand bags/rubble sacks will also help prevent losing any moisture into the ground during the first 24 hours or so.

 

[noseall]

So - what is the technique for pouring the stuff? How does tamping down work? How do you finish off the top nicely?

The pouring is done by the lorry, he will send it down his chute into the shutter. The main body of concrete is best vibrated to rid the concrete of unwanted air. The surface should be tamped, then ruled off and finally rubbed up and trowelled to achieve a tight finish.

You may achieve a good finish to the surface but any sides that are in contact with the shuttering are likely to be pitted.

Also I want to sink four metal fixings into the concrete before it goes off - the will be screwed into a wood board to get the spacing right - at what point do I put these in?

The fixings should be placed into the concrete sooner rather than later as it will go off quicker than you think, particularly below the surface. Try and ensure that they are seated perpendicular (upright) as this is difficult to correct once they are below the surface.

 

[sam8364]

Thanks for the advice chaps.

To answer the questions....

1. Only took 4 hours to dig the hole - just took me several months to get around to it.

2. Discovered it was only going to cost about £60 more to get it delivered with some special technical mix than do it myself.

3. Going to have to barrow it to the hole about 20m across the beach - luckily there are a line of paving slabs most of the way.

4. All but the top surface are underground so the finish is not too much of a problem.

Some more questions.

I do not have easy access to power so a mechanical poker may be a problem. What is the best sort of tool and technique for doing this by hand?

Cheers

Sam

 

[noseall]

I do not have easy access to power so a mechanical poker may be a problem. What is the best sort of tool and technique for doing this by hand?

Cheers

Sam

Hire a petrol one. Personally i think pokering may be overkill.