Dry Concrete base for fence posts

[acideraser]

My neighbour hired contractor to do fence and we share costs for my side.
Yesterday noticed that on one side where they put up concrete posts already they using mix of cement and sand with ballast without water - dry cocnrete. I was under impression it should be poured concrete instead as this is how existing posts have been done.
Just wondering if this is normal practice to use dry cement for the base or they are cutting corners ? Also worried that with dry cement posts will may fall in strong wind?

Thanks!

 

[JohnD]

was the ground particularly wet there?

 

[Doggit]

Someone may know better, but I've never seen that before. Not sure if they think the water from the ground will permeate the mix, but it won't the outside will set, but stay dry in the middle; they should be using postcrete which will go off and hold the post rigid so they can go on to the next post with confidence it'll hold.. Best to go and query it, and withhold you're payment till you're happy.

 

[JohnD]

sometimes you use drylean mix in the bottom of a damp excavation, it soaks up the moisture and gives a firm clean bottom that you can pour your mix onto, but it won't have correct strength because it flies in the face of correct mixing.

 

[acideraser]

it started to drizzle couple times during the day but don't think ground was wet

Will speak to them tomorrow but thought I better ask people here first as maybe it is common practice these days.

 

[r896neo]

Many contractors, including myself sometimes use semi-dry concrete which is delivered from the plant or collected in a trailer etc. This may look dry to the naked eye but once compacted Will form a normal concrete plenty strong enough for fence posts . This makes it easy to work as posts can be installed and the semi dry rammed in which holds the post level. As the day progresses a water can poured over each hole is more than enough to ensure a good set.

The flowing wet concrete most people see is no use for setting posts as it is too fluid, You'd be adjusting the posts for hours.

Semi dry concrete like i described is far stonger when set than postcrete.

 

[Doggit]

Interesting method R8; but if you were knocking up your own mix, do you know the ratios, and how do you know when you've added enough water.

 

[Newboy]

Is it possible they were using postcrete? - it would look like they were pouring a dry mix into the hole

 

[r896neo]

Basically whilst it is not much help to anyone else I know because i have spent years making concrete and know when its wet enough. The cement needs to be mixed with enough water to start it going off but dry enough that you can hammer it well and not have it ooze everywhere, Best way to achieve this is by adding the water then most of the gravel and some sand then cement and then dry it up with the end of the sand and gravel.

The same mix you would use for laying kerbs.

In reality most people collect or get it delivered as it is a pain to make and makes a mess of your mixer. Buying concrete from a plant especially if you collect it is pretty much the same price as just buying the materials needed to make it, never mind the mixing time etc.

 

[acideraser]

Thank you for the input.
Asked the guys to use wet concrete for posts on my side of the garden, and checked yesterday they have done it, so all good now.
Good that I spotted it though...