Slip Form Gate Pillars

[Onoff]

Maybe it's the whole Haloween thing but I'm back to thinking about my as yet unbuilt gate pillars. This was the original idea:

 

 

Well, the I eventually made the gate. Finished in satin black Bedec barn paint.

 

But the pillars.....we can't decide on bricks. We want for definite, inset flint panels and both like Gothic styles. Think gargoyles on top!

 

I'm thinking that it would be perfectly feasible to cast in situ, semi hollow pillars or even solid concrete ones using the 100x100 steel boxes that currently act as the gate posts as guides/formers.

 

 

I've experimented with a few bricks blocks:

 

 

I'm favouring the hollow idea - fab a wooden inner column then an outer one to give say a 100mm thick "wall".

 

Or do I make a small, true slip form say 3 courses high and do a bit at a time ? 

 

But do I incorporate a mesh or rebar cage?

 

Do I tack on false brick joints to the outer former? I could too, incorporate hanging brakets for the flint panels or slots to slide them down.

 

What mix ,  concrete or a sharp sand mix for finer definition? In one hit? Do I use a poker?

 

Just mulling it all over but I reckon it's a goer. I could  incorporate ducts for all the sensors and lights too.

 

Then paint it or just colour the mock mortar lines?

 

Maybe a test section is good idea?

Edited October 29, 2016 by Onoff

[Crofter]

Wouldn't be a million miles away from the pillars I cast for my house to sit on. These are 400mm each side and the tallest one is about 900mm. I made these in stages:

- footings poured to ground level, with rebar inserted to tie into the pillar

- 'kicker' made up using timber slats, I could probably have filled these at the same time as the footings were poured, as they were only 150mm high. But I only thought about them afterwards.

- once footing and kicker had cured, built formers from ply with timber stiffening. The former was built around the 150mm upstand, and ratchet strapped around it

- poured the pillar and vibrated it with my £35 poker off Amazon

 

The poker was good, only downside was having searched for vibrating pokers online my Google history went a bit funny and started showing me some 'interesting' adverts for a few days after!

[Onoff]

My pillar design needs to be Gothic so I guess it's off to Google "gothic pillar".

 

If I'm casting the pillar then the mix is I guess critical. To get definition on any pseudo bricks/blocks I'm thinking 20mm ballast will be too "coarse" but sharp sand too weak?

 

What mix did you use for your house pillars?

[Onoff]

My pillar design needs to be Gothic so I guess it's off to Google "gothic pillar".

 

If I'm casting the pillar then the mix is I guess critical. To get definition on any pseudo bricks/blocks I'm thinking 20mm ballast will be too "coarse" but sharp sand too weak?

 

What mix did you use for your house pillars?

 

Is this poker any good, just for a couple of pillars:

 

https://www.amazon.co.uk/gp/aw/d/B00R4PH5DE/ref=mp_s_a_1_5?ie=UTF8&qid=1477852870&sr=8-5&pi=AC_SX236_SY340_FMwebp_QL65&keywords=concrete+poker&dpPl=1&dpID=41xbXQwSyhL&ref=plSrch

 

 

[Crofter]

I just used normal 20mm ballast, obviously all you see once the forms are stripped is the smooth face (complete with knots and woodgrain from the plywood). My mix was 4:1.

 

The poker looks identical to the one I bought. I would sell you mine but I'm thinking of using it to make a concrete kitchen worktop, just cos it seems like a fun way to spend an afternoon (other people may have different ideas on 'fun')...

[Onoff]

I've had a look at those YouTube videos where they make concrete counter tops, looks like fun. I think they use a special mix? Mainly American ones I've watched. From memory a guy used silicon in the moulds internal corners to end up with a neat rounded edge.

 

I was considering similar for the pillar's vertical edges but not sure how it would interface with any beading for mock mortar joints. This in lieu of rounded corner bricks which are mega money.

 

Bit concerned about longevity if I cast a pillar and colour fade if I dye the mix. Maybe a coat of Thompson's Water Seal after?

[PeterW]

Unless you cast in one go, dying the concrete will end up a mess ... Small batches are really difficult to get right consistently !

 

Why not block and render ..?

[Onoff]

23 minutes ago, PeterW said:

Unless you cast in one go, dying the concrete will end up a mess ... Small batches are really difficult to get right consistently !

 

Why not block and render ..?

 

Where's the fun in that?  It's "Can I?" not "Should I?"

 

I want it to look like bricks or possibly large blocks with mortar lines.

 

Thinking I'll have a crack making a test former from some moisture resistant T&G chipboard flooring offcuts using vegetable oil as the release agent. That should naturally degrade so I can apply a water seal later on.

 

I can build in pockets for lights, conduits, proximity sensors etc. Thinking to bolt the inner and forms together with stainless studding that would double up as rebar. Some drain tubes too done the same way.