Which dry ready concrete for strong bollards?

I am going to make 2 bollards to protect my trees from cars so as not to be broken. I want to buy a ready dry concrete. Please which concrete is the best to be strong enough to stop the cars?:

Blue Circle Multi Purpose Ready to use Concrete 20kg Bag
https://www.diy.com/departments/blu...MIzMnuhIit5QIVB7TtCh1rrgfIEAQYBiABEgJmL_D_BwE

OR

Blue Circle High strength Ready to use Premixed concrete 20kg Bag
https://www.diy.com/departments/blu...MInOjvsout5QIVgbTtCh1SaAyfEAQYBCABEgJQbPD_BwE


OR

Blue Circle Postcrete Ready to use Concrete 20kg Bag
https://www.diy.com/departments/blu...-use-concrete-20kg-bag/35713_BQ.prd?rrec=true

OR

any other one? Please suggest.

I prefer this because is the cheapest:

https://www.diy.com/departments/blu...-use-concrete-20kg-bag/35713_BQ.prd?rrec=true

But they do not say "High strength (40N)". Or is this the same like this?:

https://www.diy.com/departments/blu...MInOjvsout5QIVgbTtCh1SaAyfEAQYBCABEgJQbPD_BwE


And another question:

Is there any seller who can deliver these a few bags for free to Balham?

Oker,
Am I reading this correctly - "I am going to make 2 bollards" - are you planning on making your own bollards from concrete?

If just planning to use 'postcrete' type concrete to only make foundations for a post, then use any of the ones you gave said. You will get more strength by making base of pole deeper and using more bags to increase foundation size. But note that a car or lorry will damage or knock over a bollard - but that will stop damage to your tree.

If you are planning to also make your own concrete post, then I would suggest - do not do this for following reasons:

0) Postcreat does not make posts, it makes foundation for posts.
1) To make concrete bollard you need cement AND ballast AND steel rebar (you do not use neat cement to make concrete, you must also use stones (ballast) to give it strength and steel to stop it snapping). Note that postcreate does contain ballast (stones), but I would not use this to actually make a concrete post.
2) When someone hits the concrete bollard, it will crack and you will have to start again making a new post - steel posts are better.
3) Dustbin lorries around here hit the steel bollards, and rip them out the concrete foundations. This seems okay as it reminds the lorry/cars to take wider turn, and although they damage the bollard they do not not hit tree/wall/etc. The ripped out scratched bollard is then reset into a new concrete foundation (using postcrete), to continue its protection role.
4) I have no idea what the litigation is when someone hits your bollard with their car. I guess there is a possibility the car insurance could claim against you if you bollard is not properly located.

Suggest you look at purpose made steel bollards, or steel poles, set into concrete foundations:

https://www.ebay.co.uk/itm/Steel-bo...441474&hash=item238cd5f77b:g:-j0AAOSw46BZqUCs
https://www.ebay.co.uk/itm/90mm-Ste...423720?hash=item3645271728:g:KwsAAOSwl-5a0KC8
https://www.ebay.co.uk/itm/Steel-ch...671478&hash=item25defefaad:g:VXYAAOSwJ~RZqV8s

all found using following serach :
https://www.ebay.co.uk/sch/i.html?_...ete.TRS0&_nkw=steel+bollard+concrete&_sacat=0
and
https://www.google.com/search?q=steel+bollard+concrete&safe=strict&client=firefox-b-d&tbm=isch&source=iu&ictx=1&fir=GAw94kyIJMBMpM%3A%2CDwHH1H3YwKB0rM%2C_&vet=1&usg=AI4_-kTFFCSzU07hgxO6ZsVNKOKi3lxDrw&sa=X&ved=2ahUKEwihv6j0ta3lAhVWTxUIHSU5AfMQ9QEwAnoECAQQDA#imgrc=GAw94kyIJMBMpM:


sfk

Regarding delivery, Wickes currently charge about £7.95 if you get their postcrete:
https://www.wickes.co.uk/Blue-Circle-Ready-To-Use-Postcrete---20kg/p/221100

50kg bags willl give you stronger bollards. Especially if you don't use a barrow, but carry them.

is this on your own land?

Go to a metal scrap yard and buy some RSJ's or steel posts, long enough for your purpose plus enough to go into the ground. Just dropped into a hole in the ground, with earth compacted around them, they will provide a deterrent and be easy to straighten if they are hit. Any scrap yard will oxy cut them to length for you.

If you must use concrete posts, them they will need reinforcing rebar in them if you want them to last.

Yes, I want to make my own bollard from concrete.

Yes, I will use 12mm Reinforcement Rods:
https://fulhamtimber.co.uk/12mm-3m-reinforcement-rod-bar/

So, if I understand correctly, I will have to mix cement with the ready concrete from the bags which I gave here the links?


What ratio I should mix these?

Which ready concrete I should use? SEE the links...

What cement I should buy? (please a link)

Should I add gravel, as well, or only the concrete from the bags and cement?

Oker,
I have never made freestanding bollards, only concrete slabs (my drive), or concrete around fence posts.
So I am happy to be shouted down by others:

1) I would not make a free standing bollard from concrete for the reasons I said before, but if you decide to:

2). Postcrete is a fast setting concrete (ie it is fast-setting-cement and stone already mixed together. You dig a hole, put fence post in hole (or the steel bollard I mentioned before), pour dry Postcrete onto hole, add water. This postcrete then sets very quickly (15mins). It sets too quickly to make a free standing post.

3) Concrete for my drive is made from 1 bag of cement and 5 bags of ballast. YOu can get these from wickes and this works out as cheapest method of making concrete. You mix the two together, then add water. and mix again. To make a bollard you would make a wood box (a former), put in the steel (holding it in the middle) and then put in the concrete. Then vibrate box to remove any air holes. Wait 7 days to dry (might be longer than needed but although it looks dry it needs time to get strong) and then take off wood box sides.

4) One of your links was for concrete, which means that it is Cement and Ballast already mixed. So that does save you a step in Process 3 above as you only need to mix in water. But still very hard work.

But again, I am not sure I would be happy to suggest you make your own concrete bollard. It feel you will be on a hiding to nothing.

Otherwise if you want (what I consider difficult to make and ugly) concrete Bollards, why not use reinforced concrete lintels. You could use these lintels dropped in a hole and secured in place using a couple of bags of Postcrete.
https://www.wickes.co.uk/search?text=lintel

[Notes
- you do not add gravel. You use ballast with cement tyo make concrete. Gravel is all one size of stone, so would be weak and expensive as cement would fill all the gaps. Ballast is all the stone sizes up from sand to gravel, and it will fill all the gaps so less cement needed and makes for a strong concrete.]

SFK

Video here that could be adapted to make a taller concrete bollard (pls do not leave a re-bar sticking out like that without a temporary cap on it in-case any one trips and falls on it).:

Oker,
Am I overthinking this (I was thinking of a bollard 100cm high, 10cm by 10cm)?

This OP simply made bucket shaped and sized, 30cm high bollards to stop cars:
https://www.diynot.com/diy/threads/make-concrete-bollard.363289/

What is the Bollard size you are thinking of?
SFK

Knock 2 fenceposts in the ground.
To help them be seen, paint them a bright colour (white), and add a couple of reflectors.

About 20x20x100 cm.
Which my links already include ballast and cement? I suppose all of them?

Thanks for confirming size.

All the ones you listed are all pre-mixed cement and ballast.
For all of them only need to mix in water to make concrete.
You do not add builders sand or pebbles or ballast to any of them.

Note that your favourite is Postcrete which is fast-setting-cement and ballast. As said before it is not suitable for you. It will set very fast.

Sfk

DO NOT USE POSTCRETE TO MAKE BOLLARDS!

just a suggstion

you can purchase recycled bollards from a salvage yard, here are a sample
https://fenori.co.uk/product-category/bollards/
of different types of bollard , not very expensive, by the time you dd up the rods, concrete and time it will take to make