Homebrew Mortar Ingredient Specifics UK

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To make mortar for a brick dome.

FIRECLAY
Got some of this:
https://www.potclays.co.uk/clays-sli...eclay-320-(pwd)

LIME
Will get some of this:
https://www.travisperkins.co.uk/ceme...-25kg/p/740142

CEMENT
Which of is the correct cement, if either:
https://www.travisperkins.co.uk/ceme...-25kg/p/846581
https://www.travisperkins.co.uk/ceme...-25kg/p/550548
Can't find UK suppliers who describe their product as simply Portland cement.

SAND
I think all the choices are: sharp (most sources I have here are a bit too coarse), plastering/rendering, building (soft) or silver/white (too fine?),
or even kiln-dried (don't know if classed as sharp/washed or soft but I think it's too fine - although I have some spare bags in the cellar)
I was going go for one or a mix of these:
https://www.travisperkins.co.uk/trad...-pack/p/996239
https://www.travisperkins.co.uk/trad...-pack/p/996241
https://www.travisperkins.co.uk/trad...-pack/p/996272

• Any advice on which UK-available cements & sands are appropriate would be very helpful.
Also, if nobody out there can comment on these specific sand products what are the general principles of what kind of sand is best for homebrew mortar?

• Can you chuck this stuff in a concrete mixer (any plasticiser/admix?) or do you need to use a paddle and bucket like with tile adhesive?

Sorry if all of this has been covered elsewhere I haven't been able to come to firm conclusions from what I have found so far.

[david s]

The homebrew is a pretty forgiving mix. Virtually any powdered clay will do, but avoid Bentonite as it’s extremely small particle size leads to excessive shrinkage. The high clay content in the mix does a great job of making the mix sticky, it is better to mix by hand in a barrow rather than a mixer.
Getting the correct amount of water in the mix is very impoortant. The correct amount is when you’ve achieved “ball up” consistency, ie a cricket ball sized handful thrown 2ft in the air and caught again stays in a ball. It is also important to add the polypropylene fibres and mix them in really well for full dispersion.

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I'm making mortar not a castable material, I presume the cricket ball test is not appropriate.

[david s]

My apologies I was getting you mixed up with someone else who is casting. Skip the ball up test. You want fine sand for mortar, or sieve out the coarse stuff if you have coarse sand. You will probably find it better not to use a mixer as the high clay content makes it very sticky. Probably better to mix in a barrow with a trowel in small batches. Because of all the brick cutting required you really need small batches anyway. You can also skip the polypropylene fibres as well, although I don't as you can make a good case for their use with such thick mortar joints on the outside. They do also work as a binder to hold the mortar together when wet, bu t requires extended mixing time for their good dispersion.