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Wednesday, 22 February 2023 11:58

My Concrete, Mortar, Cement and Aggregate Notes

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All you need to know about concrete

  1. It will always go off
  2. It will always crack
  3. No-one will steal it

Mixes Table

Mix Ratio
(by volume)
Cement/Sand/Aggregate		 Name Generally used for Notes
1 : 2 : 4 Concrete Small slabs, Fence posts
  • a.k.a M15
  • a.k.a C20
  • A good ratio for most general domestic jobs.
1 : 3 : 3 Concrete Slabs, Floors, Walls, footings (foundations)
  • I have used this to do footings for my retaining wall.
  • eg: You would mix 1 shovel of cement with 6 shovels of Pre-mixed Ballast / All-In Ballast.
1 : 2 : 3 Concrete DIY projects
  • This is not an official mix ratio but is easy to remember
1 : 3 : 0 Concrete Mortar Mortaring/Pointing Retaining walls and Chimneys.
  • I have used this to build my retaining wall.
  • It is denser than normal mortar and prevents water ingress.
  • Do NOT use waterproofer or plasticiser with this mortar because it will put holes and air bubbles in the mix.
  • This should be used when the mortar is likely to be constantly exposed to moisture.
1 : 4 : 0 Mortar Bricklaying
  •  This is a standard mortar mix used for bricklaying.
1 : 4
(with plasticiser)		 Scratch Coat
(bottom coat)		 Rendering brick
  • Add plasticiser
  • 10mm thick is best
  • The sand must be plastering sand or rendering sand, not building sand – do not use building sand for rendering because it shrinks and cracks.
  • Some people use sharp sand.
  • Never to make the rendering mix stronger than the material to be rendered.
  • The first coat of render should ideally be slightly stronger than the second coat. While some tradespeople make the two mixes the same strength, the second coat should never be stronger than the first coat.
1: 5
(with waterproofer)		 Finish Coat
(top coat)		 Rendering brick, Pebble dashing
  • Do NOT use building sand for rendering because it shrinks and cracks.
  • The sand must be plastering sand or rendering sand, not building sand – do not use building sand for rendering because it shrinks and cracks.
  • Some people use sharp sand.
  • Never to make the rendering mix stronger than the material to be rendered.
  • The first coat of render should ideally be slightly stronger than the second coat. While some tradespeople make the two mixes the same strength, the second coat should never be stronger than the first coat.
0 : 3 : 3 Pre-mixed Ballast / All-In Ballast Part of the mix for footings
  • You would add 1 part cement to use this for footings (foundations). See above.
  • I think a lot of people shorten the name to just `Ballast`.
  • This ratios are done by volume, i.e. 1 shovel of cement, 2 shovels of sand and 4 shovels of aggregate.
  • The sand is always building/builders sand in mortar and concrete
    • Not all concrete applications can you use building sand.
    • There seems a lot of debate about this
    • I always use building sand in my home projects
    • What Is Sharp Sand? | Sharp Sand Uses | Avon Material Supplies - What is washed sharp sand and why use it? See why sharp sand (also known as grit) is ideal for mortar, concrete, paving and landscaping.
  • Plasticiser should only be used with mortars.
  • in the M5, M7.5....., M20 categorisation of the aggregate content seems to always be twice the sand content

Notes

These are my notes on concrete mixes and various project using concrete, mortar and cement.

Read 821 times Last modified on Sunday, 22 October 2023 10:17
Published in House
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