Mortar mix for retaining wall?

[julianf]

I've done a fair bit of lime plaster, gypsum plaster, concrete, stone walls... But zero block work.

Need to build a very small retaining wall. This is the job -

The posts are set in concrete, which goes down below the new concrete level, by, i think, somthing like 8". There's steel in the new concrete base, and the soil is very stable anyway (job has been as in the photo since last year, and you can see virtually nothing has fallen through!) but id like the retaining wall to bond in with the old post concrete to keep it all stable too.

The soil level on the other side is at the bottom of the lowest rung - so it's not like the fence is holding back mass really.

My plan is to do 4 courses of blocks, obviously with the joints staggered, not like the photo!

The post hole concrete will stay, so I'll build around them.

I then thought I'd chuck some steel mesh in the remaing 4" or so gap, and pour concrete in there too.

But on to my question -

Do you use sharp or soft sand for retaining wall mortar? Or a mix? Google is inconclusive.

Probably thinking a 1:3:1 mix (cement:soft:sharp) - does that sound about right?

 

[Parm]

I’ve built a few wall like this in my old house, always used 4:1 with ordinary building sand

Never had any problems

 

[Dcal]

Sharp sand (plastering sand) is better.
The finer the sand the greater the surface area of the sand particles and the more cement you need to coat and bond the sand together.

Having said that for the job you are doing I wouldn't worry too much.
Use what you can get, 1:3:1 will be fine and the resultant mortar will be far stronger than the blocks.

 

[gaz1]

3x1 or 4x1 mix is fine i use 5x1 for inside walls prefer more cement for outside

 

[julianf]

Use what you can get, 1:3:1 will be fine and the resultant mortar will be far stronger than the blocks.

Isnt exactly what's not intended? I thought that the mortar was always supposed to be weaker than the blocks?

I should raise the point also, that id like the wall to stop the posts of the concrete fence moving also - not just hold back the soil. I wont be able to bind onto them really, but im hoping the whole lot will stick together a bit.

 

[grim_d]

Soft sand for mortar, I use 3:1 or 4:1 usually depending on what it is, usually the bag of cement has mixes on the back of it, the lafarge paper bag does anyway.

If you can get a hold of some plasticiser it makes a huge difference to mortar.

Make sure to mix it well..far beyond what you think is mixed.

 

[Burdekin]

Soft sand for mortar, I use 3:1 or 4:1 usually depending on what it is, usually the bag of cement has mixes on the back of it, the lafarge paper bag does anyway.

If you can get a hold of some plasticiser it makes a huge difference to mortar.

Make sure to mix it well..far beyond what you think is mixed.

Yep soft/builders sand, not sharp sand for mortar.

 

[julianf]

Soft sand for mortar, I use 3:1 or 4:1 usually depending on what it is, usually the bag of cement has mixes on the back of it, the lafarge paper bag does anyway.

If you can get a hold of some plasticiser it makes a huge difference to mortar.

Make sure to mix it well..far beyond what you think is mixed.

I sprung for that cement with the admix in it - its a quid more per bag, but i find that it cuts down the labor so much, as, when you chuck it in the mixer, it seems to "want" to go into a soup, rather than balls.