Mixing mortar

[Vijay]

Evening,

 

Job in a few weeks is to lay 500 odd blocks for my internal walls. I'll be working on my own, so I wondered if anyone can give me any advice on mixing up the mortar. I can use a cement mixer but I'll be laying the blocks at a slower pace, so would it be an idea to mix the mortar in smaller batches, maybe using a paddle mixer and large bucket?

 

Cheers

 

Vijay

[Vee6 dan]

Just tip half out of the mixer at once. I’m a bricklayer and mixing with a paddle mixer tends to over mix. 

[Vijay]

Cheers.

 

should have mentioned I'll be using a genny for power on site. Should I keep the mixer going with the second half?  Can I still over mix by leaving the mixer going?

[Oz07]

No don't leave it going just respin for a bit before you tip out again 

[Vijay]

great  How long is a good time to mix?

[Oz07]

Not a question that can be answered in minutes only in experience. A bit like popping your cherry. You will know when you know

[Oz07]

Btw I think mixing needs to be learnt before laying, although the young brickies nowadays are prob crap at it

[nod]

1 hour ago, Oz07 said:

Btw I think mixing needs to be learnt before laying, although the young brickies nowadays are prob crap at it

Hardly ever see mixers on site now 

Silo or tub 

[Onoff]

5 minutes ago, nod said:

Hardly ever see mixers on site now 

Silo or tub 

 

Tub as in tub of ready mixed?

[nod]

13 minutes ago, Onoff said:

 

Tub as in tub of ready mixed?

Yep delivered 

[PeterW]

14 minutes ago, Onoff said:

 

Tub as in tub of ready mixed?

Yep - 1/3rd cubic metre tubs with a retarder in that lasts 3 days from delivery. Consistent and very good and means they aren’t waiting on mixes. 

[dpmiller]

local concrete guy sends one of his trucks out with mortar each morning to top-up tubs he has out on sites. Whatever is left when the truck comes back is tipped for some of the small businesses to descend upon, vulture-like...

[Gus Potter]

Hello Vijay.

 

Well done getting the tools out. Below is a bit of text from a previous post.

 

"Just on you own with a half bag Belle mixer, a good barrow, under cover, with not too many windows, tricky bits, and loading out the blocks each night for the next day, cleaning the mixer then with this amount of blocks I would go for 150 blocks a day (15m sq) if you are fit and tenatious. Expect this to drop off from time to time, well quite often, go for a hundered a day (10m sq) tops as you also need to order materials etc"

 

Vijay, if you haven't done this before expect to lay say fifty 100mm thick dense block for the first few days.

 

But the mix.. Oz07 @Oz07 is bang on with it being a learning process. Actually, a good labourer used to be worth their weight in gold to a brickie squad.

 

Anyway here are a few pointers.

 

1/ Look after you materials. Get the sand, cover it up so it does not get too wet  / or dry and to stop the local cats / foxes using it as a bog.

2/ Buy your cement in weather proof bags.. may cost a few pence more.

3/ Get some plasticizer for mortar.. 5 litres should about do.

4/ Get a half bag Belle or similar mixer.. bigger than that and you'll end up wasting mortar and having to dump it.

5/ Get two or three mortar boards..  kitchen doors work well, not OSB board as it splinters

6/ Tools.. string line, good bead etc.

 

A bit of technical stuff. Below is some info from a common standard. The key here is to understand what type of blocks you are working with. If the mortar is too strong the blockwork will be more prevelant to cracking. Too weak and well.. that is just as bad as making it too strong.

 

Roughly what you are often looking for is something  around class two to three.. more leaning towards class three for practical purposes above ground.. provided you do you best to not remix stuff and really take care with the mortar, temperature, keeping the blocks not too wet or too dry (not on a boiling hot day or below 4 deg c or falling).. there is a lot too it.. but so long as you do a bit of research you should be on the way to a good job.

 

You can see he above table refers to proportion by volume. This helps. Get a pail and pour half a 25 kg bag of cement into it. Mark the level. Now gently shovel the sand into the pail to the same level as the cement was. Tip it out onto a board and repeat. Now you have a pile of sand. Get your shovel and count how many shovels it take of the same size to move the sand into the mixer... note it down as you are learning. Don't whack the sand into the pail as you are not at the beach. As you go you'll get the hang of judging the proportions so you don't have to use the pail any more.

 

Put half the sand into the mixer, Now depending on how dry the sand is you roughly need about the same volume or a bit less than the amount of cement. For the first mix of the day put the plasticiser in first following the instructions for how much you need for 12.5 kg of cement.. Now add water.. about half the volume of the cement measuring as you go. Now add the cement, a bit more water until it starts to mix and the back of the mixer is clean.. stuff not sticking to the blades... don't put your arm into the mixer.. Add the rest of the sand and very slowly add more water, it comes a point where you only need about a mug full to get it just right. Mixing should take three to five minutes.. don't over mix or under mix.

 

The key to getting start is to make sure it is workable but not over mixed with too much air.

 

It will take some time to learn how to do it but once you get the hang of it it can be very satisfying, so long as you take your time and set everything out carefully.

 

From memory roughly one batch out of a mini Belle ( 12.5 kg of cement) will do about 25 number 100mm thick blocks.

 

Do a bit more research and it's all doable. Lastly, just check that what you are building is a standard wall.. not some kind of specialist engineered wall with high strength blocks carrying high loads.. always check first.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Vijay]

On 07/12/2020 at 21:44, PeterW said:

Yep - 1/3rd cubic metre tubs with a retarder in that lasts 3 days from delivery. Consistent and very good and means they aren’t waiting on mixes. 

 

Don't think tubs will be a real option for me if there's a small shelf life. I'm not on site every day and weather rarely seems to be on my side. Plus add the fact I'll be laying blocks at my own slow pace lol So looks like mixing on site is the best option for me.

 

Thanks for the info Gus. I had in mind that if I can lay min 50 blocks a day, I'd be happy as it's enough to see progress. Any more is just a bonus   You're last point about what type of wall it is, it's a load bearing wall in 7.3nm 100mm blocks

[Gus Potter]

Hello Vijay.

 

Take your time to start with.. get the coursing worked out both horizontally and vertically. Some days you'll get on great and lay lots. Take care with any corners and openings as if it's rough you'll just make a rod for your own back later.

 

A 7 N/mm^2 dense block is fairly standard provided the wall is not to high between points of lateral restraint.. that could be the floors, return corners of a descent length etc. Check your drawings and SE spec. Remember to look after the blocks, specially as it's winter. Make sure you don't lay when the temperature is below 4 deg C or falling.. even inside!

 

All the best.. once you get the bug and realise the savings it can be a very satisfying job.