Had horrendous weather here for weeks but really need to get my paving laid so planning on hiring a mixer tomorrow.
Just looking for some mixing advice as never used a mixer before.
I plan to use a moist mix at 1:6 (although have more cement here if I need to make it stronger?)
My query is really about the amount of water per mix, I plan on using buckets to make sure I have accurate amounts in each mix. I guess you add the plasticiser to the water stick that in the mixer then add half your sand, full amount of cement then the rest of the sand.
How much water do you start with? half bucket or just a few litre's. I get that the sand will already have water in it, especially with the rain and the sand at the bottom of the bag will hold more water but just looking for ball park amounts.
The mixer is likely a belle 150, I get that you watch your mix to check its the right consistency and slump etc but just curious how long it normally takes to mix up a batch, guessing only a few minutes? don't want to leave it mixing to long in case that weakens the mix.
What sort of coverage does a mix usual cover, my mortar is 50mm deep, guessing that only covers enough for a few bits of paving?
Also noticed on videos I have watched showing laying sandstone that although they say the mortar is 50mm is looks much more, guessing that's the plasticiser making it fluff up?
Finally question honest I have my sbr to put on the back of the flabs as I lay, is it just a thin coating or do you pump it on?
Just add the water as necessary until you get the consistency that your happy to work with. There's no real science behind this other than the fact that mortar needs some water to enable it to set.
Some prefer a wet mix, others a semi dry, just go with what feels right for you.
A mix of 12:2 will do at least 1m2.
SBR mixed with cement to form a runny cream paste works best. Don't worry about covering every inch of the slab just get some on it.
Half-a-bucket of water with plasticiser and any other additives (such as SBR) to start. Then add dry ingredients (sand and cement) and allow to mix, add more water as necessary, say half-a-litre at a time, until you get the desired consistency.
If you are mixing using aggregates from placky bags or even a bulk bag, you *cannot* expect to achieve identical results by accurately measuring the quantity of added water to each batch. Some bags will be moister or drier than others; the sand at the base of a bulk bag is nearly always wetter than that at the top.
It comes down to using your eye to judge just when you think you have the consistency you require.
As for the bond bridge SBR, aim to cover as much of the flag base as possible, but don't worry too much about achieving 100% coverage. As long as you get more than 80% coverage, you'll be fine.
Thanks guys, got the rest of the type 1 in and wacked, got mixer delivered but not till half 4 this afternoon so will be mixing first thing tomorrow. I have got my 3t sharp sand waiting and going to just use sbr slurry painted on the slab as I lay rather than putting it in the mixer as expect that would reduce my working time. That said now the base is all sorted I reckon the paving will go down a lot faster than I expected, if it does I will add sbr to my mix as well as priming the slab.
Just thought of a final question oops lol. I have a few steps into my garage that I will be paving, the tread of the first step is level with my patio. I will also be putting paving on the risers, I was thinking that the overhang should be about 25mm longer than the riser, is that what you guys would normally do?
25-30mm with a drip groove cut into the underside of the overhang tread, about 15mm from the face of the riser. There's a cross-section drawing here which shows the basic principle.
Thanks I actually done the first step yesterday before I seen your reply, I left it 25mm over what will be the riser height but I didn't do a drip groove, will sort that before I do the riser's and other couple of steps
I have my sbr to put on the back of the flabs as I lay, is it just a thin coating or do you pump it on?