Tools for making paving mortar
- Cement mixer (recommended)
- Wheel barrow
- Trowel
- Spade/shovel
- Garden hose or watering can
Materials
- Sharp Sand / Grit Sand - 5 parts
- Cement (OPC/general purpose) - 1 part
- Water
- Mortar plasticiser (optional) - improve workability
Method
1) Add 3 parts sharp sand and 1 part cement to the mixer/barrow/tub in which you are mixing the mortar
2) Add some water and mix and work together until full mixed
3) Add the last 2 parts of sharp sand to the mix
4) If you are adding plasticiser to you mortar add this now
5) Add water as necessary and mix and work together until fully mixed
6) Tip out and transfer the mixed mortar from the cement mixer to the barrow and rinse the mixer clean whilst the residual mortar is still wet
Safety
- Wear a face mask when pouring cement powder into your mixer / barrow or bucket as its fine particle will be airborne and are not good for your lungs
- Ensure you turn off the cement mixer whenever you work any of the mortar with a shovel or trowel
Advice
For a complete breakdown of how to lay paving slabs see our guide here:
www.pavingdirect.com/info/how...
We recommend a cement mix of 5:1 sharp sand to general purpose/ordinary Portland cement (OPC) as this will provide good strength and bonding. You may consider also adding an SBR bond to the mix to increase bonding, elasticity and reduce osmosis, however this is probably better done via priming slurry painted directly onto the underside of the slabs.
Some landscapers like to swap a little builders’ sand for sharp sand to the mix - this will give the mortar a more pliable texture allowing you to make fine adjustments to the slabs more easily when laying them, but it will slightly weaken the mix. Instead, we recommend using a mortar plasticiser, as this will enhance workability whilst keeping the mortar as strong as possible.
Use sharp sand (aka grit sand) for your bedding mortar mix. Sharp sand is used for the laying coarse mortar mix because firstly, it has improved strength and cohesion. Secondly, it also offers better adhesion and grip to the slabs. Lastly, it also helps prevent insect and burrowing animal intrusions too!
Q: What mix ratio should I use for a patio mortar bed?
A: Use a 5:1 mix of sharp sand to general purpose cement.
Some landscapers may use weaker sand-cement concrete mixes where the slab is slightly porous and the underside is courser and has more natural grip (e.g. sandstone), but this will inevitably make for a weaker bedding layer with weaker bonds to the slabs.
For porcelain paving in addition to a strong 5:1 ratio cement mix for your bedding mortar, you must use a priming slurry to aid adhesion between the bedding mortar and slabs. Porcelain slabs are vitrified (non-porous), so have less grip and natural bonding than found with more porous stone or concrete slabs - so a priming slurry is essential.
Laying coarse bedding mortar should a pliable but firm mix
The bedding mortar should not be too wet, nor not too dry. It should be reasonably firm and hold its shape when you trowel down the laying coarse. It should be creamy and pliable. Ideally you want to be able form small peaks above the line of the laying coarse so when you tamp down the slab into the mortar it creates a full bed and the peaks spread out under the slab.
Q: How wet should the bedding mortar cement mix be?
A: It should be just wet enough to hold the mix together and be pliable.
If it is too wet, when you trowel it down, it will not provide the support or hold the peaks/ridges needed to ensure a full bed from the laying coarse. Additionally, if it is too wet, moisture transfer from the mortar can react with concrete and natural stone (as they are porous), leading to differential weathering, blooming, and soluble crystalline deposit staining.
Consider hiring or buying a cement mixer (mixing the mortar in a bucket or a flexi-tub by hand is very time consuming and labour intensive).
11 окт 2022
