avoiding efflorescence

[Symptoms]

noseall wrote: "People who have never laid dry bricks, wet bricks, hard bricks, porous bricks, had to muck up, screw down, corbel out, over-sail, lay in the rain - these are the people who blather on about using rinsed sand." That's a bit snide, anyway my post was about 'washed' not "rinsed" - there is a difference.

The OP asked about a guarantee againt efflorescence, and whilst there can be none, there can be steps taken to minimise the risk - hence my suggestion to "also consider using washed sand." He didn't ask about the workability of the mortar.

Using a washed building sand (not plastering or rendering sand) WILL minimise the risk, especially a sand that's been through a scrubber-mill, as opposed to one that's been passed below a spray bar; the significant quantities of soluble salts, silt, and clay often present in unwashed sand may well add to the efflorescence risk.

Maybe, the legions of the calloused handed, ar*e hanging-out-of-the-trousers, wolf-whistling brickies who're on piecework for volume housebuilders don't much care what type of sand is in the mix so long as they can slap it on. However, our friend DIYedboy is aiming for more exacting work and should CONSIDER (not must) think about sourcing 'decent' sand.

 

[noseall]

Maybe, the legions of the calloused handed, ar*e hanging-out-of-the-trousers, wolf-whistling brickies who're on piecework for volume housebuilders don't much care what type of sand is in the mix so long as they can slap it on. However, our friend DIYedboy is aiming for more exacting work and should CONSIDER (not must) think about sourcing 'decent' sand.

Touché.

 

[DIYedboy]

I'm with you Symptoms.............I'm up for some washed sand even if it's harder to use (I'm assuming it will be less workable). Thing is, I've never seen bags of washed building sand in any builder's merchant's.................so can I get it in DIY quantities or does it only come loose on a lorry?

 

[noseall]

You can lay with rinsed sand but the penalty is a reduced working time.

There are also other factors that make using rinsed or washed sands less desirable for a professional bricky who needs to earn a crust from bricklaying.

I agree though, if you are just a diy plodder, then ok.

If the bricks are porous you will need to wet them first. If it hot dry and sunny, then soak 'em. Soaking the bricks though has a detrimental effect regards efflorescence.

The problem is, if the muck dries out too quickly (which is a problem with rinsed muck) then you may lose cohesion. Also it is easy to nudge a brick off its bed when tapping level and it not regain any cohesion.

Its your choice. you could try mixing a loamy sand and a rinsed sand with a good dollop of plasticiser.

 

[DIYedboy]

Nice one Nosall, as you say, as a plodder, I have all the time in the world, I'd rather spend all evening laying a few bricks than watchin eastenders etc. I'm going to use a brick with only about 7% water absorbtion so this should help I hope to stop the mortar prematurely drying out and I presume this will also help efflorescence as the brick won't suck up a lot of moisture to bring out the salts..............or am I wrong?

 

[jdw0624]

Products that are designed to repel water or minimize water intrusion can certainly help but they are rarely a permanent solution. The ideal solution would be to include an admixture in the cement/masonry mixture at the batching/mixing stage. Fortunately, there are some (admixture) solutions you can use to permanently stop efflorescence from "leaching out" and manifesting itself onto masonry surfaces. You need to use an additive that, when mixed with the cement, chemically reacts with and binds the salt based impurities when hydrogen (H) is present. These types of products will fuse the sodium and convert it into non-sodium material and other harmless matter that will not leach out over time. Some products out there even use nanotechnology to react with cement chemicals at a nanomolecular level. Again, reducing the water with a silicone or silane product can help. But it's only a temporary solution. You want an admixture that actually reacts water (H2O) to produce the permanent results you're after. Hope your project is a success.