bricks

[adder1969]

Hi, I'm building a retaining wall in my garden and I've seen these bricks on ebay

was wondering if anyone here had any comment about the white marks on the bricks. Is this effloresence? Do all bricks do this or is this a sign that these are not of low salt content thus I would need to use sulphate resisting cement? Does the white go away once washed off?

My other easiest option is just going to my local wickes but I'm not really sure of the rating of their bricks either other than they say they come with a "frost guarantee".

Am I worrying too much?

[The Natural Philosopher]

Just leace it for a year. It washes off.

Its a sign thet the bricks are wet and porous: Salts leach out of the cement and migrate by osmosis to the surface of the brickwork

Eventually the rain will wash them off, or of an instant result is needed use brick acid.

Frost guarantee generally means they are of sufficielntly low porosity not to retain mositure in the surface layer, where it can freeze and lead to surface flaking.

Thse will be better at efflorecsence, but probably still shhow it. Frankly, with todays climate, I would not worry.

I had my new chimneys covered in it. Two years latyer no sign is left.

[adder1969]

These (the ones on ebay) are allegedly engineering bricks and haven't been layed but in any case I doubt the latter part is true. AIUI the salt is in the bricks themselves.

[Mary Fisher]

It is but I'm surprised it's on engineering bricks.

Mind you, I'm not an expert on bricks except that as a child we loved licking off the efflorescence from bricks on the lavatory yard wall. There was no dpc and a garden behind so the white stuff wasn't just at a low level and our little tongues could reach it easily.

I occasionally still have a taste when I see it and don't have to bend down (ouch!).

Mary

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[adder1969]

Hopefully above p!ss height too!

[Jeff]

Best laugh I've had for a while :-) I was going to ask what it tasted of as well

Regards Jeff

[Mary Fisher]

Well, since I've never tasted p*ss I can't compare.But if mine tasted like the efflorescenceI think I'd be worried.

Efflorescence tastes sharp, acidic. Makes the salivary glands work. Remember Fenning's Fever Cure? No, probably not. That was 3% nitric acid and I loved it. I also like very dilute hydrochloric acid. Sulphuric never did anything for me. Oxalic's not too bad ... carbolic's tame.

Mary

[Dave Stanton]

Its not salt as you think of it, but salts ie chemical compounds formed from the reaction of acids and alkalis.

DAve

[The Natural Philosopher]

I am not so sure.

Bricks are stored ourtside for many months, but I have never seen them leach salts until they are laid with cement.

I laid some that had been outside in teh rain for 50 years. They still leached after laying.

[doozer]

I thought bricks had to be dry before laying or the mortar wouldn't stick to them properly. AIUI the dryness of the brick draws in some of the fluid from the mortar (along with some mortar particles) to producing the bond. I've not laid bricks though so I might be speaking from the wrong orifice.

[Rob Morley]

You've got it the wrong way around - if a brick is bone dry it will draw the water out of the mortar, so the mortar dries before it's had a chance to harden properly.