When to use sharp sand and when to use "soft" sand?

I've always been unsure about when to use the different types of sand. Obviously it's sharp sand for screed and builders sand for bricklaying mortar but can someone tell me why? I'm about to bed a shower tray with mortar (per manufacturers instructions) but can't decide whether to use sharp sand or builders sand - ?
Dave
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I think it's to do with workability: soft sand has many grades of rounded particles, right down to clay. This makes it handle well and you can adjust bricks easily, the mortar made with soft sand supports the bricks but allows plenty of movement if you need it.
Sharp sand has angular grains, less gradation, and I believe makes a stronger mortar, but it won't handle well or have the range of adjustment that soft-sand mortar does. My experience with soft-sand is very limited, but I have a fair bit with sharp sand, and found that if you didn't get the thickness off mortar right first time when bricklaying or laying paving stones on a solid bed of mortar, then if you tap the brick/paving down only a limited amount of adjustment occurs before it locks up solid, then it's take the brick/slab up and start again. It also allegedly doesn't handle well on a trowel. I built a wall using sharp sand as I wanted white mortar, and the local sharp sand is silver, but it wasn't easy.
Supposedly mortar can be made to handle better by using a plasticiser, which is either lime, or a proprietary plasticiser, like PVA or Febmix ( or squeezy if you're a cheapo! ).
I'm not an expert, but bedding something like a shower tray makes me think a mortar that allows a goodly amount of adjustment is best, so I'd try the soft sand. There is a special cement for bricklaying, masonry cement, that does not need additional plasticiser, but if you're using ordinary Portland cement, I think some lime or plasticiser added to the mix will be beneficial ( e.g. 1:1:6 lime/cement/sand ).
PS: I defer to anyone else who's had years of experience in the trade and knows better!
Andy.
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On Sat, 28 May 2005 00:08:15 +0100, "andrewpreece"

Is there any reason why graded crushed glass couldn't be used in admixture with sharp sand?
AJH
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snipped-for-privacy@despammed.com wrote:

I thought that essentially that is what sand actually is.
Why on earth we dont just throw bottles into a smasher and then into the sea and let that do the job of reducing them to coloured pebbles and sand I don't know...
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Philosopher" snipped-for-privacy@b.c says...

Because it's more economical to reuse it as glass?
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Sand and glass are not really the same thing, though sand is used in the manufacture of glass. Sand is mostly the crystalline form of silicon dioxide known as quartz. The yellow/brown colouring comes mostly from iron oxides. Glass is made by melting sand with sodium and other metallic compounds and then supercooling it to form a non-crystalline solid. Glass is not nearly as hard as quartz but the main reason for not using it as an aggregate is that it is much more valuable than sand.
Unless you are being paid for how many zillion bricks per hour you can lay, sharp sand is perfectly good enough for building and the mortar will indeed be stronger than with soft sand. More importantly, if you want to be on the side of the angels, don't use Ordinary Portland Cement at all. Build with lime mortar, a 3:1 sand : lime mix. The best lime to use comes wet in a plastic tub and is called lime putty but a cheaper alternative is the bagged hydrated lime available from all buildres' merchants. Buy it from a merchant with a rapid turnover and empty the bag into a plastic dustbin of water as soon as possible and then use it wet because the lime cabonates on contact with the air.
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snipped-for-privacy@biffvernon.freeserve.co.uk wrote:

Thanks to one and all.
Dave
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Dave wrote:

I used sharp sand to bed the shower tray BUT couldn't get the tray to bed evenly so scraped it all off and tried again with builders' sand - no problem.
Dave
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And keep your work covered for how long to protect it from the rain?
-- I am using the free version of SPAMfighter for private users. It has removed 5074 spam emails to date. Paying users do not have this message in their emails. Try www.SPAMfighter.com for free now!
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On 28 May 2005 05:11:18 -0700, snipped-for-privacy@biffvernon.freeserve.co.uk wrote:

OK so the silica in glass is in mixture with other chemicals which lower its fusion temperature and prevent it forming back to small particles on cooling? It is not strong as silica grains in sand.
Is the strength of silica grains a limiting factor in the properties of the sand?
I continue to ask as my local council has a problem disposing of coloured glass, it going to landfill. There is a market for clear glass but even this does not cover collection costs if my local authority is correct.
AJH
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     snipped-for-privacy@despammed.com writes:

Glass really wasn't worth recycling at all until the landfill tax came in. If you have to start your car engine in order to participate in glass recycling, then it's almost certainly still not worth it. "Driving to the bottle bank" is an expression which is sometimes used to refer to pointless recycling. People are looking around for uses for coloured glass, and new road surfaces is something they are being used on, but I think that's still experimental. Manufacturing and using less coloured glass in the first place is probably a better bet, but people seem to like trying to solve problems at the wrong end of the supply chain.
Paper is another questionable one. The cost (in particular the energy use) of processing recycled paper often exceededs the cost of creating new paper. It has always seemed to me that paper should be buried in landfill as this is exactly the reverse process of burning fossil fuels, i.e. it's taking CO2 out of the atmosphere and burying it back underground. Actually, planting fast growing plants, harvesting them, and burying them down old coal mines could be quite a good thing to do from this perspective.
--
Andrew Gabriel

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On 05 Jun 2005 15:55:09 GMT, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

I've been known to suggest that oil deposits are the disposable nappies of a lost civilisation.
--
On-line canal route planner: http://www.canalplan.org.uk

(Waterways World site of the month, April 2001)
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On 05 Jun 2005 15:55:09 GMT, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

I'll not disagree but given the "need" to avoid landfill and ongoing quarrying/dredging for sand it just struck me as a possible use without too much recycling cost.

I'll agree this with the possible exception of glossy papers which have lots of china clay in them, I wonder if this filler can be washed out and reclaimed?
This is a bit of my hobby horse because use of recycled fiber impacted on my erstwhile trade. In the 70s we harvested the portion of the crop that was "pulpwood" at a profit. As GATT and recycling bit we needed to cross subsidise harvesting this with the better grades, now with mechanised harvesting a lot gets left in the wood.
I disagree about burying it though, if anaerobic conditions occur biogas is given off and this has implications for damaging the ozone layer as well as being a worse climate changing gas than the CO2 that would be generated by burning it.
Now if you consider pyrolysing it to >85% fixed carbon and then burying it.....
I also cannot see the benefit in recycling simple (non halogenated) plastics over burning them for power, more a topic for the environment newsgroups though.
AJH
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snipped-for-privacy@despammed.com wrote:

Totally agree.
And as far as landfill sites - or their lack - goes - why not use glass banks to shore up the east coast, bits of which keep falling into the sea...?

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Andrew Gabriel wrote:

I like the idea of it. Perhaps we could go onto lots of wbesites and request catalogues to be sent to 'shaft 6, The Old Tin Mine, Trefryw, S Wales'
;-)
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Andrew Gabriel wrote:

And when the soil has been denuded of all nutrients, what then? Or local water courses are polluted from nitrate run off due to fertilising said crops?
Seems like a paticularly stupid idea to me.
MBQ
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snipped-for-privacy@hotmail.com wrote:

Eh? either he nitrate has gone into teh plantst or it hasn't. If its gone in it won't be in the water.
Its perfectly possible to grow willows with very little nitrate. Or ghrow a crop of field beans one yaer and then plant the willow.

Yes, but its YOUR idea not his.

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replying to sylva, chris wrote: the limes the binder not the glass
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replying to biff, chris wrote: silica sand is glass, used for ashlar . sharp sand contains glass but a not as much. 3:1 ratio is okay for walls and low level renders/pointing. exposed areas need something stronger. 2.2:1 lime to sand ( add a tiny wee bit cement to the mix ) any st astiars nhl (except 5) will work greatly. you can buy pre mix 25 kg for £12.50. fine sand or coarse ( fine for pointing/rendering less than 5mm) . just add water. adhesion is exceptional and it sets very quickly. its bombproof!!! otherwise general building ...... sharp, sand, tradiblanc nhl (35 kg) but be aware, tradi sets very light so use a dark sand or add pigment and defiantly carry out a wee trial.patch
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wrote:

It is for insulating renders on houses needing a breathable insulating layer outside.
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