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

"Dave" wrote in message
...
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

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.

Sharp sand is used for renders and screeds,also used dry for bedding block
paving and slabs.

On Fri, 27 May 2005 21:39:19 +0000 (UTC), Dave
wrote:

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

Have you come accross "washed sand" yet ?

Rick

"Rick" wrote in message
...
On Fri, 27 May 2005 21:39:19 +0000 (UTC), Dave
wrote:

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

Have you come accross "washed sand" yet ?

Yeah, I washed some building sand the other day. What stayed suspended in
the water was a surprisingly large amount of something called limonite,
which is a kind of clay tinted with yellow oxide.


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I'm tempted to say that washed sand is what you get when you add a dash
of washing up liguid to the mortar to make it easier to work. Really
it means that there is little or no clay and silt mixed in with the
sand. This is not neccessarily an advantage. When making mortar with
sand and lime, as oposed to Portland cement, a sound mortar can be
obtained with less lime if there is some silt and clay in the
aggregate.

Limonite it not a kind of clay but is a hydrated iron oxide, usually
amorphous or cryptocrystalline and often closely combined with
colloidal silica, phosphates, clay minerals and organic decomposition
products. It's a product of the weathering of iron bearing minerals
and is responsible for mush of the yellow/brown colour of sand.
There's not much limonite in silver sand!

Geological pedant.

On 28 May 2005 14:12:45 -0700, wrote:

I'm tempted to say that washed sand is what you get when you add a dash
of washing up liguid to the mortar to make it easier to work. Really
it means that there is little or no clay and silt mixed in with the
sand. This is not neccessarily an advantage. When making mortar with
sand and lime, as oposed to Portland cement, a sound mortar can be
obtained with less lime if there is some silt and clay in the
aggregate.

Limonite it not a kind of clay but is a hydrated iron oxide, usually
amorphous or cryptocrystalline and often closely combined with
colloidal silica, phosphates, clay minerals and organic decomposition
products. It's a product of the weathering of iron bearing minerals
and is responsible for mush of the yellow/brown colour of sand.
There's not much limonite in silver sand!

Geological pedant.

I never knew that

From my (simple) angle, washed sand has larger sharper bits.

I use it to make motar for stone cladding my walls (with rough stone),
where at times there is quite a bit of motar. It makes a stronger
"lump" than when using "building sand".

Rick

"Rick" wrote in message
...
On 28 May 2005 14:12:45 -0700, wrote:

I'm tempted to say that washed sand is what you get when you add a dash
of washing up liguid to the mortar to make it easier to work.

Never do this. Us proper plasticisers.

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wrote in message
oups.com...
I'm tempted to say that washed sand is what you get when you add a dash
of washing up liguid to the mortar to make it easier to work. Really
it means that there is little or no clay and silt mixed in with the
sand. This is not neccessarily an advantage. When making mortar with
sand and lime, as oposed to Portland cement, a sound mortar can be
obtained with less lime if there is some silt and clay in the
aggregate.

Limonite it not a kind of clay but is a hydrated iron oxide, usually
amorphous or cryptocrystalline and often closely combined with
colloidal silica, phosphates, clay minerals and organic decomposition
products. It's a product of the weathering of iron bearing minerals
and is responsible for mush of the yellow/brown colour of sand.

It's the only time I've seen oxides freely suspended in water, which
suggests the particles must either be incredibly small, or they are
balanced
by some or all of the combination products above.
If the oxide content of limonite were higher it wouild presumably have a
commercial value as an ochre.

Geological pedant.
Any geologist is better than none.


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