Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.

I had to crush some of the portland cement because it's a bit old and
some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must chisel
out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out so
poor. Next time I'll use 2 sand, 1 cement.

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but no. It's
too sandy by far. I'm sure I put in 3 levels of cement and 9 of sand.

I had to crush some of the portland cement because it's a bit old and some
of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I notice
that when I'm chiseling the concrete out that I made, it easy turns to
powder. My house has concrete/pebble walls and I must chisel out and plug
with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out so
poor. Next time I'll use 2 sand, 1 cement.


Use NEW cement FFS!

"RW" wrote in message
...

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.

I had to crush some of the portland cement because it's a bit old and
some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must chisel
out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out so
poor. Next time I'll use 2 sand, 1 cement.


Use NEW cement FFS!


Does cement "go off?

I mean, I can crush these clumped up bits to powder, because they are
fairly soft. But is the cement now practically useless even when ground
down?

In article ,
"Rich" writes:
Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.

3:1 is a very strong mix. There aren't many applications where
that would be suitable.

I had to crush some of the portland cement because it's a bit old and
some of has gone hard, but not rock hard. I used a rolling pin.

That means the cement has partially set, so you actually have a
cement bag containing a mixture of inert dust and cement, the
proportions of which are unknown. Just because you broke it
apart doesn't mean it's capable of setting a second time.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must chisel
out and plug with concrete for shelving.

Where does the concrete come into it? You described making
mortar, not concrete.

I'm miffed and not slightly confused why the mix I made turned out so
poor. Next time I'll use 2 sand, 1 cement.

Because your cement has gone off, and/or because you didn't allow
enough time for it to set fully (about 6 weeks).

1) Chuck out the bag of gone-off cemnent.
2) Describe the wall construction in more detail.
3) Specify age of house, and location, so we have some idea
how it might have been constructed.

Then people can help you by suggesting what you should be
using (which might not be cement at all, but certainly won't
be a 2:1 or 3:1 mortar mix).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Rich wrote:

"RW" wrote in message
...

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.

I had to crush some of the portland cement because it's a bit old and
some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must chisel
out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out so
poor. Next time I'll use 2 sand, 1 cement.


Use NEW cement FFS!


Does cement "go off?

I mean, I can crush these clumped up bits to powder, because they are
fairly soft. But is the cement now practically useless even when ground
down?


sort of. Essentially half of that ground up crap has set. So its not
cement, its a weak sand. Which is why you needed more..

Rich wrote:
"RW" wrote in message
...

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but
no. It's too sandy by far. I'm sure I put in 3 levels of cement and
9 of sand.

I had to crush some of the portland cement because it's a bit old
and some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must
chisel out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out
so poor. Next time I'll use 2 sand, 1 cement.


Use NEW cement FFS!


Does cement "go off?

Yes

I mean, I can crush these clumped up bits to powder, because they are
fairly soft. But is the cement now practically useless even when
ground down?

Yes.

Now. what were you doing with a 1:3 mix of cement and sand?

As this is not classed as a concrete mix but a mortar.

A concrete mix would be 1:3:4.

I.E. 1 part cement, 3 parts sand and 4 parts chippings - of varying grades
dependant upon the job in hand.

Also, the amount of water used will have an effect on the strength - as will
the water content of the sand. Too much water = a weak mix of concrete

Tanner-'op

In article ,
Rich wrote:
Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.

3:1 is far too strong for most things.

I had to crush some of the portland cement because it's a bit old and
some of has gone hard, but not rock hard. I used a rolling pin.

You have your answer. Cement goes off with age - and is so cheap it's not
worth keeping.

--
*I used to have an open mind but my brains kept falling out *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
dave wrote:
On Tue, 15 Jul 2008 00:23:03 +0100, "Dave Plowman (News)"
wrote:

In article ,
Rich wrote:
Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.

3:1 is far too strong for most things.

Ok - I've been reading this thread - know 0 about cement/mortar, but
trying to learn a bit. This has got 2B a stupid question, but how can
the mix be "*too strong* for most things". Too weak I could
understand - but too strong! Please explain.

For example. If you use too strong a mix when bricklaying any movement
will cause the bricks to crack.

--
*I never drink anything stronger than gin before breakfast *

Dave Plowman London SW
To e-mail, change noise into sound.

On Jul 15, 1:16*am, "Dave Plowman (News)"
wrote:
In article ,
* *dave wrote:

On Tue, 15 Jul 2008 00:23:03 +0100, "Dave Plowman (News)"
wrote:
In article ,
* Rich wrote:

Well, I thought 3 parts sand and 1 part cement would be okay, but no..
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.

3:1 is far too strong for most things.
Ok - I've been reading this thread - know 0 about cement/mortar, but
trying to learn a bit. This has got 2B a stupid question, but how can
the mix be "*too strong* for most things". *Too weak I could
understand - but too strong! Please explain.

For example. If you use too strong a mix when bricklaying any movement
will cause the bricks to crack.

Mortar should be weaker than brick, then any movement breaks the
mortar not bricks.


NT

dave wrote:
On Tue, 15 Jul 2008 00:23:03 +0100, "Dave Plowman (News)"
wrote:

In article ,
Rich wrote:
Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.
3:1 is far too strong for most things.

Ok - I've been reading this thread - know 0 about cement/mortar, but
trying to learn a bit. This has got 2B a stupid question, but how can
the mix be "*too strong* for most things". Too weak I could
understand - but too strong! Please explain.

Actually strength reduces with pure portland cement.


The ideal water resistant mix is where the holes between the grains of
sand are completely filled with fine cement. Thats a 'strong' mix and is
used underground and below damp according to my brickies, so that it
wont split with frost: instead the bricks will....haha. Nothing to do
with the mortar though. porous bricks below damp (or in driving rain)+
frost = spalling.

Weaker than that between 2:1 and about 5:1 the mortar becomes less full
of cement, and air pockets replace the cement between the sand grains.

Enough to make it quite permeable. Like most bricks are, so its reckoned
to be no worse than the bricks in terms of general waterproofness. The
texture tends proggresivly from 'hard set muck' towards 'crunchy sand'
as you go up the scale reaching crunchy sand with very little strength
at about 7:1

Which is sort of what you might lay e.g. patio slabs on. The cement only
being there to stop the sand washing away, without reducing drainage.

I've got a few cracks in my wall that I built where I didn't use ties.
The cement is rock hard, but no bricks cracked by the way.

I have never seen a brick split by too strong cement yet. Maybe old,
soft or very cheap bricks will tho.

The general reason to not use too strong a mix is firstly that it gets
weaker beyond the sort of optimal 2:1 and secondly cement, whilst cheap,
is still a whole lot more expensive than sand.

To be honest, there is a lot of merit in the view for general
bricklaying, that the cement is there to stop the sand washing out, and
the sand is there to keep the bricks apart ;-)

In this weather you mortar wont fully set for 2 days as far as general
feel goes. After that it will set a bit harder in a few weeks.

On 15 Jul, 06:02, The Natural Philosopher wrote:
dave wrote:
On Tue, 15 Jul 2008 00:23:03 +0100, "Dave Plowman (News)"
wrote:

In article ,
Rich wrote:
Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.
3:1 is far too strong for most things.

Ok - I've been reading this thread - know 0 about cement/mortar, but
trying to learn a bit. This has got 2B a stupid question, but how can
the mix be "*too strong* for most things". Too weak I could
understand - but too strong! Please explain.

Actually strength reduces with pure portland cement.

The ideal water resistant mix is where the holes between the grains of
sand are completely filled with fine cement. Thats a 'strong' mix and is
used underground and below damp according to my brickies, so that it
wont split with frost: instead the bricks will....haha. Nothing to do
with the mortar though. porous bricks below damp (or in driving rain)+
frost = spalling.

Weaker than that between 2:1 and about 5:1 the mortar becomes less full
of cement, and air pockets replace the cement between the sand grains.

Enough to make it quite permeable. Like most bricks are, so its reckoned
to be no worse than the bricks in terms of general waterproofness. The
texture tends proggresivly from 'hard set muck' towards 'crunchy sand'
as you go up the scale reaching crunchy sand with very little strength
at about 7:1

Which is sort of what you might lay e.g. patio slabs on. The cement only
being there to stop the sand washing away, without reducing drainage.

I've got a few cracks in my wall that I built where I didn't use ties.
The cement is rock hard, but no bricks cracked by the way.

I have never seen a brick split by too strong cement yet. Maybe old,
soft or very cheap bricks will tho.

The general reason to not use too strong a mix is firstly that it gets
weaker beyond the sort of optimal 2:1 and secondly cement, whilst cheap,
is still a whole lot more expensive than sand.

To be honest, there is a lot of merit in the view for general
bricklaying, that the cement is there to stop the sand washing out, and
the sand is there to keep the bricks apart ;-)

In this weather you mortar wont fully set for 2 days as far as general
feel goes. After that it will set a bit harder in a few weeks.

Also, good mixing is important, especially for weaker mixes. If you
are trying for 5:1 for bricklaying and its not mixed well, you could
have parts at 7:1 which is too weak and / or will take too long to
set.
Simon.

"Tanner-'op" wrote in message
...
Rich wrote:
"RW" wrote in message
...

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but
no. It's too sandy by far. I'm sure I put in 3 levels of cement and
9 of sand.

I had to crush some of the portland cement because it's a bit old
and some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must
chisel out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out
so poor. Next time I'll use 2 sand, 1 cement.


Use NEW cement FFS!


Does cement "go off?

Yes

I mean, I can crush these clumped up bits to powder, because they are
fairly soft. But is the cement now practically useless even when
ground down?

Yes.

Now. what were you doing with a 1:3 mix of cement and sand?

As this is not classed as a concrete mix but a mortar.

A concrete mix would be 1:3:4.

I.E. 1 part cement, 3 parts sand and 4 parts chippings - of varying grades
dependant upon the job in hand.

Also, the amount of water used will have an effect on the strength - as
will the water content of the sand. Too much water = a weak mix of
concrete

Tanner-'op


Butting in here, as I too find the ratios in practice a bit hit and miss,
and have to fight a strong tendency to add a bit more cement 'just to make
sure':

Other comments seem to be hitting on about 5:1 sand to cement for mortar,
but your ratio for concrete is essentially that same 'spoonful' of cement
now extended to cover 7 'spoonfuls' of other stuff. Is that really reliably
enough?
(before I resume trying to remake a large number of steps in the - very
steep - garden, that are taking me a long time because of the surprisingly
large quantities of materials involved... I would not want to sit back and
watch them all get gradually washed away afterwards!)

Cheers,
S

Spamlet wrote:
"Tanner-'op" wrote in message
...
Rich wrote:
"RW" wrote in message
...
"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but
no. It's too sandy by far. I'm sure I put in 3 levels of cement and
9 of sand.

I had to crush some of the portland cement because it's a bit old
and some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must
chisel out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out
so poor. Next time I'll use 2 sand, 1 cement.

Use NEW cement FFS!

Does cement "go off?
Yes

I mean, I can crush these clumped up bits to powder, because they are
fairly soft. But is the cement now practically useless even when
ground down?
Yes.

Now. what were you doing with a 1:3 mix of cement and sand?

As this is not classed as a concrete mix but a mortar.

A concrete mix would be 1:3:4.

I.E. 1 part cement, 3 parts sand and 4 parts chippings - of varying grades
dependant upon the job in hand.

Also, the amount of water used will have an effect on the strength - as
will the water content of the sand. Too much water = a weak mix of
concrete

Tanner-'op


Butting in here, as I too find the ratios in practice a bit hit and miss,
and have to fight a strong tendency to add a bit more cement 'just to make
sure':

Other comments seem to be hitting on about 5:1 sand to cement for mortar,
but your ratio for concrete is essentially that same 'spoonful' of cement
now extended to cover 7 'spoonfuls' of other stuff. Is that really reliably
enough?
(before I resume trying to remake a large number of steps in the - very
steep - garden, that are taking me a long time because of the surprisingly
large quantities of materials involved... I would not want to sit back and
watch them all get gradually washed away afterwards!)


I always want to add a bit. Doesn't seem feasible it will set sound with
standard ratios.

Isn't it very largely the surface area of the 'other stuff' together
with how the packing works? That is, the cement fills holes betwen sand
particles; the sand/cement fills holes between the aggregate particles.
And there is just enough 'binding' power in the cement for the huge area
of sand surface plus the much smaller area of aggregate surface.

Posting in the hope that someone will tell me where I am wrong - if I
am. That is just how I seem to have absorbed infromation over the years.

The experiemnt I have always wanted to do is to mix in a load of jelly
(whether real jelly, carragheenan, agar or something similar). Seems to
me that you might manage a very weak mixture but surprisingly strong
final substance as the gelling could stop the cement particles flowing
out. Or maybe it would work to allow very sloppy mixtures to set?

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

On 15 Jul, 11:20, "Spamlet" wrote:
"Tanner-'op" wrote in message

...



Rich wrote:
"RW" wrote in message
...

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but
no. It's too sandy by far. I'm sure I put in 3 levels of cement and
9 of sand.

I had to crush some of the portland cement because it's a bit old
and some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must
chisel out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out
so poor. Next time I'll use 2 sand, 1 cement.

Use NEW cement FFS!

Does cement "go off?

Yes

I mean, I can crush these clumped up bits to powder, because they are
fairly soft. But is the cement now practically useless even when
ground down?

Yes.

Now. what were you doing with a 1:3 mix of cement and sand?

As this is not classed as a concrete mix but a mortar.

A concrete mix would be 1:3:4.

I.E. 1 part cement, 3 parts sand and 4 parts chippings - of varying grades
dependant upon the job in hand.

Also, the amount of water used will have an effect on the strength - as
will the water content of the sand. Too much water = a weak mix of
concrete

Tanner-'op

Butting in here, as I too find the ratios in practice a bit hit and miss,
and have to fight a strong tendency to add a bit more cement 'just to make
sure':

Other comments seem to be hitting on about 5:1 sand to cement for mortar,
but your ratio for concrete is essentially that same 'spoonful' of cement
now extended to cover 7 'spoonfuls' of other stuff. Is that really reliably
enough?
(before I resume trying to remake a large number of steps in the - very
steep - garden, that are taking me a long time because of the surprisingly
large quantities of materials involved... I would not want to sit back and
watch them all get gradually washed away afterwards!)

Cheers,
S

I think the ballast in concrete (e.g. stones) is large enough simply
to take up volume in the mix. But a general strong concrete mix is
1-2-4, so the cement to sand ratio is 1 to 2, more than you would use
for a mortar where 1-3 would be the max (with engineering bricks).
When I was using all-in ballast (sand and stones), I thought the
equivalent to 1-2-4 is now 1-6 which sounded quite weak, but it set
very solid, since the stones are really just bulking up the volume, as
well as stopping cracks propogating etc.
Simon.

"sm_jamieson" wrote in message
...
On 15 Jul, 11:20, "Spamlet" wrote:
"Tanner-'op" wrote in message

...



Rich wrote:
"RW" wrote in message
...

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but
no. It's too sandy by far. I'm sure I put in 3 levels of cement and
9 of sand.

I had to crush some of the portland cement because it's a bit old
and some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must
chisel out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out
so poor. Next time I'll use 2 sand, 1 cement.

Use NEW cement FFS!

Does cement "go off?

Yes

I mean, I can crush these clumped up bits to powder, because they are
fairly soft. But is the cement now practically useless even when
ground down?

Yes.

Now. what were you doing with a 1:3 mix of cement and sand?

As this is not classed as a concrete mix but a mortar.

A concrete mix would be 1:3:4.

I.E. 1 part cement, 3 parts sand and 4 parts chippings - of varying
grades
dependant upon the job in hand.

Also, the amount of water used will have an effect on the strength - as
will the water content of the sand. Too much water = a weak mix of
concrete

Tanner-'op

Butting in here, as I too find the ratios in practice a bit hit and miss,
and have to fight a strong tendency to add a bit more cement 'just to
make
sure':

Other comments seem to be hitting on about 5:1 sand to cement for mortar,
but your ratio for concrete is essentially that same 'spoonful' of cement
now extended to cover 7 'spoonfuls' of other stuff. Is that really
reliably
enough?
(before I resume trying to remake a large number of steps in the - very
steep - garden, that are taking me a long time because of the
surprisingly
large quantities of materials involved... I would not want to sit back
and
watch them all get gradually washed away afterwards!)

Cheers,
S

I think the ballast in concrete (e.g. stones) is large enough simply
to take up volume in the mix. But a general strong concrete mix is
1-2-4, so the cement to sand ratio is 1 to 2, more than you would use
for a mortar where 1-3 would be the max (with engineering bricks).
When I was using all-in ballast (sand and stones), I thought the
equivalent to 1-2-4 is now 1-6 which sounded quite weak, but it set
very solid, since the stones are really just bulking up the volume, as
well as stopping cracks propogating etc.
Simon.

Beginning to see light dawning here. So really we might see the thing as
the ballast being equivalent to a number of very small bricks, mortared
together by the sand and cement.

Suppose one just has to watch out for any more absorbent or soluble 'stones'
that might creep in (bits of old plaster board come to mind, as I consider
the bags of rubble from our bathroom conversion, as possible ballast
material for my steps - duly sieved of course.).

All very interesting,

Cheers,
S

Dave Plowman (News) wrote:

but too strong! Please explain.

For example. If you use too strong a mix when bricklaying any movement
will cause the bricks to crack.

Also strong mixes shrink more when curing. Using the weakest suitable
mix helps avoid shrinkage problems and saves money.

--
Andy

Spamlet wrote:
Beginning to see light dawning here. So really we might see the
thing as the ballast being equivalent to a number of very small
bricks, mortared together by the sand and cement.

Suppose one just has to watch out for any more absorbent or soluble
'stones' that might creep in (bits of old plaster board come to mind,
as I consider the bags of rubble from our bathroom conversion, as
possible ballast material for my steps - duly sieved of course.).

All very interesting,

Cheers,
S

Don't use secondhand rubble to mix concrete...like anything else, it's only
as strong as it's weakest link, and if that link is lumps of lime plaster
and bits of plasterboard, then it's going to diseappear fairly quickly -
frost is the main enemy of concrete, and given that these highly absorbent
particles will soak up water like a sponge, the frost will then expand
these, effectively blasting apart the concrete until it comes away in thin
sheets.
Limestone, other solid stone chippings or pebbles are the only decent
quality ballast that should be used with sand and cement for high quality
concrete.

"Phil L" wrote in message
om...
Spamlet wrote:
Beginning to see light dawning here. So really we might see the
thing as the ballast being equivalent to a number of very small
bricks, mortared together by the sand and cement.

Suppose one just has to watch out for any more absorbent or soluble
'stones' that might creep in (bits of old plaster board come to mind,
as I consider the bags of rubble from our bathroom conversion, as
possible ballast material for my steps - duly sieved of course.).

All very interesting,

Cheers,
S

Don't use secondhand rubble to mix concrete...like anything else, it's
only as strong as it's weakest link, and if that link is lumps of lime
plaster and bits of plasterboard, then it's going to diseappear fairly
quickly - frost is the main enemy of concrete, and given that these highly
absorbent particles will soak up water like a sponge, the frost will then
expand these, effectively blasting apart the concrete until it comes away
in thin sheets.
Limestone, other solid stone chippings or pebbles are the only decent
quality ballast that should be used with sand and cement for high quality
concrete.
Are the plastery bits any use for anything?
Hmm, lots of blackboard 'chalk'...

Could go on the allotment I suppose, but that is real chalk already.

S

Spamlet wrote:
"Phil L" wrote in message
om...
Spamlet wrote:
Beginning to see light dawning here. So really we might see the
thing as the ballast being equivalent to a number of very small
bricks, mortared together by the sand and cement.

Suppose one just has to watch out for any more absorbent or soluble
'stones' that might creep in (bits of old plaster board come to mind,
as I consider the bags of rubble from our bathroom conversion, as
possible ballast material for my steps - duly sieved of course.).

All very interesting,

Cheers,
S
Don't use secondhand rubble to mix concrete...like anything else, it's
only as strong as it's weakest link, and if that link is lumps of lime
plaster and bits of plasterboard, then it's going to diseappear fairly
quickly - frost is the main enemy of concrete, and given that these highly
absorbent particles will soak up water like a sponge, the frost will then
expand these, effectively blasting apart the concrete until it comes away
in thin sheets.
Limestone, other solid stone chippings or pebbles are the only decent
quality ballast that should be used with sand and cement for high quality
concrete.
Are the plastery bits any use for anything?
Hmm, lots of blackboard 'chalk'...

Could go on the allotment I suppose, but that is real chalk already.


I have read that it (gypsum) helps to make clay soil workable.

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

In article ,
Rod writes:
I have read that it (gypsum) helps to make clay soil workable.

I've chucked loads of gypsum slop-ends over the lawn and the
beds, and things that grow there seem to like it. Did the same
with cement in one particular flower bed, and it developed quite
a strong crust. The bluebells all managed to break through it
though, giving their usual dense display of blue.

I wouldn't use these anywhere where you might grow veg though;
there are some nasty things in cement. Probably wasn't a good
idea to dump cement mortar slops into the flower bed in the
first place.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Rod wrote:
Spamlet wrote:
"Phil L" wrote in message
om...
Spamlet wrote:
Beginning to see light dawning here. So really we might see the
thing as the ballast being equivalent to a number of very small
bricks, mortared together by the sand and cement.

Suppose one just has to watch out for any more absorbent or soluble
'stones' that might creep in (bits of old plaster board come to mind,
as I consider the bags of rubble from our bathroom conversion, as
possible ballast material for my steps - duly sieved of course.).

All very interesting,

Cheers,
S
Don't use secondhand rubble to mix concrete...like anything else,
it's only as strong as it's weakest link, and if that link is lumps
of lime plaster and bits of plasterboard, then it's going to
diseappear fairly quickly - frost is the main enemy of concrete, and
given that these highly absorbent particles will soak up water like a
sponge, the frost will then expand these, effectively blasting apart
the concrete until it comes away in thin sheets.
Limestone, other solid stone chippings or pebbles are the only decent
quality ballast that should be used with sand and cement for high
quality concrete.
Are the plastery bits any use for anything?
Hmm, lots of blackboard 'chalk'...

Could go on the allotment I suppose, but that is real chalk already.


I have read that it (gypsum) helps to make clay soil workable.


Alkaline though.
You could always use New Improved B&Q Soil Improver (aka sharp sand!)

Dave Plowman (News) wrote:

You have your answer. Cement goes off with age - and is so cheap it's not
worth keeping.


Crushed dead cement is still good for oil spills on the garage floor.

Andy

Spamlet wrote:


Beginning to see light dawning here. So really we might see the thing as
the ballast being equivalent to a number of very small bricks, mortared
together by the sand and cement.


Yes. Concrete is strong in compresssion, relatively weak in shear, and
very weak in tension.


Essentially conctrete is packed stones. To increase shear strength we
add sand to stop them sliding about and we add cement to stop the sand
grains sliding about. We then add steel to give tensile strength.

The cement merely increase the shear strength by adding a reasonably
high shear matrix between the sand grains.

Suppose one just has to watch out for any more absorbent or soluble 'stones'
that might creep in (bits of old plaster board come to mind, as I consider
the bags of rubble from our bathroom conversion, as possible ballast
material for my steps - duly sieved of course.).


I dont even bother to do that, TBH. large limps of crap embedded in
mortar work pretty well.


concrete will work at prettty low cement ratios, but it becomes porous,
liable to frost damage, aand easily damaged by sharp onbjects.


All very interesting,

Cheers,
S

Phil L wrote:
Spamlet wrote:
Beginning to see light dawning here. So really we might see the
thing as the ballast being equivalent to a number of very small
bricks, mortared together by the sand and cement.

Suppose one just has to watch out for any more absorbent or soluble
'stones' that might creep in (bits of old plaster board come to mind,
as I consider the bags of rubble from our bathroom conversion, as
possible ballast material for my steps - duly sieved of course.).

All very interesting,

Cheers,
S

Don't use secondhand rubble to mix concrete...like anything else, it's only
as strong as it's weakest link, and if that link is lumps of lime plaster
and bits of plasterboard, then it's going to diseappear fairly quickly -
frost is the main enemy of concrete, and given that these highly absorbent
particles will soak up water like a sponge, the frost will then expand
these, effectively blasting apart the concrete until it comes away in thin
sheets.
Limestone, other solid stone chippings or pebbles are the only decent
quality ballast that should be used with sand and cement for high quality
concrete.


but most domestic concrete des not need to be high quality.

And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.

Limestone is soft and permeable.

In article ,
The Natural Philosopher wrote:
And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.

Limestone is soft and permeable.

I did wonder about that. I've never seen it in mixed aggregate. Not that
I've knocked up much.

--
*Work is for people who don't know how to fish.

Dave Plowman London SW
To e-mail, change noise into sound.

The Natural Philosopher wrote:
Phil L wrote:
Spamlet wrote:
Beginning to see light dawning here. So really we might see the
thing as the ballast being equivalent to a number of very small
bricks, mortared together by the sand and cement.

Suppose one just has to watch out for any more absorbent or soluble
'stones' that might creep in (bits of old plaster board come to
mind, as I consider the bags of rubble from our bathroom
conversion, as possible ballast material for my steps - duly sieved
of course.). All very interesting,

Cheers,
S

Don't use secondhand rubble to mix concrete...like anything else,
it's only as strong as it's weakest link, and if that link is lumps
of lime plaster and bits of plasterboard, then it's going to
diseappear fairly quickly - frost is the main enemy of concrete, and
given that these highly absorbent particles will soak up water like
a sponge, the frost will then expand these, effectively blasting
apart the concrete until it comes away in thin sheets.
Limestone, other solid stone chippings or pebbles are the only decent
quality ballast that should be used with sand and cement for high
quality concrete.


but most domestic concrete des not need to be high quality.

And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.

Limestone is soft and permeable.

It must depend on where you live in the UK then because around here it's
almost all limestone, even the readymixed crowd use it, and almost all BM's
stock it, along with B&Q etc.
Flint is a rarity, except for decorative purposes and granite is used, but
in the form of 'granno' - IE sharp green grit.

Phil L wrote:

http://www.tarmac.co.uk/QUARRYVILLE/lab/limestone.html

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but no. It's
too sandy by far. I'm sure I put in 3 levels of cement and 9 of sand.

I had to crush some of the portland cement because it's a bit old and some
of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I notice
that when I'm chiseling the concrete out that I made, it easy turns to
powder. My house has concrete/pebble walls and I must chisel out and plug
with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out so
poor. Next time I'll use 2 sand, 1 cement.

I asked this

http://groups.google.co.uk/group/uk.d-i-y/browse_thread/thread/1da50ccd1684eae1/04fc5f8af1be37b2?hl=en&lnk=st&q=#04fc5f8af1be37b2

And my cement was fluffy and did not need to be broken up by a rolling pin.

Adam

ARWadworth wrote:

"Rich" wrote in message
...
Well, I thought 3 parts sand and 1 part cement would be okay, but no.
It's too sandy by far. I'm sure I put in 3 levels of cement and 9 of
sand.

I had to crush some of the portland cement because it's a bit old and
some of has gone hard, but not rock hard. I used a rolling pin.

I'm having to chisel out the concrete now and make up a new mix. I
notice that when I'm chiseling the concrete out that I made, it easy
turns to powder. My house has concrete/pebble walls and I must chisel
out and plug with concrete for shelving.

I'm miffed and not slightly confused why the mix I made turned out so
poor. Next time I'll use 2 sand, 1 cement.

I asked this

http://groups.google.co.uk/group/uk.d-i-y/browse_thread/thread/1da50ccd1684eae1/04fc5f8af1be37b2?hl=en&lnk=st&q=#04fc5f8af1be37b2


And my cement was fluffy and did not need to be broken up by a rolling pin.

Adam

Glad you posted that refresher. I contributed there and said I had used
some old cement for a fence post. It set. And a few days, maybe a week
or two, later I realised that I needed to 'adjust' it. Bolster. Lump
hammer. And by gosh it was tough.

For critical work - fresh, in date, dry. Never even consider anything else.

For probably-strong-enough - slightly old, still looking good, dry can
be adequate.

What OP of this thread said, he'd need to send it to a cement factory
for reprocessing to stand a chance.

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

Phil L wrote:
Phil L wrote:

http://www.tarmac.co.uk/QUARRYVILLE/lab/limestone.html


well well well. Round here its never ever used. gravel (flint) only..

The Natural Philosopher wrote:

And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.


In my experience, limestone and alluvial gravels are by far the two
most frequently used aggregates for concrete. Flint is something of a
rarity - I don't think I have ever seen a project that used flint for
a concrete aggregate.

Where gravel is available, it tends to be cheaper. However, away from
south east England, gravel is used less and limestone dominates the
market. There are some localised areas where granite is quarried in
large quantities for roadstone, and some of it finds its way into
local readymix plants, but granite is always quite expensive because
of the much higher cost of crushing it - it wears out crushers four or
five times faster than limestone does.

Even in south east England, limestone has taken an increasing share of
the market. That is largely because of the efforts of ARC and Foster
Yeoman, who ship limestone from the Mendip Hills of Somerset
principally into Acton, West London, using their own fleet of trains.

There is nothing inferior about concrete made with limestone. Many
large bridges, landmark office developments and other major structures
are built with it. Most of the nuclear reactor pressure vessels in
the UK's nuclear power stations are made of pre-stressed concrete made
with limestone aggregate. So it is a top quality product.


[This is not in any way a criticism of your postings about concrete in
this thread, which are otherwise factually correct and make an
interesting read - thanks.]



** Posted from http://www.teranews.com **

"Bruce" wrote in message
...
The Natural Philosopher wrote:

And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.


In my experience, limestone and alluvial gravels are by far the two
most frequently used aggregates for concrete. Flint is something of a
rarity - I don't think I have ever seen a project that used flint for
a concrete aggregate.

Where gravel is available, it tends to be cheaper. However, away from
south east England, gravel is used less and limestone dominates the
market. There are some localised areas where granite is quarried in
large quantities for roadstone, and some of it finds its way into
local readymix plants, but granite is always quite expensive because
of the much higher cost of crushing it - it wears out crushers four or
five times faster than limestone does.

Even in south east England, limestone has taken an increasing share of
the market. That is largely because of the efforts of ARC and Foster
Yeoman, who ship limestone from the Mendip Hills of Somerset
principally into Acton, West London, using their own fleet of trains.

There is nothing inferior about concrete made with limestone. Many
large bridges, landmark office developments and other major structures
are built with it. Most of the nuclear reactor pressure vessels in
the UK's nuclear power stations are made of pre-stressed concrete made
with limestone aggregate. So it is a top quality product.


[This is not in any way a criticism of your postings about concrete in
this thread, which are otherwise factually correct and make an
interesting read - thanks.]



** Posted from http://www.teranews.com **

Er: in the SE, where I come from: 'gravel' generally = small bits of flint +
the odd oyster and belemnite fossil, as it comes from Chalk-derived clay
with flints washed and sorted by rivers. [Take a look at a Google Earth of
Rickmansworth to get an idea of the vast amount that has already been
removed along most of the river valleys in the region. Quite scary I find.]

S

"Spamlet" wrote:

Er: in the SE, where I come from: 'gravel' generally = small bits of flint +
the odd oyster and belemnite fossil, as it comes from Chalk-derived clay
with flints washed and sorted by rivers.


I have lived most of my life in SE England, and worked in the concrete
industry for many years. The correct term for what you are describing
as "flint" is "crushed gravel".

Perhaps it is colloquially known as flint, but in geological terms
flint consists of hard inclusions within sedimentary rocks such as
chalk. If the chalk is eroded, and the flint particles are washed
down rivers, those particles are then termed alluvial gravel - but
this could take hundreds of thousands or millions of years, and the
washing and sorting process significantly changes the shape of the
particles. Alluvial gravels are very rounded compared to flints.

I'm sorry to be pedantic but the point of the discussion is to
understand which rocks are used for concrete aggregate, and which are
not. Flint generally isn't, except as an imprecise term for something
rather different, which is correctly called gravel.

** Posted from http://www.teranews.com **

Bruce wrote:
The Natural Philosopher wrote:
And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.


In my experience, limestone and alluvial gravels are by far the two
most frequently used aggregates for concrete. Flint is something of a
rarity - I don't think I have ever seen a project that used flint for
a concrete aggregate.


What did you think alluvial gravel WAS if not flint? Small and smashed
up..but its still flint.



Where gravel is available, it tends to be cheaper. However, away from
south east England, gravel is used less and limestone dominates the
market. There are some localised areas where granite is quarried in
large quantities for roadstone, and some of it finds its way into
local readymix plants, but granite is always quite expensive because
of the much higher cost of crushing it - it wears out crushers four or
five times faster than limestone does.

Even in south east England, limestone has taken an increasing share of
the market. That is largely because of the efforts of ARC and Foster
Yeoman, who ship limestone from the Mendip Hills of Somerset
principally into Acton, West London, using their own fleet of trains.

There is nothing inferior about concrete made with limestone. Many
large bridges, landmark office developments and other major structures
are built with it. Most of the nuclear reactor pressure vessels in
the UK's nuclear power stations are made of pre-stressed concrete made
with limestone aggregate. So it is a top quality product.


[This is not in any way a criticism of your postings about concrete in
this thread, which are otherwise factually correct and make an
interesting read - thanks.]



** Posted from http://www.teranews.com **

The Natural Philosopher wrote:

Bruce wrote:
The Natural Philosopher wrote:
And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.


In my experience, limestone and alluvial gravels are by far the two
most frequently used aggregates for concrete. Flint is something of a
rarity - I don't think I have ever seen a project that used flint for
a concrete aggregate.


What did you think alluvial gravel WAS if not flint? Small and smashed
up..but its still flint.


No, that's what it was. An incredible amount of changes are made from
flint being eroded out of chalk to becoming alluvial or sea-dredged
gravel. Ask a geologist. My partner is a geologist, and she is
highly amused that people should describe alluvial gravel as "flint".

That's like describing coal or oil as "trees".

** Posted from http://www.teranews.com **

Bruce wrote:
The Natural Philosopher wrote:

Bruce wrote:
The Natural Philosopher wrote:
And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.

In my experience, limestone and alluvial gravels are by far the two
most frequently used aggregates for concrete. Flint is something of a
rarity - I don't think I have ever seen a project that used flint for
a concrete aggregate.

What did you think alluvial gravel WAS if not flint? Small and smashed
up..but its still flint.


No, that's what it was. An incredible amount of changes are made from
flint being eroded out of chalk to becoming alluvial or sea-dredged
gravel. Ask a geologist. My partner is a geologist, and she is
highly amused that people should describe alluvial gravel as "flint".

That's like describing coal or oil as "trees".

** Posted from http://www.teranews.com **

Long ago, I have bought a bag of fine ready mix concrete in which was
something that looked like flint. Of the order of quarter inch pieces
and most edges very square and sharp (some very sharp). At the time, I
assumed some sort of crushed flint. Clearly not alluvial gravel as that
would have its edges smoothed off at least a bit.

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

Bruce wrote:
"Spamlet" wrote:
Er: in the SE, where I come from: 'gravel' generally = small bits of flint +
the odd oyster and belemnite fossil, as it comes from Chalk-derived clay
with flints washed and sorted by rivers.


I have lived most of my life in SE England, and worked in the concrete
industry for many years. The correct term for what you are describing
as "flint" is "crushed gravel".

Perhaps it is colloquially known as flint, but in geological terms
flint consists of hard inclusions within sedimentary rocks such as
chalk. If the chalk is eroded, and the flint particles are washed
down rivers, those particles are then termed alluvial gravel - but
this could take hundreds of thousands or millions of years, and the
washing and sorting process significantly changes the shape of the
particles. Alluvial gravels are very rounded compared to flints.

I'm sorry to be pedantic but the point of the discussion is to
understand which rocks are used for concrete aggregate, and which are
not. Flint generally isn't, except as an imprecise term for something
rather different, which is correctly called gravel.

** Posted from http://www.teranews.com **

Flint is the name of the material as a mineral type. Gravel or shingle
is a generic term for sedimentary particles larger than sand grain size.

Bruce wrote:
The Natural Philosopher wrote:

Bruce wrote:
The Natural Philosopher wrote:
And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.

In my experience, limestone and alluvial gravels are by far the two
most frequently used aggregates for concrete. Flint is something of a
rarity - I don't think I have ever seen a project that used flint for
a concrete aggregate.

What did you think alluvial gravel WAS if not flint? Small and smashed
up..but its still flint.


No, that's what it was. An incredible amount of changes are made from
flint being eroded out of chalk to becoming alluvial or sea-dredged
gravel. Ask a geologist. My partner is a geologist, and she is
highly amused that people should describe alluvial gravel as "flint".

That's like describing coal or oil as "trees".


Then your partner is being silly. Its only been smashed up, not
metamorphosed, and in the gravel in my drive there are plenty of intact
small flints to be seen, the rtest being spmewaht smashed.


I suppose that he/she is equally amused by roadstone being called
'granite'. since its no longer bloody great lumps of igneous rock, but
small stome chippings.

Or limestone being called limestone, since its crushed into a fine powder`?



** Posted from http://www.teranews.com **

Rod wrote:
Bruce wrote:
The Natural Philosopher wrote:

Bruce wrote:
The Natural Philosopher wrote:
And limestine is never used in concrtete to my current knowledge:
its usually flint (silica), or possibly granite.

In my experience, limestone and alluvial gravels are by far the two
most frequently used aggregates for concrete. Flint is something of a
rarity - I don't think I have ever seen a project that used flint for
a concrete aggregate.

What did you think alluvial gravel WAS if not flint? Small and
smashed up..but its still flint.


No, that's what it was. An incredible amount of changes are made from
flint being eroded out of chalk to becoming alluvial or sea-dredged
gravel. Ask a geologist. My partner is a geologist, and she is
highly amused that people should describe alluvial gravel as "flint".

That's like describing coal or oil as "trees".

** Posted from http://www.teranews.com **

Long ago, I have bought a bag of fine ready mix concrete in which was
something that looked like flint. Of the order of quarter inch pieces
and most edges very square and sharp (some very sharp). At the time, I
assumed some sort of crushed flint. Clearly not alluvial gravel as that
would have its edges smoothed off at least a bit.


Glaicial

The way it works is that ice carrues racks that smash other rocks in te
way, and the whole lot got carried darn sarth, at which point global
warming was just enough to melt the glaciers, and as they melted they
left behind huge deposits of crushed rock, mainly flint, but few other
types as well: the softer rocks like sandstones became more mud like and
formed the clays. Largely thats is what you buy as sharp sand and
gravel. Its full of jaggedy bits of smashed stones.

That is although its been deposited by water, unlike sea stuff which
gets constantly pounded until the edges are knocked off, the vast
majority of gravels and sharp sands only made one trip in the water,
before being left where they are found today.

Rod wrote:

Bruce wrote:
The Natural Philosopher wrote:

Bruce wrote:
The Natural Philosopher wrote:
And limestine is never used in concrtete to my current knowledge: its
usually flint (silica), or possibly granite.

In my experience, limestone and alluvial gravels are by far the two
most frequently used aggregates for concrete. Flint is something of a
rarity - I don't think I have ever seen a project that used flint for
a concrete aggregate.

What did you think alluvial gravel WAS if not flint? Small and smashed
up..but its still flint.


No, that's what it was. An incredible amount of changes are made from
flint being eroded out of chalk to becoming alluvial or sea-dredged
gravel. Ask a geologist. My partner is a geologist, and she is
highly amused that people should describe alluvial gravel as "flint".

That's like describing coal or oil as "trees".

** Posted from http://www.teranews.com **

Long ago, I have bought a bag of fine ready mix concrete in which was
something that looked like flint. Of the order of quarter inch pieces
and most edges very square and sharp (some very sharp). At the time, I
assumed some sort of crushed flint. Clearly not alluvial gravel as that
would have its edges smoothed off at least a bit.


Probably crushed alluvial gravel.

** Posted from http://www.teranews.com **