How do you tell the difference between stone and concrete?

[JoceAndChris]

I am so confused about my house now- what's stone and what's concrete, what was does when, and how, what should stay and what go.

When it's poured down it's easy to see it's concrete/cement. What's the difference between concrete and cement? But when it's cut into slabs I just can't tell. I think I have a concrete path, and I think it wouldn't be a major job to remove the part of it that abuts the house, (having been inspired by some information in the tool thread) which would probably really help the basement. But I'm not confident enough to make that analysis on my own.

Off to take some pics.

Please help! xx

 

[JoceAndChris]

Here's the lean to - cement render on brick. Whilst it does appear to be an old structure I don't know if it's original; I think not. Gawd knows what happened to the roof. The path you see in front of it is clearly concrete.

Here's a close up of the plinth at the base of that wall - I can't tell if it's stone or concrete, why there is a plinth all round the house, if it should stay or go.

Let's just go into the corner, just seen on the left hand side of my top picture. This north facing corner is now the dampest spot in the property, not so much on the ground floor but certainly in the basement. Again, I can't tell if the plinth is stone or concrete or what the huge slab on the ground is made of.

The corner on the left of the photo above now in more detail. This piece of plinth is York stone? And yet it doesn't look the same as other sections of plinth

I'll be so pleased if anyone can shed any light on what the above is made of.

 

[Feltwell]

IWhat's the difference between concrete and cement?

Cement is the grey powder only. When mixed with sand and water it becomes mortar or render, when mixed with sand, water and gravel it becomes concrete. Bit of a simplification but that's basically it.

People often say cement when they mean concrete.

Your plinth looks like stone to me, that has been rendered above with what is probably cement-based render. Try and take a very small piece of the render out with a hammer and cold chisel - if it's very hard then it's probably cement rather than lime based.

 

[Moo]

I'd guess at stone in the second picture because the individual sections are different sizes.
And the irregular cracks in the big slabs remind me of the cement we broke up outside our son's house.

 

[JoceAndChris]

Thank you very much for your helpful thoughts.

Cement is the grey powder only. When mixed with sand and water it becomes mortar or render, when mixed with sand, water and gravel it becomes concrete. Bit of a simplification but that's basically it.

That's very useful to know. I suppose that means that cement is often between bricks and concrete is often used for paths. Bit embarassing to know this little, but hey ho.

There's no doubt in my mind that the render is all cement over the whole house and has to go. What's bothering me is the plinth and the path. If the plinth was stuck on with something cementitious that would prevent breathability right? But can a house breathe through a stone plinth anyway? Is it better to dispense with the plinth altogether?

If the path was brick, not concrete, would that improve the ability of the ground beneath to dry out? Because when I lift up bricks from the brick path I have elsewhere the ground seems very moist indeed.

Before the previous owner poured this cement about the ground here was just grass. All the actions he took were to improve appearance and damp levels. Those actions did not work!

 

[Nigel Watts]

What happens if you pour acid onto concrete? I guess it doesnt react, but limestone clearly would, and lime motar would also react. Perhaps this could be a way of testing.

I wouldnt rush to remove any of your plinth. The higher one looks like a sedimentary rock (limestone or sandstone) the way it is defoliating - not something that concrete would do. On the whole brick and stone are more porous than concrete, so water can evaporate through them more easily. Not true of all stone though. Slate is very impervious to water and is used for damp courses.

Removing the concrete path could help the ground beneath dry out a bit but there might be other reasons for dampness in that corner. Is that a damp patch on the ground in your second from last picture for example? Are the gutters and downpipes sound? You might even want to think of digging a trench around some of the outside wall to lower the ground level

 

[Feltwell]

What happens if you pour acid onto concrete? I guess it doesnt react, but limestone clearly would, and lime motar would also react. Perhaps this could be a way of testing.

Sorry Nigel - cement is heavily alkaline, and concrete definitely reacts with acid.

I also would leave that plinth alone. I think I'd be tempted to investigate a little further - take some render off, see what's underneath, see if the plinth has been stuck on later - I doubt that it has, I suspect it's integral to the wall.

The path just looks like old concrete to me - I'd surprised if it's anything else. Have you a loose cracked section near one edge? Lift a bit out, if you can see stones in the cross-section then it's concrete!

What is certain is that someone has put a cement render fillet between the path and the plinth, and again at the top of the plinth.

If you have a damp proof course, the path may be bridging it. You may be getting problems with rainwater splashing up from the path and saturating the plinth. The path may be laid with the fall the wrong way so the water collects or flows against the plinth. Nigel has already mentioned rainwater goods being in good condition. Where does that downpipe go to? Is it blocked underground and backing up in heavy rainfall?

That gutter/hopper arrangement looks a bit "bodge-tastic", although I don't see any reason why it wouldn't work. Is the hopper blocked? They're a pain for that. The cement render on the wall won't be helping at all, that's for certain.

How essential is the path? If it's not, and presuming it's concrete, I think I'd be tempted to take the worst section out, reduce ground levels and see if your wall dries out at all. Or you could run an angle grinder along to make a cut say 6" out from the wall, and just break out that section.

 

[philpjuk100]

Hi cement is what you buy in bags (blue circle etc) it is a constituent of concrete and mortar and is seldom used neat in domestic houses,so its mortar (cement and sand ) between bricks and concrete (cement sand and gravel) for paths blocks etc but please ignore all this as on this site we do not like cement only lime! :twisted:

 

[Nigel Watts]

What happens if you pour acid onto concrete? I guess it doesnt react, but limestone clearly would, and lime motar would also react. Perhaps this could be a way of testing.

Sorry Nigel - cement is heavily alkaline, and concrete definitely reacts with acid.

Found on the web:

The test to determine the cement content of concrete is given in BS 1881 : Part 124 : 1988. It requires the crushed concrete to be extracted with dilute acid and dilute alkali solution to remove the cement. The extract is then analysed for soluble silica and calcium oxide, being the two major components (expressed as oxides) of Portland cement. The cement content is determined by simple proportion from the two parameters. Where soluble components from the aggregate interfere by contributing to the calcium content (e.g. if a limestone aggregate is present) then the silica value would be used for the cement content determination. Conversely, if the silica value was inflated by some soluble component other than the cement, the lime value would be used, provided the analyst was confident that this was unaffected by soluble components from the aggregate. In practice, it is normal to analyse control samples of the aggregate, where these are available, to avoid these problems. With control samples, an accuracy of better than plus or minus 25 kg/m3 is readily achievable.

Where cement replacement materials such as pfa (pulverised fuel ash) and ggbfs (ground granulated blastfurnace slag) are present, the situation is more complex.

Nevertheless, accurate results can often be obtained using total analyses by, for example, X Ray Fluorescence methods and applying a simultaneous equations approach

Not quite so simple then

 

[JoceAndChris]

Thank you so much for all the useful pointers there.

Nigel - thank you for your ideas -in this picture the damp patch was caused by a hideous stone/ concrete (can't tell!) planter left by the previous owner. I removed it just before photographing.

Are the gutters and downpipes sound? You might even want to think of digging a trench around some of the outside wall to lower the ground level

I think the gutters and downpipes are sound, it's hard to know for sure though. The downpipe in this picture:

feeds directly into the underground rainwater tank (which is underneath the grass in that picture), and I don't think there's a problem there. The rainwater tank may be leaking, but I don't see how we can fix it easily and we're at at an impasse on that one. It's a historic, brick built tank, and we use it.

With regard to digging a trench or French drain around this wall; that's a great idea and we'd love to. I think before doing anything so major we'd need to engage a stuctural engineer, I don't want my basement walls falling in!

I also would leave that plinth alone. I think I'd be tempted to investigate a little further - take some render off, see what's underneath, see if the plinth has been stuck on later - I doubt that it has, I suspect it's integral to the wall.

I have done that elsewhere on the property, where the plinth is York stone on the front of the house. The plinth was glued on at a later date with something cementy. You can see the beigy York stone in this picture, which has been stuck on where 3 windows used to be, and now there's just one for the basement.

The heritage builder who came to quote said it would have to come off, and if I wanted it put back, put it back with lime mortar. He couldn't advise me on whether the house should or shouldn't have a plinth, or did or didn't have plinth in 1800. :?

The path just looks like old concrete to me - I'd surprised if it's anything else. Have you a loose cracked section near one edge? Lift a bit out, if you can see stones in the cross-section then it's concrete!

A great tip, thank you! So if a broken slab is powdery and chalky in cross section it's stone?

If you have a damp proof course, the path may be bridging it. You may be getting problems with rainwater splashing up from the path and saturating the plinth. The path may be laid with the fall the wrong way so the water collects or flows against the plinth.

I don't think there's a damp proof course down there. Though the slope of the hill down to the house at this point would indicate water collecting or flowing against the plinth, in practice this never happens. the land is very free draining and the rainfall in Lincs not that high. Also remember my trees, some of them huge, not very far away at all. Under that path is a complex network of roots.

How essential is the path? If it's not, and presuming it's concrete, I think I'd be tempted to take the worst section out, reduce ground levels and see if your wall dries out at all. Or you could run an angle grinder along to make a cut say 6" out from the wall, and just break out that section.

That's a great suggestion. We could hire the appropriate tools and do it in a weekend, without causing major mess and chaos. I think it would be an inexpensive job that would have tremendous benefits.

That path is not essential and certainly very ugly. The ultimate aim is to get it to match our herringbone brick path round the other side, but that's a big job for the future.

 

[Penners]

Just agreeing with the thoughts of others above - the plinth looks like stone (particularly as in one picture it is clearly in blocks, with mortar in between), while the path in that area looks like concrete (in the same picture you can see the aggregate in the bottom of some chipped, pockmarked areas).

However, it's more difficult to tell with the path in your most recent picture - the one with the flowers (agapanthus?). The slabs could be stone there.

If you're planning on lifting the concrete paths, you might want to consider replacing them with gravel, rather than bricks. This would leave the soil better able to take up and give off water. You'd also have to very careful about your choice of brick - most ordinary housebricks will sooner or later spall in the frost.

I do agree with Feltwell that you shouldn't be in too much of a hurry to take off the plinth. A bit of preliminary detective work to discover what's underneath it would be advisable.

How do you tell the difference between stone and concrete?

Rule of thumb:-

If it's got cat footprints in it, it's concrete. If it's got dinosaur footprints in it, it's stone.

 

[philpjuk100]

penners wrote
Rule of thumb:-

If it's got cat footprints in it, it's concrete. If it's got dinosaur footprints in it, it's stone.[/quote]
GREAT! :lol:

 

[JoceAndChris]

:lol: I'll look out for the dinosaur prints then!

However, it's more difficult to tell with the path in your most recent picture - the one with the flowers (agapanthus?). The slabs could be stone there.

No, they're concrete, I'm sure, because the surface has that slight bobbly look concrete can have. It's a nightmare though, it's all mixed up over the whole property, there'll be 10 concrete slabs with a rogue stone one thrown in! (The flowers are bluebells and lily of the valley)

Love the idea of a gravel path with its breathable properties, plus I believe that would be appropriate for the period- the only snag is how it would look abutting the brick path, and I love that old brick path, so wouldn't want to remove it!

Thank you for your other thoughts as well Mr P, I won't be in too much of a hurry to remove the plinth - but will see about organising some concrete removal for the New Year.

 

[Nigel Watts]

Joce you and your wonderful house keep us all fascinated!

Now why would someone go to considerable trouble and expense to fix York stone ashlar to the basement storey which cant be seen and then render the part above which can? It doesn't seem to make any sense.

When my side extension was built the soil was excavated from part of the end wall of my semi-detached house. The house is rendered brick but the external wall of the below ground basement appeared to have been faced with what looked like roofing tiles set flat against the wall. I wondered at the time if this was some early attempt at damp-proofing. Could your stone ashlar have been an attempt to do something similar I wonder? If the stone is less porous than the brick this could have made sense. If your cellar was used for storing and preserving game for his lordship in the days before refrigeration he may well have been prepared to spend a lot on it to get it just right.

The best way to check your gutters etc is to observe them in a heavy downpour.

Penners - Agapanthus flowers are like a pom-pom on the end on a long stalk. These seem more like blue bells to me.

 

[JoceAndChris]

Ashlar or plinth? Or both? :?

Joce you and your wonderful house keep us all fascinated!

Hmmm, that's very nice of you to say so, I think you're all amazing or putting up with my endless questions actually!

Now why would someone go to considerable trouble and expense to fix York stone ashlar to the basement storey which cant be seen and then render the part above which can? It doesn't seem to make any sense.

It is very puzzling, that choice. "Expense" is an assumption though. Judging by the amount and shape of the stones lying about here, either a) this house is built on the site of a previous stone building b) someone has robbed the ingredients of a derelict stone house or chapel and brought them here c) there was a stone stable?

I'll have to show you pics of those stones another time.

Aforementioned heritage builder thought a lot of salvaged materials had been used to patch up in the 20th C. As to whether the plinth is comprised of original materials - who knows? It seems curious to me that York stone is used there where Ancaster stone is used elsewhere, but then the fireplaces are Derbyshire fossil marble, so presumably there was some transportation of building materials in the 18th C for rural cottages.

 

[FamilyWiggs]

Rule of thumb:-

If it's got cat footprints in it, it's concrete. If it's got dinosaur footprints in it, it's stone.

If it's got a carbon footprint, you'll be burned at the stake. :twisted:

 

[Feltwell]

The path just looks like old concrete to me - I'd surprised if it's anything else. Have you a loose cracked section near one edge? Lift a bit out, if you can see stones in the cross-section then it's concrete!

A great tip, thank you! So if a broken slab is powdery and chalky in cross section it's stone?

Yes, basically. The main thing to look for is the aggregate that you get in concrete. If you cut concrete with a diamond saw, it looks like this:-

My desk paperweight - a core sample from the first bridge I built!

If it's broken you'll see the stones poking out:-

Ignore the pattern on the left, that's where the core drill went through a piece of steel re-inforcement.

I wouldn't rush out and hire tools straight away to break up your path, if it is concrete. As it appears to be doing quite a good job of breaking up by itself, I suspect it's not very thick - try lifting a slab up slightly with a large pry bar (something like this):-

http://www.screwfix.com/prods/29330/Hand-Tools/Bolsters-Wrecking-Bars/Wrecking-Bars/Gorilla-Bar-48

Then whilst a slab is lifted slightly clear of the ground (wedge a bit of wood under the edge if need be) give the middle a whack with a sledge hammer - if the concrete is not mega-thick it will break quite easily. Very therapeutic as well !

If that doesn't work you can still go out and hire a breaker. Don't think breakers are an easier option though, they're still hard work!

 

[JoceAndChris]

OK, that's all great advice- thanks! From your picture, concrete looks kind of pretty. It's still got to go here though. I'd sooner have gravel, which will be easy and cheap, even if not permanent. We have sledgehammer, pry bar, angle grinder, SDS drill- Chris likes his toys!

Just need a spare weekend now.

 

[Feltwell]

From your picture, concrete looks kind of pretty.

It can do, but only if the surface is ground off and it is polished - I seem to remember someone on Grand Designs doing that.

Generally it's grey and dull and lifeless!