On Thu, 14 Dec 2023 16:51:48 +0000, Max Demian
<max_demian@bigfoot.com> wrote:

>On 14/12/2023 14:22, Ottavio Caruso wrote:
>> Am 14/12/2023 um 13:26 schrieb Max Demian:
>
>>> I think the Colosseum (and many other Roman buildings) is stone with a
>>> concrete infill isn't it? The Pantheon is a rare example of concrete
>>> cast in shutters.
>>>
>>> They used the infill method for medieval cathedrals, but, in this
>>> case, the infill would either be rubble or lime mortar concrete, which
>>> could take literally centuries to harden completely, as this requires
>>> CO2 to migrate in and change the Ca(OH)2 to CaCO3.
>>>
>>
>> Not a civil engineer, but we used to have a "geometra" (roughly =
>> chartered building surveyor) in the house.
>>
>> I was told, when I was little, that "concrete" (in Italian "cemento" or
>> "cemento armato" or even better "calcestruzzo armato") is different from
>> "cement" ( = "calcestruzzo").
>>
>> The name "concrete" is supposed to be used only for the mix of cement
>> and steel for XX century kind of high rise concrete buildings or bridges.
>>
>> You can build a 1 or 2 floor house with cement and stones without steel
>> reinforcement.
>>
>> I am sure civil engineers in UK and in Italy use different and possibly
>> confusing terminologies.
>
>Cement is the binding material, e.g. Portland cement which is supplied
>as a fine powder. The word is also used for glues generally.
>
>Concrete is cement plus aggregate, i.e. sand and stones of various
>sizes, i.e. gravel. Coarse aggregate is also called ballast, from its
>use to stabilise unladen ships.

And then there is mortar, which in my understanding is a simple
cement-sand mix of various proportions depending on application, but
which doesn't contain 'aggregate' as such.

--
Chris

On 14/12/2023 17:44, Chris Hogg wrote:
> And then there is mortar, which in my understanding is a simple
> cement-sand mix of various proportions depending on application, but
> which doesn't contain 'aggregate' as such.

The whole point of concrete is to have stones, which are strong, and
fill in the gaps with smaller stones, which are strong and then fill the
gaps in those with sand, which is strong and finally to fill in the gaps
in the sand with cement, which isn't very strong!

--
It is the folly of too many to mistake the echo of a London coffee-house
for the voice of the kingdom.

Jonathan Swift

On Thu, 14 Dec 2023 18:06:08 +0000, The Natural Philosopher
<tnp@invalid.invalid> wrote:

>On 14/12/2023 17:44, Chris Hogg wrote:
>> And then there is mortar, which in my understanding is a simple
>> cement-sand mix of various proportions depending on application, but
>> which doesn't contain 'aggregate' as such.
>
>The whole point of concrete is to have stones, which are strong, and
>fill in the gaps with smaller stones, which are strong and then fill the
>gaps in those with sand, which is strong and finally to fill in the gaps
>in the sand with cement, which isn't very strong!

Quite. Use of aggregate, which is generally cheap, saves a lot of
cement, which generally isn't.

--
Chris

"Max Demian" <max_demian@bigfoot.com> wrote in message
news:ulfbr4$1f3ep$1@dont-email.me...
> Cement is the binding material, e.g. Portland cement which is supplied as
> a fine powder. The word is also used for glues generally.
>
> Concrete is cement plus aggregate, i.e. sand and stones of various sizes,
> i.e. gravel. Coarse aggregate is also called ballast, from its use to
> stabilise unladen ships.

I would tend to use "cement" for the grey anhydrous powder - and NEVER for
the hydrated solid: only Americans have that meaning.

Cement plus sand (mixed with water to hydrate it) gives mortar

Cement plus sand plus gravel (mixed with water to hydrate it) gives concrete

On Wednesday 13 December 2023 at 10:05:28 UTC, Robin wrote:
> On 13/12/2023 08:53, Chris Hogg wrote:
> > On Wed, 13 Dec 2023 07:40:32 -0000 (UTC), Jethro_uk
> > <jeth...@hotmailbin.com> wrote:
> >
> >> I wonder how easy this would be to knock up as a hobbyist ...
> >>
> >> https://www.msn.com/en-gb/travel/news/the-secret-ingredient-in-roman-
> >> concrete-that-means-buildings-can-last-for-millennia/ar-AA163dEr
> >>
> >>
> >> The durability of Roman concrete, which has allowed structures such as
> >> the Pantheon in Rome to remain standing for nearly 2,000 years, has long
> >> baffled experts.
> >>
> >> But scientists now believe they have rediscovered a secret ingredient in
> >> the ancient recipe that makes the building material self-healing –
> >> quicklime.
> >>
> <snip>
>
> >>
>
> >
> > This is nothing new. The use of volcanic ash in concrete by the Romans
> > has been known for a long time. The ash comes under the general name
> > of a pozzolan. Other pozzolans are available.
> >
> > See also
> > https://www.google.com/search?client=firefox-b-d&q=volcanic+ash+in+concrete#ip=1
> > and
> > https://www.google.com/search?client=firefox-b-d&q=pozzolan
> >
>
> Quicklime is not a pozzolan. The proposition is that the Romans used
> quicklime to give something over and above the effects of pozzolanic
> reactions. Clearer in the original paper[1] which includes the results
> of their modern mixing.
>
> As for the OP's question, I've no hands-on experience but hot mixing
> with quicklime is still done by hand to make mortar for heritage
> buildings. But needs care.
>
>
> [1] https://www.science.org/doi/10.1126/sciadv.add1602

We've known for a long time it was based on lime. The secret ingredient to longevity appears to be rice or similar.

On 14/12/2023 18:24, Chris Hogg wrote:
> On Thu, 14 Dec 2023 18:06:08 +0000, The Natural Philosopher
> <tnp@invalid.invalid> wrote:
>
>> On 14/12/2023 17:44, Chris Hogg wrote:
>>> And then there is mortar, which in my understanding is a simple
>>> cement-sand mix of various proportions depending on application, but
>>> which doesn't contain 'aggregate' as such.
>>
>> The whole point of concrete is to have stones, which are strong, and
>> fill in the gaps with smaller stones, which are strong and then fill the
>> gaps in those with sand, which is strong and finally to fill in the gaps
>> in the sand with cement, which isn't very strong!
>
> Quite. Use of aggregate, which is generally cheap, saves a lot of
> cement, which generally isn't.
>

The size and type of the aggregate determines the compressive
strength of the concrete mix