From Newsgroup: rec.crafts.metalworking

Thanks everyone for entertaining my posts about welding, generators
and offgrid electric power, etc., etc.

I have come in and looked at replies.

Silence has been I have been lime-mortar'ing, and using lime in
another niche application I came across - "mud" mortar -
subsoil-mortar - used in local natural stone construction here in
Cornwall (and around Britain historically, it seems).

Lime-mortar you can buy as a premix in sacks. Apparently the lime
component is already slaked through to CaOH - which is dried so is a
powder - but which otherwise holds all the right characteristics.
Giving you an easy-to-use much less hazardous material to work with.
Took me ages coming from nothing to having some idea what to use.
Then at a basic level the meaning of the terminologies.

The "subsoil-mortar" had me doing "hot-mix lime".
Lime component goes in as the quicklime, CaO, as it comes out of a
lime-kiln. Its heat of hydration is notorious - leading to name
"hot-mix". Seeing is understanding...

I at least somewhat see now how in Roman "hydraulic mortars" - mortars
which have a self-setting reaction "within themselves" after
hydration, not solely relying on drying and/or reaction with
carbon-dioxide in the atmosphere (as lime tries to revert to
limestone) - are "clever". Roman mortar on quays / harbours in
seawater have lasted 2 millennia and remain sound. It was thought
unreacted quicklime was "careless" hot-mixing. I can now at least
kind-of see what has recently been realised - that feature is
deliberate. It gives a self-healing mechanism, by having a reservoir
of quicklime to chemically react and self-heal if there is structural settlement etc.

So have been preoccupied.
While being grateful for help & guidance which came-in on topics I have
asked about.

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From Newsgroup: rec.crafts.metalworking

"Richard Smith" wrote in message news:m1v7914chu.fsf@void.com...

I at least somewhat see now how in Roman "hydraulic mortars" - mortars
which have a self-setting reaction "within themselves" after
hydration, not solely relying on drying and/or reaction with
carbon-dioxide in the atmosphere (as lime tries to revert to
limestone) - are "clever". Roman mortar on quays / harbours in
seawater have lasted 2 millennia and remain sound. It was thought
unreacted quicklime was "careless" hot-mixing. I can now at least
kind-of see what has recently been realised - that feature is
deliberate. It gives a self-healing mechanism, by having a reservoir
of quicklime to chemically react and self-heal if there is structural settlement etc.

-----------------------------------
The Romans were fortunate to have this volcanic ash nearby: https://en.wikipedia.org/wiki/Pozzolan

My understanding is that the unreacted quicklime dissolves in water leaking through cracks and deposits like cave stalactites when the water evaporates
at the exposed end.

In Germany I saw concrete from the rushed construction of the 1930's and
40's that was already crumbling, plus ancient work that wasn't.

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From Newsgroup: rec.crafts.metalworking

On 8/23/2026 4:45 AM, Jim Wilkins wrote:

"Richard Smith"-a wrote in message news:m1v7914chu.fsf@void.com...

I at least somewhat see now how in Roman "hydraulic mortars" - mortars
which have a self-setting reaction "within themselves" after
hydration, not solely relying on drying and/or reaction with
carbon-dioxide in the atmosphere (as lime tries to revert to
limestone) - are "clever".-a Roman mortar on quays / harbours in
seawater have lasted 2 millennia and remain sound.-a It was thought
unreacted quicklime was "careless" hot-mixing.-a I can now at least
kind-of see what has recently been realised - that feature is
deliberate.-a It gives a self-healing mechanism, by having a reservoir
of quicklime to chemically react and self-heal if there is structural settlement etc.

-----------------------------------
The Romans were fortunate to have this volcanic ash nearby: https://en.wikipedia.org/wiki/Pozzolan

My understanding is that the unreacted quicklime dissolves in water
leaking through cracks and deposits like cave stalactites when the water evaporates at the exposed end.

In Germany I saw concrete from the rushed construction of the 1930's and 40's that was already crumbling, plus ancient work that wasn't.

So the answer to the long lasting Roman concrete is its self healing?
--
Bob La Londe
CNC Molds N Stuff
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From Newsgroup: rec.crafts.metalworking

"Bob La Londe" wrote in message news:116f8fr$232a2$1@dont-email.me...

On 8/23/2026 4:45 AM, Jim Wilkins wrote:

...Roman concrete...

So the answer to the long lasting Roman concrete is its self healing?
Bob La Londe

--------------------------------

Elsewhere I've read that we still aren't certain, we have the final product but are unsure of the raw materials or mixing process. For instance the properties of modern concrete vary with the amount of water in the mix.

Vitruvius described What the Romans accomplished but rarely How, it reads
like boring ad copy. The Hows passed by example from master to illiterate young apprentice, and were valuable trade secrets. The oldest how-to books that I have copies of are less than a thousand years old. Besides Roman concrete some remaining uncertainties are Hindu Wootz sword steel, Egyptian granite obelisk carving, exquisite Etruscan gold jewelry and Roman catapult torsion windings, though I may have solved the last.



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From Newsgroup: rec.crafts.metalworking

On 8/23/2026 3:25 PM, Jim Wilkins wrote:

Elsewhere I've read that we still aren't certain, we have the final
product but are unsure of the raw materials or mixing process. For
instance the properties of modern concrete vary with the amount of water
in the mix.

That's what I heard, and what I was getting at. I wondered if you were
aware of some newer information on the subject.
--
Bob La Londe
CNC Molds N Stuff
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From Newsgroup: rec.crafts.metalworking

Bob La Londe <none@none.com99> writes:

On 8/23/2026 3:25 PM, Jim Wilkins wrote:

Elsewhere I've read that we still aren't certain, we have the final
product but are unsure of the raw materials or mixing process. For
instance the properties of modern concrete vary with the amount of
water in the mix.

That's what I heard, and what I was getting at. I wondered if you
were aware of some newer information on the subject.

"self-repairing" - seems yes.
For natural stone buildings, there are several reasons cited for using lime-mortar, of which "self-repairing" is but one, albeit crucial.

Zooming to a big context - stone buildings have been reliable for
centuries into millenia... Then we have the "panacea" of Portland
cement mortar - and in a very few decades we are seeing a rash of
problems. Mysterious absent before. Okay there wasn't Portland cement
mortar before the second industrial revolution - essentially the 1880's
and strongly into the 1890's (?) - but the overall view is builders of
old knew what they were doing; funnily enough, now we care to look back
and consider the matter.

Some key characteristics of a mortar for natural stone, as I have
gathered:
* must not be harder / stronger than the stone it is joining - else the
stones will crack with {thermal cycling, fluctuating moisture levels, settlement of the building, etc.} (all dimensional changes)
* must do the right thing with moisture - not let too much in, and let
what shouldn't be there out
* must self-heal with settlement and flexure of the building - given a
stone building is flexible and historic foundations despite being sound
not being the stiff almost immutable hard raft of modern poured concrete foundations (the "modern" building is almost floating free of the
dynamics of the ground it is on (?)).

What I am seeing is that a natural stone building with Portland cement
mortar pointing will develop a number of long cracks rising or
zig-zagging across extents of wall. Contributing to moisture / water
problems with the building.
It is my impression (I am at at early stage of learning) that a natural
stone building on a natural good but somewhat dynamic foundation will
have distributed flexure and the lime-mortar will self-heal, not showing "failure of the pointing".

I am at such an early stage of learning.
There is not basis by which I can express strong opinions.

Regards,
Rich Smith
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From Newsgroup: rec.crafts.metalworking

"Richard Smith" wrote in message news:m1ecfmpm8b.fsf@void.com...

...but the overall view is builders of

old knew what they were doing; funnily enough, now we care to look back
and consider the matter.
----------------------

https://en.wikipedia.org/wiki/Ponte_Morandi
"Traditionally, bridges were designed for a 50-year lifespan; the bridge failed just under 51 years after its opening."

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From Newsgroup: rec.crafts.metalworking

"Jim Wilkins" <muratlanne@gmail.com> writes:

"Richard Smith" wrote in message news:m1ecfmpm8b.fsf@void.com...

...but the overall view is builders of

old knew what they were doing; funnily enough, now we care to look back
and consider the matter.
----------------------

https://en.wikipedia.org/wiki/Ponte_Morandi
"Traditionally, bridges were designed for a 50-year lifespan; the
bridge failed just under 51 years after its opening."

My own perception:

there is a "Darwinian selection" in engineering;
in that you cannot fully anticipate the intersection and interaction of
all variables.
So you must accept that something like maybe 10% of ambitious structures
will need early replacement - and there is no way of getting around
that, given a world of conservatisim will make your economy and society uncompetitive.
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