A further point about lime mortar. It sets quite hard within a few weeks, but continues to get harder & harder at an exponentially slower rate until the carbon dioxide (as carbonic acid) in the atmosphere eventually converts it back to its original calcium carbonate. So Roman mortar is very very hard and totally inflexible…. Yes!, it can take thousands of years to re-convert - this is one of the reasons why ancient buildings (as Roman aqueducts) last so long. The conversion is quicker in cold climates since frost makes micro cracks which allows the carbonic acid to percolate into the mortar.
CaCO3 (limestone) ---heat---> CaO (quicklime)+ CO2 CaO (quicklime)+ H20 ---> Ca(OH)2 (slaked lime) CO2 + H2O --- in the atmosphere ---> H2CO3 (carbonic acid - very weak) Ca(OH)2 (slaked lime) + H2CO3 + O2 ---- time ---> CaCO3 (limestone) + 2H20 My chemistry is very rusty - so I hope the formulae are right All the best Kevin On 6 May 2013, at 15:32, Frank Evans <frankev...@zooplankton.co.uk> wrote: > Greetings, fellow dialists, > I'm now clearer on the subject of lime production. After firing It seems the > quicklime was taken from the kiln in lumps, separated from the ash and moved > to a pit in the nearby slaking shed (cheaper than iron pots). The pit was > lined to hold water and the quicklime was (cautiously!) added. It was in > timer bailed out and sieved (large lumps might not be completely slaked and > could "blister" later as mortar, with damaging consequences. The resulting > slaked lime could now be safely transported. Each firing produced several > tons of lime and this was sometimes left to mature for many weeks. > > Thanks to all who replied. I hope to talk further on the subject with the > stonemason when he returns to Tynemouth in the summer to paint the dial. I > note he was careful to chose the correct colour of sand to mix with his lime > putty for the repairs. > Frank 55N 1W > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial >
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