In my part of the world lime mortar joints in brickwork (Victorian/Edwardian houses) are very much thinner than those done with Portland cement. Around 5mm as opposed to 10/12mm. Just why this was so I have no idea but would be interested to learn.
Tony M. -----Original Message----- From: Jack Aubert <j...@chezaubert.net> To: 'Kevin Karney' <kar...@me.com>; 'Sundial' <sundial@uni-koeln.de> Sent: Wed, 15 May 2013 1:04 Subject: RE: Re quicklime This is all fascinating stuff and I will either impress or borepeople with my bogus erudition on the subject. But Is there an easy way to distinguish lime mortar from Portlandcement mortar, like with one’s thumbnail? In America, the oldest brickbuildings on the East Coast are from the mid 18th century but theywould generally have been re-pointed with Portland cement. Last weekend Iwas checking mortar joints in Alexandria, Virginia, where the oldest buildingsdate from that period. They all seemed to have the same sandyconsistency. I jokingly told a homeowners that I was the “mortarinspector”. He replied “Finally! We’ve been waitingforever!” Jack From: sundial[mailto:sundial-boun...@uni-koeln.de] On Behalf Of Kevin Karney Sent: Monday, May 06, 2013 2:39 PM To: Sundial Subject: Re: Re quicklime A further point about limemortar. 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 toits original calcium carbonate. So Roman mortar is very very hard and totallyinflexible…. 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 frostmakes 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 theformulae 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 thequicklime was taken from the kiln in lumps, separated from the ash and moved toa pit in the nearby slaking shed (cheaper than iron pots). The pit was lined tohold water and the quicklime was (cautiously!) added. It was in timer bailedout and sieved (large lumps might not be completely slaked and could"blister" later as mortar, with damaging consequences. The resultingslaked lime could now be safely transported. Each firing produced several tonsof 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 thestonemason when he returns to Tynemouth in the summer to paint the dial. I notehe was careful to chose the correct colour of sand to mix with his lime puttyfor the repairs. Frank 55N 1W --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial -- This message has been scanned for viruses and dangerous content by MailScanner,and is believed to be clean. -- This message has been scanned for viruses and dangerous content byMailScanner, and is believed to be clean. --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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