In response to the commnets about the development of the compressive strength of lime mortar over time, the St Astier Data Shhet for NHL 5 100% chaux gives:
Product specification: pure and natural hydraulic lime. Contains no additives.
Conforms to European Norm (EN 459) and French Norm NFP 15.311
Strength factor: 5 (Eminently hydraulic) Whiteness index: 67
Residue @ 0.09 mm: 7% Surface cover (cm2per gram): 8000
Density (volumetric weight) typical. 700 gr. / litre Expansion : < 1mm
Available (free) lime Ca(OH)2 after slaking: 15-20% Residue of quick lime after slaking: < 1%
Shelf life: 8-12 months kept sealed and dry Packing: 30kg. Bags
MORTARS Compressive Strength N/mm2 Elasticity Moduli (Mpa)
MIX RATIO EN459* 1 : 2 1 : 2.5 1 : 3 1 : 2 1 : 2.5 1 : 3
7 Days 1.96 1.00 0.88 n/a n/a n/a
28 Days 5* 2.20 2.00 1.5 10800 11000 10000
6 Months 7.31 5.91 5.31 18000 17050 16900
12 Months 9.28 8.84 6.50 18510 17280 16150
24 Months 10.81 8.81 7.8 21500 18020 17430
Consumption for 1m2
of mortar Kg +/- 10%
350 280 233
*Incoming European Norm EN 459 (mortar ratio 1:1.3 with ISO 679 Sand)
Mixing: can be mixed in cement mixers.
Application by spray gun: possible. Please consult us.
Working temperatures: not below 5oC or above 30oC. Make sure that high suction materials are thoroughly
dampened before application. Avoid rapid drying due to high temperatures or strong winds by curing with a
light water mist several times a day if necessary. See "Protecting NHL Mortars".
SUITABLE FOR LATH WORK / LIME CONCRETE/INJECTION/GROUTING:see relevant sheets.

Much of the discussion so far in this forum could be made totally redundant if the construction industry were to adopt GEOPOLYMERS.
Geopolymers are inorganic polymers of silicate minerals ( e.g quartz, feldspar etc - the skeleton if you like), chemically bonded by an alkaline sodium silicate/sodium hydroxide paste (or plasma), that sets at almost ambient temperatures. Almost no CO2 is involved except perhaps in the transport of the raw materials, and the material has a longish history of use by the likes of the US Corps of Engineers, Nasa, and the nuclear waste industry. Details of the process etc can be found at Prof Joseph Davidovits Geopolymer Institute site:
http://www.geopolymer.org/category/science
and details of the geopolymerization process at http://www.geopolymer.org/science/about-geopolymerization
Davidivits has eveb suggested that the limestone blocks making up the Pyramids were in fact cast in situ geopolymers, using phytolithic material -alkaline plant ash - as the plasma.
The major limitations to date are the cost of the alkaline solutions. The potential major advantages are that is is almost carbon free, can be readily moulded and shaped, and is almost indentical in appearance to 'normal' geological material.
Both NASA and CSIRO in Australia are actively researching the material, and technical publications on its properties are obtainable online from Curtain University of Technology, Australia via
http://www.geopolymer.org/index.php?page_id=46

Perhaps the future is with geopolyners and Astrogels!

I've just come across this YOUTUBE video by Davidovits, which certainly gives food for thought!
http://www.youtube.com/watch?v=znQk_yBHre4