Edinburgh Napier University

  The term "lime" comes from the word limestone. Limestone rocks were
converted to lime powder by burning (calcining). The process of converting
limestone to lime was an old process and it has been well documented,
archaeologically. It has been established that the production of lime is the oldest
industrial process can"ied out by humankind, dating back thousands of years. In
fact, 3650 years ago Moses instructed the people of Israel, after they crossed the
Jordan River, to set up large stones and whitewash them with lime and write the
laws of God in lime.
Lime was the most commonly used cementatious binder until about a century
ago, when its use started to decline. It was replaced by Portland cement, a
material essentially developed for structural purposes in the era of the industrial
revolution. Portland cement has certain advantages over lime. The material
develops strength and hardens faster for work to be carried out at a greater pace
with better quality control and agreed standards. It has now become the dominant
cementitious binder, part of it due to aggressive marketing of the material by the
manufacturers. The use of Portland cement in the restoration and conservation of
old buildings and structures in the UK over the past few years has resulted in a
series of problems and cost millions of Pounds to eradicate.
The decline in the use of lime in many countries has not only caused a diminution
of its production, but has also contributed to a gradual disappearance of the
traditional skills required both to produce a high quality product and to use it in
construction. Therefore it is necessary to reintroduce and revive the old tradition of using lime by providing more information about its production and use.
At present there are no comprehensive standards or code of practices, British or
European to aid engineers and contractors in the use of hydraulic and non
hydraulic limes in construction. BS EN 459 (2001) gives guidance on the
chemical and physical properties of limes but it does not provide vital
information about lime-based mortars e.g. mix proportions, mixing process, bond
with masonry units, curing methods and all other necessary aspects to assess in
the use of the material in construction. At present it is very easy for engineers,
contractors and consultants to misuse lime mortars in new construction or in
restoration and conservation of old buildings. Part of the decline in production of
lime and reluctance of use in construction is due to the lack of understanding of
the material properties and its performance in structures. Therefore it is necessary
to examine and revive the old tradition in using lime mortars in construction and
look at the new technologies used presently in the production process in order to
provide the necessary background and information to aid the use of the material The present study provides a literature review, test results, discussions,
conclusions and background information to set up standards in the production
and use of hydraulic and non-hydraulic limes and their mortars in the
construction of new buildings and the restoration and conservation of old
buildings. Hydraulic and non-hydraulic limes have an excellent track record in
buildings through history but their use in the UK was missed for some thirty
years or more. Part of the reason for undertaking this research programme was to
examine the properties of pre-packaged hydraulic limes available in the market at present. The properties of limes vary considerably dependent on the raw
materials, composition and manufacturing process. The results of this study
showed that there was a great variation in the properties and performance of
limes and their mortars. The results also showed that the properties of lime
mortar improved by adding different percentages of POliland cement.
The research examined the effect of sand grading on the lime mortars
compreSSIve, splitting and brick/mortar bond strength. The thesis also
investigated the effects of using different casting moulds and curing methods on
mortar strength. The results showed that the porosity of lime mortar was one of
the reasons it was a success in the past and why it was so important nowadays to
use it in the restoration and conservation of historic buildings.