ALCHEMY OF MORTAR

HISTORY OF LIME IN MORTAR

 

The first mortars were made from mud or clay. These materials were used because of availability and low cost. The Egyptians utilized gypsum mortars to lubricate the beds of large stones when they were being moved into position(ref. i). However, these matrials did not perform well in the presence of high levels of humidity and water. 

It was discovered that limestone, when burnt and combined with water, produced a material that would harden with age. The earliest documented use of lime as a construction material was approximately 4000 B.C. when it was used in Egypt for plastering the pyramids(ref. ii). The beginning of the use of lime in mortars is not clear. It is well documented, however, that the Roman Empire used lime based mortars extensively. Vitruvius, a Roman architect, provided basic guidelines for lime mortar mixes(ref. iii).

 

"… When it [the lime] is slaked, let it be mingled with the sand in such a way that if it is pit sand three of sand and one of lime is poured in; but if the same is from the river or sea, two of sand and one of lime is thrown together. For in this way there will be the right proportion of the mixture and blending."

 

Mortars containing only lime and sand required carbon dioxide from the air to convert back to limestone and harden. Lime/sand mortars hardened at a slow rate and would not harden under water. The Romans created hydraulic mortars that contained lime and a pozzolan such as brick dust or volcanic ash. These mortars were intended be used in applications where the presence of water would not allow the mortar to carbonate properly(ref. iv). Examples of these types of applications included cisterns, fish-ponds, and aqueducts.

 

The most significant developments in the use of pozzolans in mortars occurred in the 18th century. It was discovered that burning limestone containing clays would produce a hydraulic product. In 1756, James Smeaton developed perhaps the first hydraulic lime product by calcining Blue Lias limestone containing clay. An Italian pozzolanic earth from Civita Vecchia was also added to provide additional strength(ref. v). This mortar mixture was used to build the Eddystone Lighthouse. James Parker patented a product called Roman cement or natural cement in 1796. Natural cement was produced by burning a mixture of limestone and clay together in kilns similar to those used for lime. The resulting product was ground and stored in waterproof containers. Typically, natural cements had higher clay contents than hydraulic lime products, which allowed for better strength development. Natural cement mortar was used in construction where masonry was subjected to moisture and high levels of strength were needed(ref. vi).

 

Joseph Aspdin, an English mason/builder patented a material called portland cement in 1824. Portland cement consisted of a blend of limestone, clay and other minerals in carefully controlled proportions which were calcined and ground into fine particles. Though some portland cement was imported from Europe, it was not manufactured in the United States until 1871. The consistency and higher strength levels of portland cement allowed it to replace natural cements in mortars. Portland cement by itself had poor workability. Portland cement combined with lime provided an excellent balance between strength and workability. The addition of portland cement to lime mortars increased the speed of the construction process for masonry building due to faster strength development. Mix designs incorporating different amounts of lime and portland cement were developed. In 1951, ASTM published a Standard Specification for Unit Masonry (C270-51). This specification allowed combinations of cement and lime to be specified by volume proportions or mortar properties. ASTM C270 is still in use today. This standard identifies five mortar types based on the phrase MASON WORK S. Type M cement/lime blends have the highest compressive strength and Type K has the lowest.

 

-- More information on lime mortar specifications.

Until approximately 1900, lime putty was used in construction applications. Limestone was burned in small kilns often built on the side of a hill to facilitate loading(ref. vii). Wood, coal and coke were used as fuel. The quicklime produced from these kilns was added to water in a pit or metal trough and soaked for an extended period of time. The time required for soaking was dependent on the quality of the quicklime and could range from days to years. It was generally thought that the longer the quicklime was soaked, the better it would perform. The Standard Specification for Quicklime for Structural Purposes was developed in 1913. After the turn of the century, the use of hydrated lime products began. Water was added to quicklime at the manufacturing plant to reduce the amount of time required for soaking at the jobsite. In the late 1930's, the production of pressure hydrated dolomitic lime products began. These products required only short periods of soaking (20 minutes or less) prior to use. In 1946 the Standard Specification for Hydrated Lime for Masonry Purposes (ASTM C207) was published. This standard identified two and later four types of lime products that could be used in masonry applications. 

 

-- More information on Mason's Lime specifications.

Lime products have played a significant role in masonry construction for thousands of years. Prior to 1930, most masonry construction utilized lime based mortars. Lime has proven performance that is demonstrated by structures, such as the Great Wall of China, which have lasted for hundreds of years. The reasons for using lime in mortar 2000 years ago still remain valid today. 

 

-- More information on Lime-based mortars in modern masonry construction.

BRIEF HISTORY OF ALCHEMY

Alchemy was born in ancient Egypt, where the word Khem was used in reference to the fertility of the flood plains around the Nile. Egyptian beliefs in life after death, and the mummification procedures they developed, probably gave rise to rudimentary chemical knowledge and a goal of immortality.

By 332 BC, Alexander the Great had conquered Egypt. Greek philosophers became interested in the Egyptian ways. Greek views of how matter is made up of the four elements of nature - Fire, Earth, Air and Water, were merged with the Egyptian sacred science. The result was Khemia, the Greek word for Egypt.

When Egypt was occupied by the Arabs in the 7th Century, they added 'al-' to the word Khemia and al-Khemia meaning 'the Black Land' is now seen as a possible origin for the word alchemy. The Greek word khumos, meaning 'fluid' has been suggested as an alternate origin for the word alchemy, there is as yet no consensus on the matter. It is unfortunate that more is not known about this early period in the history of alchemy. In 391, invading Christians burned the great library in Alexandria, destroying many relevant works.

Alchemy was also developed independently in China by Taoist monks. The monks pursued both the outer elixir and the inner elixir. The former being minerals, plants etc. which could prolong life, and the latter being the use of exercise techniques, such as Qigong, to manipulate the chi or life force of the body.

Like China and Egypt, India developed alchemy independently. They had beliefs similar to the Chinese, in that they used external and internal methods to purify the body and prolong life. In their work the Indians invented steel and long before Bunsen and Kirchhoff's work, realised the importance of flame colour in the identification of metals.

The introduction of alchemy to the west came in the 8th Century when the Arabs brought it to Spain. From here it quickly spread to the rest of Europe.

 

The Arabian belief was that metals are made up of mercury and sulfur in varying proportions. Gold was seen as the perfect metal and all others were less perfect, an idea popular among western alchemists. It was a very popular idea indeed, that these lower metals could be transmuted into gold by means of a substance known as the Philosophers Stone.

 

The Stone is also believed to be able to confer immortality, the Chinese name for it being the Pill of Immortality.

In Europe, alchemy led to the discovery of manufacture of amalgams and advances in many other chemical processes and the apparatus required for them. Eventually, by the 16th Century, the alchemists in Europe had separated into two groups.

 

The first group focussed on the discovery of new compounds and their reactions - leading to what is now the science of chemistry.

 

The second continued to look at the more spiritual, metaphysical side of alchemy, continuing the search for immortality and the transmutation of base metals into gold.


This led to the modern day idea of alchemy.