Limestone is a key ingredient of quicklime, mortar, cement, and concrete. The solubility of limestone in water and weak acid solutions leads to important phenomena. Regions overlying limestone bedrock tend to have fewer visible groundwater sources (ponds and streams), as surface water easily drains downward through cracks in the limestone. While draining, water slowly (over thousands or millions of years) enlarges these cracks; dissolving the calcium-carbonate and carrying it away in solution. Most well-known natural cave systems are through limestone bedrock.

Limestone is very common in architecture, especially in North America and Europe. Many landmarks across the world, including the Great Pyramid and its associated Complex in Giza, Egypt, are made of limestone. So many buildings in Kingston, Ontario, Canada were constructed from it that it is nicknamed the ‘Limestone City’.  On the island of Malta, a variety of limestone called Globigerina limestone was for a long time the only building material available, and is still very frequently used on all types of buildings and sculptures. Limestone is readily available and relatively easy to cut into blocks or more elaborate carving. It is also long-lasting and stands up well to exposure. However, it is a very heavy material, making it impractical for tall buildings, and relatively expensive as a building material.

Source: Wikipedia

The term "Portland Cement" was coined by Joseph Aspdin who in 1824 patented a hydraulic binder created by burning a mixture of limestone and clay, resembling the previously existing Roman cement and presenting a texture very close to that of the oolitic Portland stone.

Portland’s freestone has almost certainly been used as a building material since Roman times. The many well crafted Roman sarcophagi (stone coffins and matching lids, hewn from single large blocks of Portland stone) that have been unearthed locally over the years, testify to the skill of their makers. It is interesting to speculate where the many large blocks of stone needed to make the sarcophagi were obtained and how they were transported.

It is possible that stones came from coastal exposures, where they may have been dislodged by the action of the sea, nevertheless the skills necessary to select suitable blocks, retrieve them, shape and hollow them are considerable and hint at an industry of some maturity. Were the sarcophagi "made to order" following someone’s death? Considering the amount of work and more critically, length of time involved, this would seem unlikely because of the practical need to carry out a burial promptly after death. Is it possible then, that during Roman times, there was a stone industry on Portland producing "off the shelf" sarcophagi?

The earliest known building to be constructed using Portland stone is Rufus Castle at Church Ope Cove, Portland. The original structure was probably built in around 1080, rebuilt in around 1259 and rebuilt yet again in about 1450 which is the likely date of the walls we see today.

Source: Wikipedia

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