The Ancient Origins of Limestone
Limestone a mainly sedimentary rock or calcium carbonate as it’s known chemically (CaCO3) is formed when many many sea creatures with protective shells fall to the ocean floor to decompose.
Limestone most commonly can be found around ancient water courses, oceans from millions of years ago and so forth, finding calcium carbonate in caves is common and you’ll see these in the form of stalagmites and stalactites, with a rich white coating, sometimes yellow or brown. This process takes millions of years, back to the most recent ice age of around 2.6 million years ago and beyond.
Pressing fast forward on our tape deck, VHR, DVD and now digital device, we find modern limestone quarries on the sites of those ancient water courses.
The Evolution of Lime Usage in Britain
This wasn’t always the case, lime quarries and lime burning started in the uk in the 16th century and the process would’ve been indeed much more labour intensive, used largely in agriculture, construction and even to ward off scurvy in the British Navy. Once you start reading and falling in love with lime like me, it will take you on a journey with many avenues and alleyways.
A Builder's Curiosity
A question I have asked myself time and time again!
How did our ancestors have the tenacity to burn limestone, add water, make a putty, then add an aggregate to create a mortar that has lasted hundreds of years?
The Historical Timeline of Lime
Official records show lime being used in ancient Egypt around 6000 years ago, Turkey and famously Rome which dates a little further down the timeline.
Lime in a mortar when it’s combined with or without an aggregate has stood the testament of time, whether it’s plastering the Giza pyramids or farmer jack lime washing his cow shed. The numerous qualities of lime were and still are unrivalled as a construction material to this day.
Most famously and well documented is the use of lime by the romans. Having visited Rome & Paletine Hill I’ve seen first hand of how well preserved these early structures are, and it’s just glorious, although relatively new in the history of lime in construction.
I also found this the case when visiting the Turkish amphitheatre of Aspendos which to name a few saw Alexanda the great do battle in 333 BC!
Understanding Modern Lime Applications
Turning our focus back to lime, we find it at the heart of all buildings dating from 4000 years ago to around 1900, although there is evidence of cement use and even earlier gypsum mines in the UK.
One of the advantages of lime is its low carbon footprint, the energy it takes to produce is minimal and how it re absorbs carbon dioxide once mixed.
The Technical Side of Lime Mortars
Now to its qualities when used as a mortar,
Lime when mixed with an aggregate such as a sharp sand combined with a reinforcement of horse hair for example gives such strength and flexibility. If you’re living in a home that was built prior to around 1919 you’re probably surrounded by it right now.
A pure limestone when burnt in a kiln will produce quicklime, kibbled, slaked and ready to use as the ultimate mortar for all uses, we call this a non hydraulic lime.
This quicklime gives the upmost flexibility, breathability and permeability.
A limestone historically with natural impurities such as clay or whatever else was found to be in the ground is what we call an NHL Lime, naturally hydraulic lime. This lime gives a reduced quality of flexibility, breathability etc but a faster cure or setting time.
Jumping back to the Romans, it’s been discovered that the ultimate builders were extremely active in experimenting with quicklimes, NHL and what we call pozalans. Combining and concocting mortars that give the advantages of a quicklime in parts but also the advantages of the quicker curing NHL mortars, plus some brick dust or whatever was to hand.
“Historically I’d like to know how our ancestral builders knew how pure the lime was? Was it purely on colour? Texture ? Reaction when burnt, so many questions still to answer even now”
Modern Building Practices and Lime
You’ll also see more often than not “builders” adding a hydrated lime to their mortar to create a “lime mortar” ! The hydrated lime you find in the merchants started off as a quality quicklime but has been mixed with the exact amount of water to complete the lime cycle and has turned back to a powder, so its qualities have already been spent. Soaking the hydrated lime in water for a period of time to once again turn this back to a putty would be the best option.
These days the world of heritage has been inundated with what I’ll call lime products, many try to combine the quicklime and NHL qualities with an added bit of chemistry with a healthy splash of sales jargon, but none can rival the ultimate and original lime mortar.
A Personal Perspective: Lime in Ancient Turkey
Having been asked to write this article I racked my brains and my personal archive of pictures regarding lime in landscaping, it wasn’t long before I was taken back to my time in Perge, the ancient region of pamphylian in Turkey.
The 22 metre wide streets, lined with a slightly yellow limestone that has the wear and tear of pedestrians and ancient vehicles alike. The streets are lined with porticos that are paved beautifully with mosaics all laid on lime mortar, laid in geometric patterns which are made of a variety of colourful limestone, marble and terracotta.
The columns that line the two main streets tower high into the sky, the bases from what i remember are made from Prokonnesos marble, in the attic ionic style, the pedestals themselves are made from limestone and cut to a rectangular or octagonal shape.
“Just writing this has me itching for another lime based adventure”
Conclusion
So it’s right there under our noses, under our feet and behind a lot of our walls.
Lime, the backbone and the heartbeat of construction for thousands of years.
