Lime mortar is one of the oldest and most durable building materials. Great Wall, China, had sections built 520-615AD, by ramming earth/lime/sand&small stones. Romans used lime to build complex forms such as The Colosseum and Pantheon; the latter ready in 125 AD is one of the best-preserved marvels from that era. It survived 2000 y of corrosion and natural disasters. Around 4000BC Egyptians used lime for plastering the pyramids.
Lime in modern buildings is fast growing as the ecological qualities of lime is demanded in eco-focused building projects. It also matches brick, stone, and can be used alongside other materials such as hemp or straw bales.
Lime mortar is breathable allowing water to pass through a building thereby avoiding a build-up of moisture within the fabric and the risk of damp. It allows evaporation of rising and penetrating damp from within the wall. It is due to the open pore structure of the material which allows a free flow of moisture.
Cement is less porous, so its use seals a building envelope. It is much harder than soft brick or stone and this prevents needed settling or movement of a building which results in cracking. When this mortar cracks, water seep into the cracks and moisture won’t be able to evaporate. It results in the loss of an entire face of stone or brick.
Lime mortar is CO2 friendly. Limestone is burnt at 850oC, cement at 1300o; it uses much less energy. It is made on small scale plants, with lower transportation costs. Low energy and vulnerable materials such as earth construction and straw bales are protected by adding small quantities of lime. Some of the CO2 emitted at the firing is re-absorbed by the lime as it hardens, and this continues throughout its life.
Lime mortar production does not damage the quality of our air, water, land, or soil. Because it is a natural material there is no leaching damaging chemicals, it can be used near watercourses. At the end of life, lime mortar is recyclable to bricks, stone & other materials to be disposed of as a single package, as opposed to concrete or cement.
As lime mortar is a flexible material, it will move with a building as thermal expansion or contraction or earth-quakes occurs. If cement is used, cracks will develop, and the material will move away from the substrate. By using lime into the mix, a gradual micro-cracking will occur, self-repairing, as the lime diffuses into the minute fissures and hardens when reacting with CO2 (debonding).
In Portugal we have plenty of limestone in Anadia, Mealhada, Cantanhede, Benedita, Arrábida, Sesimbra. In the Algarve around São Brás and Loulé.
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