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September 4, 2010 - One of things that struck me in an earthship is the frequent use of cement. Cement is used in the spacer blocks, the anchoring of the connecting beams, the cans and glass walls, the walls of the greywater planters, foundations for these walls, parts of the plaster mix for the wall etc.

Given the production of cement involves the necessary pollutant emissions and often also industrial, and sometimes even toxic waste is added in the production of cement, I went looking for an alternative.

My quest first went direction past. Did the Romans not develope a type of concrete? How did they do this? Did people in medieval times not build brick houses? Is it not true that, even in the present, there are several of these buildings stil standing? And did not most of the people use local materials to realize their buildings (buildings with large prestigious slant aside)?

My experience with old techniques, in any case, is that things often are resolved more ecologically and within reach of everyone. Perhaps in the past we can find solutions for the future.

The Romans and lime

Although mortars where already used by the Egyptians, the Babylonians and the Greeks, the development took a boom with the Romans, who developed a mixture of water, lime, rubble and volcanic soil¹.

What actually happened is that the Romans adopted the Greek knowledge about lime mortars (a mixture of volcanic deposits with quicklime and sand). The Romans discovered that the volcanic ashes at the foot of the Vesuvius, near Pozzuoli, combined with lime created a very sufficient hydraulic reaction. The mortar, composed of these elements, was called "Pozzolana", a still used common term.

The Romans introduced the Pozzolean knowledge and the hydraulic mortar to the conquered regions. This created the need to find new mines for materials with the same characteristics. On the Greek isles, the ashes of Santorini turned out to be suited. Near modern Syria, there was the pumice. In Northern and Central Europe, the 'trass' from the Eifel-Rhine region was used.

Finally, the Romans invented a different type of hydraulic mortar based on lime and crushed ceramics. This mortar is today known as "cocciopesto" and gave the Romans the opportunity to produce hydraulic mortars throughout their empire, regardless of location..

Through a mixture of lime, pozzolans, cocciopesto and gritstone, the Romans created the so-called Roman concrete.

The final lime mortars that were used during the later periods of history, show a certain similarity with the lime mortars from the Romans. In the 18th century, the knowledge and use of the materials started to disappear, because the hydraulic components were untraceable. Only the use of crushed bricks survived, often empirically mixed with lime, and with a dubious quality.².

Lime mortars as a substitute for cement

Lime mortars have proved to have many unique properties. The microstructure of the pores of hardened lime putty is much finer than that of hardened cement mortars. In fact, this structure of the pores is so fine,that there is no place for water vapor. In addition, buildings which are build with lime mortars can absorb deformations without visible cracks or loss of consistency. The mortars are like self-healing. Furthermore, lime has an antifungal property³.

1. Source: www.architectenweb.nl - Concrete by Roel Griffioen (Dutch)

2. Source: www.arteconstructo.be - History of hydraulic lime mortars (Dutch)

3. Source: www.hanssenbiobouw.nl - Newsletter 2008 - Article: Lime, cement and buildingbiology (Dutch)