Potential organic binders to stabilize earth construction materials

Abstract

The use of earth as construction material for modern buildings is a topical issue regarding the significant CO2 emission of the construction sector. Indeed, this millenary material can be used for environmental friendly buildings thanks to its hygrothermal properties, its wide spread availability and its low CO2 emission. However, earth materials still have to meet satisfactory mechanical strengths and water erosion resistance to satisfy the current construction standards. Therefore, most industrial applications and scientific studies used cement or lime to stabilize earth. But the high CO2 footprint due to the high amount of the mineral binders added to these materials inhibits their sustainability. An overview of the vernacular construction techniques and the existence of ancient earth buildings revealed the use of organic binders as earth stabilizers. The organic binders are natural polymers extracted from plants or animals and mixed with earth and water generally for improving its water resistance. This study aims to identify the stabilizing potential of some of those organic polymers. Four organic polymers have been chosen for the study: polysaccharides (wheat starch, alginic acid), and proteins (casein, egg white albumin). Specimens were prepared with two types of soils and various amounts of each organic binder. Specimens were then tested according to their mechanical strength and their resistance to water. Simple tests highlighted very promising organic binders especially the proteins while for the others, it was observed that the efficiency depended on several parameters (the mixture procedure, the type of the soil and the chemical pre-activation).