The major drawbacks of earth such as low water stability and moderate strength have led mankind to stabilize the earth. It has been developed as a vernacular technique in different civilizations. Since then, the focus was mainly on gypsum, lime, or pozzolan stabilization. Recently, cement has become one of the commonly used additives in earth stabilization, which consequently reduce the environmental advantage of earth.
This paper deals with a reverse engineering approach for low environmental impact earth stabilization technique, aiming the replacement of cement in earth stabilization.
Various earth-mixtures were done to investigate the performance of this technique. Water contact behaviour and compressive strength of the stabilized earth specimens was determined. Moreover, the characterization of the stabilization effect has been performed through X-ray powder diffraction patterns (XRD) and clearly identify the production of ettringite using very low CO2 intensive raw materials. Furthermore, the carbon footprint of the stabilized earth-mix has been determined with the help of LCA (life cycle assessment) calculation. The laboratory analyses on this mix-design have proven a high water-resistance and the results show a remarkable increase in compressive strength. Finally, these results open a new avenue for earth stabilization and secure the implementation of this material in the conventional construction industry.
The fast precipitation of ettringite in conventional Calcium Sulfo Aluminate (CSA) cement causes rapid stiffening of the cement paste and is directly associated with short setting times and self-desiccation. To extend the time during which those types of cement remain workable, retarding admixtures can be used. However, retarders may affect the amounts and types of hydration products formed and as a consequence the ability of hydrated cement to chemically bind water. This work investigates the influence of two natural-based admixtures on the self-desiccation ability of a vernacular CSA ternary binder used as earth stabilization. Vicat measurements were used to study the efficiency of citric acid and sucrose as retarding admixtures on the setting time of stabilized earth. A quantitative study of the self-desiccation ability of the binder was performed on dried binder pastes using thermogravimetric analysis (TGA). Results show that both admixtures have a significant impact on the setting time of the binder. Furthermore, TGA showed that the self-desiccation ability of this vernacular CSA binder is significantly reduced when citric acid at high dosages is used, both at early hydration and after 14 days. On the contrary, the use of sucrose does not affect the water chemically bound at an early age but can maximize bound water after 14 days of hydration.
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