Valorisation of stranded Laminaria digitata seaweed as an insulating earth material

Abstract

In Normandy, the marine macroalgae become a large problem when the retreat of the tide leaves large quantities of stranded seaweed on coast. These stranded seaweeds can be toxic during their degradation in addition to creating odor problems. Consequently, their elimination has become a major problem and their recovery an emergency. In this work, we proposed to use the stranded seaweed in the building construction at a large scale. We investigated in particular the performance of insulated walls based on lightened earth incorporating reed and stranded Laminaria digitata seaweed at different substitution level. The compressive strength and the hygrothermal properties of the earth insulated walls specimens were carried out. Our results show that the incorporation of seaweed in lightened earth improves both its heat storage capacity and its level of insulation without compromising its compressive strength. The most efficient seaweed content for improving the thermal insulation of the material seems to be 20%. Indeed, the addition of 20% of Laminaria digitata decreased the thermal conductivity by 34% at 20 °C in comparison with standard cob. For this mixture, the specific heat capacity value is around 800 J.kg−1.K−1 at 20 °C, which are very high compared to that of the only earth-fiber specimen (400 J.kg−1.K−1). These increases in mechanical and hygrothermal performance of insulating cob material incorporating seaweed will lead to a reduction of the cob walls thickness and therefore to the development of sustainable energy efficient building materials with a low environmental impact.