Synergic effect of hydrated lime and guar gum stabilisation on the mechanical, thermal and hygroscopic behaviour of a Ligurian earth material

This paper investigates the synergic effect of both hydrated lime and guar gum stabilisation on the mechanical, thermal and hygroscopic properties of a compressed earth material for building applications. The stiffness, strength and compression energy at failure of both unstabilised and stabilised earth samples were measured at different curing times by means of compression tests. The moisture-dependent thermal conductivity was instead determined via the hot disk technique at a constant temperature of 25 °C and at the three different relative humidity levels of 0%, 50% and 95%. The specific heat capacity was measured by means of calorimetry tests at the three temperature levels of 32-34 °C, 34-36 °C and 36-38 °C. The moisture adsorption-desorption curves were measured by performing a cyclic variation of relative humidity between 0% and 95% at a constant temperature of 25 °C via the dynamic vapour sorption (DVS) technique. Results from the experimental campaign show that the proposed stabilisation methods increase both the peak compressive strength and compression energy at failure while the addition of the biopolymer guar gum induces a progressive reduction of stiffness. The thermal properties of the earth are only marginally affected by the addition of hydrated lime and guar gum, with stabilised samples exhibiting similar levels of thermal conductivity and specific heat capacity to those of the unstabilised ones. Finally, the biopolymer stabilised samples exhibited a similar hygroscopic behaviour to that of unstabilised ones, whereas the addition of hydrated lime deteriorates the moisture adsorption capacity of the material.