Influence of sawdust and soil type on the high temperature behavior of raw earth bricks

Abstract

The current study looks into the high temperature behavior raw earth bricks made with varying amounts of sawdust additives. In addition to the various sawdust amounts, two different soil types were used: “Limon des Plateaux” soil from Beauvais city and clay from Barremian. Before being tested at high temperatures, those bricks were referred to an initial characterization to assess their physical and mechanical properties. At room temperature, the compressive strength decreased with increasing the sawdust mass fraction. The “Limon des Plateaux” soil presented a better resistance than the Barremian clay. After that, the blocks were exposed to high temperatures at a slow heating rate of 1 °C/min inside a furnace programmed to attain target temperatures of 150 °C, 300 °C, 450 °C and 600 °C. The residual physical and mechanical properties of the specimens were then determined. High temperature measurements were also assessed during the heating inside the samples by means of thermocouples that were embedded in their center. The obtained results showed that the compressive strength of the earthen bricks without sawdust increased as the temperature was raised. However, the compressive strength of the bricks with sawdust decreased between 150 °C and 300 °C due to the pyrolysis of the sawdust and then increased again between 300 °C and 450 °C as a result of clay dehydroxylation. The “Limon des Plateaux” soil and Barremian clay with sawdust demonstrated a similar evolution with respect to temperature. The temperature measurements in the center of the samples revealed the influence of the sawdust additives on the temperature distribution inside the sample. The amount of sawdust has an influence on the evolution of the residual properties with temperature. The higher the volume fraction of sawdust, the lower the compressive strength increased with temperature between 20 and 600 °C.