The effect of recycled tire rubber and expanded shale aggregate on the thermal resistance and the compressive strength of rammed earth walls

Rammed earth (RE) is one of the most environmentally friendly green building material. The low thermal resistance of rammed earth walls is one of the drawbacks of this material. In this study, nine rammed earth mixtures were tested to investigate the effectiveness of recycled tire rubber and expanded shale aggregate on the thermal resistance of rammed earth walls. A control RE sample was built without additives to form a basis of comparison for rammed earth mixtures with the additives. Powder rubber (30 mesh) and coarse rubber (20 mesh- 3/16") were each added in three percentages; 2.5%, 5%, and 7.5% of the total mixture weight to create six RE samples. Coarse expanded shale (1/4"-3/16") and crushed expanded shale (0-1/8") were added in a percentage of 7.5% of the total mixture weight to create two RE samples. The effect of those additives on the compressive strength of RE mixtures was also investigated in this study. The results showed that adding 2.5%, 5% and 7.5% of powder rubber to the RE mixture deteriorate its thermal resistance and compressive strength. Adding 2.5%, and 5% of coarse rubber improved its thermal resistance and reduced its compressive strength. Increasing the percentage of the coarse rubber to 7.5% reduced its thermal resistance and its compressive strength. On the other hand, adding 7.5% of fine and coarse expanded shale aggregate improved its thermal resistance and caused a slight reduction in compressive strength.