Assessing the Recyclability of Raw Stabilised Compressed Earth Blocks

The mix-design of innovative earthen materials must consider their recyclability. Stabilisation is expected to limit the recyclability of earthen materials and this study assesses the recyclability potential of compressed earth blocks stabilised with 5% CEM IIIA or NHL 3,5. Raw and stabilised compressed earth blocks are produced using a modified Proctor procedure and compressive strength tests were carried after a drying stage. Following the mechanical tests, the specimens were crushed to simulate recycling by repeating a cycle of block compaction and compressive strength measurement. The mechanical characteristics of compressed blocks were not affected by the recycling stage as the mechanical strengths of the material remain constant. However, a decrease in density is observed for the stabilised sample. The optimum density after recycling decreased by 50 kg/m3 and 80 kg/m3 for formulations stabilised with 5% NHL 3,5 and CEM III respectively while the Methylene Blue Value (MBV) is reduced from 0.71 (before recycling) to 0.31 and 0.41 (after recycling). The absence of a compressive strength reduction may therefore be due to changes in the interaction between the clay/hydraulic binder and cementitious products in the first life of the material.