Hot mix method for the manufacture of sand-polymer bricks

Abstract

This manuscript presents a method to produce sand-polymer bricks motivated by the need to reuse plastic waste and to reduce the embodied energy and carbon footprint associated with manufacturing. The method is designed to be simple: it involves a custom-built apparatus that simultaneously mixes and heats dry sand and recycled polypropylene granules, until the latter melt. The hot mixture is then compressed in a mold until the polymer rehardens, thereby producing a bonded brick upon extrusion. Bricks with 10% and 20% polymer content (i.e., by mass, PCg), were prepared with either a fine sand or a coarse sand. The voids of the PCg = 10% bricks were approximately halfway filled with hardened polymer, whereas the voids of the PCg = 20% bricks were nearly entirely filled. Bricks with PCg = 20% were found to be potential candidates for replacement of fired clay bricks, as these exhibited infiltration levels well below specification thresholds for fired clay bricks and strengths comparable to those reported for fired clay bricks. Furthermore, the embodied energy associated with sand-polymer bricks was calculated to be around a third of that required for fired clay bricks. In addition, the manufacture of sand-polymer bricks requires minutes, whereas that of fired clay bricks requires hours. The results gathered suggest that bricks produced by the proposed method have potential for replacement of fired clay bricks in applications wherein replacement is favorable.