Strength Characteristics of Dry-Pressed Thermally Bonded Clay–Polymer Composites

Abstract

This paper describes the development and strength characteristics of clay–polymer composites to promote their potential use as fired clay brick substitutes. Each specimen was manufactured by dry pressing a mixture of kaolinite clay and polyester particles and then heating the extruded green body. Heat melts the polyester particles, which creates a bonded composite, herein termed a brick, upon cooling. The focus was on composites in which the clay species predominates. The approach benefits from two novelties: added water is unnecessary, and heating is imposed on moldless bodies. The results indicate that green bodies preserve their shape after extrusion regardless of volumetric polymer content (PCv). Similarly, bricks preserve their shape and largely their volume after heating. The p-wave modulus was found to be significantly higher for bricks than for green bodies, offering evidence that the fabric of the material is stiffened via polymer melting, coalescing, and cooling, despite preservation of specimen shape and volume. The tensile strength of bricks was found to increase with increasing PCv and to remain unaffected by water infiltration. In particular, the brick with PCv=40% (with green body pressed to 22.5 MPa) was found to have a lower water absorbability, a measurably higher tensile strength, and a lower embodied energy associated with manufacturing than a standard fired clay brick, making the former a potential candidate for substitution for the latter in permissible applications.