The influence of constituents on the properties of the bio-aggregate composite hemp-lime

Composites made of bio-aggregate particles and lime based binder can be used as a low embodied energy alternative to traditional walling systems and can provide several performance advantages. As the ratio and nature of constituents used in bio-aggregate composites will have bearing on the properties, it is necessary for these to be capable of being optimised to meet specific design requirements. In addition, as these materials are known to be anisotropic, it is required that any impact of constituents is assessed with respect to orientation. In this paper, the influence of the binder to aggregate ratio and aggregate particle size distribution on the compressive strength, flexural strength and thermal conductivity of hemp-lime composites in two directions of loading have been assessed. A newly developed image analysis method was also employed to study the topology of the internal structure. The results show that the material is anisotropic in both behaviour and internal structure and that both binder/aggregate ratio and aggregate particle size distribution affect composite properties. In the case of binder to aggregate ratio, the impact is shown to be directionally dependent and indicative of differing governing factors controlling the failure mode in opposing loading directions.