The mechanical behaviour of a novel, sustainable foundation made of stone aggregates under vertical compressive loading

Timber buildings have become increasingly popular due to their excellent mechanical and thermal properties, short construction times typical of prefabricated structures, and low CO2 emissions. However, the usual foundation of timber buildings still consists of a thick reinforced concrete, cast-in-situ slab, which requires a relatively long time to construct and produces significant CO2 emissions. This study discusses the performance of an alternative, novel prefabricated shallow foundation for lightweight one- or twostorey timber buildings, i.e. the Ledrosteel Foundation (LSF). The LSF consists of a steel weldmesh gabion filled with stone aggregates and closed with a special lid that incorporates a reinforced-concrete beam and a hinge for connection to the superstructure. Compared to traditional reinforced concrete slabs, it reduces construction times due to prefabrication and CO2 emissions due to the use of more environmentally friendly materials. An extensive testing programme has been conducted to investigate the mechanical behaviour of the LSF under vertical loading for three different limestone aggregates. All the aggregates were freshly crushed with similar particle size distribution in the range 50-130 mm and little differences in particle shape, the latter described through the Shape Angular Group and Overall Regularity indices. The tests were carried out in the Laboratory for Material and Structural Testing of the University of Trento, where full-size specimens were brought to failure under unconfined vertical loading. All the specimens failed due to punching of the reinforced concrete beam, regardless of the aggregate type. However, their loads and secant stiffness at failure were found to reduce with increasing porosity. The tests also suggested a potential effect of particle size and angularity, but further tests will be carried out to increase sample statistical size and improve the understanding of the effect of aggregate particle characteristics and initial porosity on the mechanical performance of the LSF.