Effects of Granulated Cork with Bark on the Microstructure and Resistance to Extreme Environmental Conditions of Concrete for Non-Structural Precast Elements

The building sector is responsible for major environmental impacts. Utilising bio-based raw materials, such as bio-aggregates, in concrete production could address to this environmental challenge. While the physical and mechanical properties of various bio-based concretes have been explored, research on their microstructure and resistance to extreme conditions is limited. Cork is a light, renewable and biodegradable material. Cork industries produce a considerable number of solid wastes, among them is granulated cork with bark (GCB) that is not adequate to produce agglomerated cork. To reduce this waste volume, it is possible to use GCB as a bio-based aggregate in the production of concrete for applications in non-structural precast elements that are lighter and/or have thermal properties. The influence of GCB on the microstructure and resistance to extreme conditions of concrete for non-structural use is presented here. Concrete mixes with GCB are compared with a concrete mix made with natural aggregates (RC). Replacements of 20% and 30% of natural aggregate (2-5 mm) by GCB were considered. The microstructure shows the good integration of the GCB in the cement matrix. Freeze-thaw and wet-dry cycle tests do not affect the variation in mass and compressive strength of concrete mixes with GCB in comparison to RC mixes, although they do affect its visual appearance and microstructure somewhat. Concrete mixes with GCB present a greater variation in mass and compressive strength, 30% for RC mix and 43-49% for concrete mixes with GCB, under high temperatures. Concrete mixes with GCB did not show spontaneous combustion.