Granulated cork with bark characterised as environment-friendly lightweight aggregate for cement based materials

Abstract

The cork industry generates large quantities of waste, which has been studied for the application in the construction industry. However, the literature refers to it as cork waste (granulated or dust) in general, and its features have not been clearly specified. However, cork waste includes several by-products with different characteristics depending on the stage of process which they are generated in. The main goal of this study is to investigate the specific characteristics of one of those by-products that is granulated cork with bark, in order put to use as a lightweight aggregate in the construction industry. In this paper, its surface chemical properties are studied, by the first time, employing Fourier Transformed Infrared Spectroscopy and Energy Dispersive X-ray Spectroscopy and they are compared to those of cork. The chemical functional groups that are present at the granule surface, carbonyl and hydroxyl groups, are able to interact with cement components and water by important intermolecular chemical forces such as hydrogen bonds or dipole-dipole. The microstructure of grains is evaluated through image analysis, Scanning Electron Microscopy. The found cellular structure gives rise to density and absorption values similar to those of commercial lightweight aggregates and provides thermal insulating properties to this material. Then this material presents suitable properties to find a use as lightweight aggregate for concrete or mortar. The optimal replacement of aggregate by granulated cork with bark would contribute to a sustainable manufacture of cork providing an outlet for this waste.