Fuzzy-based quality classification model for natural building stone blocks

Natural building stones (NBS) have been used since ancient times as decoration and as construction material. The first form of NBS products is a raw stone block. International trading of NBS blocks is very important, because almost half of all commercial activity in the NBS industry involves trading of quarried raw NBS blocks. Currently, however, there is no internationally accepted quality classification system for NBS block trading in the market. The commonly applied classification depends on stone dimensions, colour, textures, and poor-quality properties such as fissures–fractures and fossils. The definitions and limitations of this classification are not exactly clear, because every NBS block has different properties. Therefore, in this study, a fuzzy model was developed to classify the qualities of NBS blocks according to their physical and colour properties. The study shows that fuzzy set theory could effectively overcome current classification uncertainties.