Impacts of Stone Waste Replacement for Portland Cement on the Mechanical Properties of Cement Pastes and Future Fields of Application

The natural stone industry in Italy is one of the largest in the world in terms of production and exports. As one of the country’s most important sectors, stone quarrying and processing are influenced by the increase in the number of construction projects due to the heavy use of natural stone as a permanent building material. However, the increased demand for natural stone increases waste, which is produced at multiple stages from quarrying to cutting and processing. The waste generated in all processes can reach up to 70% of the total volume, of which 80% is solid waste, that is relatively easy to reuse, while the remaining 20% of waste is in a semi-liquid state that is typically more difficult to recycle and often ends up in nature. The literature on the use of stone semi-liquid waste or stone slurry is extensive. This paper provides a review of the state of the art on the use of stone slurry in cement pastes and addresses its effects on the mechanical properties of fresh and cured pastes. Mechanical properties are investigated through a series of tests, which are performed to determine the flow, workability, flexural strength, and compressive strength of several samples at a constant water to binder ratio. The samples are prepared with increasing levels of replacement of cement with dried stone slurry using a CEM II cement. The results are compared to the literature to aid in the decision of choosing an appropriate mix for non-structural and non-load-bearing elements. Based on the characterized properties, this paper outlines a set of possible fields of application.