Utilization of shale cuttings in production of lightweight aggregates

The development of technologies for unconventional hydrocarbon exploration requires designing procedures to manage drilling waste that are consistent with the waste management hierarchy. In view of this, the possibility to apply shale drill cuttings as a prospective additive (replacing bentonite) to fly ash used for the production of lightweight aggregates (LWAs) was investigated. Moreover, a facile, waste-free method of LWAs production with using shales was proposed. Cuttings were characterized in terms of their mineralogical and elemental composition (XRD and XRF) as well as thermophysical behavior (TG-DTA and fusibility test). The sintered product, in turn, was assessed taking into account its structure, physicochemical and mechanical properties. It was found that the composition of the shale drill cuttings meets the conditions required for the bloating (as expressed by the SiO₂/ΣFlux and Al₂O₃/SiO₂ ratios) and binding processes (Al₂O₃ content), essential for the aggregates production. In comparison to bentonite, shales provided an additional source of kaolinite, which thermal transformation to mullite is crucial for the formation of mechanically durable structure of the aggregate. Moreover, the bulk density of the sintered product was found to be less than 1200 kg/m³, and the dry particle density below 2000 kg/m³, confirming that the obtained porous material belong to lightweight aggregates with accordance to European standard (UNE-EN-13055-1). The porosity of LWA was found to be higher (even up to 50%), thus the apparent density lower, compared with the reference product containing bentonite. These properties were accompanied by the relatively high crushing resistance which was up to 4.4 N/mm². Hereby, usefulness of shale drill cuttings for LWAs production was confirmed.