Utilizing shale gas drilling cuttings as admixture in cement mortars: a case study in Fuling, Chongqing, China

Huge amount of water-based drilling cuttings (WDC) is generated during the drilling and exploitation of shale gas. In this study, WDC powder was used as a replacement of cement at different mass fraction (0, 10%, 30%, and 50%) to prepare cement mortars. The mechanical properties, water absorption, and heavy metals leaching of the mortars were then investigated along with the corresponding microstructures. The results showed that a higher porosity was formed within the WDC-blended mortars. For instance, the porosity of the control specimen was 16.7%, while the porosity increased to 20.6%, 21.4%, and 25.0% for the mortars blended with 10%, 30%, and 50% WDC, respectively. Therefore, the mechanical properties of the mortars decreased and their water absorption increased with the increase of WDC replacement ratio. For example, the compressive strength of the mortars blended with 10% and 30% WDC decreased from 33.11 MPa of the control specimen to 29.33 MPa and 21.48 MPa, respectively. Nevertheless, the blended mortars still satisfied the M20 strength grade according to the Chinese standard (JGJ/T 98-2010). The compressive strength of the mortar blended with 50% WDC was 11.33 MPa and then satisfied the M10 strength grade. The leaching test indicated that the water quality of leachates from the mortars blended with lower than 30% WDC remained as Grade I according to the Chinese standard (GB 3838-2002); the water quality of leachate from the mortar blended with 50% WDC was classified as Grade III, which, however, would not cause a safety issue to the environment.