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

Abstract

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 33.11MPa of the control specimen to 29.33MPa and 21.48MPa, 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 11.33MPa 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.