Mechanistic insights into the early hydration kinetics of oil-well cement controlled by calcined shale-gas drill cuttings: a multi-scale characterization and kinetic-model approach

This study investigates how calcined shale-gas drill cuttings (CDC) regulate early oil-well cement hydration. CDC is pozzolanic, yet its dissolution releases Al3+ ions that adsorb onto C3S surfaces, inhibiting dissolution and prolonging induction by 23.5%, 41.2%, and 111.8% for 30%, 50%, and 70% CDC pastes, respectively. Rising pH subsequently weakens this inhibition, accelerating post-induction hydration. Krstulović-Dabić modeling shows CDC reduces nucleation-and-growth (KNG), interfacial reaction (KI), and diffusion (KD) rate constants while elevating reaction order (n); for 70% CDC, KNG, KI, and KD fell by 14.17%, 27.03%, and 14.43%, respectively, while n rose by 6.96%. Elevated pore-solution Al and Si accelerate C3A-gypsum reactions, generating extra ettringite that limits C-S-H nucleation. Despite impairing fluidity and early strength, 10% CDC achieves 30.91 MPa at 28 d, matching pure cement. Denser ettringite and foil-like C-(A)-S-H gels are observed microstructurally. These findings offers a novel pathway for drill cuttings resource utilization.