No abstract

The transition to a low-carbon future involves every component of our productive life — from the energy we use, to the buildings we construct, to the materials we use in our daily lives. Realistically, the shift onto a low-carbon path cannot happen instantly but requires adopting short- and long-term solutions while assessing whether the solutions work in the physical world in which we live. In the short term, incremental technological improvements, such as transitioning to energy sources like natural gas, have the potential to yield immediate benefit to air quality and pollution. In the mid and long term, however, more far-reaching decarbonization technologies must be pursued to achieve game-changing outcomes. In the geosciences realm, leading technologies span from cleaner energy solutions to exploring alternative earth-inspired materials and processes. These include CO2 storage in geologic disposal sites along with its reuse for material manufacturing, the development of enhanced geothermal systems expanding the use of geothermal energy, and adapting subsurface processes to engineer greener processes and materials through geomimicry. In this landscape, experimentation and rock physics are at the crux of understanding rock-fluid processes and are the premise and foundation of decarbonizing our future. All of these applications require experimentation for wider public acceptance to avoid hasty solutions that are counterproductive. The cross-disciplinary nature of each endeavor is pivotal in assessing how processes induced by fluids, their chemistry, and thermal capacity affect the physical and mechanical properties of treated environments. This paper provides an account of the role that rock physics will play in leveraging knowledge across the nanosciences to underpin our path to a decarbonized future through chemical and thermal stimulation practices, solid-CO2 reactions, and engineering processes that manipulate geology to produce materials with functional properties.

Studying the mechanisms that control the rheology of rocks and geomaterials is crucial as much for predicting geological processes as for functionalizing geomaterials. That requires the understanding of how structural arrangements at the micro and nano scale control the physical and mechanical properties at the macroscopic scale. This is an area of rock physics still in its infancy. In this paper, we focus the attention on the formation of cementitious phases made of micro- and nano-scale fibrous structures, and the controls of the arrangement of these phases on mechanical properties. We use hydrothermal synthesis, and the properties of hydrothermal water, to promote the growth of fibrous mineral phases having nano-size diameter and length of a few microns, creating disordered and entangled mats of fibrous bundles as those found in natural samples. We draw inferences from structural microscopy to inform a statistical model that establishes an interdependence between structural parameters of fibrous structures and bulk mechanical response. Structural parameters include number and length of fibers, spatial orientation, and fraction of fibrous threads bearing the load. Mechanical properties include strength and mode of failure. Results show that as the fibrous microstructure evolves from ordered and aligned to disordered and entangled, the mechanical response of the fibrous composite transitions from a brittle to ductile behavior. Furthermore, the disordered and entangled microstructure exhibits lower strength at failure though strength increases as the number of fibers within the microstructure increases. Finally, the longer the entangled fiber, the larger the strain that the matrix can accommodate. The value of this study lies in further understanding fault healing through hydrothermal fluids and how the physical properties of fibrous microstructures resulting from it control brittle-ductile transitions, and possibly, slow slip events along subduction zones.