REACTivity under confinement: in-situ mineral growth within nano- and microscale volumes.

In nature, crystals tend to grow inside pores. When water flows through porous media such as rocks or building materials, minerals can dissolve, and new more stable crystals may grow. The consequences of mineral growth inside pores affect a vast range of natural and anthropogenic environments. These for example include: built cultural heritage and modern infrastructure where new minerals crystallize and cause damage; geological formations where the growth of new minerals may lead to fracturing and failure; underground reservoirs in porous rocks where injection of CO2 changes the existing mineral types with unknown consequences for the reservoir’s permeability; or ordinary Portland cement where mineral dissolution and growth is the source of its extremely high cohesion. Depending on the setting, crystallization may be disadvantageous or desired. In both cases, there is a pressing need to better understand and control the mineral growth in pores. REACT project team aims to better understand, predict, and control mineral reactivity and growth under confinement. We will especially focus on the destructive or cohesive impact of mineral growth in pores on the surroundings. Our unique experimental setup relies on the surface forces apparatus (SFA) technique. SFA can provide measurements of adhesive or repulsive surface forces during mineral growth in a nanometer- to micrometer-sized confined geometry. Our experimental work will focus on locations of new growing minerals as a function of pore shape. We will find links between surface forces during the damaging or cohesive growth of minerals. Our results will provide new knowledge on crystal growth under confinement, broadly relevant to geology and material science.

Real-life mineral nucleation and growth is seldom a homogenous, bulk solution process. Minerals frequently grow under spatial confinement in pores. When fluids percolate through porous media, minerals can dissolve, and new more thermodynamically stable phases may precipitate. The consequences of mineral growth under confinement affect a vast range of natural and anthropogenic environments. These include: built cultural heritage and modern infrastructure where new minerals crystallize and cause disintegration; geological formations where mineral replacement may lead to fracturing and cohesive failure; subsurface geological reservoirs where anthropogenic injection of CO2 changes the existing mineral assemblages with unknown consequences for the reservoir’s permeability; and Portland cement where mineral dissolution-reprecipitation govern its robust cohesive properties. Depending on the setting, the confined mineral growth may be perceived as disadvantageous or desired. In both cases, there is a pressing need to better understand and control the mineral growth in pores. In the interdisciplinary REACT project, we will endeavor to better understand, predict, and control mineral reactivity under confinement. We will especially focus on the destructive or cohesive impact of confined mineral growth on the host matrix, i.e. confining material, by measuring in-situ forces acting between reactive surfaces. Our unique experimental approach relies on the surface forces apparatus (SFA) with real-time force sensing. SFA is the only technique, which can provide measurements of nano- to microscale, distance-resolved surface forces in a confined geometry. After upgrading the SFA to enable real-time force sensing (WP1), we will study confined mineral replacement to unravel the mechanisms that control the spatial location of new growing minerals (WP2). Further, we will find links between surface forces acting during cohesive (WP3) and damaging (WP4) growth of minerals in pores.