TY - JOUR

T1 - Multistep Crystallization Pathways in the Ambient-Temperature Synthesis of a New Alkali-Activated Binder

AU - Maslyk, Marcel

AU - Gäb, Tobias

AU - Matveeva, Galina

AU - Opitz, Phil

AU - Mondeshki, Mihail

AU - Krysiak, Yaşar

AU - Kolb, Ute

AU - Tremel, Wolfgang

N1 - Funding Information: The authors thank Stefanie Berinskat and Frank Ludwig for X‐ray diffraction measurements and Prof. Angela Möller for access to the STOE powder diffractometer and access to the thermogravimetric analyzer. The facilities of the EM Center in Mainz (EZMZ) were partially funded by the Center for INnovative and Emerging Materials (CINEMA). The authors are grateful for technical support of the 11‐BM beamline staff. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE‐AC02‐06CH11357.

PY - 2022/2/8

Y1 - 2022/2/8

N2 - Concrete is the most prevalent manufactured material that has shaped the built environment, but the high-temperature production of cement, the main component of concrete, has a massive carbon footprint. It is shown that CO2 emissions during clinker production of cement can be circumvented by a metathesis reaction at room temperature in ball-mills, where the cement clinker is replaced by non-calcined limestone and alkali-activated binders/geopolymers. An amorphous intermediate (aNaSiCC) containing a random mixture of the ionic constituents in “molecular” dispersion is formed by mechanochemical activation of CaCO3 and Na2SiO3. This allows molecular transport during crystallization and low activated reactions, as precipitation of solids from liquids (nucleation limited and kinetically controlled) and solid-state transformations (diffusion-limited and thermodynamically controlled) have equal weight. Several steps of the hydration reaction could be resolved. Activating the amorphous aNaSiCC precursor with NaOH leads to a C-S-H-like phase with a C/S ratio of ≈1 containing some sodium. The carbonate components pass through a multistep crystallization from aNaSiCC via pirssonite and gaylussite to monohydrocalcite. The findings help unravel the interplay between thermodynamics and kinetics in complex reactions of alkali-activated binders and for CaCO3 crystallization in industrial and geochemical settings, where dissolved silicate is always involved.

AB - Concrete is the most prevalent manufactured material that has shaped the built environment, but the high-temperature production of cement, the main component of concrete, has a massive carbon footprint. It is shown that CO2 emissions during clinker production of cement can be circumvented by a metathesis reaction at room temperature in ball-mills, where the cement clinker is replaced by non-calcined limestone and alkali-activated binders/geopolymers. An amorphous intermediate (aNaSiCC) containing a random mixture of the ionic constituents in “molecular” dispersion is formed by mechanochemical activation of CaCO3 and Na2SiO3. This allows molecular transport during crystallization and low activated reactions, as precipitation of solids from liquids (nucleation limited and kinetically controlled) and solid-state transformations (diffusion-limited and thermodynamically controlled) have equal weight. Several steps of the hydration reaction could be resolved. Activating the amorphous aNaSiCC precursor with NaOH leads to a C-S-H-like phase with a C/S ratio of ≈1 containing some sodium. The carbonate components pass through a multistep crystallization from aNaSiCC via pirssonite and gaylussite to monohydrocalcite. The findings help unravel the interplay between thermodynamics and kinetics in complex reactions of alkali-activated binders and for CaCO3 crystallization in industrial and geochemical settings, where dissolved silicate is always involved.

KW - calcium carbonate

KW - calcium silicate hydrate

KW - crystallization

KW - sodium silicate

KW - solid state reaction

UR - http://www.scopus.com/inward/record.url?scp=85118309303&partnerID=8YFLogxK

U2 - 10.1002/adfm.202108126

DO - 10.1002/adfm.202108126

M3 - Article

AN - SCOPUS:85118309303

VL - 32

JO - Advanced functional materials

JF - Advanced functional materials

SN - 1616-301X

IS - 7

M1 - 2108126

ER -