title: Aluminum-induced dreierketten chain cross-links increase the mechanical properties of nanocrystalline calcium aluminosilicate hydrate.
abstract: The incorporation of Al and increased curing temperature promotes the crystallization and cross-linking of calcium (alumino)silicate hydrate (C-(A-)S-H), which is the primary binding phase in most contemporary concrete materials. However, the influence of Al-induced structural changes on the mechanical properties at atomistic scale is not well understood. Herein, synchrotron radiation-based high-pressure X-ray diffraction is used to quantify the influence of dreierketten chain cross-linking on the anisotropic mechanical behavior of C-(A-)S-H. We show that the ab-planar stiffness is independent of dreierketten chain defects, e.g. vacancies in bridging tetrahedra sites and Al for Si substitution. The c-axis of non-cross-linked C-(A-)S-H is more deformable due to the softer interlayer opening but stiffens with decreased spacing and/or increased zeolitic water and Ca2+of the interlayer. Dreierketten chain cross-links act as 'columns' to resist compression, thus increasing the bulk modulus of C-(A-)S-H. We provide the first experimental evidence on the influence of the Al-induced atomistic configurational change on the mechanical properties of C-(A-)S-H. Our work advances the fundamental knowledge of C-(A-)S-H on the lowest level of its hierarchical structure, and thus can impact the way that innovative C-(A-)S-H-based cementitious materials are developed using a 'bottom-up' approach.
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States.
authors.forename: Guoqing
authors.initials: G
authors.lastname: Geng
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States.|School of Forestry &Environmental Studies, Yale University, New Haven, Connecticut 06511, United States.
authors.forename: Rupert J
authors.initials: RJ
authors.lastname: Myers
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States.
authors.forename: Jiaqi
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Chemical &Biomolecular Engineering, University of California, Berkeley, California 94720, United States.
authors.forename: Roya
authors.initials: R
authors.lastname: Maboudian
authors.affiliation: Department of Chemical &Biomolecular Engineering, University of California, Berkeley, California 94720, United States.
authors.forename: Carlo
authors.initials: C
authors.lastname: Carraro
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Shapiro
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States.|Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Paulo J M
authors.initials: PJ
authors.lastname: Monteiro