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@PHDTHESIS{Muzenda:1028014,
      author       = {Muzenda, Tafadzwa Ronald},
      othercontributors = {Matschei, Thomas and Thienel, Karl-Christian and Snellings,
                          Ruben},
      title        = {{E}arly reactivity of activated clays - impact on binder
                      design and hydration},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2026-01389},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2026},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, Rheinisch-Westfälische Technische
                      Hochschule Aachen, 2026},
      abstract     = {The readily available approach to cut down carbon footprint
                      from the cement and concrete industry is the use of
                      supplementary cementitious materials (SCMs). Clays and
                      limestone are available globally and this has led to the
                      development of calcined clay limestone cements (CCLC, also
                      widely referred to as LC3). When the clays are activated
                      using methods other than calcination (thermal activation),
                      we refer to the binder as activated clay limestone cement
                      (ACLC). This thesis focuses on kaolinitic clays, and
                      smectitic clays. The impact of the physico-chemical
                      properties of natural calcined clays (CCs) on rheology and
                      early reactivity is the entry point of this thesis. It was
                      shown that metakaolin content was not the main factor
                      leading to differences in rheological properties and early
                      reactivity. In addition, high early reactivity is also
                      observed for some low specific surface area (SSA) CCs,
                      showing the influence of factors other than SSA. High
                      structural disorder of kaolinite was shown to be related to
                      faster early reactivity. In a follow up study, the impact of
                      physico-chemical properties and metakaolin content on the
                      hydration of ACLC was followed up to 2 years. In order to
                      better characterize the early reactivity of activated clays,
                      a sulfate-limited model system (SLiM) test was developed.
                      SLiM consists of an excess of CC and portlandite, and
                      limited gypsum. It was demonstrated that the SLiM test can
                      be used to probe physico-chemical properties, including the
                      standard enthalpy of formation of metakaolin, and can
                      predict mechanical performance and hydration of ACLC up to 3
                      days. Additionally, it lays the foundation for automated
                      optimal sulfate determination, and it complements the R3
                      test in the assessment of activated clays or, in general,
                      alumina-rich SCMs. Mechanical activation, and the
                      combination of mechanical and thermal activation were
                      explored. Results highlighted different mechanisms by which
                      activated clays contribute to the hydration and mechanical
                      performance of ACLC, and the influence of activation
                      protocols on the properties of activated clays. Early
                      reactivity was shown to be dependent on physical properties
                      and structural defects, as highlighted by differences in
                      portlandite consumption and hemicarboaluminate
                      precipitation, while late-reactivity mainly depended on
                      activation degree of clay minerals. Mechanical and
                      mechano-thermal activation, as well as grinding aids, were
                      shown to improve the early strength of smectite-based ACLC
                      by 15 - 59 $\%.$ This was partly because, unlike calcination
                      at 900 °C, mechanical and mechano-thermal activation does
                      not result in a significant loss in SSA, and mechanical
                      activation increases the initial dissolution of smectitic
                      clays as shown using the SLiM test. Insights presented in
                      this thesis improve understanding of the effect of
                      physico-chemical properties of activated natural clays on
                      workability and, early and late strength development. An
                      early reactivity test (the SLiM test) which has widespread
                      applications for alumina-rich SCMs was developed. In
                      addition, the potential of mechanical activation and
                      combination of mechanical and thermal activation as
                      alternatives to thermal activation was highlighted.},
      cin          = {311110},
      ddc          = {624},
      cid          = {$I:(DE-82)311110_20160603$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2026-01389},
      url          = {https://publications.rwth-aachen.de/record/1028014},
}