Microstructure engineering of Portland cement pastes and mortars through addition of ultrafine layer silicates

Holger Lindgreen, Mette Geiker, Hanne Krøyer, Niels Springer, Jørgen Skibsted

Publikation: Bidrag til tidsskriftArtikelForskningpeer review

60 Citationer (Scopus)

Abstrakt

Pozzolanic submicron-sized silica fume and the non-pozzolanic micron- and nano-sized layer silicates (clay minerals) kaolinite, smectite and palygorskite have been used as additives in Portland cement pastes and mortars. These layer silicates have different particle shape (needles and plates), surface charge, and size (micron and nano). The structure of the resulting cement pastes and mortars has been investigated by atomic force microscopy (AFM), helium porosimetry, nitrogen adsorption (specific surface area and porosity), low-temperature calorimetry (LTC) and thermal analysis. The main result is that the cement paste structure and porosity can be engineered by addition of selected layer silicates having specific particle shapes and surface properties (e.g., charge and specific surface area). This seems to be due to the growth of calcium-silicate-hydrates (C-S-H) on the clay particle surfaces, and the nano-structure of the C-S-H depends on type of layer silicate. The effect of layer silicate addition is most pronounced for palygorskite and smectite having the largest surface area and negative charges on the particle surfaces. The cement pastes containing palygorskite and bentonite have, in comparison to the pure cement paste and the paste containing kaolinite, a more open pore structure consisting of fine pores. Silica fume paste contains a significant amount of closed pores. As a secondary result, it is demonstrated that both the degree and duration of sample drying strongly modifies the structure of the cementitious materials under investigation.

OriginalsprogEngelsk
Sider (fra-til)686-699
Antal sider14
TidsskriftCement and Concrete Composites
Vol/bind30
Udgave nummer8
DOI
StatusUdgivet - sep. 2008

Programområde

  • Programområde 4: Mineralske råstoffer

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