Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Strength Evolution of Hydrating Cement Pastes: the Counteracting Effects of Capillary Porosity and Unhydrated Clinker Reinforcements
In the 1930s, Freyssinet presented a model describing that the strength of cement paste decreases with increasing capillary porosity. He proposed that uniaxial compressive strength of cement pastes is proportional to a volume quotient which is nowadays referred to as "gel-space ratio". In the 1970s, Fagerlund found out that capillary porosity is not the only governing factor because he observed that the final strength of substoichiometric cement pastes increases with decreasing initial water-to-cement mass ratio. However, due to limited microstructural insight, he could only propose an empirical description of the observed effect. We here provide more insight into how microstructural properties of cement paste influence its macroscopic compressive strength, based on the experimentally confirmed elasto-brittle micromechanics model of Pichler and Hellmich [CemConRes, 41(5) 467-476, 2011]. Gel-space ratio is shown to be equal to the solid volume fraction of a "hydrate foam" which is defined at the scale of a few microns and which exhibits a (quasi-)polycrystalline morphology of needle-shaped and isotropically oriented hydration products with capillary porosity filling the space in between. The model confirms that the material strength of cement pastes is not only determined by the capillary porosity, but unhydrated clinker grains (which are embedded, as inclusions, in the hydrate foam) act as reinforcements which increase the macroscopic strength; and that this is practically significant for substoichiometric mixes at large maturities, see Pichler et al. [CemConRes, 45(1), 55-68, 2013].
Strength Evolution of Hydrating Cement Pastes: the Counteracting Effects of Capillary Porosity and Unhydrated Clinker Reinforcements
In the 1930s, Freyssinet presented a model describing that the strength of cement paste decreases with increasing capillary porosity. He proposed that uniaxial compressive strength of cement pastes is proportional to a volume quotient which is nowadays referred to as "gel-space ratio". In the 1970s, Fagerlund found out that capillary porosity is not the only governing factor because he observed that the final strength of substoichiometric cement pastes increases with decreasing initial water-to-cement mass ratio. However, due to limited microstructural insight, he could only propose an empirical description of the observed effect. We here provide more insight into how microstructural properties of cement paste influence its macroscopic compressive strength, based on the experimentally confirmed elasto-brittle micromechanics model of Pichler and Hellmich [CemConRes, 41(5) 467-476, 2011]. Gel-space ratio is shown to be equal to the solid volume fraction of a "hydrate foam" which is defined at the scale of a few microns and which exhibits a (quasi-)polycrystalline morphology of needle-shaped and isotropically oriented hydration products with capillary porosity filling the space in between. The model confirms that the material strength of cement pastes is not only determined by the capillary porosity, but unhydrated clinker grains (which are embedded, as inclusions, in the hydrate foam) act as reinforcements which increase the macroscopic strength; and that this is practically significant for substoichiometric mixes at large maturities, see Pichler et al. [CemConRes, 45(1), 55-68, 2013].
Strength Evolution of Hydrating Cement Pastes: the Counteracting Effects of Capillary Porosity and Unhydrated Clinker Reinforcements
Pichler, Bernhard (Autor:in) / Hellmich, Christian (Autor:in) / Eberhardsteiner, Josef (Autor:in) / Wasserbauer, Jaromír (Autor:in) / Termkhajornkit, Pipat (Autor:in) / Barbarulo, Rémi (Autor:in) / Chanvillard, Gilles (Autor:in)
Fifth Biot Conference on Poromechanics ; 2013 ; Vienna, Austria
Poromechanics V ; 1837-1846
18.06.2013
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
Wave propagation , Poroelasticity , Cement , Mechanics , Simulation , Porous media , Porosity , Hydration
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