Abstract
Adding polymers to cementitious materials improves their workability and impermeability, but also increases their creep activity. In the present paper, the creep behavior of polymer-modified cement pastes is analyzed based on macroscopic creep tests and a multiscale model. The continuum micromechanics model allows for “downscaling” the results of macroscopic hourly-repeated ultra-short creep experiments to the viscoelastic behavior of micron-sized hydration products and polymer particles. This way, the increased creep activity of polymer-modified cement pastes is traced back to an isochoric power-law-type creep behavior of the polymers. The shear creep modulus of the polymers is found (i) to be two orders of magnitude smaller than that of the hydrates and (ii) to increase considerably with increasing material age. The latter result suggests that the creep activity of the polymers decreases with the self-desiccation-related decrease of the relative humidity inside the air-filled pores of cement paste. Furthermore, its decrease is most likely related to the penetration of cementitious hydrates into compliant polymer agglomerates.
Highlights
Polymer-modified mortars and concretes (PCC) have gained wide attention in the fields of repair, restoration and construction [1,2,3]
The present paper aims at understanding and quantifying the micromechanical origin of the more pronounced creep activity of polymer-modified cement pastes
The identified polymer creep properties allow for a quite reliable reproduction of the experimentally-determined viscous strains; see Figure 4. This demonstrates that the experimentally-observed significantly larger creep activity of the polymer-modified cement pastes, relative to the unmodified reference paste, can be traced back to the creep behavior of the micrometer-sized polymer particles, despite their relatively small volume fraction
Summary
Polymer-modified mortars and concretes (PCC) have gained wide attention in the fields of repair, restoration and construction [1,2,3]. Regularly-repeated ultra-short creep tests provide insight into the hydration-driven evolution of the elastic stiffness and the non-aging creep properties of cementitious materials. Multiscale models, developed in the framework of continuum micromechanics, have been successfully applied to cementitious materials, in order to predict the hydration-induced evolutions of their elastic stiffness [9,23,24,25,26,27,28], their compressive strength [29,30,31] and their viscoelastic behavior [22,32,33]. The multiscale model is used to “downscale” results from the aforementioned macroscopic ultra-short creep tests on polymer-modified cement pastes [9] to the creep properties of micrometer-sized polymers. Modeling the Hydration-Induced Evolutions of the Non-Aging Creep Properties of Polymer-Modified Cement Pastes
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