Khashayar Farzanian

The absorption and desorption of superabsorbent polymers (SAPs) in cement mixtures containing two different glass powders as supplementary cementitious materials are examined in this paper. Two SAPs with different chemical compositions were synthesized in-house and used in the experiments. SAP absorption was investigated directly through the mass change of SAPs in cement slurries, as well as indirectly using the flow test. Scanning electron microscopy was used to monitor the desorption of SAPs using samples prepared with freeze-drying. Hydration and setting time were evaluated to explain the desorption behavior of SAPs. SAP absorption generally increased in pastes with glass powders. The desorption rate of SAPs in different pastes was shown to correlate with the onset of solid skeleton development in the pastes. The addition of SAPs reduced autogenous shrinkage in neat cement paste more than in pastes with glass powders.

The behavior of poly(sodium acrylate-co-acrylamide) copolymer hydrogels with varied chemical compositions in artificial pore solutions with three different pH values is examined. The absorption, chemical characteristics, mechanical stiffness, and desorption of the hydrogels in contact with a porous cementitious material were investigated. It was observed that the surface characteristics of the hydrogels play an important role in the desorption of hydrogels due to the capillary forces. It was shown that in the hydrogel systems studied here, the bonding between the hydrogels and the porous cementitious material is improved with an increase in the content of acrylamide in the hydrogels, and this results in an increased desorption rate of the hydrogels.

This article studies the interactions between hydrogels with two distinct chemical compositions and hydrating blended mixtures containing supplementary cementitious materials (SCMs), including Class F fly ash, slag, and silica fume. The effect of SCMs on the absorption behavior and chemical characteristics of hydrogels was investigated. The desorption of hydrogels in hydrating blended pastes was examined at various times using scanning electron microscopy. A reduction in the absorption of hydrogels was observed in the blended slurry with fly ash compared to other slurries. Hydrogels showed faster desorption in the paste with silica fume and delayed desorption in the paste with fly ash. This was attributed to faster densification of the microstructure and development of the capillary suction in the paste with silica fume and delayed densification in the paste with fly ash at early ages.