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Rashid K.,Hokkaido University | Ueda T.,Hokkaido University | Zhang D.,Zhejiang University | Miyaguchi K.,Denki Kagaku Kogyo Kabushiki Kaisha DENKA | Nakai H.,Maeda Kosen
Construction and Building Materials | Year: 2015

Abstract This paper presents research outcomes of an experimental program carried out to determine the influence of moisture and temperature on the polymer cement mortar (PCM)-concrete interface properties along with intrinsic properties of constituents. Performance of materials was evaluated using split tensile test of both composite and bulk specimens and also by observing glass transition temperature, melting point and molecular weight of extracted polymers from PCM. All specimens were exposed to different temperature conditions for temperature exposure, or wetting and drying cycles and continuous immersion in water for moisture exposure. Significant reduction in strength was observed of composite and bulk specimens with the increase in temperature, while the effect of moisture was marginal. Finally, design formulas were developed to predict the interfacial split tensile strength under various exposure conditions, by using the control tensile strength of PCM and concrete. © 2015 Elsevier Ltd. Source

Le Saout G.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Lothenbach B.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Hori A.,DENKA Chemicals GmbH | Higuchi T.,Denki Kagaku Kogyo Kabushiki Kaisha DENKA | Winnefeld F.,Empa - Swiss Federal Laboratories for Materials Science and Technology
Cement and Concrete Research | Year: 2013

The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C-S-H has a similar composition as in OPC with no additional Al to Si substitution. As in CSA-OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems. © 2012 Elsevier Ltd. All rights reserved. Source

Higuchi T.,Denki Kagaku Kogyo Kabushiki Kaisha DENKA | Eguchi M.,Denki Kagaku Kogyo Kabushiki Kaisha DENKA | Morioka M.,Denki Kagaku Kogyo Kabushiki Kaisha DENKA | Sakai E.,Tokyo Institute of Technology
Cement and Concrete Research | Year: 2014

An expansive additive (CSA) containing lime (CaO), ye'elimite (3CaO·3Al2O3·CaSO4) and anhydrite (CaSO4) was treated with high-temperature carbonation, and used to make mortar samples for expansion tests. After 1 day, the mortar made with the CSA which underwent high-temperature carbonation (treated CSA) expanded to a lesser degree than the mortar made with the untreated expansive additive (CSA). However, from 1 to 3 days significant expansion occurred in the treated-CSA mortar, and by day 7, the sample had expanded ~ 23% more than the CSA mortar. The hydration of the CSA was suppressed until 6 h after it came into contact with water; in particular, reaction of free lime was suppressed. Loss of expansion performance during the accelerated weathering test was significantly reduced by high-temperature carbonation, and the weathering rate was reduced by a factor of ~ 7. The CO2 and calcite contents increased with high-temperature carbonation, and a 0.2-μm-thick calcite film formed on the lime surface. This film reduces the extent of lime reaction before formation of the cement matrix, resulting in increased expansion, and improvement in the stability towards weathering. © 2014 Published by Elsevier Ltd. Source

Su J.,Kyushu University | Su J.,Tokyo Institute of Technology | Amamoto Y.,Kyushu University | Sato T.,Kyushu University | And 8 more authors.
Polymer (United Kingdom) | Year: 2014

Reversible cross-linking reactions of alkoxyamine-appended polymers with low glass transition temperature (Tg) were successfully carried out under bulk conditions. The low-Tg polymers with alkoxyamine units in the side chains were synthesised by radical copolymerisation of 2-ethylhexyl acrylate and two kinds of alkoxyamine-containing acrylate monomers. By heating the low-Tg polymers under bulk conditions at 100 C, cross-linked polymers were formed by radical exchange reactions between alkoxyamine units, and a transition from a liquid-like flowable polymer state to a rubber-like polymer state was confirmed. A de-cross-linking reaction was also accomplished by radical exchange reactions between the cross-linked polymers and an added alkoxyamine-containing small molecule or stable nitroxyl radical, which resulted in transition to the flowable state again. The structural transition between low-Tg linear polymers and cross-linked polymers were characterised by 1H and 13C NMR spectroscopy, Fourier transform infrared spectroscopy, rheology measurement, swelling experiment, and gel permeation chromatography measurement. © 2014 Elsevier Ltd. All rights reserved. Source

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