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Microstructure and mechanical properties of macro-defect-free cements
The mechanical properties of macro-defect-free (MDF) cements were investigated with the help of fracture mechanics and rheology; transmission electronic microscopy (TEM) and scanning electronic mircoscopy (SEM) were used to characterize the microstructure. The microstructure was found to consist of nanosized hydration products embedded in a cross-linked polymer matrix. MDF cements show very high fracture strengths due to both a high stress intensity factor, and a small critical defect size. An investigation of Polyvinylalcohol-(PVA)-aluminate ion films allowed to discuss the origin of the high K(ic). Ionic cross-linking, although present, is probably not the main toughening mechanism occurring in these cements, because the tensile strength of the films was seen to decrease with the addition of aluminate ions. The high critical stress intensity factor was ascribed to the composite structure of the cement, which is observed at different scales: 15 micron (cements grains) and 20 micron (hydrated products). Bridging effects were also shown to have an influence on the fracture work. On the other hand, the critical defect size is also a very important parameter affecting the mechanical properties. It was shown that changing the processing variables (molecular weight, or pressing temperature, for examples) may have an influence on both K(ic) and a(c), leading to complicated evolutions of the tensile strength.
Microstructure and mechanical properties of macro-defect-free cements
The mechanical properties of macro-defect-free (MDF) cements were investigated with the help of fracture mechanics and rheology; transmission electronic microscopy (TEM) and scanning electronic mircoscopy (SEM) were used to characterize the microstructure. The microstructure was found to consist of nanosized hydration products embedded in a cross-linked polymer matrix. MDF cements show very high fracture strengths due to both a high stress intensity factor, and a small critical defect size. An investigation of Polyvinylalcohol-(PVA)-aluminate ion films allowed to discuss the origin of the high K(ic). Ionic cross-linking, although present, is probably not the main toughening mechanism occurring in these cements, because the tensile strength of the films was seen to decrease with the addition of aluminate ions. The high critical stress intensity factor was ascribed to the composite structure of the cement, which is observed at different scales: 15 micron (cements grains) and 20 micron (hydrated products). Bridging effects were also shown to have an influence on the fracture work. On the other hand, the critical defect size is also a very important parameter affecting the mechanical properties. It was shown that changing the processing variables (molecular weight, or pressing temperature, for examples) may have an influence on both K(ic) and a(c), leading to complicated evolutions of the tensile strength.
Microstructure and mechanical properties of macro-defect-free cements
Mikrostruktur und mechanische Eigenschaften makrodefekt-freier Zemente
Brotzmeyer, D. (author) / Frouin, L. (author) / Montardi, Y. (author) / Orange, G. (author)
Journal of Materials Science ; 30 ; 4138-4144
1995
7 Seiten, 14 Bilder, 1 Tabelle, 15 Quellen
Article (Journal)
English
Calciumaluminat , Zement , Mikrogefüge , mechanische Eigenschaft , Materialbruch , Rheologie , Transmissionselektronenmikroskopie , Rastermikroskop , mechanische Festigkeit , Zugfestigkeit , Spannungsintensitätsfaktor , Werkstofffehler , Bruchmechanik , Temperatur , Transmissionselektronenmikroskop , Rasterelektronenmikroskop , Polymer , Matrix (Grundmasse) , Polymermatrix , Matrix , Calciumsilicat , Polyvinylalkohol , Vorspannen , Molekulargewicht
Microstructure and mechanical properties of macro-defect-free cements
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