SULFATE ATTACK OF PORTLAND CEMENT STUDIED BY X-RAY MICROTOMOGRAPHY (MICRO-CT), S.R. Stock, K. Ignatiev, A.P. Wilkinson, N. Naik, K.E. Kurtis, pp. 128-132
نویسندگان
چکیده
Attack of Portland cement by ambient sulfates presents a considerable risk to structures in some environments. In this study, x-ray microtomography, a high resolution variant of medical “CT”, noninvasively mapped the progression of damage in Portland cement resulting from exposure to an aqueous solution of Na2SO4 (sodium ion concentration of 10,000 ppm). Cement paste samples from water-to-cement ratios w/c = 0.45, 0.50 and 0.60 and exposures between 0 and 120 days were examined. Microtomography revealed cracking that would have been attributed to sample preparation during sectioning of the friable material and allowed damage to be followed in individual specimens. The greater w/c, the more rapidly damage progressed, and spalling originated at the corners of the 10 mm diameter, 40 mm long cylindrical samples.
منابع مشابه
Multi-mode X-ray Study of Sodium and Magnesium Sulfate Attack on Portland Cement Paste
Sulfate attack is potentially one of the most damaging forms of degradation affecting portland cement-based materials. However, despite over six decades of study, considerable uncertainty remains in optimally selecting and proportioning materials for sulfate resistance, and current understanding of the actual mechanisms of degradation in sulfate environments remains incomplete. In this research...
متن کاملFATIGUE CRACKS IN ALUMINUM SAMPLES STUDIED WITH X-RAY PHASE CONTRAST IMAGING AND WITH ABSORPTION MICROTOMOGRAPHY, S.R. Stock, K. Ignatiev, G.R. Davis, J.C. Elliott, K. Fezzaa, W.-K. Lee, pp. 123-127
X-ray absorption microtomography, a high resolution variant of medical “CT”, quantifies threedimensional microstructures efficiently and noninvasively. With this imaging modality, determination of the three-dimensional spatial distribution of crack opening as a function of applied load has helped clarify important physical processes of roughness-induced fatigue crack closure. There is a real ne...
متن کاملMINERAL PHASE MICROSTRUCTURE IN TEETH OF THE SHORT SPINED SEA URCHIN (Lytechinus variegatus) STUDIED WITH X-RAY PHASE CONTRAST IMAGING AND WITH ABSORPTION MICROTOMOGRAPHY, S.R. Stock, T. Dahl, J. Barss, A. Veiss, K. Fezzaa, W.K. Lee, pp. 133-138
X-ray absorption microtomography, a high resolution variant of medical “CT”, and synchrotron x-ray phase contrast imaging reveal the distribution of mineral within teeth of the sea urchin Lytechinus variegatus. Data from these imaging modalities on intact teeth are compared with histochemically stained thin sections observed with transmission optical microscopy. Because these teeth grow continu...
متن کاملX-ray Microtomography of an Astm C109 Mortar Exposed to Sulfate Attack
X-ray microtomography can be used to generate three-dimensional 5123 images of random materials at a resolution of a few micrometers per voxel. This technique has been used to obtain an image of an ASTM C109 mortar sample that had been exposed to a sodium sulfate solution. The three-dimensional image clearly shows sand grains, cement paste, air voids, cracks, and needle-like trystah growing in ...
متن کاملX-RAY MICROBEAM DIFFRACTION COMPARISON OF MESOTEXTURES IN PLATES OF THREE ALUMINUM ALLOYS, K. Ignatiev, S.R. Stock, Z.U. Rek, pp. 56-61
Samples from the center of plates of rolled aluminum alloys AA 8090 and 7055 were investigated using microbeam diffraction and polychromatic synchrotron x-ray radiation. Transmission Laue patterns from different parts of the samples were compared and analyzed for the presence of mesotexture similar to that observed previously in the center of plates of aluminum alloy AA 2090 (i.e., near single-...
متن کامل