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Stepkowska, E.T., Blanes, J.M., Franco, F., Real, C. and Pérez-Rodriguez, J.L. (2004) Phase Transformation on Heating of an Aged Cement Paste. Thermochimica Acta, 420, 79.

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• TITLE: Effect of High Temperatures on the Microstructure of Cement Paste

  AUTHORS: M. A. Tantawy

  KEYWORDS: Cement paste, C-S-H, Portlandite, Dehydration, Microstructure

  JOURNAL NAME: Journal of Materials Science and Chemical Engineering, Vol.5 No.11, November 17, 2017

  ABSTRACT: The microstructural and compositional changes within the cement paste exposed to high temperatures were monitored by XRD, FTIR, TGA/DTA and SEM techniques to understand the nature of decomposition of C-S-H gel and the associated physicomechanical properties of thermally damaged cement paste. OPC paste (w/c ratio 0.27) was hydrated for 28 days then fired up to 750°C for 2 hours (heating rate 10°C/min). The relative mass percent of calcium hydrates and portlandite was estimated by calculations derived from TGA results. Beyond 450°C, the percentage of portlandite sharply diminishes and C-S-H progressively decomposes into C2S and C3S until complete loss of calcium hydrates content occurs at 750°C. An increase of the total porosity, severe loss in mechanical strength and propagation of harmful cracks occurs. The thermal shock as a result of cooling of the heated cement paste and the rehydration of lime enhance the propagation of harmful cracks.