Effects of high temperature on the pore structure and strength of plain and polypropylene fiber reinforced cement pastes

• Published in: Fire technology 2003, Vol.39 (1), p.23-34
• Main Authors: KOMONEN, Juha, PENTTALA, Vesa
• Format: Article
• Language: English
• Subjects: Applied sciences; Building technical equipments; Buildings; Buildings. Public works; Cement; Cement concrete constituents; Cements; Composition (specifications, compliance criterid, standards, certification, control, patents, etc.); Exact sciences and technology; Fibers; Fire behavior of materials and structures; Fire protection; High temperature; Hydration; Low temperature; Materials; Mercury; Miscellaneous (including polymer concrete, repair and maintenance products, etc.); Porosity; Portland cement; Temperature effects; Water
• ISSN: 0015-2684; 1572-8099
• DOI: 10.1023/A:1021723126005

The effect of high temperature on the residual properties of plain and polypropylene fiber reinforced Portland cement paste was investigated. Plain Portland cement paste having water/cement ratio of 0.32 was exposed to the temperatures of 20, 50, 75, 100, 120, 150, 200, 300, 400, 440, 520, 600, 700, 800, and 1000 degrees C. Paste with polypropylene fibers was exposed to the temperature of 20, 120, 150, 200, 300, 440, 520, and 700 degrees C. Residual compressive and flexural strengths were measured and pore structure of the pastes was determined by mercury porosimetry. The total porosity of the pastes more than doubled when exposure temperature was increased from 20 degrees C to 1000 degrees C. The gradual heating coarsened the pore structure. The most notable coarsening of pore structure--together with strength loss--took place at exposure temperatures exceeding 600 degrees C. At 600 degrees C, the residual compressive capacity (f c600 degrees C /f c20 degrees C ) was still over 50% of the original. Strength loss due to the increase of temperature was not linear. Polypropylene fibers produced a finer residual capillary pore structure, decreased compressive strengths, and improved residual flexural strengths at low temperatures. According to the tests, it seems that exposure temperatures from 50 degrees C to 120 degrees C can be as dangerous as exposure temperatures 400-500 degrees C to the residual strength of cement paste produced by a low water cement ratio.[PUBLICATION ABSTRACT]