Microstructure Study of Ordinary Concrete Containing High Grade Portland Cement

In this experimental study, a mixture design of ordinary concrete containing Portland cement (OPCC) with a grade of ۵۰۰ kg/m۳ was made and compressive strength tests were performed at ۷, ۲۸ and ۹۰ days of curing, and X-ray diffraction spectrometer (XRD) and scanning electron microscopy (SEM) imaging were performed on concrete samples at ۹۰ days of curing at ۲۱ ℃ to evaluate the microstructure of the concrete and to compare it with the test results of this study. Increasing the curing age due to the progress of the polymerization process (hydration) improved the results of the concrete compressive strength test. In this regard, at ۹۰ days of curing, a compressive strength of ۶۴.۹۲ MPa was obtained, which was an increase of ۷۹.۴۸% compared to ۷ days. SEM and XRD results indicate that a large part of the polymerization process has been completed and a high volume of hydrated calcium aluminosilicate gel called ettringite gel (C-A-S-H) and hydrated calcium silicate gel called tobermorite gel (C-S-H) has been produced in the concrete mix. The reduction in the amount of calcium hydroxide (Ca(OH)۲) crystals in the XRD results indicates that this product has a good contribution to the hydration process and the production of hydrated gels. The high grade of cement used has played a significant role in increasing the volume of C-S-H gel production (as the main product of the chemical reaction process in OPCC) and filling the pores, cracks and capillary pores in the microstructure matrix of OPCC.

کلیدواژه ها:

OPCC ، C-S-H ، XRD ، SEM ، Concrete microstructure