دانلود رایگان مقاله تاثیر دمای کلسینه بر ویژگی های پوزولانی خاکستر علف فیل

abstract

The influence of calcining temperature on the pozzolanic properties of elephant grass ash (EGA) for application as a supplementary cementitious material is reported. Five different calcining temperatures were used (ranging from 500 to 900
C for 3 h at 100
C increments) after a first calcining step at 350
C for 3 h, a 10
C/min heating rate, and a 0.04 constant volumetric ratio between the sample and the internal furnace chamber. After calcining and high energy grinding, all ashes were characterized based on particle size distribution, oxide composition, loss on ignition, B.E.T. specific surface area, X-ray diffraction, and scanning electron microscopy. The pozzolanic behavior was investigated based on pozzolanic activity index test and compressive strength of concretes up to 180 days of curing. An expressive decrease in loss on ignition values and, consequently, increase in silica content of EGA produced at higher temperatures were observed. Overall, the results demonstrated that 600
C was the most suitable temperature for producing EGA. Additionally, the replacement of 20% (in volume) of cement by 600
C-calcining EGA did not change significantly the 28-day compressive strength of concrete, and increased the strength after 180 days of curing in relation to a reference concrete.

5. Conclusions

The effect of the calcining temperature of elephant grass on the pozzolanic properties of EGA was investigated in this study. Based on the results, the following conclusions were drawn:  The two-step calcining procedures afforded the production of pozzolanic EGA at the temperature range from 500 to 900
C. Except for the ash produced at 500
C, all other ashes showed loss on ignition values under 5%. The increase in the final calcining temperature resulted in higher density and smaller B.E.T. specific surface area.  Based on the analytical characterization and pozzolanic activity values, it was concluded that the most suitable EGA was produced at 600
C under laboratory conditions. Nevertheless, the pozzolanic activity index was not sufficiently changed by calcining temperature.