Rapid Compressive Strength Achievement of Coal Bottom Ash Based Geopolymer by Employing Microwave Energy

摘要

Coal bottom ash (CBA), one of the coal combustion byproducts, is a source material good enough for the synthesis of geopolymers considering its high silica and alumina contents, although it has not been used widely because of large particle size. We grind CBA to have a mean particle size of 44.57 μm, and synthesize the geopolymer by activating it with 14 M NaOH solution. To achieve a high compressive strength within a short time, we synthesize the geopolymer by following the procedure: (1) mix CBA with an adequate amount of activator NOT to make it flowable, and then mold it in 5 cm cube, (2) demold specimens and heat them in 75 °C oven below 36 hours, and then (3) irradiate 700 W microwave for several minutes. The compressive strength reaches to above 40 MPa by microwaving specimen for 3 minutes after oven curing for 36 hours. Our experiment shows that high compressive strength can be achieved rapidly by employing microwave combined with conventional oven curing.