Experimental study on the strength behaviors of municipal solid waste incineration bottom ash using ultrasonic wave velocity tests

To investigate the physico-mechanical properties of municipal solid waste incineration bottom ash (MSWIBA), the factors influencing the strength characteristics of MSWIBA were studied using an ultrasonic wave velocity test, to investigate its physico-mechanical properties. The test results show that the curing age, dry density, temperature, particle size, moisture content, and soaking time in water affect the strength of MSWIBA. The analyses of the wave velocity suggest that the strength of MSWIBA increases with its curing age and dry density. The strength increases rapidly over a curing age of 3-7 days but increases slowly after 14 days. In addition, the strength increases under an increase in temperature within the range of 20-50 degrees C, and it tends to stabilize above 50 degrees C. Moreover, the moisture content and particle size have a significant effect on the strength. MSWIBA, with a particle size of 0-2 mm, exhibits the greatest strength, and its strength is maximal at the optimum moisture content (15%). The soaking time in water has an adverse impact on the strength of MSWIBA during the first 80 h, decreasing its strength by approximately 5%. Moreover, the Poisson's ratio of MSWIBA is determined using wave velocity ratios from elastic theory.