Geoenvironmental and mechanical properties of a fly ash

The geoenvironmental and mechanical properties of a fly ash (coal ash) in Japan were investigated experimentally. Geoenvironmental consideration is focused on the concentration of C_r⁶⁺ in solution/leakage. Batch contact test and column percolation test results indicate that mixing the fly ash with Ariake clay with a clay/fly ash ratio (C/F ratio) of larger than 20:80 by dry weight, or mixing the fly ash with 5% cement and cured for 1 week, the concentration of C_r⁶⁺ in the solution/leakage was less than 0.05 mg/l (Japanese environmental standard). The strength and modulus of compacted fly ash and the fly ash-cement-Ariake clay mixture were investigated by unconfined compression tests. For the fly ash alone or adding 5% cement to the fly ash and mixed with Ariake clay with a C/F ratio of 20:80, their unconfined compressive strength (q_u) was more than 100 kPa and the secant modulus corresponding to a tress level of 50% of the strength (E₅₀) was more than 10.0 MPa. For the samples of the fly ash plus 5% cement, q_u and E₅₀ values were more than 10 times of that the fly ash alone.