Abstract: Orthogonal unconfined compression test was conducted on lead-contaminated soil solidified by curing agent CFG (cement mixed with flyash and desulphurized gypsum) to investigate the strength characteristics of treated lead-contaminated soils varying with lead ion concentration and CFG dosage. Results reveal that the unconfined compressive strength of stabilized soils increases with the growth of CFG dosage, while reduces with the climbing of lead ion concentration. In the first seven days of curing, the effect of lead ion concentration is greater than that of curing agent dosage; after seven days, the influence of the dosage of curing agent is greater than that of lead ion concentration. At 3 d and 7 d of curing, the influences of both factors on soil strength are small, while at 14 d the influence greatly increases, and at 28 d, the effect is especially significant. Furthermore, the formula of strength prediction based on curing age and CFG dosage is proposed as a reference for the treatment of lead-contaminated soil.

Key words: composite cement material, orthogonal test, unconfined compressive strength, lead-contaminated soil, flyash, desulphurized gypsum, strength prediction