Bio-carbonization of Reactive Magnesia for Sandy Soil Solidification

Bio-carbonization of reactive magnesia (r-MgO) is a new technology for sandy soil solidification. In this study, two sets of tests were conducted to investigate the influence of r-MgO contents on the bio-solidification effects of sandy soils, with the analysis of the unconfined compressive strength (UCS), permeability coefficient, sonic time value, and precipitation content. The relationship between r-MgO contents and solidification effects with a single treatment cycle was studied in the first sand solidification test. Then, the second sand solidification test was further conducted until their permeability coefficient reached about 10−6 cm/s to determine the maximum treatment cycle under various r-MgO contents. The results showed that the UCS, permeation resistance, and carbonate precipitation content were positively related to the r-MgO content if the solidification treatment was applied only once, while the sonic time value showed an opposite trend. Moreover, the maximum treatment cycle obtained under various r-MgO contents varied greatly. A high dosage of r-MgO could clearly reduce the maximum number of treatment cycles of the sand column, especially the r-MgO content larger than 15%. Decreased treatment cycle reduced carbonate precipitations in the sand column and decreased the UCS by over 40%. There was a close relationship between UCS and average carbonate precipitation contents for the bio-carbonated sand columns with the only one treatment cycles. However, the UCS of sand columns with multiple treatment cycles varied greatly within a similar average precipitation content. The results of this study lay a solid foundation for applying bio-carbonization of r-MgO in sandy soil solidification.