Study on laboratory and engineering application of multi source solid waste based soft soil solidification materials

Abstract

The study on multi source solid wastes solidified organic clay is limited, as well as engineering application in deep mixing pile. In this paper, steel slag powder (SS) and high calcium fly ash (HCFA) are used as raw materials, by-product sodium sulfate was recycled to develop a kind of multi-source solid waste based low carbon emission solidifying material. The solidification mechanism was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TG) and pH tests. Finally, the solidifying agent was applied to the deep mixing pile project, and the solidification effect was studied. The results reveal that the fluidity of preferred multi-source solid waste based solidifying agent slurry was 170 mm (50 °C, 1 h), which is 55% higher than that of cement. The optimum content of solidifying agent in organic clay was determined as 27%, and the unconfined compressive strength (28d) of the solidified soil was 5 MPa. Na2SO4 showed double effect of alkali activation and dense packing. The pH of solidifying agent slurry was maintained at 13.31 after the addition of 0.7% Na2SO4. More C-S-H and AFt generated under the effect of pH and SO42-. The application study reveals that the multi-source solid waste based solidifying agent deep mixing pile exhibited excellent pile integrity in organic clay. The compressive strength of deep mixing pile with the 40 kg/m solidifying agent at the curing of 14d and 28d is 0.95 MPa and 2.77 MPa, respectively. Solidifying agent deep mixing pile field strength prediction equation “y = 0.832x+ 0.1225, R2 = 0.936″ was proposed.