The application of carbide slag-coal gangue powder stabilized soil in the immersion subgrade of expressway
A mixture of carbide slag(CS)and coal gangue powder(CG)was utilized as the stabilizer for the roadbed soil of the soaked subgrade of the Mingdong Expressway in order to increase the water stability and bearing capacity of the subgrade.The dosages of stabilizer were 5%,10%and 15%,and the quantity ratios of CS and CG were 0∶100,30∶70,50∶50,70∶30 and 100∶0.Tests of unconfined compressive strength(UCS),dry-wet cycles,water immersion,pH value detection,X-ray diffraction(XRD),scanning electron microscope(SEM)and mercury intrusion porosimetry(MIP)were conducted to evaluate the mechanical properties,water stability and microscopic characteristics of the CS-CG stabilized soil.The results show that the UCS value of CS-CG-10%-(70∶30)stabilized soil was 5.87 MPa after curing for 28 days,and the UCS was decreased to 4.77 MPa after 6 dry-wet cycles.It was evident that the bearing capacity and water stability were good.With increasing CS percentage,the UCS of the stabilized soil after 30 days'immersion increased.The UCS of CS-CG-10%-(100∶0)and CS-CG-10%-(70∶30)stabilized soil were 6.29 and 5.74 MPa respectively.The pH value increased with an increase of CS-CG dosage and CS proportion,but decreased slightly as the dry-wet cycles increased.The pH value of CS-CG-10%-(70∶30)stabilized soil was 9.71.After adding CS-CG,a large number of hydration products such as C-(A)-S-H gel,Ca(OH)2 crystal and ettringite were produced in the stabilized soil,which improved the pore structure and increased the UCS.With more dry-wet cycles,the hydration products increased,which was benefit for the properties of the stabilized soil,but the pore diameter also increased.It can be seen that CS-CG stabilized soil has good bearing capacity and water stability.Considering the effects on the environment,the pH value of stabilized soil should not be too high,so it is recommended that the best dosage of CS-CG stabilizer is 10%,and the best ratio of CS-CG is 70∶30.
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