Multi-scale Laboratory Evaluation of the Physical, Mechanical and Microstructural Properties of Soft Highway Subgrade Soil Stabilized with Calcium Carbide Residue

Calcium carbide residue (CCR) is an industrial by-product, stockpiles of which are rapidly accumulating worldwide. Highway embankment construction has been identified as an avenue to consume huge quantities of CCR as an economical, less energy intensive and environmental-friendly chemical additive for soil stabilization. Previous studies have investigated the mechanical behavior of soils stabilized by CCR or blends of CCR with other additives; however, interpretation of the macro-scale geomechanical behavior of CCR stabilized soft soils from a systematically microstructural observation and analysis is relatively unknown. This paper presents a multi-scale laboratory investigation on the physical, mechanical and microstructural properties of CCR stabilized clayey soils with comparison to quicklime stabilized soils. Several series of tests were conducted to examine the Atterberg limits, particle size distribution, compaction characteristics, unconfined compressive strength, California-Bearing-Ratio and resilient modulus of the CCR stabilized clayey soils. The influences of binder content, curing time, and initial compaction state on the physical and mechanical properties of treated soils are interpreted with the aids of physicochemical and microstructural observations including soil pH, soil mineralogy obtained from X-ray diffraction and thermogravimetric analysis, and pore size distribution obtained from mercury intrusion porosimetry. Soil particle flocculation and agglomeration at the early stage and pozzolanic reactions during the entire curing time, which originate from the finer particle size, greater specific surface area and higher pH value of calcium carbide residue, are the controlling mechanisms for the superior mechanical performance of CCR stabilized soils. The outcomes of this research will contribute to the usage of CCR as a sustainable and alternative stabilizer to quicklime in highway embankment applications.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author