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Calcium carbide residue (CCR) is a waste product from acetylene gas factories, which is rich in calcium hydroxide []. Because clayey soils contain high amount of natural pozzolanic materials (silica and alumina), CCR can be used as a soil stabilizer. This article presents the engineering properties of CCR-stabilized silty clay to ascertain its performance in pavement base and subbase applications. The input of CCR, which reduces the plasticity index of the clay, increases the optimum water content (OWC) and decreases the maximum dry unit weight () of the stabilized clay. The CCR fixation point, simply obtained from the index test, is proved as a practical indicator for determining the CCR content to obtain the required engineering properties at a particular molding water content. The state of water content controls the densification, chemical reaction, and water absorption capacity. The soaked engineering properties are thus dependent upon the state of water content. For a particular CCR content, the optimum water content is the most appropriate in terms of strength, swelling and collapse behaviors, and bearing capacity. The lower water content is not sufficient for the chemical reaction, while the higher water content yields a higher water/binder ratio. The water absorption is smallest for the CCR-stabilized samples compacted at the OWC. To conclude, the optimal mix proportion is the CCR fixation point at OWC. CCR stabilization is more effective than lime stabilization in terms of engineering, economic, and environmental viewpoints. [ABSTRACT FROM AUTHOR]

The potential of woodash to stabilize clay soil was evaluated. The evaluation involved the determination of the geotechnical properties of clay soil in its natural state as well as when mixed with varying proportions of woodash. The parameters tested included the particle size distribution, specific gravity, Atterberg limits, compaction characteristics, California bearing ratio (CBR) and the compressive strength. The CBR and strength tests were repeated after 28-day curing of the treated samples. Results showed that the geotechnical parameters of clay soil are improved substantially by the addition of woodash; plasticity was reduced by 35% and CBR and strength increased by 23–50% and 49–67%, respectively, depending on the compactive energy used. The highest CBR and strength values were achieved at 10% woodash. Results also showed that curing improved the strength of the woodash-treated clay. However, the strength gain was short lived as the strength quickly decreased after 7–14 days of curing. These results imply that although woodash provides some of the beneficial effects of lime in soil stabilization, such as plasticity and swell reduction, improved workability, and strength increase, it is unlikely to be a substitute for lime as strength gain is short lived. [ABSTRACT FROM AUTHOR]

This paper aims to show that the addition of lime and lime/cement can significantly improve both the stiffness and the resistance to permanent deformation of clay soils even under adverse, though realistic, curing conditions. The AASHTO Guide for Design of Pavement Structures incorporates a method of calculating subgrade resilient modulus (MR), using repeated load triaxial testing, with respect to seasonal variations of the soil’s moisture content and temperature, while the equivalent British specifications adopt a “soaked California bearing ratio” approach. In practice 8°C is a realistic worst case curing temperature in situ and a (necessarily) wetter underlying clay will allow water to be drawn into the chemically treated layer during curing as a result of suctions, while the material will experience a small degree of confinement after compaction. These conditions have been replicated in a series of repeated load triaxial tests on lime and lime/cement stabilized, predominantly kaolinitic clay and the results compared with those from sealed samples, which were also cured at 8°C. All samples were subjected to 100 cycles of stresses representing 20, 40, 60, and 80% of the relevant undrained shear strength. This paper concludes that allowing the samples access to water is necessary if field performance is to be replicated. [ABSTRACT FROM AUTHOR]