Faculty Publications
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Item Strength and Durability Characteristics of Cement and Class F Fly Ash-Treated Black Cotton Soil(Springer, 2021) Chethan, B.A.; Ravi Shankar, A.U.This paper analyses improvement of the strength and durability characteristics of black cotton (BC) soil treated with cement and Class F fly ash for pavements. The increase in cement dosage (3–14%) improved the UCS, but the specimens could not resist WD durability cycles. In order to improve, industrial by-product Class F fly ash was used in addition to the cement. Different combinations of cement (10, 12, and 14%) and fly ash (10, 15, 20, 25, and 30%) replacements were evaluated for strength and durability characteristics. The higher dosage of fly ash reduced the plasticity with uniform distribution of cement cluster formations, leading to higher UCS. The soil mixes with (cement + fly ash) stabilizer combinations (10 + 30), (12 + 30), (14 + 25), (14 + 30) were stable against WD test with soil loss < 14%. Mix with (14 + 25) stabilizer showed a maximum retained UCS of 3.6 MPa at 2.9% moisture content (MC) after 12 WD cycles. However, most of the mixes showed high resistance to the FT test. The retained UCS of FT tested specimens was more due to low variations in moisture content. Mix with (14 + 30) stabilizer showed a maximum retained UCS of 2.6 MPa at 23.3% MC after 12 FT cycles. The soil samples with high cement and fly ash contents, with 90 days curing, can exhibit significant strength and more resistance to WD and FT cycles with soil loss < 14%. After drying, severe damage to WD specimens was observed due to the drastic absorption of water during the wetting cycle. Durable samples showed good plunger penetration resistance with an expansion of < 2%. Scanning electron microscopy (SEM) images showed the formations of cemented interclusters. CSH formed resulted in strength improvement, as observed from XRD patterns. The 7 days cured WD specimens did not exhibit any volume expansion on soaking, thawing in water. A maximum volumetric shrinkage of 3.2% on drying and 1.91% on freezing was observed for stabilized soil. Hence, the stronger and durable stabilized soil mixes with high volume stability can be used for pavements. © 2021, Indian Geotechnical Society.Item Effect of Flash Flood and Weather Changes on Unconfined Compressive Strength of Cement- and Fly Ash-Stabilized Black Cotton Soil Used as Road Materials(Springer, 2023) Chethan, B.A.; Ravi Shankar, A.U.Stabilized soil naturally undergoes variation in moisture content and temperature during seasonal weather changes. In this investigation, the influence of these weather changes on unconfined compressive strength (UCS) of black cotton (BC) soil stabilized with ordinary Portland cement (43 grade) and class F fly ash was studied. Cement dosage was varied from 3 to 10%, along with different combined dosages of (cement + fly ash) (where fly ash < 32%) for stabilizing various mixes. The UCS specimens were cured for 0 (immediately after preparation) 3, 7, 28, 60, and 90 days in a desiccator and subsequently submerged for 24 h in water to ensure saturation. The flash flood effect was evaluated in terms of strength reduction by correlating UCS of saturated specimens (UCSs) with UCS of desiccator-cured specimens. The stabilized materials’ resistance to wetting–drying (WD), freezing–thawing (FT) durability tests and subsequent UCS retained over time were determined. The UCS values increased substantially at higher cement and fly ash contents and with the curing period, whereas a notable reduction in UCSs values was observed for saturated samples. However, the samples with high cement and fly ash contents exhibited low moisture susceptibility with lesser strength reduction. The UCS and UCSs values are linearly correlated with R2 values > 0.9. All the specimens were intact with improved volume stability at higher cement and fly ash dosages during saturation and drying. Mixes with high cement and fly ash dosages shown improved resistance to WD cycles, whereas at a low dosage, most of the mixes failed during the second wetting cycle due to a drastic absorption of water after the first drying cycle. All FT specimens were intact with considerable strength retained after 12 cycles exhibiting a minimal mass loss. The formation of hydration products has justified the strength gain as observed from scanning electron microscope (SEM) images, energy dispersive X-Ray analysis (EDAX), and X-ray diffraction (XRD) plots. © 2021, The Author(s), under exclusive licence to Chinese Society of Pavement Engineering.