A Comparative Study on the Effect of Class C and Class F Fly Ashes on Geotechnical Properties of High-Plasticity Clay

Clays generally have a low strength and capacity, and additives are usually used to stabilize them. In recent years, using fly ash to stabilize soil has decreased environmental pollution while also having an economic benefit. The objective of this study is to perform a comparative investigation on the effect of class C and class F fly ashes on geotechnical properties of high-plasticity clay using the Atterberg’s limit, compaction, California Bearing Ratio (CBR), and unconfined compressive strength tests. The results showed that with an increase in the amount of fly ash, there was a decrease in the maximum dry density and an increase in the optimum moisture content. Moreover, an addition of fly ashes of up to 25% caused a reduction of the liquid limit and plasticity index, and an increase in the maximum unconfined compressive strength and CBR. Lengthening the curing time had a positive impact on the unconfined compressive strength of the soil. The soil samples with class C fly ash were seen to possess more efficient geotechnical properties as compared to class F fly ash.

Examining the Effects of Suction and Nonlinear Strength Envelopes on the Stability of a High Plasticity Clay Slope

Slope failures in high plasticity clay deposits are common occurrences in many parts of the world. In western and central Alabama, expansive Prairie clays are commonly found, and shallow slope failures have occurred in both fill and cut slopes containing these high plasticity clays. The objective of this study was to examine the effects of suction and the use of nonlinear strength envelopes on the embankment stability of a section of highway AL-5. The testing program consisted of fifteen ring shear tests performed using a Bromhead Ring Shear Device. The results of the tests were used to develop both linear and nonlinear fully softened and residual strength envelopes. The saturated strength envelopes are then used in a limit equilibrium slope stability analysis with and without the effects of suction. The results show stability (factor of safety >1) for all cases except the residual friction angle without suction. Given these results, large slope failures are unlikely to occur in this area, but surficial failures and deformations due to creep may be possible. These results demonstrate the importance of considering the effects of suction and nonlinear strength envelopes when examining the potential for shallow slope failures in high plasticity clays.

EFFECT OF ADDING WOOD POWDER ASH ON CBR VALUE IN STABILIZED HIGH PLASTICITY CLAY CEMENT AND LIME

<p>Cement and lime are widely used as stabilizing agents for soft clays. Some pozzolanic materials have also been used as additives such as asphalt, geosta, fly ash (geopolymer), base ash, salt. Industrial waste such as rice husk ash, coal burning ash (geopolymer) is also used as an alternative for stabilization materials. This research aims to study the effect of sawdust ash, as wood waste, to replace cement and lime on the stabilization of high plasticity clay. The effectiveness of sawdust ash, in this study, was evaluated from the CBR value. The test samples were also reviewed under conditions with and without immersion and with and without curing. Based on the test results, lime is very effective as an additive because it increases the CBR value of more than 100 at a level of 10%. Wood husk ash also increases the CBR value by 100%. The use of cement, lime and wood husk ash requires curing time so that there is a strong bond between the clay and additives. The use of additives without curing did not increase the CBR value. In the stabilization of clay with 10% lime, replacement of lime with wood husk ash by 4%-6%, can be used as a road sub-grade with good quality.</p>

PERUBAHAN POTENSI MENGEMBANG TANAH EKSPANSIF YANG DISTABILISASI SECARA FISIS DAN MEKANIS

Expansive soil has a high swelling and shrinkage ability which can damage the buildings above it. Glagahagung Village, Purwoharjo District, Banyuwangi Regency is one of the areas suspected of having this type of soil. Residents often experience problems in their residential buildings every year, such as cracks in floors, walls, columns, and beams. Several methods can be used to improve expansive soil, including physical and mechanical stabilization. In this study, lime and cement were used as physical stabilizers. On the other hand, sand is used as a mechanical stabilizer. Physical and mechanical parameters will be observed in the stabilization process. Based on the three stabilizers, a 5% cement mixture can be the best alternative. Cement stabilizers can increase the maximum dry volume weight, reduce the rate of soil swelling, and change natural soils' classification from high plasticity clay to silty sand.