The Effect of Bottom Ash on Soil Suction and Resilient Modulus of Medium-Plasticity Clay

The effect of adding bottom ash to medium-plasticity clay as a soil stabilizer was evaluated in this study by performing triaxial resilient modulus tests. Two log–log resilient modulus prediction equations found in the literature (MEPDG and NCHRP 1-28) were selected and calibrated for mixtures of bottom ash and clay at different moisture contents. It was found that, with 25% bottom ash in the mixture, the resilient modulus increased between 5% and 23% under different stress states. The soil total and matric suctions of the mixtures were indirectly measured using the filter paper method, and the total suction parameter was incorporated in the two log–log prediction models. The nonlinear regression analysis revealed that the average goodness-of-fit statistics for one of the modified models showed highly satisfactory performance in predicting the resilient modulus values.

Evaluation of the benefits of utilization of fly ash as a material for road subgrade

The assessment of potential effects of the application of fly ash in road construction was based on the results of tests of fly ash from two thermal power plants in Serbia and three characteristic soil types: the medium plasticity clay, silty-sandy clay and high plasticity clay. The physical and mechanical characteristics of the stabilization of the above three types of soils with different percentages of fly ash and stabilizers (cement/lime) were determined in the study, and pavement designs for three traffic levels, from 1,000 to 10,000 vehicles/day were developed. The savings that can be achieved by using fly ash are going up to 16.8% depending on the type of material in the subgrade and the level of traffic. The potential savings are higher if the subsoil has lower bearing capacity, and if the traffic level is higher.