Search

This study presents the characteristics of municipal solid waste (MSW) incineration ash obtained from an electric energy generation plant and evaluates the MSW ash applicability in base road pavement layers through the mixture of ash with a nonlateritic regional clay soil. Chemical, physical, and mechanical tests and the mechanistic-empirical design for a typical pavement structure were carried out on the pure soil and also in the soil mixture with the addition of different ash content (20 and 40%). Fly ash reduced the expansion of the material, showing an increase in the California bearing ratio (CBR) and resilient modulus value. The results are satisfactory, depending on the content and type of ash used, highlighting the positive work of MSW fly ash for its use in base road pavement layers. [ABSTRACT FROM AUTHOR]

This study evaluated the constituent make up of simulated rainwater runoff from Class C fly ash–stabilized and nonstabilized clay soil using laboratory test pads to assess the potential for impacts to surface water from the use of uncovered fly ash–stabilized soils as potential roadbed material. Recirculated runoff from test pads was sampled and tested during three simulated rainfall events over an 84-day trial period. All samples were analyzed for trace metals. Analytical results from the simulated runoff were screened to identify five indicator parameters in the runoff that were used as the basis for assessing potential environmental effects to surface waters. Runoff water results from fly ash–stabilized test pads for these indicator parameters were compared to water quality benchmarks. Based on the low concentrations measured in runoff relative to applicable criteria, and on the conservative nature of the experimental methods relative to typical field conditions, we concluded that surface runoff from fly ash–stabilized soil would not present significant adverse effects to surface water if used uncovered on low traffic exposed surfaces. [ABSTRACT FROM AUTHOR]

This paper presents, by way of comparison, the effect of fly ash on the volume change of two different types of clay, one a highly plastic expansive clay and the other a nonexpansive clay, also of high plasticity. Expansive clays swell on absorbing water and shrink on drying. Nonexpansive clays undergo large compression at high water contents. The effect of fly ash content on free swell index, swell potential, and swelling pressure of expansive clays was studied. Compression index and secondary consolidation characteristics of both expansive and nonexpansive clays were also determined. Swell potential and swelling pressure, when determined at constant dry unit weight of the sample (mixture), decreased by nearly 50% and, when determined at constant weight of clay, increased by nearly 60% at 20% fly ash content. Compression index and coefficient of secondary consolidation of both the clays decreased by 40% at 20% fly ash content. [ABSTRACT FROM AUTHOR]

Laboratory tests have been carried out in order to evaluate the improvement in engineering properties relevant to highway design and construction obtained when clayey subgrade soils are stabilized with lime or fly ash. The experimental program included California bearing ratio (CBR) tests to evaluate the bearing strength of stabilized soils used as working platforms during highway construction. The admixture of lime or fly ash caused an increase in the plasticity limit, while both the liquid limit and the plasticity index of the soils have been reduced. Substantial increases in the California bearing ratio value, higher than those of the soil-fly ash mixtures, have been obtained when the soil samples were mixed with lime. The swelling after a 4-day soaking period has been reduced with the addition of both additive materials. The increase in optimum moisture content acts subsidiarily to the increased CBR value, particularly at high lime or fly ash percentages. An analogous effect has been found for the maximum dry density reduction. [ABSTRACT FROM AUTHOR]