Unconˆned compression tests and suction measurements were carried out in the present work on sandy specimens with distinct Class F ‰y ash amounts, lime contents, porosities and curing periods to assess key parameters controlling strength of ‰y ash-lime amended soil. A special eŠort has been allocated in order to develop a dosage methodology for ‰y ash-lime improved soils based in a rational criterion, as it exists in the concrete technology where the water/cement ratio plays a fundamental role in the assessment of the target strength. The results show that the unconˆned compressive strength (UCS) increased linearly with the amount of lime for soil-‰y ash-lime mixtures at all curing time periods studied. A power functionˆts better the relation UCS-porosity for soil-‰y ash-lime mixtures. The bigger the amount of ‰y ash and the curing time, the larger the UCS for any given porosity and lime content. Finally, the porosity/volumetric lime content ratio, in which volumetric lime content is adjusted by a coe‹cient (in this case a unique value-0.12-was found for all soil-‰y ash-lime mixtures and all curing periods studied) to end in single correlations for each curing period, show to be a good parameter in the evaluation of the unconˆned compressive strength of the soil studied (UCS varies non-linearly with the porosity/volumetric lime content ratio in the case of ‰y ash-lime addition).
The aim of this study is to assess the strength controlling parameters of a sandy soil (Botucatu residual soil (BRS)) treated with industrial by-products (basaltic powdered rock (PR) or coal fly ash (FA)) and lime, as well as to show that the porosity/volumetric lime content (η/Lv) plays a fundamental role in the assessment of the target strength. The controlling parameters evaluated were addition of industrial wastes, quantity of lime, porosity and η/Lv. The unconfined compressive strength (qu) increased non-linearly with the amount of lime and decreased with porosity for all studied mixtures. Similar equations were found relating qu to η/(Lv)0·12 for BRS–lime, BRS-PR–lime and BRS-FA–lime mixtures. Tests of potential reactivity of siliceous materials with alkalis on the materials studied indicated that the higher amount of dissolved silica in the alkaline environment of the FA, when compared with the BRS and the PR, was responsible for increasing the number of reactions with the lime and consequently increasing the strength for BRS (25% FA)–lime mixtures, when compared to BRS–lime and BRS (25% PR)–lime blends.
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