Effects of carbonation on chemo-mechanical behaviour of lime-treated soils
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ORIGINAL PAPER
Effects of carbonation on chemo-mechanical behaviour of lime-treated soils E. Vitale 1 & D. Deneele 2,3 & G. Russo 1 Received: 4 June 2020 / Accepted: 4 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In the paper, a multi-scale experimental investigation on the occurrence of carbonation and its effect on chemo-mechanical behaviour of lime-treated soil has been presented. Carbonation affects chemo-mineralogical evolution of lime-treated soils depending on the time scale at which reaction mechanism takes place. In the short term, a progressive carbonation of portlandite is responsible for the formation of calcium carbonate with consumption of available lime for pozzolanic reactions (lime carbonation). In the long term, carbonation of the secondary phases resulting from pozzolanic reactions weakens the bonding effects induced by hydrated compounds (carbonation of secondary reaction products). Mineralogical and microstructural features of lime-treated and carbonated samples have been monitored at increasing curing times by means of microstructural analyses. Triaxial drained compression tests have been performed on treated samples cured in different conditions for short and long term. Mineralogical investigations showed precipitation of calcium carbonate for lime-treated samples exposed to atmospheric CO2 since the very short term. Exposure of lime-treated sample to CO2 after precipitation of hydrated phases favoured decalcification of cementitious compounds and formation of calcium carbonate. In both cases, precipitation of calcite relevantly affects the mechanical behaviour of lime-treated samples. From the observed behaviours, it will be possible to take into account relevant factors for performing the best practice finalized to efficient and durable soil treatment. Keywords Lime-treated soil . Carbonation . Chemo-physical evolution . Microstructure . Mechanical behaviour
Introduction Minimizing costs in construction of civil infrastructures and saving natural resources favour the use of stabilising agents (such as lime, cement or alkali-activated binders) to improve engineering properties of soils not suitable as construction materials for earthworks. Lime treatment is a soil improvement technique widely used for geotechnical engineering applications (Sherwood 1993; Metcalf 1977; Little 1995; Russo 2016). Addition of lime has a strong impact on physical and mechanical properties of soils in the short and long term after * G. Russo [email protected] 1
Department of Earth Science, Environment and Resources, University of Napoli Federico II, Naples, Italy
2
GERS-LEE, Université Gustave Eiffel, IFSTTAR, F-44344 Bouguenais, France
3
Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS 44322 Nantes Cedex 3, France
treatment (Glenn and Handy 1963; Brandl 1981; Bell 1996; Rogers and Glendinning 1996; Locat et al. 1996; Sivapullaiah et al. 2000; Tremblay et al. 2001; Rao and Shivananda 2005, Vitale et al. 2020). Several studies on the basic lime-cla
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