Swelling properties and lime stabilization of N'Gaous expansive marls, NE Algeria

The interaction of marly soils and buildings in the town of N'Gaous has led to the appearance of deformations and disturbances that have affected many constructions due to the swelling of the underlying soil. In addition, when these soils are used as construction material, embankments, they are extremely problematic. In this article, three sets of samples, from three different locations, were sampled. Their average carbonate content varies from 14% to 33%.The mineralogical and microsctructural characteristics of these soils are studied by X-ray diffraction (XRD), TG/DTA and SEM analysis. These are mainly smectite clays containing kaolinite and other minor constituents. They all have similar structure, laminar texture with an arrangement of clay particles oriented parallel to the bedding and pores of varying size. These soils are very plastic and have a plasticity index ranging from 41.5 to 54.3%. It was found that the swelling pressure before any treatment ranged from 2.3 to 2.7 bars, after treatment the swelling pressure becomes stable with 5% lime, this behavior has a link with the formation of a cementitious phase of calcium silicate hydrate (CSH) type, as revealed by XRD, ATD/TG and analysis and SEM. In terms of results, it was found that the addition of quicklime has clearly reduced the swelling of the tested samples. It was also found that the presence of carbonates with the above mentioned contents in the studied samples (<50%) does not affect negatively the lime treatment of these soils. However, it promotes the stabilization of swelling, which gives encouraging results.