Tropical soils for highway construction: Peculiarities and considerations José Camapum de Carvalho a,⇑ , Lilian R. de Rezende b , Fabricio B. da F. Cardoso c , Lêda C. de F.L. Lucena d , Renato C. Guimarães e , Yamile G. Valencia f a Postgraduate Program in Geotechnics, Brasilia University, Brasilia, Brazil b Federal University of Goias, School of Civil and Environmental Engineering, Goiania, Brazil c Groundwater Coordination, National Water Agency, Brasilia, Brazil d Postgraduate Program of Environmental and Civil Engineering, Campina Grande Federal University, Campina Grande, Brazil e Furnas Centrais Elétricas S.A., Goiania, Brazil f National University of Colombia, Campus Medellin, Colombia article info Article history: Received 18 May 2015 Revised 12 October 2015 Accepted 13 October 2015 Available online 2 November 2015 Keywords: Chemical properties Mineralogy Structure Mechanical behavior Biomineralization Wastes abstract Tropical soils have properties and behavior that are different from sedimentary soils due to the diversity of environments of formation. The focus of this paper is to identify peculiarities that depend on the formation conditions of the soils and the location of highways. It discusses the use of tropical soils in highway construction, making use of physical and soil structure models to facilitate a better understanding of soil properties and behavior. The paper presents aspects ranging from deposit exploitation (borrow areas) for highway construction purposes to issues related to behavior of these soils. To do this, data from several research sources on Brazilian soils were used, noting that climate, geo- logical, geomorphological, and biological peculiarities cause different results not only from one country or continent to another but also between micro regions and even over weath- ering profiles close to one another. It was found that chemical, mineralogical, physical characteristics change and soil structure depending on the type of tropical soil studied and these characteristics have a direct influence on their behavior. Consequently, for pave- ment design, non-conventional tests should be done to define field procedures to be used during construction. In particular, some questions related to the soil water characteristic curves and compaction of fine tropical soils are highlighted. Ó 2015 Elsevier Ltd. All rights reserved. Introduction In the case of tropical soils, transported or otherwise, the formation process is more than simple rock decompo- sition, as tropical weathering involves decomposition and chemical–mineralogical and structural transformation. This gives these soils different properties and behavior from other soils formed in temperate and cold climate regions. A diagram presented by Gidigasu (1976) from Strakhov (1967) concerning depth variation and products derived from the variation of a section studied from the equator to the polar region leads to an understanding on a macro scale of the importance of climate, temperature, precipita- tion, and surface coverage on soil formation. It must be understood, however, that there is an interdependency between climate, soil formation, surface coverage and veg- etation coverage, in particular. In tropical soil formations, aspects such as geomorphology, direction and duration of exposure to weathering, and wind direction and intensity http://dx.doi.org/10.1016/j.trgeo.2015.10.004 2214-3912/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Transportation Geotechnics 5 (2015) 3–19 Contents lists available at ScienceDirect Transportation Geotechnics journal homepage: www.elsevier.com/locate/trgeo