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8th International RILEM SIB Symposium, ANCONE, Italie, 07-/10/2015 - 09/10/2015; Clay fines are known to reduce the water resistance of bitumen-aggregates binding and cause stripping in Asphalt Concrete (AC) mixtures. To address this phenomenon, a better understanding of the mineralogical composition of aggregates is needed as well as an assessment of the bitumen-clay-water interactions. This paper contributes to reach this goal from a mineralogical perspective. The most common clays in natural aggregates, kaolinite, illite and montmorillonite, were used to prepare thin clay films and artificial clay-rich aggregates. The bitumen-clay interaction was studied using the sessile drop and the Oliensis spot tests on those thin clay films, whereas Duriez tests allowed measuring the stripping potential of AC mixtures containing the clay-rich aggregates. The results show that the water-bitumen-clay interaction and water resistance of the AC mixture are specific to the clay mineralogy. Furthermore, they show that the bitumenclay interaction may be captured upon determining the surface energy of bitumen, the chemical composition and pH value of the clay and the bitumen-clay compatibility. Hence, predicting the water resistance of clay rich AC mixtures from mineralogical properties of the bitumen-clay interaction seems feasible.

O trabalho trata da formação de solos arenosos hidromórficos com morfologia de Espodossolo, encontrados em extensas planícies, onde ocorrem áreas isoladas de Latossolos, em terrenos ondulados e bem drenados de colinas. O objetivo do estudo é elucidar a existência de relação pedogenética num sistema Latossolo-Espodossolo, verificando o possível desenvolvimento dos solos arenosos por transformação dos Latossolos. Para tanto, foram caracterizados a morfologia dos solos e seus atributos fisicos, químicos e mineralógicos. Os solos estudados apresentam desenvolvimento autóctone e filiação com a rocha granítica do embasamento, mostrando relação genética lateral entre si. Pode-se admitir transformação do Latossolo em areia branca, que se verifica numa escala métrica, de acordo com as condições de saturação hídrica crescente, provocando amarelecimento, seguido de gleização, na periferia da colina. Nesta zona, ocorre empobrecimento em argila em subsuperfície, que se estende lateralmente na planície, onde se encontram, de início, o material arenoso e, em seguida, os Espodossolos hidromórficos. Esta disposição evidencia o desenvolvimento dos Espodossolos posteriormente à formação das areias. O principal processo pedogeoquímico envolvido na perda de argila seria a acidólise, que provoca dissolução da gibbsita e caulinita. Nesse caso, a transformação dos solos teria papel preponderante na evolução do modelado com aplainamento geral do relevo. This paper deals with the genesis of hydromorphic sandy soils with spodosol morphology found in extensive flat surfaces, in which isolated zones with undulating relief emerge, containing well drained oxisols. The objective of this study was to explain the existence of pedogenetic relationship in an oxisol-spodosol system, and to verify the possible development of the sandy materials as a consequence of oxisol transformation. For this purpose, we characterized the morphology of the soils and their physical, chemical and mineralogical attributes. The studied soils showed autochthonous development and filiation to granitic rock of the crystalline basement, displaying lateral genetic relationship between them. Thus, we can admit the occurrence of oxisol transformation, verified in a metric scale, caused by increasing waterlogging conditions. As a result, soil yellowing was found, followed by gleization near the edge of the hill. In this zone, clay depletion was evidenced in the subsuperficial soil layer, extending laterally towards the plain, with the appearance of sandy materials (white sands) near the hill, followed by hydromorphic spodosol. This disposition suggests that evolution of the spodosol occurred after sand formation occurred later. The main pedogeochemical process involved in clay removal would be acidolysis, which causes gibbsite and kaolinite dissolution. Thus, soil transformation would probably have played a preponderant role in the landscape evolution resulting in overall relief planation.

Suspended matter (SM) from the Nyong basin (Cameroon, Africa), a tropical watershed, was collected by tangential flow ultrafiltration to separate particulate (>0.45 μm) and colloidal ( 20 kDa) fractions. In this basin, two distinctive systems in a selected small catchment (Nsimi–Zoetele) of the Nyong river basin have been considered: (i) colourless water (groundwater and spring) with a low suspended load ( 10 mg/l) and contains higher amounts of SM (10–20 mg/l) than the colourless water. Freeze-dried samples of SM have been analysed by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), electron paramagnetic resonance spectroscopy (EPR), and visible diffuse reflectance spectroscopy (DRS). Colourless water mainly contains mineral phases, such as poorly ordered kaolinite, plus quartz and goethite in the particulate fraction, and euhedral kaolinite plus amorphous iron oxyhydroxides in the colloidal fraction. In contrast, the SM in coloured water is mainly organic in nature. The mineral phases in the particulate fraction are similar to those from clear water, but with additional phytoliths and diatom frustules composed of biogenic opal. In the colloidal fraction, complexation of Fe3+ and Mn2+ with organic matter is evidenced by EPR, together with significant occurrence of Fe oxyhydroxides associated with organic matter. The sites of Al, Si, Fe, Mn in colloidal fractions derived from spectroscopic analyses are discussed with reference to chemical analyses performed by inductively coupled plasma mass spectrometry. Most of the observed solid phases or species correspond to those expected from published thermodynamic calculations for the same hydrosystem, except the colloidal iron oxyhydroxides in the coloured water. The presence of such iron phases is emphasised since they are expected to have large sorption capacities for numerous trace elements. The crystal chemistry of SM is used to discuss the origin of the mineral particles transported from the soil to the main rivers in terms of mechanical and chemical erosion processes.

International audience; Brazilian Latosols are characterized by low activity clay, little horizon differentiation, a weak macrostructure and a strong microgranular structure. The development of the latter that was reported as being possibly related to the fine material mineralogy, location in the landscape, parental material and biological activity is still under discussion. The aim of this study is to discuss the origin of the microgranular structure of Latosols located in the Brazilian Central Plateau. Ten Latosols (L) developed in different parent materials were selected along an approximately 350-km long regional toposequence across the South American Surface (SAS) (L1 to L4) and Velhas Surface (VS) (L5 to L10). The structure of the Latosols was studied in the field and samples of the diagnostic Bw horizons were collected for laboratory analyses. Basic soil characterization was performed on the

The Brazilian Central Plateau is constituted of the two main geomorphic surfaces: the South American surface and the Velhas surface. These surfaces were developed during the Cretaceous Superior and Tertiary and are covered by deeply weathered Latosols. The South American surface is the oldest and occupies the highest position in the landscape (950 to 1,200 m altitude) with smoothly convex plane portions. The Velhas surface is composed by irregular and slightly sloping planes and occupies in the landscape (750 to 950 m altitude). It is connected to the South American surface by areas of steep hillsides.

The purpose of this study was to investigate the impact of redox-induced changes in the organization of the clay fraction of a bulk vertisol using transmission electron microscopy. Chemical and X-ray powder diffraction (XRD) analyses indicated that the oxidized clay was composed of 32% kaolinite and 68% non-pure smectitic material, mostly a dioctahedral beidellite with octahedral Fe, according to Quantarg2 and DecompXR models.The cation exchange capacity of the soil increased from 26.1 to 65 cmolc+ kg-1 due to structural iron (FeStr) reduction and dissolution of oxide coatings. Transmission electron micrographs revealed dramatic changes upon reduction. Oxides were dissolved and the smectite increased in particle darkness, lateral extension, thickness, compactness and stacking order. These changes were interpreted to be a consequence of sorption of ferrous Fe and reduction of FeStr, as found in previous studies on pure Fe-bearing smectites.

Core MD77-169, located in the Andaman Sea, is characterized by eNd(0) ranging between −9.5 and −11, implying that the Irrawaddy River is the main contributor of detrital material. The pedogenic clays (smectite and kaolinite) to primary mineral (feldspar, quartz, illite and chlorite) ratios show strong precessional cycles, suggesting that they are controlled by past changes in the monsoon intensity. Wet periods of summer monsoon reinforcement are characterized by the increase of chemical weathering and/or physical erosion of the Irrawaddy plain soils.

Indurated volcanic soils (tepetates) of the Mexican Altiplano display thick columnar horizons, hard laminar horizons, and grey mottles at depth. X-ray diffraction (XRD) studies show a relative enrichment in cristobalite vs. halloysite in the indurated plates of the laminar horizons and in the clay fraction of the mottles. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) studies of these two soil components have shown that they are composed of small tubes of halloysite in which numerous globular grains ∼1 μm in diameter are embedded. Based on the relative abundance of cristobalite in pedological features and on the spatial relations between successive mineral phases, we interpret the cristobalite as a transformation of halloysite with a transitional amorphous phase. In the globular grains, large platy 1:1 clay minerals undergo a progressive transformation into platy particles of opal-A and opal-C. These are in turn transformed into cristobalite without further major change in their shape and appearance, except for a higher electron density than opal and clay.

Les sols du massif d'Ona au sud de l'Equateur, à 3000 m d'altitude, formés sur des dacites du Miocène présentent des caractéristiques ferrallitiques à leurs base et andiques près de la surface. Les analyses géochimiques et minéralogiques montrent que le sol n'est pas polyphasé et qu'il s'est d'abord développé sous climat chaud à faible altitude, puis sous climat froid, en accord avec une vitesse de surrection d'environ 0,6 mm/an. (Résumé d'auteur)

This study concerns thick layers of isovolumetric transformations products developed from Miocene phonolite, in the uplands of Central Kalimantan Province (Borneo). The study of this unusual alteration material is carried out by means of chemical and thermal analysis, of X-ray diffraction and of electron microscopy. The wax-like isovolumetric alteration material shows a density close to 2.4 and a very low porosity ranging from 10 to 10 %. There are no more remains of minerals of the original rock, but the initial volume seems to be perfectly preserved. The clay material of these alterations is mainly composed of well-ordered kaolinite mixed with a small amount of 2 :1 clay minerals. Mass-balance calculation shows that the alteration material contains 40 to 60 % more AI2O3 than the same volume of the initial rock. This increase in AI2O3 is on a par with a similar increase in ГегОз and ТЮ2. For trace elements, this increase varies according to each element, ranging from 15 to 30%., Sieffermann G., Tjojudo Suharto. Evidence of mobility and input of AI, Fe, Ti and trace elements in altered volcanic rocks from Kalimantan, Indonesia. In: Proceedings of the 9th international Clay Conference, Strasbourg, 1989. Vol I : Clay-organic interactions. Clay minerals in soils. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1990. pp. 109-117. (Sciences Géologiques. Mémoire, 85)

A simple geochemical balance of lateritization processes governing the development of several tens of meters of weathering profiles overlain by ferricretes is estimated on the basis of detailed mineralogical and geochemical data. The lateritic weathering mantle of the “Haut–Mbomou” area in Central Africa is composed of different weathering layers described from the base to the top of vertical profiles as a saprolite, a mottled clay layer, a soft nodular layer, a soft ferricrete, and a ferricrete in which kaolinite, gibbsite, goethite, and hematite occur in various quantities. Incongruent dissolution of kaolinite leads to the formation of gibbsite in the upper saprolite, whereas the hematite does not clearly replace the kaolinite according to an epigene process in the upper ferruginous layers of the profiles. Instead, that kaolinite is also transformed into gibbsite according to an incongruent dissolution under hydrated and reducing conditions induced by a relatively humid climatic pattern. The respective relations of the silica, iron, and aluminum balances and the Al substitution rate of the hematite on the one hand, and of RHG [RHG = 100 (hematite/hematite + goethite)] and the kaolinite on the other hand, to the consumption or the release of protons H+ permit differentiation of aggrading ferruginization and degradation processes operating in the different lateritic weathering profiles. The Al substitution rate of the Fe–oxyhydroxides varies according to the nature of lateritization processes, e.g., saprolitic weathering and aggrading ferruginization vs. degradation. The observations and results indicate that the ferruginization process of the weathering materials of parent rocks is not a simple ongoing process as often thought. This suggests that the actual lateritic weathering mantle of the Haut–Mbomou area may result from different stages of weathering and erosion during climatic changes.