Lateritic Materials Research Articles

Enhanced erosion and silicate weathering of the West African craton during the late Cretaceous cooling evidenced by mineralogical and Hf[sbnd]Nd isotope proxies

The evolution of oceanic temperatures between the Turonian and the K/T boundary indicates a long-term cooling coincident with a decrease of atmospheric CO2 levels, yet the cause of climate cooling at that time still remains debated. In this study, we evaluated the possible implication of enhanced silicate weathering as a sink for atmospheric CO2 by applying paired NdHf isotope measurements to detrital clay records from the West African margin. The use of this novel proxy for chemical weathering intensity (ΔɛHf(t)clay) was complemented by additional mineralogical and major-trace element analyses in order to investigate the variability of mechanical erosion patterns and further explore potential linkages between tectonics, weathering and climate during the late Cretaceous.Our ΔɛHf(t)clay data suggest more intense silicate weathering on the West African Craton during the Santonian to the middle Campanian period, coincident with enhanced physical erosional inputs as inferred from higher Quartz/Clays and Feldspar/Clays ratios. This observation suggests that the shift towards intensified chemical weathering at that time was driven by enhanced mechanical erosion, possibly related to a moderate tectonic event on the West African craton. Evidence for increasing kaolinite contents and higher ΔɛHf(t)clay values during the Maastrichtian point towards more hydrolysing conditions, inducing either destabilization of older Mesozoic lateritic material or favouring the development of kaolinite-rich soils.Overall, this study was compared with several new data of chemical weathering evolution along the south Atlantic margins, adding new insights on tectonic-weathering-climate interactions during the late Cretaceous, suggesting a possible link between silicate weathering feedbacks and global cooling at that time.

Why Do Small Earth Dams Deteriorate: Insights from Physical Investigations in the West African Sahel

In West Africa, the construction of small earth dams is common against water scarcity. Burkina Faso, an inland country in West Africa, is home to 1001 dams that serve agricultural and pastoral needs. These embankments are predominantly made of compacted laterite, a cost-effective material abundant in over 2/3 of the country. However, these dams degrade over time, hindering their functionality. This study aims to establish a catalog of typical degradation occurring on small dams in Burkina Faso, which is virtually non-existent in the region while identifying and analyzing the potential causes. The study uses a diagnostic analysis followed up with technical visits on a representative sample of 24 dams in the Centre and Centre-South regions as a basis for future studies. The results reveal that these dams were constructed between 1965 and 2018, with capacities ranging from 150,000 to 4,740,000 m3. 33% of these dams have undergone total failure, likely attributed to factors such as internal erosion, pore overpressures, settlement, and deformation. Although 67% of the dams remain functional, their structural integrity could be improved. Erosion observed in riprap indicates vulnerability during high flood periods. Additionally, the absence of proper maintenance, as shown by the vegetation development weakening embankments, contributes to deterioration. The analysis also suggests that variability in construction techniques and lateritic material properties across time and regions may further exacerbate degradation. These findings inform infrastructure improvements and policy development for sustainable water resource management in Burkina Faso and similar regions.

Multi-criteria assessment of groundwater potential of shallow aquifers in the vicinity of Osun state university, Ikire campus and environs, southwestern Nigeria

In order to investigate the groundwater potentials of shallow water-bearing layers within the vicinity of the Osun State University Campus at Ikire, fifteen vertical electrical sounding (VES) resistivity data were acquired at random. The groundwater potential of the shallow water-bearing layers was inferred from the resistivity data based on three (3) existing criteria namely aquifer resistivity, transmissivity and reflective coefficient. At each VES station, the maximum electrode spreading employed for the resistivity data acquisition was between 200 m and 240 m, with the interpretation of the data carried out using partial curve-matching and computer iterative software. Geoelectric parameters obtained were used to compute the longitudinal conductance, transverse resistance, hydraulic conductivity, transmissivity and reflective coefficient using empirical relationships. The computed parameters were compared with existing classification tables to deduce the groundwater propensity in the shallow water-bearing layers of the study area. Four to five geoelectric layers corresponding to the HQ, HA and HKA geoelectric curve types were observed having lateritic materials as topsoil, sandy clay/clayey sand, weathered/fractured basement and fresh basement. In most cases, the water-bearing layer is mostly of clayey material with high porosity and low permeability and resistivity values that varies from 14.6 Ωm in VES 1 to 65.6 Ωm in VES 6. A few consist of sandy clay also with low resistivity values 76.9 Ωm in VES 7 to 107.1 Ωm in VES 4. The transmitivity values vary from 0.239 m2/day in VES 2 to 2.522 m2/day in VES 5. This same behavior was observed with reflective coefficient values which range from 0.690 in VES 6 to 0.994 in VES 1. The conclusions from the classification tables correlate in most of the VES stations. This study shows that the groundwater potential of the shallow water-bearing layers in the study area is generally poor within 0 to 80 m depth due to the low transmissivity of the clay materials at the shallow depths. Effective groundwater development in the study area must therefore integrate geophysical methods and remote sensing techniques to investigate depths beyond 100 m.

Adsorption characteristics and mechanisms of ciprofloxacin on polyanion-modified laterite material

Adsorption characteristics and mechanisms of ciprofloxacin on polyanion-modified laterite material

Mineralogy, geochemistry, origin, and potential industrial applications of kaolin deposit from Hassi Abyad, Mauritania

The Hassi Abyad kaolin deposit is in the southern part of Mauritania, around 45 km east of the town of M'Bout. Hassi Abyad lies in the middle of the Mauritanides Shield, which consists of deformed and metamorphosed Precambrian and Paleozoic formations. Complementary geological, mineralogical, and geochemical studies have been carried out to help answer questions linked to the origin of these kaolin and to determine the potential suitability for different industrial applications. The mineralogical compositions showed that Hassi Abyad kaolin is mainly composed of kaolinite (61–96%) and other minerals such as chlorite, illite, muscovite, cronstedtite, quartz, rutile, magnetite, laumontite, and gibbsite. The average chemical composition of the kaolin samples is 35.84% Al₂O₃, 45.27% SiO₂, and 14.19% LOI. Other oxides occur in low concentrations (less than1%). The higher chemical indices of alteration CIA (99.5%) and CIW (99.6%) indicate that this kaolin deposit underwent a high degree of alteration during the process of kaolinization of the source rock. The absence of high temperature minerals such as pyrite, topaz and dickite, and the presence of high Ce + Y + La and Cr + Nb contents signifies that the development and evolution of this deposit are affiliated with supergene processes. This kaolin is derived from a lateritic material, proving that they are the source rock of this deposit. The geochemical and mineralogical characteristics indicate that Hassi Abyad kaolin is applicable in ceramics, paper, cosmetics, pharmaceutics, bricks making, and pottery.

Assessment of crushed rock aggregates addition to granular lateritic materials in sub-Saharan extensive urbanization context (Yaoundé Cameroon) for road construction purposes

Granular lateritic materials (GLM) suitability for road construction after the addition of crushed rock aggregates (CRA) in the sub-Saharan extensive urbanization context was evaluated. The urbanization rate was made by using Landsat7 and Landsat8 radar images. The studied materials were subject to petrographic description and geotechnical analysis. The urbanized surface in the Yaoundé area increased by 41.88% from 2004 to 2020. The studied rock are gneisses composed of quartz, garnet, biotite, pyroxene, and feldspars. The gneisses obtained CRA have fines content of less than 10%, maximum dry density value of more than 2.00 g/cm3, good bearing capacity (CBR = 88%), and excellent mechanical characteristics (Los Angeles < 40%). This recommend their use as base course for low to medium volume traffic pavements. Gneisses-derived GLM, less load-bearing (CBR = 39 to 42%) than CRA, have limited behaviour in road construction and can be used as sub-base for all volume traffics. Their use in base courses requires prior treatment. CRA addition to these GLM result in the plasticity index decrease and compaction parameters improvement. CBR values increase shows a perfect correlation (R2 > 0.90) with the addition of CRA. Litho-stabilised materials (CBR ≥ 60%) can be used as base course for low-volume trafficked pavements. The addition of a CRA percentage greater than or equal to 25% is efficient for the optimization of their use. By reducing the amount of quarry aggregates, the improved material could be an economical alternative for road projects. This reduces and controls the haulage of materials within crowded urban area.

Bioleaching of a lateritic ore (Piauí, Brazil) in percolators

Heap leaching of laterites for extraction of nickel and cobalt is an attractive alternative to capital and energy intensive high pressure acid leaching, the dominant hydrometallurgical processing technology for limonitic laterites. Conventional approach for heap leaching of laterites is leaching with sulfuric acid. Consumption of sulfuric acid during heap leaching is substantial and industrial-scale operations require construction of a sulfuric acid production plant on site. In this study, heap bioleaching of laterites was simulated in laboratory scale column percolators and bioleaching of nickel and cobalt from lateritic material was successfully demonstrated for the first time. The process is based on biooxidation of the bacterially modified “wet sulfur” inside column percolators by sulfur-oxidizing acidophilic bacteria Acidithiobacillus thiooxidans. The “wet sulfur“ was generated in a bioreactor with the bacterial culture, harvested, and mixed with lateritic ore before forming agglomerates to be filled in the percolator columns. Liquid was circulated with a flow rate of 8 mL/min. Maximum metal extraction was 66% nickel, 95% cobalt, 10% iron, 55% magnesium and 89% manganese from the Piauí lateritic ore after one month bioleaching. For comparison, chemical leaching with 1 M sulfuric acid with or without addition of 10 g/L of ferrous sulfate heptahydrate as reductant resulted in extraction of approximately 80% nickel, 86% cobalt, 33% iron, 50% magnesium and 81% manganese. With bioleaching a higher cobalt but lower nickel and iron extraction was achieved, i.e. a better selectivity of nickel over iron extraction, as well as a relatively higher pH of the pregnant leach solution requiring less limestone and, consequently, lower CO2 emission and generation of iron cake waste in case of laterite bioleaching. Overall, the results are promising and show potential of laterite heap bioleaching to be further developed to application on industrial scale.

REE and trace element mobility during the transformation of basalt to laterite and bauxite, Payas Province, Türkiye

The bauxites of the Payas area in the eastern Mediterranean region of Turkey occur as a stratigraphically continuous layer between Early and Late Cretaceous shallow marine carbonates. The laterites represent an in situ formation and mark a key stratigraphic layer in the region. Bauxite pockets are also present in the laterites, formed from the reworking of the laterites and accumulated in depressions in the karst terrain. Therefore, bauxite occurrences are found locally in this stratigraphic layer. The parental rock was a Ti-rich basalt that is compositionally similar to Hawaiian basalts, as indicated by petrographic features and distinctive trace element composition (Zr/TiO2 and Nb/Y). The behavior of elements during the lateritization and bauxitization processes was interpreted using the composition of the Hawaiian basalts with the iron laterite and Ti-rich bauxites of the Payas Region. During lateritization, Fe, Al, Ti, Cr, Nb, and Ta, were largely immobilie while REE and other trace elements, except for Rb, Ni, Co, and Pb were significantly removed. Approximately 75 % of the REE were removed at the end of the bauxitization and/or transportation of the lateritic soil into the karstic depressions. REE were not equally mobile with La to Ce and Lu to Yb having a relatively lower mobility than highly mobile middle REE. During the transformation of laterite to bauxite, low mobility elements such as Ti, Nb, Th, Cr, Hf, and Sn were enriched in the bauxite phase. In comparison to other elements, Rb, As, Pb, Mo, and Ni were strongly removed from the lateritic material during the bauxitization processes. The transfer of MREE during lateritization and bauxitization would have resulted in the enrichment of both light and heavy REE (concave pattern) in contemporaneous seawater. In other words, silicate weathering periods on land should be marked by a concave REE pattern with positive Eu anomaly in marine sediments throughout the geological period.

PERFORMANCE EVALUATION OF LATERITE AND PULVERIZED RECLAIMED ASPHALT PAVEMENT STABILIZED WITH BASE SEAL AND CEMENT

This research delves into the effectiveness of incorporating pulverized Reclaimed Asphalt Pavement (RAP), Base Seal, and cement to enhance the stability of lateritic base materials in Nigeria. Addressing a crucial gap in pavement engineering literature, particularly the underexplored use of base seals as liquid stabilizers, the study adopts a comprehensive methodology involving literature review, field evaluation, and laboratory tests. Analyzing various material mixes, from pure Laterite to combinations with RAP, Base Seal, and varying cement contents, the research reveals substantial improvements in crucial engineering properties. Enhanced particle size distribution, reduced clay content, and optimal compaction characteristics at 0% cement content for laterite materials with pulverized RAP signify the positive impact of these additives. California Bearing Ratio analysis establishes a consistent correlation between higher cement content and improved load-bearing capacity. Notably, the synergistic effects of RAP and base seal, particularly at 5% cement content, showcase the highest CBR value (91), indicating optimal conditions for strength and stability. The study concludes with practical recommendations for road maintenance authorities, advocating for innovative approaches like full-depth reclamation techniques and stabilized full-depth reclamation, exploring different RAP to base material ratios, examining curing periods' impact, assessing long-term performance, considering environmental implications, and conducting field trials for validation. Overall, these findings contribute valuable insights to pavement design practices, fostering the development of resilient infrastructure in construction projects.

Resilient Modulus of Compacted Granular and Lateritic Materials Used as Base Layers for Flexible Pavements in West Africa

The objective of the study is to synthesize resilient modulus data available in Senegal and to propose linear and nonlinear elasticity parameters, which can be used directly for the design of flexible pavements in west Africa. The materials tested are unbound aggregates of basalt and quartzite and gravel lateritic soil from Senegal and Burkina Faso. The Repeated Load Triaxial device is used according to French and American procedures to measure resilient modulus. Different models of the resilient modulus are used to determine the parameters of the nonlinear models and the summary and/or characteristic resilient modulus used in the elastic linear calculation. For the nonlinear calculation, the parameters of the models of Seed et al. (1967), NCHRP (2004) and Boyce (1980) are determined. For the linear elasticity calculation, at the optimum water content and at the dry density of 95% of its maximum value, a maximum modulus of between 300 and 350 MPa is proposed for laterites in the base layer. Values ​​of 220 MPa and 150 MPa are proposed for basalt and quartzite respectively. The moduli obtained are not correlated to the CBR values of the materials. A strong variability in the modulus of laterites is also noted, contrary to the modulus of unbound aggregates. Laterites sometimes have higher modulus than unbound aggregates due to cohesion, but they are more sensitive to water. We recommend that unbound materials (untreated gravels and laterites) be compacted in situ to 97% of the maximum dry density and, for laterite, to the optimal water content -1.5 but also to ensure a good waterproofing and good drainage of the structure. Keywords: Resilient modulus; unbound aggregates; gravel lateritic soil; West Africa.

Characterization of basaltic rock laterites in Dschang, West-Cameroon: Compressed Earth Bricks (CEB) for low-cost buildings

This study reports on the geotechnical characterization of lateritic soils upon basaltic rocks in Dschang, West-Cameroon. Six (06) soil samples from six (06) sites were taken for assessing their suitability in good quality CEB manufacturing. An analytical approach was adopted and consisted of standard physical and mechanical properties including water content, absolute density, Atterberg limits, grain size distribution and Optimum Proctor Modified (OPM). Mineralogical and geochemical contents of the materials were obtained by X-ray diffraction (XRD) and X-ray fluorescence (XRF) respectively. In addition, density, water absorption, abrasion resistance, and dry and wet compressive strengths were determined for manufactured brick specimens. Results indicate that the materials are rich in kaolinite (33–38%), gibbsite (21–27%) and goethite (22–26%) associated to low proportions of smectites (2–7%) and oxides such as hematite, ilmenite, anatase and bohmite. SiO2 (29.57–35.8%), Al2O3 (22.72–26.93%) and Fe2O3 (20.67–27.95%) are the most abundant oxides while basic cations are generally low in the materials (WIP: 2.25–5.89). The absolute density varies from 2.26 to 2.57 t/m3 and could be indicative of higher Fe2O3 contents. The plasticity index (7.80–18.95%) and the liquidity limit (57.80–64.50%) of materials allow their classification as inorganic silt and organic clay with high plasticity and compressibility that are not suitable for the production of CEB. Furthermore, these materials fall out the preferential plasticity domain recommended by Cameroonian standard for CEB. Based on grain size distribution, the studied materials also fall out the sprindle reference of the Cameroonian standard. For improving the characteristics of studied materials, a grain size correction was performed and provided an optimal mixture made up of 75% natural materials and 25% medium sand (0.05–0.5 mm) that is locally available. This is accompanied by considerable variations of consistency parameters allowing to pass from inorganic silt and organic clay to inorganic clay that display appropriate compressibility and plasticity for good quality CEB production. The using of cement at 4%, 6% and 8% revealed a progressive increase of the MDD (1.40–1.77%) and Wopt (12.60–28.39%). Moreover, the density and mechanical parameters of the manufactured specimens increase with the cement content. The density, physical and mechanical properties of the manufactured specimens fall within the Cameroonian standard of compressed earth bricks (CEB). Globally, the lateritic materials of Dschang improved with sand (25%) and Cement (8%) can be suitable for the production of good and low-cost CEB especially as the two additional materials are locally available and accessible.

Ultisols with Unique Soil Properties and their Implications in Carbon Enhancement Strategies for Indian Tropical Soils

Million years old Ultisols, developed as an end stage of advance soil weathering on base-poor rock systems under forest and plantation crops of the Indian sub-continent, are enriched with organic carbon (OC). Despite their remarkable acid chemical reaction, they show an upward increase in extractable bases (EB) and base saturation (BS) in the pedon, and on some occasion BS &gt; 35% in surface horizons. Recent research suggests that the litter falls from forest species provide bases on soil surface, which causes similar depth distribution of EB and BS in Andisols of Nilgiri Hills of humid tropical southern India, developed on pre-weathered lateritic materials consisting primarily of Fe and Al oxides/ hydroxides. Under similar humid tropical (HT) climate in protected rain forest, million years old OC rich soils of Andaman and Nicobar Islands, developed on base-poor rock systems, have similar chemical and clay mineralogical properties of Ultisols except however their EB and BS, which are more than 10% and much above 50%, respectively and therefore, they are acidic Alfisols. Formation of Alfisols on the Island is a unique example on the formidable role of vegetation in soil formation, suggesting that if inland Ultisols are kept under natural protected forest ecosystem, they may phase towards Alfisols thereby facilitating OC sequestration and perform other ecosystem functions. The preservation of natural or semi-natural ecosystems is thus essential to raise the OC stocks of soils, which would help to gain various ecological benefits.

Mineralogy and geochemistry of the Morro do Engenho lateritic nickel deposit, Goiás Alkaline Province, Brazil

The Morro do Engenho lateritic nickel deposit results from the action of weathering processes on the alkaline mafic-ultramafic rocks that make up the Cretaceous zoned intrusive body belonging to the Goiás Alkaline Province. Historically, the deposit is classified as a silicate one, and mineralization is present especially in phyllosilicates such as serpentine and chlorite. By identifying Ni-bearing phases and providing the lithogeochemical characterization of weathering profiles, this study aims to provide further insights into the metallogenetic processes and controls acting on the mineralization of the Morro do Engenho lateritic Ni deposit. The following methods were used: petrographic studies, SEM-EDS, XRD and lithogeochemical characterization of the weathering profiles developed on each of the parent rocks that make up the body. The Morro do Engenho intrusive massif is formed by a dunite core, surrounded by a peridotite/pyroxenite zone, an alkaline gabbro zone and more externally by a syenite-nepheline zone. The lateritic profile constitutes eight weathering horizons, stacked one upon another from the bedrock namely: (i) saprock, (ii) lower saprolite, (iii) ferruginous saprolite, (iv) ocher saprolite, (v) plasma zone, (vi) lateritic duriccrust, (vii) silcrete and (viii) topsoil. Most Ni mineralization occurs in the lower saprolite, ferruginous saprolite and ocher saprolite zones. The findings pointed to the presence of Ni in silicate mineral phases, represented by serpentine, chlorite, smectite, as well as in Fe and Mn oxyhydroxides. The depressed area, located between the two major topographic elevations, has the highest Ni enrichments, which according to mass balance calculations can account for up to 40%. Hydrodynamic factors, by dissolution/precipitation of silicates in saprolite horizons of dunite core, are suggested as possible agents in the remobilization of Ni, among other mobile elements, to topographically flat zones. The geometry of the Morro do Engenho deposit show that lateral redistribution by hydrodynamic factors could also account for the mineralization of areas peripheral to the dunite core, composed of pyroxenite and gabbro-derived lateritic profiles. The direction of regional groundwater flow, strongly influenced by topography, would also be an important factor in the remobilization of Ni, as well as the mechanical transport of lateritic materials. Silicate mineralization predominates in the Morro do Engenho deposit, concentrated in Mg hydrosilicates and clay minerals; oxide mineralization also occurs, mostly in Fe and Mn oxyhydroxides. The findings discussed in this paper can broaden the understanding of metallogenetic processes involved in the genesis of lateritic nickel deposits. .

Mechanical Behavior of Hydrated-Lime–Liquid-Stabilizer-Treated Granular Lateritic Soils

Granular lateritic soil is commonly used for road construction in humid tropical and subtropical regions. However, the high plastic clay content and poor particle distribution of some laterite materials make them unsuitable for bases and subbases. Lime treatment is a widely used method for improving problematic lateritic soil, and liquid ionic stabilizers are considered an environmentally friendly solution for reinforcing such soils. However, using only lime or only stabilizers may not be optimal. This study investigated the effect of treating granular lateritic soil with hydrated lime and a new liquid stabilizer, Zhonglu-2A (ZL-2A). A series of indoor tests, including compaction, California bearing ratio, and unconfined compressive strength tests, were conducted to evaluate the effects of hydrated lime content and stabilizer content on the mechanical properties, mineralogical composition, and microstructure of the soil. The results show that an increase in hydrated lime dosage increases the optimal moisture content and decreases the maximum dry density. The CBR of lime-stabilizer-treated laterite was at least 2–3 times higher than that of the only-lime-treated soil. The highest CBR was observed in samples treated with 0.2‰ ZL-2A stabilizer. The sample with 6% lime and 0.2‰ ZL-2A stabilizer exhibited the highest unconfined compressive strength, and a nearly linear increase was observed between the unconfined compressive strength and CBR. Further investigation of the stabilization mechanism using X-ray diffraction mineralogy analysis and scanning electron microscopy revealed that the inorganic substances of the ZL-2A stabilizer and the hydrated lime provided the basic conditions for the reaction and generated cementitious hydrates on the clay particles. The mixture of granular lateritic soil and hydrated lime was wrapped by the ZL-2A stabilizer, forming a complex spatial structure and improving the strength of the soil. To improve the bearing capacity of subgrades in actual subgrade engineering, a combination of a liquid ionic stabilizer and lime should be used to treat laterite.

EVALUATION OF THE COMPRESSIVE STRENGTH AND WATER RESISTING CAPACITIES OF LIME STABILIZED SOIL BLOCKS FOR BUILDING CLIMATE RESILIENT STRUCTURES

The compressive strength and water resisting capacities of lime stabilised soil blocks for use in building climate resilient structures were evaluated. Good laterite material, lime of suitable chemical composition and potable water were used for mixing. Six (6) different mix proportions of soil-blocks were produced i.e., 2%, 4%, 6%, 8%, 10% and 12% lime content in laterite. The dry compressive and wet compressive strengths tests for the blocks produced were measured after the period of 1, 3, 7, 14 and 28 days. Results showed that the 2% lime has an average dry compressive strength ranging between 0.17 to 0.67 N/mm2 and no wet compressive strength was recorded due to the dissolution of the blocks in water after first day of immersion and 4% lime has an average dry compressive strength ranging from 0.71 to 1.24N/mm2 and wet compressive strength ranging from 0.76 to 0.49N/mm2 from day 1 to day 3, while day 7, 14 and 28 dissolved in water. The 6% lime has an average dry compressive strength ranging between 0.58 to 1.96 N/mm2 and wet compressive strength of 0.67 to 1.47 N/mm2. A decrease in average dry and wet compressive strengths was observed for 8%, 10% and 12% lime contents. Therefore, the 6% lime-soil mix ratio gave the highest compressive strength of 1.96 N/mm2 above the weakest average strength of 1.70 N/mm2, specified by the Federal Ministry of Works and Housing, and minimum requirements of 1.75N/mm2 by the Nigerian National Building Code.&#x0D;

Application of 2-D imaging survey for ascertaining the cause(s) of road failures along Sapele/Agbor road in Delta State, Nigeria

Surveying involving 2-D imaging dipole–dipole geophysical technique was carried out along Sapele-Agbor Highway situated in Southern, Nigeria to determine the primary causes for Highway pavement failure. Twelve profiles spreading over 100 meters were in each cases conducted on road surface sections along the stable (control) and unstable portions of the road. Data were gathered together along the various profile employing ABEM Terra meter SAS 1000. The field data were processed and inverted utilizing Dipro software. This was done by specifying and locating the geoelectric arrangement within the surface, sub-base and sub grade soil to obtain the confirming cause(s) of the road associated with pavement failure. Geoelectric sections identified four geologic layers embracing the topsoil, clayey, laterite and sand. The sections failure is due to disparity of the material used for road model (construction) as some comprises of clay materials. The results show the presence of low resistivity values at several subdivisions of the 12 profiles. Resistivity values varying from 21.60 Ωm – 1026.0 Ωm to a depth of 14.92 m from the surface was observed along Okpara Water side, Aghalokpe and Otumara. In Igun, Eku and Obiaruku resistivity values ranges from 10.5 Ωm – 500.0 Ωm to a depth of 5.5 m from the topsoil, 22 m from sub grade and 9.8 m - 50 m were observed along the four profiles. Urhomehe, Urhonigbe, Abavo and Agbor indicate resistivity ranging from 59.25 Ωm – 1467.50 Ωm for stable and unstable sections of the road with depth up to 15.0 m for some profiles. Low resistivity values, not greater than 199 Ωm observed in some distinctive regions of 12 profiles comprises of expansive, compressible, collapsible and sandy clay materials which have the capacity of absorbing water. These make the roads swell and collapse leading to road failure under stress and strain. Many stable portions of the road are characterized with high resistivity value greater than 199 Ωm, mostly laterite materials. Competent fill soil should replace low resistivity soil to a depth of 5 m – 7m from the surface of the road. Good drainage system is also recommended within the unstable road sections.

Relative Dielectric Permittivity Variations during Compaction as a Mean of Compaction Quality Control: Case Study on Laterite Samples from Senegal

This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.

Assessment of Lateritic Gravelled Materials for Use in Road Pavements in Cameroon

Assessment of Lateritic Gravelled Materials for Use in Road Pavements in Cameroon

Contribution to the flexible pavement design guides evaluation used in tropical zone: Application to lateritic materials of Bamougoum (West, Cameroon)

The choice of any materials in the realization of sustainable road infrastructures for the well-being of populations must be made using reliable criteria. In this work, classic geotechnical characteristics and experimental Young's modulus determination of the Bamougoum lateritic materials were put together in order to raise the non-exhaustive limits of pavement design guides used in tropical zone. The results show that the Bamougoum materials are very plastic silty materials, made up mainly of the fine fraction (33.49% and 76.41%) with plasticity indices between 9.49 and 36.88. The CBR values vary from 11 to 38 and the behavior of materials is qualified as fair to poor. For compression forces of 18.30–25.45 KN, and longitudinal deformations of 0.007–0.02, Young's modulus values varies from 72 to 221 MPa with an increase percentage less than 20 from age 3–7 days. The compliance of studied materials to road pavement standards for tropical countries and technical guides indicate that they can be used in sub-base of flexible pavements of medium or low traffic. However, relying mainly on these criteria can be misrepresentative as materials characteristics vary considerably based on laboratory test procedures, climate and parent rock not considered in the different manuals. Then, the experimental Young's modulus association with the existing classical selection criteria of material to be used in road pavement could contribute to the reduction of early roads degradation in tropical countries. Moreover, the use of pre-established modulus values has a negative impact on the infrastructure durability.

Geochemical characterization of the Sutlegen bauxite deposit, SW Antalya

Purpose.The purpose is to determine geological and geochemical characteristics of the Sutlegen (Antalya, Turkey) bauxites, to identify the elements that played a major role in their formation. Methods. X-ray diffraction (XRD) mineral phase analysis, X-ray fluorescence (XRF) elemental analysis, plasma-mass spectrometry (ICP-MS), the petrographic and mineralogical analyses, and multivariate statistical methods were used. Findings. The major element content of the ore was determined as Al2O3 (60-35.2 wt%), SiO2 (39.5-0.2 wt%), Fe2O3 (48.4-19.5 wt%), TiO2 (36.9-16 wt%), and P2O5 (0.5-0.1 wt%). The Sutlegen region, which shows epirogenetic action with the uplift of the earth's crust, is generally rich in neritic carbonates. It was revealed that the bauxite ores have undergone moderate and strong laterization as a result of the deferruginization in the environment, and they were classified into four groups as lateritic, ferritic, kaolinitic, and bauxite. The increase in the aluminosilicate minerals, which were formed during the formation of bauxite in the environment was found to be directly proportional to the laterization processes. In this context, it was considered that the lateritic material that was firstly formed in the environment filled the cavities and pores of the karst-type limestones and sedimentary units in the region by superficial transfer phenomena. The bivariate diagrams of Log Cr vs. Log Ni revealed that the bauxite that formed in the region had an ultrabasic source. Originality. In literature, no scientific studies have been found on bauxite mineralization in the Sutlegen deposits that have been operated for a long period. Practical implications. In this context, the geochemical characteristics of bauxites revealed that the source of the laterization process in the region was the ultrabasic igneous rocks. The lateritic material moved by superficial transfer was accumulated on sandstone, claystone, siltstone, and limestone and in karstic cavities; then, it formed karstic bauxite (kaolinitic and bauxite) of different classifications due to the effect of metamorphism.