Search Results (38)

The rapid advance of urbanization and social development has intensified the complexity of engineering projects, especially where geotechnical constraints play a decisive role. Expanding cities increasingly occupy areas with challenging soil conditions, such as collapsible soils, which demand careful investigation and innovative design solutions. These geotechnical factors directly influence the safety, durability, and cost-effectiveness of infrastructure, making integrated analysis essential from the earliest stages of project planning. An experimental study with lateritic sandy soil was performed to investigate the effect of rice husk ash (RHA) on collapsible soil behavior. Collapsible soils occur worldwide in diverse geological and geotechnical conditions and can result in costly structural damage. Due to intense leaching during tropical weathering, lateritic soil structures and textures show high collapse potential, with substantial volume reduction under constant stress when wetted. The investigated soil was collected in a tropical area of the Paraná Basin (Brazil) and is considered representative of large regions with similar geological conditions. Soil samples and mixtures (2, 4, 6, 8, 10, 12, and 14 wt.% RHA) were tested using standard geotechnical procedures such as grain size distribution and compaction tests. Collapsibility behavior (i.e., collapse potential, CP) was measured using oedometer tests. Tests were conducted with realistic compaction degrees (~80%), representing conditions found in nature and in civil works involving collapsible soils. The results show that RHA can considerably reduce the collapse potential of lateritic fine sandy soils, mainly due to its packing effect, which reduces volumetric changes with increased moisture. The CP was significantly reduced from 9.83% to 1.93% in the mixture containing 14% RHA. Full article

The principal global sources of platinum-group elements (Os, Ir, Ru, Rh, Pt, Pd), collectively referred to as PGEs, are magmatic Ni-Cu sulfide deposits associated with large, layered intrusions, such as the Bushveld Complex. Recent exploration efforts have identified rock types with elevated PGE concentrations, although their potential remains uncertain. This comprehensive review synthesizes the current knowledge regarding potential sources from both natural magmatic and anthropogenic activities, as well as the environmental risks associated with the Pt, Pd, and Rh sub-group, or PPGEs. The order of Pd > Pt > Rh content in emitted particulates has been documented in dust and soil along roadsides, whereas in Fe-Ni laterite, Pt tends to accumulate residually at the top of profiles due to the higher mobility of Pd compared to Pt and Rh. The greater mobility and transfer of Pd are evidenced by higher bioaccumulation factors for Pd in plants and crops, with a higher Pd content observed in roots than in shoots. The effects of chronic occupational exposure to Pt compounds, such as allergic reactions affecting the skin and respiratory system of workers, are well-documented. Although no established permissible limits for Pt, Pd, and Rh in soil, water, or plants exist within major regulatory frameworks, the increasing applications of PPGEs and the use of Pd in catalytic converters (due to its lower cost) underscore the need for further studies on the recycling of spent catalytic converters, health impacts, ecotoxicological assessments, and the application of current technological advances to mitigate exhaust emissions. Full article

The Otukpo Burnt Brick Factory has remained dormant for more than three decades despite repeated government interventions. In this context, the present study investigates the suitability of soils from Otukpo, Benue State, Nigeria, for unfired brick production and as supplementary cementitious materials (SCMs). Four representative samples (OT1–OT4) were subjected to X-ray fluorescence (XRF), thermogravimetric analysis (TGA), particle size distribution (PSD), X-ray diffraction (XRD), unconfined compressive strength (UCS), cube strength, shrinkage, and water absorption tests. The results revealed high reactive oxide contents (SiO₂ + Al₂O₃ + Fe₂O₃ > 93%) with low SO₃ and moderate loss on ignition (~6%), thus indicating strong pozzolanic potential. PSD residues on the 45 µm sieve ranged from 6.8 to 17%, which is well below the ASTM C618 limit of 34%. XRD confirmed quartz and kaolinite as dominant phases. Strength activity indices showed that only OT3 and OT4 exceeded Nigerian (NIS 693:2007) and Indian (IS 1725:2023) standards when stabilized with 5 wt.% cement or sodium hydroxide; while OT1 and OT2 were below these thresholds. Water absorption values for OT3 (18.69%) and OT4 (19.04%) marginally satisfied Indian standards but failed Nigerian requirements, which is reflective of high porosity. Linear shrinkage (~14%) met IS 1498 marginally, and pH values (6.14–6.34) were consistent with lateritic soils. Overall, OT3 and OT4 demonstrated promise for low-energy SCMs and unfired brick applications, though they must be restricted to non-load-bearing uses unless further stabilization is applied. Full article

As a sustainable construction material, mudbrick can be used widely in areas where common modern construction materials are not easily accessible but high clay content soil is available. The inclusion of locally available natural fibres in mudbrick could improve its mechanical and erosion resistance performance. This study examines the performance of fibre-reinforced mudbrick from spinifex and laterite soil which are abundant in Australia. The main objective of this study is to evaluate the mechanical and durability performance of spinifex fibre-reinforced mudbricks made with Australian laterite soil, focusing on the influence of fibre content, fibre length, and cement stabilisation. Spinifex fibre length (30 mm, 40 mm, 50 mm), spinifex fibre percentage (0.3%, 0.6%, 0.9%), and cement percentage (5% and 10%) are considered as the experiment variables. Results show that compressive strength generally decreases with fibre size. In this regard, specimens with 0.3% spinifex fibre, 40 mm fibre length, and 10% cement, with an average compressive strength value of 4.1 MPa, were found to have the highest strength among all design mixes. The elastic Young’s modulus was highest for the specimens with 0.3% spinifex fibre, 30 mm fibre length, and 10% cement with a 36.1 MPa. A low amount of longer fibres was found to be more effective in reducing water absorption in samples with higher cement content. Water absorption and compressive strength results suggest that, on average, 0.3–0.5% spinifex content of size 30 mm improves both low and high cement content mudbricks properties. Full article

To investigate cohesion degradation in laterite soil under dry–wet cycles—a process exhibiting intrinsic asymmetric evolution in natural systems—direct shear tests were conducted on natural and stabilized soils (guar gum/coconut fiber composites) under simulated cycles. A cohesion prediction model was developed using the gray system GM(1,1) framework, with validation confirming its applicability and reliability. Results indicate the following: (1) Stabilized soils showed significantly increased cohesion and reduced cohesion degradation rates. (2) Compared to coconut fiber-stabilized soil, guar gum-stabilized soil exhibited smaller cohesion decay magnitude and more stable internal structure. (3) Cohesion degradation in both natural and stabilized soils conformed to the GM(1,1) model, achieving >95% fitting accuracy across all groups (peak: 99.84% for natural soil). This model effectively characterizes the strength degradation process under dry–wet cycles, establishing a novel methodology for predicting cohesion in natural/stabilized laterite soils. Full article

Laterite soil is widely found in various tropical and subtropical regions. This study focuses on the physical and chemical properties of laterite soil as a precursor for geopolymer synthesis. The characteristics of the soil were determined through experimental analyses, including XRF, XRD, SEM, EDS, FTIR, TGA/DTA, and pH measurements. XRF analysis revealed that the primary chemical oxides are silica, alumina, and iron oxide, which are very essential for geopolymer production. Both XRD and FTIR assessments revealed that the calcination process applied to laterite diminishes its crystallinity while enhancing its amorphous nature, thereby improving its reactivity. TGA and DTA results confirmed significant weight loss and dihydroxylation between 400 °C and 700 °C, while temperatures above 700 °C showed minimal weight loss and no further dihydroxylation. The pH of the tested laterite soil was measured at 5.35, indicating strong acidic behaviour. Based on these combined chemical and physical analyses, this study concludes that laterite soil is a viable precursor material for geopolymer synthesis. Full article

The Mamuju region in West Sulawesi, Indonesia, is a High Background Natural Radiation Area (HBNRA) characterized by a significant enrichment of high field strength elements (HFSEs) and rare earth elements (REEs) within its lateritic deposits. This study investigates the geochemical behavior, mineralogical distribution, and enrichment processes of HFSEs and REEs in lateritic profiles of drill cores and surface samples derived from alkaline volcanic rocks. The mineralogy and geochemical content of HFSEs and REEs in the alkaline bedrocks indicate its potential to become a source of lateritic enrichment. An intense lateritic weathering process leads to the residual accumulation of HFSEs and REEs, particularly in B-horizon soils, where clay minerals and Fe–Al oxides are crucial in element precipitation. Moreover, groundwater redox conditions are a key factor for uranium precipitation in the lateritic profile. The findings provide insight into the potential of lateritic weathering as a natural mechanism for HFSE and REE concentration, contributing to the broader understanding of critical metal resources in Indonesia. These insights have implications for sustainable resource exploration and environmental management in areas with high natural radiation exposure. Full article

In the framework of lateritic material valorization, we demonstrated how the geological environment determines the mineralogical characterizations of two laterite samples, KN and LA. KN and LA originate from the Birimian and Precambrian environments, respectively. We showed that the geological criterion alone does not determine the applicability of these laterites as potential adsorbents but must be associated with their physicochemical properties. The characterizations were carried out using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermal analysis, and Atomic Emission Spectrometry Coupled with an Inductive Plasma Source. The major mineral phases obtained by X-ray diffraction analysis coupled with infrared analysis showed that the KN and LA laterite samples were composed of quartz (33.58% to 45.77%), kaolinite (35.64% to 17.05%), hematite (13.36% to 11.43%), and goethite (7.44% to 6.31%). The anionic exchange capacity of the KN and LA laterites ranged from 86.50 ± 3.40 to 73.91 ± 9.94 cmol(-)·kg⁻¹ and from 73.59 ± 3.02 to 64.56 ± 4.08 cmol(-)·kg⁻¹, respectively, and the cation exchange capacity values are in the order of 52.3 ± 2.3 and 58.7 ± 3.4 cmol(+)/Kg for the KN and LA samples, respectively. The specific surface values determined by the BET method were 58.65 m²/g and 41.15 m²/g for the KN and LA samples, respectively. The effects of adsorbent doses on As(III,V), Pb(II), and Cu(II) adsorption were studied. At 5 mg/L As and 15 g/L adsorbent (pH 6.5–7), arsenate removal was 99.72 ± 0.35% and 99.58 ± 0.45% for KN and LA, respectively, whereas arsenite removal reached 83.52 ± 2.21% and 98.59 ± 0.64% for LA and KN, respectively. The Pb(II) and Cu(II) removal rates were 74.20 ± 0.95% for 2.4 g/L KN and 54.18 ± 0.01% for 8 g/L KN, respectively. Based on their physicochemical and mineralogical characteristics, the KN and LA laterite samples were shown to possess a high potential as adsorbent material candidates for removing heavy metals and/or anionic species from groundwater. Full article

Bacterial leaching is a well-known green technology proposed for the extraction of valuable metals into solution. However, this biotechnology has some “bottle neck” problems too. Arsenopyrite, a gold-bearing ore, is a refractory mineral material that is hardly soluble and contains toxic arsenic compounds which decrease any bioleaching production. The most common biotechnology used for this process is provided with the species Acidithiobacillus ferrooxidans: autotrophic and acidophilic bacterial strains including ones resistant to inorganic arsenic compounds. Common attempts to dissolve arsenopyrite with increasing volumes of sulfuric acid provoke acidification of the environment and its pollution with toxic compounds. In our research, we compared two A. ferrooxidans strains of different origin: TFBk isolated from arsenopyrite ore (pre-adopted to arsenic), the Republic of Kazakhstan, and ShA-GNK isolated from silicate nickel-ferrous ore (laterite, without arsenic), the Russian Federation. The studied genomes of both strains showed the presence of the same genes providing defense against arsenic compounds, but the resistance to toxic compounds was higher in the strain that had never been exposed to any high As concentration under the natural conditions. Both strains showed a weak oxidation of the arsenopyrite flotation concentrate (AFC). In accordance with the published data, supplementation of the medium with formate stimulated bacterial growth in the culturing medium. However, this supplementation to the leaching solution decreased the arsenopyrite oxidation during the first stage of the AFC leaching because formate was used as an alternative energy substrate, but subsequently gave a higher iron yield later. Full article

With the booming of renewable clean energies towards reducing carbon emission, demands for lithium-ion batteries (LIBs) in applications to transportation vehicles and power stations are increasing exponentially. As a consequence, great pressures have been posed on the technological development and production of valuable elements key to LIBs, in addition to concerns about depletion of natural resources, environmental impacts, and management of waste batteries. In this paper, we compile recent information on lithium, nickel, and cobalt, the three most crucial elements utilized in LIBs, in terms of demands, current identified terrestrial resources, extraction technologies from primary natural resources and waste. Most nickel and cobalt are currently produced from high-grade sulfide ores via a pyrometallurgical approach. Increased demands have stimulated production of Ni and Co from low-grade laterites, which is commonly performed through the hydrometallurgical process. Most lithium exists in brines and is extracted via evaporation–precipitation in common industrial practice. It is noteworthy that at present, the pyrometallurgical process is energy-intensive and polluting in terms of gas emissions. Hydrometallurgical processes utilize large amounts of alkaline or acidic media in combination with reducing agents, generating hazardous waste streams. Traditional evaporation–precipitation consumes time, water, and land. Extraction of these elements from deep seas and recycling from waste are emerging as technologies. Advanced energy-saving and environmentally friendly processes are under extensive research and development and are crucial in the process of renewable clean energy implementation. Full article

A very common hazard in Rwanda is represented by the instability of steep road cut slopes in lateritic soil. In its natural state, this material appears as a fine-grained weak and altered rock, generally in unsaturated conditions. Steep cut slopes made by this material could remain stable for a long time unless weathering weakens its mechanical behavior and heavy rainfall provokes a rapid landslide. This paper presents the results of an experimental investigation on the microstructural, petrophysical, and geotechnical properties of lateritic soil from a road cut slope located in Kabaya (Ngororero District—Rwanda), which was recently subjected to a landslide. The mechanical properties of the material are strictly related to the geological origin and history of the deposits, their formation environment, and weathering processes. These characteristics were revealed by peculiar microstructural features (micro-texture, porosity, and degree of alteration of original mineral paragenesis). The experimental investigations included identification and classification tests, direct shear tests on saturated samples, and swelling tests. This multidisciplinary approach provided insights into the relationship between geotechnical properties and the microstructural, petrophysical, and chemical characteristics of the altered rocks. This study showed how different levels of chemical alteration operated by weathering processes, in conjunction with brittle deformation related to the tectonic history, formed in the same site two shallow rock layers with similar macro-scale features and mechanical behaviors but markedly different microstructural and chemical properties. The innovative aspect of this research suggests an integrated multidisciplinary approach to considering microstructural aspects in addition to mechanical behavior in the slope stability analyses in lateritic soil. In particular, this study demonstrates the importance of such an approach since the failure mechanism is better explained if it is based on microstructural observations instead of considering the soil shear strength parameters only. This research helped to explain the formation of the landslide failure mechanism in a specific road cut slope, which could be assumed as representative of many other similar slopes subjected to landslides in Rwanda. Full article

This study assesses the usability of natural materials available in Australia’s remote communities for making fibre-reinforced mudbricks. The present construction cost for housing in remote areas is too high to maintain the level of housing required for the remote Australian population. As this includes mostly First Nations communities, more culturally appropriate housing materials and construction methods are being considered. This study looks at mudbricks made from laterite soil reinforced by spinifex fibre, both available in abundance in remote communities. Hence, this material is more acceptable to communities as it is more sustainable, and the construction methods are more suited for First Nations engagement. Various mixes were tested for compressive strength and erosion resistance. Results suggest that spinifex can significantly improve compressive strength and reduce erosion effects; however, spinifex showed adverse effects at the early stage of the spray test. The results satisfy the minimum strength and erosion resistance requirements for construction and suggest that spinifex-reinforced mudbricks could potentially be considered as an alternative material in remote housing. Full article

Natural laterite fixed-bed columns intercalated with two types of layers (inert materials, such as fine sand and gravel, and adsorbent materials, such as activated carbon prepared from Balanites aegyptiaca (BA-AC)) were used for As(III) removal from an aqueous solution. Investigations were carried out to solve the problem of column clogging, which appears during the percolation of water through a natural laterite fixed-bed column. Experimental tests were conducted to evaluate the hydraulic conductivities of several fixed-bed column configurations and the effects of various parameters, such as the grain size, bed height, and initial As(III) concentration. The permeability data show that, among the different types of fixed-bed columns investigated, the one filled with repeating layers of laterite and activated carbon is more suitable for As(III) adsorption, in terms of performance and cost, than the others (i.e., non-intercalated laterite; non-intercalated activated carbon, repeating layers of laterite and fine sand; and repeating layers of laterite and gravel). A study was carried out to determine the most efficient column using breakthrough curves. The breakthrough increased from 15 to 85 h with an increase in the bed height from 20 to 40 cm and decreased from 247 to 32 h with an increase in the initial As(III) concentration from 0.5 to 2 mg/L. The Bohart–Adams model results show that increasing the bed height induced a decrease in the k_AB and N₀ values. The critical bed depths determined using the bed depth service time (BDST) model for As(III) removal were 15.23 and 7.98 cm for 1 and 20% breakthroughs, respectively. The results show that the new low-cost adsorptive porous system based on laterite layers with alternating BA-AC layers can be used for the treatment of arsenic-contaminated water. Full article

Soil concrete is a material produced by mixing the soil at the site with a hydraulic binder. This paper aims to study the influence of the nature of binder on the physical and mechanical properties of soil concrete. For the mixtures, three types of soil were chosen and studied: sandy clay with a granular class of 0/5 (SA5), laterite with a granular class of 0/5 (LA5), and laterite with a granular class of 0/10 (LA10). Three different cements were used: CEM I 52.5, CEM II 42.5, and CEM III 32.5, with cement contents of 150 and 250 kg/m³. The soil concretes were designed for a constant spread of 32–33 cm measured on a mini-slump. The results showed that LA5-based soil concrete has a higher water content of about 8.8% more than SA5 and LA10-based soil concretes. For all the mixtures, the lowest porosity values were obtained with CEM III 32.5, followed by CEM I 52.5, and finally CEM II 42.5. For the three types of cement and the same soil granular size, the compressive strength, static, and dynamic modulus of SA5-based soil concretes are higher than LA5. It was noted that the mechanical properties of soil concretes made with CEM III 32.5 are higher than those made with CEM I 52.5 and CEM II 42.5. Regardless of the type of cement used, the mechanical properties obtained on LA10-based soil concrete are higher than those on LA5-based soil concrete. Full article

Spatiotemporal assessment and a comprehensive understanding of cropland sustainability are prerequisites for ensuring food security and promoting sustainable development. However, a remote sensing-based approach framework that is suitable for large-scale and high-precision assessment and can reflect the overall sustainability of cropland has not yet been developed. This study considered a typical lateritic red soil region of Guangdong Province, China, as an example. Cropland sustainability was examined from three aspects: natural capacity, management level, and food productivity. Ten typical indicators, including soil organic matter, pH, irrigation guarantee capability, multiple cropping index, and food productivity, among others, were constructed using remote sensing technology and selected to represent these three aspects. Based on the indicator system, we assessed the spatiotemporal patterns of cropland sustainability from 2010 to 2020. The results showed that the natural capacity, management level, and food productivity of cropland had improved over the 10 years. The cropland sustainability score increased from 67.95 to 69.08 over this period. The sustainability scores for 68.64% of cropland were increased and were largely distributed in the eastern and western region of the study area. The croplands with declining sustainability scores were mostly distributed in the central region. The prefecture-level regions differed in cropland sustainability, with Zhongshan, Zhuhai, and Qingyuan cities exhibiting the highest values, and Zhanjiang the lowest. Exploring the underlying mechanisms of cropland sustainability and proposing improvement measures can guide decision-making, cropland protection, and efficient utilization, especially in similar lateritic red soil regions of the world. Full article