Clay Minerals Mapping from Imaging Spectroscopy

Mapping subsurface clay minerals is an important issue because they have particular behaviors in terms of mechanics and hydrology that directly affects assets laid at the surface such as buildings, houses, etc. They have a direct impact in ground stability due to their swelling capacities, constraining infiltration processes during flooding, especially when moisture is important. So detecting and characterizing clay mineral in soils serve urban planning issues and improve the risk reduction by predicting impacts of subsidence on houses and infrastructures. High-resolution clay maps are thus needed with accurate indications on mineral species and abundances. Clay minerals, known as phyllosilicates, are divided in three main species: smectite, illite, and kaolinite. The smectite group highly contributes to the swelling behavior of soils, and because geotechnical soil analyses are expensive and time-consuming, it is urgent to develop new approaches for mapping clays’ spatial distribution by using new technologies, e.g., ground spectrometer or remote hyperspectral cameras [0.4–2.5 μm]. These technics constitute efficient alternatives to conventional methods. We present in this chapter some recent results we got for characterizing clay species and their abundances from spectrometry, used either from a ground spectrometer or from hyperspectral cameras

The efficacy of lignosulfonate in controlling the swell potential of expansive soil and its stabilization mechanisms

Many techniques have been developed and applied to prevent and/or remediate infrastructural damage caused by expansive soils throughout the world. Of these techniques, traditional chemical (lime and cement) stabilization has gained world attention because of a good understanding of the underlying mechanisms, availability of technical guidelines, and years of demonstrated field experiences. However, despite the global acceptance of traditional additives for treating expansive soil, other environmentally benign alternatives have been an important subject of research due to the inherent health and safety concerns for traditional admixtures. One such alternative is from the paper industry that manufactures pulp from wood and in the process produces over 50 million tons annually of a waste substance known as lignosulfonate (LS). This substance has been disposed of as a waste product resulting in colossal disposal cost; however, it does have a potential application in geotechnical engineering under the concept of sustainable development. This investigation into LS admixture consists of experimental and theoretical studies. The experimental investigation involved a laboratory evaluation of the efficacy of LS admixture in controlling the swell potential of a remoulded expansive soil. The swell potential was examined in terms of percent swell and swell pressure of the soil. In addition to these engineering properties, the Atterberg limits, unconfined compressive strength, durability (wet/dry and freeze/thaw), compaction characteristics, permeability, consolidation characteristics, and shrinkage behaviours were also investigated. Furthermore, the mechanism by which the remoulded soil was modified or altered by the LS admixture was probed and identified. The optimum content of LS admixture was found to be about 2% by dry weight of the soil. Standard geotechnical laboratory tests performed on untreated and treated compacted soil specimens showed significant and consistent changes in the swell potential and other engineering properties such that the percent swell decreased by 22% while maintaining the soil’s pH. In some instances, identical specimens treated with 2% cement were prepared and tested for comparison. Although the specimens treated with cement recorded a 33% reduction in the percent swell, the ductile characteristics were replaced by brittleness and a significant increase in pH. Further analysis of the laboratory test data also suggested that LS admixture is a resourceful alternative for “low” swelling soils. This finding led to the formation of a “LS application chart” that will help geotechnical practitioners on admixture choice for a particular expansive soil deposits. The physical-chemical analyses of untreated and 2% LS treated specimens were studied microstructurally after 7 days of curing. When LS was added into expansive soil, the stabilization mechanisms consisted of an insignificant exchange of interlayer cations due to the “cover-up-effect”, basal/peripheral adsorption on mineral surfaces through hydrogen bonding (water bridging), direct bonding to dehydrated cations with the subsequent formation of flocculation-aggregates, initial expansion of diffuse double layer and water entrapment, and a waterproofing effect. An elemental analysis of untreated and treated specimens suggested inter-molecular interactions between soil minerals and the LS admixture as opposed to major chemical reactions. Thus, LS summarily altered the crystallographic characteristics of the soil minerals, and helped to reduce shrink-swell behaviour of the otherwise expansive soil. The theoretical aspect of this research work involved the development of a robust mathematical model to predict the swell behaviour of expansive soil treated with LS. Relationships were proposed to estimate the suction behaviour of treated soil using laboratory data obtained experimentally. Suction behaviour was governed by a single constant (β), which depends on an input variable; the degree of saturation (Sd). A reasonable correlation was found between the percent swell determined experimentally and the predicted values. A non-traditional admixture such as LS has the potential to become a technically and economically competitive alternative in the stabilization of expansive soils. With over 50 million tons being produced annually, the successful use of LS admixture as a new stabilization material for expansive soil appears to be one of many viable solutions to the sustainable use of a waste by-product, green construction, and as well as saving the disposal problems inherent in the paper manufacturing industry

An experimental study on micro-structural and geotechnical characteristics of expansive clay mixed with EPS granules

© 2020 Pavement structures constructed on the expansive soil subgrade experience a higher upward pressure compared to any other subgrade material. The upward pressure is caused due to high swelling and shrinkage characteristics of expansive clay soil. The present study has investigated and identified the mechanisms by which a remolded expansive soil can be modified to reduce the upward pressure and swelling (heave). To achieve this, a lightweight, environmentally friendly, and high pressure resistive expanded polystyrene (EPS) granules have been used with expansive soil s from three different locations of Madhya Pradesh state, India. The study has been performed to understand the swelling and strength characteristics of soil with and without the use of EPS (density = 21.6 kg/m3) as per ASTM specifications. The chemical and microstructural components of the expansive soil were investigated using autotuned total reflectance Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Several laboratory experiments, including optimum moisture content, maximum dry unit weight, grain-size distribution, liquid limit, plastic limit, shrinkage limit, free swell index, unconfined compressive strength, and pressure swelling tests were carried out on the statically compacted expansive clay soil specimen with and without EPS (0.25%, 0.50%, 1.00%). The maximum addition of EPS was considered as 1% as the very high expansion was observed, and beyond this, further addition of EPS was not feasible. The results show that the swelling pressure, expansion percentage, and time rate of swell decrease, whereas the unconfined compressive strength (UCS) increases with the addition of EPS. The inclusion of EPS in expansive clay soil exponentially reduced the heave and the upward pressure, whereas the maximum UCS was observed at 0.5%

Swelling potential reduction of Spanish argillaceous marlstone Facies Tap soil through the addition of crumb rubber particles from scrap tyres

[EN] During construction of road and railway projects, expansive soils may be encountered. Their use as construction material for embankments presents difficulties, due to their tendency to swell or shrink. Traditional solutions include mixing soil with cement or quicklime, or to import materials from other locations. As an alternative to these solutions, the present paper proposes a less expensive and more sustainable solution, consisting in mixing the natural expansive soil with rubber particles obtained from scrap tyres. Especially, the Facies Tap (a typical soil of southeastern Spain) is studied in this paper. This soil, which is mainly a white argillaceous marlstone, is mixed with six different amounts of rubber content (2.5, 5, 10, 15, 20 and 25% in terms of weight) and submitted to several geotechnical tests, including compaction, free swelling, unidimensional consolidation, direct shear testing and undrained shear compression. The addition of rubber particles to the soil up to a 15% makes it lighter and less prone to swelling, while compressibility remains similar to the natural soil and the drained shear strength slightly increases. Based on experimental results, the optimum rubber content mixed with the soil to prevent its swelling is established at around 3%.Hidalgo Signes, C.; Garzón-Roca, J.; Martínez Fernández, P.; Garrido De La Torre, ME.; Insa Franco, R. (2016). Swelling potential reduction of Spanish argillaceous marlstone Facies Tap soil through the addition of crumb rubber particles from scrap tyres. Applied Clay Science. 132-133:768-773. doi:10.1016/j.clay.2016.07.027S768773132-13

Long-term comparison between waste paper fly ash and traditional binder as hydraulic road binder exposed to sulfate concentrations

Sulfate attack is one of the drawbacks of cementitious materials for stabilized soils. In the current study, a durability comparison of stabilized soil with cement (Type IV) and waste paper fly ash (WPFA) was conducted. First, the treated soil’s unconfined compressive strength (UCS) was tested. Next, the treated soil was subjected to various wetting/drying cycles with various sulfate concentrations and temperatures for a year. In the meantime, samples were taken for DRX, FTIR, and TGA microstructural analyses. Additionally, samples were manufactured to track swelling over an 800 day period. The outcomes show that WPFA’s UCS remained constant. Furthermore, ettringite development can be seen in the microstructural studies, however testing on linear displacement over 800 days revealed no significant changes in swelling. Finally, SEM was used to verify the ettringite formation at 360 days in order to confirm the previous findings. All the results indicated that stabilizing soil with 5% of WPFA and 3% of cement IV is possible even in presence of high sulfate concentrations, while maintaining the durability of the structure.This research was funded by European Union’s Horizon 2020, grant number 730305.Peer ReviewedPostprint (published version

Subsurface Characterization of Flexible Pavements Constructed Over Expansive Soil Subgrades and Selection of Suitable Rehabilitation Alternatives

Expansive soils present significant engineering challenges, with annual costs associated with repairing structures constructed over expansive soils estimated to run into several billion dollars. Volume changes in expansive soil deposits induced by fluctuations in the moisture content can result in severe damage to overlying structures. A flexible pavement section near the Western Border of Idaho has experienced recurrent damage due to volume changes in the underlying expansive soil layer; traditional stabilization methods have provided partial success over the years. The main objective of this research effort was to characterize the problematic soil layer contributing to the recurrent pavement damage and propose suitable rehabilitation alternatives. An extensive laboratory test matrix was carried out to characterize soil samples collected from underneath the problematic pavement section. Laboratory tests showed that the problematic expansive soil deposit was often at depths greater than 6 ft. (183 cm) from the pavement surface. Potential Vertical Rise (PVR) values calculated for ten boreholes strategically placed along the problematic pavement section closely matched with the surface roughness profile observed in the field. Liquidity Index (LI) calculations indicated that the active-zone extended to a depth of least 11 ft. (335 cm) from the pavement surface, and therefore, most of the heaving likely originates from soil layers as deep as 11 ft. (335 cm) from the pavement surface. Clay mineralogy tests indicated the presence of high amounts of Montmorillonite that can lead to significant volume changes. Moreover, high sulfate contents were detected in soil samples obtained from several of the boreholes, indicating a potential for sulfate-induced heaving upon chemical stabilization using calcium-based stabilizers. Based on findings from the laboratory testing, it was concluded that chemical stabilization or shallow treatment alternatives are not likely to be successful in mitigating the recurrent differential heave problems. A mechanical stabilization approach using geocells was proposed as a likely rehabilitation alternative for this pavement section. By dissipating the heave-induced stresses over a wider area, this reinforcement configuration was hypothesized to significantly reduce the differential heave. Finite-element models of the pavement section comprising six alternative geocell-reinforced configurations were prepared using the commercially available package, ABAQUS®. Moisture swelling and suction properties for the expansive soil deposit were established in the laboratory and were used in the numerical model to simulate the swelling behavior. Results from the numerical modeling effort established that placing two layers of geocell within the unbound granular base layer led to the highest reduction (~60%) in the differential heave. Placing a single layer of geocell, on the other hand, reduced the differential heave magnitude by approximately 50%. A single layer of geocell was therefore recommended for implementation to achieve the optimal balance between pavement performance and construction costs

Combining visible near-infrared spectroscopy and water vapor sorption for soil specific surface area estimation

Abstract The soil specific surface area (SSA) is a fundamental property governing a range of soil processes relevant to engineering, environmental, and agricultural applications. A method for SSA determination based on a combination of visible near‐infrared spectroscopy (vis‐NIRS) and vapor sorption isotherm measurements was proposed. Two models for water vapor sorption isotherms (WSIs) were used: the Tuller–Or (TO) and the Guggenheim–Anderson–de Boer (GAB) model. They were parameterized with sorption isotherm measurements and applied for SSA estimation for a wide range of soils (N = 270) from 27 countries. The generated vis‐NIRS models were compared with models where the SSA was determined with the ethylene glycol monoethyl ether (EGME) method. Different regression techniques were tested and included partial least squares (PLS), support vector machines (SVM), and artificial neural networks (ANN). The effect of dataset subdivision based on EGME values on model performance was also tested. Successful calibration models for SSATO and SSAGAB were generated and were nearly identical to that of SSAEGME. The performance of models was dependent on the range and variation in SSA values. However, the comparison using selected validation samples indicated no significant differences in the estimated SSATO, SSAGAB, and SSAEGME, with an average standardized RMSE (SRMSE = RMSE/range) of 0.07, 0.06 and 0.07, respectively. Small differences among the regression techniques were found, yet SVM performed best. The results of this study indicate that the combination of vis‐NIRS with the WSI as a reference technique for vis‐NIRS models provides SSA estimations akin to the EGME method

Strength and Microstructure of a Clayey Soil Stabilized with Natural Stone Industry Waste and Lime or Cement

Industrial waste generated by the natural stone industry when working with limestone and dolostone is mainly composed of calcium carbonate and calcium magnesium carbonate. This mineral composition makes soil stabilization a potential use of the natural stone industry waste. However, much research must be carried out to fully understand the aptitude of this waste for soil improvement. In this work, the strength and microstructure of a clayey soil stabilized using limestone powder waste and lime or cement were studied employing the following techniques: unconfined compressive strength tests, mercury intrusion porosimetry, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. Moreover, the effects of an aggressive environment were simulated using a sodium sulfate solution. Its effects were investigated from 7 days to 6 months. The results obtained show an increase in the unconfined compressive strength and a more compact structure for the samples with the industrial waste. Therefore, limestone powder waste from the natural stone industry can be used as a ternary element with lime and cement in soil stabilization.This work was supported by the Spanish Ministry of Universities under project number PRX21/00554 and the University of Alicante under project number GRE17-11 and developed within the framework of the project INNVA1/2021/8 of the Agencia Valenciana de Innovación