The variable characteristics of weathered marl cause engineering problems, particularly in geotechnics, and require indepth studies to design structures. Where these characteristics are poor, lime is used to stabilize the soil. Experimental research is being carried out on various Tizi-Ouzou marls composed of different percentages of CaCO3. The aim is to study their behavior in the presence of quicklime and its impact on the evolution of their geotechnical characteristics to provide effective and economical solutions for stabilization. These marls are mixed with increasing percentages of lime and subjected to a series of tests in which cyclic shear is essential for simulating dynamic effects. The results obtained confirm the improvement in their geotechnical characteristics. On the one hand, interstitial pressures and cyclic deformations have decreased, thus avoiding the risk of liquefaction, subsidence, or settlement. On the other hand, cyclic stresses and resistances have increased, resulting in better resistance of these stabilized marls to dynamic stresses. Finally, the number of cycles required to reach failure has increased, thus reducing the risk of pavement damage. These results depend primarily on the percentage of CaCO3 in the marl.

Phosphate mining industry generates different types of by-products that have significant environmental impacts such as ecosystems destruction and soil contamination. To reduce their environmental footprint, these wastes were investigated as supplementary cementitious materials (SCMs). The generated by-products included a clayey material and calcareous marl which were used in the current study. Blends of the abovementioned materials with cement (ratio of 1:1) were investigated using X-Ray Fluorescence spectrometry (XRF), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TDA-TG), Mercury Porosimetry, Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Electromechanical testing device. Using these results, a learning model based on multiple linear regression (MLR) was proposed to predict the compressive strength and the specific surface area from the constituents of the material, the additives, the L/S ratio, and the hardening regime. The accuracy of the models was assessed using the correlation coefficient (R2), mean absolute error (MAE), and root mean square error (RMSE). Compressive strength results confirmed that the sample's strength improved with the amount of calcined clay. Unlike the water demand where the mixtures required more water than the OPC mixture. SEM -EDS examinations proved the existence of the C -S -H gel, responsible for the specimen strength. The used machine learning model demonstrated excellent performance and practical potential to predict both compressive strength (CS) and specific surface area (SS) by capturing both linear and nonlinear relationships. As well as time and plasticizer were the most influential factors on the properties studied (CS and SS) and their effect was positive. This sensitivity study provides important information on the critical factors influencing compressive strength and specific surface area in the different ranges considered.

Marl soil is highly prone to erosion when exposed to water flow, posing a potential threat to structural stability. The common practice of stabilizing soil involves the addition of cement and lime. However, persistent reports of severe ruptures in many stabilized soils, even after extended periods, have raised concerns. In stabilized marls, unexpected ruptures primarily result from the formation of ettringite, which gradually damages the soil structure. This article aims to assess the impact of nanosilica on the formation of ettringite and the nanostructure of calcium silicate hydrate (C-S-H) during the marl soil stabilization process with lime. To achieve this, marl soil was stabilized with varying percentages of lime and nanosilica. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images were collected to observe changes in mineralogy and microstructural properties. Various geotechnical parameters, including granularity, Atterberg limits, compressive strength, and pH, were measured. The results indicate that the uniform distribution of nanosilica in marl-lime soils enhances pozzolanic activities, calcium aluminate hydrate growth (C-A-H), and the nanostructure of calcium silicate hydrate (C-S-H). According to XRD and SEM experiments, the presence of nanosilica reduces the formation of ettringite. Moreover, the compressive strength of modified samples exhibited an upward trend. In the experimental sample manipulated with 1% nanosilica combined with 6% lime, the compressive strength increased by 1.84 MPa during the initial 7 days, representing an approximately 18-fold improvement compared to the control sample.

Marl clays with varying levels of calcite content often exhibit more erratic behavior compared to other problematic soils, especially when exposed to repetitive Freeze-Thaw (F-T) cycles. It is crucial to prioritize the mechanical properties and durability of this particular soil variety as neglecting such characteristics can result in irreversible harm to the superstructures. This research focused on examining the utilization of lime and Nanoclay (NC) as stabilizers and Glass Fiber (GF) as reinforcement for natural marl soil. The study involved preparing samples with 6% lime and up to 1.5% NC, combined with varying amounts of GF ranging from 0 to 1%. The samples were cured for 7 and 28 days and subjected to 0, 1, 4, and 8 F-T cycles. Several Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS) tests as well as microstructural analyses including Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) were performed on the samples before and after being exposed to F-T cycles. Results showed that the application of GF enhanced the UCS and ITS of lime-NC-stabilized marl soil by creating interlocking zones between the particles. The addition of lime and NC shifted the behavior of the soil sample from ductile to brittle, while the inclusion of GF caused the soil to revert to ductile behavior, resulting in a decrease in secant modulus (E50) and an increase in energy absorption capacity (Eu) compared to samples without GF. Furthermore, incorporating GF along with lime and NC into the marl soil improved the F-T durability even after 8 cycles and resulted in reduced strength deterioration compared to the control sample. The optimum mixture was found to be 6% lime, 1% NC, and 0.75% GF, resulting in a noteworthy improvement of 6.5 times in the ITS and a slight decrease of 6% after 8 F-T cycles compared to the untreated marl soil.