Search Results (11)

High-content cemented soils are critical for modern geotechnical technologies (e.g., pre-bored precast piles), yet their long-term durability remains underexplored. This study investigates the 28- to 365-day mechanical and microstructural evolution of high-content cemented silty clay under freshwater and seawater curing via UCS, SEM, MIP, and XRD. Under freshwater, cement content directly dictated strength, with the 8:2 mix reaching 24.31 MPa at 365 days. However, marginal efficiency analysis confirmed diminishing returns for excessive binder, establishing the 7:3 ratio as the optimal baseline. Seawater exposure induced a biphasic response: a 4.6% early strength gain at 28 days, followed by severe degradation (a 23.5% drop at 365 days). Concurrently, the failure mode shifted to macroscopic “pseudo-ductility,” with peak strain increasing from 2.37% to 3.04%. Crucially, a micro–macro inconsistency emerged: although seawater physically refined the pore structure (micropore proportion doubled to 30.2% at 90 days) via expansive salts filling mesopores, macroscopic strength declined. XRD confirmed this degradation coincides with severe long-term alkaline buffer (Ca(OH)₂) depletion. Consequently, lifecycle durability assessments for high-binder marine systems must not rely solely on physical metrics like porosity, but adopt a coupled multi-factor framework prioritizing chemical stability. Full article

This study investigates the impact of the Static Press-in Piling Machine (SPPM) on marine soft clay foundations in the Ningbo area using model testing and numerical simulation. In marine soft clay areas, it is common to increase the bearing capacity of the foundation by curing the foundation prior to the deployment of the SPPM to prevent problems such as “trapping”. This research examines the relationship between the unconfined compressive strength and the ultimate bearing capacity of foundations reinforced with varying percentages of cement. Unconfined compressive strength (UCS) tests and foundation bearing capacity model tests were conducted to establish the relationship between soil strength and foundation performance. The results indicate that the ultimate bearing capacity of the foundation increases linearly with cement content under the static load of the SPPM. Numerical simulations reveal that the SPPM’s long barge significantly affects soil stress distribution, emphasizing the need to incorporate these effects into the design of static pile systems. Full article

This study investigates the strength development of cement-stabilized marine clay, which is influenced by a complex interplay of microstructural factors. To optimize its performance for coastal and offshore engineering, we explored the relationship between microstructure and unconfined compressive strength (UCS). Using Scanning Electron Microscopy (SEM) and the Pore/Crack Analysis System (PCAS), we analyzed samples with varying cement contents (10%, 15%, and 20%) and curing times (3, 7, 14, and 28 days). Key microstructural parameters, including porosity, particle shape, size, and arrangement, were quantified and correlated with UCS results. A novel comprehensive micro-parameter was introduced to encapsulate the combined effects of these factors, revealing an exponential relationship with strength development. The findings provide a quantitative framework for predicting the performance of cement-stabilized marine clay, contributing to more efficient solutions in geotechnical engineering. Full article

Nowadays, the use of new compound chemical stabilizers to treat marine clay has gained significant attention. However, the complex non-linear relationship between the influencing factors and the unconfined compressive strength of chemically treated marine clay is not clear. In order to study the influence of various factors (dosage, type of stabilizer, curing age) on the unconfined compressive strength of solidified soil during chemical treatment, experiments were performed to determine the unconfined compressive strength of soft marine clay modified with various types of stabilizers. Further, an artificial neural network (ANN) model was used to establish a prediction model based on the unconfined compressive strength test data and to verify the performance. Sensitivity and optimization analyses were further conducted to explore the relative significance of parameters as well as the optimal dosage amount. Research has found that when the content of aluminate cement is 89.5% and the content of curing agent is 30%, the unconfined compressive strength significantly increases after 28 days of solidification, and the change in quicklime content has the greatest effect on the improvement in the unconfined compressive strength. The influence of modifiers on the unconfined compressive strength is in the order: potassium hydroxide > kingsilica > quick lime > bassanite. The values of each factor were obtained when the unconfined compressive strength was the maximum, which provided support for the optimization of the treatment scheme. The analysis of chemical treatment is no longer limited to the linear relationship according to the test results, which proves the feasibility of non-linear relationship analysis based on the artificial neural network. Full article

Cement-stabilization of weak and soft soils is an efficient way for ground improvement. Traditional Portland cement remains the most popular cementitious material in practice, and thus, a proper dosage design of cement-stabilized soil is of practical interest to meet the sustainable engineering requirements and to remedy environmental concerns. Based on the unconfined compression test of cement-stabilized Qiantang River silty clay, the effects of cement content, mixing moisture content, mixing-water-to-cement ratio, and curing time on the unconfined compressive strength were investigated. The results show that the mixing-water-to-cement ratio can comprehensively characterize the effects of cement content and water content on the unconfined compressive strength of the cement-stabilized clay. A prediction method for the unconfined compressive strength of cement-stabilized Qiantang River silty clay has been proposed with considerations for mixing-water-to-cement ratio and curing time. By comparing the experimental data of the present study with the existing literature data, it is found that there is a unified relationship between the unconfined compressive strength and the mixing-water-to-cement ratio of cement-stabilized Qiantang River silty clay, kaolin, Singapore marine clay, and Bangkok clay under the same curing time. The prediction method recommended by the standard may overestimate the unconfined compressive strength of cement-stabilized Qiantang River silty clay cured for 90 days. Full article

Marine soft clays are prevalent in coastal regions of China, giving rise to engineering challenges such as salt swelling, corrosion, and load bearing in foundations with soft soil. This study is dedicated to enhancing the mechanical properties of fiber-reinforced cement-stabilized soft clay (FCSSC) and revealing its strengthening mechanism. Uniaxial compression tests are performed to explore the impact of fiber length, fiber amount, and curing ages on mechanical behavior. The stabilization mechanisms of cement and glass fibers are explored through damage analyses and microscopy. Based on the experimental results, a damage constitutive model is formulated for FCSSC, and its validity is established by comparing fitting curves with testing curves. The results demonstrate a significant improvement in the mechanical properties of the stabilized soil, attributed to the synergistic effects of the cement and glass fibers. The growth rate of the unconfined compressive strength decreased with increasing curing ages. Notably, the fiber length significantly impacted the strength index, with short-chopped fibers playing a crucial role in strength enhancement. The compressive strength exhibited an initial increase followed by a decrease with rising fiber content, reaching a maximum between 0.3% and 0.4%. The bridging effect of the glass fibers proved effective in inhibiting compression crack expansion and mitigating structural damage of the soil sample. However, excessive fiber content or length led to improved local porosity, resulting in the deterioration of strength and deformation properties. The stress–strain curves fitted using the proposed damage constitutive model accurately reflected the stress–strain relationship and deformation characteristics of the FCSSC. Full article

The understanding of the mechanical properties of sensitive marine clay subgrade stabilized with cement is vital for the safe, economical, and durable design of road structures. As the curing temperature affects the cement hydration progress, it is necessary to investigate the influence of the temperature on the evolution of the mechanical properties of cement-reinforced marine clay in road construction. A column testing and relevant monitoring program were performed to study the effect of various curing temperatures (2 °C, 22 °C, and 40 °C) on the mechanical properties’ development of cement-reinforced clay within 28 days. After these cement clay samples were cured for a specific time (1, 3, 7, and 28 days), they were subjected to two mechanical tests (i.e., California Bearing Ratio (CBR) test and uniaxial compressive strength (UCS) test). The findings reveal that a higher curing temperature accelerates cement hydration and self-desiccation. Consequently, the UCS and CBR values increase with curing temperature and the strength might vary by more times, especially for early age (≤7 days) samples. The results of this study contribute to a deeper understanding of the influence of temperature on the mechanical properties of the cement-reinforced clay and thus provide practical guidance with regards to road construction in the field. Full article

The porosity-to-cement index ($\mathsf{\eta }$/C_iv) has been extensively applied to study the evolution of different types of soil stabilization. However, this index has still not been used to characterize soils cemented with crushed limestone waste (CLW). In this sense, this paper sought to analyze the applicability of the porosity-to-cement index over the unconfined compressive strength (${\mathrm{q}}_{\mathrm{u}}$) and initial stiffness at small deformations ($G_{\mathrm{o}}$) of clayey soil improved with CLW and Portland cement. In addition, a microstructural analysis (SEM and EDX tests) was also conducted. CLW addition increased soil strength and stiffness over time. Moreover, ${\mathrm{q}}_{\mathrm{u}}$ and $G_{\mathrm{o}}$ compacted mixtures containing CLW have established a distinctive correlation. Chemical microanalyses have uncovered a complex interfacial interaction between the soil, cement, and fine CLW particles, leading to a notable reduction in porosity. Full article

In this study, an environmentally friendly ionic soil stabilizer (ISS) was adopted with combination of Portland cement to stabilize a marine muck. The macro and micro tests results demonstrated that the ISS was an effective stabilizer to improve the strength of marine muck when it was used combined with cement after adding the alkalizer NaOH. Except for the reduction in interlayer distance of clay minerals by ISS, Ca${}^{2+}$ and SO${}_4^{2-}$ dissolved from ISS promoted the production of ettringite (AFt), pozzolanic and carbonation reactions of Portland cement in the presence of NaOH. Meanwhile, the hydration products of curing reaction notably agglomerated soil particles, which caused an obvious decrease of pores and a high increase of strength for solidified soils. Furthermore, this combination of stabilizers can not only save the dosage of cement, but also accelerate the solidification speed, decrease the cement setting time within 7 days to meet the curing requirements, and enhance the strength of solidified soils. Full article

The world’s population is growing at a rapid pace, thus increasing the need for shelter, which, because of increased carbon emissions, is making our planet less habitable. Thus, supplementary cementitious materials (SCMs) are used to reduce the embodied carbon emissions in the building sector. Wood-ash, as a replacement for cement in ground improvement, seems to be a promising material. In this study, we considered the strength, stiffness, and microstructural behavior of marine deposited clays of Cyprus treated with cement and wood-ash as a cement replacement. Since clay is abundant in nature, it could help stabilize waste to improve the mechanical behavior of produced composites. Portland cement (7%, 10%, and 13%) was replaced with various amount of wood-ash (5% and 10%) with two different dry densities (1400 and 1600 kg/m3) and three distinct curing periods (7, 28, and 60 days). Unconfined compressive strength (UCS), direct shear, porosity and pulse velocity tests were performed. Additionally, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy analysis (EDX) were performed for microstructural evaluation of clay–wood-ash–cement mixtures. The results revealed that the replacement of cement with 5% of wood-ash yielded superior performance. The microstructure investigation of wood-ash–cement–clay blends further showed the formation of a densified matrix with stable bonds. Furthermore, the porosity and strength properties (unconfined compressive strength, splitting tensile strength, cohesion (C) and friction angle (ϕ)) of blends have unique relationships with porosity and binder contents, which were further confirmed by other supplementary materials and soils. Full article

Marine clay deposits are commonly found worldwide. Considering the cost of dumping and related environmental concerns, an alternative solution involving the reuse of soils that have poor conditions is crucial. In this research, the authors examined the strength, microstructure, and wet–dry resistance of triple-binder composites of marine-deposited clays and compiled a corresponding database. In order to evaluate the wetting–drying resistance of the laboratory-produced samples, the accumulated mass loss (ALM) was calculated. The use of slag alone as a binder, at any percentage, increased the ALM up to 2%. However, the use of lime as the third binder seemed to accelerate the chemical reactions associated with the hydration of clay and cementitious material and to enhance the chemical stability, i.e., specimens that included both lime and slag experienced the same ALM as specimens treated with cement only. Scanning electron microscopy analysis confirmed the durability improvements of these clays. The proposed unconfined compressive strength–porosity and accumulated mass loss relationship yielded practical approximation for the fine- and coarse-grained soils blended with up to three binders until 60 days of curing. The laboratory-produced mixes showed reduction of embodied energy and embodied carbon dioxide (eCO₂) emissions for the proposed models. Full article