Using ecological materials such as raw earth represents an ancestral building practice that has been revisited for modern construction, thanks to its availability, low cost, environmental friendliness, and thermal properties, which offer optimal insulation and thermal comfort. This article explores the development of a new composite based on raw earth reinforced with 15% mussel shells, a by-product of the aquaculture industry, combined with two stabilizers: lime or cement (3%, 5% and 8%), in distinct formulations. This study aims to characterize the chemical and mineralogical composition of the soil and mussel shells and the thermal and mechanical properties of the composites. The results indicate that the gradual addition of lime to the soil-mussel shell mixture decreases dry density, which reduces dry mechanical strength due to increased porosity but enhances thermal properties. Conversely, incorporating cement into the soil-mussel shell mixture improves significantly mechanical properties while limiting the thermal performances.

An experimental study was conducted to evaluate the effects of crumb rubber (CR) on mechanical properties of roller compacted concrete (RCC) for use in pavements. In the experiment, proportions of 0%, 10%, 20% and 30% by volume (vol) CR, were incorporated into RCC as sand replacement material. Mixtures were made at cement contents of 275 kg/m3 (11%) and 201 kg/m3 (8.6%). The water content quantities used to prepare RCC mixtures, were determined from the moisture-dry density relationship obtained based on the soil compaction approach. Various mechanical properties were measured comprising compressive strength, splitting tensile strength, ultrasonic pulse velocity, static and dynamic moduli of elasticity. Also measured were pore-related physical tests consisting of water absorption and volume of permeable pores. It was found that cement content has significant influence on the amount of CR that can be suitably utilized in RCC mixtures. The RCCs prepared at the adequate cement content of 275 kg/m3, exhibited suitable performance for all mixtures containing up to 20% vol CR content. Results showed that the standard relationships between compressive strength, static and elastic moduli as established for normal concretes, are also applicable to RCCs.

This study explores the influence of the water-cement ratio and fiber content in engineered cementitious composite (ECC) on the mechanical characteristics of foamed lightweight soil (FLS) through experimental analysis. Two types of cementitious materials-ECC and ordinary Portland cement (OPC)-were utilized to create FLS specimens under identical parameters to examine their mechanical performance. Results indicate that ECC-FLS exhibits superior toughness, plasticity, and ductility compared to OPC-FLS, validating the potential of ECC as a high-performance material for FLS. To assess the influence of the ECC water-cement ratio, specimens were constructed with varying ratios at 0.2, 0.25, and 0.3, while maintaining other parameters as constant. The experimental results indicate that as the water-cement ratio of ECC increases, the flexural strength, compressive strength, flexural toughness, and compressive elastic modulus of the lightweight ECC-FLS gradually increase, exhibiting a better mechanical performance. Moreover, this study investigates the effect of basalt fiber content in ECC on the mechanical properties of FLS. While keeping other parameters constant, the volume content of basalt fibers varied at 0.1%, 0.3%, and 0.5%, respectively. The experimental results demonstrate that within the range of 0 to 0.5%, the mechanical properties of FLS improved with increasing fiber content. The fibers in ECC effectively enhanced the strength of FLS. In conclusion, the adoption of ECC and appropriate fiber content can significantly optimize the mechanical performance of FLS, endowing it with broader application prospects in engineering practices. ECC-FLS, characterized by excellent ductility and crack resistance, demonstrates versatile engineering applications. It is particularly suitable for soft soil foundations or regions prone to frequent geological activities, where it enhances the seismic resilience of subgrade structures. This material also serves as an ideal construction solution for underground utility tunnels, as well as for the repair and reconstruction of pavement and bridge decks. Notably, ECC-FLS enables the resource utilization of industrial solid wastes such as fly ash and slag, thereby contributing to carbon emission reduction and the realization of a circular economy. These attributes collectively position HDFLS as a sustainable and high-performance construction material with significant potential for promoting environmentally friendly infrastructure development.

The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures. In this study, a largescale experiment, in combination with numerical simulation, was conducted to investigate the influence of ground fissures on a metro shield tunnel. The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall, resulting in a two-dimensional stress state of vertical shear and axial tension-compression, and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure. In addition, the damage to curved bolts includes tensile yield, flexural yield, and shear twist, leading to obvious concrete lining damage, particularly at the vault, arch bottom, and hance, indicating that the joints in these positions are weak areas. The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure, suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm, and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced. This study could provide a reference for metro design in ground fissure sites. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

In the vat photopolymerization (VPP) 3D printing of ceramic cores, the solid loading is generally conducive to the microstructure and performance of products, owing to the improved bonding between adjacent layers and enhanced dimensional accuracy with increasing solid loading. In this work, the content of ceramic powder in photosensitive resin was optimized, the solid loading increased from 56 vol% to 68 vol%, and a novel curing model was established to explain the impact of solid loading on the printing precision. During sintering, the shrinkage is regulated to approximately 3 %, demonstrating a more homogeneous structure. The interlayer strength increased to 11.43 MPa while maintaining an apparent porosity of 23.47 %. Furthermore, the anisotropy of VPP-3D printed ceramic cores dependent on the solid loading was investigated. The ratio of vertical strength to horizontal strength (sigma V/sigma H) increased from 0.57 to 0.68 when the solid loading grew from 56 vol% to 68 vol%. At 1540 degrees C, the value of sigma V/sigma H was further enhanced to 0.81. This value met the precision casting criteria for ceramic cores effectively. This work can provide a reference for the investigation of high-solid-loading ceramic cores.

Frost heave in cold regions requires urgent measures to improve the mechanical properties of soils. However, harsh climatic and environmental conditions escalate the costs of engineering construction and operation. Therefore, it is imperative to enhance the sustainability of engineering designs. In this study, different sisal fibre contents, specific proportions of metakaolin, and alkaline activators were added to silty clay to alleviate frost heave, as well improve the mechanical properties of soils. Firstly, the unconfined compressive strength (UCS) and shear strength of soil samples containing varying sisal fibre geopolymer were tested before and after freeze-thaw cycles (FTCs). To analyse the effect of FTCs on thermal conductivity, the thermal conductivity of fibregeopolymer solidified soil (FGSS) with different sisal fibre contents was evaluated. Subsequently, X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry were conducted on the samples before and after the FTCs. Then, the variations in soil temperature, volumetric unfrozen water content, heat flux, vertical deformation, and soil pressure during the FTCs were analyzed. The results indicated the following: 1) Sisal fibre and geopolymer improved the mechanical performance and adhesion among soil particles of FGSS after the FTCs. 2) The thermal conductivities of FGSS showed a tendency of initially increasing, then decreasing, and finally increasing as the sisal fibre content increased. 3) The addition of sisal fibres did not cause new chemical reactions but inhibited the reaction between metakaolin and the alkaline activator. 4) The combination of sisal fibre and geopolymer effectively mitigated frost heave. 5) Sisal fibre incorporation reduces CO2 emission index and economic efficiency index. Therefore, FGSS is proposed to provide a green and effective approach for addressing geotechnical engineering issues in cold regions.

The 21st century is often referred to as the Age of Plastics where the mass consumption of disposables leads to excessive pollution and contributes to the climate crisis. Indeed, single-use plastics are frequently used in packaging applications. Thus, in line with the political and ethical demands of our times, scholars and industries are pushed to search for sustainable materials. In this work, a new generation of nanocomposites were prepared by melt mixing using poly(butylene succinate-co-adipate) (PBSA) as a matrix reinforced with 5 wt % of POSSPh nanoclusters, i.e. unmodified trisilanol phenyl POSS (POSSPh-triol) and two prepared ionic liquid-modified POSSPh (IL-g-POSSPh) having chloride (Cl-) or bis-trifluoromethanesulfonimidate (NTf2 -) counteranions, in order to develop more sustainable and efficient active packaging food systems. The incorporation of IL-g-POSSPh into the PBSA matrix led to the formation of well-dispersed POSS nanoclusters (10 to 100 nm), resulting in a significant increase of the mechanical performances, i.e., Young's modulus (982 vs 260 MPa) and strain at break (297 vs 226%). In addition, the corresponding PBSA nanocomposites displayed outstanding water (87%) and oxygen (90%) barrier properties combined with higher bactericidal and fungicidal activities. Finally, biodegradation tests under soil burial conditions showed a better ability of the PBSA nanocomposites to biodegrade after 12 weeks (84 against 58% for pure PBSA).

Carboxymethyl cellulose (CMC) has attracted considerable interest in research due to its exceptional film-forming properties and compatibility with biological systems. However, CMC films still suffer from mechanical brittleness and structural instability due to the rigid structure and many hydroxyl groups in practical applications. Herein, a nanocomposite film is reported, synthesized via inserting layered montmorillonite (MMT) into a CMC and guar gum (GG) hydrogen bond networks. Incorporating MMT with a high aspect ratio increases the number of hydrogen bond cross-linking sites among constituents, thereby enhancing the mechanical strength and toughness of nanocomposite films. The resulting CMC/GG(10)/MMT6 films show flexibility (elongation at break 83.5 +/- 4.35%), high tensile strength (53.5 +/- 1.10 MPa), and high toughness (32.16 +/- 1.04 MJ/m(3)). These films also integrate hydrophobic (up to 84.78 degrees) and high-temperature resistance (50% degradation temperature up to 304 degrees C) properties to adapt to complex practical application environments. Moreover, they exhibit excellent ultraviolet shielding performance under a wide wavelength range (200-320 nm). Soil burial experiments showed that all the films could be assimilated into the soil within about 9 days. This approach offers a simple and promising route for producing biodegradable CMC-based films for food packaging.

Most investigations in the literature concerning cement replacement with supplementary cementitious materials (SCMs) have predominantly focused on the utilization of fly ash and slag, which are not universally available. Laterite soil presents itself as a potential alternative to these commonly used SCMs, particularly where availability is an issue. Commonly found in tropical and subtropical regions, laterite soils have been extensively employed in building construction. Therefore, the present study aims to explore the incorporation of laterite soil calcined at 600 degrees C as a substitute for Portland cement (PC) in mortars, with the objective of producing sustainable construction materials. The effect of calcined laterite (CL) passing 75 mu m sieves as 10, 30 and 50% replacement of Portland cement (PC) on the fresh and hardened properties of mortars was investigated. Mortars were cured at room temperature, and subjected to setting time, flowability, ASR, mechanical strength, porosity, water absorption, bulk density test along with scanning electron microscopy analysis at 28 days. The obtained result revealed the reduction in mechanical properties with the incorporation of CL up to 50 wt% compared to the reference sample only used OPC. As incorporation rates of calcined increased, the flow and setting times (initial and final) values decreased from 197 to 138 mm and 156 to 24 min and 341 to 77 min, respectively.

Microbial induced carbonate precipitation (MICP) has the potential to have less hazardous impacts on the environment compared with traditional reinforcement technologies. In this paper, the mechanical property and cementing mechanism of MICP-treated mortar (MTM) are studied, and the double-layer rigid soaking mold is invented to prepare high-strength MTM samples. The effects of the cementation solution concentration (CSC), the concentration ratio of urea to calcium chloride (CRUC), aggregate particle size, and soaking time on the mechanical properties of MTM are researched. The results show that the strength of the MTM sample increases first and then decreases with the increase of CSC. The mean UCS of MTM samples reaches the peak of 8.19 MPa when the CSC is 1.5 M. The strength performance of MTM samples is relatively better when the CRUC is 1. For MTM samples with graded particle size, the sample with the particle size of 0.4-0.8 mm has the highest strength of 5.03 MPa. For MTM samples with full particle size, the mean UCS increases from 1.18 to 12.88 MPa with the increase of the maximum particle size from 0.2 to 2 mm. The MTM sample with full particle size has a higher strength when the maximum particle size is larger than 0.8 mm. The strength of MTM samples increases within 9 days over the soaking time and then tends to be stable at the later stage. The calcium carbonate mineral in the MTM sample is mainly calcite and a small amount of vaterite, and the strength of MTM is positively correlated with its CaCO3 content. The CaCO3 content of the sample shows a high surrounding and low middle distribution.