Earth-building materials offer a low-carbon option for construction, but their poor water resistance limits their adoption by the construction industry. Adding biopolymers to earth materials can improve mechanical strength and water resistance but also promote mold mycelium growth that reduces indoor air quality. However, for other applications such as insulation or packaging, the controlled growth of specific mycelium is seen as a promising option for producing natural waterproof materials. These application require heat-inactivation to kill the mycelium and preserve air quality. It is currently unknown if heat-inactivated mold mycelium could improve the water resistance of earth materials. This study explores a new design by promoting the natural growth of molds on biostabilized earth materials and studying the effect on earth material properties after heat inactivation. Earth mortars were prepared by mixing soil, water, and biopolymers (2 % of soil mass) to a consistent texture. Twenty formulations, using two soils and four biopolymers, were subjected to two different 21-day cures, under dry (oven at 50 degrees C) or humid (30 degrees C, 98 % RH) conditions. Mortar properties were investigated after a 48-h 80 degrees C heat treatment to inactivate mold. We found that the humid cure consistently prompted mold growth on biostabilized mortars, which was associated with significantly higher water resistance compared to unexposed mortars. Specifically, capillary water absorption and mass loss after water spray was reduced by 28 % and 64 % respectively. These improvements were achieved with minimal impact on shrinkage, density, and mechanical strength. The amelioration in water resistance was attributed to the hydrophobic mold mycelium filling the earth mortar pore as observed by UV microscopy. Together, this study demonstrates that mycelium could dramatically improve the water resistance of biostabilized earth materials.

This research investigated the production of biodegradable plastic films made from a blend of carrageenan and corn starch biopolymers. The procedure included producing bioplastic resin pellets using a single screw extrusion at a 110 degrees C temperature, followed by hot compression at a temperature of 160 degrees C to form a biodegradable plastic film. The project aimed to develop a continuous biodegradable plastic production method, particularly made from carrageenan, which is more adaptable for commercial-scale production. The carrageenan/corn starch films were prepared with various compositions, ranging from formulations dominated by carrageenan (56:14% w/w) to those dominated by corn starch (14:56% w/w), with the addition of a constant amount of glycerol (30% w/w) as a plasticizer. After the films were obtained, each of the samples was evaluated for their physico-mechanical properties, chemical structure, water sensitivity, and soil biodegradability. In general, an increase in corn starch content within the film matrix led to an enhancement of the overall properties of the resulting film. The film with the highest corn starch content exhibited tensile strength and elongation at break values that were 49% and 163% higher, respectively, compared to the film with the lowest corn starch content. Additionally, these samples demonstrated improved thermal stability, with a 12% increase in the thermal decomposition temperature, and enhanced barrier properties, as evidenced by a 6% reduction in water vapor permeability and a 72% decrease in water uptake. This is mainly due to the inherent molecular structure of corn starch, particularly due to its long straight-glucose chains. On the other hand, carrageenan increased the biodegradability rate of the films. These findings demonstrate the potential of carrageenan/corn starch blends as promising candidates for future packaging materials.

This study sought to develop a biodegradable material that can be a substitute for conventional plastics and is sustainable and eco-friendly. The research's primary focus was the conversion of carboxymethyl cellulose (CMC) derived from agricultural waste into a bioplastic film that is satisfactory for use in packaging. The weak mechanical stability and excessive water sensitivity of CMC films limit their widespread use. To overcome these limitations, therefore, CMC films were reinforced with varying concentrations (0, 5, 10, 15, 20, and 25%) of zinc oxide nanoparticles (ZnO NPs), using a solution casting method. The films were also surface-modified by spray coating with a 1:1 composite mixture of poly(dimethylsiloxane) (PDMS) and starch. An array of analyses were used to investigate the films' properties. Structural characterization employing Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the successful incorporation of ZnO and uniformity of PDMS/starch coating on the films. Thermogravimetric analysis (TGA) and mechanical testing revealed that the films' thermal and mechanical properties were improved by the incorporation of ZnO, with the film CZ20-C exhibiting the highest value of tensile strength--14.029 MPa--and 27.59% elongation at break. The films exhibited excellent water resistance, as evidenced by a remarkable increase in their water contact angle to 152.04 degrees. Furthermore, biodegradability studies demonstrated that the films degraded by 84.78% in soil within 20 days, under ambient conditions. Films with these desirable characteristics are therefore producible through the study's facile strategy for preparing CMC-based eco-friendly composite films that have excellent potential to replace conventional plastic in the packaging industry.

Utilizing casein in geotechnical engineering and construction can reduce global dairy waste. Variations in initial water content during sample preparation influence cation and OH ion availability, alkaline additive concentrations, casein binder function, and rheological properties of the casein solution. This study investigates the impact of initial water content and casein solution rheology on unconfined compressive strength in two soil types (coarse and fine) treated with casein, both in dry conditions and after water immersion. The study also assesses the long-term performance of casein-treated soil under bio-decomposition. Results suggest that increasing casein content, beyond the optimal ratio, can enhance strength by adjusting initial water concentration. Notably, calcium caseinate-treated soil shows improved water resistance, with wet strength reaching 833 kPa at 5% casein and 20% initial water content, due to reduced viscosity and better workability, resulting in a more rigid soil structure during preparation. We propose an empirical formula describing the influence of casein solution rheological characteristics on soil strength. Furthermore, artificial neural networks, developed from experimental data, predict casein-treated soil strength, highlighting the significance of initial water content and rheological parameters.

This study explores the mechanical properties of casein-treated and agar-treated sand, considering biopolymer content, dehydration time, immersion periods, relative densities, porosity ratios, and porosity/volumetric biopolymer contents. Adding casein was found to improve the water resistance of agar-treated sand. Results reveal that 4 % and 5 % casein-treated sand exhibit the highest water resistance after a week of submersion, with wet strength of 0.359 MPa and 0.493 MPa, respectively. Increased relative density and biopolymer content correlate with higher unconfined compressive strength, inversely linked to sample porosity. An empirical equation connecting unconfined compressive strength to porosity/volumetric biopolymer content is derived.

In recent years, the growing demand for sustainable packaging has significantly fueled the quest to explore novel approaches that enhance the applicability of renewable alternatives. This study leverages the unique properties of silica aerogel (SA) to address the limitations of traditional molded pulp products. By integrating SA into recycled paper pulp (RP), we aimed to improve water resistance, thermal stability, and mechanical properties. Composites were prepared with varying SA concentrations (1-10 %). Contact angle measurements showed enhanced hydrophobicity, with RP/SA3 % achieving a contact angle of 152.09 degrees, compared to 122.39 degrees for neat RP. The tensile index (TI) of RP/SA composites with 3 % SA increased by 21.09 % compared to neat RP, indicating better mechanical strength. Thermal conductivity significantly decreased, with RP/SA10 % reducing from 0.155 W m- 1 center dot K- 1 in neat RP to 0.088 W m- 1 center dot K- 1, a 43.2 % improvement in thermal insulation. Additionally, composites with 1 % and 3 % SA maintained high biodegradability, showing over 50 % degradation after six weeks in soil. These results suggest that incorporating SA into RP composites enhances their functionality without compromising biodegradability, offering a promising solution for sustainable packaging. As regulatory bodies emphasize resource management and waste reduction, the potential of these innovative and environmentally friendly packaging solutions becomes increasingly significant.

Growing environmental concern has led to an increase in the demand for ecofriendly coatings for paper. The use of renewable feedstock in place of synthetic raw materials is generating much interest in new scientific and technological developments. In this regard, we developed a biobased coating material using crosslinked alkyl chitosan with the objective to enhance the properties of kraft paper. Here, we used simple 1,4 conjugate addition between chitosan (Ch) and pentaerythritol triacrylate, followed by octadecyl amine (ODA), producing crosslinked ODA-grafted chitosan (Ch-ODA). The formation of Ch-ODA was confirmed by FT-IR and solid-state C-13 NMR spectroscopic studies. The dispersion of Ch-ODA was used for the dip-coating of kraft papers, and such coated kraft papers showed significant improvement in mechanical properties (tensile index: from 17.1 to 32.8 N m/g), hydrophobicity (water contact angle (WCA): from 81.5 degrees to 119.8 degrees), good tolerance to sandpaper abrasion (WCA: 112-139 degrees after 100 cycles), and adhesive tape peeling (WCA: 113 degrees-139 degrees after 10 cycles). The impact of the coating on the porosity of the kraft paper was analyzed by scanning electron microscopy. The coated kraft paper was found to be compostable in soil, and we explored its potential use in mulching.

Most earthen sites are located in open environments eroded by wind and rain, resulting in spalling and cracking caused by shrinkage due to constant water absorption and loss. Together, these issues seriously affect the stability of such sites. Gypsum-lime-modified soil offers relatively strong mechanical properties but poor water resistance. If such soil becomes damp or immersed in water, its strength is significantly reduced, making it unviable for use as a material in the preparation of earthen sites. In this study, we achieved the composite addition of a certain amount of sodium methyl silicate (SMS), titanium dioxide (TiO2), and graphene oxide (GO) into gypsum-lime-modified soil and analyzed the microstructural evolution of the composite-modified soil using characterization methods such as XRD, SEM, and EDS. A comparative study was conducted on changes in the mechanical properties of the composite-modified soil and original soil before and after immersion using water erosion, unconfined compression (UCS), and unconsolidated undrained (UU) triaxial compression tests. These analyses revealed the micro-mechanisms for improving the waterproof performance of the composite-modified soil. The results showed that the addition of SMS, TiO2, and GO did not change the crystal structure or composition of the original soil. In addition, TiO2 and GO were evenly distributed between the modified soil particles, playing a positive role in filling and stabilizing the structure of the modified soil. After being immersed in water for one hour, the original soil experienced structural instability leading to collapse. While the water absorption rate of the composite-modified soil was only 0.84%, its unconfined compressive strength was 4.88 MPa (the strength retention rate before and after immersion was as high as 93.1%), and the shear strength was 614 kPa (the strength retention rate before and after immersion was as high as 96.7%).

The primary purpose of this study is to assess excavated soil rich in limestone for its use as a raw material in manufacturing Compressed and Stabilized Earth Blocks (CSEBS). Valorization of cut excavation is a promising solution to reduce the strain on natural resources, which aligns with sustainable development goals. The identification of raw materials was performed to study the main properties of blocks manufactured. Samples are obtained by chemical stabilization with the addition of 8% cement. They are compacted at different pressures (1.5, 2.5, 3.5, 5 and 10 MPa) using a hydraulic press. Certainly the stabilization and the compaction of the block contribute significantly to its strength properties but the use of carbonate-rich fine-grained earth has further strengthened the material. The first part of this paper spotlight the measurement of the optimal water content (omega(opt)) for the different levels of applied stresses. The second part, presents an experimental study conducted to investigate the thermal-mechanical performance and durability of CSEBS. The compressing strength recorded a value of 16.32 MPa at a compressing stress of 10 MPa and the thermal conductivity observes an increase with increasing the compaction because this tends to densify the mixture. Moreover, the hydrous properties of the compressed stabilized earth blocks are stated by gradually raising the compacting pressure.

Urban construction has generated substantial amounts of waste soils, impeding urban ecological development. With the aim of promoting waste recycling, waste soils possess a high potential for sustainable utilization in subgrade construction. However, these waste materials exhibit inadequate engineering properties and necessitate stabilization for an investigation into their long-term performance as subgrade filling materials. Initially, a thorough assessment and comparison were conducted to examine the key mechanical properties of lime- and cement-stabilized soils with mixed ratios (total stabilizer contents ranging from 2% to 8%). The results indicated that these soils met the requirements of subgrade materials except for the 2% lime-treated soil. Subsequently, to reveal the improvement in water resistance of stabilized waste soil (e.g., under conditions of rainfall or elevated groundwater table), the effects of soil densities and stabilizer contents on the disintegration characteristics were investigated using a range of disintegration tests. An evolutionary model for the disintegration ratio of stabilized soils was then developed to predict the process of disintegration breakage. This model facilitates the quantification of the lower disintegration rates and elevated disintegration time attributed to higher levels of compactness and stabilizer contents during a three-stage disintegration process. This enhances the understanding and evaluation of sustainable applications in stabilized waste soils used as subgrade filling materials.