The rapid depletion of natural aggregate resources has led to the exploration of recycled aggregates as sustainable alternatives. The steel industry annually generates 28 million tons of magnesia-based waste refractories (WMRs), making their incorporation into construction materials a potential strategy for resource conservation. However, WMR recycling poses a challenge because of its susceptibility to volume expansion during hydration. This study evaluated the feasibility of an environmentally friendly additive, lignosulfonate (LS), for stabilizing crushed waste magnesia refractory bricks (CWMR) to explore the potential application of WMR as construction aggregates. The swelling properties, including the free swell index (FSI) and the swell pressure (Ps), and mechanical properties including unconfined/uniaxial compressive strength (qU), shear wave velocity (VS), and thermal conductivity (lambda) of LS stabilized CWMR (CWMLS) were evaluated over different curing periods at varying LS contents (LSc). Hydration transformed CWMR from sandlike to highly plastic silt-like, resulting in a significant FSI of 250 % and Ps of 5.2 MPa. LS effectively stabilized CWMR, as indicated by decreased FSI and Ps, and enhanced qU and VS. Microscopic observation and mineralogy analyzes confirmed that LS stabilizes CWMR by adsorbing onto its surface. Stabilization of thermal conductivity at higher LSc over curing periods further supports these interactions. Macroscopic behavioral analyzes give stabilized effect of 94.3 % at LSc = 5 % with minimal improvement at higher LSc. These findings highlight LS as a promising stabilizer for mitigating hydration-induced expansion and improving the mechanical properties of CWMR, supporting its application as a recycled aggregate in construction.

The objective of this study was to enhance the mechanical properties of gravelly soil and to consider the binding and filling effects of xanthan gum and calcium lignosulfonate. To this end, gravelly soil samples were prepared with various dosages of xanthan gum and calcium lignosulfonate, and their curing effects were investigated. The mechanical properties and strength parameters of the cured gravelly soil were investigated using unconfined compressive strength (UCS) tests and conventional triaxial compression tests. Furthermore, scanning electron microscopy (SEM) was employed to examine the microstructure and curing mechanisms of the gravelly soil treated with these additives. The findings demonstrate that as the dosage increases, both xanthan gum and calcium lignosulfonate markedly enhance the compressive strength and shear strength of the gravelly soil. The curing effect of xanthan gum was found to be more pronounced with higher dosages, while the optimal curing effect for calcium lignosulfonate was achieved at a dosage of 4%. The gravelly soil treated with xanthan gum exhibited superior performance compared to that treated with calcium lignosulfonate when the same dosage was used. Moreover, at elevated confining pressures, the binding effect of xanthan gum and calcium lignosulfonate on the gravelly soil was less pronounced than the strength effect imparted by the confining pressure. This suggests that the impact of dosage on the shear strength of the gravelly soil is diminished at higher confining pressures. The stabilization of crushed stone soil by xanthan gum is a complex process that involves two main mechanisms: bonding and cementation, and filling and film-forming. The curing mechanism of calcium lignosulfonate-cured gravelly soil can be summarized as follows: ion exchange, adsorption and encapsulation, and pore filling and binding effects. The findings of this research offer significant insights that are pertinent to the construction of high earth-rock dams and related engineering applications.

Lignosulfonate (LS), an environmentally friendly and non-toxic material, has attracted attention as a non-traditional soil stabilizer. However, LS could be easily washed out from soil due to its high water-solubility, which leads to the consequent loss of strength. Therefore, an additional admixture is needed to overcome this limitation. In this study, polyethyleneimine (PEI) was mixed with LS to stabilize silica sand. The consequent improvements in the water-resistant and strength characteristics of LS-treated soil were investigated through the unconfined compressive strength (UCS) test, triaxial test, and cyclic wetting- drying tests. The results demonstrated that the UCS had an increasing trend with a rise in LS content. Moreover, the UCS was influenced by the drying out of the water from the specimen related to the LS concentration and the curing time: a higher concentration and a longer curing duration improve the UCS. According to the triaxial test, the deviatoric stress also increased with the LS content. In addition, both the soil's cohesion and secant elastic modulus were improved in a more ductile manner than typical cemented soil. In the cyclic wetting-drying test, no disintegration of the specimen was observed. Although the UCS of the treated soil in wet condition revealed a notable decrease, after re-dry for seven days in a controlled room, its strength recovered to about 86% of that in its initial dry condition.

Controlled low-strength materials (CLSM) have been used for conventional backfilling and structural filling owing to their flowability, self-consolidating, and self-leveling features. This study investigates the rheological, mechanical, and dynamic characteristics of lignosulfonate-modified CLSM. The elemental analysis of lignosulfonate reveals the presence of various elements and an irregular morphology, as observed using a scanning electron microscope. A series of tests, including flow tests, Vicat needle tests, uniaxial compression tests, and shear wave monitoring, are conducted to evaluate the flowability, setting time, strength, and shear wave velocity of lignosulfonate-modified CLSM. The experimental results show that the flowability and initial and final setting times of the CLSM mixtures increase with increasing lignosulfonate content (LC), which improves workability in the field but results in a slight strength loss. Regarding the uniaxial compressive strength, CLSM mixtures with lower LC exhibit a rapid increase in strength during the early stages, while those with higher LC show higher performance on the 14th day of curing. In contrast, an LC of 0.21% led to a slight reduction in the strength on the 28th day. The current study also shows an exponential correlation between the uniaxial compressive strength and shear wave velocity.

In cold regions, the extensive distribution of silt exhibits limited applicability in engineering under freeze-thaw cycles. To address this issue, this study employed rice husk carbon and calcium lignosulfonate to stabilize silt from cold areas. The mechanical properties of the stabilized silt under freeze-thaw conditions were evaluated through unconfined compressive strength tests and triaxial shear tests. Additionally, scanning electron microscopy was utilized to analyze the mechanisms behind the stabilization. Ultimately, a damage model for rice husk carbon-calcium lignosulfonate stabilized silt was constructed based on the Weibull distribution function and Lemaitre's principle of equivalent strain. The findings indicate that as the content of rice husk carbon and calcium lignosulfonate increases, the rate of improvement in the compressive strength of the stabilized silt progressively accelerates. With an increase in the number of freeze-thaw cycles, the deviatoric stress of the stabilized soil gradually diminishes; the decline in peak deviatoric stress becomes more gradual, while the reduction in cohesion intensifies. The decrease in the angle of internal friction is relatively minor. Microscopic examinations reveal that as the number of freeze-thaw cycles increases, the soil pores tend to enlarge and multiply. The established damage model for stabilized silt under freeze-thaw cycles and applied loads demonstrates a similar pattern between the experimental and theoretical curves under four different confining pressures, reflecting an initial rapid increase followed by a steady trend. Thus, it is evident that the damage model for stabilized silt under freeze-thaw conditions outperforms traditional constitutive models, offering a more accurate depiction of the experimental variations observed.

Red clay exhibits characteristics such as softening owing to water absorption and cracking because of water loss, which can lead to slope instability, road cracking, and compromised structural integrity when used directly in roadbed filling. Although the addition of industrial materials such as cement is a common engineering treatment, it severely impairs soil renewability. Lignosulfonate (LS) extracted from paper plant waste fluids is a natural bio-based polymer with promising applications as a soil improver. In this study, the boundary moisture content and mechanical properties of LS-treated red clay were investigated using Atterberg, unconfined compressive strength, and direct shear strength tests. Additionally, the LS-treated red clay modification mechanism was explored at multiple scales using zeta potential analysis, X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The results indicated that the LS dosage significantly affected both the water content and mechanical strength of the red clay boundaries. The optimal dosage of LS for red clay was 3 wt. %, at which the liquid limit was reduced by 32.97%, the plastic limit by 19.33%, and the plasticity index by 48.37%. The 28-day compressive strength of LS-treated red clay was increased by 378.4%, and the direct shear strength was increased by 136%. Analysis of the microstructure and mineral composition revealed that the LS-treated red clay did not form new minerals, but primarily filled pores and connected soil particles. Through the combined effects of hydrogen bonds, electrostatic interactions, and cation exchange, the LS-treated red clay reduced the size of the mineral particles and the thickness of the mineral double electric layer, resulting in increased structural densification. These results are of great scientific significance for the ecological modification of soils.

The utilization of lignosulfonate (LS) as a naturally derived biopolymer sourced from lignin in soil stabilization has gained significant attention in recent years. Its intermolecular interaction, hydrophobic and hydrophilic effects, adhesive and binding properties, erosion control abilities, compatibility with various soil types, and environmental sustainability make it a promising alternative to traditional soil stabilizers as well as highlighting its importance. By integrating LS into soil stabilization practices, soil properties can be enhanced, and an ecofriendlier approach can be adopted in the construction sector. This comprehensive review paper extensively examines the applications and structure of LS, as well as their efficacy and mechanisms on a micro-level scale. Afterward, it discusses the geotechnical characteristics of LS-treated soils, including consistency characteristics, dispersivity properties and erosion behavior, electrical conductivity, compaction parameters, permeability and hydraulic conductivity, compressibility characteristics, swelling potential, strength and stiffness properties, durability, and cyclic loading response. In general, LS incorporation into the soils could enhance the geotechnical properties. For instance, the Unconfined Compressive Strength (UCS) of fine-grained soils was observed to improve up to 105 %, while in the case of granular soils, the improvement can be as high as 450 %. This review also examines the economic and environmental efficiency, as well as challenges and ways forward related to LS stabilization. This can lead to economic and environmental benefits given the abundance of LS as a plant polymer for cleaner production and owing to its carbon neutrality and renewability.

The cement composite calcium lignosulfonate is used to enhance the mechanical properties and the freeze-thaw resistance of loess. Based on an unconfined compressive test under different freeze-thaw cycles, the influence of cement dosage, curing age, and freeze-thaw cycles on compressive strength are discussed. The results indicate that the strength of loess can increase by up to 13 times, and the loss of strength is reduced from 72% to 28% under the reinforcement of cement dosage and curing age. The loss of strength is mainly concentrated in the initial 5 freeze-thaw cycles, and the structure gradually stabilizes after 10 freeze-thaw cycles. In addition, according to the X-ray diffraction test, it is found that the stabilized loess exhibits a comparatively more stable mineral composition. The scanning electron microscope results reveal that hydration products enveloped the soil particles, forming a mesh structure that strengthens the connection between the soil particles. The freeze-thaw damage makes the small and medium pores turn into large pores in loess, while the stabilized loess changes micro and small pores into small and medium pores, with no large pores found. It is feasible to improve loess with the cement composite calcium lignosulfonate, which can provide references for the reinforcement treatment of loess.

The road sector is actively exploring strategies to reduce greenhouse gas emissions by investigating the potential use of local and recycled materials, including quarry waste sand. This study presents the results of frost heave and repeated load triaxial tests conducted on fully characterized Norwegian quarry waste sands. The tests examined the effects of two nontraditional additives, lignosulfonate and organosilane, on the engineering properties of the quarry waste sands. Thermal conductivity tests were also performed on untreated samples. The quarry waste sands, including gneiss, gabbro, quartz-diorite, limestone, and granite, exhibited varying fine contents ranging from 7% to 28%. A thermal conductivity model was validated with R2 values ranging from 0.87 to 0.99. The frost susceptibility was found to be reduced by 65% in samples treated with 1% additive content, and further improvements of 85% at a 2% concentration. Moreover, the addition of 1.5% lignosulfonate or 0.5% organosilane significantly improved the resilient modulus, elastic stiffness, and resistance to permanent deformation in all samples. These findings highlight the improved frost protection and mechanical properties of the stabilized quarry waste sands, contributing to enhanced pavement stability and longevity. Furthermore, incorporating lignosulfonate additives in quarry waste sands offers a promising solution for environmentally sustainable road construction. Further research, including comprehensive field-testing and life-cycle cost analyses, is recommended to assess the economic, technical, and environmental aspects of these additives.

High -value utilization of bleached lignin has been widely used in different fields, whereas the investigation on darkened lignin in composite materials was often ignored. In this work, a sort of eco-friendly and structurally robust sodium carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVA)/sodium lignosulfonate (SLS) black composite mulch film was elaborately designed. The chelation and redox reaction effect between Fe ions and SLS lead to the formation of a more quinones structure on lignin, darkening both lignin and the mulch films. The chelation effect between Fe ions and biopolymer formed three-dimensional structures, which can be used as sacrifice bonds to dissipate energy and improve the mechanical properties of the composite films. In particular, the maximum elongation at break and toughness increased from 48.4 % and 1141 kJ/m 3 for the CMC/PVA film to 210.9 % and 1426 kJ/m 3 for the optimized CMC/PVA/SLS/Fe black mulch film, respectively. In addition, the optimized black mulch film also possesses good soil water retention, thermal preservation effect, controlled urea release, and well biodegradability. This work offered a novel strategy for designing eco-friendly black mulch with reinforced mechanical strength, slow -release urea, soil moisture retention, and heat preservation performances.