A state-of-the-art review on the application of lignosulfonate as a green alternative in soil stabilization.

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 eco-friendlier 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.

Experimental investigation of the effect of landfill leachate on the mechanical and cracking behavior of polypropylene fiber-reinforced compacted clay liner.

This paper aims to investigate the effect of leachate on the geotechnical parameters and the cracking behavior of compacted clay liners (CCLs) containing different percentages of polypropylene fibers. Accordingly, 200 compacted clay samples were reinforced with different percentages of fiber contents (FC) (i.e., 0, 0.5, 0.75, and 1%) and prepared with water or leachate to conduct different laboratory tests. First, the physical properties of the clay were determined. Then, the shear strength parameters (i.e., cohesion and friction angle), unconfined compressive strength, and the hydraulic permeability were determined subjected to water or leachate. Notably, the cracking behavior was modeled using visual images of the samples. The leachate increased desiccation cracks in the natural soil from 0.425 to nearly 1.111%. However, the addition of 0.5% (in the case of water) and 1% (in the case of leachate) fiber to the soil reduced the surface desiccation cracks in clay liners to about 0.185 and 0.352%, respectively. In both water- or leachate-prepared samples, the addition of fibers significantly increased the cohesion and friction angle. The shear strengths of the unreinforced leachate-prepared samples were lower than those of the water-prepared samples. The shear strength and unconfined compressive strength of all specimens increased with increasing fiber percentage. The presence of fibers in all samples caused more ductile behavior. The required amount of energy to achieve the maximum strength in the samples increased with increasing FC. By increasing the percentage of fibers, the permeability of the natural soil and the leachate-prepared samples increased. However, the highest permeability was observed in the leachate-prepared samples containing 1% fibers of 8.3 × 10-10 m/s, which is less than 10-9 m/s (maximum allowable permeability for clay liners). Finally, the obtained results were satisfactorily confirmed by scanning electron microscopy (SEM) analysis.

Application of the dynamic cone penetrometer test for determining the geotechnical characteristics of marl soils treated by lime.

Quantitative estimation of mechanical characteristics of soils and determination of their behavior using in-situ experiments have always been one of the main concerns of geotechnical engineers. So far, various methods have been introduced to achieve this goal, among which the Dynamic Cone Penetrometer (DCP) test has become more popular as one of the most accurate and efficient methods. Therefore, in this study, an attempt was made to examine the correlation between different soil parameters by performing DCP test along with a series of conventional tests including Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) tests on marl soil samples containing 2, 5, 8% lime at 1, 7 and 15 curing days. Furthermore, since the subgrade reaction coefficient (Ks) is needed in the design of pavements and their underlying materials, Plate Load Test (PLT) was performed to determine Ks. The results showed that the addition of lime up to 5% increased UCS, CBR and Ks and decreased dynamic penetrometer index (DPI) of marl soil samples. Further addition of lime had a negative effect on the mechanical characteristics of the samples. Moreover, using the equations obtained from the correlations in this study, strength characteristics and subgrade reaction coefficient of the stabilized marl soil can be estimated by knowing the DPI of the samples. The results of this study showed that the use of the DCP test as a cheap and easy-to-use method can provide a comprehensive view of soil behavior in civil engineering projects with an acceptable coefficient of determination to geotechnical engineers.

Damage source identification of reinforced concrete structure using acoustic emission technique.

Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures.

Investigating the effect of lignosulfonate on erosion rate of the embankments constructed with clayey sand.

Internal erosion is known as the most important cause of dam failure after overtopping. It is important to improve the erosion resistance of the erodible soil by selecting an effective technique along with the reasonable costs. To prevent internal erosion of embankment dams the use of chemical stabilizers that reduce the soil erodibility potential is highly recommended. In the present study, a lignin-based chemical, known as lignosulfonate, is used to improve the erodibility of clayey sand specimen. The clayey sand was tested in various hydraulic heads in terms of internal erosion in its natural state as well as when it is mixed with the different percentages of lignosulfonate. The results show that erodibility of collected clayey sand is very high and is dramatically reduced by adding lignosulfonate. Adding 3% of lignosulfonate to clayey sand can reduce the coefficient of soil erosion from 0.01020 to 0.000017. It is also found that the qualitative erodibility of stabilized soil with 3% lignosulfonate is altered from the group of extremely rapid to the group of moderately slow.