Search Results (14)

Although there has been a notable increase in Life Cycle Assessment (LCA) studies in civil engineering, the field of Mechanically Stabilized Earth (MSE) with geosynthetics remains relatively underexplored. This research aimed to perform LCA together with a circularity analysis of countries that could represent the South American context. The materials and methods section covers an environmental analysis using LCA, spanning the manufacturing phase to the end of the structures of MSE with different geosynthetics, comparing Earth-Retaining Walls (ERWs), employing the ReCiPe method. Material circularity analyses for the three structures under consideration were performed using the Material Circularity Indicator (MCI). The proposed scenarios were conducted not only when recycled materials were introduced to replace virgin materials, but also when examining the concrete face and incorporating vegetation planting. The results suggest that MSEs can be environmentally more sustainable than ERWs. Therefore, the decreases were 80%in almost all categories. Furthermore, the material circularity analysis indicated that the incorporation of recycled materials increased the MCI, achieving 250% circularity for geosynthetics. Thus, it was inferred that the LCA methodology and circularity analysis effectively enabled qualitative and quantitative assessments. Notably, the findings highlighted the superior environmental sustainability of soil structures compared to their concrete counterparts. Full article

This study articulates findings from research pertaining to the utilisation of recycled geogrid in asphalt concrete. The issue of contamination of reclaimed waste with geosynthetic materials persists as a significant concern that warrants attention. In Poland, the allowable quantity of geogrid contaminants within the mineral–asphalt composition is 0.1% w/w. The preliminary evaluation of the validity of the research topic was conducted based on an analysis of correspondence and survey outcomes. The fundamental material research was executed employing elements of experimental design theory. The experimental domain considered two qualitative factors: the type of bituminous mixture for the binding layer (AC16W and AC22W) and the type of geogrid material (glass, carbon), in addition to two quantitative factors: the length of the recycled geogrid fibres ranging from 1 cm to 5 cm, and the quantity of recycled geogrid fibres varying from 0.2% to 1%. A generalised linear model was employed for the analysis, enabling the consideration of dependent qualitative factors in forecasting characteristics. The qualitative evaluation of the resultant solution was conducted using multi-criteria optimisation via the Harrington function. Consequently, recycled carbon mesh fibres demonstrated a notably positive impact, enhancing the material’s quality by 22%. Regarding glass mesh, the fibre content should not exceed 0.2% in the AC22W mixture, whereas it can be increased to 1% in the AC16W mixture. Comparing all evaluated mixtures, it was ascertained that surpassing the allowable contamination limit of 0.1% in geogrid form does not result in a significant reduction in the quality of asphalt concrete compared to the reference mix. Full article

To fulfill the modern concept of sustainable construction, the civil engineering community has shown increased interest in alternative options to replace natural backfills for engineering purposes. Since Recycled Construction and Demolition Waste (RCDW) has proven to be attractive in environmental, economic, and technical aspects, its behavior should be assessed considering its interaction with other construction materials, such as geosynthetics. Bearing in mind that the backfill affects the durability of geosynthetic materials, this study aims to assess the damage caused to geogrids by RCDW dropped by transportation (dump) trucks. Moreover, this study aimed to obtain an equation to predict the reduction factor caused by the backfill drop process. In an experimental facility, six RCDW materials (with different grain size distributions) were dropped (using a backhoe loader) from 1.0 m and 2.0 m heights over three distinct geogrids; the geogrid samples were exhumed and then tested under tensile loading. The results provided a database subjected to machine learning (Artificial Neural Network—ANN) to predict the reduction factor caused by the induced damage. The results demonstrate that the increase in drop height or potential energy cannot be directly associated with the damage. However, the damage increases as the maximum grain size of uniform gradation backfill increases, which is different from the results obtained from the fall of continuous gradation backfill. Moreover, since ANNs do not have any of the traditional constraints that multiple linear regression has, this method is an attractive solution to predict the geosynthetic reduction factors, providing relative errors lower than 8% compared to the experimental investigation reported in the study. Full article

Replacing natural aggregates in infrastructure with recycled construction and demolition waste (RCDW) works helps to meet the requirements established by sustainable development. This environmentally friendly proposal undoubtedly becomes better when it is carried out with geosynthetics, providing better technical performance and positive economic impacts. However, the chemical characteristics of RCDW may result in the degradation of the geosynthetics and, therefore, must be assessed and quantified. This study aims to assess the chemical degradation caused by RCDW for the mechanical properties of two types of polymeric geogrids (polyester and polyvinyl alcohol). The study evaluates the influence of the RCDW saturation condition in the chemical degradation and the possible synergism between the launching damage (drop height) and chemical degradation. Watertight tanks were constructed to maintain the geosynthetic reinforced layers in flooded, dry and open-to-environment conditions, simulating paved and unpaved roads. The occurrence of degradation was evaluated and quantified by reduction factors related to the properties of interest using statistical analysis. The results have shown a significant influence of chemical degradation on the geogrid characteristics (especially tensile strength and secant tensile stiffness), which increased when the specimens were subjected to prior launching process simulation. The reduction factor values reported herein encourage the combined use of these materials (geogrid and RCDW) and highlight the importance of assessing the chemical degradation for the design purposes of geosynthetic-reinforced roadways with alternative materials. Full article

Sustainability emphasises the importance of increasing the resource efficiency of infrastructure. The usage of geosynthetic materials in civil and environmental engineering can significantly influence sustainability at the planning and design stages of infrastructure construction projects. They are used in many different applications in construction and environmental engineering, as they provide a better and longer performance and less costly solutions than traditional materials (such as sand, gravel, concrete and cement). Additional benefits can be achieved by combining geosynthetics with various recycled materials as substitutes for high-quality natural materials. In this paper, the importance of sustainability in geosynthetics-based solutions is discussed. The possibilities of using geosynthetics in sustainable development have been analysed and the benefits resulting from their application, such as the reduction in carbon footprint and release of greenhouse gases and saving water and other natural resources, have been assessed. Innovative solutions that support mitigation measures, adaptation to climate change and achievement of sustainable development goals have been presented. Full article

Recycled construction and demolition (C&D) wastes have been pointed out as a feasible alternative to traditional backfill materials of geosynthetic-reinforced structures, but the current knowledge about the interface behaviour between these unconventional (recycled) materials and the reinforcement is still limited, particularly as far as the time-dependent response is concerned. In this study, a series of large-scale direct shear tests was conducted using an innovative multistage method to evaluate the influence of shear creep loading on the direct shear response of the interfaces between a fine-grained C&D material and two different geosynthetic reinforcements (high-strength geotextile and geogrid). The peak and large-displacement interface shear strength parameters obtained from tests involving sustained loading were compared with those from conventional interface tests. Test results have shown that the shear creep deformation of the interfaces increased with the magnitude of sustained loading. The test specimens experienced additional vertical contraction during the creep stage, which tended to increase with the applied normal stress. For the recycled C&D material–geotextile interface, the sustained loading induced a reduction in the apparent cohesion and a slight increase in the friction angle, when compared to the values estimated from conventional tests. In turn, for the geogrid interface, the apparent cohesion values increased, whereas the friction angle did not significantly change upon shear creep loading. Full article

Geotextiles, a group of high-performance materials, have grown during the last decades into needful auxiliaries when it comes to infrastructure, soil, construction, agriculture and environmental applications. Although geotextiles made of synthetic fibers (geosynthetics) are considered a modern achievement, the basic concept dates back to ancient times when textiles consisting of locally available natural fibers were employed to increase the stability of roads and soils. In recent decades, considering the growing interest in environmental protection and sustainable development based on using renewable resources and the recovery and recycling of waste of various origins, the use of natural fibers-based geotextiles is a viable alternative, despite their limited-life service owing to their biodegradability. In addition to this feature, their low cost, good mechanical properties and large-scale accessibility recommend them for geo-engineering applications, environmental sensitive applications in geotechnical engineering, such as land improvements and soil erosion control. This paper focuses on geotextiles as a versatile tool in environmental applications given their high theoretic and practical relevance as substantiated by recent literature reports. Natural and synthetic geotextiles are presented herein, as well as their features that recommend them for geo-engineering. Insights on the main types of applications of geotextiles are also included, along with a wide variety of materials employed to perform specific functions. Full article

The effects of the climate change that the planet has been experiencing, and the growing awareness of citizens that natural resources are finite, highlight the inevitability of making society more sustainable. Since the construction industry is responsible for a high consumption of natural resources and it simultaneously produces high volumes of waste, it is of great importance to investigate the feasibility of using construction and demolition (C&D) wastes as alternatives to common natural materials. This paper investigates the feasibility of using fine-grain recycled C&D wastes as backfill material of geosynthetic reinforced steep slopes, through a laboratory study focused mainly on the pullout behaviour of two geosynthetics embedded in these alternative materials. The influence of the geosynthetic type, moisture content and compaction degree of the recycled C&D material on the pullout behaviour is assessed and discussed. The physical and mechanical characterization of the filling material is also presented. The pullout test results have pointed out that, although the two geosynthetics have similar tensile strength, the pullout resistance of the geogrid is higher than that of the geotextile and is achieved at lower frontal displacements. While the reduction of the compaction moisture content below the optimum value induced a slight decrease in the geogrid pullout resistance (ranging from 5% to 7%), conversely the pullout capacity of the geotextile increased up to 22%. The compaction degree of the recycled C&D material had the expected effect on the geotextile pullout resistance, reflected in an increase of about 20% when the degree of compaction rose from 80% to 90%. However, the expected trend was not observed on the geogrid pullout behaviour. The pullout interaction coefficient tended to decrease with the variation of the compaction moisture content around the optimum value (maximum decrease of 33% and 16% for the geogrid and the geotextile, respectively) and with an increase in the vertical confining pressure from 10 kPa up to 50 kPa (decrease around 25%). The average value of the pullout interaction coefficient, fb, ranged from 0.61 to 1.09 for the geogrid and from 0.67 to 1.25 for the geotextile. From all these findings it can be concluded that recycled C&D materials can be seen as an environmentally friendly alternatives to the natural resources commonly used in the construction of geosynthetic-reinforced embankments. Full article

After years of using geosynthetics in civil engineering and infrastructure construction, it has recently become necessary to consider the possibility of recycling and reusing these materials. This paper presents the results of laboratory tests of the effect of recycled geogrid on the bearing capacity of soils using a CBR test. A polyester geosynthetic was selected for testing due to its high resistance to biodegradation and wide application. In a series of laboratory tests, two types of road and railway subgrade were used, mixed with geosynthetic cuttings in two different weight concentrations. The aim of the research was to demonstrate whether old demolition geosynthetics could be used to strengthen road and rail subgrade as recycled material. The influence of the geosynthetic cutting shape was also considered. The obtained results confirm the possibility of using recycled geogrid to improve the bearing capacity of the pavement subgrade, at least under these laboratory conditions. In the case of sand, the use of 2.0% additive causes that the poorly compacted soil obtains sufficient bearing capacity for the layer of road improved subgrade. As expected, the level of this improvement depends on the type of soil and the shape of geogrid cuttings. Full article

Geosynthetic-reinforced soil structures have been used extensively in recent decades due to their significant advantages over more conventional earth retaining structures, including the cost-effectiveness, reduced construction time, and possibility of using locally-available lower quality soils and/or waste materials, such as recycled construction and demolition (C&D) wastes. The time-dependent shear behaviour at the interfaces between the geosynthetic and the backfill is an important factor affecting the overall long-term performance of such structures, and thereby should be properly understood. In this study, an innovative multistage direct shear test procedure is introduced to characterise the time-dependent response of the interface between a high-strength geotextile and a recycled C&D material. After a prescribed shear displacement is reached, the shear box is kept stationary for a specific period of time, after which the test proceeds again, at a constant displacement rate, until the peak and large-displacement shear strengths are mobilised. The shear stress-shear displacement curves from the proposed multistage tests exhibited a progressive decrease in shear stress with time (stress relaxation) during the period in which the shear box was restrained from any movement, which was more pronounced under lower normal stress values. Regardless of the prior interface shear displacement and duration of the stress relaxation stage, the peak and residual shear strength parameters of the C&D material-geotextile interface remained similar to those obtained from the conventional (benchmark) tests carried out under constant displacement rate. Full article

Recycled rubber in granulated form is a promising geosynthetic material to be used in geotechnical/geo-environmental engineering and infrastructure projects, and it is typically mixed with natural soils/aggregates. However, the complex interactions of grains between geological materials (considered as rigid bodies) and granulated rubber (considered as soft bodies) have not been investigated systematically. These interactions are expected to have a significant influence on the bulk strength, deformation characteristics, and stiffness of binary materials. In the present study, micromechanical-based experiments are performed applying cyclic loading tests investigating the normal contact behavior of rigid–soft interfaces. Three different geological materials were used as “rigid” grains, which have different origins and surface textures. Granulated rubber was used as a “soft” grain simulant; this material has viscoelastic behavior and consists of waste automobile tires. Ten cycles of loading–unloading were applied without and with preloading (i.e., applying a greater normal load in the first cycle compared with the consecutive cycles). The data analysis showed that the composite sand–rubber interfaces had significantly reduced plastic displacements, and their behavior was more homogenized compared with that of the pure sand grain contacts. For pure sand grain contacts, their behavior was heavily dependent on the surface roughness and the presence of natural coating, leading, especially for weathered grains, to very high plastic energy fractions and significant plastic displacements. The behavior of the rigid–soft interfaces was dominated by the rubber grain, and the results showed significant differences in terms of elastic and plastic fractions of displacement and dissipated energy compared with those of rigid interfaces. Additional analysis was performed quantifying the normal contact stiffness, and the Hertz model was implemented in some of the rigid and rigid–soft interfaces. Full article

At the beginning of this century, due to well-established Brazilian recycling processes, geosynthetics’ manufacturers started to use recycled poly(ethylene) terephthalate (PET) yarns/filaments (from PET bottles) in geotextile production. Despite the fact that recycled products cannot act as reinforcement functions, geosynthetics are constantly under sustained tensile load and experiences evolutions of the axial strain (creep behaviour). Thus, this study aims to assess the influence of the structure of (needle-punched) non-woven geotextiles manufactured using recycled PET yarns on their creep behaviour. Two geotextiles with different fibre/filament production processes were investigated (short-staple fibres—GTXnwS—and continuous filaments—GTXnwC). Unconfined in-isolated conventional and accelerated (using the stepped isothermal method) creep tests were performed at 5%, 10%, 20%, 40% and 60% of geotextiles’ ultimate tensile strength. The geotextiles investigated provided similar creep behaviour to geotextiles manufactured with virgin PET material. The standard deviation of the axial strain tends to increase as the load level applied increase. The structure of the GTXnwS harms its tensile –strain behaviour, promoting axial deformation under sustained loads, at least 50% higher than GTXnwC for the same load level applied. The influence of the load level and geotextile structure in the initial axial strain is pointed out. Long-term predictions based on creep tests performed using the stepped isothermal method have proven to be conservative and they must be restricted for quality control of the investigated geotextiles. Full article

In recent years, environmental concerns related to the overexploitation of natural resources and the need to manage large amounts of wastes arising from construction activities have intensified the pressure on the civil engineering industry to adopt sustainable waste recycling and valorisation measures. The use of recycled construction and demolition (C&D) wastes as alternative backfill for geosynthetic-reinforced structures may significantly contribute towards sustainable civil infrastructure development. This paper presents a laboratory study carried out to characterise the interaction between a fine-grained C&D material and two different geogrids (a polyester (PET) geogrid and an extruded uniaxial high-density polyethylene (HDPE) geogrid) through a series of large-scale pullout tests. The effects of the geogrid specimen size, displacement rate and vertical confining pressure on the pullout resistance of the geogrids are evaluated and discussed, aiming to assess whether they are in line with the current knowledge about the pullout resistance of geogrids embedded in soils. Test results have shown that the measured peak pullout resistance of the geogrid increases with the specimen size, imposed displacement rate and confining pressure. However, the pullout interaction coefficient has exhibited the opposite trend with the specimen size and confining pressure. The pullout interaction coefficients ranged from 0.79 and 1.57 and were generally greater than or equal to the values reported in the literature for soil-geogrid and recycled material-geogrid interfaces. Full article