Raw earth bricks made from river sediments and natural fibers are essentially environmentally friendly bricks. They are made from river sediment waste and natural fiber waste, both of which are renewable resources. Sediment-based bricks have been formed from river sediment and flax fibers, the latter being considered as waste. Both types of waste are available in the same region. The study focused on the definition of water content by means of a miniature Proctor test, on the incorporation of short flax fibers of 2, 3 and 4 cm at various dosages and on the shaping by dynamic compaction of bricks of reduced size of 4 cm × 4 cm × 16 cm, dimensions similar to mortar specimens. The air-drying kinetics of the specimens were monitored from manufacture through to stabilization of their mass. The effects of water content, fiber content and fiber length were analyzed. Recommendations are given for the manufacturing and drying of green bricks and natural fibers.

The study focuses on the analysis of the microstructure on the short-term mechanical performance of sediment-based mortars, prepared with the sandy and clayey San Giuliano and Camastra reservoirs sediments, to minimize the use of natural resources and to reduce the cement quantity. The workability of mortars was first investigated according to the rate of incorporation of sandy and/or clayey sediments, with a mass ratio of 0.5 as a standardized mortar. This ratio increases to 0.64 when clayey sediment is incorporated in place of cement, if the clayey sediment is not considered as a binder. The influence of water quantity and of sandy and/or clayey lake sediment substitutions on the microstructure of these mortar mixes was analyzed by measuring the specific surface area, pore size, and volume for specimens. Different samples have been compared regarding adsorption/desorption hysteresis and pores network. It was found that mortars absorb more water than normalized mortar (MN), due to a larger specific surface area. MN is the reference cementitious mortar, manufactured with river sand, common used in constructions. The mechanical strengths are about half that of MN, except mortars E10 and E12. The replacement of part of the binder with the upstream clay material significantly affects mechanical strengths, unlike pore size distribution, pore volume and adsorbed volume, on which the impact is less pronounced. The relationship between mortars’ mechanical properties and microstructural characteristics shows that specific surface area is not a significant parameter. On the contrary, the pore size distribution is a key parameter for predicting the in situ mortars’ behavior: higher pore size values (> 25 Å) correspond to better workability and to higher mechanical strength, so that their use, with nonstructural functions, can be hypothesized for applications on site.

This paper investigates the improvement of earthen sediment-based bricks through the use of natural flax fibers to enhance their mechanical properties. The experimental tests were designed to develop numerical modeling based on material guidelines that have been partially followed. To facilitate the precise placement of flax fibers within the earthen sediment, periodically distributed holes have been deliberately made on both sides of the molds, ensuring the proper positioning of the flax fibers. The three-point bending test was conducted to assess the mechanical strength of the earthen bricks, providing insights into their stiffness and resistance to fracture. Non-linear numerical modeling was employed to gain a deeper understanding of fatigue behavior and crack propagation in earthen bricks under stress. The comparison of raw experimental data with numerical simulations validated the consistency of the results without adjustments, while the application of the homogenization principle improved data approximation. These findings confirm that the numerical homogenization method is the most effective approach for ensuring the validity of the numerical model and should be systematically applied to this type of problem.

The interruption of solid transport causes sediment deposition, compromising the useful storage capacity. Therefore, it is essential to remove these materials, currently labelled as waste and disposed of in landfills, by identifying alternatives for recovery and valorization, after assessing their compatibility for reuse through characterization, in a circular economy view. This study analyses the potential contamination of shore surface sediments collected at the Camastra and the San Giuliano lakes, located in the Basilicata region. It defines their potential ecological risk, assesses the contamination level status of the sediments, and verifies whether they are polluted and, consequently, suitable for reuse. Analyses carried out using several pollution indices show a slight Arsenic pollution (with values above the regulatory threshold between 55% and 175%) for the San Giuliano sediments and slight Cobalt pollution (with exceedances between 30% and 58.5%) for the Camastra sediments. Subsequently, through statistical analysis, it was possible to make hypotheses on the possible pollutant sources, depending on the geological characteristics of the sampling area and the type of land use, and to identify the potential ecological risk linked to the exceedance of As and Co in San Giuliano and Camastra reservoirs, respectively. In conclusion, this study ascertained the low pollution content in the sampled sediments, so they could be reused in various application fields, from construction to agriculture, significantly reducing landfill disposal.

This study presents a new laboratory apparatus for measuring and estimating the ability of shoveling, loading, and transport of fine soils and sediments. This device permits the investigation of the slump and sliding behavior of fine sediments based on their consistency and water content. Initially, a manual version of the apparatus was designed. The combined slump-sliding test (SST) and its use through a simple procedure were described in detail. Measurements done during tests on three different sediments and smooth steel support allow the presentation of the typical results obtained from the SST test. Because consistency governs the slump and sliding behavior of sediments, grain size distribution and Atterberg limits are the most useful characteristics of sediments. Typical relationships among slumps, cone footprints, and sliding rotation angle versus water content during moistening of sediments were established and explained. Based on these relationships, criteria for the ability to shovel sediments were proposed.

The management of sediments dredged and deposited on land has been the focus of many recycling studies, especially in laboratories where small quantities of sediments are oven-dried. These investigations have usually concluded that recovery as a material requires stabilization/solidification treatment. Few research studies are available for the sustainable, ecological and direct use of dewatered sediments, particularly on the compaction of raw sediments and the analysis of the different influences related to their texture, composition and drying methods. The present study investigates the compaction of raw dredged sediments for their potential reuse as fill material in the infrastructure projects. A series of 16 types of sediment from various environments, including rivers, dams and harbors, were compacted at an energy equivalent to that of the normal Proctor test. The test used a miniature laboratory version of the conventional Proctor test to estimate optimal compaction parameters. The results show that factors such as particle size, plasticity, specific gravity and organic matter content have a significant influence on optimum compaction values. Four distinct groups of sediments were identified, each with specific characteristics in terms of maximum dry density and optimum moisture content. The analysis first focused on the study of the influence of these factors (geotechnical properties) on the optimum compaction parameters in relation with organic matter content, for which a threshold of 5

This paper deals with the dewatering and handling of dredged sediments in the context of sustainability and renewability of natural resources. Dewatering is a critical part of sediment management, as the high water content of dredged sediments becomes a challenge for transportation, final storage and/or recycling. This is why it is necessary to reduce their water content before transportation. Conventional methods suggest using land-based drained basins, which is a sustainable solution. However, this solution has certain drawbacks: dewatering the sediment is time-consuming and involves the use of large land areas. The main problem with this method of dewatering can be solved by proposing mechanical dewatering in the vicinity of the dredging operation. Once the sediment has been sufficiently dewatered, it should be shoveled and transported again. The proposed paper covers the study of the dewatering and shoveling ability of sediments. After introducing why dewatering is a critical phase in the recycling process of sediment, some techniques for dewatering large volumes of high-water sediments are briefly reported. Typical dewatering laboratory tests are detailed, demonstrating their usefulness for understanding the mechanisms of natural dewatering. A laboratory dewatering press machine is reported and the procedure used for a sediment sludge. The last section concerns a recent innovative test implemented for the study of the shoveling ability and adhesion of sediments. This study improves our understanding of the phenomenon of sediment dewatering, for both natural and mechanical dewatering. It also provides the protocols for typical laboratory tests on sediment dewatering and shoveling ability.

Excessive consumption of natural resources to meet the growing demands of building and infrastructure projects has put enormous stress on these resources. On the other hand, a significant quantity of soil is excavated for development activities across the globe and is usually treated as waste material. This study explores the potential of excavated soils in the Brittany region of France for its reuse as earthen construction materials. Characterization of soil recovered from building sites was carried out to classify the soils and observe their suitability for earthen construction materials. These characteristics include mainly Atterberg limits, granulometry, organic matter and optimum moisture content. Soil samples were separated into fine and coarse particles through wet sieving. The percentage of fines (particles smaller than 0.063 mm) in studied soil samples range from 28% to 65%. The methylene blue value (MBV) for Lorient, Bruz and Polama soils is 1, 1.2 and 1.2 g/100 g, and French classification (Guide de terrassements des remblais et des couches de forme; GTR) of soil samples is A1, B5 and A1, respectively. The washing of soils with lower fine content helps to recover excellent-quality sand and gravel, which are a useful and precious resource. However, residual fine particles are a waste material. In this study, three soil formulations were used for manufacturing earth blocks. These formulations include raw soil, fines and restructured soil. In restructured soil, a fine fraction of soil smaller than 0.063 mm was mixed with 15% recycled sand. Restructuring of soil fine particles helps to improve soil matrix composition and suitability for earth bricks. Compressed-earth blocks of 4 × 4 × 16 cm were manufactured at a laboratory scale for flexural strength testing by using optimum molding moisture content and compaction through Proctor normal energy. Compressive strength tests were performed on cubic blocks of size 4 × 4 × 4 cm. Mechanical testing of bricks showed that bricks with raw soil had higher resistance with a maximum of 3.4 MPa for Lorient soil. Removal of coarse particles from soil decreased the strength of bricks considerably. Restructuring of fines with recycled sand improves their granular skeleton and increases the compressive strength and durability of bricks.

The damming of watercourses results in sediment accumulation and, therefore, in the reduction of useful storage capacity. The storage capacity can be recovered through dredging, but this process generates large volumes of sediments that require proper management. To avoid landfilling and promote recovery operations, sediment characterization is the preliminary step to any assessment and decision. This paper presents the results of tests on sediments sampled at two reservoirs in southern Italy, the Camastra and the San Giuliano, in Basilicata. These investigations include testing of organic matter, heavy metals grain size distribution, and the assessment of the pollution degree. A lack of correlation between the sampling point and the heavy metal content was observed in sediments, except Be, Cr and Ni for the San Giuliano reservoir. This may be attributed to the presence of agricultural activities and fertilizer use in its watershed. Similarly, there is no dependence between the organic carbon and the grain size distribution, the former being scarcely found in both reservoirs (on average 0.91% for the Camastra sediments and 0.38% for the San Giuliano sediments), the latter being predominantly characterized by sandy matrices downstream of the reservoirs (on average 64.3% ± 32.9%) and by silty-clayey matrices in the upstream areas (on average 65% ± 14.3%). Finally, the determination of the single pollution index Pi and the Nemerow integrated pollution index PN highlights that sediments are not contaminated with heavy metals. Most of them show values of the indices above between 0 and 1 (“unpolluted”) and, in a few cases, values between 1 and 2 (“poorly polluted”). The findings suggest that these sediments can be reused for environmental and material recovery, using them as secondary raw materials for sub-bases and embankments, for filling in disused quarries, for reprofiling and reconstructing the morphology of coastlines or riverbeds, for beach nourishment and in the agronomic and construction industry fields.

The production of construction and demolition waste (CDW) in urban areas is growing rapidly. While the storage and disposal of CDW waste is costly, its recovery can help to conserve natural resources. This study investigates the characteristics of recycled sand obtained from the processing of CDW waste and the possibility of its reuse for pedestrian pathways. Physico-chemical and mineralogical characteristics of the recycled sand were investigated for its reuse. The percentage of fine particles in sand (below 0.63 μm) is 2.8%. The grain size of sand fulfills the particle size requirement of French standards. The methylene blue value of sand is 0.05 g/100 g. The GTR classification of recycled sand is D2 which is insensitive to water and suitable for road applications. A mineralogical analysis of soil shows that quartz, albite and microcline are important minerals in recycled sand. XRF analysis shows that CaO and SiO2 are major oxides in the recycled sand. The characterization of sand was followed by a manufacturing of cylindrical specimens of sand to observe the compressive strength. Samples were compacted with dynamic compaction by applying the Proctor normal energy of 600 kN·m/m3. The compressive strength testing of specimens shows that non-stabilized sand samples have compressive strength around 0.1 MPa which is considerably lower for its reuse in pedestrian pathways and road applications. Due to the low bearing capacity of sand, recycled sand was stabilized with the addition of binders such as Rolac (hydraulic binder), ground-granulated blast furnace slag (GGBS) and ECOSOIL® (slag mixes) with different percentages of the binder ranging from 0 to 7% for the optimization of the binder and for economic efficiency. The compressive strength of sand samples increases with the increasing percentage of the binder. The increase in strength is more important with a higher percentage of binders (5%, 6% and 7%). At a 7% binder addition, specimens with Rolac, GGBS and ECOSOIL binders show the compressive strength of 1.2 MPa, 0.5 MPa and 0.5 MPa. At a 7% Rolac addition, specimens have a compressive strength higher than 1 MPa and meet the strength requirement for soil reuse in the foundation and subbase layers of roads with low traffic. The experimental work shows that recycled sand can replace conventional quarry sand for road applications and pathways with the addition of a local binder, which is an eco-friendly and economical practice.

The shaping of raw earth reinforced with natural fiber waste poses problems in the distribution of fibers and the homogeneity of the composite material. These same problems are encountered when making laboratory specimens and the scale effect. These specimens must be as homogeneous and reproducible as possible. As part of a specific study on the reinforcement of mud bricks with natural fiber waste, prismatic test specimens were prepared. The dimensions used are those of standard mortar specimens, i.e., 4 × 4 × 16 cm3. These specimens can also be subjected to indirect bending tensile tests like mortars. The data resulting from the test allow the influence of the incorporation of fibers into the raw earth to be analyzed. The shaping of the specimens requires, first of all, the development of a rigorous and repetitive mixing procedure. Then follow the filling of molds and compacting of the volume of reinforced raw earth within the mold. To make the compaction procedure repetitive, a compaction system adapted to the selected mold (4 × 4 × 16 cm3) was used to compact the reinforced raw earth specimen at controlled energy. This procedure is indeed repetitive. The choice of this dynamic compaction method was preferred to impact or tamping compaction or static compaction. The level of energy applied is adjustable and can be equivalent to that required for a normal or modified Proctor test in the case of stabilized soils. The control of the fiber distribution within the specimen makes it possible to judge the specimen's homogeneity and the fibers' good distribution. A procedure for counting the fibers in a cross-section of the specimen is proposed. All these procedures (mixing, filling, compacting, and fiber distribution) are presented and discussed when making prismatic sediment (raw earth) specimens reinforced with natural fibers (hemp). The method of compaction is also detailed.

The mechanical characterization of natural fiber waste poses problems concerning the preparation of the fibers and their isolation to characterize them. Fibers are available in various forms: in the form of bunches (oil palm fibers), shells (coconuts), dried blocks (banana spines), entangled crushed fibers (sugar cane), etc. Isolating a fiber or bundle of fibers requires a procedure for the preparation of fiber waste which involves cutting the fibers to length. This cutting can be manual in the laboratory but must be mechanized from an industrial point of view. But the mechanically lengthened fibers are either crushed or cut, which changes their structure and affects their mechanical properties. Once insulated, the fibers can be subjected to mechanical tests such as the tensile test, which is a reference test in studies of fiber-reinforced materials. A procedure for this direct tensile test is used. The analysis of the results requires knowledge of the fiber geometry, especially the cross-section. This cross-section can be defined by direct measurement or by image processing. Both methods were applied to a set of tropical fiber wastes of Mexican origin, i.e., oil palm, sugar cane, coconut, and banana rachis fibers. These fibers were subjected to a tensile test to determine their mechanical characteristics (ultimate strength, rate of deformation at failure) and behavior. All the data acquired on these fibers are analyzed, discussed, and compared with those in the literature. This is followed by a description of their behavior and a proposal for modeling from a rheological point of view.