The Influence of External Sulfate Attack on the Durability of Reinforced Mortars in the Presence of Calcined River Sediments.

In France, the annual volume of dredged sediments is significantly increasing, which has become a real environmental problem. Nevertheless, these sediments can be used beneficially as supplementary cementing material. On the other hand, external sulfate attack is one of the most aggressive causes of deterioration that affects the durability of concrete structures. This study focused on the valorization of river-dredged sediments from Noyelles-Sous-Lens (Hauts-de-France) as a mineral addition in substitution of Portland cement, and it studied their impacts on the mechanical behavior and durability of reinforced mortars. X-ray diffraction (XRD) analysis indicated the presence of clay minerals in the raw sediment. In order to activate this clay fraction, flash calcination was applied at a temperature of 750 °C. In addition, four mixed mortars were formulated by mixing a Portland cement (CEM I 52.5 N) and the calcined sediments as a partial substitute for cement with proportions of 0%, 15%, 20%, and 30%, then stored in water tanks at room temperature (20 ± 2 °C) for 90 days in order to immerse them in a tank containing a 5% MgSO4 solution and to track the evolution of their corrosion potential as well as their mass variations every 20 days for a period of 360 days. The following additional tests were carried out on these mortars: tests of resistance to compression and flexion and to porosity by mercury intrusion. The results obtained from the majority of these tests showed that the mortar containing 15% calcined sediments is as effective and durable as the reference mortar itself. The main conclusion we can draw from these results is that the presence of these calcined sediments improves the overall behavior of the mortar.

Assessment of Dynamic Surface Leaching of Monolithic Polymer Mortars Comprised of Wastes.

Today, the reuse of waste in building materials occupies an important place in the approach to the circularity of materials. National and European environmental regulations require ensuring the environmental safety of material-incorporating waste. For this, there are specific tests to verify that there is no health risk when using these materials. Concretely, to check the environmental acceptability of construction materials, including wastes, the release of hazardous substances into water must be assessed. In this research, we performed a diffusion test with the sequential renewal of water during a 64-day period according to the NF EN 15863 specifications on polymer mortar monoliths, common construction products used in floor-covering applications and incorporating sediments. Polymer mortars were prepared at a laboratory scale by incorporating 30 or 50% of polluted sediment for various polymer concentrations (12, 14, 16, 18, 20 and 25%). It was shown that the release of inorganic substances is limited in these hydrodynamic conditions. Among trace elements, As, Cd, Cr, Ni, Pb and Zn are lower than quantification limits in most leachates, whereas Ba, Co, Cu and V are systematically quantified at low concentration levels. This is particularly true for samples displaying the highest polymer concentration (25%) and the lowest sediment incorporation rate (30%). This is because of the low water absorption level and low porosity of polymer mortar matrices. No adverse effect is to be expected for environmental health from the leachates of these construction materials, including waterways sediments, because all the measured parameters were below the Soil Quality Decree limits applied in the Netherlands for environmental assessment of construction products.

Managing the Heat Release of Calcium Sulfoaluminate Cement by Modifying the Ye'elimite Content.

Nowadays, calcium sulfoaluminate cement (CSA) is garnering a large amount of attention worldwide and is being promoted as a sustainable alternative to Portland cement for specific applications. This study aimed to control the heat release of CSA cement paste by choosing the appropriate composition. For this purpose, different calcium sulfoaluminate clinkers with up to 75 wt. % of ye'elimite were synthetized. Then, a reactivity study on the synthesized clinkers was conducted while varying the amount of gypsum added. The heat of hydration was measured by isothermal calorimetry. The influence of the ye'elimite content on the heat release and on the compressive strength was investigated. According to the findings, the amount of ye'elimite in the cement has a direct relationship with the heat release. The heat release as well as the mechanical performance increase with the increase in the ye'elimite content in the CSA cement. An equation allowing the prediction of the total heat release after 24 h is provided. Such data can be of particular interest to consultants aiming at the reduction of thermal cracking in massive concrete.

Prediction of the Compressive Strength of Waste-Based Concretes Using Artificial Neural Network.

In the 21st century, numerous numerical calculation techniques have been discovered and used in several fields of science and technology. The purpose of this study was to use an artificial neural network (ANN) to forecast the compressive strength of waste-based concretes. The specimens studied include different kinds of mineral additions: metakaolin, silica fume, fly ash, limestone filler, marble waste, recycled aggregates, and ground granulated blast furnace slag. This method is based on the experimental results available for 1303 different mixtures gathered from 22 bibliographic sources for the ANN learning process. Based on a multilayer feedforward neural network model, the data were arranged and prepared to train and test the model. The model consists of 18 inputs following the type of cement, water content, water to binder ratio, replacement ratio, the quantity of superplasticizer, etc. The ANN model was built and applied with MATLAB software using the neural network module. According to the results forecast by the proposed neural network model, the ANN shows a strong capacity for predicting the compressive strength of concrete and is particularly precise with satisfactory accuracy (R² = 0.9888, MAPE = 2.87%).

Designing Efficient Flash-Calcined Sediment-Based Ecobinders.

To ensure the optimum navigation of boats and protection against flooding, waterways and ports are regularly dredged. The volume of dredged materials represents 56 million m3 in France and 300 million m3 in Europe. These materials show a high potential for a use as supplementary cementitious material (SCM). In this paper, sediments treated by the flash calcination method (STFC), which is based on a low-energy consumption process, are utilized as a mineral admixture in a cementitious matrix. The results of the physical, chemical, and mineralogical characterization prove that this heat treatment has an interesting impact on the final properties of the sediments. Mortars based on the flash-calcined product have comparable mechanical properties to control mortar. For a substitution rate below 10%, the performances are even equivalent to a metakaolin (MK80)-based mortar. Calorimetry testing demonstrated that calcined materials also improve hydration processes in the cement matrixes by generating additional heat release due to sediment pozzolanic activity. Across this study, it is shown that waste material including sediment can be transformed after optimized heat treatment into a valuable resource for the building and infrastructure sector.

Reuse of treated wastewater and non-potable groundwater in the manufacture of concrete: major challenge of environmental preservation.

This work concerns the reuse of treated wastewater from Er-Rachidia wastewater treatment plant (WWTP) in the mixing of ordinary C20/25 concrete, to reduce the overexploitation of non-potable groundwater, avoid its discharge into watercourses and reduce the risk of environmental pollution due to its mineral and organic matter load. In this respect, three types of mixing water were used in this study: drinking water (DW), non-potable groundwater (GW), and treated wastewater (TW). The results recorded for each type of mixing water, in the fresh and hardened state of concretes, were compared with the requirements of the standards. The obtained results show that the treated wastewater does not have any adverse effect upon the quality of the concrete; it has shown an improvement of the mechanical strength from the first stage, a similar density, setting time, and porosity and a slight decrease of the workability compared with the control concrete. A one-way analysis of variance (ANOVA) of the mechanical performance of concrete at different cure times (7, 14, 28, and 90 days) has shown that there is no significant decrease in the mechanical performance of concretes based on TW and GW compared with concretes formulated with DW. Through this study, the substitution of drinking water by treated TW and GW will help to minimize the footprint of construction materials on natural resources. From a point of view of the mechanical performance, TW and GW improve the mechanical performance of concrete. Additionally, it makes wastewater treatment plants more economically attractive and contributes to sustainable development.

Storage facilities reclamation using dredged sediments from waterways: Growing media formulation for plants according to the EU Ecolabel requirements.

Dredged sediments display a great potential for growing media applications; however, there are few studies about their beneficial reuse for the waste storage reclamation. This research study aims at checking the agronomic values and environmental impacts of three growing media based on waterways sediments (WSs) and green waste (GW) according ecolabel requirements. For this purpose, three growing media named GW0, GW25, and GW50 were prepared at field pilot scale by co-composting WS and GWs during 12 months. Samples were submitted to ecolabel analyses package. Following to the ecolabel requirements, the growing media comply with criteria like pH, electrical conductivity, trace elements and polycyclic aromatic hydrocarbon contents, chlorides, and pathogens, whereas they are not in compliance with the EU Ecolabel guidelines for propagules, organic matter, and zinc contents. Results of laboratory leaching tests performed according to NF EN 12457-2 for GW0, GW25, and GW50 have shown that sulfates, soluble fraction exceed limit for inert waste storage. Lysimeter tests at pilot scale were performed during 6 months to check the leaching potential of pollutants from growing media under real field conditions, including a European ecolabel product. Results demonstrate that Ba, Mo, Sb, Zn, Se, and Sb are higher in GW0, GW25, and GW50 than in the European ecolabel. As, Cd, Cr, Ni, and F- are more soluble in the commercial product compared to other growing media. This study allowed to demonstrate that main characteristics are fulfilling for reusing these growing media in the specific field of waste storage reclamation.

Environmental assessment, mechanical behavior, and chemical properties of self-compacting mortars (SCMs) with harbor dredged sediments to be used in construction.

Environmental and ecological issues have led to the development of new sustainable channels for the recovery of dredged sediments. One of the major difficulties of sediment valorization lies in particular in its very heterogeneous composition. For example, the presences of heavy metals and organic matter have a significant influence on the environmental impact of materials formulated with sediment. Some heavy metals such as antimony, mercury, lead, and cadmium in high concentrations are dangerous to the body. Trace metals trapped in sediments are transformed through complex biogeochemical processes. They subsequently associate with organic matter to form clay-humic groups that define the degree of sediment pollution. The Harbour Dredging Sediments (HDSs) used were classified as non-hazardous waste in accordance with Directive 12/12/14/EC. The purpose of this study is to evaluate the environmental impact of the use of HDS from active lagoon in the formulation of self-compacting concrete (SCC) with the objective of incorporating a high sediment content, obtaining materials with a low environmental impact and ensuring compressive strength of a C25/30 class concrete. Three HDSs are being studied that have a significant impact their difference by their fines content at 125 µm. Sediments recovered from the active lagooning process have not undergone any physical, chemical, or thermal treatment. The DMDA (Densified Mixture Design Algorithm) method is used to optimize the composition of "sediment" SSCs. The communication focuses on mortars equivalent to these "sediment" SCCs (SCMs). Sediment represents about 20% of the granular composition with a sediment-to-cement ratio of 80%. Compressive strengths are greater than 25 MPa and tensile strengths are in the range of 3 to 8 MPa at 28 days of curing. From an environmental point of view, all heavy metals are stabilized except nickel. In particular, there has been a considerable decrease in the levels of sulfate, total organic carbon, and chloride. The different SCMs are classified as inert, clinker hydration produces hydrates that capture and stabilize heavy metals in the cementitious matrix. The results obtained show that HDSs could be used as a secondary raw material in the formulation of self-compacting concretes.

An eco-friendly epoxy polymer binder for the treatment of Tunisian harbor sediments: Laboratory investigations for beneficial reuse.

The management of dredged sediments poses serious environmental and economic problems because of their geochemical properties and in particular their pollutant content. In this research, marine sediments from Tunisian harbors were collected to study their beneficial reuse as construction materials using an eco-friendly polymer binder. Experimental investigations include the determination of physicochemical, mineralogical, and environmental parameters of sediments from the Sidi Mansour and Sidi Youssef areas in Tunisia. Prismatic mortar samples (4 × 4 × 16 cm) were prepared at laboratory scale using normalized sand and epoxy resin. Then their composition was modified by including a sediment fraction in the substitution of sand at rates ranging from 10 to 50% in dry mass. After a 7-day curing period, mortar samples were submitted to mechanical, physicochemical, and environmental analyses. Mortar samples including sediment fractions displayed lower strength than sand mortar used as control. This result is explained by the increase of porosity values in the mortar samples when sediment samples were incorporated. A positive relationship between porosity and compressive strength values was evidenced, suggesting that the compactness of granular skeleton could play an important role in the preparation of materials. From an environmental point of view, the mortar samples containing sediment fractions showed relatively low leaching levels, which confirms their suitability for the manufacturing of construction materials.

Assessing temporal variability and controlling factors of the sediment budget of a small agricultural catchment in Northern France (the Pommeroye).

A high-frequency monitoring station was implemented at the outlet of the small catchment of the Pommeroye (0.54 km2) in Northern France to study erosion by runoff and hydro-sedimentological responses to heavy rainfall events in the context of Quaternary loess deposits. The aim of this experimental work is to assess the temporal variability of sediment yield and to identify the factors controlling the hydro-sedimentary response. To achieve this goal, statistical and hydro-sedimentary dynamic analyses were performed. During two years of monitoring (April 2016-April 2018), 48 flood events were recorded. The specific sediment yield (SSY) is highly variable and was evaluated to 29.4-70 t km-2 yr-1 which is conventional for the study region. Most of the sediment yield was produced in winter (55%) and autumn (42%). Only 3% of SSY were produced during spring and summer periods. According to our results, only 6% of the erosive events are responsible for the transport of more than 40% of the sediment flux recorded at the outlet. This underlines the temporal variability of the hydro-sedimentary production in small agricultural catchments for which most of the hydro-sedimentary flux is produced during a limited number of events. The results of statistical analyses show that the total amount of rainfall and the duration of a rainfall episode are the main controlling factors on the hydro-sedimentary response. Our results also suggest that the rainfall kinetic energy better reflects the sediment detachment, and that the 48 h-antecedent rainfall is not linked to the hydro-sedimentary response.

Quantification of tributaries contributions using a confluence-based sediment fingerprinting approach in the Canche river watershed (France).

Since a few years, land use management aims to reduce and control water erosion processes in watersheds but there is a lack of quantitative information on the contribution of the sources of transported sediment. This is most important in agricultural areas where soils are sensitive to erosion. The geology of these areas is often characterized by large expanses of relatively homogeneous quaternary silts. The possibility of distinguishing the sources of erosion according to their geological substratum is thus very delicate. This information is important because its lack can lead to the mis-implementation of erosion control measures. To address this request, a confluence-based sediment fingerprinting approach was developed on the Canche river watershed (1274 km2; northern France), located in the European loess belt, an area that is affected by diffuse and concentrate erosion processes. Suspended particulate matter was collected during five seasonal sampling campaigns using sediment traps at the outlet of each tributary and confluence with the main stream of the Canche river. The final composite fingerprint was defined using physico-chemical and statistical analyses. The best tracer parameters for each tributary were selected using stepwise discriminant function analyses. These parameters were introduced into a mass balance mixing model incorporating Monte-Carlo simulations to represent the uncertainty. Estimates of the overall mean contributions from each tributary were quantified at different temporal scales. The annual sediment flux tributaries contributions range from 3 to 22% at the outlet of the Canche river, and annual sediment flux range from 0.87 to 40.7 kt yr-1. The Planquette and the Créquoise tributaries appear to be those producing the largest sediment flux. In contrast, tributaries with the highest number of erosion control on their area exhibit the lowest values of sediment flux. Our results indicate a positive impact of recent land management policies in the Canche river watershed.

Beneficial reuse of Brest-Harbor (France)-dredged sediment as alternative material in road building: laboratory investigations.

The scarcity of natural aggregates promotes waste reuse as secondary raw material in the field of civil engineering. This article focuses on the beneficial reuse of marine-dredged sediments in road building. Thus, mixtures of raw sediments and dredged sand collected from Brest Harbur (Bretagne, France) were treated with road hydraulic binders. Formulation were prepared and characterized as recommended by the French Technical Guidelines for soil treatment with lime and/or hydraulic binders. Mechanical resistance results are quite similar for both the hydraulic binders, suggesting a similar reactivity with the studied sediment sample. However, some discrepancies can be noted on sustainability parameters. Indeed, water resistance after immersion at 40°C is significantly better for the mixtures treated with cement containing more glass-forming oxides (SiO2 + Al2O3) and fluxing (Fe2O3+CaO + MgO + K2O + Na2O). Moreover, the both hydraulic binders can lead to swelling in the road materials as observed in scanning electron microscopy analyses. Indeed, microscopic observations indicated volumetric swelling of treated samples, which is greatly influenced on the one side by ettringite quantity and on the other hand by the presence of water in pores material.

Mechanical behavior of municipal solid waste incinerator bottom ash: Results from triaxial tests.

Bottom ash resulting from the incineration of various domestic wastes can be viewed as a typical granular material. It is mainly used in civil engineering as a substitute for traditional natural aggregates. The purpose of this paper is to characterize their mechanical behavior and evaluate their mechanical properties for engineering applications. First, results of triaxial tests confirm that bottom ash behaves like dense sand. Second, the deformation and strength characteristics of bottom ash, such as the secant modulus, Poisson ratio, characteristic angle, dilation angle, effective cohesion and effective friction angle, are determined. It is found that these mechanical parameters are in close agreement with those of road aggregates and are influenced by the effective confining pressure. Third, the evolution of the deformation modulus according to the axial strain and the variation of the deviator stress according to the mean effective pressure are analyzed. Finally, a set of points of the yielding state is determined from triaxial tests to represent the shape of the yielding surface of bottom ash.

Relationship between the water-exchangeable fraction of PAH and the organic matter composition of sediments.

The sorption of PAH on 12 different sediments was investigated and was correlated to their corresponding organic matter (OM) content and quality. For this purpose, the OM was precisely characterized using thermal analysis consisting in the successive combustion and quantification of the increasingly thermostable fractions of the OM. Simultaneously, the water-exchangeable fraction of the sorbed PAH defined as the amount of PAH freely exchanged between the water and the sediment (by opposition to the PAH harshly sorbed to the sediments particles) was determined using a passive sampler methodology recently developed. The water concentrations, when the sediment-water system is equilibrated, were also assessed which allows the determination of the sediment-water distribution coefficients without artifacts introduced by the non water-exchangeable fraction of PAH. Hence, the present study provides the distribution coefficients of PAH between the water and 4 different OM fractions combusted at a specific temperature range. The calculated distribution coefficients demonstrate that the sedimentary OM combusted at the intermediate temperature range (between 300 °C and 450 °C) drives the reversible sorption of PAH while the inferred sorption to the OM combusted at a lower and higher temperature range does not dominate the partitioning process.

Valorization of unauthorized sea disposal dredged sediments as a road foundation material.

The main objective of this study is to show the ability of fine dredged material (mainly silty material) to be used in road construction project. This paper is divided into three parts. In the first part, the physical, the mineralogical and the mechanical characteristics of the used fine dredged sediments, as well as their chemical composition and environmental impacts are presented. In the second part, the methodology developed to design the road made from dredged fine sediment is developed. The third part of the paper focuses on the presentation of the road construction and the interpretation of analyses made on cores drilled samples from the road and measurements of the deflection of the road. The environmental assessment, based on leaching tests, is also performed at different issues.

Experimental investigation on consistency limits of cement and lime-stabilized marine sediments.

This paper presents the effects of treatments with cement and lime on the consistency limits of marine sediments dredged from Dunkirk port. The Casagrande percussion test and the fall cone test were used to determine the liquid limits of raw sediments and treated marine sediments. For the evaluation of the plastic limits, the results of the fall cone test were compared with those obtained by the rolling test method. The relationship between the water contents and the penetration depths for the determination of the liquid limit and the plastic limit was explored. Liquid limits at 15.5 mm and plastic limits at 1.55 mm seem to be a more appropriate choice for the studied marine sediments compared with the limits determined by other used prediction methods. Finally, the effect of cement treatment and lime treatment on the Casagrande classification of the studied sediments was investigated according to the different prediction results.

Solidification/stabilization of dredged marine sediments for road construction.

Cement/lime-based solidification is an environmentally sound solution for the management of dredged marine sediments, instead of traditional solutions such as immersion. Based on the mineralogical composition and physical characteristics of Dunkirk sediments, the effects of cement and lime are assessed through Atterberg limits, modified Proctor compaction, unconfined compressive strength and indirect tensile strength tests. The variation of Atterberg limits and the improvement in strength are discussed at different binder contents. The potential of sediments solidified with cement or lime for road construction is evaluated through a proposed methodology from two aspects: I-CBR value and material classification. The test results show the feasibility of solidified dredged sediments for beneficial use as a material in road construction. Cement is superior to lime in terms of strength improvement, and adding 6% cement is an economic and reasonable method to stabilize fine sediments.

Formulation of artificial aggregates from dredged harbour sediments for coastline stabilization.

Coastal erosion is a common phenomenon along the shores of the member states of the European Union. In 2004, approximately 20,000 km of coastlines, accounting for 20% of the whole of the EU coastline, were considered particularly affected by this phenomenon. Coastal erosion and shoreline retreat already affect a significant proportion of the French coast, the beaches in the north of France being no exception, and will probably increase during the 21st Century because of climate change. Because erosion is often accentuated by sedimentary deficits, artificial beach replenishment often represents an appropriate engineering solution for coastline stabilization. Meanwhile, large quantities of sediments are dredged every year from ports, with approximately 25 to 45 million tons of sediments (dry matter) per year being dredged for the maintenance of harbours. The purpose of the study presented in this article is to report on the potential use of artificial aggregates formulated with harbour sediments in order to recharge beaches and/or nearshore environments. The manufacture of the aggregates consisted of several stages, beginning with the characterization and the preparation of the sediment before the fabrication of aggregates by extrusion, associating the sediments with a specific hydraulic binder. Various parameters, such as water content of the mixing sediment, the cement content and the shape of the aggregates, were taken into account, in order to ensure the criteria regarding the strength of these aggregates are entirely fulfilled. The first simulations in a wave flume are encouraging and reveal the possibilities for use of the aggregates in coastal engineering.

Monotonic aspects of the mechanical behaviour of bottom ash from municipal solid waste incineration and its potential use for road construction.

Municipal solid waste incineration (MSWI) bottom ash is an atypical granular material because it may include industrial by-products that result from the incineration of domestic waste. The prospects for the beneficial use of this particular material mainly lie in the field of road construction, as a substitute for the traditional natural aggregates. However, its mechanical properties are still little known, particularly in term of stiffness and deformability, characteristics that are essential to the construction of a durable roadway. The purpose of this paper is to describe better the mechanical behaviour of this recycled material. In order to reach this objective, a large experimental campaign is presented. The first part of this paper presents and comments in detail on the results obtained from static monotonic tests. Oedometric and triaxial shear tests were performed on MSWI bottom ash both before and after treatment with a specific hydraulic binder. These tests allow specification of the mechanical characteristics of the MSWI bottom ash, such as the initial Young's modulus, Poisson's ratio, the compressibility index, the friction angle, and the contracting or dilating behaviour of the material. The results reveal a mechanical behaviour similar to that of initially dense standard materials (sands, unbound granular materials) and a dependence on the applied average pressure, characteristic of the mechanical behaviour of granular media. More laboratory data on other samples of MSWI bottom ash are required to ensure that this comparison is statistically valid.