Rachid Zentar

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.

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 Youngs modulus, Poissons 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.

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.

Interpretation of Compression Behavior of Structured and Remolded Marine Soils

AbstractAlthough extensive research has been conducted on the strength and stiffness of stabilised soils, fewer attempts have been made on the compression behavior of artificially structured and re...

Effect of lime treatment on geotechnical properties of Dunkirk sediments in France

The increasing cost associated with high-quality materials has lead to the need for sediments to be treated and then used in road construction in the context of durable development. Therefore, the modification and stabilisation of Dunkirk marine sediments by using lime is necessary to study for their potential use in road construction. Based on the physical characteristics of untreated sediments, a series of laboratory tests to investigate the geotechnical properties of untreated sediments and lime-treated sediments, such as unconfined compressive strength tests, standard oedometer tests, direct shear tests and triaxial tests, were performed. Lime was added in percentages of 3% and 6%, by weight of dry sediments. The test results show a significant improvement in unconfined compressive strength and shear strength due to the addition of lime. From the strain–stress relationship of compressive strength tests, it can be found that the failure mode of solidified sediments develops gradually from plastic failure to brittle failure, while the failure strength increases and the failure strain decreases with lime content. Compared with untreated sediments, the shear strength parameters of solidified sediments determined by direct shear tests, such as internal friction angle and cohesion, are increased owing to the pozzolanic reaction between lime and clay minerals. Using the oedometer apparatus, it is observed that after lime treatment, the preconsolidation pressure, the coefficient of consolidation and the compression index are increased, while the swelling index is decreased. The characteristics of the deviator stress–axial strain relation and the pore water pressure distribution under different confining stresses are compared with untreated and treated sediments, and the effect of lime content on cohesion and internal friction angle determined by triaxial tests is discussed.

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.

Temperature-Accelerated Strength Development in Stabilized Marine Soils as Road Construction Materials

AbstractFew studies have been reported about the effect of high curing temperature on the engineering properties of lime/cement-treated marine soils as alternative materials in road construction. L...

Co-valorisation of Dunkirk dredged sediments and siliceous–aluminous fly ash using lime

The objective of this work was to investigate a viable alternative for the final disposal of siliceous–aluminous fly ash and dredged sediments by using them as roadbed materials. For this purpose, the physical parameters of sediments were studied through a series of laboratory tests. For designed mixes, in terms of mechanical property, the modified compaction tests, unconfined compressive tests and tensile strength tests are realised to evaluate the evolution of compaction and strength characteristics of sediments with different curing time and binder content. The standardised swelling tests were carried out to appraise the effect of lime and fly ash on swelling potential and Immediate California Bearing Ratio index. To appraise the durability of designed materials, the thawing–freezing tests and water immersion tests were carried out. A coefficient of strength loss was defined to quantify the effect of freezing–thawing damage and water immersion ageing on compressive strength of sediments. Finally, the X-ray diffraction analysis and schematic sketch were undertaken to explain the microstructure change and mechanism of strength improvement of lime/fly ash-treated sediments.

Natural Dewatering of Marine Dredged Sediments

The aim of this study is to explore the water content decrease in dredged sediment by natural evaporation and/or drainage. This operation constitutes, in several fields, a preliminary operation to insure a reliable beneficial use of this material. Firstly, a methodology is proposed to assess the relative efficiency of drainage and evaporation in the process of water content reduction in the dredged sediment. Secondly, comparisons of measured evaporation rates are compared to predictions of an available model in the literature. Thirdly, the observed stages during drying are explained in the light of standard parameters measured on the sediment. Finally, a relationship between water content decrease and increase of shear strength of the sediment is discussed. These results will allow a better management of beneficial use of the sediment and enhance scheduling of the drying operation and its transport.

Durability and Swelling of Solidified/Stabilized Dredged Marine Soils with Class-F Fly Ash, Cement, and Lime

AbstractVery few studies have been carried out to investigate the durability and swelling behavior of dredged marine materials. To tackle this issue, this study mainly considers the influence of wa...