SURICATES : demonstration through pilots of sediment reuse for coastal defence or climate change mitigation

The SURICATES project is a research initiative funded by the European Union regional funds (INTERREG NWE), aimed at increasing the reuse of dredged sediments

Urban land planning: The role of a Master Plan in influencing local temperatures

Land use planning (LUP) is central for managing issues related to climatic variation in urban environments. However, Master Plans (MPs) usually do not include climatic aspects, and few studies have addressed climate change at the urban scale, especially in developing countries. This paper proposes a framework with ten categories for assessment of climatic variation in urban LUP. Each category comprises attributes that describe a complex of relationships in influencing local temperature variations. They are analyzed for the case of the Master Plan of Porto Alegre (MPPA), the Southernmost metropolis of Brazil. It is concluded that the MPPA is strongly grounded in climate-related land and zoning coordination, but exhibits weaknesses in building, cartographical and social aspects considered synergistically relevant for tackling problems related to urban climate variation. Furthermore, the MPPA does not contain provisions related to monitoring of local climate and greenhouse gases (GHG) emissions and it is ineffective for improving energy efficiency. Specific MPPA failures stemming from these weaknesses include: an increase of 21.79% in the city's urbanized area from 1986 to 2011 to accommodate a similar increase in population, with significant horizontal sprawl; average temperature rise of 0.392. °C from 1991-2000 to 2001-2010, with statistically significant increases in temperature found since 1931; significant vehicle traffic increases, especially since 2007. From these findings, it is possible to conclude that the MPPA does not offer answers to all the imbalances related to land use, and therefore gives insufficient support to tackle the issue of rising temperatures

Experimental study of rockburst under true-triaxial gradient loading conditions

AC

Effect of Dewatering by the Addition of Flocculation Aid on Treated River Sediments for Valorization in Road Construction

Sediments produced from dredging are categorized as waste. The management of these materials is a worldwide problem. In the context of sustainable development, the traditional solutions such as, immersion, suspension and storage are controlled by national and international regulations. Simultaneously, there is a shortage of aggregates from quarries. It is for these reasons that the environmentalists are encouraged to increase the economically and ecologically responsible re-use of sediments. The aim of this work is to assess the applicability of dredged river sediments in road construction. After dredging the sediment contains a high amount of water. In order to obtain a rapid dewatering, the addition of an optimum dose of a flocculation aid has been proposed. The first part of this paper looks to evaluate the physical, geotechnical and environmental properties of the raw sediment and dehydrated sediment through addition of a flocculation aid. The second part focuses on the treatment of these materials by incorporating a hydraulic binder/lime and a granular corrector, in order to improve the mechanical properties of these sediments for use in sub-base construction and to evaluate the effect of these treatments on the dehydrated sediment. The obtained results show that the dehydrated sediment has no appreciable effect for valorization of river sediments and can be used in sub-base layer of the road construction. © 2016, Springer Science+Business Media Dordrecht

Comparison between reactive MgO- and Na2SO4-activated low-calcium fly ash-solidified soils dredged from East Lake, China

International audienceA novel approach to mitigate the environmental concerns associated with cement industry is to replace Portland cement with low carbon alternative materials such as fly ash-based geopolymer cement. Hence, reactive MgO-activated low-calcium Class F fly ash was employed in comparison to Na2SO4-activated fly ash to stabilize a lacustrine soil reused potentially in soft coastal reclamation projects and as reinforced aggregates for anti-corrosion in marine engineering. The microstructural and strength properties were investigated with series of tests including X-ray diffraction (XRD), thermogravimetry/differential thermogravimetry (TG/DTG), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and unconfined compressive strength (UCS). The results demonstrate that the main hydration products in reactive MgO- and Na2SO4-fly ash-solidified soils are, respectively, magnesium silicate hydrate (M-S-H) gel and sodium aluminosilicate hydrate (N-A-S-H) gel. This finding is reconfirmed by the weight loss of solidified samples at 40–200 °C, which is correspondingly attributed to the dehydration of magnesium silicate hydrate (M-S-H) gel and sodium aluminosilicate hydrate (N-A-S-H) gel. The morphology and bonding ability of hydration products affects the microstructure and long-term strength of solidified soils. The microstructural change identified from SEM images coincides well with the quantitative evolution of pore structure. The pores with radius of 0.01–1 µm, i.e., micropore and mesopore, are supposed to be the dominant pores in reactive MgO- and Na2SO4-activated fly ash-solidified soils. The comparison of UCS indicates reactive MgO-activated low-Ca fly ash behaves much superior to Na2SO4-activated fly ash in enhancing the long-term compressive strength of soils. This study provides insight into the promising potential of low-Ca fly ash activated by immerging material–reactive MgO to replace cement in soil improvement. © 2019 Informa UK Limited, trading as Taylor & Francis Group

Formulation of mortars based on thermally treated sediments

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Study of the polymer mortar based on dredged sediments and epoxy resin: Effect of the sediments on the behavior of the polymer mortar

International audienceSeveral studies have shown the potential of upgrading sediments in the civil engineering field. However, the complexity of sediments represents a scientific challenge in terms of their management. This study presents the river sediments recovery in a thermosetting matrix. The characterization results epoxy mortars show the feasibility of incorporating dredged sediments up to 50% substitution rate of natural sand. Moreover, according to the physic, mechanical, thermal and chemical evaluations of the thermosetting matrices, it appears that the performances depend on the factors of the rate of resin and the rate of sediments used. Indeed, the difference between the performances of resin mortars containing sediments and mortars without sediments is reduced by a resin content equal to 18%. In comparison with cementitious matrix mortars, the performances of polymeric mortars are well above. Finally, the SEM observations of different formulations made it possible to explain the results observed at the macroscopic scale. © 2019 Elsevier B.V

Effect of basalt fiber inclusion on the mechanical properties and microstructure of cement-solidified kaolinite

The polypropylene fibers, which are currently attracting enormous attention in various geotechnical applications, carry a risk of aging under an integrated effect of heat, oxygen, light and other environmental factors, causing potentially infrastructure failure. An eco-friendly and biologically inactive material – basalt fiber, which has excellent natural resistance to aging and can eliminate aging-associated disasters, deserves more attention in geotechnical field. However, quite few studies are available on the beneficial reuse of basalt fibers to improve the engineering performance of soils. Therefore, this study aims to incorporate the sustainable basalt fiber and clarify how its inclusion impacts the mechanical properties and microstructure of cemented kaolinite. The experimental programs are comprised of three types of tests, i.e. two to examine the compressive strength and triaxial shear behavior and one to evaluate the microstructure properties. The results indicate that the basalt fiber reinforcement plays an essential role in enhancing the compressive strength and peak deviatoric stress of cemented and uncemented kaolinite. The inclusion of basalt fibers improves the ductility and weakens the brittleness of cemented kaolinite. The compressive strength increases with basalt fiber content and curing time, and reaches the peak at the fiber content of 0.2%, followed by a reduction due to the formation of weak zone at higher fiber content. The peak deviatoric stress is elevated until reaching the maximum at the basalt fiber content of 0.4%, after which further addition of basalt fiber tends to reduce its reinforcing effect. The peak deviatoric stress increases as the basalt fiber length is shortened and the confining pressure is raised. The strength gain of cement-basalt fiber inclusion is much more than the sum of strength increase induced by them individually. The combination of basalt fiber and cement has the virtues of both cement-stabilized and basalt fiber-reinforced kaolinite. The SEM analysis reveals that the mechanical interaction in the form of interface bonding and friction between kaolinite particle, cement hydration product and basalt fiber is the dominant mechanism controlling the reinforcement-cementation benefits. The bridging effect (reinforcement) of basalt fibers and binding effect (cementation) of hydration products make a major contribution to the formation of stable and interconnected microstructure, which results in an evident improvement in the mechanical behaviour of cemented kaolinite. The combination of basalt fiber and cement stabilization would be an innovative and effective method for geotechnical engineering works such as soft ground improvement. © 2020 Elsevier Lt

Use of uncontaminated marine sediments in mortar and concrete by partial substitution of cement

The disposal of dredged marine sediments has become a major economic and environmental issue in the world. In this study, uncontaminated marine sediments dredged in the harbor of Dunkirk (France) were dried and ground and then used in partial substitution of cement in the manufacture of mortars and concretes. A given volume of cement has been replaced by the same volume of sediment for three substitution contents (10%, 20%, 30%) of a Portland cement CEM I 52.5. The flexural and compressive strengths of mortars decreased when the sediment replacement content increased. However, the mechanical properties of the mortar with 20% replacement of cement with sediments were better than those of a mortar made from cement CEM II/A-LL 32.5 containing a proportion of limestone similar to the sediment substitution. The total porosity measured by mercury intrusion porosimetry of different types of mortars showed that the porosity increased as the sediment substitution content increased but the pore size distribution was shifted toward smaller pores. Finally, it was demonstrated that concrete C30/37 could be designed with 20% cement replaced by sediment without the use of admixture. Additionally, this concrete fulfilled the standards with respect to the total chloride content required for unreinforced concrete. As a conclusion, dried and finely ground uncontaminated sediments appeared to be a very interesting constituent for partially substituting up to 20% of cement as its efficiency overpass limestone filler