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Nowadays,the preservation of natural resources,the reuse,and the recycling of waste and by-products in the cement industry are gaining increasing attention in a sustainable development project.In this perspective,many studies focus on finding solutions in order to propose environmentally friendly materials.Nowadays the sediments represent a way to preserve the natural resources by their reuse as a secondary raw material in multiple applications(concrete,roads,landscaped mound,etc.).However,they commonly contain contaminants,organic matter(5%-30%),high water content(50%-200%),and relatively small particle size(Dmax≤300 mm).Therefore to improve the mechanical properties of this material as well as its physiochemical ones,specific methods of characterization and appropriate treatment techniques(calcination,chemical treatment,etc.)are required.This article presents a bibliographical review of the efficient use of sediments in cementitious matrix.It details experimental tests that must be performed to ensure the durability of sediment-based structure and assess their environmental impact under prescribed conditions. 相似文献
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Dongxing Wang Mahfoud Benzerzour Hongwei Wang Nor-Edine Abriak 《Marine Georesources & Geotechnology》2020,38(9):1046-1055
AbstractA 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. 相似文献
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Dongxing Wang Xiangyun Gao Ruihong Wang Stefan Larsson Mahfoud Benzerzour 《Marine Georesources & Geotechnology》2020,38(6):659-671
AbstractAlkali-activated industrial by-products (granulated blast furnace slag, Class F fly ash) by traditional alkali activator (such as NaOH and Na2SiO3) serves as a partial replacement for Portland cement in soil stabilization projects and suffers from environmental and technical problems. Reactive MgO – a greener and more practical alternative has recently emerged as a potential activator for slag and fly ash, but its micromechanisms of alkaline activation still need to be deeply investigated for strength improvement of soils. Hence, this study focuses on the strength and hydration properties of reactive MgO-slag and MgO-fly ash solidified soils, especially incorporating the impact of elevated curing temperature. Reactive MgO is proved to be excellent as a novel activator for activation of slag and fly ash, and their activating efficiency increases with elevated curing temperature that helps to remarkably enhance the compressive strength of soils. The major hydration products for reactive MgO-slag solidified soils, detected jointly by X-ray diffraction, scanning electron microscopy and thermogravimetric/differential thermogravimetric tests, are calcium silicate hydrate gels and hydrotalcite-like phases. The primary hydration products for MgO-fly ash solidified soils are magnesium silicate hydrate gels and Mg(OH)2. That is just the intrinsic reason why the microstructure of solidified soils becomes much denser and the mechanical behavior is significantly improved. The minor carbonate phases such as magnesium carbonate and/or calcite are also observed in reactive MgO-slag and MgO-fly ash solidified soils, depending on the period of exposure to air. The curing temperature and binder amount are proved to be the two major factors governing the hydration process of reactive MgO-slag and MgO-fly ash blends. A higher curing temperature and binder amount can generate more hydration products, but their chemical compositions such as accurate element ratios need to be investigated in the future study. 相似文献
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Mahfoud Benaissa M. C. Berguig V. Doumbia S. Bouraoui 《Arabian Journal of Geosciences》2017,10(15):329
The equatorial electrojet (EEJ) is an intense daytime ionospheric current that circulates eastward along the geomagnetic dip equator. In this work, the EEJ current intensity was studied from ground-based magnetic data and CHAllenging Minisatellite Playoad (CHAMP) satellite observations. The ground-based magnetic data were recorded along a meridian chain of three stations across the dip equator in West Africa. These stations were operated by the Institut de Physique du Globe de Paris (IPGP). For the CHAMP satellite data, vector magnetometer records during geomagnetically quiet periods with Kp?≤?2 were used. To estimate the EEJ current intensity, we have first isolated its magnetic effect from CHAMP satellite observations for 10 years (from July 2000 to September 2010). The results were used to analyze the EEJ seasonal variability and the local time and longitude dependence. In addition, a comparison between ground-based and satellite observations of the EEJ current intensity was made. A good correlation was found between satellite and ground-based EEJ current intensity, with an average correlation coefficient of r 2 ~0.93. This performed correlation show that the technique used in this study can be extended to all ground magnetic stations for modeling the EEJ phenomena. 相似文献
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