EFFECT OF CALCINATION TEMPERATURE OF TUNISIAN CLAYS ON THE PROPERTIES OF GEOPOLYMERS

Geopolymers are amorphous three dimensional aluminosilicate materials that may be synthesized at room or slightly higher temperature by alkaline activation of aluminosilicates obtained from industrial wastes, calcined clays and natural minerals. Among the different family of geopolymers, two Tunisian clays (a kaolinite clay from Tabarka and illito/kaolinitic clay from Medenine) are tested for their feasibility of geopolymers at low temperature. The unfired and calcined clays were dissolved in strongly alkaline solution in order to produce consolidated materials whose pastes were characterized by their compressive strength. Hardened geopolymer samples were also submitted to X-Ray diffraction, FTIR spectroscopy and scanning electron microscopy analyses. The geopolymer strength is related to the structure and reactivity of the clay generated by thermal treatment and to the role of associated minerals in clays. The amorphous character of obtained geopolymers and the displacement of the IR wavenumber are signature of geopolymerisation reaction

The role of hematite in aluminosilicate gels based on metakaolin

International audienceThis paper investigates the role of iron oxide in natural clay and its contribution to polycondensation reactions. Iron oxide was added to pure kaolin in the same proportion as Medenine clay with different amounts of potassium hydroxide. The physicochemical and structural properties of these materials were determined by infrared spectroscopy, scanning electron microscopy, thermal analyses (DTA-TG) and X-ray diffraction. The amorphous character seen in the diffractograms obtained from the materials and the displacement of the IR wavenumber are indicative of a polycondensation reaction. The representative characterization of the microstructure of different samples using electron microscopy highlights the nonreactivity of iron exhibited during consolidation. In general, the contribution of iron oxide seems to be small under the conditions described here

An overview on the potential of geopolymers for concrete infrastructure rehabilitation

Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. In USA alone the rehabilitation needs are estimated to exceed 1.6 trillion dollars over the next 5 years. Since the majority of the existent infrastructures are concrete based this means that concrete infrastructure rehabilitation is a hot issue to be dealt with. Besides the sooner concrete deterioration is tackled the lower are the rehabilitation costs. This paper provides a literature review on concrete repair materials, highlighting the current problems face by them. It covers concrete surface treatments, patch repair and FRP strengthening. The case of trenchless rehabilitation of concrete sewage pipelines is also discussed. The potential of geopolymers to overcome those limitations is analyzed

Mineralogical and chemical investigation of Tunisian phosphate washing waste during calcination

Phosphate washing waste (PWW) is one of the wastes generated by the phosphate mine with a very high amount. This waste was investigated in this work to study the effect of the calcination of the PWW at four different temperatures 600 oC, 700 oC, 800 oC and 900 oC on its mineralogical and chemical composition. The samples were investigated by X-ray powder diffraction, Fourier transform infrared, differential scanning calorimetry and thermogravimetric analysis, solidstate magic angle spinning nuclear magnetic resonance of 29Si, 27Al and 31P and scanning electron microscope. The results show that the PWW presents a complex system and it suffers a significant change on its mineralogical and chemical composition after calcination. It reveals the presence of carbonate, natural zeolite, fluorapatite, quartz and clay. After calcination, the waste shows the disappearance of some of these phases and the appearance of others and some other phases remain steady

Myasthenie - spondylarthropathies: association fortuite ? A propos d’un cas et revue de la littérature

Propos Nous rapportons le cas d’un patient atteint d’une myasthénie associée à une spondylarthropathie. Cette observation est originale de part sa rareté, six cas seulement on été rapportés dans la littérature et le problème que pose cette association : est ce qu’elle est fortuite ou impliquerait-elle d’autres facteurs génétiques qui restent à prouver ?Observation Monsieur J.H. âgé de 32 ans, aux antécédents de myasthénie depuis 2002, était hospitalisé en avril 2004 pour polyarthrite chronique bilatérale et asymétrique évoluant depuis un an, touchant le poignet gauche, les inter phalangiennes proximales des 3ème et 5ème doigts droits et le genou droit associées à des talalgiesbilatérales et une douleur des articulations sacro-iliaques. La biologie montrait un syndrome inflammatoire modéré, des facteurs rhumatoïdes faiblement positifs et un typage HLA B7 et B17. Le bilan radiologiquemontrait une arthrite des mains, une enthésite calcanéenne et permettait de suspecter une sacro-iliite bilatérale qui était confirmée par un scanner. L’évolution était bonne sous anti- inflammatoires nonstéroïdiens pendant 6 mois. Il consulte en janvier 2006 pour le même tableau associé à une sècheresse buccale et oculaire. Le bilan trouvait une VS à 20, des facteurs rhumatoïdes faiblement positifs mais desAAN positifs à un taux 1/160 homogènes avec des anti SSA. Les radiographies standard montraient une carpite stade II gauche. L’examen ophtalmologique a confirmé le syndrome sec oculaire. La biopsie des glandes salivaires accessoires a montré un syndrome de Gougerot Sjögren grade 2 de Shisholm

Mechanical performance of geopolymeric mortars based on tunisian calcined clay, fly ash and metakaolin

Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. Since the majority of the existent infrastructures are Portland cement concrete based this means that concrete infrastructure rehabilitation is a hot issue to be dealt with. Geopolymers are novel inorganic binders with high potential to replace Portland cement based ones. So far very few studies in the geopolymer field have addressed the rehabilitation of deteriorated concrete structures. This paper discloses results of an investigation concerning the development geopolymeric repair mortars. The mortars are based on Tunisian clay coming from Medenine region, plus calcium hydroxide, sodium silicate and sodium hydroxide. Results show that the geopolymeric mortar has a high compressive strength and a lower unrestrained shrinkage performance as long as partial replacement by metakaolin is carried out. The results also show that Tunisian calcined clay based mortars have hydration products with typical geopolymeric phases

Shrinkage and mechanical performance of geopolymeric mortars based on calcined Tunisian clay

Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. Since the majority of the existent infrastructures are Portland cement concrete based this means that concrete infrastructure rehabilitation is a hot issue to be dealt with. Geopolymers are novel inorganic binders with high potential to replace Portland cement based ones. Geopolymerization is a complex chemical process evolving various aluminosilicate oxides with silicates under highly alkaline conditions, yielding polymeric units, similar to those of an aluminosilicate glass. So far very few studies in the geopolymer field have addressed the rehabilitation of deteriorated concrete structures. This paper discloses some results of an investigation concerning the development geopolymeric repair mortars based on a calcined Tunisian clay. The results show that Tunisian calcined clay based mortars have hydration products with typical geopolymeric phases. Results also show that the geopolymeric mortar shows a high unrestrained shrinkage behavior and that its modulus of elasticity is below the threshold required for this repair mortars

Shrinkage and mechanical performance of geopolymeric mortars based on calcined Tunisian clay

"Special Issue for International Congress on Materials & Structural Stability, Rabat, Morocco, 27-30 November 2013"Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. Since the majority of the existent infrastructures are Portland cement concrete based this means that concrete infrastructure rehabilitation is a hot issue to be dealt with. Geopolymers are novel inorganic binders with high potential to replace Portland cement based ones. Geopolymerization is a complex chemical process evolving various aluminosilicate oxides with silicates under highly alkaline conditions, yielding polymeric units, similar to those of an aluminosilicate glass. So far very few studies in the geopolymer field have addressed the rehabilitation of deteriorated concrete structures. This paper discloses some results of an investigation concerning the development geopolymeric repair mortars based on a calcined Tunisian clay. The results show that Tunisian calcined clay based mortars have hydration products with typical geopolymeric phases. Results also show that the geopolymeric mortar shows a high unrestrained shrinkage behavior and that its modulus of elasticity is below the threshold required for this repair mortar

Механические характеристики геополимерных растворов на основе тунисской кальцинированной глины, золы-уноса и метакаолина

Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. Since the majority of the existent infrastructures are Portland cement concrete based this means that concrete infrastructure rehabilitation is a hot issue to be dealt with. Geopolymers are novel inorganic binders with high potential to replace Portland cement based ones. So far very few studies in the geopolymer field have addressed the rehabilitation of deteriorated concrete structures. This paper discloses results of an investigation concerning the development geopolymeric repair mortars. The mortars are based on Tunisian clay coming from Medenine region, plus calcium hydroxide, sodium silicate and sodium hydroxide. Results show that the geopolymeric mortar has a high compressive strength and a lower unrestrained shrinkage performance as long as partial replacement by metakaolin is carried out. The results also show that Tunisian calcined clay based mortars have hydration products with typical geopolymeric phases.s a high compressive strength and a lower unrestrained shrinkage performance as long as partial replacement by metakaolin is carried out. The results also show that Tunisian calcined clay based mortars have hydration products with typical geopolymeric phases.Восстановление инфраструктуры требует много- милионных затрат. Поскольку большая часть стро- ительных объектов возведена с использованием бе- тона на основе портландцемента, ремонт именно та- ких сооружений является важнейшим направлением дальнейших исследований. Геополимеры — новые не- органические вяжущие вещества, которые с высокой долей вероятности могут стать альтернативой портланд- цементу. Немногочисленные исследования геополи- меров были посвящены возможности их использо- вания при ремонте поврежденных бетонных кон- струкций. В данной работе представлены результаты исследований по разработке ремонтных растворов на основе геополимеров. В качестве основного ком- понента была выбрана тунисская глина из области Меденин с введением в качестве затворителя гидрок- сида кальция, натриевого жидкого стекла и гидрок- сида натрия. Результаты исследования показали, что геополимерный раствор обладает высокой прочно- стью при сжатии и низким уровнем усадки в свобод- ном состоянии (далее усадка) при условии частичной замены глины метакаолином. Кроме того, получен- ные результаты показали, что в растворах на основе тунисской кальцинированной глины продукты гидрата- ции соответствуют стандартным геополимерным фазам.info:eu-repo/semantics/publishedVersio