Physicochemical Characterization of Geopolymer Binders and Foams Made from Tunisian Clay (original) (raw)
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Effect of calcination temperature of tunisian clays on the properties of geopolymers
Ceramics Silikaty
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 ...
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2014
The development of sustainable construction and building materials with reduced environmental footprint, in both manufacturing and operational phases of material life cycle, is attracting increasing interest. In this frame, new geopolymer-based materials seem very attractive, due to their good mechanical properties, chemical and fire resistance. In addition, as compared to the ordinary Portland cement, they are characterized by higher environmental sustainability, in terms of reduced production energy requirements and lower CO2 emissions. In this paper we have prepared different geopolymer materials starting from a calcined clay. Pastes and mortars showed a good mechanical strength. Starting from these samples, materials characterized by different macroscopic features were developed, including a lightened concrete, a multilayer sample and macroporous materials at increasing pores amount and size, with the aim of investigating the applicability of geopolymers towards different buildi...
A new geopolymeric binder from hydrated-carbonated cement
Materials Letters, 2012
This paper evaluates the use of hydrated Portland cement as the raw material in the production of geopolymers. The silicon and aluminium oxides needed for the geopolymerization process were produced by the carbonation of hydrated Portland cement, which transforms CSH and CAH (Portland cement hydrates) into silica and alumina gels. Hydrated-carbonated Portland cement was alkali activated with a NaOH/waterglass solution. Pastes and mortars were prepared, and micro-structural and mechanical properties were analyzed. It has been noted that geopolymers are mechanically stable and yield compressive strength higher than 10MPa when mortars are cured at 65º C for three days. The results have shown that there are interesting possibilities for re-using the cement-rich fraction of construction and demolition waste. Alkaline activation of hydrated-carbonated Portland cement could be considered a low CO 2-emission binder.
PROPERTIES OF GEOPOLYMER CEMENTS
Geopolymer cement, high-alkali (K-Ca)-Poly(sialate-siloxo) cement, results from an inorganic polycondensation reaction, a so-called geopolymerisation yielding three dimensional zeolitic frameworks. High-tech Geopolymer K-Poly(sialate-siloxo) binders, whether used pure, with fillers or reinforced, are already finding applications in all fields of industry. These applications are to be found in the automobile and aeronautic industries, non-ferrous foundries and metallurgy, civil engineering, plastics industries, etc. Geopolymer cement hardens rapidly at room temperature and provides compressive strengths in the range of 20 MPa, after only 4 hours at 20°C, when tested in accordance with the standards applied to hydraulic binder mortars. The final 28-day compression strength is in the range of 70-100 MPa.The behaviour of geopolymeric cements is similar to that of zeolites and feldspathoids; they immobilize hazardous materials within the geopolymeric matrix, and act as a binder to convert semi-solid wastes into adhesive solids. Their unique properties which include high early strength, low shrinkage, freeze-thaw resistance, sulphate resistance and corrosion resistance, make them ideal for long term containment in surface disposal facilities. These high-alkali cements do not generate any Alkali-Aggregate-Reaction. Preliminary study involving 27 Al and 29 Si MASNMR spectroscopy and the proposed structural model, reveal that geopolymeric cements are the synthetic analogues of natural tecto-alumino-silicates.
Geopolymer Cements and Their Properties: A Review
Building Research Journal, 2015
Concrete is the world's most versatile, durable and reliable construction material. Next to water, concrete is the second most used substance on earth and it requires large quantities of Portland cement. The industrial sector is the third largest source of man-made carbon dioxide emissions after the transportation sector as the major generator of carbon dioxide, which pollutes the atmosphere. Ordinary Portland cement (OPC) production produces the largest amount of carbon dioxide amongst all industrial processes. In addition to that a large amount of energy is also consumed for the cement production. The production of OPC not only consumes a huge amount of the natural resources i.e. limestone and fossil fuels but also produces almost 0.9 t of CO2 for 1t of cement clinker production. Thus, the world cement production generates 2.8 billion tons of manmade greenhouse gas annually. Hence, it is inevitable to find an alternative material to the existing most expensive, most resource a...
Physical–chemical characterization of Tunisian clays for the synthesis of geopolymers materials
Journal of African Earth Sciences, 2015
Natural clay materials from Tunisia were examined as an aluminosilicate source for the synthesis of consolidated materials at low temperatures. Three clay samples were collected from the El Kef, Douiret and Gafsa basins and calcined at different temperatures. All of the samples were characterized using chemical and mineralogical analyses, thermogravimetry, dilatometry, and Fourier transform infrared spectroscopy (FTIR) measurements. The chemical (XRF) and mineralogical analyses (XRD and FTIR) indicated that all of the samples contained various amounts of kaolinite and quartz, followed by calcite, mica, palygorskite and gypsum. Curing produced a binder which did not significantly affect the physic-chemical properties of these clays. The obtained materials heterogeneous did not reach the geopolymerization stage, most likely because of their low kaolinite content. The addition of a suitable aluminosilicate to these clays is therefore recommended to produce homogeneous consolidated geopolymers. The synthesized materials obtained after the addition of metakaolin to the formulation to improve reactivity have interesting properties, thereby providing good potential for Tunisian clays in the synthesis of geopolymers.
2020
The geopolymer cement is a suitable alternative material for Portland cement due to their environmental compatibility, low curing temperature, and high strength. In this research, Kaolin was used as a raw material for the construction of a geopolymer cement, while sodium hydroxide was an alkali hydroxide. Kaolin is calcined at 750 °C to obtain meta-kaolin. Geopolymer samples were prepared at various curing temperatures (25, 50, and 75 °C), different curing times (3, 7, 21, 28, and 60 days) and with different activator ratios (0.6-0.9). The thermal analysis of kaolin was done via DTA/TGA. Investigation on the geopolymer cement structure and phases were performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and magic angle spinning nuclear magnetic resonance (MAS-NMR). Also, the effects of temperature and time of curing and Na2O/SiO2 molar ratio were studied. The results showed that the maximum compressive strength was 115 MPa, which obtained at a mol...
Sustainable Construction Materials and Technologies (SCMT), 2019
Low purity kaolin clay is presently receiving attention as a promising aluminosilicate source that has the potential of extending the application of geopolymers because of its global abundance and low embodied energy, but its strength performance depends substantially on the calcination process, mineralogy of the clay, type and proportion of chemical activator etc. This work focuses on comparing the compressive strength of calcined clay geopolymer mortars activated by three forms of chemical activators. Three groups of geopolymer mortar mixes were prepared and tested, group one utilizes sodium hydroxide solution (NaOH) prepared by adding 68% water to the pellets 24 hrs prior to mixing, group two based on sodium silicate solution derived by adding 55.9% water to sodium metasilicate pentahydrate (Na2SiO3.5H2O) 24 hrs prior to mixing, while the group three mixes were activated with industry produced Na2SiO3 solution that has 54.5% solid component. The results show that high compressive strength is achieved by developing calcined clay geopolymer mortar using high viscosity industry produced sodium silicate solution, while very low strength is achieved by utilizing sodium silicate containing chemically bounded water. The result further shows that the compressive strength of the geopolymer mortars are enhanced by sealed curing of the samples.
Synthesis of geopolymer cement using natural resources for green construction materials
2015
This work aims to investigate the use of alkali activated metakaolinite from natural kaolinitic soil as precursors for the production of geoplymer cement for green construction materials. Geopolymer cement was synthesized using metakaolinite, and alkaline activators, namely sodium silicate (Na2SiO3) and sodium hydroxide. For metakaolinite preparation, Kaolinitic soil sample was collected from kaolin deposit (Saudi Arabia), which is located in Riyadh region. XRD analysis showed that kaolinite phase, was diminished due calcination and geopolymerization. The geopolymer cement exhibits a residual metakaolin layers bonded by geopolymer gel as shown by SEM analysis. The produced geopolymer cement exhibited a flexural strength of 12.3MPa, and compressive strength of 32MPa and 44.2MPa under immersed and dry conditions. The produced geopolyemer was characterized by relatively low density, 1.45 g/cm3, and comparable water absorption, 15% (w/w), compared with other cement-based materials. The ...
Elaboration of geopolymer cement based on dredged sediment
2019
This work aims to study the feasibility of making a geopolymer cement based on dredged sediments, from the Fergoug dam (Algeria). Sedimentary clays were characterized before and after calcination by X-ray diffraction, ATG / ATD, spectroscopy (FTIR) and XRF analysis. The reactivity of the calcined products was measured using isothermal calorimetric analysis (DSC) on pastes prepared by mixing an alkaline solution of sodium hydroxide (NaOH) 8 M in an amount allowing to have a Na / Al ratio close to 1. Also, cubic mortar samples were prepared with a ratio L / S: 0.8, sealed and cured for 24 hours at 60 ° C and then at room temperature. The results obtained allowed to optimize the calcination time of 5 hours for a better reactivity of these sediments, and a concentration of 8M of sodium hydroxide and more suitable to have the best mechanical performances.