The suitability of thermally activated red illite / kaolinitic clay as raw material for geopolymer binders (original) (raw)
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The suitability of thermally activated illite/smectite clay as raw material for geopolymer binders
Applied Clay Science, 2009
So called geopolymers or geopolymeric binders and cements are made by means of an alkaline activation of materials reactive in this respect. Such material has to consist of a certain amount of silicate and aluminate phases which can be dissolved by the alkaline medium. In the consequence stable polymeric networks of alumosilicates will be formed. Metakaolins and alumosiliceous fly ashes, in particular, have by now achieved noteworthy significance. The search for alternative low cost or high available materials may lead among other things to "normal clays". This material is widely available all over the world and may show certain reactivity after a thermal activation process. This investigation focuses on the suitability of illite/smectite clay to form a geopolymer after thermal and alkaline activation. Therefore clay containing mainly illite was thermally activated between 550 and 950°C. The degree of dehydroxylation and the reached reactivity were followed by X-ray diffraction, NMR spectroscopy and dissolution techniques. The performance of the geopolymer binder in terms of strength as well as the phase composition was studied.
Cement and Concrete Research, 2016
This research focused on developing thermally-stable materials based on alkali-activation of slag, fly ash, and metakaolin compared to portland cement mixtures by using a hierarchical approach to material design. At lower length scales, X-ray diffraction (XRD) characterized the mineralogy that coupled to higher length scale experiments using thermogravimetric analysis (TGA) for determining the materials thermal stability. Additionally, high-energy X-ray computed microtomography (μCT) determined the best-performing material formulation that minimized thermal damage when exposed to high temperatures (650°C). The thermal loading was ramped up to 650°C from ambient temperature in 60 s and then held for a total of 10 min. The μCT identified that the alkali-activated fly ash mortar had less initial porosity than the ordinary portland cement mixtures, with more than 66% of the pores between 20 and 50 μm in diameter. Consequently, the alkali-activated fly ash mortar was able to dissipate approximately 565°C in just 50 mm of material, outperforming all the other mixes studied in this paper with μCT confirming minimal damage after the temperature exposure.
2017
In the present work we sought to determine the most convenient calcination temperature of Tunisian kaolinitic clay in order to produce a more reactive metakaolin and to determine the most suitable potassium hydroxide (KOH) and sodium hydroxide (NaOH) concentration to produce geopolymer cements with good physical and mechanical performance, less energy consumption and low carbon dioxide emission. This product would play the role of a construction material able to replace Portland cement. The kaolinitic clay fractions collected from Tabarka (Tunisia) were first calcined at different temperatures ranging from 550 °C to 1 100 °C. Calcined fractions were then activated by potassium hydroxide and sodium hydroxide solutions with concentrations of between 5 M to 18 M. The mineral and chemical composition of raw and geopolymer samples was characterized by X-ray diffraction, infrared spectroscopy and thermal analysis, whereas the mechanical and physical properties of hardened samples were cha...
Portland cement is considered an excellence building material. This is due mainly to its high performance, its good quality/price ratio and the raw materials from which it is made can be found almost everywhere in the world. However, the development of alternative Portland cements obtained through processes involves lower emission of CO2 into the atmosphere is a priority research and great interest worldwide. Alkaline activation constitutes an alternative to Portland cement, preferably amorphous or vitreous aluminosilicates and alkaline activator (such as NaOH, Na2CO3 or sodium silicates hydrates). The aluminosilicates may be natural products such as metakaolin or industrial by-products such as blast furnace slag or aluminosiliceous fly ash. These cements and concretes obtained by alkali activating aluminosilicates are characterised by high mechanical strength, low heat of hydration and high impermeability, as well as resistance to high and low temperatures and sulphate, seawater and acid attacks. Moreover, the preparation of these alkaline cements requires lower energy than in the manufacturing process of Portland cement. However, we still cannot say or establish that alkaline cements (alkali activated materials or geopolymers) are based on a clean chemical to the environment, due to production processes of alkaline solutions such as sodium silicates emit large amounts of CO2 into the atmosphere. This article aims to make a trip back in time to the origins of the alkali activation to explain the most characteristic and important chemical concepts.
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 ...
Geopolymerization Behaviour of Red and White Clays
Journal of Nepal Chemical Society
Construction is one of the most important activities increasing the demand for Portland cement resulting significant amount of CO2 emission, natural resources degradation, and a high amount of energy consumption. The use of geopolymer has been studied as a potential substitute for Portland cement. Geopolymers are environmentally-friendly binding materials that are produced by the polymerization of alumino-silicates in presence of alkali polysilicates forming Si-O-Al bonds, which are used for several building applications. In this study, red and white clays which contain solid alumino-silicate have shown reactive in presence of an alkaline activator. The addition of lime has shown improvement in the mechanical and physical properties of the geopolymer products. The FTIR analysis and SEM images of the product have shown the formation of aluminosilicate gel in the geopolymeric product. The maximum compressive strength of the geopolymer products RCW and RWL were achieved to be 15.91 and...
Durability of alkali activated cement produced from kaolinitic clay
Applied Clay Science, 2015
Alkali activated products were synthesized by activation of kaolinitic clay from Hiswa area, Jordan with a sodium hydroxide solution. These specimens were subjected to long-term durability tests under different environmental and chemical conditions. The geopolymer specimens undergo very low drying shrinkage. The specimens perform well under ambient, de-ionized water, wet-dry cycles, sea water, and sodium sulfate conditions. The newly developed material from Hiswa clay shows a stable strength under all these conditions. The specimens are however attacked by acid solutions and lose about 9.7% of their mass after 90 days of exposure. The alkali-silica reaction has highly affected the geopolymer specimens as indicated by cracking, expansion and loss of mechanical strength.
Journal of the Korean Ceramic Society, 2020
The main target of this work is to compare the compressive strengths and the microstructural properties geopolymer cements from waste fired brick as low-value aluminosilicate-rich waste and metakaolin. The chemical reagent used in this investigation is a sodium waterglass from rice husk ash. The obtained results show that waste fired brick contains a higher amount of SiO 2 (60.98 wt%). The quartz content in the waste fired brick, standard and local metakaolins was estimated at approximately 8, 2 and 8 wt%, respectively. The X-ray patterns of these aluminosilicates indicate the broad hump structure between 15 and 35° (2θ) corresponding to the amorphous aluminosilicate phase. Besides this amorphous phase, waste fired brick shows the broad bands of hematite at 33.29 and 35.87° (2θ) indicating that some Al is replaced by Fe in IV-fold coordination. The micrographs of metakaolins show the platy-shaped with coarse-grain particles and the one of waste fired bricks indicates the platy-and spherical-shaped with smaller particle sizes. The compressive strength values of geopolymer cements from local and standard metakaolins are 40.32 and 44.46 MPa, respectively. Whereas the one from waste fired brick is 47.82 MPa. It was found that waste fired brick could be used as an alternative low-value aluminosilicate-rich waste for producing geopolymer cements with high compressive strength.
Civil Engineering Journal
Great efforts are being made to minimize the negative impact of the Portland cement industry on the environment by using industrial by-products during the manufacture of clinker or by the partial replacement of cement during the preparation of concrete. However, the carbon footprint remains relatively high in addition to the large consumption of natural resources such as sand and other aggregates. A solution to these problems is to completely replace Portland cement with a new generation of mineral binders, commonly known as geopolymers, which have properties similar to those of Portland cement. These binders can be obtained by the alkali-activation of siliceous or aluminosilicate materials. This study aims to develop pozzolanic type binders at room temperature (20°C) from the alkali-activation of aluminosilicate materials based on metakaolin and blast furnace slag at different percentages. Different activators were employed, including solid (NaOH) and liquid (Na2SiO3.nH2O). The opt...