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Showing 5 results for Kaolin

M. A. Soleimani, R. Naghizadeh, A. R. Mirhabibi, F. Golestanifard ,
Volume 9, Issue 4 (12-2012)

Metakaolinite-based geopolymer has been synthesized at about 25 °C from metakaolin which has been calcined in different temperatures (600-900 °C) and different Na2O/SiO2 ratio activator (0.3-1.1). Compressive strength and microstructure of cement pastes after 7-28 days curing at ambient temperature were measured. Compressive strength tests on the samples showed that the sample made with calcined kaolin at 700 °C and molar ratio of 0.6 has highest average compressive strength of 32 MPa after 28 days of curing. Evaluation of infrared spectroscopy (FTIR) and microstructure showed that geopolymer cement developed and new molecular structure established
Y. Kianinia, A. K. Darban, E. Taheri-Nassaj, B. Rahnama, A. Foroutan,
Volume 12, Issue 1 (3-2015)

A method for producing high surface area nano-sized mesoporous alumina from inexpensive Iranian kaolin as raw material is proposed. In this method, first, kaolin was purified for purifying Kaolin, High Grade Magnetic Separation and leaching with HCl and chemical bleaching treatment by using sodium dithionite (Na 2 S 2O4 ) as reducing agent in acidic media (H 2SO 4 ) were used. Purified kaolin was calcined. After that, Al (hydr) oxide from acid -leachates of calcined kaolin was precipitated with ammonia, in presence of polyethylene glycol. Finally, a white powder of nano-sized alumina particles was obtained after calcination. BET surface area, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to characterize the sample. The resulting alumina with relatively high surface area (201.53 m 2 g -1 ) and narrow mean pore diameter (6.91 nm), consists of a particle size distribution ranging from 22 to 36 nm.
H. R. Sobhani Kavkani, A. Mortezaei, R. Naghizadeh,
Volume 13, Issue 2 (6-2016)

Different mineral admixtures of Indian metakaolin, Iranian silica fume and nanosilica were used to produce high performance mortars. Two different sands types with grain size of 0.015-4mm were mixed with type II Portland cement, polycarboxylate superplasticizer,mineral admixture with 650kg/m3 cement content and water/cement ratio of 0.35. Different amount of cement was replaced by metakaolin or silica fume (5-15wt%) or nanosilica (0.8-5wt%). After mixing, moulding and curing, compressive strength, electrical resistivity and abrasion resistance were studied. The maximum compressive strength of 28 days samples were 76MPa, 79MPa and 75MPa for 15wt% substitution of cement with metakaolin, silica fume and 5wt% with nanosilica. The compressive strength of these samples showed 28%, 33% and 26% increment in comparison with reference sample, respectively. X-ray patterns showed that replacing silica fume leads to reduction of Portlandite (Ca(OH)2) phase. This can be attributed to the pozzolanic reaction and formation of new hydrated calcium silicate phase (CSH) that caused improvement of strength of admixtures containing samples. The microstructure of silica fume containing sample also showed better bond between sand and matrix. The electrical resistivity of samples with 15wt% metakaolin or silica fume and 5wt% nanosilica reach to 21kΩ.cm, 15 kΩ.cm and 10kΩ.cm, respectively. These samples showed high durability and corrosion resistance relative to reference samples (3.4 kΩ.cm). The abrasion resistance of different admixtures, specially silica fume containing samples were improved.


Anas Al-Reyahi, Salem Yahya Degs, Ayman Issa, Zyad Khattari, Mohammed Abu Al Sayyed,
Volume 18, Issue 4 (12-2021)

The structural properties of a natural clay sample (51% kaolinite) were tweaked to suit specific applications. H2SO4 and NaOH (1.0 M) treatment caused structural alterations and a significant release of Al ions compared to Si ions. Chemical treatment caused structural alterations, according to XRD analysis. FTIR analysis also indicated higher density of polar surface groups upon treatment which affected the corresponding dielectric behaviors. Dielectric measurements shown the suitable application of the materials either as dielectrical insulator and this dependent on the applied frequency. Acid treated kaolinite was reported to be a promising dielectric at 10 and 1000 Hz. With appropriate mass attenuation coefficients (μ/ρ) 12.098-12.182 cm2/g and a high half value layer of 10 cm at 10 keV, kaolinite and other treated forms were adequate shielding materials.
Nailia Rakhimova, Vladimir Morozov, Aleksey Eskin, Bulat Galiullin,
Volume 20, Issue 3 (9-2023)

In this study, the potential of calcined montmorillonite as a primary precursor for one-part alkali-activated cement incorporated with high percentage of limestone, is evaluated. Comparative studies on the properties of the sodium silicate activated metakaolin-limestone and metamontmorillonite-limestone fresh and hardened cement pastes depending on several formulation and processing parameters (precursor nature, dosages of limestone and alkali reactant, curing conditions) showed that metamontmorillonite exhibits reactivity comparable to that of metakaolin in the studied cement systems. The mechanical performance of optimal alkali-activated cement formulations consisted of 20-30% of metamontmorillonite and 70-80% of limestone is provided by both reactivity of metamontmorillomite under sodium silicate activation and the filler, nucleation, and chemical effects of the raw limestone. The reaction products and microstructures of alkali-activated metamontmorillonite-limestone cement-based hardened pastes were investigated using thermal, XRD, and SEM/EDS analyses.   

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