Influence of Thermal Treatment on Kankara Kaolinite

In this work, the influence of thermal treatment on the structure of Kankara kaolinite was studied for the first time, using X-ray diffractogram (XRD), EDX, NanoSEM, FTIR-Attenuated Total Reflectance, DTA/TGA and BET surface area measurements. The treatment temperatures applied represents the peak of the transformation stages. The results show that surface area decreases with increase in temperature of treatment, while its crystal structure was transformed from the native kaolinite structure via the amorphous metakaolin to the typical mullite/crystobalite structure though with some unidentifiable peaks. The morphological studies showed that Kankara kaolinite is composed of nano-platelets of about 30nm thickness and in bundles of between 1 – 3 µm thicknesses with some marked variations/reductions as the treatment temperatures increases. The DTA/TGA result shows that the kaolinite undergoes dehydroxylation at 528.560C while been converted to metakaolin with a weight loss of about 14.4%. The presence of the characteristic OH, Al-OH, Si-OH and Si-O-Al bands were confirmed with the ATR studies which also showed the disappearance and subsequent appearance of new bands as the treatment temperature increased, this also affected the surface area and pore sizes of the transformation products

An alternative methodology to predict aging effects on the mechanical properties of glass fiber reinforced cement (GRC)

The effect of three different aging methods (immersion in hot water, freeze–thaw cycles and wet–dry cycles) on the mechanical properties of GRC were studied and compared. Test results showed that immersion in hot water may be an unreliable method for modified GRC formulations, with it being in probability a very harmful procedure. A new aging method, mixing freeze–thaw cycles and wet–dry cycles, seems to be the most accurate simulation of weather conditions that produce a noticeable change in GRC mechanical properties. Future work should be carried out to find a correlation between real weather and the proposed aging method

Failure and impact behavior of facade panels made of glass fiber reinforced cement(GRC)

GRC is a cementitious composite material made up of a cement mortar matrix and chopped glass fibers. Due to its outstanding mechanical properties, GRC has been widely used to produce cladding panels and some civil engineering elements. Impact failure of cladding panels made of GRC may occur during production if some tool falls onto the panel, due to stone or other objects impacting at low velocities or caused by debris projected after a blast. Impact failure of a front panel of a building may have not only an important economic value but also human lives may be at risk if broken pieces of the panel fall from the building to the pavement. Therefore, knowing GRC impact strength is necessary to prevent economic costs and putting human lives at risk. One-stage light gas gun is an impact test machine capable of testing different materials subjected to impact loads. An experimental program was carried out, testing GRC samples of five different formulations, commonly used in building industry. Steel spheres were shot at different velocities on square GRC samples. The residual velocity of the projectiles was obtained both using a high speed camera with multiframe exposure and measuring the projectile’s penetration depth in molding clay blocks. Tests were performed on young and artificially aged GRC samples to compare GRC’s behavior when subjected to high strain rates. Numerical simulations using a hydrocode were made to analyze which parameters are most important during an impact event. GRC impact strength was obtained from test results. Also, GRC’s embrittlement, caused by GRC aging, has no influence on GRC impact behavior due to the small size of the projectile. Also, glass fibers used in GRC production only maintain GRC panels’ integrity but have no influence on GRC’s impact strength. Numerical models have reproduced accurately impact tests

Hydrometallurgical extraction of Al and Si from kaolinitic clays

Herein is presented the results of a study on the hydrometallurgic extractionand recovery of aluminum and silicon by leaching of kaolinitic clays with HF. Thestudied extraction parameters were: temperature, reaction time, solid/liquid ratio,concentration, and precipitating agent mass. In the leaching process, mineraldissolutions near 100% were obtained when working at 348 K, solid/liquid ratio2% w/v, HF 12% v/v, for 120 minutes. The HF leach liquor generated from thedissolution of kaolinitic clays contains H2SiF6 and H3AlF6. Studies were conductedto recover the two valuable fluorides as K2SiF6 and Na3AlF6 by precipitation withalkaline salts from the leach liquor. Phases of precipitated fluorides were identifiedby XRD and surface morphology by SEM. The purity of the K2SiF6 precipitate was98.8%, whereas for Na3AlF6, it was 89.3%. Also, both synthesized solids are ofhigh commercial value due to their industrial applications.Fil: Pinna, Eliana Guadalupe. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Suarez, Daniela Silvana. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Universidad Nacional de Cuyo; ArgentinaFil: Rosales, Gustavo Daniel. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Rodriguez, Mario Humberto. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentin

In-situ early age hydration of cement-based materials by synchrotron X-ray powder diffraction

Cement based binders are building materials of worldwide importance. Since these samples are very complex, the knowledge/control of their mineralogical composition are essential to design and predict materials with specific/improved performance. Rietveld quantitative phase analysis (RQPA) allows the quantification of crystalline phases and, when combined with specific methodologies, as the addition of an internal standard or the external standard approach (G-factor), amorphous and non-crystalline phases can also be quantified. However, to carry out a proper RQPA in hydrated cementitious-materials, a good powder diffraction pattern is necessary. In this work, synchrotron X-ray powder diffraction (SXRPD) has been used, allowing in-situ measurements during the early-age hydration process. This work deals with the early hydration study of cement-based materials. The studied samples were: a laboratory-prepared belite calcium sulphoaluminate (BCSAF) clinker (non-active) mixed with 10wt% gypsum, labelled G10B0; two active laboratory-prepared BCSAF clinkers (activated with 2wt% borax), one mixed with 10wt% gypsum and the other one with 10wt% monoclinic-bassanite, hereafter named G10B2 and B10B2, respectively; and an environmentally-friendly cement sample from Henkel, composed of bassanite mixed with 15wt% Portland cement and 10wt% Metakaolin, labelled H1. Anhydrous G10B0 contains beta-belite and orthorhombic-ye'elimite as main phases, while alpha'H-belite and pseudo-cubic-ye'elimite are stabilized in G10B2 and B10B2, with the corresponding sulphate source. Anhydrous H1 contains monoclinic and hexagonal bassanite and alite as main phases. Ye'elimite, in the non-active BCSAF cement pastes, dissolves at a higher pace than in the active one (degree of reaction is α~25% and α~10% at 1 h, respectively) (both prepared with gypsum), with the corresponding differences in ettringite crystallisation (degree of precipitation is α~30% and α~5%, respectively). Moreover, the type of sulphate source has important consequences on the hydration of the active BCSAF cement pastes. Bassanite is quickly dissolved and it precipitates as gypsum within the first hour of hydration (in B10B2). At that time, ettringite starts to crystallize, and after 12 hours is almost fully crystallized, similar to G10B2. In H1, bassanite transforms into gypsum within the first hour, being the principal hydration product; ettringite starts to be formed just after few hydration minutes. These results are crucial in the understanding and development of improved cement materials.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Analysis of glass fiber reinforced cement (GRC) fracture surfaces

Glass fiber reinforced cement (GRC) is a composite material produced by the union of a cement mortar matrix and chopped glass fibers. Its good mechanical properties deteriorate with time. This phenomenon has been studied performing a tensile test program on both young and aged samples of GRC produced by using different chemical additives. Once the tests were carried out, a microstructural analysis of fracture surfaces was performed using a scanning electronic microscope (SEM). Pictures taken showed that the addition of metakaolin enables more fibers to be pulled out from the matrix instead of being broken in aged GRC samples. However, the increase in the number of such fibers pulled out did not prevent the embrittlement of GRC. Also, all the other chemical additions used did not show any improvement in the mechanical properties of GRC

Encapsulation of Cs/Sr contaminated clinoptilolite in geopolymers produced from metakaolin

The encapsulation of caesium (Cs) and strontium (Sr) contaminated clinoptilolite in Na and K based metakaolin geopolymers is reported. When Cs or Sr loaded clinoptilolite is mixed with a metakaolin geopolymer paste, the high pH of the activating solution and the high concentration of ions in solution cause ion exchange reactions and dissolution of clinoptilolite with release of Cs and Sr into the geopolymer matrix. The leaching of Cs and Sr from metakaolin-based geopolymer has therefore been investigated. It was found that Na-based geopolymers reduce leaching of Cs compared to K-based geopolymers and the results are in agreement with the hard and soft acids and bases (HSAB) theory. Cs ions are weak Lewis acids and aluminates are a weak Lewis base. During the formation of the geopolymer matrix Cs ions are preferentially bound to aluminate phases and replace Na in the geopolymer structure. Sr uptake by Na-geopolymers is limited to 0.4 mol Sr per mole of Al and any additional Sr is immobilised by the high pH which causes precipitation of Sr as low solubility hydroxide and carbonate phases. There was no evidence of any other phases being formed when Sr or Cs are added to metakaolin geopolymers

Menentusahkan faktor tekanan kerja guru sekolah menengah Gred A Daerah Batu Pahat

Kajian ini dilaksanakan untuk mengenal pasti faktor-faktor yang mempengaruhi tekanan kerja guru yang mengajar di kawasan bandar dan sekolah tersebut dikategorikan sebagai sekolah gred A. Kajian ini dijalankan di tiga buah sekolah yang terletak di bandar dalam Daerah Batu Pahat iaitu Sekolah Menengah Datin Onn, Sekolah Menengah Dato’ Bentara Luar dan Sekolah Menengah Kebangsaan Munshi Sulaiman. Kajian ini mengesahkan sama ada konstruk yang dihasilkan merupakan faktor tekanan kerja guru sekolah berkenaan. Selain itu, kajian ini juga mengenal pasti apakah faktor paling dominan yang menyebabkan tekanan kerja guru dan , seterusnya melihat impak dimensi terhadap responden berdasarkan faktor yang dikaji. Dalam menentukan konstruk, Classic Theory Test (CTT) dengan menggunakan kaedah kualitatif melalui analisis dokumen dengan membuat kupasan kajian literatur. Analisis faktor model Rasch dengan menggunakan Analisis Komponen Utama pada residual digunakan dalam kajian ini bagi memastikan dan mengesahkan konstruk atau faktor. Berdasarkan dapatan analisis dokumen, konstruk bagi faktor tekanan kerja yang dikenal pasti adalah (i) Beban kerja (ii) Kekangan Masa dan Sumber (iii) Disiplin pelajar (iv) Perhubungan Interpersonel dan (v) Keperluan Penghargaan. Melalui analisis faktor yang dijalankan pula, mendapati kesemua faktor yang dihasilkan telah menepati kriteria yang ditetapkan oleh model Rasch iaitu peratusan varians mentah dijelaskan oleh pengukuran (raw variance explained by measure) melebihi daripada 40%, peratus varians tidak dijelaskan dalam kontras pertama (first contrast unexplained variance) adalah kurang daripada 10%, dan nilai eigen kontras pertama (first contrast eigenvalue) juga kurang daripada 3.0. Hal ini membuktikan dan mengesahkan bahawa keseluruhan konstruk adalah bersifat unidimensi dan mampu mengukur apa yang hendak diukur. Faktor yang paling dominan adalah faktor disiplin pelajar dan terdapat perbezaan persepsi responden dari aspek jantina, umur dan tempoh bekerja terhadap konstruk atau faktor yang dikaji

KAJIAN KUAT TEKAN BETON RINGAN METAKAOLIN BERSERAT ALUMINIUM PASCA BAKAR

Abstrak Penelitan ini mengamati beton ringan dengan serat alumunium sebagai penguat mikro menghadapi beban alam khususnya kebakaran. Benda uji silinder berdiameter 150 mm dan tinggi 300 mm dibuat untuk selanjutnya diuji kuat tekan. Campuran beton menggunakan serat alumunium dengn aspek rasio 60, semen tipe 1, pasir, ALWA, superplaticizer dan metakaolin. Fraksi serat adalah 0,75% volume beton dan kandungan metakaolin adalah 7,5% berat semen. Pengujian kuat tekan beton mengacu kepada SK-SNI S-36-1990-03. Hasil pengujian menunjukkan bahwa kuat tekan beton ringan meningkat 12,31% dengan adanya serat alumunium dan 23,54% dengan adanya serat aluminum dan metakaolin dibandingkan dengan beton ringan normal. Pembakaran benda uji 500 0C yang dikombinasikan dengan curing dalam air, kuat tekan beton ringan meningkat 47,61% pada benda uji yang mengandung serat alumunium saja dan meningkat 11,79% pada benda uji yang mengandung serat alumunium dan metakaolin. Namun, benda uji yang mengalami pembakaran 300 0C, 400 0C dan 500 0C tanpa curing, pembakaran cenderung menurunkan kuat tekan beton. Kuat tekan beton ringan rata-rata benda uji tanpa serat pada variasi suhu tersebut mengalami penurunan 14,53%, 18,27% dan 42,21%. Pada variasi pembakaran suhu yang sama, kuat tekan rat-rata beton ringan dengan serat alumunium mengalami penurunan 26,72%, 27,52% dan 50,61%. Sedangkan benda uji beton ringan berserat alumunium yang mengandung metakaolin yang dibakara pada tiga tingkatan suhu tersebut mengalai penurunan kuat tekan 27,76%, 29,29% dan 35,74%. Hal ini mengindikasikan bahwa serat alumunium dan metakaolin memperbaiki kinerja kuat tekan beton setelah terbakar dan mengalami curing. Kata kunci: beton ringan, beton ringan berserat, metakaolin, pasca bakar, serat alumunium Abstract The research concerns on strenght of lightweight concrete with aluminium fibre as micro-reinforcement by enviromental load especially burning. Some cylindrical form of concrete of 150 mm dia, 300 mm high for compressive strenght test were made. Mixtures used aluminium fibres with aspect ratio of 60, cement type I, sand, ALWA, water, superplasticizer and metakaolin. The volume fraction of aluminium fibre was 0,75% and the used metakaolin was 7,5% of cement weight. Testing was based on SK SNI S–36–1990–03. The result shows that the average compressive strenght of lightweight concrete increases 12.33 % and 23.54% due to the addition of aluminium fibre and metakaolin respectively compared to plain lightweight concrete. As the sample was burned at 500˚ C then cured in water, the average of compressive strength was recorded higher 47,61% by samples containing aluminium fibre and 11,79% by samples containing aluminium fibre and metakaolin. However, samples those have been burned at 300 0 C, 400 0 C dan 500 0 C without curing, the fire burning tent to decrease the sample compressive strength. The average compressive strength of plain lightweight concrete at those respective temperature decreases 14,53%, 18,27% and 42,21%, while samples of lightweight concrete with aluminium fibres decreases 26.72 %, 27,52 and 50.61% and lightweight concrete with aluminium fibres and metakaolin decrease 27.76 %, 29,29 and 35.74%. This indicates that aluminium fibre and metakaolin improve the compressive strength performance of light weight concrete both before and post fibre burning combined with curing process Keywords : aluminium fibre, metakaolin light weight concrete, burning