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Influence of Sintering Temperature on the Pore Structure of an Alkali-Activated Kaolin Based Geopolymer

Ramli Mohd Izrul Izwan, Salleh Mohd Arif Anuar Mohd, Aziz Ikmal Hakem, Zaimi Nur Syahirah Mohamad, Amli Siti Farahnabilah Muhd, Abdullah Mohd Mustafa Al Bakri

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 3

987-989

EN

Kaolin-based geopolymers are alternatives for producing high-strength ceramics for construction materials. Creating high-performing kaolin ceramics utilizing the regular technique requires a high handling temperature (higher than 1200°C). Thus, the structure and properties such as pore size and distribution are affected at higher sintering temperatures. Along these lines, information with respect to the sintering system and related pore structure is essential for advancing the properties of the previously mentioned materials. This study investigated the microstructure and the density of a kaolin-based geopolymer at various sintering temperatures. The unsintered sample has the highest density of 1610 kg/cm3 , while the samples sintered at 1100°C haves the lowest density of 1203 kg/cm3 . The result also shows that increasing the sintering temperature to 1100°C resulted in increasing the water absorption of the kaolin-based geopolymer ceramic.

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The Investigation of Ground Granulated Blast Furnace Slag Geopolymer at High Temperature by Using Electron Backscatter Diffraction Analysis

Aziz Ikmal Hakem, Al Bakri Abdullah Mohd Mustafa, Salleh Mohd Arif Anuar Mohd, Yoriya Sorachon, Razak Rafiza Abd, Mohamed Rosnita, Baltatu Madalina Simona

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

227--231

EN

This paper elucidated the potential of electron backscatter diffraction analysis for ground granulated blast furnace slag geopolymers at 1000°C heating temperature. The specimen was prepared through the mechanical ground with sandpaper and diamond pad before polished with diamond suspension. By using advanced technique electron backscatter diffraction, the microstructure analysis and elemental distribution were mapped. The details on the crystalline minerals, including gehlenite, mayenite, tobermorite and calcite were easily traced. Moreover, the experimental Kikuchi diffraction patterns were utilized to generate a self-consistent reference for the electron backscatter diffraction pattern matching. From the electron backscatter diffraction, the locally varying crystal orientation in slag geopolymers sample of monoclinic crystal observed in hedenbergite, orthorhombic crystal in tobermorite and hexagonal crystal in calcite at 1000°C heating temperature.

3

Setting Time and after Setting Properties of High Calcium Fly Ash Geopolymers with Different Concentration of Sodium Hydroxide

Mohamed Rosnita, Abd Razak Rafiza, Al Bakri Abdullah Mohd Mustafa, Sofri Liyana Ahmad, Aziz Ikmal Hakem, Shahedan Noor Fifinatasha

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

563--567

EN

Setting time in geopolymers is known as the time taken for the transition phase of liquid to solid of the geopolymer system in which is represented in the initial setting and final setting. Setting time is significant specifically for application in the construction field. This study intends to determine the setting time of high calcium fly ash geopolymers and the properties of the geopolymers after setting (1-day age). This includes the determination of heat evolved throughout geopolymerization using Differential Scanning Calorimeter. After setting properties determination includes compressive strength and morphology analysis at 1-day age. High calcium fly ash was used as geopolymer precursor. Meanwhile, for mixing design, the alkali activator was a mixture of sodium silicate and sodium hydroxide (concentration varied from 6M-14M) with a ratio of 2.5 and a solid-to-liquid ratio of 2.5. From this study, it was found that high calcium fly ash geopolymer with 12M of NaOH has a reasonable setting time which is suitable for on-site application as well as an optimal heat evolved (-212 J/g) which leads to the highest compressive strength at 1-day age and no formation of microcracks observed on the morphology. Beyond 12M, too much heat evolved in the geopolymer system can cause micro-cracks formation thus lowering the compressive strength at 1-day age.

4

Assessment of Geopolymer Concrete for Underwater Concreting Properties

Zaidi Fakhryna Hannanee Ahmad, Ahmad Romisuhani, Al Bakri Abdullah Mohd Mustafa, Wan Ibrahim Wan Mastura, Aziz Ikmal Hakem, Junaidi Subaer, Luhar Salmabanu

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

677--684

EN

For ages, concrete has been used to construct underwater structures. Concrete laying underwater is a very complex procedure important to the success or failure of underwater projects. This paper elucidates the influence of alkali activator ratios on geopolymers for underwater concreting; focusing on the geopolymer concrete synthesized from fly ash and kaolin activated using sodium hydroxide and sodium silicate solutions. The geopolymer mixtures were designed to incorporate multiple alkali activator ratios to evaluate their effects on the resulting geopolymers’ properties. The fresh concrete was molded into 50 mm cubes in seawater using the tremie method and tested for its engineering properties at 7 and 28 days (curing). The control geopolymer and underwater geopolymers’ mechanical properties, such as compressive strength, water absorption density, and setting time were also determined. The differences between the control geopolymer and underwater geopolymer were determined using phase analysis and functional group analysis. The results show that the geopolymer samples were optimally strengthened at a 2.5 alkali activator ratio, and the mechanical properties of the control geopolymer exceeded that of the underwater geopolymer. However, the underwater geopolymer was determined to be suitable for use as underwater concreting material as it retains 70% strength of the control geopolymer.