Romisuhani Ahmad
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Romisuhani Ahmad
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Romisuhani, Ahmad
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Ahmad, Romisuhani
Romisuhani, Ahmad
Romisuhani, A.
Ahmad, R.
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56354732400
Researcher ID
AAA-1058-2021

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Effect of the sintering mechanism on the crystallization kinetics of geopolymer-based ceramics

2023 , Nur Bahijah Mustapa , Romisuhani Ahmad , Andrei Victor Sandu , Mohd. Mustafa Al Bakri Abdullah , Ovidiu Nemes , Wan Mastura Wan Ibrahim , Petrica Vizureanu , Christina Wahyu Kartikowati , Puput Risdanareni

This research aims to study the effects of the sintering mechanism on the crystallization kinetics when the geopolymer is sintered at different temperatures: 200 °C, 400 °C, 600 °C, 800 °C, 1000 °C, and 1200 °C for a 3 h soaking time with a heating rate of 5 °C/min. The geopolymer is made up of kaolin and sodium silicate as the precursor and an alkali activator, respectively. Characterization of the nepheline produced was carried out using XRF to observe the chemical composition of the geopolymer ceramics. The microstructures and the phase characterization were determined by using SEM and XRD, respectively. The SEM micrograph showed the microstructural development of the geopolymer ceramics as well as identifying reacted/unreacted regions, porosity, and cracks. The maximum flexural strength of 78.92 MPa was achieved by geopolymer sintered at 1200 °C while the minimum was at 200 °C; 7.18 MPa. The result indicates that the flexural strength increased alongside the increment in the sintering temperature of the geopolymer ceramics. This result is supported by the data from the SEM micrograph, where at the temperature of 1000 °C, the matrix structure of geopolymer-based ceramics starts to become dense with the appearance of pores.

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Assessment of geopolymer concrete for underwater concreting properties

2021 , Fakhryna Hannanee Ahmad Zaidi , Romisuhani Ahmad , Mohd. Mustafa Al Bakri Abdullah , Wan Mastura Wan Ibrahim , Ikmal Hakem Aziz , Subaer Junaidi , Salmabanu Luhar

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.

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Geopolymer-based nepheline ceramics: effect of sintering profile on morphological characteristics and flexural strength

2022 , Romisuhani Ahmad , Wan Mastura Wan Ibrahim , Mohd. Mustafa Al Bakri Abdullah , Phakkhananan Pakawanit , Petrica Vizureanu , Arman Shah Abdullah , Andrei Victor Sandu , Fakhryna Hannanee Ahmad Zaidi

The focus of this study is the fabrication of innovative and sustainable ceramic-based geopolymer with improved low temperatures performances. Kaolin was mixed with liquid sodium silicate (Na₂SiO₃) and 12M of sodium hydroxide (NaOH) solution using alkali activator ratio of 0.24 and solid-to-liquid ratio of 1:1 to synthesize kaolin geopolymer. The effect of the sintering profile on the microstructure, pore evolution and flexural strength were investigated. The heating exposure aided consolidation and created a fairly uniform microstructure, resulting in a smooth surface texture. In comparison to the unheated geopolymer, 3D pore distribution showed a significant increase in the range size of ~30 µm with the appearance of isolated and intergranular pores. The flexural strength at 1200 °C with a heating rate of 5 °C/min and was increased by 146.4% to 85.4 MPa, as compared to the heating rate of 2 °C/min. The sintering process has an impact on the final microstructure formation thus improving the characteristic of geopolymer-based nepheline ceramic.

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Development of kaolin geopolymer ceramic with addition of ultra high molecular weight polyethylene (UHMWPE) as binder for lightweight ceramics

2018 , Romisuhani Ahmad

A lightweight ceramic material displays physical, mechanical and structural features which is highly preferred in modern ceramic industry. Geopolymer technology has been involved in many applications including in the formation of ceramic. The transformation phase of geopolymer from amorphous to crystalline upon heating require a low processing temperature compared to the conventional ceramics. A major synthetic process for industrialised lightweight ceramics is to use additives which are organic in nature such as binders, plasticizers, surfactants and lubricants.This study investigated the use of geopolymer in producing ceramic materials where kaolin was used as main source material and Ultra High Molecular Weight Polyethylene was added as binder. In this study, the solid-to-liquid ratio of 1.0 and alkaline activator ratio of 0.24 were fixed. Kaolin geopolymer were then cured at 80 °C for 24 hours, the samples were then crushed into powder form. By using powder metallurgy method in producing kaolin geopolymer ceramic, three parameters used are sintering temperature (900 °C, 1000 °C, 1100 °C, 1200 °C), binder content (2 wt.%, 4 wt.%, 6 wt.%, 8 wt.%) and sintering method which are conventional and two-steps sintering method. The optimum weight percent of binder were studied by fixing the sintering temperature, while the optimum of sintering temperature were studied by fixing the weight percent of binder based on testing of flexural strength, density, shrinkage, and water absorption. The results indicated that kaolin geopolymer ceramic with the addition of 4 wt.% of Ultra High Molecular Weight Polyethylene sintered at 1200 °C using two steps sintering method could achieve an optimum strength of 94.32 MPa with a density of 1.71 g/cm3. Also a smooth surface and increasing in formation of pores were observed, which would facilitate the formation of the lightweight and strong structure. Then, the performance of kaolin geopolymer lightweight ceramic was examined by performing microstructural and mechanical properties tests. The outcomes revealed the possibility to produce a lightweight ceramic based kaolin-geopolymer with a considerable characteristics and mechanical properties, which could open the door for many applications in the future. Geopolymer based lightweight ceramic has been claimed as a promising material, due to its ability to produce a high-performance lightweight ceramic and because of its relevant environmental and economic benefits. Furthermore, lower-powered mechanical and thermal treatments are required to ensure the excellent properties and quality to produce the lightweight ceramic materials lead to a positive effect on the environment hence suitable with the desire for eco-friendly industry.

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Densification behavior and mechanical performance of Nepheline geopolymer ceramics: preliminary study

2023 , Nur Bahijah Mustapa , Romisuhani Ahmad , Mohd. Mustafa Al Bakri Abdullah , Wan Mastura Wan Ibrahim , Andrei Victor Sandu , Christina Wahyu Kartikowati , Puput Risdanareni , Wan Hasnida Wan Mohamed Saimi

Nepheline geopolymer ceramics have emerged as a promising sustainable alternative to traditional cementitious materials in various applications. As the sintering mechanism plays a crucial role in the densification and mechanical performance of ceramics, therefore, in this paper, a preliminary study was conducted to examine the effects of densification towards mechanical properties of geopolymer-based nepheline ceramics upon sintering. The said innovative geopolymer technology can convert raw materials of aluminosilicate activating with alkaline activator into ceramic-like materials requiring low temperatures. The experimental procedure includes the synthesis of nepheline geopolymer ceramics through the geopolymerization method, then sintered at different temperatures to explore the sintering behavior and its impact on the materials’ microstructure and mechanical performance. The densification behavior of nepheline geopolymer ceramics during sintering was analyzed by evaluating the changes in density, shrinkage, and porosity. The microstructural evolution and are determined by using SEM. The relationships between sintering conditions, microstructure, and mechanical performance were investigated to understand the underlying mechanisms affecting the material’s strength and durability. The geopolymer exhibited its highest flexural strength of 54.93 MPa when sintered at 1200 ℃, while the lowest strength of 6.07 MPa was observed at a sintering temperature of 200 ℃. The findings demonstrate a positive correlation between the sintering temperature and the flexural strength of the geopolymer ceramics, indicating that higher temperatures lead to increased strength. Ultimately, this knowledge can facilitate the broader utilization of nepheline geopolymer ceramics as sustainable materials in various engineering and construction applications.

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Evaluation on the mechanical properties of Ground Granulated Blast Slag (GGBS) and fly ash stabilized soil via geopolymer process

2021 , Syafiadi Rizki Abdila , Mohd. Mustafa Al Bakri Abdullah , Romisuhani Ahmad , Shayfull Zamree Abd. Rahim , Małgorzata Rychta , Izabela Wnuk , Marcin Nabiałek , Krzysztof Muskalski , Muhammad Faheem Mohd. Tahir , Muhammad Syafwandi , Marek Isradi

This study intended to address the problem of damaged (collapsed, cracked and decreased soil strength) road pavement structure built on clay soil due to clay soil properties such as low shear strength, high soil compressibility, low soil permeability, low soil strength, and high soil plasticity. Previous research reported that ground granulated blast slag (GGBS) and fly ash can be used for clay soil stabilizations, but the results of past research indicate that the road pavement construction standards remained unfulfilled, especially in terms of clay’s subgrade soil. Due to this reason, this study is carried out to further investigate soil stabilization using GGBS and fly ash-based geopolymer processes. This study investigates the effects of GGBS and ratios of fly ash (solid) to alkaline activator (liquid) of 1:1, 1.5:1, 2:1, 2.5:1, and 3:1, cured for 1 and 7 days. The molarity of sodium hydroxide (NaOH) and the ratio of sodium silicate (Na2SiO3) to sodium hydroxide (NaOH) was fixed at 10 molar and 2.0 weight ratio. The mechanical properties of the soil stabilization based geopolymer process were tested using an unconfined compression test, while the characterization of soil stabilization was investigated using the plastic limit test, liquid limit test, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results showed that the highest strength obtained was 3.15 MPA with a GGBS to alkaline activator ratio of 1.5 and Na2SiO3 to NaOH ratio of 2.0 at 7 days curing time. These findings are useful in enhancing knowledge in the field of soil stabilization-based geopolymer, especially for applications in pavement construction. In addition, it can be used as a reference for academicians, civil engineers, and geotechnical engineers.

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Crumb rubber geopolymer mortar at elevated temperature exposure

2022 , Ahmad Azrem Azmi , Mohd. Mustafa Al Bakri Abdullah , Che Mohd Ruzaidi Ghazali , Romisuhani Ahmad , Ramadhansyah Putra Jaya , Shayfull Zamree Abd. Rahim , Mohammad A. Almadani , Wysłocki, Jerzy J. , Agata Śliwa , Andre Victor Sandu

Low calcium fly ash is used as the main material in the mixture and the crumb rubber was used in replacing fine aggregates in geopolymer mortar. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) which were high alkaline solution were incorporated as the alkaline solution. The fly ash reacted with the alkaline solution forming alumino-silicate gel that binds the aggregate to produce a geopolymer mortar. The loading of crumb rubber in the fly ash based geopolymer mortar was set at 0%

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Role of sintering temperature in production of nepheline ceramics-based geopolymer with addition of ultra-high molecular weight polyethylene

2021 , Romisuhani Ahmad , Mohd. Mustafa Al Bakri Abdullah , Jitrin Chaiprapa , Kamarudin Hussin , Wan Mastura Wan Ibrahim , Fakhryna Hannanee Ahmad Zaidi , Jerzy J. Wysłocki , Katarzyna Błoch , Marcin Nabiałek

The primary motivation of developing ceramic materials using geopolymer method is to minimize the reliance on high sintering temperatures. The ultra-high molecular weight polyethylene (UHMWPE) was added as binder and reinforces the nepheline ceramics based geopolymer. The samples were sintered at 900 °C, 1000 °C, 1100 °C, and 1200 °C to elucidate the influence of sintering on the physical and microstructural properties. The results indicated that a maximum flexural strength of 92 MPa is attainable once the samples are used to be sintered at 1200 °C. It was also determined that the density, porosity, volumetric shrinkage, and water absorption of the samples also affected by the sintering due to the change of microstructure and crystallinity. The IR spectra reveal that the band at around 1400 cm−1 becomes weak, indicating that sodium carbonate decomposed and began to react with the silica and alumina released from gels to form nepheline phases. The sintering process influence in the development of the final microstructure thus improving the properties of the ceramic materials.

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Effect of the sintering mechanism on the crystallization kinetics of Geopolymer-Based ceramics

2023 , Nur Bahijah Mustapa , Romisuhani Ahmad , Mohd. Mustafa Al Bakri Abdullah , Wan Mastura Wan Ibrahim , Andrei Victor Sandu , Ovidiu Nemes , Petrica Vizureanu , Christina W. Kartikowati , Puput Risdanareni

This research aims to study the effects of the sintering mechanism on the crystallization kinetics when the geopolymer is sintered at different temperatures: 200 °C, 400 °C, 600 °C, 800 °C, 1000 °C, and 1200 °C for a 3 h soaking time with a heating rate of 5 °C/min. The geopolymer is made up of kaolin and sodium silicate as the precursor and an alkali activator, respectively. Characterization of the nepheline produced was carried out using XRF to observe the chemical composition of the geopolymer ceramics. The microstructures and the phase characterization were determined by using SEM and XRD, respectively. The SEM micrograph showed the microstructural development of the geopolymer ceramics as well as identifying reacted/unreacted regions, porosity, and cracks. The maximum flexural strength of 78.92 MPa was achieved by geopolymer sintered at 1200 °C while the minimum was at 200 °C; 7.18 MPa. The result indicates that the flexural strength increased alongside the increment in the sintering temperature of the geopolymer ceramics. This result is supported by the data from the SEM micrograph, where at the temperature of 1000 °C, the matrix structure of geopolymer-based ceramics starts to become dense with the appearance of pores.

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Phase analysis of different liquid ratio on Metakaolin/Dolomite geopolymer

2021 , Ahmad Syauqi Sauffi , Wan Mastura Wan Ibrahim , Mohd. Mustafa Al Bakri Abdullah , Masdiyana Ibrahim , Romisuhani Ahmad , Fakhryna Ahmad Zaidi

Geopolymer is widely studied nowadays in various scope of studies. Some of the ongoing studies are the study of the various materials towards the geopolymer strength produced. Meanwhile, some of the studies focus on the mixing of the geopolymer itself. This paper discussed the phase analysis of metakaolin/dolomite geopolymer for different solid to the liquid ratio which was, 0.4, 0.6, 0.8, and 1.0, and the properties that affected the geopolymer based on the phases. The constant parameters in this study were the percentage of metakaolin and dolomite used. The metakaolin used was 80% meanwhile dolomite usage was 20%. Besides that, the molarity of NaOH used is 10M and the alkaline activator ratio used is 2.0. All the samples were tested at 28 days of curing. The results show that the 0.8 solid to the liquid ratio used gave better properties compare to other solid to liquid ratio. The phases analyzed were quartz, sillimanite, mullite, and faujasite. The 0.8 S/L ratio shows the better properties compared to others by the test of phase analysis, compressive strength morphology analysis, and functional group analysis.

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