Romisuhani Ahmad
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Preferred name
Romisuhani Ahmad
Official Name
Romisuhani, Ahmad
Alternative Name
Ahmad, Romisuhani
Romisuhani, Ahmad
Romisuhani, A.
Ahmad, R.
Main Affiliation
Scopus Author ID
56354732400
Researcher ID
AAA-1058-2021

Research Output
Now showing 1 - 6 of 6
  • Publication
    Effect of the sintering mechanism on the crystallization kinetics of geopolymer-based ceramics
    (MDPI, 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.
  • Publication
    Densification behavior and mechanical performance of Nepheline geopolymer ceramics: preliminary study
    (Springer, 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.
  • Publication
    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.
      3  24
  • Publication
    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.
      3  42
  • Publication
    Potential of soil stabilization using Ground Granulated Blast Furnace Slag (GGBFS) and fly ash via geopolymerization method: a review
    ( 2022)
    Syafiadi Rizki Abdila
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Romisuhani Ahmad
    ;
    Dumitru Doru Burduhos Nergis
    ;
    Shayfull Zamree Abd. Rahim
    ;
    Mohd Firdaus Omar
    ;
    Andrei Victor Sandu
    ;
    Petrica Vizureanu
    Geopolymers, or also known as alkali-activated binders, have recently emerged as a viable alternative to conventional binders (cement) for soil stabilization. Geopolymers employ alkaline activation of industrial waste to create cementitious products inside treated soils, increasing the clayey soils’ mechanical and physical qualities. This paper aims to review the utilization of fly ash and ground granulated blast furnace slag (GGBFS)-based geopolymers for soil stabilization by enhancing strength. Previous research only used one type of precursor: fly ash or GGBFS, but the strength value obtained did not meet the ASTM D 4609 (<0.8 Mpa) standard required for soil-stabilizing criteria of road construction applications. This current research focused on the combination of two types of precursors, which are fly ash and GGBFS. The findings of an unconfined compressive strength (UCS) test on stabilized soil samples were discussed. Finally, the paper concludes that GGBFS and fly-ash-based geo-polymers for soil stabilization techniques can be successfully used as a binder for soil stabilization. However, additional research is required to meet the requirement of ASTM D 4609 standard in road construction applications, particularly in subgrade layers.
      22  1
  • Publication
    Chemical distributions of different Sodium Hydroxide molarities on fly ash/dolomite-based geopolymer
    ( 2022)
    Wan Mastura Wan Ibrahim
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Romisuhani Ahmad
    ;
    Andrei Victor Sandu
    ;
    Petrica Vizureanu
    ;
    Omrane Benjeddou
    ;
    Afikah Rahim
    ;
    Masdiyana Ibrahim
    ;
    Ahmad Syauqi Sauffi
    Geopolymers are an inorganic material in an alkaline environment that is synthesized with alumina–silica gel. The structure of geopolymers consists of an inorganic chain of material and a covalent-bound molecular system. Currently, Ordinary Portland Cement (OPC) has caused carbon dioxide (CO2) emissions which causes greenhouse effects. This analysis investigates the impact on fly ash/dolomite-based-geopolymer with various molarities of sodium hydroxide solutions which are 6 M, 8 M, 10 M, 12 M and 14 M. The samples of fly ash/dolomite-based-geopolymer were prepared with the usage of solid to liquid of 2.0, by mass and alkaline activator ratio of 2.5, by mass. After that, the geopolymer was cast in 50 × 50 × 50 mm molds before testing after 7 days of curing. The samples were tested on compressive strength, density, water absorption, morphology, elemental distributions and phase analysis. From the results, the usage of 8 M of NaOH gave the optimum properties for the fly ash/dolomite-based geopolymer. The elemental distribution analysis exposes the Al, Si, Ca, Fe and Mg chemical distribution of the samples from the selected area. The distribution of the elements is related to the compressive strength and compared with the chemical composition of the fly ash and dolomite.
      1  18