Heah Cheng Yong
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Preferred name
Heah Cheng Yong
Official Name
Heah, Cheng Yong
Alternative Name
Yong, Heah Cheng
Yong, H. C.
Heah, Cheng Yong
Heah, C. Y.
Cheng-Yong, Heah
Cheng Yong, Heah
Main Affiliation
Scopus Author ID
54402789500
Researcher ID
S-7139-2019

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  • Publication
    Sintered and unsintered pressed fly ash geopolymer: A comprehensive study on structural transformation in nitric and sulfuric acid
    ( 2024-09-15)
    Shee-Ween O.
    ;
    Heah Cheng Yong
    ;
    Liew Yun Ming
    ;
    Ho Li Ngee
    ;
    Wei-Hao L.
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Wei-Ken P.
    ;
    Yong-Jie H.
    ;
    Pin-Hsun L.
    Acidic attacks contribute to the degradation of cementitious materials, diminishing the structural service life and increasing the requirement for maintenance of the structure. To address the limited understanding of the impact of the sintering process on the acid resistance of pressed geopolymer, an investigation and comparison of the acid resistance of room-cured (RPG) and sintered (SPG) pressed geopolymer was performed. Specimens were immersed in 3 % and 8 % nitric (HNO3) and sulfuric (H2SO4) acids for 7 and 28 days. Despite the higher sorptivity, SPG demonstrated better mechanical strength retention than that of RPG. Specifically, the compressive strength of SPG after 3 % of HNO3 immersion for 28 days increased (+14.2 %), surpassing the control specimen, while RPG experienced a 14.5 % strength drop. The strength increment in SPG was due to the further geopolymerization during acid immersion. In RPG, a new crystalline phase of NaNO3 was observed after immersion in 8 % HNO3 for 28 days. In contrast, SPG showed no evidence of NaNO3 formation, indicating lower reactivity with HNO3 compared to RPG. Additionally, both RPG and SPG exhibited gypsum formation after immersion in H2SO4. The presence of gypsum induced crack formation in RPG, whereas SPG, with its intensive cross-linked structure, effectively compensated for gypsum expansion, preventing crack formation. This finding is crucial for practical applications where exposure to aggressive acids is a concern, as it provides a method to enhance the acid resistance of geopolymer structures.
      1
  • Publication
    Green development of fly ash geopolymer via casting and pressing Approaches: Strength, Morphology, efflorescence and Ecological Properties
    ( 2023-09-22)
    Shee-Ween O.
    ;
    Heah Cheng Yong
    ;
    Liew Yun Ming
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Ho Li Ngee
    ;
    Pakawanit P.
    ;
    Suhaimi Khalid M.
    ;
    Hazim Bin Wan Muhammad W.
    ;
    Wan-En O.
    ;
    Yong-Jie H.
    ;
    Yong-Sing N.
    ;
    Hui-Teng N.
    The high liquid content of cast geopolymer not only limits its strength development and durability but also leads to high energy consumption and carbon dioxide (CO2) emissions. Thus, a study of the cast and pressed geopolymer was performed. The geopolymers were cured for 1, 7 and 28 d before testing and characterizations. With the incorporation of pressure compaction, higher bulk density (2158–2227 kg/m3) was recorded for pressed geopolymer in comparison to cast geopolymer (1842–1854 kg/m3). The dense matrix in pressed geopolymer improved the inter-particle contact, increasing the 28 d degree of reaction to 39.7%, higher than that of cast geopolymer (33.0%). This feature was proved by SEM micrographs wherein the pressed geopolymer was well-compacted and denser in microstructure, with less unreacted/partially reacted fly ash and pores. The compressive and flexural strengths of pressed geopolymer reached 114.2 and 29.9 MPa after 28 d, higher than that of cast geopolymer (60.0 and 6.2 MPa, respectively). The strength reduction of pressed geopolymer (31.7%) after the accelerated efflorescence test was lower than that of cast geopolymer (60.2%). The ecological analysis inferred that pressed geopolymer was ecologically superior to the casting method in terms of embodied energy (EE) and embodied carbon dioxide emission (ECO2), in which 50% and 59% of reductions are acquired. Besides, the embodied carbon index (ECI) of pressed geopolymer was about 21% of cast geopolymer.
      3