Zarina Yahya
Thumbnail Image
Preferred name
Zarina Yahya
Official Name
Zarina, Yahya
Alternative Name
Yahya, Zarina
Zarina, Y.
Zarina, Yahya
Main Affiliation
Scopus Author ID
51162069600
Researcher ID
DXZ-6436-2022

Research Output

Filters

Show more
Reset filters

Settings
Now showing 1 - 2 of 2
  • Publication
    Behavior of alkali-activated fly ash through underwater placement
    ( 2021-11-01)
    Zarina Yahya
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Li Long-Yuan
    ;
    Nergis D.D.B.
    ;
    Muhammad Aiman Asyraf Zainal Hakimi
    ;
    Sandu A.V.
    ;
    Vizureanu P.
    ;
    Rafiza Abd Razak
    Underwater concrete is a cohesive self-consolidated concrete used for concreting underwater structures such as bridge piers. Conventional concrete used anti-washout admixture (AWA) to form a high-viscosity underwater concrete to minimise the dispersion of concrete material into the surrounding water. The reduction of quality for conventional concrete is mainly due to the washing out of cement and fine particles upon casting in the water. This research focused on the detailed investigations into the setting time, washout effect, compressive strength, and chemical composition analysis of alkali-activated fly ash (AAFA) paste through underwater placement in seawater and freshwater. Class C fly ash as source materials, sodium silicate, and sodium hydroxide solution as alkaline activator were used for this study. Specimens produced through underwater placement in seawater showed impressive performance with strength 71.10 MPa on 28 days. According to the Standard of the Japan Society of Civil Engineers (JSCE), the strength of specimens for underwater placement must not be lower than 80% of the specimen’s strength prepared in dry conditions. As result, the AAFA specimens only showed 12.11% reduction in strength compared to the specimen prepared in dry conditions, thus proving that AAFA paste has high potential to be applied in seawater and freshwater applications.
      2
  • Publication
    Seawater Exposure Effect on Fly Ash based Geopolymer Concrete with Inclusion of Steel Fiber
    ( 2020-03-18)
    Zarina Yahya
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Jing L.Y.
    ;
    Li L.Y.
    ;
    Rafiza Abd Razak
    Concrete is widely used in construction offshore such as concrete floating bridges and sea tank. This research is providing an alternative construction material to replace ordinary Portland cement (OPC) concrete known as geopolymer. The geopolymer concrete was produced by mixing fly ash with alkaline activator and 3% of steel fibre in order to improve the properties of fiber reinforced geopolymer concrete (FRGPC). The effects of aging period in term of strength, changes in weight and carbonation of FRGPC in seawater is investigated and compared with the fiber reinforced concrete (FROPC). The compressive strength obtained for FRGPC were higher than FROPC. The highest compressive strength obtained by FRGPC is 76.87 MPa at 28 days and 45.63 MPa at 28 days for FROPC concrete. The compressive strength was decreased as the period of immersing the concrete in seawater is increased. During the immersion process of both samples in seawater up to 120 days, the carbonation was not detected even though with the existence of steel fibres.
      3  21