Ismail Khairul Nizar

Microstructure Study on Optimization of High Strength Fly Ash Based Geopolymer

The compressive strength and microstructural characteristics of fly ash based geopolymer with alkaline activator solution were investigated. The sodium hydroxide and sodium silicate were mixed together to form an alkaline activator. Three parameters including NaOH molarity, mix design (fly ash/alkaline activator ratio and Na2SiO3/NaOH ratio), and curing temperature were examined. The maximum strength of 71 MPa was obtained when the NaOH solution of 12M, fly ash/alkaline activator of 2.0, Na2SiO3/NaOH of 2.5 and curing temperature of 60°C were used at 7th days of testing. The results of SEM indicated that for geopolymer with highest strength, the structure was dense matrix and contains less unreacted fly ash with alkaline activator

Influence of Solidification Process on Calcined Kaolin Geopolymeric Powder

This paper aims at investigating the influence of solidification condition on the processing of calcined kaolin geopolymeric powder. This is a new process developed using the geopolymerization process. Geopolymer slurry was prepared from calcined kaolin and activating solution (mixture of NaOH and Na2SiO3). This slurry was allowed to solidify in oven and then crushed and grounded to fixed particle size. Compressive testing and SEM analysis were performed in this study. The results showed that the solidification condition at 80 °C for 4 hours was the best to synthesize the geopolymeric powder where this solidification condition results in geopolymeric powder which can produce higher strength resulted geopolymer paste. The microstructure showed more intervening gel phase which indicates that the geopolymerization process continued to react after the addition of water to the calcined kaolin geopolymeric powder.

Effect of Mechanical Activation on Kaolin-Based Geopolymers

Raw materials kaolin was subjected to mechanical modification; the effect of the mechanical activation of kaolin on the compressive strength and morphological properties of the geopolymers has been studied. Mechanical activation of the kaolin results in particle size reduction and morphology changes with increase in reactivity. Mechanical activated kaolin has overall higher strength gain compared to raw kaolin. Wider particle size distribution and some spherical particles produced, promote a higher packaging density in the sample resulting in higher strength obtained. Mechanically activation of kaolin can be considered as an alternative method to achieve better geopolymerization reaction for kaolin-based geopolymer.

The Influence of Curing Periods on the Compressive Strength of Fly Ash-Based Geopolymer at Different Aging Times

Omar A. Abdulkareem1a, A.M. Mustafa Al Bakri1b, H. Kamarudin1c, and I. Khairul Nizar2d 1Center of Excellence Geopolymer System Research, School of Material Engineering, Universiti Malaysia Perlis (UniMAP), P.O. Box 77, D/A Pejabat Pos Besar, Kangar, Perlis, 01000, Malaysia. 2School of Environmental Engineering, Universiti Malaysia Perlis (UniMAP), Box 77, D/A Pejabat Pos Besar, Kangar, Perlis, 01000, Malaysia. aeng.omar83@yahoo.com,bmustafa_albakri@unimap.edu.my, cvc@unimap.edu.my, dnizar@unimap.edu.my. Keywords: curing periods, geopolymerization, alkaline activator, compressive strength, fly ash.

Microstructure Study on Volcano Ash Geopolymer Aggregate at Different Sintering Temperature

Recent research shows that the by-product materials such as fly ash can be used as raw material in producing aggregates and lightweight aggregates. The usage of this material can improve the quality of the aggregates produced compared to conventional in term of structurally strong, physically stable, durable, and environmentally inert. However, volcano ash also has a potential to be used as artificial geopolymer aggregate due to high Si and Al contents. This volcano ash is almost dominated by quartz phase and sulfur. Volcano ash has plate-like structure. The structure of original volcano ash shows more layer stick together to form the bigger structure due to the existence of water. More large pores can be clearly observed at sintering temperature of 1000 °C and contribute to less density and have potential to be used as lightweight artificial geopolymer aggregate.

Effect of curing regimes on metakaolin geopolymer pastes produced from geopolymer powder

The properties of metakaolin geopolymer paste are affected by the alkali concentration, the initial raw materials, solidification process, and amount of mixing water as well as the curing conditions. This study aimed to investigate the effect of curing temperature (room temperature, 40°C, 60°C, 80°C and 100°C) and curing time (6h, 12h, 24h, 48h and 72h) on the geopolymer pastes produced from geopolymer powder. The results showed that curing at room temperature was unfeasible. Heat was required for the geopolymerization process, where strength increased as the curing temperature was increased. Moderate elevated curing temperature favored the strength development of geopolymer pastes in comparison with those treated with extreme elevated curing temperature. When geopolymer paste was subjected to extreme elevated curing temperature, shorter curing time should be used to avoid deterioration in strength gain. Similarly, longer curing time was recommended for moderate elevated curing temperature. The microstructure of geopolymer paste cured at moderate curing temperature showed obvious densification of structure. In contrast, the structure formed was weak and less compact at very high elevated curing temperature.