A.R. Rafiza

The Relationship of NaOH Molarity, Na2SiO3/NaOH Ratio, Fly Ash/Alkaline Activator Ratio, and Curing Temperature to the Strength of Fly Ash-Based Geopolymer

Geopolymer, produced by the reaction of fly ash with an alkaline activator (mixture of Na2SiO3 and NaOH solutions), is an alternative to the use of ordinary Portland cement (OPC) in the construction industry. However, there are salient parameters that affecting the compressive strength of geopolymer. In this research, the effects of various NaOH molarities, Na2SiO3/NaOH ratios, fly ash/alkaline activator, and curing temperature to the strength of geopolymer paste fly ash were studied. Tests were carried out on 50 x 50 x 50 mm cube geopolymer specimens. Compression tests were conducted on the seventh day of testing for all samples. The test results revealed that a 12 M NaOH solution produced the highest compressive strength for the geopolymer. The combination mass ratios of fly ash/alkaline activator and Na2SiO3/NaOH of 2.0 and 2.5, respectively, produced the highest compressive strength after seven days. Geopolymer samples cured at 60 °C produced compressive strength as high as 70 MPa.

Correlation between Na2SiO3/NaOH Ratio and Fly Ash/Alkaline Activator Ratio to the Strength of Geopolymer

Geopolymer requires an alkaline activator to induce it pozzolanic property and to accelerate the geopolymerisation process. The geopolymerisation process occurs due to the mixing of fly ash, sodium silicate and sodium hydroxide as the alkaline activator, which produces aluminosilicate gel that acts as a binder. As such, the ratios of fly ash to alkaline activator and Na2SiO3/NaOH play an important role in obtaining desirable compressive strength; the concentration of NaOH used in this study was 12 M. Different ratios of fly ash to alkaline activator (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0) and Na2SiO3/NaOH (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0) were investigated in order to determine the maximum compressive strength. The alkaline activator was mixed with fly ash with different ratio as mentioned above and the samples were cured at 70°C for 24 hours and tested on the seventh day. The maximum compressive strength was obtained when the ratios of fly ash to alkaline activator and Na2SiO3/NaOH were 2.0 and 2.5 with compressive strength 73.86 MPa.

Mechanical properties and wear behavior of brake pads produced from palm slag

Brake pads are important safety devices in vehicles. An effort to avoid the use of asbestos in brake pads has led to the development of asbestos-free brake pads that incorporate various organic and inorganic fillers. Palm slag as a filler in brake pads was investigated in this paper. Different processing pressures were employed during production of samples through compression molding. The properties examined included hardness, compressive strength, and wear behavior. The results showed that brake pad samples prepared with 60 tons of compression pressure resulted in the most desirable properties. Hence, palm slag has its own potential for use as a filler in asbestos-free brake pads.

Optimization of Alkaline Activator/Fly ASH Ratio on the Compressive Strength of Manufacturing Fly ASH-BASED Geopolymer

Fly ash and a mixture of alkaline activators namely sodium silicate (Waterglass) and sodium hydroxide (NaOH) solution were used for preparing geopolymer. The aim of this research is to determine the optimum value of the alkaline activator/fly ash ratio. The effect of the oxide molar ratios of SiO2/Al2O3, water content of the alkaline activator and the Waterglass% content were studied for each Alkaline activator/fly ash ratio. The geopolymers were synthesized by the activation of fly ash with alkaline solution at three different alkaline activator/fly ash ratios which were 0.3, 0.35, and 0.4 at a specific constant ratio of waterglass/NaOH solution of 1.00. The geopolymers were cured at 70°C for 24 h and cured to room temperature. Results revealed that the alkaline activator/fly ash ratio of 0.4 has the optimum amount of alkaline liquid, which shows the highest rate of geopolymerization compared to other ratios. A high strength of 8.61 MPa was achieved with 0.4 of activator/fly ash ratio and 14% of waterglass content.

Study on Physical and Chemical Properties of Fly Ash from Different Area in Malaysia

Fly ash is residue from the combustion of coal which widely available in worldwide and lead to waste management proposal. Moreover, the use of fly ash is more environmental friendly and save cost compared to OPC. Fly ash mostly consists of silicon dioxide (SiO2), aluminium oxide (Al2O3) and iron oxide (Fe2O3). The chemical compositions of the sample have been examined according to ASTM C618. Different sources of fly ash may result in different chemical composition. The fly ash is mainly an amorphous material with the presents of crystalline phase of quartz and mullite. Fly ash consists of mostly glassy, hollow and spherical particles.

Feasibility of Producing Wood Fibre-Reinforced Geopolymer Composites (WFRGC)

Wood fibres have long been known as a fibre reinforcement for concrete. Due to its availability and low production cost, this natural fibre has been used in less developed country where conventional construction materials were very expensive. In Japan, the production of these types of composites such as high performance fibre-reinforced cement-based composite (HPFRCB), ultra high performance (UHPFRCB) and strain-hardening (SHCC) fibre-reinforced cement-based composite has been developed rapidly in last decades. Geopolymer, future composite and cement produced by the alkali-activation reaction is well known as a potential replacement to Ordinary Portland Cement. This study aims at studying the possibility to produce wood fibre-reinforced geopolymer composite (WFRGC). The various percentage of fibre have been made from 10% to 50% and cured at 60C, tested for compressive strength for 7th and 14th day and the microstructure examined using SEM. The density and water absorption test have been performed. The results showed are encouraging and indicate the feasibility of producing a wood fibre-reinforced geopolymer composite (WFRGC).

Characterization of LUSI Mud Volcano as Geopolymer Raw Material

The mud of mud volcano samples were collected from an eruption site named ‘LUSI’ (Lumpur “mud” –Sidoarjo), East Java, Indonesia for characterization. Analysis showed that, the major constituents of mud are SiO2 and Al2O3 which are higher than those in fly ash. The particle of mud has a flake-shaped particle and the overall particle size is dominated by particles between 2.5µm – 25.0µm. The results of XRD shows that mud of mud volcano have a characteristic of structurally disordered compounds, and a set of peaks corresponding to minor crystalline phases such as quartz, feldspars, and kaolinite. FTIR adsorption bands of the raw material of mud have the chemical bonding between bands 1-5.

Influence of Dolomite on the Mechanical Properties of Boiler Ash Geopolymer Paste

The waste material from palm oil industry has been increasing since Malaysia was the world largest exported of palm oil mill. The waste such as palm fibers, nut shells, palm kernel and empty fruit bunches are the solid waste the obtained from palm oil processing for oil extraction. When these wastes were incinerated, the waste from the burning process known as boiler ash was obtained at the lower compartment of the boiler. The production of boiler ash was estimated to be over 4 million tones/ year. This paper investigates the influence of dolomite on the mechanical properties of boiler ash based geopolymer pastes. The boiler ash was calcined at 800oC for 1 hour. After that, the dolomite was replaced in boiler ash at 1, 2, 3, 4 and 5% wt where the geopolymer samples were cured 80 oC. Sodium silicate and sodium hydroxide (NaOH) with concentration 12 Molar has been used as alkaline activator to synthesis the boiler ash to produce geopolymer paste. The ratio of solid/liquid and sodium silicate/NaOH was 1 and 2.5 for all geopolymer paste. The result showed the addition of dolomite has decrease the strength of boiler ash based geopolymer. The geopolymer sample without addition of dolomite showed the maximum compressive strength (19.4 MPa) at 28 days testing. Meanwhile the addition of 4% of dolomite into geopolymer paste has the maximum compressive strength (7.3 MPa) compared to others. Additions of dolomite into boiler ash based geopolymer have reduced the compressive strength at 28 days of testing.

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.

Microstructure Studies on the Effect of the Alkaline Activators of Fly Ash-Based Geopolymer at Elevated Heat Treatment Temperature

Fly ash-based geopolymers are new binding materials produced to replace the ordinary Portland cement (OPC) used in concrete. In this research, the effect of alkaline activators on the compressive strength and the microstructure of low-calcium (Class F) fly ash-based geopolymers were studied. Fly ash and the alkaline activator were mixed with alkaline activator to fly ash ratios of 0.30, 0.35, and 0.40 at a constant ratio of water glass (sodium silicate) to sodium hydroxide (NaOH). The alkaline activator solution was prepared by mixing water glass with a 15 M NaOH solution. The samples were cured at a temperature 70 °C for 24 hr and maintained at room temperature until the testing was conducted. The test results indicated that the compressive strength increased when the ratio of alkaline activator to fly ash was increased at 7 days. The ratio of 0.4 produced the maximum compressive strength, which was 8.61 MPa. This was due to high reaction rate between the fly ash and the alkaline activator solution. Morphology studies, conducted by SEM analysis of the geopolymer samples, indicated that geopolymers synthesized at a ratio of 0.4 also had the most homogeneous and less porous microstructures, which was attributed to the high dissolution of the fly ash particles in the alkaline activator solution. The microstructure appearance of geopolymers treated heat temperature of 400, 600 and 800°C, shows a sintering process takes place for unreacted fly ash microspheres. It was observed as an overall, the visible microcracks formed on the surface of the highest compressive strength geopolymers only, was due to loss of water during heating.