Chayanee Tippayasam

Geopolymer Development by Powders of Metakaolin and Wastes in Thailand

Geopolymer has been developed as an alternative material to Portland cement. Geopolymer is based on the polymerization of alkaline activation and oxide of silicon and aluminium. These oxides can be found in many pozzolanic materials such as metakaolin and the wastes from industries and agricultures in Thailand, e.g., fly ash, bagasse ash and rice husk ash. Pozzolanic materials were selected as source materials for making geopolymers into 4 different types. Sodium hydroxide concentration of 10 Molar (10MNaOH) and sodium silicate (Na2SiO3) solutions were used as alkaline activators by the mass ratio of Na2SiO3/NaOH at 1.5. The mixtures were cast in 25×25×25 mm. cubes. After casting, the geopolymers were cured at 80๐C for 24 hrs. in an oven and then at room temperature for 7 days. The pozzolanic materials effects, the Si/Al molar ratio and the Na/Al molar ratio were studied and characterized. An X-ray fluorescence (XRF) was chosen to determine the percentages of silica and alumina in order to verify the proper ratio of the fly ash, Rice husk ash, Bagasse ash and Metakaolin.The study also included the impact on mechanical and physical properties such as compressive strength, water absorption, density and porosity.

Metakaolin-Based Porous Geopolymer with Aluminium Powder

Porous concretes such as aerated and lightweight concretes are commonly used in construction fields. Lightweight construction materials are used to reduce either the weight or the budget of building structures. Porous concrete production is widely utilised aluminium (Al) powder to increase pores in concrete structures and giving information for porous geopolymer production. It was introduced by adding 0.05-1% Al-powder as the initiated materials of geopolymers, to react with water in those materials and promote hydrogen gas inside specimens. The research, therefore, focused on the synthesis of porous geopolymer by metakaolin as a pozzolan and mixed with alkali solution (8M NaOH and Na2SiO3) as well as Al-powder as a foaming agent. The highly porous geopolymers were produced with various Al-powders as 0%, 0.2%, 0.4%, 0.6% 0.8% and 1% by weight. After 7, 14 and 28 days age, the specimens were tested the mechanical properties, such as compressive and flexural strengths. The water absorption, apparent porosity and bulk density were analyzed at 28 days age. The synthesis of metakaolin-based porous geopolymers with Al-powder presented good results. It showed that Al-powder content affected to degree of porosity of geopolymers. Keywords: Metakaolin based geopolymer, Porous geopolymer, Aluminium powder, Foaming agent, Mechanical and physical properties

Properties of Geopolymer Paste from Fly Ash Blended with Metakaolin as Pervious Concrete

The purpose of this research was to study pervious geopolymer concrete with different amounts of lignite fly ash (F), metakaolin (M), sodium silicate (NS) and 8 mol/L sodium hydroxide (NH) solution. Constant NS/NH ratio of 0.5, three alkali liquid/pozzolan (L/P) ratios viz., 0.5, 0.6 and 0.7 and pozzolan to coarse aggregate ratio of 1:8 were used. The compressive strengths of 50×50×50 mm3 cube specimens were tested at the age of 28 days. In addition, compressive strengths of 100 mm in diameter and 200 mm in height cylindrical specimens were tested at the age of 7, 14, 21 and 28 days. The chemical compositions and microstructures of specimens were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM), respectively.The mixture with 50%F+50%M and L/P ratio of 0.7 was the best proportion for pervious geopolymer concrete according to the compressive strength, good permeability and microstructural images. The bond of Si-O-Al and Si-O-Si characterized by Fourier Transform Infrared Spectroscopy (FTIR) spectra confirmed the developed geopolymeric structure.

Development of Thai Lignite Fly Ash and Metakaolin for Pervious Geopolymer Concrete

The study was to use Thai lignite fly ash and metakaolin to produce geopolymer paste as binder material in pervious concrete. The proper ratio of fly ash to metakaolin were varied as 100:0, 70:30, and 50:50. Alkali solution to pozzolan (L/P) ratios viz., 0.5, 0.6 and 0.8 by weight were prepared. The mechanical and characterization of pervious geopolymer concrete (PGC) were carried out. The results presented that the particle of fly ash was sphere with smooth surface, while metakaolin was partly agglomerated and irregular shaped. The increase of fly ash in the ratio of fly ash to metakaolin affected the lower requirement of volume of alkali solution. The compressive strength and of pervious geopolymer concrete at 28 days were 3.74-5.41. The void ratio and water permeability were 28.54-30.74% and 1.90-2.09 cm/sec, respectively. Therefore, geopolymer paste from fly ash and metakaolin could be used for pervious concrete with satisfied properties. However, the price of pervious cement concrete is 1,898-2,168 THB/m3, while the price of pervious geopolymer concrete is 2,123-4,173 THB/m3 due to the energy cost to transform kaolin into metakaolin by an electric furnace. The cost can be reduced by increasing the ratio of fly ash to metakaolin.

Development of Geopolymer Mortar from Metakaolin Blended with Agricultural and Industrial Wastes

Geopolymer is a greener alternative cement produced from the reaction of pozzolans and strong alkali solutions. Generally, the cement industry is one of largest producers of CO2 that caused global warming. For geopolymer mortar usage, Portland cement is not utilized at all. In this research, geopolymer mortars were prepared by mixing metakaolin, various wastes (fly ash, bagasse ash and rice husk ash) varied as 80:20, 50:50 and 20:80, 15M NaOH, Na2SiO3 and sand. The influence of various parameters such as metakaolin to ashes ratios and pozzolans to alkali ratios on engineering properties of metakaolin blended wastes geopolymer mortar were studied. Compressive strength tests were carried out on 25 x 25 x 25 mm3 cube geopolymer mortar specimens at 7, 14, 21, 28 and 91 air curing days. Physical and chemical properties were also investigated at the same times. The test results revealed that the highest compressive strength was 20% metakaolin - 80% fly ash geopolymer mortar. When the curing times increases, the compressive strength of geopolymer mortar also increases. The mixing of metakaolin and bagasse ash/rice husk ash presented lower compressive strength but higher water absorption and porosity. For FTIR results, Si-O, Al-O and Si-O-Na+ were found. Moreover, the geopolymer mortar could easily plastered on the wall.

In vitro surface reaction in SBF of a non-crystalline aluminosilicate (geopolymer) material

Geopolymer is a non-crystalline material based on aluminosilicate reaction exhibiting ceramic-like properties. It showed the possibility to use geopolymer as biomaterials by soaking in SBF solution to induct carbonate apatite onto the surface of samples. Carbonate apatite possesses good biocompatibility and bioactivity. The aims of this research were to study the geopolymer synthesis as a biomaterial to replace bones and the effects of Ca/P ratio on bioactivity properties of metakaolin-based geopolymers. For in vitro bioactivity test, the samples were soaked in SBF to study the influence of Ca(OH)2 contents on the surface reaction. The 14, 28, and 90xa0day-soaked sample surfaces were investigated using SEM, XRD, and FTIR characterization. The compressive strength of samples was also tested. The SEM micrographs revealed that the increase of Ca/P ratio resulted in the increase of the carbonate apatite on sample surfaces. FTIR results confirmed that the formation of Ca10(PO4)3(CO3)3(OH)2 was investigated.

Effect of Porosity and Pore Size on Microstructures and Mechanical Properties of Metakaolin Blended with Ca(OH)2 and PLA as Porous Geopolymers

Geopolymer is generally made of pozzolanic materials and alkali activators such as sodium alkali or potassium alkali. It can be solidified at ambient temperature to be developed as construction materials. Polylactic acid (PLA) was chosen to create pores in order for porous geopolymers. In this research, the porous geopolymer was developed either to reduce the weight of materials or to be utilized as thermal insulation materials. It was performed by metakaolin (MK), calcium hydroxide (Ca(OH)2), 10 molar potassium hydroxide (10M KOH) and potassium silicate (K2SiO3) for geopolymer pastes. These geopolymer pastes were mixed with 40 wt%, 50 wt% and 60 wt% of PLA and fired at 550°C for 6 h., therefore, pores inside geopolymer structure were found. Consequently, those geopolymers were characterized the mechanical properties e.g. compressive and flexural strength by Universal Testing Machine (UTM), microstructures by Scanning Electron Microscope (SEM), chemical compositions as functional groups by Fourier Infrared Spectroscope (FTIR). Furthermore, the pore size, bulk density, apparent porosity and thermal conductivity coefficient of geopolymers were analyzed. The results presented that the quantity of PLA affected the compressive strength and porosity of geopolymers. In conclusion, our porous geopolymer with 40 wt% PLA gave the highest strength.