The term “geopolymer” was first used by J.Davidovits in the
late 1970s.
Geopolymers have three dimensional amorphous structure
and can be synthesized from by products such as fly ash,
blast furnance slag or geological materials such as metakaolin.
However, metakaolin is expensive and is not used widely in
the construction industry.
Xray fluorescence (XRF)
X-ray diffraction (XRD)
Scanning electron micrograph (SEM)
Fourier transform infrared spectroscopy (FTIR)
Differential scanning calorimetry (DSC)
Thermal gravimetric analysis (TGA)
The chemical composition of the alumino silicate was
determined using XRF shows the chemical
composition of fly ash.
The basic material of the geopolymer based fly ash is
of a prevailingly amorphous character only seldom
containing needle-shaped minority crystals. The X-
ray diffraction (XRD) pattern of fly ash in its as received condition is shown in Fig.
SEM image showing the characteristic morphology of the
original fly ash. The majority of the fly ash particles are
spherical in nature and are precipitator type fly ash.
This ash consists of a series of spherical particles of different
sizes (diameters ranging from 200 to 10 Am). Although
usually hollow, some of these spheres may contain other
particles of a smaller size in their interiors.
The FTIR spectra for both raw fly ash and geopolymer paste demonstrated remarkable differences. The vibration at 1020 cm-1
corresponding to SiO and AlO in the raw fly ash was shifted to less than 1000 cm-1.
DSC was used to measure a number of characteristic
properties of the geopolymer pastes.
Using this technique, it is possible to observe exothermic and
endothermic events as well as glass transition temperatures(Tg).
The range of investigation is between -30 and 100̊ C
Wide range of temperatures. Programmed heating/cooling rates Sensitivity Any material may be tested
Fiber Powder liquid etc;
Small amount of material is needed Does not take much timeClearness of results
Cannot really control the rate of experiment.
Dependent on too many parameters.
Very sensitive to any changes.
The result depends a lot from the operator.
The procedure of standard parameters.
Evaluation is not described.
In this TGA test, the mass loss was measured while the
specimens were gradually exposed to increasing temperatures.
Powdered specimens were used in TGA to ensure the
achievement of thermal equilibrium during transient heating.
Accurate
Low detection limit(up to 10-7 g)
Reliable data
Easy to use
Rather cheap
Disadvantages
Destructive
Limited range of samples
Time consuming
Usually not qualitative
Class C Fly Ash:
For class c fly ash-based
geopolymer paste, low W/F
could meet the demand for an
approving fluidity.
Class C fly ash-based
geoolymer pase and mortar
could both abtain high
compressive strength after
curing a 70 ͦC for 24h.
Compressive strengthof mortar
was much higher than paste
with same water to fly ash
ratio.
Class F fly ash:
Class F fly ash mixed
with calcium hydroxide
geopolymer mortar.
The compressive
strength and the flexural
strength of geopolymer
mortar after being
demolded cured at
standard temperature for
1 day were up to 6.48
MPa and 2.07 MPa.
Geopolymer are new materials which have various application
fields.
Geopolymer concrete showed reduction deterioration in its
properties when exposed to temperatures above 200 ͦC.
Geopolymers shows significant potential to be a material for
the future,because it is not only environmentally friendly but
also possesses excellent mechanical properties.
And it also has a great potential for applications in various
industries.