XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
184
T1: P–51
Spectroscopic studies of fly ash-based geopolymers
Piotr Rożek
1
, Magdalena Król
1
, and Włodzimierz Mozgawa
1
1
Department of Silicate Chemistry and Macromolecular Compounds, Faculty of Materials Science
and Ceramics, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków,
Poland, e-mail: prozek@agh.edu.pl
Geopolymers are inorganic, amorphous to semi-crystalline materials with three-dimensional
network, which consist of Si–O–Al chains, i.e. silicon-oxygen and aluminum-oxygen
tetrahedrons connected by oxygen bridges [1]. Geopolymers are obtained from fly ash,
metakaolin or other aluminosilicate sources, which are activated by alkalis, e.g. sodium
hydroxide or sodium silicate solution; presence of Na
+
ions provides electrical charge balance of
the geopolymer framework [2]. Main product of geopolymerization is amorphous
aluminosilicate gel (N-A-S-H). Crystalline phases, such as hydroxysodalite, calcite, and zeolites
were also identified in geopolymeric matrices [2]. Geopolymers exhibit thermal, acidic and
alkaline resistance as well as relatively high compressive strength [3]. The aim of this work is to
examine the influence of different alkali and water contents on (micro)structure and mechanical
properties of fly ash-based geopolymers.
Coal fly ash was a starting material. Its chemical composition was determined by X-ray
fluorescence (XRF) method. Alkali-activation was conducted with sodium hydroxide (NaOH) at
the SiO
2
/Na
2
O molar ratio of 3, 4, and 5. Water content was at the ratio of 30, 40, and 50 wt.%
in respect to the weight of fly ash. These ingredients were mixed together and then filled into the
cubic molds, sealed with polyethylene film and cured in 80°C in a laboratory oven for 24 hours.
Subsequently the geopolymeric samples were kept in plastic bags for 27 days. After this time
structural and microstructural characterization (FTIR spectroscopy; X-ray diffraction, XRD;
scanning electron microscopy, SEM) of the specimens as well as compressive strength tests and
apparent density measurements were carried out.
XRD patterns of the geopolymers allowed to identify three crystalline phases:
hydroxysodalite, quartz and mullite, but only the first is a product of geopolymerization, while
quartz and mullite derive from unreacted remnants of fly ash. Broad peak in the region 20-30°
indicates presence of amorphous phase. The major band in the mid-infrared spectra (at about
1000 cm
–1
) is related to Si–O–Si(Al) vibrations. Several component bands in this region can be
noticed after the decomposition process. Vibrations of O–H bonds correspond to bands at 3440
and 1660 cm
–1
(stretching and bending, respectively) and vibrations of C–O bonds to bands at
1450 cm
–1
. The former may be related to water bound in amorphous aluminosilicate gel, while
the latter may be the result of carbonation – reaction of atmospheric CO
2
with
geopolymerization products and unreacted sodium hydroxide. Higher NaOH content favors
carbonation, inasmuch as the intensity of C–O vibrations bands then increases. Apparent density
decreases with an increase of both the SiO
2
/Na
2
O molar ratio and water content. Similar
situation is observed for compressive strength.
Keywords: geopolymer; fly ash; alkali-activation; FTIR spectroscopy
Acknowledgment
This work was financially supported by the National Science Centre in Poland under grant no.
2015/17/B/ST8/01200.
References
[1] J. Davidovits, J. Therm. Anal. 37(8) (1991) 1633.
[2] D. Khale, R. Chaudhary, J. Mater. Sci. 42(3) (2007) 729.
[3] M. Jin, Z. Zheng, Y. Sun, L. Chen, Z. Jin, J. Non-Cryst. Solid. 450 (2016) 116.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
185
T1: P–52
Application of infrared spectroscopy (FTIR)
in studies on asbestos-cement materials
Józef Iwaszko
1
, Anna Zawada
2
, and Małgorzata Lubas
3
1
Institute of Materials Engineering, Czestochowa University of Technology, 19 Armii Krajowej St.,
42-200 Czestochowa, Poland, e-mail: iwaszko@wip.pcz.pl
2
Institute of Materials Engineering, Czestochowa University of Technology, 19 Armii Krajowej St.,
42-200 Czestochowa, Poland, e-mail: zawada@wip.pcz.pl
3
Institute of Materials Engineering, Czestochowa University of Technology, 19 Armii Krajowej St.,
42-200 Czestochowa, Poland, e-mail: mlubas@wip.pcz.pl
Asbestos-Containing Waste (ACW) in the form of a fragment from an asbestos-cement sheet
was subjected to high-energy milling in a planetary mill at a constant rotational speed of 650
rpm and variable milling times: 1, 2, and 3 hours. The initial and the milled material were
subjected to infrared spectroscopic examination to identify the asbestos variety and to evaluate
changes in individual IR spectra caused by the high-energy milling. FTIR examinations
followed the optical microscopy and scanning electron microscopy studies as well as the X-ray
analysis of the phase composition. It was found that the asbestos fibres present in the asbestos-
cement sheet were respirable fibres with pathogenic properties. Identification of asbestos using
the spectroscopic method showed that chrysotile asbestos was present in the as-received ACW;
while no characteristics of absorption bands from crocidolite or amosite were found. The results
of spectroscopic examinations were confirmed by the X-ray phase analysis. During SEM
investigations of the milled ACW, the complete loss of the fibrous structure of chrysotile was
observed. The FTIR examinations of the milled material showed that with the increasing milling
time the characteristic absorption spectra from chrysotile diminished and already after 2 hours of
milling their almost complete decay was observed. Thereby it was confirmed that high-energy
milling results in the destruction of the crystalline structure of the asbestos phase. The studies
carried out have shown that the treatment of asbestos-cement materials using high-energy
milling is an effective method for the asbestos disposal, capable of competing with other
technologies and solutions. Moreover, the FTIR spectroscopy was found to be useful to identify
asbestos phases and to assess changes caused by high-energy milling.
Keywords: asbestos-containing waste; high-energy milling; FTIR
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