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Frontiers of Chemical Science and Engineering

Front. Chem. Sci. Eng.    2017, Vol. 11 Issue (3) : 317-327     DOI: 10.1007/s11705-017-1622-6
The influence of curing conditions on the mechanical properties and leaching of inorganic polymers made of fayalitic slag
Remus I. Iacobescu1, Valérie Cappuyns2,3, Tinne Geens4, Lubica Kriskova1, Silviana Onisei1, Peter T. Jones1, Yiannis Pontikes1()
1. KU Leuven, Department of Materials Engineering, 3001 Leuven, Belgium
2. KU Leuven, Department of Earth and Environmental Sciences, 3001 Leuven, Belgium
3. KU Leuven, Faculty of Economics and Business, 1000 Brussels, Belgium
4. KU Leuven, Department of Healthcare and Technology, 3001 Leuven, Belgium
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This study reports on the impact of the curing conditions on the mechanical properties and leaching of inorganic polymer (IP) mortars made from a water quenched fayalitic slag. Three similar IP mortars were produced by mixing together slag, aggregate and activating solution, and cured in three different environments for 28 d: a) at 20 °C and relative humidity (RH) ~ 50% (T20RH50), b) at 20 °C and RH≥90% (T20RH90) and c) at 60 °C and RH ~ 20% (T60RH20). Compressive strength (EN 196-1) varied between 19 MPa (T20RH50) and 31 MPa (T20RH90). This was found to be attributed to the cracks formed upon curing. Geochemical modelling and two leaching tests were performed, the EA NEN 7375 tank test, and the BS EN 12457-1 single batch test. Results show that Cu, Ni, Pb, Zn and As leaching occurred even at high pH, which varied between 10 and 11 in the tank test’s leachates and between 12 and 12.5 in the single batch’s leachates. Leaching values obtained were below the requirements for non-shaped materials of Flemish legislation for As, Cu and Ni in the single batch test.

Keywords inorganic polymer      geochemical leaching modelling      heavy metals      recycling      non-ferrous fayalitic slag      curing     
Corresponding Authors: Yiannis Pontikes   
Online First Date: 17 March 2017    Issue Date: 23 August 2017
 Cite this article:   
Remus I. Iacobescu,Valérie Cappuyns,Tinne Geens, et al. The influence of curing conditions on the mechanical properties and leaching of inorganic polymers made of fayalitic slag[J]. Front. Chem. Sci. Eng., 2017, 11(3): 317-327.
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Remus I. Iacobescu
Valérie Cappuyns
Tinne Geens
Lubica Kriskova
Silviana Onisei
Peter T. Jones
Yiannis Pontikes
Oxides XRF/
Elements XRF/
ICP-OES/ (mg?kg ?1) VLAREMA[ 32] Minerals QXRD /wt-%
FeO 57.4 Cr 4789 8.4 1250 Fayalite 24.1
SiO 2 26.4 Pb 5570 5.5 1250 Magnetite 1.6
ZnO 6.2 Zn 49753 250 1250 Quartz 1.0
Al 2O3 3.4 Cu 3994 375 Amorphous 73.3
CaO 2.3 As 8.4 250
Cr 2O3 0.7 Cd 5.5 10
PbO 0.6 Ni 250 250
MgO 0.7
CuO 0.5
MnO 0.5
Other 1.3
Tab.1  Total oxides and elements composition (determined with XRF (in wt-%), ICP-OES (in mg/kg) and QXRD (in wt-%)) of the fayalitic slag and the thresholds of critical metals content in the starting material, allowed by VLAREMA
Fig.1  Reactivity test of the fayalitic slag in 10 mol/L NaOH showing the dissolution rate of Al, Si, Pb and Zn over time
Fig.2  BEI of a fayalitic slag particle after the reactivity test revealing the remaining crystalline part (mainly fayalite mineral) after dissolving the amorphous part around it. (a) the whole particle (100 µm scale); (b) magnification of a selected area (20 µm scale)
Fig.3  XRD patterns of the reference slag and IPs produced in different curing environments. Peaks identification has not been used due to the major presence of only fayalite mineral
Fig.4  FTIR spectra of the reference slag and IPs produced in different curing environments
Fig.5  BEI of samples T20RH50, T20RH90 and T60RH20. FP: unreacted fayalitic particles; IPB: IP binder; S: sand used as aggregate; R: resin (scale bar 10 µm)
Samples Oxides As and heavy metals (as oxides)
FeO SiO 2 Al 2O3 CaO Na 2O As 2O5 Cr 2O3 NiO PbO ZnO CdO CuO
T20RH50 36.22±7.0 43.77±6.3 3.57±0.6 6.47±0.7 0.66±0.3 0.12±0.03 0.06±0.04 0.01±0.01 0.54±0.16 4.69±1.16 0.01±0.01 0.42±0.18
T20RH90 45.09±8.9 37.07±9.7 3.00±1.2 4.55±1.1 3.19±1.6 0.10±0.06 0.09±0.02 0.04±0.01 0.42±0.23 3.87±0.95 0.01±0.01 0.34±0.18
T60RH20 36.17±5.0 43.75±8.0 4.64±1.8 3.94±1.5 1.45±0.5 0.06±0.02 0.08±0.04 0.03±0.01 0.55±0.16 4.02±0.43 0.01±0.01 0.52±0.19
Tab.2  WDS microanalysis of the major oxides, As and heavy metals (as oxides) in the IP matrix (in wt-%, standard deviation from the mean value is also given, in wt-%)
Samples Compressive strength Flexural strength
Average St. dev. Average St. dev.
T20RH50 19.3 ±2.9 1.8 ±0.0
T20RH90 31.0 ±4.8 3.4 ±0.2
T60RH20 20.6 ±1.7 2.1 ±0.0
Tab.3  Mechanical properties after 28 days of curing (in MPa)
Elements T20RH50 T20RH90 T60RH20
As 165 179 167
Cd bdl a) bdl bdl
Cr 13 5 6
Cu 130 146 174
Pb 69 69 68
Ni 5 10 6
Zn 0 22 39
Ca 351 182 127
Fe 602 362 136
Mg 6 17 2
Tab.4  Cumulative amount of As, Cd, Cr, Cu, Ni, Pb and Zn (in mg•m–2) released in the tank leaching test
Fig.6  Cumulative release of heavy metals, As, Ca, Fe and Mn as a function of time during the tank test
Elements T20RH50 T20RH90 T60RH20 Threshold /(mg•kg –1)
(CMA 2/II/A.9.1.)
As 0.20 0.40 0.20 0.80
Cd bdl a) bdl bdl 0.03
Cr 0.10 0.10 0.20 0.50
Cu 1.40 1.30 1.80 0.50
Pb 0.90 1.80 1.60 1.30
Ni 0.05 0.10 0.06 0.75
Zn 6.30 14.20 6.90 2.80
Ca 127.00 73.00 58.00
Fe 408.00 728.00 708.00
Mn 0.35 0.88 0.70
Tab.5  Amount of As, Cd, Cr, Cu, Ni, Pb and Zn (in mg•kg–1) released during the single batch leaching test
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