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Delayed setting time for alkali-activated slag composites using activator containing SiO2 and Na2O

Chi-Che Hung
Chi-Che Hung
, 
Wei-Ting Lin
Wei-Ting Lin
, 
Wei-Chung Yeih
Wei-Chung Yeih
 und 
Jiang-Jhy Chang
Jiang-Jhy Chang
   | 26. Apr. 2022
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Online veröffentlicht: 26. Apr. 2022
Seitenbereich: 570 - 579
Eingereicht: 07. Jan. 2022
Akzeptiert: 06. März 2022
DOI: https://doi.org/10.2478/msp-2021-0045
Schlüsselwörter
© 2021 Chi-Che Hung et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Fig. 1

pH value of activator as a function of SiO2 concentration under various Na2O concentrations
pH value of activator as a function of SiO2 concentration under various Na2O concentrations

Fig. 2

pH values of activators with fixed alkali modulus of SiO2/Na2O = 1
pH values of activators with fixed alkali modulus of SiO2/Na2O = 1

Fig. 3

pH values of activators with fixed total alkali content of SiO2+Na2O = 160 g/l or 200 g/l
pH values of activators with fixed total alkali content of SiO2+Na2O = 160 g/l or 200 g/l

Fig. 4

Relationship between SiO2/Na2O and pH value of activator
Relationship between SiO2/Na2O and pH value of activator

Fig. 5

Relationship between SiO2+Na2O and the pH value of activator
Relationship between SiO2+Na2O and the pH value of activator

Fig. 6

Setting time (Na2O = 60–120 g/l): (A) initial time; (B) final time
Setting time (Na2O = 60–120 g/l): (A) initial time; (B) final time

Fig. 7

Setting time under SiO2/Na2O = 1: (A) initial time; (B) final time
Setting time under SiO2/Na2O = 1: (A) initial time; (B) final time

Fig. 8

Setting times under SiO2+Na2O = 160 g/l or 200 g/l: (A) initial time; (B) final time
Setting times under SiO2+Na2O = 160 g/l or 200 g/l: (A) initial time; (B) final time

Fig. 9

Relationship between setting time and SiO2/Na2O: (A) initial time; (B) final time
Relationship between setting time and SiO2/Na2O: (A) initial time; (B) final time

Fig. 10

Relationship between setting time and SiO2+Na2O: (A) initial time; (B) final time
Relationship between setting time and SiO2+Na2O: (A) initial time; (B) final time

Fig. 11

SEM photos (1,000× magnification): (A) SiO2 = 120 g/l and Na2O = 120 g/l for 3 days; (B) SiO2 = 80 g/l and Na2O = 80 g/l for 3 days. SEM, scanning electron microscopy
SEM photos (1,000× magnification): (A) SiO2 = 120 g/l and Na2O = 120 g/l for 3 days; (B) SiO2 = 80 g/l and Na2O = 80 g/l for 3 days. SEM, scanning electron microscopy

Mix designs

Activator (g/l) Weight %
SiO2 Na2O NaOH Na2SiO3 H2O Slag
60 60 0.013 0.054 0.266 0.667
60 80 0.022 0.054 0.257 0.667
60 100 0.031 0.054 0.249 0.667
60 120 0.039 0.054 0.240 0.667
80 60 0.009 0.072 0.252 0.667
80 80 0.018 0.072 0.243 0.667
80 100 0.027 0.072 0.235 0.667
80 120 0.035 0.072 0.226 0.667
100 60 0.005 0.090 0.238 0.667
100 80 0.014 0.090 0.229 0.667
100 100 0.022 0.090 0.221 0.667
100 120 0.031 0.090 0.212 0.667
120 60 0.001 0.108 0.224 0.667
120 80 0.010 0.108 0.216 0.667
120 100 0.018 0.108 0.207 0.667
120 120 0.027 0.108 0.198 0.667

Grain size distribution of the slag

Sieve size No. 50 No. 100 No. 200 No. 325 Bottom
Cumulative retained percentage (%) 0.20 0.40 32.50 77.23 100.00

Chemical composition of sodium silicate used in the experiments

Items Results
Water-insolubles (%) 0.01 (max)
SiO2 (%) 37.0
Na2O (%) 17.7
Mole ratio 2.16
Fe (%) 0.02 (max)

Chemical composition of sodium hydroxide used in experiments

Chemical composition Content (wt. %, maximum)
Chloride (Cl) 0.005
Sulfate (SO4) 0.003
Silicate (SiO2) 0.01
Phosphate (PO4) 0.001
Heavy metal (As, Pb) 0.001
Iron (Fe) 0.0007
Aluminum (Al) 0.003
Calcium (Ca) 0.001
Magnesium (Mg) 0.0005
Potassium (K) 0.1
Total nitrogen (N) 0.001
Arsenic (As) 0.0002
Sodium carbonate (Na2CO3) 2.0
Assay (NaOH) 95.0

Chemical and physical properties of slag

Main chemical composition of slag (by weight %) SiO2 33.87
Al2O3 14.42
Fe2O3 0.69
CaO 39.54
MgO 5.35
SO3 2.47
Basicity coefficient Kb (CaO+MgO)/(SiO2+Al2O3) 0.93
Physical properties Specific weight 2.90
Ignition loss (%) 0.28
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