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

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

Materials Science-Poland

Volume 39 (2021): Issue 4 (December 2021)

By: Chi-Che Hung, Wei-Ting Lin, Wei-Chung Yeih and Jiang-Jhy Chang

Open Access

|Apr 2022

Figures & Tables

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

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

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

Relationship between SiO2/Na2O and pH value of activator

Relationship between SiO2+Na2O and the pH value of activator

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

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

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

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

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 K_b	(CaO+MgO)/(SiO₂+Al₂O₃)	0.93

Physical properties	Specific weight	2.90
Physical properties	Ignition loss (%)	0.28

DOI: https://doi.org/10.2478/msp-2021-0045 | Journal eISSN: 2083-134X | Journal ISSN: 2083-1331

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Language: English

Page range: 570 - 579

Submitted on: Jan 7, 2022

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Accepted on: Mar 6, 2022

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Published on: Apr 26, 2022

Published by: Wroclaw University of Science and Technology

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

alkali-activated materials,

silicate-based activator,

microstructures

Related subjects:

Materials sciences,

Materials sciences, other,

Functional and smart materials,

Materials characterization and properties

© 2022 Chi-Che Hung, Wei-Ting Lin, Wei-Chung Yeih, Jiang-Jhy Chang, published by Wroclaw University of Science and Technology
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

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