http://www.flyash.info/2013/064-Tandon-2013.pdf

1. Influence of Coal Fly Ash on
Mechanical Properties of Mortar
Consisting of Total Dissolve Solids
By
Bijoy Krishna Halder, Vivek Tandon, Anthony Tarquin,
Ramana V. Chintalapalle
The University of Texas at El Paso

2. Agenda
 Introduction
 Challenges
 Objective
 Material Used
 Micro Scale Test
 Experimental Design
 Compressive Strength Test
 Conclusion

3. Introduction

4. Introduction
• Water is an important resource.
• Mark et al. (2002) (Global Water Outlook 2025 Averting an
Impending Crisis)
Year
Global Water
Demand (billion
gallon/day)
Increase
1995 3000
25 %
2025 3750

5. Introduction (Cont.)
• Dependency on Nontraditional source
• Technique like Desalination is used to produce 50-90%
potable water.
• Remaining is byproduct brine
• Problem is sustainable disposal of this brine (containing TDS*)
• Is it possible to use TDS as construction material?
* TDS=Total Dissolved Solids

6. Challenges

7. Challenges
 TDS contains high corrosive elements (Na, Cl) which needs
stabilization.
 Barberon et al. (2005)* found that
*Barberon, F., Baroghel-Bouny, V., Zanni, H, Brsson, B., Caillerie, J., Malosse, L., Gan, Z., Interactions between chloride and cement paste materials, Magnetic Resonance
Imaging, V. 23, 2005, pp. 267-282.

8. Objective

9. • Evaluate the feasibility of using TDS in mortar by stabilizing
salt using fly ash.
Objective

10. Material Used

11. Material Used
• Cement (Type I/II OPC, ASTM C-150)
• Quickrete all purpose sand (ASTM C 33 )
• Water & Sodium phosphate buffer (50mM Na3PO4, 8.2g/l of
water)
• TDS (passing #16 sieve )
• Class F fly Ash

12. • Analytical report of final concentration of brine
• All concentration in mg/l, conductivity (µs/cm) and pH in (pH unit)
Material Used (Cont.)
1
Parameter Final concentration
Calcium 1432
Iron 5.5
Magnesium 438
Potassium 216
Sodium 8,640
Chloride 26,600
Sulfate 8,140
Silica 72
Electrical Conductivity 99,000
TDS 57,800
pH 3.6
Source: Tarquin, A. J. (2010). “High Tech Methods to Reduce Concentrate Volume Prior to Disposal”, El Paso Water Utilities Public Service Board, El Paso, p. 23.

13. • Fly ash Property (Collected from Boral Material Technology)
Material Used (Cont.)
Component Results
SiO2 50.69 %
Al2O3 23.68 %
Fe2O3 4.68 %
SiO2+ Al2O3+ Fe2O3 79.05 %
CaO 13.19 %
MgO 1.62 %
SO3 1.78 %
Na2O 0.05 %
K2O 0.90 %
Total Alkalies (as Na2O) 0.64 %
Loss of Ignition, % LOI 1.69 %
Specific gravity 2.29
1

14. MICRO SCALE TEST

15. XRD Analysis of TDS
• Bruker D8 X-ray diffractometer
• Rock salt, Halite

16. Laser Diffraction Particle Sizing
0
2
4
6
8
10
12
14
0.1 1 10 100 1000
VolumeIn(%)
Particle Size (µm)
Mean diameter
=34.065 µm

17. 0
10
20
30
40
50
60
70
80
90
100
0.1 1 10 100 1000
CumulativeVolumeIn(%)
Particle Size (µm)
Median Dia =24.062 µm
Laser Diffraction Particle Sizing (Cont.)

18. • The key findings of laser diffraction analysis are
Parameter Outcome
D (0.1) 3.825 µm
D(0.5) 24.062 µm
D(0.9) 80.24 µm
Surface weighted mean D[3,2] 7.359 µm
Volume weighted mean D [4,3] 34.065 µm
Specific surface area 815 m2
/kg
Particle size larger than 45 µm in
volume
25 %
Particle size larger than 10 µm in
volume
70 %
1
Laser Diffraction Particle Sizing (Cont.)

19. XRD Analysis of Fly Ash
• Predominant crystalline phases Q & M (Al4.44Si1.56O9.78).

20. SEM Analysis of Fly Ash
1
(a) (b)
(c) (d)Irregular
Shape

21. • Fig a, b & c showed irregular and larger particle > 45 μm.
• Yield due to collision of the flame-borne particles of silica ash
and sulfate fume in pulverized-coal-fired boilers.
• Does not have smooth texture.
• Significant amount of small solid sphere particles (Figure 5 d).
SEM Analysis of Fly Ash (Cont.)

22. • EDS analysis of a single solid sphere particle at 20 kV and
10000 magnification
• Si/Al=1.5 is low, may cause formation of lower strong bonds
of Al-O-Al or Si-O-Al than strong bonds Si-O-Si.
• MgO induce formation of mullite.
SEM Analysis of Fly Ash (Cont.)
Element Si Al Fe K Ca Na Mg S O
Weight (%) at
10,000
magnification
26 17 2.8 0.6 4.9 2.4 1.2 0.3 45

23. Experimental Design

24. Sample Preparation (Cont.)
 ASTM* C-109 (2008)
 Cement: Sand: Mixing Liquid= 1:2.75:0.49
 Samples were prepared in 2 × 2 × 2 in..
*American Society of Testing material

25. Specimen
Size
Mortar
Components
Material Amount
Cement
(C),
grams
Fly
Ash(F),
grams
Sand (S),
grams
Salt
(s),
grams
Phosphate
Buffer (P),
ml
Amount
of
Materials
required
for Six-50
mm. Cube
Specimens
CSP 500 --- 1,375.0 --- 242.5
CSF(5%)P 475 25 1,375.0 --- 242.5
CSF(10%)P 450 50 1,375.0 --- 242.5
CSF(20%)P 400 100 1,375.0 --- 242.5
CSF(30%)P 350 150 1,375.0 --- 242.5
CSF(40%)P 300 200 1,375.0 --- 242.5
CSs(5%)P 475 25 1306.3 68.7 242.5
CSs(5%)F(5%)P 475 25 1306.3 68.7 242.5
1
Sample Preparation (Cont.)
*C: Cement; S:Sand; s: TDS/salt; F:Fly Ash; P:Sodium Phosphate Buffer; W: Water

26. Curing Process
• Tap Water (For standard samples)
• Cured at 25 ̊ C, submerging under water.

27. Compressive Strength
Test (ASTM C 109-08)

28. Compressive Strength Test
*C: Cement; S:Sand; s: TDS; F:Fly Ash; P:Sodium Phosphate Buffer; W: Water

29. • Fly ash sample strength reduction
• From micro scale test
1. Particle size larger that 45 µm = 25% in vol. (Cheerarot suggested only 5%)
2. Mean particle size = 34 µm (Li (2005)* found that fly ash coarser than 12 µm
lower strength ratio of 28 day compressive strength in mortar comparing no fly
ash added sample)
3. Formation of non glassy phase mullite that chemically inactive.
4. EDS analysis showed low Si/Al ratio, may form more C-A-S-H gel (Walairat
(2009)** mentioned C-A-S-H is weak binder)
5. Larger particle present in fly ash will remain inert.
Compressive Strength Test
*Li, Gengying & Wu, Xiaozhong," Influence of fly ash and its mean particle size on certain engineering properties of cement composite mortar.", Cement & Concrete Research, Vol 35, p. 1128-
1134, 2005.
**Walairat, B., Richard, L. “A figure of merit for fly ash replacement of Portland cement.” World of Coal Ash Conference, May 4-7, 2009.

30. • For TDS (s) added Sample CSs(5%)P
 Addition of salt considerably decreased the strength for CSs(5%)P sample.
For >5 % replacement with TDS, sample failed by crumbing under
loading.
 Berke* reported that chloride ions presence in solution may weaken the
integrity of cement matrix.
 Barberon found free Cl- ion form Friedel’s salt; thus, Al substituted in C-
S-H gel does not contribute towards strength gain.
• CSs(5%)F(5%)P improved the ultimate strength (30.6 MPa)
by 6 MPa.
• Gained strength at higher rate from 7-28 days by 23 percent.
*Berke, N.S., Pfeifer, D.W., and Weil, T.G., Protection against Chloride Induced Corrosion; Concrete International, V.10, No.12, 1988,
pp. 45-55.
Compressive Strength Test

31. Strength Growth Rate (%)
*C: Cement; S:Sand; F:Fly Ash; s:TDS; P:Sodium Phosphate Buffer; W: Water
Only 30 & 40 % fly ash replacement showed higher pozzolanic reaction rate,
though some fly ash will remain inert due to lack of hydration product Ca(OH)2

32. Conclusion

33. Conclusion
• Fly ash with mean particle size larger than 10 µm, inactive
mullite and lower calcium oxide and Si/Al ratio content will
cause slower pozzolanic reaction to yield lesser strength
(ultimate compressive strength) of Mortar.
• Total dissolve solid (TDS) or salt can raise the pozzolanic
reaction rate, so use of brine partially with water can be an
option to produce cement mortar. However still it does require
lot of research to dispose it as construction material in
sustainable way.

34. • Ternary blends of this type of fly ash can be investigated to
use it effectively.
• Alternative approach for this type of fly ash with
biocementation may further improve strength and durability,
that is under investigation.
Future Recommendation