1. Presenter: M.W. Heyns
Mentor: Dr M. Mostafa

2. 
 Fly Ash?
 Fly Ash is recognized as a suitable pozzolanic material
and can be used in construction materials on a large
scale. Fly Ash utilization has significant environmental
benefits:
 Fly Ash concrete requires less energy and water to
produce and has lower greenhouse gas emissions
 Reduction in coal combustion products such as landfill
sites
 Conservation of other natural materials and resources
Introduction

3. 
 But,
 A question still remains:
 How environmental friendly is Fly Ash
 To understand this, we need to analyse Fly Ash
chemically and compare it to a substance which is in
human terms, “A life source”. This means that if this
source is threatened, human existence is threatened.
Introduction

4. 
 We also need to analyse the product for the purpose
it is going to be used and then also analyse the
environment effects.
 Two steps we have to look at:
 The environment effects of the product in it’s natural
state
 The environment effect of the product after the
intended use.
Introduction

5. 
 The life source in this study is:
Introduction

6. 
 G5 – Crushed Granite
 Cement:
 LAFARGE CEM II 32,5 VA(S-V)
 AFRISAM CEM II 32,5 B-M(S-V)
 Fly Ash:
 Durapozz
 Pozzfill
 Dump Ash
Materials

7. 
 After subjecting the materials with various combinations
to specified tests, the following mixtures were identified
for this study:
 1% LAFARGE mixed with 16% Dump Ash
 1% LAFARGE mixed with 16% POZZFILL
 1% LAFARGE mixed with 16% DURAPOZZ
 1% AFRISAM mixed with 18% Dump Ash
 1% AFRISAM mixed with 18% POZZFILL
 1% AFRISAM mixed with 18% DURAPOZZ
 G5 + 1% AFRISAM
 G5 + 1% LAFARGE
Materials

8. 
 The combinations were further subjected to leach
testing to identify harmful elements that could have
serious detrimental effect on the life source.
 Key potential hydrological impact is the collection of
contaminants by water as it percolates through or
over a material. Leachant tests are conducted to
analyze the solubility of Fly Ash
Materials

9. 
 Stabilization with Fly Ash and cement is not only to
gain strength and meet required specifications but it
can also be used to “entomb” the harmful elements
that can enter and contaminate the ground water
system.
 Once these elements are shown to be less than the
maximum allowed elements found in drinking
water, then it can thus be concluded that the use of
Fly Ash in road stabilization can be used and that the
risk of harmful elements being released to the
environment will be negligible.
Materials

10. 
Results
Material
As
Ba
Cr
Pb
Se
Cu
Zn
Maximum Acceptable
Level (parts per billion)
Possible Effects of Higher Levels
50 Lung Cancer, kidbey damage
1000 Heart damage
50 Liver, kidney damage
50 Brain damage
10 Growth inhibition
49
Metallic taste, blue-green stains on
fixtures
N/A Metallic taste

11. Parameter Range (ppb)
As 20
Ba 1502
Bi 3.8
Br <2
Ce 235
Co 16
Cs 7.8
Cu 49
Cr 190
Pb 54
Se 2.8
Zn 49
Zr 476
Results

12. 
 Fly Ash in it’s natural state
Results
Material
Fly Ash
Results
(ppb)
Maximum Acceptable
Level (parts per
billion)
Possible Effects of Higher
Levels
As 20 50 Lung Cancer, kidbey damage
Ba 1502 1000 Heart damage
Cr 190 50 Liver, kidney damage
Pb 54 50 Brain damage
Se 2.8 10 Growth inhibition
Cu 49 49
Metallic taste, blue-green
stains on fixtures
Zn 49 N/A Metallic taste

13. 
Results
As Ba Bi Co Cr Cu Pb Se Zn
20 1502 3.8 16 190 49 54 2.8 49
1%LAFARGE+ 16%DURAPOZZ 15.30 < 4 1.76 < 0.2 46.35 14.24 < 6 < 0.4 < 60
1%LAFARGE+16 POZZFILL 13.65 < 4 1.72 < 0.2 58.11 14.88 < 6 1.56 < 60
1%LAFARGE+ 16%DUMP ASH 7.59 < 4 1.70 < 0.2 23.97 16.39 < 6 < 0.4 < 60
1%AFRISAM + 18%DURAPOZZ 19.41 < 4 1.68 < 0.2 50.29 14.20 < 6 2.33 < 60
1%AFRISAM + 18%POZZFILL 15.04 < 4 1.76 < 0.2 59.14 17.14 < 6 < 0.4 < 60
1%AFRISAM +18%DUMP ASH 8.19 < 4 1.67 < 0.2 8.89 17.11 < 6 < 0.4 < 60
5.32 < 4 1.70 0.44 8.18 15.91 < 6 < 0.4 < 60
5.36 < 4 1.70 0.29 8.56 18.89 < 6 < 0.4 < 60
TypicalClass F FlyAsh(ppb)
Leachate (ppm)
Description
1% AFRISAM
1% LAFARGE

14. 
Results
Cr Cu Zn As Se Ba Pb
ppm ppm ppm ppm ppm ppm ppm
8.18 15.91 <60 5.32 <0.4 <4 <6
8.56 18.89 <60 5.36 <0.4 <4 <6
46.35 14.24 <60 15.30 <0.4 <4 <6
58.11 14.88 <60 13.65 1.56 <4 <6
23.97 16.39 <60 7.59 <0.4 <4 <6
50.29 14.20 <60 19.41 2.33 <4 <6
59.14 17.14 <60 15.04 <0.4 <4 <6
8.89 17.11 <60 8.19 <0.4 <4 <6
Leachate (parts per million)
1% OPCAFRISAM
1% OPCLAFARGE
1% OPC+16% D.POZZ LAFARGE
1% OPC+16POZZFILLLAFARGE
1% OPC+16% D.ASHLAFARGE
1% OPC+18% DURAPOZZ AFRISAM
1% OPC+18% POZZ FILLAFRISAM
1% OPC+18% D.ASHAFRISAM
Description

15. 
 The Fly Ash stabilized, show a tremendous
reduction in leach elements which is mainly due to
the reaction-taking place between cement, Fly Ash
and soil.
 Laboratory leaching sample results have indicated
that Fly Ash constituents exhibit limited mobility.
 The study revealed that Fly Ash is an environmental
option and has engineering advantages when used
properly for soil stabilization techniques.
Conclusion

16. 
 Elements in Fly Ash vary from different classes. As
shown, common Class F Fly Ash in South Africa
have some potential hazardous material compared
with water’s maximum inorganic allowable when
not stabilized as indicated in the study.
 A full comparison must be conducted at the design
stage of an intended project, to compare what
hazardous materials are leached and at what toxic
level it represents.
Conclusion

17. 
 The Leach results have shown that the material was
“entombed” and the possibility of leachant releasing
agents of a dangerous nature are to a minimal.
 The results have shown a tremendous reduction in leach
agents and have shown that it is even safe if the minor
leach agents do enter the drinking water tables.
 The leach tests in this study have shown that the Fly Ash
stabilization is environmental friendly.
 It also shows that the Fly Ash particles that are normally
released are bound within the soil due to chemical
reactions and continue to be bound as long as reactions
take place.
Conclusion

18. Q & A