This document presents the outline of a research project on the use of fly ash in the construction industry in Sri Lanka. It begins with an introduction describing fly ash as a byproduct of coal power generation and its current uses. It then outlines the objectives and methodology of the research project, which include understanding the properties of fly ash concrete and identifying suitable applications through literature reviews and field surveys. The document reviews the properties, production, and chemical composition of fly ash, as well as its reactions in cement. It describes several current and potential applications of fly ash in Sri Lanka, including in concrete, bricks, blocks, and road construction. It provides details on some local efforts and mix designs used. The document also notes some failures experienced with high

2. Presented by
K.Yasothan
Institution of Engineers Sri Lanka
Part III (C) – Research Project

3. PRESENTATION OUTLINE
 INTRODUCTION
 LITERATURE REVIEW
 FIELD SURVEYS DATA AND LOCAL EFFORTS
 ANALYSIS OF RESULT AND RECORDS
 CONCLUSIONS AND RECOMMENDATION FOR
FUTURE WORK

4. INTRODUCTION
In coal power generation, fly ash is produced as a by-product. In power plant the
dust-collection system removes the fly ash, as a fine particulate residue. Fly ash
particles are typically spherical, ranging in diameter from <1 µm up to 150 µm. Over
the past decade, the use of fly ash in construction industry has been successfully
archived. In Sri Lanka, major proportion of the power demand was met using
hydropower in the twentieth century. There is one coal power plant in operation
now at Nuraichcholai and plans are there to have another one at Sampoor,
Trincomalee in the near future. As this is a new approach for power generation in Sri
Lanka, there are considerable efforts to dump the generated fly ash in construction
projects. To dispose this waste material in a sustainable way, research is needed to
identify possible usage in the construction industry of our country. The use of fly ash
in concrete improves its workability, reduces segregation, bleeding, heat evolution
and permeability, inhibits alkali-aggregate reaction, and enhances sulphate
resistance. Presently a few companies are involved in using fly ash in their batching
plants to manufacture concrete in Sri Lanka. Also there are several other firms,
which have tried to use fly ash for applications and failed. For example use of fly ash
in manufacturing hume pipes, paving blocks etc have failed due to delay in strength
gaining.

5. Aim
In the present study, it is aimed to collect the details on fly ash added
concrete and successful applications from field and literature surveys and
summarise them so that fly ash can be effectively used in Sri Lanka.
Objective
To achieve the aim following specific objectives are considered in the
present study:
(i) Understand the properties of fly ash added concrete
(ii)Identify suitable applications of fly ash in the Sri Lankan Construction
Industry together with proper mix design methods.

6. Scope of the study
As there are vast number of studies being carried out on fly ash, fly ash added concrete in the
international arena and considerable efforts have been already being taken by individuals and
organisations locally in Sri Lanka; the scope of the present study is limited to collecting some
of those details, analysing and summarising the findings.
Methodology
To achieve the first objective, first a thorough literature survey was carried out on fly ash
added concrete and its properties. Then from field surveys and literature data and details on
efforts to use fly ash added concrete in different applications already being in use in the Sri
Lankan construction industry, potential problems and methods to overcome them are found.
From the gathered information from literature and field surveys & local effort, properties of
fly ash added concrete and requirements for different applications were compared. Also the
effect of changing the volume of fly ash being added was analysed. Hence, recommendations
were made available for fly ash added concrete for various suitable applications.

7. LITERATURE REVIEW
Fly ash
Fly ash is the residue from combustion of pulverized coal
used as fuel. During the combustion of coal, the products
formed are classified into two categories viz.The bottom
ash is that part of the residue which is fused into
particles. The fly ash is that part of the ash which is
entrained in the combustion gas leaving the boiler. Most
of this fly ash is collected in either mechanical collectors
or electrostatic precipitators.

8. Production of Fly ash

9. Fly ash is the finely divided residue, resulting from the combustion of
pulverized coal, transported from the precipitators. The recognition
of the fly ash frequently exhibits pozzolanic properties have led to its
use. A pozzolana is defined as “a siliceous or siliceous and aluminous
material which in itself possesses little or no cementitious value but
which will, in finely divided form and in the presence of moisture,
chemically react with calcium hydroxide at ordinary temperature to
form compounds possessing cementitious properties”. The mineral
admixture is similar to cement but have very less binding property
compared to cement. The finer particles will fill the pores of cement
mortar paste and hence will reduce permeability and voids ratio.
Hence, mineral admixtures could be viewed as true friend of
concrete and cement mortars.
Fly ash – the mineral admixture

10. Properties of Fly ash
The properties of fly ash change with time, the nature of coal, its degree of grinding, boiler
operations, the type of fuel used, the type of separators used etc.
Physical Characteristics of Fly ash
Colour: Carbon and iron affect the colour of the fly ash. High carbon content changes the
colour to grey or black. High iron content produces a tin coloured ash.

11. • Fineness: using specific surface area fineness of fly ash can
be calculated and the values, which varies from 2x107 to
5x107 mm2/N. Greater fineness of fly ash, better the air
entraining admixture demand. Greater amount of surface
energy is consumed to combine fly ash with lime. The
fineness of the fly ash used as a percentage by weight
retained on 90-micron sieve is 9%.
• Shape: fly ash particles are spherical in shape and particle
sizes vary between 150micron and 1mm.

12. Chemical composition of Fly ash
Fly ash is categorized as Class F fly ash and Class
C due to the amount of calcium, silica, alumina,
and iron content in the fly ash .Also, chemical
properties of the fly ash are principally
influenced by the chemical content of the coal
burnt such as bituminous, Sub-bituminous and
lignite .

13. Component (%) Bituminous
(Class F)
Sub-bituminous
(Class C)
Lignite
(Class C)
Portland
Cement
SiO2 20-60 40-60 15-45 23
Al2 O3 5-35 20-30 20-25 4
Fe2 O3 10-40 4-10 4-15 2
CaO 1-12 5-30 15-40 64
LOI 0-15 0-3 0-5 0-4
It can be seen that Portland cement is rich in lime (CaO) while fly ash is low. Fly ash is
high in reactive silicates while Portland cement has smaller amounts. With these
chemical properties it is recommended to use fly ash with Portland cement since the
pozzolanic activity of fly ash. I

14. Reaction of fly ash in cement
Portland Cement + Water Calcium silicate hydrate
Free lime
Portland cement + Fly ash + Water Calcium silicate hydrate
Free lime Fly ash
It can be seen that pozzolanic reaction not only provides strength but also prevents
efflorescence, which occurs due to free lime leaching out from hardened concrete.

15. Microstructure of fly ash

16. Microstructure of fly ash and Portland cement
Fly ash
Portland cement

17. Application of Fly ash
• Cement production
• Fly ash in concrete
• Fly ash in asphalt pavements
• Fly ash in production of bricks
• Fly ash in Stabilized Base Course
• Fly ash in flowable fill
• Fly Ash in structural/ embankment fills
• Fly ash in soil improvement

18. Burj Khalifa, Dubai Petronas Towers, Kuala Lumpur

19. Laying of fly ash added
asphalt
Full depth reclamation of
bituminous road
Fly ash flowable fill Fly ash structural fill in highway embankment
Compaction of fly ash stabilized soil

20. Failures of fly ash application
• Consultant Lew Migliore of (LGM & Associates) raised an issue that is
just upcoming in the flooring industry. That is when increasing
proportions of fly ash in concrete underlayment are causing flooring
installation failures. When it comes to about 40% of fly ash content, it
starts to create issues of flooring materials not sticking to the surface of
the concrete. When increasing fly ash content up to about 60%, it is
likely anything to become very remote without sticking to concrete in
fly ash. This is because fly ash contains silicon dioxide and calcium
oxide.
• An aerated concrete block manufacturer had also faced a problem due
to use of fly ash with aerated concrete block. He used the mix design of
cement: fly ash ratio approximately 40:60. One day he got fly ash which
was slightly green tinted (colour like cement) and he made 14 numbers
of batches of 0.6 cubic metre mix, but 12 of them had failed. Even
though cement had set in same time but strength was not enough to
hold aerated bubbles. After 2-3 hours of casting, all bubbles which were
trapped in the slurry came up and freed to the air.

21. FIELD SURVEYS DATA AND LOCAL EFFORTS
In the process of Electricity generation in Puttalam Lakvijeya coal power station, nearly
70000 tons of fly ash gets produced per year is available as a by-product.
Tokyo super is the major customer of fly ash released from the coal power plant and
contribute 43 percent of the total production. Balance 57 percentage of fly ash is supplied
to Holcim (Lanka) Ltd, Sigiri Roofings (Pvt) Ltd, Fine Ash (Pvt) Ltd and Ceylon and Foreign
Trades.

22. Fly ash concrete in Sri Lanka
To find the possible percentage addition of fly ash, three grades of concrete namely
Grade 25, Grade 30 and Grade 35A were considered and then 20% and 25%
replacement of cement with fly ash were considered as trial mixes.
Identifica
tion
Ordinary
Portland
cement
(kg)
Fly Ash
(kg)
Fine
Aggregate
(kg)
Coarse
aggregate
(kg)
Water
(litres)
Admixture
1 (ml)
Admixt
ure 2
(ml)
Grade 25 348 0 770 1021 200 1480
Trial A 295 75 770 1021 200 1480
Trial B 277 93 770 1021 200 1480
Grade 30 408 0 698 1046 179 952
Trial A 341 85 698 1046 179 952
Trial B 320 106 698 1046 179 952
Grade 35A 370 0 734 1057 175 1000 3900
Trial A 340 85 734 1057 175 1000 3900
Trial B 325 100 734 1057 175 1000 3900

23. Test / Unit Test Method Results
Physical Parameters
Residue on 45 mm sieve by %
mass
BS 3892 : Part 1: 1982 30.03
Chemical Parameters
Loss on ignition / by % mass
Moisture content / by % mass
SO2 / by % mass
Total Chloride / by % mass
SiO2 / by % mass
Al2O3 / by % mass
Fe2O3 / by % mass
CaO / by % mass
BS 3892 : Part 1: 1997
1.2
0.16
0.26
Not detected
50.7
31.79
8.95
5.63
Test results of fly ash physical and chemical properties from Industrial
Technological Institute (ITI)

24. Fly Ash used in manufacturing bricks in Sri Lanka
Mix
identification
Fly Ash(g) Cement(g) Chips (g) Water
Mix 3600 330 2620 As required
Compaction by the tamping View of making Bricks

25. Fly ash in manufacturing low cost cement block
To identify low cost cement blocks, six categories of blocks were
• Type 01 - Cement, Quarry Dust, 10mm Aggregates & Water
• Type 02 – 5% of fly ash, cement, Quarry Dust, 10mm Aggregates & Water
• Type 03 - 10% of fly ash, cement, Quarry Dust, 10mm Aggregates & Water
• Type 04 - 15% of fly ash, cement, Quarry Dust, 10mm Aggregates & Water
• Type 05 - 20% of fly ash, cement, Quarry Dust, 10mm Aggregates & Water
• Type 06 - 25% of fly ash, cement, Quarry Dust, 10mm Aggregates & Water

26. Fly ash in cement concrete for road construction
Raw Materials
Volume per cubic meter of concrete mixture
Plain Cement Concrete Fly Ash Cement Concrete
Cement 0.14 m3 0.1 m3
Sand 0.29 m3 0.29 m3
Gravel 0.57 m3 0.57 m3
Fly Ash _ 0.04 m3
Total Volume 1.0 m3 1.0 m3
The actual weight and dimension of rectangular and cylindrical specimens used . The
specimen was cast in a rectangular mould approximately 154 mm. x 154 mm. x 460 mm.
and in a cylindrical mould approximately with diameter of 154 mm. and height of 306
mm. Each specimen is weighed before testing in the universal testing machine.

27. Fly ash in high performance concrete
In this research , mixture of fly ash with ordinary Portland cement were carried out in two
ways. First one is 5%,10%,20%,30%,40% and 50% replacement of cement by Fly ash and
another method is 25%fly ash replacement in Grade 70, Grade 80 and Grade 90 concrete.
Concrete Test
Cement
OPC
(kg)
Sand (kg)
Coarse
aggregates
(kg)
Water (l)
Admixture -
Glenium
233 (ml)
Fly ash (kg)
CI(OPC) 435 774 1026 174 4350
C10(OPC +5%FA) 413.25 774 1026 174 4350 21.75
C11(OPC+10%FA) 391.5 774 1026 174 4350 43.5
C12(OPC+20%FA) 348 774 1026 174 4350 87
C13(OPC+30%FA) 304.5 774 1026 174 4350 130.5
C14(OPC+40%FA) 261 774 1026 174 4350 174
C15(OPC+50%FA) 217.5 774 1026 174 4350 217.5
Mix design of OPC with Fly ash

28. Mix of OPC and PPC
Concrete
Test
Cement
OPC (kg)
Cement
PPC (kg)
Sand (kg)
Coarse
aggregates
(kg)
Water
(l)
Admixture
-Glenium
233 (ml)
Fly ash
(kg)
G70 OPC 400 760 900 170 7000 125
G80 OPC 420 740 900 170 7500 145
G90 OPC 435 740 900 150 7500 145
G70 PPC 400 760 900 170 7000 125
G80 PPC 420 740 900 170 7500 145
G90 PPC 435 740 900 150 7500 145

29. Concrete mix design in Sri Lanka
Grade 30 concrete mix design
Maga Concrete Mix design
CML Concrete Mix design
Quantities Cement (kg) Fly ash (kg) Water (l)
Fine
Aggregate
(kg)
Uncrused
70%
Fine
Aggregate
(kg) crused
30%
Coarse
Aggregate
(kg)
Retarder (l)
Superplastici
ser
Per 01m3 300 100 176 561 241 1062 1.05 2.8
Quantities Cement (kg) Fly ash (kg) Water (l)
Fine Aggregate
(kg)
Coarse
Aggregate (kg)
Admixture (ml)
Per 01m3 370 47 178 901.3 901.2 3500

30. Concrete Mixes
No.
ELS/B/001 ELS/B/002 ELS/B/004 ELS/B/011 ELS/B/006
Concrete Grade
(N/mm2)
50 40 40 40 25
10-20 mm
Aggregate (kg) 680 662 662 685 682
5-10 mm
453 441 441 456 455
Aggregate (kg)
River Sand (kg) 747 799 799 761 610
Quarry Dust - - - - 205
Water (L) 174 144 156 156 152
Cement (kg) 380 355 355 335 272
Fly Ash 70 70 70 60 48
Admixture Name SP 430 SP 430 SP 430 SP 430 SP 430
Dosage Range 1.4 1.25 1.25 1.25 1.5
Admixture (L) 6.3 5.313 5.313 4.938 4.8
Slump(mm) 60 130 100 120 100
% passing 0.6mm 41 39 39
Water Cement
Ratio 0.39 0.34 0.37 0.39 0.56
ELS Concrete Mix design

31. ANALYSIS OF RESULTS & RECORDS
Fly ash Concrete in Sri Lanka
Identification
Average Compressive strength (N/mm2)
3 days 7 days 21 days 28 days
Concrete with fly ash
Grade 25 - Trial A 22.8 27.5 33.5 35.5
Grade 30 - Trial A 25.6 29.7 39.5 43.2
Grade 35A- Trial B 37.9 43.2 52.5 54.2
Concrete without fly ash
Grade 25 23.3 27.7 30.1 35.2
Grade 30 26 31.2 36.7 39.8
Grade 35A 31.5 33.7 41.8 44.1

33. Fly ash manufacturing bricks in Sri Lanka
Sample
Dimensions (mm) Compressive
Strength
(N/mm2)
Water
absorption
(%)
Length Width Height
1 230 109 70 3.5
9.8
2 231 108 72 3.3
14.4
3 232 110 73 3.4
11.2
4 231 108 72 3.1
8.6
5 230 108 72 3.4
14.9
6 231 107 70 3.3
13.4
7 231 108 72 3.5
13.3
8 230 108 72 3.6
13.4
9 229 110 70 3.3
13.7
10 230 107 69 3.6
13.1
Average Compressive strength of the 10 bricks is 3.4 N/mm2 and is satisfactory for the
requirement. Because the minimum compressive strength according to SLS 855: Part 1 is 1.2
N/mm2 .

34. Fly ash in manufacturing low cost cement block
Price for 1kg of material
Fly ash = Sri Lanka Rupees. 0.90 Quarry Dust = Sri Lanka Rupees1.60
Cement = Sri Lanka Rupees 15.30 10mm Aggregates = Sri Lanka Rupees 1.56.
The 28 days’ compressive strength values for all the types of cement blocks satisfy the
requirements of Sri Lankan Standard SLS 855: Part 1: 1989 “Specification for Cement
Blocks” Part 1: Requirements

35. Fly ash cement concrete for road construction
By comparing the results between plain concrete and fly-ash cement concrete specimen, it
can be found that the strength of fly-ash cement concrete develops at a faster rate than the
plain cement concrete specimen after 7 days.
Comparative Flexural Strength Test Results of Plain Concrete and Fly Ash Cement
Concrete
Comparative Compressive Strength Test Results of Plain Concrete and Fly Ash
Cement Concrete

36. Fly ash in high performance concrete
Concrete Test
Compressive strength (N/mm²)
7 Days 28 Days 60 Days
CI(OPC) 46.3 57.7 59
C11(OPC+10%FA) 53 61.4 64.1
In this research 100 % ordinary Portland cement concrete have the lesser compressive
strength than the 10% fly ash added concrete.

37. In Sri Lankan mix design, fly ash has been used from 13% to 33% replacement by cement to
get the compressive strength. So we can get it a good approach because 12% to 24% of fly
ash had been used in the mix design of world tallest building Burj Dubai.
Concrete mix design in Sri Lanka
Concrete Mixes No. ELS/B/001 ELS/B/002 ELS/B/004 ELS/B/011 ELS/B/006
Concrete Grade (N/mm2) 50 40 40 40 25
Water/Cement 0.39 0.34 0.37 0.39 0.56
Strength (N/mm2)
3 days (Av.) 32.9 29.5 22.4 24.15 14.9
Strength (N/mm2)
7 days (Av.) 37.57 37.8 30.45 30.66 20.13
Strength (N/mm2) 28days
(Av.)
51.47 51.98 39.98 44.23 29.67
Strength (N/mm2) 56days
(Av.)
57.24 57.78 46.2 50.27 35.2

38. • Earlier strength (3day and 7day) compressive strength of fly ash cement concrete is
lesser than the ordinary Portland cement after that fly ash cement compressive
strength gain accelerate.
• Replacement of cement by fly ash increase the compressive strength of the concrete.
Especially 5% replacement of cement by fly ash have better compressive strength
compared to 10%, 15%, 20% and 25% .
• 20% of cement replacement by fly ash provides better strength than 25% of cement
replacement fly ash in Grade 25 and grade 30 concrete. And 25% cement replacement
by fly ash provides better strength in Grade 35 A concrete.
• Rate of strength development at various age is related to the water cement ratio (W/C).
In Grade 40 Mix Design the difference between the concrete mixture ELS/B/002 &
ELS/B/004 is W/C of 0.34 & 0.37 respectively and compressive strength at 28 days are
51.98 and 39.98. ELS/B/004 not satisfy the strength at 28 days but it satisfied the
strength requirement at 56 days and is 46.2.
• According to the sieve analysis test results, it is proved that the fly ash from
Norochcholai coal power plant meets the ASTM requirements for mineral filler. And fly
ash in hot asphalt mix result conforming to specification were obtained 42% mineral
filler replacement quarry dust by fly ash.
Summary of Observations

39. Conclusions
• Physical and chemical properties found from literature
for fly ash. This explains using fly ash as a construction
raw material have better strength but the delay in
strength gain at early age of concrete. Hence for
applications where early strength gain is needed adding
fly ash may not be desired.
• Some of the applications found from field survey and
literature view and findings are summarised in summary
of observation .

40. Recommendation for future work
In the present study use of fly ash in concrete, cement
block and production of cement are highlighted, that
can satisfy the requirement and cost effectiveness. It is
recommended to use in road stabilization and asphalt
concrete in future. Most of the time, due to
modification in the strength gaining process/rate fly ash
added concrete has caused problems. Hence, it is
recommended to carry out trials and also collect data
from ready mix suppliers with fly ash to have a database
so that strength gaining pattern can be identified based
on mix proportions.