1 INTRODUCTION Concrete made with natural aggregate originating

from hard rock has a density within a narrow range because the specific gravity of most rocks varies little [1]. In practice, the density of normal weight con-crete lies within the range of 2300 to 2500 kg/m3. Density of concrete can contribute significantly to the self-weight of concrete elements. By using concrete with a lower density can have an important effects structurally and economically. The British Standard, BS 8110: Part 2: 1985 [2] classified lightweight con-crete as concrete having densities of 2000 kg/m3 or lower while the Draft International Standard Model Code for Concrete Construction classifies lightweight concrete as having densities between 1200 and 2000 kg/m3. However, according to Ne-ville [1], the practical range of densities of lightweight concrete is between about 300 and 1850 kg/m3. Generally, concrete with density between 2000 and 2300 kg/m3 can be classified as medium lightweight concrete.

Malaysia is well known for its palm oil industry, producing a total of more than 10 million tons of crude palm oil annually, making our country the larg-est producer of palm oil in the world. However, the palm oil industry also produces some kind of waste, named as palm oil clinker (POC) and palm oil fuel ash (POFA). POC is a waste by-product produced by palm oil mill from the boiler. According to BS 3797: 1990[4], clinker is defined as a fused residue from furnaces fired with coal which has not been pulve-rized. The same situation goes to POC, which is ob-tained, from the furnaces in the process of palm oil. POC is suitable to be used as lightweight aggregate where the physical and mechanical properties are ful-

filling the British Standard 3797: 1990 [7]. POFA is obtained from a palm oil mill, which produced well-burnt fuel (shell and fibres). The ash is grey in color.

This paper reports the result of experimental study on the full replacement of POC as coarse aggregate to produce a medium lightweight concrete containing unprocessed POFA varied from 5 % - 15 % as the partial cement replacement material.

2 EXPERIMENTAL WORK 2.1 Preparation of material The cement used was ordinary Portland cement while POFA varied from 5 to 15% were used to replace the total cement required. Kahang sand was used as fine aggregate and palm oil clinker as coarse aggregate. DOE (Department of the Environment) mix design guideline was used as the guide in designing the me-dium lightweight concrete.

The clinker and POFA were taken from Kian Hoe Plantation Berhad, a local palm oil mill situated in Kluang, Johor. All the clinkers taken out from the boiler need to be crushed into smaller size (Figure 1). The clinkers were crushed manually by using hammer so that it can fit to a size average of 20 mm. The clinker aggregates were then sieved using BS 410 sieve sizes in order to segregate the aggregate to re-quire to nominal size of 20 mm, which will be used as coarse aggregate replacing gravel (Figure 2). For those aggregate larger than 20 mm will be crushed again until it is 20 mm or smaller than that while those smaller than 5 mm will be discard. Figure 3 and Figure 4 show the grading curve for fine and coarse aggregate.

Medium Lightweight Concrete Containing Palm Oil Fuel Ash (POFA)

Koh Heng Boon, Y.L. Lee & David Yeoh Eng Chuan Department of Civil Engineering, Faculty of Engineering, Kolej Universiti Teknologi Tun Hussein Onn 86400 Parit Raja, Batu Pahat, Johor ABSTRACT: This paper discusses the results of a study on the use of palm oil clinker (POC) to replace coarse aggregate to produce medium lightweight concrete. Five types of concrete mixes containing palm oil fuel ash (POFA) varied from 5 % - 15 % were used as the partial cement replacement material. Compressive strength, density, workability and water permeability of this medium lightweight POFA concrete is determined to com-pare with the control mix (0 % POFA). It is found that the compressive strength of POFA mixes increased by an average of 8% - 14% compared to the control mix. The average coefficient of water permeability for me-dium lightweight POFA concrete is in the order of 10-11 m/s, which can classified as concrete with average quality. Study has shown that by utilizing POC and POFA, a good performance medium lightweight concrete can be produced. Key words: Medium lightweight concrete, palm oil fuel ash, partial cement replacement, compressive strength, water permeability.

Figure 1. Clinker in original size

Figure 2. Clinker after process

Figure 3. Grading curve for fine aggregate

Figure 4. Grading curve for POC coarse aggregate

2.2 Procedure of Batching the Materials After the trial mix process, the fresh concrete was cast in 100 mm x 100 mm x 100 mm steel mould. The moulds have to be greased before placing the concrete. This is to ensure that the concrete cube can be taken out from the mould easily. The hand rod-ding and mechanical vibrations methods are com-monly applied in the compaction of concrete. The mechanical vibration used in this project is the vibrat-

ing table. The mould is opened one day after placing the

concrete and the concrete cubes are placed in the curing tank at a temperature of approximately 27 C. The concrete cubes were subjected to water permea-bility and compressive strength test at 7, 28 and 56 days. The water permeability test is performed using KUiTTHO Dual Test System, which is developed based on ISO/DIS 7031.

3 RESULT AND DISCUSSION 3.1 Density of concrete In this project, the density of concrete for all con-crete cubes were measured before subjected to water permeability and compressive strength test. Based on Figure 5, the average density for POC medium lightweight concrete is around 2100 kg/m3.

Figure 5. Density of POFA lightweight concrete

3.2 Workability The slump test based on BS 1881: Part 102: 1983 was used to determine the workability of the con-crete mixes. The slump was controlled as medium category of workability in the range of 60 mm to 80 mm. As shown in Figure 6, the slumps of the con-crete mixes are within the targeted workability.

Figure 6. Relation between slump and percentage of POFA

Relation between slump and percentage of POFA

Slu

mp

(mm

)

40

50

60

70

80

0% 5% 8% 10% 12% 15%

Percentage of POFA

7 days 28 days

56 days

2000

2050

2100

2150

Density of Medium lightweight concrete

D

ensi

ty o

f con

cret

e (k

g/m

3)

0% 5% 8% 10% 12% 15%

Percentage of cement replacement (POFA)

1.18mm 2.36mm 5.0mm 10mm 20 mm

Sieve size (BS 410: 1986)

Perc

enta

ge

pass

-

Coarse Aggregate

(Grade 20mm)

0

20

40

60

8

0

1

00

75 m 300 m 1.18 mm 5.0 mm 20

Sieve size (BS 410: 1986)

Perc

enta

ge p

assi

ng

Fine Aggregate

(Zone 1)

0

20

40

6

0

80

1

00

The slump can be maintained at a certain level by reducing the water cement ratio for POFA mixes. This shows that the spherically molecule of POFA produces a lubricating function. Figure 7 shows the water cement ratio used for the concrete mixes.

Figure 7. Relation between water cement ratio and percentage of POFA

3.3 Compressive Strength

A total of 6 types of concrete mix are compared in the compressive strength development. The compres-sive strength was done at 7, 28 and 56 days using the ELE Compact 1500 Machine. A graph of relation be-tween the compressive strength and age of concrete was plotted. Based on Table 1 and Figure 8, it shows that there are steady strength developments for each type of mix. It was found that, a higher compressive strength was obtained for POFA medium lightweight concrete mixes compared with the control mix (without POFA) for 7, 28 and 56 days compressive strength. The average 56 days compressive strength of the control mix is 30.9MPa. An increment of 7.8%, 8.7%, 10.7%, 11.65% and 13.6% of compres-sive strength was respectively gained for mix with 5% POFA, 8% POFA, 10% POFA, 12% POFA and 15% POFA as cement replacement.

Table 1. Concrete Cube Compressive Strength Result

Palm Oil Fly Ash

(POFA) %

Compressive Strength (N/mm2) 7 days 28 days 56 days

0 15.4 25.8 30.9 5 15.7 26.3 33.3 8 17.4 26.7 33.6 10 17.6 26.9 34.2 12 18.2 26.9 34.5 15 17.9 27.3 35.1

Figure 8. Relation between compressive strength and age of concrete

3.4 Effect of water/cement ratio on the strength of concrete

Figure 9 shows that a lower water/cement ratio mix produces a higher compressive strength at 7, 28 and 56 days.

Figure 9. Relation between Compressive Strength and Age of Concrete with Different Water/Cement Ratio

3.5 Water permeability

Water permeability test is done at 7 days, 28 days and 56 days using the Germans Water permeability Test (GWT). This is a Non Destructive Test (NDT) method on standard test cube prior to the determina-tion of compressive strength. Figure 10 and Table 2 show that the relation between coefficient of per-meability and age of POFA concrete mix. The aver-age coefficient of water permeability for medium lightweight POFA concrete is in the order of 10-11 m/s, which can be classified as concrete with average quality. Study has shown that POFA has the potential to reduce the water permeability of medium lightweight concrete.

Relation between Compressive strength and Age of concrete

10

15

20

25

30

35

40

Com

pres

sive

Str

engt

h (N

/mm

2 )

OPC 5POFA 8POFA 10POFA 12POFA 15POFA

0 7 14 21 28 35 42 49 56 63 (Day)

Relation between Water/cement ratio and Percent ofPOF

W/C

Rat

io

0.5

0

.51

0.5

2 0

.53

0.5

4 0

.55

0% 5% 8% 10% 12% 15%

Percentage of POFA

0 5

10

15

20

25

30

35

40

OPC 5POFA 8POFA 10POFA 12POFA 15POFA Age at Test- Days

Relation between Compressive Strength and Age ofConcrete with Different Water Cement Ratio

7-

days 28-days56-days

Com

pres

sive

Stre

ngth

(N/m

m2 )

0.542 0.54 0.538 0.533 0.53 0.528

Figure 10. Relation between Coefficient of Permeability and Age of Concrete

Table 2 Water Permeability Test Result

Palm Oil Fuel Fly Ash (POFA) %

Coefficient of Water Permeability, Ccp (m/s)

7 days 28 days 56 days 0 8.75E-11 7.29E-11 6.75E-11 5 8.69E-11 7.16E-11 6.71E-11 8 8.66E-11 7.14E-11 6.70E-11

10 8.63E-11 7.08E-11 6.66E-11 12 8.47E-11 7.06E-11 6.60E-11 15 8.03E-11 6.98E-11 6.58E-11

4 CONCLUSION

Based on the results of the study, the following con-clusions can be made:

i. The average density for this mixture is around

2100 kg/m3 which is about 12.5% lower than the normal weight aggregates concrete.

ii. The coefficient of water permeability for the medium lightweight concrete mix is around 10-11 m/s, which can be classified as concrete with av-erage quality.

iii. Higher percentage of POFA produces a higher compressive strength and lower water permea-bility medium lightweight concrete.

5 REFERENCES

1. Neville A. M. (1995). Properties of Concrete. London: Pitman Books.

2. British Standards Institution (1985). Structural use of concrete. London: (BS 8110).

3. British Standards Institution (1997). Method for Specifying Concrete Mixes. London: (BS 5328: Part 2).

4. British Standards Institution (1990). Specifica-tion for Lightweight aggregates for masonry units and structural concrete. London: (BS 3797).

5. Clark, J. L. (1993). Structural Lightweight Aggregate Concrete. Glasgow: Blackie Aca-demic & Professional.

6. Comitee Euro-International du Beton (CEB) and Federation Internationale de la Precon-trainte (FIP). (1997). Lightweight Aggregate Concrete. Lancaster, England: The Construc-tion Press.

7. Koh Heng Boon (2003). The Use Of Palm Oil Clinker In Reinforced Lightweight Concrete Beam. Fundamental research final report: KUiTTHO.

8. Wahid Omar and Roslli Noor Mohamed (2001). Properties of Lightweight Concrete Using Palm Oil Clinker in Prestressed Concrete Beam. 7th International Conference on Con-crete Engineering and Technology. 127-133.

9. The Institution of Structural Engineers (1987). Guide to the Structural Use of Lightweight Aggregate Concrete. London: The Concrete Society.

Relation between Coefficient of Permeability and Age of Concrete

6.5

7

7.5

8

8.5

9

OPC 5POFA 8POFA 10POFA 12POFA 15POFA

0 7 14 21 28 35 42 49 56 63 (Day)

C

oeff

icie

nt o

f Per

mea

bilit

y (x

10-1

1 m/s)

full paper for National Civil Engineering Conference 2004 organised by USM