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Systematic formulation of high performance concrete pavement.

ABSTRACT

Following a [2.sup.5-1] fractional factorial design concept, an experiment was planned ; sixteen experimental mixes were calculated from a basic mix (cement : sand : aggregates : fly ash = 1 : 1.3 : 2.6 : 0.8 and W/C ratio of 0.37) and determined changes (cement = 0.1 ; sand = 0.1 ; aggregates = 0.2 ; fly ash = 0.04 and changing W/C ratio by 0.01) using Taguchi's orthogonal array. Samples were made from each data point. Compressive strength and water absorption were determined after each of two curing conditions (a) 28 days in the water, (b) 28 days in the water and 32 days in the air after that. Mix no 12 [Cement : Sand : Gravel : Fly Ash = 0.9 : 1.2 : 2.8 : 0.76] was found to have highest compressive strength and lowest water absorption.

Keywords: fractional factorial, fly ash, water absorption, compressive.

INTRODUCTION

The Indonesian development in construction during this globalization era is very rapid and as a result, the need of construction materials is increasing rapidly. Since the supply of such materials is not increasing at the same rate, there is increase of price. If the waste materials can be used to make useful construction materials, the price of such materials can be kept down.

Fly ash is a waste material obtained in thermal power plants and other plants during burning of pulverised coal. Fly ash has been studied extensively as a material and from the point of view of its impact on the environment. In this research we have shown a method to make concrete pavement using fly ash as one component.

Most of the paving bricks normally used here do not meet the international standard. It has been shown in this research that by systematic formulation paving bricks of very high quality can be made using fly ash. People generating fly ash and those utilizing it for product development will find this research beneficial. Those who use products made with fly ash will also benefit in terms of lower buying cost. In recent years, there has been a growing interest to develop cementitious products using fly ash.

Roller Compacted Concrete with improved properties has been made using fly ash and water reducing admixture in the formulation and utilizing the vibrating roll compaction technology [1].

Considerable saving of cost can be achieved in making ready mix concrete by using up to 30% of standard quality fly ash [2]. High Performance concrete has been made incorporating fly ash in the formulation [3].

Asphalt concrete made by replacing 10% fine aggregate by ash can be successfully used in road construction. This replacement could fulfill all standard requirements except the air void. To improve the air void, an additive (chemcrete) can be added. The use of chemcrete can increase the stability and improves the air void of asphalt concrete [4].

Fly ash has also been used in formulation of crack free mortar [5]. The preliminary study on paving bricks from five randomly selected sources gave the following compressive strength and cost values (Table 1).

However the BS 6717: Part 1 requires the paving bricks to have a minimum strength of 49 MPa. The weakness of the bricks can't be understood from the appearance but this weakness is responsible for premature failure of many road pavement requiring early repair and replacement [6]. Fly ash is rich in silica and alumina. The chemical composition of a typical fly ash is given in Table 2.

[Al.sub.2][O.sub.3] forms mullite (M) with Si[O.sub.2] and the remaining Si[O.sub.2] is present as Quartz (Q) in fly ash. Typical X-ray diffraction pattern of fly ash is shown in figure 1; the figure indicates the presence of quartz and mullite as the two major phases.

[FIGURE 1 OMITTED]

In this research sixteen experimental formulations based on a [2.sup.5-1] fractional factorial design were studied for compressive strength and water absorption. The size fractions and the fineness modulus of the sand and the coarse aggregate used were also measured. A further study of the effect of replacement of sand by fly ash was done.

EXPERIMENTAL

Sieve numbers 10mm to 0.063mm were used for the sieve analysis of the sand and the gravel used in this experiment [7]. The sieve analysis of the sand and the gravel used are given in Table 3.

From the sieve analyses the calculated fineness modulus of the sand and of the gravel were 1.24 and 4.72 respectively. Standard Portland cement of Gresik Cement Type I and municipal water were used. Fly ash used was obtained from Tjiwi Kimia. Madiun sand and coarse aggregate were used. Compressive Strength was measured using Compression Machine in Cement Gresik as per BS 6717; Part 1 1986. Water absorption of each sample was also measured from the dry weight and the wet weight of the samples [6].

Using a basic formula (cement : sand : aggregates : fly ash = 1:1.3:2.6:0.8 and W/C ratio of 0.37) and fixed change in each constituent (cement = 0.1 ; sand = 0.1 ; aggregates = 0.2 ; fly ash = 0.04 and changing W/C ratio by 0.01) 16 experimental mixes were determined following Taguchi's orthogonal array. Each factor was studied at two levels [8]. The sixteen mixes thus obtained are given in Table 4.

Five cubes (20x10x6) cm3 were made from each mixes and compressive strength as well as water absorption was determined on each cube.

RESULTS

The average compressive strength and the average water absorption of the 16 mixes are given in Table 5.

The highest strength was obtained in sample number 12 and this sample also had the lowest water absorption after 28 days of curing in water. The effect of keeping the blocks in the room air for additional 32 days caused an average increase of compressive strength of 32.6%. This can be seen in Table 6. This shows the need to keep the blocks in moist storage for a period before actual paving is done.

The measured compressive strength and the water absorption data are found to be related as in figures 2 and 3.

[FIGURE 2 OMITTED]

From the linear regression equation in Figure 2. shows that every 1% water absorption increase will cause 2.3489 MPa strength decrease [9].

[FIGURE 3 OMITTED]

CONCLUSION

a. Fractional factorial design technique is found useful to develop paving bricks.

b. Composition no.12: Cement : Sand : Gravel : Fly Ash = 0.9 : 1.2 : 2.8 : 0.76 is found, in this study, the best for making paving blocks.

c. Composition no.12 has a compressive strength of 61.7 MPa after curing 28 days in the water.

d. Air curing for 32 days after water curing for 28 days can give 32.58% higher strength.

e. The research shows that economic paving blocks with quality better than BS 6717: Part 1 1986 can be made with local resources.

REFERENCES

[1.] Jiaping, Liu, Wei, Sun and Honggen, Qin, Study on Physical and Mechanical Properties of Roller Compacted Concrete with Fly Ash for High Way Use, China Southeast University, Nanjing, 1995.

[2.] Lai, A.K., Fly Ash in Building Construction, National Workshop on Utilization of Fly Ash, Roorke, 19-20 Mei 1988.

[3.] Roy, S.K., P.K. Gangopadhyay, R.Roy., R.. Sen and V. Sundaram, Utilization of Fly Ash with Specal Reference to Its Use in High Performance Concrete, International Conference on Concrete Engineering and Technology, Kuala Lumpur, Malaysia, 6-8 May 1997.

[4.] Santoso, Indriani and Kumar Roy, Salil, Pengaruh Penggunaan Bottom Ash Terhadap Karakteristik Campuran Aspal Beton, Dimensi Teknik Sipil, vol. 5 no. 2, U.K. Petra, Surabaya, September 2003.

[5.] Rehsi, S.S., Factors Affecting Strength of Structural Fly Ash Concrete, National Workshop on Utilization of Fly Ash, Roorke, 19-20 Mei 1988.

[6.] British Standard Precast Concrete Paving Blocks, BS 6717: Part 1, British Standard Institution, 1986.

[7.] British Standard Coarse and Fine Aggregates From Natural Sources, BS 882: Part 2, British Standard Institution, 1973.

[8.] Montgomery, Douglas C., Design and Analysis of Experiments 5th Edition, Arizona State University, John Wiley and Sons, Inc., 1993.

[9.] Kume, Hitoshi, Metoda Statistik Untuk Peningkatan Mutu, Mediyatama Sarana Perkasa, Jakarta, 1988.

Note: Discussion is expected before November, 1st 2005. The proper discussion will be published in "Dimensi Teknik Sipil" volume 8, number 1, March 2006.

Salil Kumar Roy

Lecturer, Postgraduate Program in Civil Engineering, Petra Christian University Surabaya

Handoko Sugiharto

Lecturer, Department of Civil Engineering and Planning, Petra Christian University, Surabaya

Anton Kristanto, Salim Himawan S.

Alumni Department of Civil Engineering and Planning, Petra Christian University, Surabaya
Table 1. Mean Compressive Strength and Cost
of Five Locally Available Paving
Bricks

Source Number    Strength ,MPa     Price/[m.sup.2] (Rp)

      1               42.4                25,500
      2               24.0                22,600
      3               33.1                24,000
      4               27.3                23,800
      5               20.4                24,000

Table 2. Typical Analysis of a Fly Ash

Oxide Constituent    Weight (%)

Si[O.sub.2]              60
Al2[O.sub.3]             24
Fe2[O.sub.3]              5
Ti[O.sub.2]               1
CaO                       4
MgO                       1
[Na.sub.2]O               0.2
[K.sub.2]O                1.8
L.O.I                     3

Total                   100

Table 3. Sieve Analysis of Sand and Aggregate

Sieveness     Gravel
Number
             % Weight     [summation] % Weight
             Retained           Retained

10.000 *       0.202              0.202
 5.000 *      12.340             12.542
 2.360 *      72.730             85.272
 1.180 *       5.481             90.753
 0.600 *       2.354             93.107
 0.300 *       1.311             94.418
 0.150 *       1.614             96.032
 0.063         2.656             98.688
Bottom         1.312            100.000
Total        100.000

Sieveness      Sand
Number
             % Weight     [summation] % Weight
             Retained           Retained

10.000 *
 5.000 *       0.000              0.000
 2.360 *       0.510              0.000
 1.180 *       0.204              0.510
 0.600 *       0.204              0.714
 0.300 *      25.400              0.918
 0.150 *      69.450             26.318
 0.063         4.182             95.768
Bottom         0.050            100.000
Total        100.000

* = standard of sieve to calculate the fineness odulus

Table 4. Sixteen Experimental Mixes

   No       Cement      Sand      Gravel     Fly Ash      W/C
Treatment     (A)        (B)        (C)        (D)        (E)

   1          1.1        1.4        2.8       0.84       0.38
   2          1.1        1.4        2.8       0.84       0.36
   3          1.1        1.4        2.8       0.76       0.38
   4          1.1        1.4        2.8       0.76       0.36
   5          1.1        1.2        2.4       0.84       0.38
   6          1.1        1.2        2.4       0.84       0.36
   7          1.1        1.2        2.4       0.76       0.38
   8          1.1        1.2        2.4       0.76       0.36
   9          0.9        1.2        2.8       0.84       0.38
  10          0.9        1.2        2.8       0.84       0.36
  11          0.9        1.2        2.8       0.76       0.38
  12          0.9        1.2        2.8       0.76       0.36
  13          0.9        1.4        2.4       0.84       0.38
  14          0.9        1.4        2.4       0.84       0.36
  15          0.9        1.4        2.4       0.76       0.38
  16          0.9        1.4        2.4       0.76       0.36

Table 5. Compressive Strength and Water Absorption Data

          Curing 28 days in        Curing 28 days in water + 32
            water                    days in air after that

Sample      Water      Strength       Water       Strength
number     Abs (%)       (MPa)       Abs (%)        (MPa)

  1          6.4         44.00         6.2          58.70
  2          3.4         50.03         3.1          67.02
  3          8.6         37.27         8.4          49.18
  4          2.6         51.04         2.4          68.06
  5          7.4         41.82         7.2          56.20
  6          2.8         51.66         2.5          70.14
  7          4.6         52.08         4.3          66.64
  8          1.4         58.72         1.1          78.42
  9          6.2         48.62         6.0          62.96
 10          4.7         49.36         4.5          66.48
 11          8.5         42.58         8.3          56.27
 12          1.3         61.74         1.2          79.78
 13          2.4         51.19         2.2          68.98
 14          5.6         49.74         5.4          66.51
 15          6.4         48.34         6.3          64.34
 16          1.7         57.74         1.5          75.01

Table 6. Effect of Extra Curing for 32 Days in Air

                  Compressive Strength  (MPa)

Compo-    Curing 28 days    Curing 28 days in water      Strength
sition       in water          + 32 days in the        difference(%)
                                air after that

  1           44.00                  57.70                 3.34
  2           50.03                  67.02                 3.39
  3           37.27                  49.18                 3.19
  4           51.04                  68.06                 3.33
  5           41.82                  56.20                 3.43
  6           51.66                  70.14                 3.57
  7           52.08                  66.64                 2.79
  8           58.72                  78.42                 3.35
  9           48.62                  62.96                 2.94
 10           49.36                  66.48                 3.46
 11           42.58                  56.27                 3.21
 12           61.74                  79.78                 2.92
 13           51.19                  68.98                 3.47
 14           49.74                  66.51                 3.37
 15           48.34                  64.34                 3.30
 16           57.74                  75.01                 2.99

                                    Mean :                 3.25
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Author:Roy, Salil Kumar; Sugiharto, Handoko; Salim Himawan S., Anton Kristanto
Publication:Civil Engineering Dimension
Article Type:Report
Geographic Code:9INDO
Date:Sep 1, 2005
Words:2196
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