Replacement of Fine Aggregate with Bottom Ash in Concrete and Investigation on Compressive Strength

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Replacement of Fine Aggregate with Bottom Ash in Concrete and Investigation on Compressive Strength

Dr. R. G. D Souza Principal , YIT, Moodabidri, Karnataka, India

Abstract – Coal bottom ash is a coarse granular and incombustible byproduct from coal burning furnaces. The appearance and particle size distribution of coal bottom ash is similar to that of river sand and makes it attractive to be used as fine aggregate in the production of concrete. The other advantage of using bottom-ash is that it can be dust free, the sizes of bottom-ash can be controlled easily so that it meets the required grading for the given construction. Bottom ash also exhibits a relatively high permeability and grain size distribution that allows the design engineer to use it in direct contact with impervious material. Bottom ash is used as concrete aggregate or for several other civil engineering applications where sand, gravel and crushed stone are used. In the present work M20, M25 and M30 grade of concrete is considered for the experimental investigation. Fine aggregate is fully replaced with 100% percentage of bottom ash. Comparative result of workability and compressive strength of conventional concrete cube and bottom ash added concrete cube are reported. From the results it is concluded that bottom-ash can be used as a replacement for fine aggregate. The results proved that the replacement of 100% of fine aggregate by bottom-ash achieved higher compressive strength. Thus the environmental effects due to illegal extraction of sand and cost of conventional fine aggregate can be significantly reduced.

Key Words: bottom ash, fine aggregate, replacement, concrete

  1. INTRODUCTION

    Coal-based thermal power plants all over the world face serious problems in the handling and disposal of the ash produced. The utilization of fly ash is about 30% in various engineering requirements that is for low technical applications such as in construction of fills and embankments, backfills, pavement base and sub base course. Coal bottom ash is a coarse granular and incombustible byproduct from coal burning furnaces. It is composed of mainly silica, alumina and iron with small amounts of calcium, magnesium sulfate, etc. The appearance and particle size distribution of coal bottom ash is similar to that of river sand. Bottom ash based artificial lightweight aggregate offer potential for large scale utilization in the construction work. The other advantage of using bottom-ash is that it can be dust free, the sizes of bottom-ash can be controlled easily so that it meets the required grading.

    Mohd Syahrul Hisyam bin Mohd Sani et al. [1] studied the compressive strength of concrete mixes made with various

    % of Washed Bottom Ash as fine aggregate replacement. The compressive strength of control sample (fully natural sand) was determined at 3, 7, 28, and 60 days of curing. It was seen that the compressive strength of concrete mixes of sand replacement is much lower than control sample at all tested days. According to M. Purushothaman et al. [2] Bottom Ash added Concrete mixes showed enhanced compressive strength than the conventional concrete and showed uniformly higher compressive strengths at almost all ages. The ample gain in strength is thought to be due to very high pozzolanic reactivity of the two mineral admixtures silica fume and bottom ash. P. Tang et al. [3] studied the compressive and flexural strength of concrete drain with the augmentation of the bottom ash fines at the identical curing age, particularly after 3 and 7 days. M.P. Kadam et al. [4] carried out Compressive strength tests of concrete mix made with and without coal bottom ash of cubes size 1.5 cm × 1.5 cm × 1.5 cm and the results were determined at 7, 28, 56, and 112 days. It was observed that for 10 % and 20 % sand replacement the compressive strength was increased by 4.6 %, 3.99 %, 0.61%, 0.20 %

    for 7, 28, 56 and 112 days respectively as compared with controlled concrete. The compressive strength was decreased from 30% to 100 % replacement 2.07 % to 22.30%, 4.97 % to 33.66 %, 1.23 % to 38.99%, and 0.78 %

    to 36.83 % for 7, 28, 56 and 112 days respectively as compared with controlled concrete. The study of K. Soman et al. [5] shows that 30% replacement of sand with bottom ash has given a 28 day compressive strength of 38.43 kN/m2 (target mean strength is 38.25kN/m2). The result showed that bottom ash can be used to substitute sand and the ideal replacement level was 30%. Remya Raju et al. [6] observed that Compressive strength reduced marginally on the inclusion of bottom ash in concrete.

  2. MATERIALS

    Bottom ash which is a by-product of burning coal at thermal power plants has particles much coarser than the fly ash. It is a coarse, angular material of porous surface texture predominantly sand-sized. This material is composed of silica, alumina, and iron with small amounts of calcium, magnesium, and sulfate. Grain size typically ranges from fine sand to gravel in size. Chemical composition of bottom ash is similar to the fly ash but typically contains greater quantity of carbon. Bottom ash

    Sieve size

    Materials retained on each sieve in grams

    Cumulative mass in grams

    Cumulative % mass retained

    % passing

    Requirements as per IS 383-1970 % passing

    4.75mm

    19

    19

    1.9

    98.1

    90 100

    2.36mm

    17

    36

    3.6

    96.4

    85 -100

    1.18mm

    140

    176

    17.6

    82.4

    75 100

    600µ

    158

    334

    33.4

    66.6

    60 -79

    300µ

    506

    840

    84.0

    16.0

    12 40

    150µ

    144

    985

    98.5

    1.5

    0 10

    Pan

    15

    1000

    100

    0

    0

    also exhibits a relatively high permeability and grain size distribution that allows the design engineer to use it in direct contact with impervious material. Bottom ash is used as concrete aggregate or for several other civil engineering applications where sand, gravel and crushed stone are used. The chemical and chemical composition of bottom ash are shown in Table-1 and Table -2 respectively

    Table- 1: The chemical composition of bottom ash

    Content (%)

    Cement

    Bottom ash

    SiO2

    20.5

    57.03

    Al2O3

    4.0

    22.86

    Fe2O3

    4.02

    7.05

    K2O

    0.8

    0.3

    CaO

    64.0

    1.03

    TiO2

    0.17

    SO3

    1.8

    6.15

    MgO

    1.2

    0.85

    Na2O

    4.29

    td>

    0.642-0.747

    Properties of Bottom ash

    Values

    Specific gravity

    2.30

    Bulk density( gm/cc)

    Maximum dry density (KN/m3)

    7.20

    Water absorption (%)

    14.10

    Aggregate impact value (%)

    18.25

    Aggregate crushing strength (%)

    19.30

    Aggregate abrasion value (%)

    30.12

    Table- 2: Physical properties of bottom ash

    Ordinary Portland cement of 43 Grade and having specific gravity 3.03 was used for the experimental work. The bulk density of Bottom-ash was 1.75 kg/m3, specific gravity and fineness modulus was found to be 2.73 and 4.66, respectively.

    Table-3: Sieve analysis of bottom-ash

    Sieve size

    Materials retained on

    each sieve in

    Cumulative mass in grams

    Cumulative % mass retained

    %

    passing

    Requirements as per IS 383- 1970

    % passing

    4.75mm

    194

    19.4

    19.4

    92.2

    90 100

    2.36mm

    101

    10.1

    29.5

    88.3

    85 -100

    1.18mm

    292

    29.2

    58.7

    76.3

    75 100

    600µ

    178

    17.8

    76.5

    66.6

    60 -79

    300µ

    109

    10.9

    87.4

    13.0

    12 40

    150µ

    18

    1.8

    89.2

    2.5

    0 10

    Pan

    108

    10.8

    100

    0

    0

    Table-3: Sieve analysis of natural sand

    The percentage of particles passing through various sieve were compared with natural sand and it was found to be similar (refer Table-3 and Table-4). Crushed angular aggregate with maximum grain size of 20 mm and downgraded having bulk density 1.38 kg/m3, specific gravity 2.82 and fineness modulus 8 was used

  3. EXPERIMENTAL STUDIES

In the present work M25, M20, M30 grade of concrete is considered for the experimental investigation. Fine aggregate fully replaced with 100% percentage of bottom ash (refer Figure-1 and Figure-2). Comparative result of workability and compressive strength of conventional concrete cube and bottom ash added concrete cube are reported.

Constant parameters:

Grade of concrete: M25, M20, M30

Size of specimen: 150mm×150mm×150mm

Variable parameters:

Bottom ash: fine aggregate is replaced with bottom ash in different grade of concrete.

Curing period: 7days, 14days, 28days and 56 days

Figure-1: Bottom-ash

Figure- 2: Bottom-ash of different grading

    1. COMPRESSIVE STRENGTH

      The specimen of standard cube of (150 mm x150 mm x 150 mm) was used to determine the compressive strength of concrete. Three specimens were tested for 7, 14, 28 and 56 days with varying proportion of bottom-ash replacement. The constituents were weighed and the materials were mixed in a mixer. The mixes were compacted with the help of tamping rod. The specimens were de-molded after 24h, cured in water for 7, 14, 28 and 56 days and then tested for its compressive strength as per Indian Standards. The compressive strength test on cubes in the CTM machine is conducted as shown in Figure-3

    2. RESULTS AND DISCUSSIONS

      Table-4: Compressive Strength for M20 grade

      Age

      0%

      Bottom-ash (N/mm2)

      100%

      Bottom-ash (N/mm2)

      %

      Strength variation

      7 days

      14

      18

      28.57

      14 days

      16

      21

      31.25

      28 days

      20

      22

      10.00

      56days

      24

      26

      8.33

      Age

      0%

      Bottom-ash ( N/mm2)

      100%

      Bottom-ash (N/mm2)

      %

      Strength variation

      7 days

      17

      20

      17.65

      14 days

      21

      23

      9.52

      28 days

      24

      26

      8.33

      56days

      27

      30

      11.11

      Table-5: Compressive Strength for M25 grade

      Table-6: Compressive Strength for M30 grade

      Age

      0%

      Bottom-ash (N/mm2)

      100%

      Bottom-ash (N/mm2)

      %

      Strength variation

      7 days

      20

      23

      15.0

      14 days

      24

      28

      16.67

      28 days

      31

      33

      6.45

      56days

      37

      37

      0.0

      COMPRESSIVE STRENGTH IN N/mm2

      From the results obtained it can be seen there is not more than 28.57% increase in the compressive strength in 100% fine aggregate replaced concrete in case of M20 grade concrete at 7days.Similarly it can be observed that in no case the strength of bottom ash concrete cubes has fallen below the control sample (0% ash concrete cubes).In case of strength attainment over the age of 56days in case of bottom ash concrete cubes, it is lower than that of 0% bottom ash concrete cubes. In case of M30 it can be seen that the strength attained at the age of 56days by both type of cubes is same. Even the early strength of concrete with 100% ash concrete cubes i.e at 7days is between 40% to 55% and is better than that of no bottom ash concrete (15% to 40%)

      30

      25

      20

      15

      10

      5

      0

      7

      14

      28

      56

      NO.OF DAYS

      0% B.A 100%B.A

      Chart-1: Comparison of compressive strength

      M20 concrete

      35

      30

      25

      20

      15

      10

      5

      0

      CONCLUSIONS

      COMPRESSIVE STRENGTH IN N/mm2

      From the results it is concluded that the Bottom Ash can be used as a replacement for fine aggregate. The results prove that the replacement of 100% of fine aggregate by Bottom Ash induced higher compressive strength. Thus the environmental effects, illegal extraction of sand and cost of fine aggregate can be significantly reduced. By keeping in mind the acute shortage of river sand, heavy short coming on quality of river sand, high cost, greater impact on road damages and environmental effects. Thus the construction industry shall start using the bottom-ash to full extent as an alternative and reduce the impacts on environment by not using river sand.

      7

      14

      28

      56

      NO.OF DAYS

      0% B.A 100%B.A

      COMPRESSIVE STRENGTH IN

      N/MM2

      Chart-2: Comparison of compressive strength M25 concrete

      40

      35

      30

      25

      20

      15

      10

      5

      0

      7

      14

      28

      56

      NO.OF DAYS

      0% B.A 100%B.A

      Chart-3: Comparison of compressive strength

      COMPRESSIVE STRENGTH IN N/MM2

      M30 concrete

      40

      35

      30

      25

      20

      15

      10

      5

      0

      7

      14

      28

      56

      NO.OF DAYS

      M20 M25 M30

      Chart-3: Comparison of compressive strength

      M20,M25 and M30 concrete

      REFERENCES

      1. Mohd Syahrul Hisyam bin Mohd Sani, Fadhluhartini bt Muftah and Zulkifli Muda, The Properties of Special Concrete Using Wshed Bottom Ash (WBA) as Partial Sand Replacement, International Journal of Sustainable Construction Engineering & Technology (IJSCET), ISSN: 2180-3242, Volume 1, No. 2, December 2010, pp.65-76

      2. M. Purushothaman and R.M. Senthamarai, Strength Properties of High Performance Concrete using Bottom Ash as Fine Aggregate, International Journal of Civil Engineering (IJCE), ISSN 2278-9987, Volume 2, Issue 3,

        July 2013, pp.35-40

      3. P. Tang, Q.L. Yu, R. Yu and H.J.H. Brouwers, The application of MSWI bottom ash fines in high performance concrete, 1st International Conference on the Chemistry of Construction Materials, Berlin, October 2013, pp.435-438

      4. M.P. Kadam and Y.D. Patil, Effect of Coal Bottom Ash as Sand Replacement on the properties of Concrete with different W/C ratio, International Journal of Advanced Technology in Civil Engineering, ISSN: 2231-5721, Volume 2, Issue 1, 2013, pp.45-50

      5. K. Soman, Divya Sasi and K.A. Abubaker, Strength properties of concrete with partial replacement of sand by bottom ash, International Journal of Innovative Research in Advanced Engineering (IJIRAE), ISSN: 2349-2163, Volume 1, Issue 7, August 2014, pp.223-227.

      6. Remya Raju, Mathews M. Paul and K. A. Aboobacker, Strength Performance of Concrete using Bottom Ash as Fine Aggregate, International Journal of Research in Engineering & Technology (IJRET), ISSN (e): 2321-8843, ISSN (p): 2347-4599, Volume 2, Issue 9, September 2014, pp.111-122.

BIOGRAPHY

Dr R.G.Dsouza is currently the Principal at Yenepoya Institute of Technology,Moodabidri,Karnataka, India. He obtained his B.E. in Civil Engineering and M.Tech in Structural Engineering from M.I.T.Manipal. He obtained his Ph.D in Civil Engineering from NITK Surathkal

One thought on “Replacement of Fine Aggregate with Bottom Ash in Concrete and Investigation on Compressive Strength

  1. Vijayan says:

    Good one. as replacement of bottom ash is good for reducing the usage of natural resources whether it is sand or M-sand. Also use of Bottom ash also reduce the dumping of it in land.

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