Splitting Tensile Strength of Ternary Blended Concrete Containing Phosphogypsum and Silica Fume

Splitting Tensile Strength of Ternary Blended Concrete Containing Phosphogypsum and Silica Fume

Leena V P

Department of civil Engineering Musaliar College of Engineering and Technology,

Pathanamthitta, Kerala, India

Subhalekshmi

Bismi M Buhari

Department of civil Engineering Musaliar College of Engineering and Technology,

Pathanamthitta, Kerala, India

Department of civil Engineering Musaliar College of Engineering and Technology,

Pathanamthitta, Kerala, India

Abstract – Phosphogypsum is the second largest waste material produced in the World. It contained small quantities of silica, fluorine and phosphate as impurities. These impair the strength development of calcined products. Because of the reason phosphogypsum can be effectively used in cement replacement. 10% Silica fume and 5-15% of phopshogypsum by weight of cement are used for this investigation

Keywords – phosphogypsum; calcined product; silica fume

1. INTRODUCTION

   Ordinary concrete has a single cementitious material i.e. cement. Binary blend of concrete includes cement as the binding material and a pozzolanic material being added. Ternary blended concrete marks the inclusion of two different pozzolanic materials to the concrete with cement acting as the primary binding material. Durability of concrete is increased by the reduction of Calcium Hydroxide content which causes Sulphate Attack. Fly ash from coal fired power plants and metakaolin are both important in modern concrete technology [2]. Enlarging the scope of material science to Supplementary Cementious Materials (SCM) viz., fly ash, slag, silica fume, rice husk ash and Metakaolin in the use of concrete, this led to the concept of blended cements and blended concretes. Thus impact during early hydration was reduction in generation of surplus Ca(OH)2, control of heat of hydration and mitigation of continuous bleed channels. So, reorienting the mix design for improved performance of concrete with thrust on, (a) Controlling OPC content but increasing the total cementitious material, (b) Controlling water content, using chemical admixture, for improved workability, for offsetting slow hydration with SCM. Thus the impermability was achieved. In India, about 6 million tons of waste gypsum such as phosphogypsum, flourogypsum etc., are being generated annually [3]. Phosphogypsum refers to the gypsum formed as a by-product of processing phosphate ore into fertilizer with sulfuric acid.

2. METHODOLOGY

   Phopshogypsum and silica fume was used as binding material along with cement. 10% silica fume is fixed for all mixes according to IS456-2000(clause-5.2.1.1) and IS 15388-2003 (code for silica fume specification)[10,11]. At first Control mix of M30 grade is prepared to get sufficient 28 day characteristic strength. Then different mixes are prepared by replacing cement with 10% silica fume and 0%, 5%, 7.5%,

   10%, 12.5%, 15% of phosphogypsum. Fresh properties of different mixes studied by slump test and compacting factor test. Then splitting tensile strength test is conducted for different mixes.

3. MATERIALS AND METHODS

Materials used are cement, fine aggregate, coarse aggregate, silica fume and phosphogypsum. All materials are tested as per standard procedures to assess their engineering properties and the results were compared with those in relevant IS codes.

TABLE I. PROPERTIES OF CEMENT

TABLE II. PROPERTIES OF FINE AGGREGATE

54.53%

TABLE III. PROPERTIES OF COARSE AGGREGATE

TABLE IV. MIX PROPORTION

TABLE V. QUANTITY OF MATERIALS USED

IV SPLITTING TENSILE STRENGTH TEST

The split tensile strength test is a well known indirect test used for determining the tensile strength of concrete. Test was carried out on concrete cylinder of size 150mm×300mm as per IS 5816:1999 specification. In split tensile strength test, concrete cylinder was placed with its axis horizontal, between the loading surface of a compression testing machine and the load was applied until the failure occurred due to a splitting in the plane, containing the vertical diameter of the specimen. In order to reduce the magnitude of high compression stress near the points of application of the load, narrow packing strips of plywood were placed between the specimen and loading plates of the testing machine. The split tensile strength was determined for various mixes after 28 day water curing. Figure

3.7 shows split tensile strength test on cylinder. The measured splitting tensile strength fc, of the specimen shall be calculated to the nearest 0.05 N/mm2 using the following ormula :

fp= 2p/ld

P = maximum load in N applied to the specimen.

l = length of the specimen (in mm), and

d = cross sectional dimension of the specimen (in mm). V TEST RESULTS

1. Control Mix

   In this study , replacement of cement by silica fume and phosphogypsum is done on M30 design mix. 7 and 28 day splitting tensile strength and flexural strength values of M30 is shown in table.

   TABLE VI. SPLITTING TENSILE STRENGTH VALUE OF M30

   	7 Day	28 Day
   Splitting tensile strength(N/mm²)	1.6	3.91

   5

   4

   3

   2

   1

   Spitting

   Tensile Strength ( N/mm²)

   5

   4

   3

   2

   1

   Spitting

   Tensile Strength ( N/mm²)

   0

   0

   7 day 28 day

   Age,day

   7 day 28 day

   Age,day

   Splitting tensile

   strength(N/MM2)

   Splitting tensile

   strength(N/MM2)

   Fig. 1. Splitting tensile strength values of M30.

2. Cement Replaced with 10% SF & 0% PG (PG0)

   10% cement in M30 mix is replaced with silica fume is selected as the first mix for study.

   Spliting tensile

   strength(N/mm2)

   Spliting tensile

   strength(N/mm2)

   TABLE VII. SPLITTING TENSILE STRENGTH VALUE OF PG0

   	7 Day	28 Day
   Splitting tensile strength(N/mm²)	1.85	4.15

   5

   4

   3

   2

   1

   PG0

   M30

   5

   4

   3

   2

   1

   PG0

   M30

   0

   0

   7 daAyge,da2y8 day

   7 daAyge,da2y8 day

   Fig. 2. Splitting tensile strength values of PG0

3. Cement Replaced with 10% SF & 5% PG (PG5)

   15% cement in M30 mix is replaced with 10% silica fume and 5% of phosphogypsum for study.

   TABLE VIII. SPLITTING TENSILE STRENGTH VALUE OF PG5

   	7 Day	28 Day
   Splitting tensile strength(N/mm²)	2.15	4.2

   5

   PG5 M30

   0

   7 dAayge,d2a8yday

   5

   PG5 M30

   0

   7 dAayge,d2a8yday

   Spliting

   tensile strength(N/

   Spliting

   tensile strength(N/

   Fig. 3. Splitting tensile strength values of PG5

   5

   5

   Spliting

   tensile strength(

   Spliting

   tensile strength(

4. Cement Replaced with 10% SF & 7.5% PG (PG7.5

   PG12.5

   PG12.5

   0

   0

   17.5% cement in M30 mix is replaced with 10% silica fume and 7.5% of phosphogypsum for study.

   M30

   M30

   7 day

   7 day

   28 day

   28 day

   TABLE IX. SPLITTING TENSILE STRENGTH VALUE OF PG7.5

   Age,day

   Age,day

   5

   Spliting tensile

   strength(N/mm2)

   Spliting tensile

   strength(N/mm2)

   4

   3

   2

   1

   0

   7 day 28 day

   Age,day

   PG7.5 M30

   Fig. 6. Splitting tensile strength values of PG12.5

   	7 Day	28 Day
   Splitting tensile strength(N/mm²)	2.1	4.29

   	7 Day	28 Day
   Splitting tensile strength(N/mm²)	2.1	4.29

   G. Cement Replaced with 15 % SF & 10% PG (PG 15)

   25% cement in M30 mix is replaced with 10% silica fume and 15% of phosphogypsum for study.

   TABLE XII. SPLITTING TENSILE STRENGTH VALUE OF PG15

   	7 Day	28 Day
   Splitting tensile strength(N/mm²)	1.00	3.75

   Spliting

   tensile strength(N

   Spliting

   tensile strength(N

   5

   PG15

   Fig. 4. Splitting tensile strength values of PG7.5

5. Cement Replaced with 10% SF & 10% PG (PG10)

   0

   7 dAayge,d2a8yday

   M30

   20% cement in M30 mix is replaced with 10% silica fume and 10% of phosphogypsum for study.

   Spliting tensile

   strength(N/mm2)

   Spliting tensile

   strength(N/mm2)

   TABLE X. SPLITTING TENSILE STRENGTH VALUE OF PG10

   	7 Day	28 Day
   Splitting tensile strength(N/mm²)	1.3	4.1

   5

   4

   3

   2

   PG10

   M30

   5

   4

   3

   2

   PG10

   M30

   Age,day

   Age,day

   1

   0

   1

   0

   7 day

   7 day

   28 day

   28 day

   Fig. 5. Splitting tensile strength values of PG10

6. Cement Replaced with 12.5 % SF & 10% PG (PG 12.5)

22.5% cement in M30 mix is replaced with 10% silica fume and 12.5% of phosphogypsum for study.

Fig. 7. Splitting tensile strength values of PG15

H. Comparison of Result

TABLE XIII. COMPARISON OF RESULTS

Figure shows the comparison of splitting tensile strength. 7 day and 28 day spitting tensile strength retain nearly constant ratio. 7 day strength is maximum at PG5 and

28 day strength is maximum at PG7.5. Above 7.5% phosphogypsum replacement along with 10% silica fume decreases the splitting tensile strength.

TABLE XI. S

PLITTING TENSILE STRENGTH VALUE OF PG12.5

Flexural strength(N/mm2)

Flexural strength(N/mm2)

12

10

8

6

4

2

0

Mix Designation

Fig. 8. Comparison of results

VI CONCLUSION

ACKNOWLEDGEMENT

I would like to express my personal thanks to all the support given from the college and also the second author for her continuous encouragement.

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   The present investigation had presented results of the

   experimental study to evaluate the suitability of utilizing phosphogypsum and silica fume as supplementary cementatious materials in ternary blended concret in M30 concrete.

   • The workability of ternary blended concrete containing silica fume and phosphogypsum decreased when percentage replacement increases. This is due to higher percentage of finer particles than 150 microns.

   • Splitting tensile strength and flexural strength were improved on the addition of phosphogypsum along with 10% silica fume.

   • Increasing amount of supplementary cementitious materials in concrete extent set time and slow

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