Chloride Ion Penetration of High Strength High Performance Concrete

Jeenu G. Dept. of Civil Engineering

College of Engineering Trivandrum, India

P. Vinod Dept. of Civil Engineering

College of Engineering Trivandrum, India

Lalu Mangal Dept. of Civil Engineering

T.K.M. College of Engineering Kollam, India

Abstract-High strength high performance concrete (HPC) represents an important technological innovation which promises to unleash the full potential of the raw materials to produce an ecological concrete for the construction industry. This paper focusses on the chloride ion permeability of HPC mixes with strength greater than 75 N/mm2. The influence of mineral and chemical admixtures on the strength development and chloride ion permeability of high strength HPC is also studied. The investigated mixes were proportioned with aggregates designed for maximum density, using packing density method. The results indicate that unique combinations of micro silica and superplasticiser exist for HPC mixes with negligible to very low chloride ion permeability. Equation for predicting 6 hour conductivity from 1 hour conductivity is also proposed. Keywords- Chloride ion permeability, Durability, HPC, RCPT

I. INTRODUCTION The developments in construction industry demand

concretes with high flowability in the fresh state and enhanced properties in the hardened state. The strive for this led to the development of high strength high performance varieties of concrete, which effectively utilises raw materials to achieve high strength and durability, in addition to enhanced rheological characteristics [1]. Reduced porosity and micro cracks, and improved homogeneity in concrete and the transition zone in high performance concretes (HPC) has been achieved by using superplasticizers (SP) and supplementary cementitious materials (SCMs) such as fly ash, ground granulated blast-furnace slag, silica fume and metakaolin as part of binders. The potential ability of SCMs to enhance the properties and performance of concrete through their filler effect as well as pozzolanic reaction is utilised. Most of these materials are industrial by-products; hence, their inclusion in HPC could serve as an effective means of disposal and helps in producing cost effective, energy efficient and green concrete [2, 3].

One of the main problems in concrete structures is diffusion of chloride into concrete resulting in corrosion of reinforcement. Hence, the assessment of the rate of ingress of chlorides has become very important for assessing the long-term performance of concrete structures [4, 5]. Concrete can be considered an electrolytic conductor as the pore fluid transports current through it. The quantity of current passing through the concrete specimen will depend on the porosity and continuity of the pore system in addition to composition and mobility of ions present in the pore fluid [6]. Both resistivity and conductivity are useful for assessing the quality of concretes, related to durability [4] and Rapid Chloride

Permeability Test (RCPT) has been widely used to assess the permeability characteristics of concrete.

The mechanism of electrical conductivity in concrete is through cement pastes due to the infinitely large electrical resistivity of aggregates [7]. Several studies have concluded that the introduction of aggregate increases the diffusivity of chlorides mainly because of the interface effect [8, 9]. Some SCMs, such as silica fume and metakaolin have a significant impact on the ability of concrete to resist the penetration of chloride ions. The inclusion of such SCMs results in refined pore structure, reduced permeability and ionic diffusivity. It also alters the composition of the paste and thereby, the chloride binding capacity of the hydrated phases [10, 11]. SCMs also have a very significant effect on the pore solution chemistry of concrete, depending on the dosage and composition. Further, SCMs with low alkali content will incorporate more alkalis into hydration products than they release to the pore solution, lowering the pH value of the pore solution down to a safe level to suppress alkali-aggregate expansion of concrete [12, 13]. However, in most of the mix design procedures the proportioning of mineral admixtures is based on trial and error. In addition, it has been observed that the addition of mineral admixtures in conjunction with SP such as high range water reducers has very complicated effects, which may be either beneficial or detrimental to the fresh and hardened properties of concrete.

During the RCPT, the temperature in the solution and concrete specimen increases due to the flow of electric current generated by the relatively high-applied voltage (Joule effect). Since electrical conductivity is sensitive to temperature, heating will result in higher quantity of charge passed. To overcome this problem in RCPT, some researchers have proposed to run the test for a shorter duration to reduce or eliminate the heating effect and tried to correlate between 30-minutes conductivity or even 1-minute conductivity and the total charge [4].

II. RESEARCH SIGNIFICANCE

The degradation of the built environment is of enormous economic and technical importance as a major share of expenditure in the construction industry is spent on repair, maintenance and remediation. Hence, the performance characteristics and quality of infrastructure is of fundamental importance to the sustainability of the environment [14]. Chloride induced corrosion is one of the main durability problem in concrete structures. A critical review of various factors affecting chloride ion permeability of HPC revealed

978-1-4673-2636-0/12/$31.00 ©2012 IEEE 124

that chloride induced corrosion in concrete can be minimized if interconnected porosity is minimized at the early stages itself, which can be achieved by densifying the aggregate skeleton as well as the matrix. Also, wide variation in the effect of aggregate inclusion on chloride ion penetration of concrete is reported in the literature. Hence, there is a need to investigate the effect of dense packing of aggregates in chloride ion penetration on HPC. The combined effect of SCM and SP addition on the chloride ion penetration of HPC is also worth studying.

The main objective of the work discussed herein is to investigate the electrical conductivity of flowable high strength high performance concrete. The effect of dense aggregate gradation and the combined effect of micro silica (MS) and SP on the densification of the matrix and the resulting strength and chloride ion permeability is investigated. By the analysis of the results of RCPT at various intervals, the correlation between 1 minute, 30 minutes and one-hour conductivity with six-hour conductivity is also attempted.

III. MATERIALS AND METHODS

A. Materials Crushed quartz aggregates of angular shape and rough

texture with maximum size 20 mm and natural river sand (size < 4.75 mm) with specific gravity and fineness modulus 2.55 and 2.64 respectively were used for the study. Ordinary Portland cement (53 grade) was used for the entire experimentation. MS in the powdered form and polycarboxylate ether based SP (high range water-reducing admixture) with solid content 42% and specific gravity 1.1 were used.

The particle size distribution characteristics of cement and micro silica determined using Laser particle size analyzer are presented in Fig.1. The chemical composition of the cementitious materials is tabulated in Table 1.

Fig. 1. Particle size distribution curves for cement and micro silica

TABLE 1. CHEMICAL COMPOSITION OF CEMENTITIOUS MATERIALS (IN PERCENTAGE)

Compounds Cement Micro Silica

Silica (SiO2) 18.10 98.12

Calcium Oxide (CaO) 60.30 0.053

Iron Oxide (Fe2O3) 4.90 0.52

Aluminium Oxide (Al2O3) 4.54 0.29

Titanium Dioxide (TiO2) 0.27 0.17

Magnesium Oxide (MgO) 0.68 0.15

Potassium Oxide (K2O) 0.57 -

Sulphur Trioxide (SO3) 3.59 -

Sodium Oxide (Na2O) 0.20 -

B. Packing density determination and aggregate gradation To achieve the most effective particle size distribution

characteristics that would yield the densest gradation, packing density method of aggregate grading was adopted. Different aggregate combinations were designed by separating the aggregates into different fractions and by varying the percentage of individual fractions. From the packing density values of different combinations, the combination with coarse and fine aggregates in the ratio 0.58: 0.42 (with packing density 0.7951) was chosen for further investigation.

C. Mixture proportioning The objective of the investigation was to prepare flowable

high strength HPC with low absorption characteristics. Accordingly, trial mixes were made using different mix proportions and from the trial mixes which yielded a compressive strength of 75 N/mm2, the cement content of 450, 525 and 600 kg/m3 and a water-cement ratio of 0.23 were selected for further investigation. For the selected values of cement content and water cement ratio, different series of mixes with MS dosages of 0, 5, 10, 15, 20 and 25% by weight of cement were proportioned by absolute volume method. In each series, eight mixes were proportioned by varying the SP dosage from 0 to 3.5% in steps of 0.5%. From the trial mixes, only flowable mixes were considered for further investigation. The mixes were designated as M followed by the cement content, water-cement ratio and the percentages of MS and SP (Table 2).

D. Test procedure The ability to resist chloride penetration was assessed by

RCPT as per ASTM C1202-12 [15]. The test measures chloride ion migration or the electrical conductance of concrete. In this method, a potential difference of 60 V DC is maintained across the ends of 100 mm diameter 50 mm thick slices of a concrete cylinder, one side of which is immersed in a sodium chloride solution, the other in a sodium hydroxide solution. The amount of electrical current passing through the concrete during a six-hour period is measured at regular intervals. The compressive strength of the developed mixes was also determined according to ASTM C39-12 [16].

0

10

20

30

40

50

60

70

80

90

100

0.01 0.10 1.00 10.00 100.00

Perc

enta

ge p

assi

ng

Particle size (microns)

Cement

Microsilica

125

IV. RESULTS AND DISCUSSION

A. RCPT Values Typical values of the current passed through the specimen,

conductivity of the concrete and quantity of charge passed (Q) through the specimen after 1 minute, 30 minutes, 1 hour and six hours of the test are tabulated in Table 2. It is observed that very small quantity of current passed through the specimens and consequently, the charge passed through the specimen was less than 400 C for all the investigated mixes. Comparable values have been reported by Julio-Betancourt and Hooton, 2004 [4]. For flowable concretes with 10% silica fume, values of charge passed have been reported to lie in the range from 375 to 1118 C [17]. The negligibly low values of chloride ion penetrability of the investigated mixes indicate very high durability. The conductivity values of the investigated specimens ranged between 106.1 µs/cm and 1485.4 µs/cm, which are indicative of the highly reduced interconnected pore structure.

B. Influence of Particle Packing Assessment of the packing density of various aggregate

combinations for 20mm aggregates revealed that one with coarse and fine aggregates in the ratio 0.58: 0.42 exhibited maximum packing density of 0.7951. The coarser aggregate particles would form a skeleton, the intermediate pore spaces being filled with finer materials resulting in dense packing. The very high solid concentration of the aggregate skeleton would have ensured low porosity of the concrete mixes. The pore spaces between the finest fractions of aggregates would have been successively filled by cement and MS. From fig.1, it is observed that the average particle size of cement is about 30 microns (size range being 1 to 150 microns) and that of micro silica is less than 10 microns (size range being 1 to 20 microns). Hence, even the finest pores would have been filled with MS. The shape effect of MS might have also aided in the reduction of pore spaces and consequently the interconnectivity of pores.

C. Influence of Cement Content

Fig. 2. Typical variation of electrical conductivity with cement content

(SP= 2%)

Variation of electrical conductivity with cement content for different MS dosages is illustrated in fig. 2. The mixes with cement content 450 kg/m3 with MS dosages 10 to 15% and 525 kg/m3 with MS dosage 5 to 15% registered negligible chloride ion permeability (Q <100). For low cement contents, i.e., 450 kg/m3, MS dosages of 5% may not be sufficient for full pozzolanic activity and hence may have resulted in higher pore spaces and very low permeability (Q >100). All the mixes with cement content 600 kg/m3 exhibited very low permeability. At higher cement contents, the excess powder may have caused repulsion of particles, which would have ultimately resulted in unpacking of the fine fillers leading to larger number of pores and more interconnected porosity. Hence, in order to proportion HPC mixes with negligible permeability, cement content of 450 to 525 kg/m3 is suggested.

D. Influence of MS Addition The addition of MS decreases the chloride ion permeability

of all the investigated mixes by filler effect and pozzolanic activity. The SiO2 content of MS used for the investigation was higher than 98% (Table 1), which may have ensured high pozzolanicity. For all the cement contents, MS dosages of 10 and 15% yielded mixes with least chloride ion penetration (Fig. 2 and Fig. 3). MS dosage of 5% seems to be insufficient for the complete pore filling as well as pozzolanic action, as the mixes with 5% MS exhibited higher Coulomb values. The electrical conductivity registered a maximum for mixes with 20% MS and it increases with increase in cement content (Fig. 2). The adverse influence of very high powder content is evident from this increase in the conductivity values. For developing HPC with negligible permeability, for any cement content, MS dosage of 10 to 15% is recommended.

E. Influence of SP Addition The addition of SP improves the rheological properties of

HPC by its dispersive effect as well as steric action. This improvement in rheology would have resulted in better packing and compaction of concrete and consequently, low permeability. From Fig. 3, it is observed that as SP dosages increases, there is a reduction in chloride permeability until a

Fig. 3 . Typical variation of charge passed with MS dosage

(Cement content = 600 kg/m3)

0

50

100

150

200

250

400 450 500 550 600 650

Cha

rge p

asse

d (C

)

Cement content (kg)

MS=5%

MS=10%

MS=15%

MS=20%0

50

100

150

200

250

300

350

400

450

0 5 10 15 20 25

Cha

rge p

asse

d (C

)

MS dosage (%)

SP=1% SP=1.5%SP=2% SP=3%SP=2.5% SP=3.5%

126

dosage of 2.5% is reached. Lower SP dosages (1.0 and 1.5%) might not be sufficient for the proper dispersion of cementitious materials and might have resulted in agglomeration of these particles and consequent flocculation. The higher dosages (>3%) would have over dispersed the fine materials resulting in increased space between particles beyond the optimum for proper reactions to take place. For all cement contents and MS dosages, optimum SP dosage for least chloride ion permeability in HPC is about 2.5%.

For proportioning high strength HPC with low permeability characteristics, cement content of 450 to 525 kg/m3 with MS dosage of 10 to 15% and SP dosage of about 2.5% is suggested.

F. Conductivity at Different Stages of RCPT According to McGrath and Hooton (1999), the RCPT is a

measure of conductivity and that there is no need to extend the test time beyond the period necessary to overcome initial polarisation (likely a few minutes). By using the 30-min value of charge passed and multiplying by 12, a RCPT value is obtained before significant heating can occur. The 1-min conductivity was also found to be very helpful in understanding the ideal behaviour of concrete tested using the RCPT when the effect of temperature in the pore fluid and microstructure are not considered [4].

Typical correlation between 1-minute conductivity and 6- hour conductivity is shown in fig. 4. The poor correlation of the conductivities may be due to extremely low conductivity during the initial one minute of the test (current passed through the specimens ranged between 0.001 A to 0.008 A [Table 2]). From Fig. 5, it is observed that 30 minutes conductivity has better correlation with 6 hours conductivity. However, multiplying the charge passed through specimens at the end of 30 minutes by 12, 6-hour conductivity could not be established as the initial conductivity is very small. From Table 2, it is observed that though the initial polarisation is over at very early stages itself, one-minute or 30-minute conductivity would not give a clear estimate of the final conductivity in the investigated mixes. Further, it is noticed that some mixes having zero initial conductivity exhibited negligible permeability at the later stages.

Fig. 4. Typical correlations between conductivities at 1 minute

and 6 hours (cement content =450 kg/m3)

Fig. 5. Typical correlations between conductivities at 30 minutes and 6 hours

(cement content =450 kg/m3)

This extremely low electrical conductivity during the early hours of the test can be attributed to very low interconnected porosity in the investigated mixes. The pozzolanic activity of highly reactive micro silica would have filled the pore spaces during the early ages itself and this may have reduced the interconnected porosity.

Hence, correlation is established between 1-hour conductivity and 6-hour conductivity, considering RCPT values of all the investigated mixes (Fig. 6). The regression analyses of the data resulted in the following equation with satisfactory values of correlation coefficient (0.99).

Q6hrs = 5.81 Q1hr +16.73 (1) Since the mean and the standard deviation of the ratio of

predicted values and corresponding observed values are 1.00 and 0.05 respectively, Equation (1) can be considered acceptable for predicting 6-hour conductivity. This equation takes into consideration the condition when RCPT does not record any current passing through the specimen during the initial hours of the test.

Fig. 6. Correlation between conductivities at 1 hour and 6 hours

y = 379.4x + 42.58R² = 0.79

0

50

100

150

200

250

0 0.1 0.2 0.3 0.4 0.5

Cha

rge p

asse

d in

in 6

hou

rs (C

)

Charge passed in 1 minute (C)

y = 27.58x + 29.12R² = 0.829

0

50

100

150

200

250

0 1 2 3 4 5 6 7

Cha

rge p

asse

d in

6 h

ours

(C)

Charge passed in 30 minutes (C)

30 minQ30* 12

y = 5.81x + 16.73R² = 0.99

0

50

100

150

200

250

300

350

400

0 10 20 30 40 50 60 70

Cha

rge p

asse

d in

6 h

ours

(C)

Charge passed in 60 min (C)

C=450C=525C=600

127

From the RCPT results, it can be suggested that for high strength high performance mixes, the 6-hour conductivity can roughly be estimated as the 1-hour conductivity multiplied by 6.3265.

G. Correlation between strength and RCPT values The HPC mixes developed for the present investigation

with negligible (Q < 100 C) to very low permeability (Q < 1000 C), exhibited high compressive strength. However, there is no correlation between strength and the values of total charge passed. It is also observed that the mixes with highest value of 3-day compressive strength in each series of MS addition exhibited the least chloride ion permeability (Tables 2). The early hydration as well as the pozzolanic action which is responsible for early strength development in these mixes may have also contributed to the reduction in pore structure and interconnected porosity.

V. CONCLUSIONS

The following conclusions are drawn based on the results of the present study:

• Dense aggregate packing, further densified by the complex action of mineral and chemical admixtures aid in the development of HPC with very early strength and low permeability characteristics.

• For proportioning high strength HPC with very high strength as well as negligible to very low chloride ion permeability, cement content 450 to 525 kg/m3, MS dosages of 10 to 15% with SP dosages in the range of 2 to 2.5% is suggested.

• One or 30 minutes conductivity cannot be used to predict the 6-hour conductivity in high strength HPC. The equation for predicting 6-hour conductivity from 1-hour conductivity for high strength HPC is proposed. It is suggested that the 6-hour conductivity of high strength HPC can roughly be estimated as the 1-hour conductivity multiplied by 6.3265

• There is no correlation between strength and chloride ion permeability. However, the mixes with high early strength exhibited least value of chloride ion penetration.

ACKNOWLEDGEMENT Authors express their gratitude to the Kerala State Council

for Science, Technology and Environment (KSCSTE), Government of Kerala, India, for funding this study, which is part of the sponsored research project on “Investigations on Ultra High Performance Cementitious Composites”.

REFERENCES [1] P.C. Aitcin, “The durability characteristics of high performane

concrete : a review”, Cement and Concrete Composites, 24(4), 2003, pp.409-420.

[2] M.J. Shannag , “ High strength concrete containing natural pozzolan and silica fume”, Cement and Concrete Composites, 22(4), 2000, pp.399-406.

[3] M.A. Megat Johari , J.J. Brooks, S. Kabir and P. Rivard , “ Influence of supplementary cementitious materials on engineering properties of high strength concrete” Construction and Building Materials, 25, 2011, pp.2639–2648.

[4] A. Julio-Betancourt and R.D. Hooton, “ Study of the Joule effect on rapid chloride permeability values and evaluation of related electrical properties of concrete”, Cement and Concrete Research, 34, 2004, pp.1007–1015.

[5] G.S.M. Ahmed, O. Kayali and W. Anderson,” Chloride penetration in binary and ternary blended cement concretes as measured by two different rapid methods”, Cement and Concrete Composites, 2008, 30, pp. 576–582.

[6] K. Stanish, R.D. Hooton and M.D.A. Thomas, A novel method for describing chloride ion transport due to an electrical gradient in concrete: Part 1. Theoretical description, Cement and Concrete Research, 34, 2004, pp. 43–49.

[7] T.H. Wee, A.K. Suryavanshi and S.S. Tin, “ Influence of aggregate fraction in the mix on reliability of the rapid chloride permeability test”, Cement and concrete composites, 21 (1), 1999, pp. 59-72

[8] P. Halamickova, R. J. Detwiler, D. P. Bentz and E. J. Garboczi, “Water permeability and Chloride Ion Diffusion in Portland Cement Mortars: Relationship to Sand Content and Critical Pore Diameter”, Cement and Concrete Research, 25(4), 1995, pp.790-802, 1995.

[9] A.H. Asbridge, G. A. Chadbourn and C. L. Page, “Effects of Metakaoline and the Interfacial Transition Zone on the Diffusion of Chloride Ions Through Cement Mortars”, Cement and Concrete Research, 31(11), 2001, pp.1567-1572.

[10] C.C. Yang, S.W. Cho and R. Huang, “The relationship between charge passed and the chloride-ion concentration in concrete using steady-state chloride migration test”, Cement and Concrete Research, 32 ,2002, 217–222.

[11] M.D.A. Thomas, R.D. Hooton, A. Scott c,H. Zibara, “The effect of supplementary cementitious materials on chloride binding in hardened cement paste” Cement and Concrete Research, 2011

[12] Shi, “Strength, Pore Structure and Permeability of High Performance Alkali-Activated Slag Mortars, Cement and Concrete Research”, 26 (12),1996, pp.1789-1800.

[13] M. H. Zhang, A. Bilodeau, V. M. Malhotra, K. S. Kim and J. C. Kim, “Concrete Incorporating Supplementary Cementing Materials: Effect on Compressive Strength and Resistance to Chloride-Ion Penetration”, 96 (2),1999, pp.181-189.

[14] E Long, P.A.M Basheer, S.E. Taylor and J.Kirkpatrick, “Sustainable concrete structures through innovative research and development”, Concrete Platform 2007.

[15] ASTM C1202 – 12: Standard test method for Electtrical Indication of Concrete’s ability to resist Chloride Ion Penetration.

[16] ASTM C39-12: Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens.

[17] M. Gesoglu, E. Guneyisi and E. Ozbay, “Properties of self-compacting concretes made with binary,ternary, and quaternary cementitious blends of fly ash, blast furnace slag and silica fume”, Construction and Building Materials, 23(5), 2009, pp. 1847-1854.

128

TAB

LE 2

RC

PT T

EST

RES

ULT

S A

ND

CO

MPR

ESSI

VE

STR

ENG

TH O

F TH

E IN

VES

TIG

ATE

D M

IXES

Mix

des

igna

tion

Cur

rent

pas

sed

(A)

Con

duct

ivity

(µs/

cm)

Cha

rge

pass

ed (C

) Pe

rmea

bilit

y cl

assi

ficat

ion

Com

pres

sive

stre

ngth

(N

/mm

2 )

1 m

in

30 m

in

1 hr

6h

rs

1 m

in

30 m

in

1 hr

6h

rs

1 m

in

30 m

in

1 hr

6h

rs

3 da

ys

28 d

ays

M-4

50-0

.23-

5-1.

0 0.

006

0.00

6 0.

006

0.00

9 63

6.6

636.

6 63

6.6

954.

9 0.

36

5.4

21.6

14

8.5

Ver

y Lo

w

65.0

98

.0

M-4

50-0

.23-

5-1.

5 0.

003

0.00

3 0.

004

0.00

7 31

8.3

318.

3 42

4.4

742.

7 0.

18

2.7

11.7

11

1.6

Ver

y Lo

w

52.0

95

.0

M-4

50-0

.23-

5-2.

0 0.

004

0.00

4 0.

005

0.00

7 42

4.4

424.

4 53

0.5

742.

7 0.

24

3.60

15

.3

130.

5 V

ery

Low

54

.5

97.5

M-4

50-0

.23-

5-2.

5 0.

003

0.00

3 0.

004

0.00

5 31

8.3

318.

3 42

4.4

530.

5 0.

18

2.70

11

.7

100.

8 V

ery

Low

71

.0

95.0

M-4

50-0

.23-

5-3.

0 0.

004

0.00

5 0.

006

0.00

6 42

4.4

530.

5 63

6.6

636.

6 0.

24

4.05

18

.0

126.

0 V

ery

Low

62

.5

81.0

M-4

50-0

.23-

5-3.

5 0.

003

0.00

4 0.

005

0.00

8 31

8.3

424.

4 53

0.5

848.

8 0.

18

3.15

14

.4

125.

1 V

ery

Low

47

.0

80.5

M-4

50-0

.23-

10-1

.0

0.00

3 0.

004

0.00

5 0.

008

318.

3 42

4.4

530.

5 84

8.8

0.18

3.

15

14.4

13

2.3

Ver

y Lo

w

57.0

97

.0

M-4

50-0

.23-

10-1

.5

0.00

1 0.

001

0.00

1 0.

001

106.

1 10

6.1

106.

1 10

6.1

0.06

0.

90

3.6

21.6

N

eglig

ible

50

.0

101.

0

M-4

50-0

.23-

10-2

.0

0.00

1 0.

002

0.00

2 0.

005

106.

1 21

2.2

212.

2 53

0.5

0.06

1.

35

6.3

68.4

N

eglig

ible

65

.0

100.

0

M-4

50-0

.23-

10-2

.5

0.00

1 0.

002

0.00

2 0.

004

106.

1 21

2.2

212.

2 42

4.4

0.06

1.

35

6.3

47.7

N

eglig

ible

62

.5

97.0

M-4

50-0

.23-

10-3

.0

0.00

3 0.

003

0.00

5 0.

008

265.

3 31

8.3

530.

5 84

8.8

0.15

2.

48

12.2

12

2.9

Ver

y Lo

w

85.0

98

.0

M-4

50-0

.23-

10-3

.5

0.00

4 0.

005

0.00

5 0.

006

424.

4 53

0.5

530.

5 63

6.6

0.24

4.

05

17.1

12

4.2

Ver

y Lo

w

47.6

88

.5

M-4

50-0

.23-

15-1

.0

0.00

7 0.

007

0.00

8 0.

014

742.

7 74

2.7

848.

8 14

85.4

0.

42

6.30

26

.1

234.

9 V

ery

Low

53

.0

102.

0

M-4

50-0

.23-

15-1

.5

0.00

7 0.

007

0.00

7 0.

011

742.

7 74

2.7

742.

7 11

67.1

0.

42

6.30

25

.2

198.

0 V

ery

Low

55

.0

102.

0

M-4

50-0

.23-

15-2

.0

0.00

4 0.

005

0.00

6 0.

007

424.

4 53

0.5

636.

6 74

2.7

0.24

4.

05

18.0

14

3.1

Ver

y Lo

w

67.5

83

.5

M-4

50-0

.23-

15-2

.5

0.00

4 0.

004

0.00

4 0.

005

424.

4 42

4.4

424.

4 53

0.5

0.24

3.

60

14.4

92

.7

Neg

ligib

le

72.5

10

8.0

M-4

50-0

.23-

15-3

.0

0.00

4 0.

004

0.00

5 0.

006

424.

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