Development and characterization of hybrid polyethylene-fibre-reinforced cement composites

Development and characterization of hybrid polyethylene-fibre-reinforced cement composites Parviz Soroushian*,

Atef Tlili, Abdulrahman

Alhozaimy

and Ataullah

Khan

Civil Engineering Department, Michigan State University, Lansing, Michigan, USA Received and accepted 19 July 1993 The research reported here is concerned with optimizing the combined use of two different fibre types in cementitious matrices. The two fibre types were a high-modulus polyethylene fibre and a fibrillated polyethylene pulp. The effects of different volume fractions of the two fibres and their interaction on the impact resistance, flexural strength and toughness, compressive strength, bulk specific gravity, volume of permeable pores and water absorption capacity of cementitious materials manufactured with a highperformance mixer were investigated through a factorial experimental design. In the case of impact resistance, the positive effect of each fibre was pronounced in the presence of the other fibre type, For flexural strength and toughness, the combined use of polyethylene fibre and pulp produced desirable results as long as the amounts incorporated were below certain limits. The negative effects of fibres on compressive strength were less pronounced when the two fibre types were used in combination. The interactions between polyethylene fibre and pulp in deciding the specific gravity, volume of permeable pores and water absorption capacity of cementitious materials were either negligible or only moderately significant.

Keywords: cement compound composition; fibre-reinforced concretes; plastics, polymers and resins

Brittle failure is an inherent property of cementitious materials, and one way to overcome this problem is by using reinforcing fibres. Fibre-reinforced cement composites represent a class of cementitious materials generally constructed by adding short fibres of small crosssectional dimensions to the cementitious matrix. Closely spaced fibres (i.e. fibres with relatively small crosssectional dimensions) are capable of interfering with the propagation of microcracks that initiate from internal flaws in the material, forcing them to deflect and thus dissipate additional energy during propagation. This delays the formation of an unstable crack system and, thus, increases the tensile strength and toughness of the composite material. Upon the formation of macrocracks in the postpeak region under tensile stress systems, fibres tend to bridge the cracks and restrain their widening by providing pullout resistance. The pullout action of fibres dissipates frictional energy, and the bridging of cracks and dissipation of frictional energy by fibres lead to improvements in the postpeak ductility and toughness characteristics of cementitious materials. Considerable research has been conducted with fibrereinforced cement composites using one type of fibre within the cementitious matrix. Each fibre type tends to be more effective in improving certain aspects of the properties of cement-based materials. Potentials exist for

*Correspondence to Dr Parviz Soroushian

0950-0618/931040221-9© Butterworth-HeinemannLtd

achieving balanced improvements in the performance characteristics of cementitious materials through using different fibre types in combination. To use a combination of different fibre types successfully in cementitious matrices, due consideration should be given to the mix proportioning and manufacturing procedures to achieve a uniform dispersion of different types in the matrix. The research reported here is concerned with assessing the combined effects of two different polyethylene fibre types in cement-based matrices. The two polyethylene fibres used are a high-modulus polyethylene fibre I and fibrillated polyethylene pulp 2. The high-modulus polyethylene fibre is particularly effective in improving the toughness and ductility of cement-based materials, while the fibrillated polyethylene pulp can be effective in arresting microcracks in cementitious matrices under load, thereby increasing the tensile and flexural strengths of the composite material.

Research significance The research reported here explores the potentials for achieving balanced improvements in the performance characteristics of cement-based materials through the combined use of different fibre types. Such efforts potentially can lead to the development of fibrous cement composites that will provide superior performance under severe loading and environmental effects at reasonable costs.

Construction and Building Materials 1993 Volume 7 Number 4

221

Hybrid polyethylene-fibre-reinforced cement composites: P. Soroushian et al.

Fibre types

Table 1 Mix proportions*

High-modulus polyethylene fibre ~ The high-modulus polyethylene fibre used in this investigation has a tensile strength o f 375 ksi (2588 MPa), a Young's modulus of 17 000 ksi (117 300 MPa), an elongation at break ranging from 5% to 8%, a specific gravity of 0.97, a filament diameter of 0.0015 in (38 micrometres), and a length of 0.25 to 0.5 in (7 to 13 mm). It has a linear stress-strain curve up to failure. The combination of high tensile strength and modulus with a 0.97 specific gravity gives these high-modulus polyethylene fibres a higher specific tensile strength (tensile strength/ specific gravity) than other commercially available fibre typesL The specific modulus (modulus/specific gravity) of this high-modulus polyethylene fibre is comparable with those of other high-modulus fibres such as boron and graphite. High-modulus polyethylene fibre has desirable strength-retention properties under long-term exposure to aggressive environments (e.g. sea water, alkalis and acids) 1. The fibre also has reasonable thermal stability, retaining a high percentage of its room temperature properties at elevated temperatures of about 176°F (80°C). Its creep properties compare favourably with those of other organic fibres. In application to cement paste 3, the high-modulus polyethylene fibre is highly effective in increasing the flexural strength and toughness characteristics and impact resistance of the material.

Polyethylenepulp volume fraction (%)

Fibrillated polyethylene pulp 2 The fibrillated polyethylene pulp used in this investigation has a specific gravity of 0.91 to 0.97 and a diameter of 0.43 × 10 -3 to 8.5 x 10 -3 in (1 to 20 micrometres). It maintains 50% of its room temperature modulus at 212°F (100°C). Thin-sheet cement products incorporating fibrillated polyethylene pulp have been manufactured in the past using the slurry-dewatering processing technique. In this method, a dilute slurry of fibres and solids (cement and possibly fine aggregates) is prepared and then dewatered by applying a vacuum and pressing for compaction. Slurry-dewatered cement sheets reinforced with 3.9% and 7.4% mass fraction of fibrillated polyethylene pulp can reach flexurai strengths of 2.623 and 3.33 ksi (18.1 and 23.0 MPa), respectively; no specific durability problems have been reported for these composites ~.

Experimental programme The objective of this experimental study was to develop hybrid fibre-reinforced cement composites incorporating both the high-modulus polyethylene fibre and the fibrillated polyethylene pulp. Optimum combinations of these two fibres were decided (for the specific cementitious matrix and manufacturing technique considered in this investigation) based on the workability and fibre dispersability conditions in the fresh state and mechanical characteristics of the hardened composite. Uniform dispersion of fibres is vital to the development of cement composites which effectively take advantage of the reinforcement properties of fibres. A cellulose ether 4 was used to facilitate uniform fibre dispersion. The cellulose ether acts as a colloidal stabilizer and controls 222

Polyethylenefibre volumefraction (%) 0

0

4.5

9

w/bt sp/b~ Flow, % % air w/b* sp/b~ Flow, % % air w/bt sp/b~ Flow, % % air

0.1

0.207 0.2075 0.007 0.007 85 79 7.37 11 0.3 0.4092 0.0167 0.0175 70 64 9.42 8.50 0.410 0.4020 0.033 0.034 68 70 8.90 9.1

0.2 0.23 0.011 67 86 15.50 0.403 0.0183 65 10.61 0.405 0.035 51 14.3

0.3 0.2078 0.015 72 13.30 0.4003 0.0187 62 11.50 0.4456 0.0358 59 12.90

*Antifoamingagent was used (antifoam/binder = 0.002, by weight) *w/b = water/binder ratio, by weight ~sp/b = superplasticizer/binderratio, by weight

the rheology of the fresh mix. It is a water-soluble polymer that forms aqueous dispersions of swelling and hyperscenic hydration of its structural layers. In the cementitious mixtures of this study, 18% by weight of cement was also substituted with a fine pozzolan (silica fume) with a relatively small particle size to improve further the fibre dispersability of the matrix. When mixed with water, silica fume provides a cohesive mixture that is capable of attacking fibre balls and coating the individual fibres; the fibre-to-matrix interfacial bond strength also tends to be improved in the presence of silica fume (specific gravity = 2.26; average particle size = 0.8 micrometres (0.315 x 10 -6 in); SiO2 content = 90% to 95%) 5. Silica fume, as well as fibres, tends to decrease the workability of the fresh mix; a superplasticizeo with naphthalene formaldehyde sulfonate as the active ingredient was used to improve workability. Only fine aggregates (Grade 100 silica sand) were used in the matrix. Large aggregate particles, which increase the tendency toward fibre balling, were avoided. The matrix mix proportions and fibre reinforcement conditions considered in this investigation are given in Table 1. The matrix consists of a fast-setting cement 6, silica fume, and cellulose ether. The fast-setting cement was used to overcome the problems with prolonged setting time observed in the presence of fibrillated polyethylene pulp for the mix proportions and manufacturing procedures considered in this investigation. The water/ binder (w/b) and superplasticizer/binder (sp/b) ratios presented in Table 1 were selected to produce a constant flow (ASTM C 230) of 65% to 85%. The term 'binder' refers to the combination of cement and silica fume, and all ratios presented here are by weight. The fresh-mix air content (ASTM C 138) was kept within the range of 8% to 15%; an antifoaming agent (B-emulsion 10% silicone defoamer) was used as necessary to control air content. The measured values of flow and air content are also presented in Table 1. The silica fume/binder and cellulose ether/binder ratios were kept constant at 0.18 and 0.005 by weight, respectively, for all the mixes considered. These ratios were observed by trial and adjustment to give desirable fresh-mix workability and fibre dispersability characteristics.

Construction and Building Materials 1993 Volume 7 Number 4

Hybrid polyethylene-fibre-reinforced cement composites: P. Soroushian et al. A mixer was employed for manufacturing the hybrid composites that is capable of applying varying accelerations to the mix particles and fibres in many different directions 5. This action forces all inclusions to come into intimate contact with the cementitious paste in a very short time, thereby eliminating the possibility of dry fibre balls forming in the mixture. The sequence and rate of addition of different constituents to the mixture were as follows: 1 2 3 4

Charge the mixer with fibrillated polyethylene pulp, cellulose ether and silica sand, and mix for 3 min. Add the polyethylene fibres with two-thirds of the water and mix for 2 min. Add the cement, silica fume and remainder of water, and mix for 5 min. Add superplasticizer and the remainder of silica sand and mix for 2 min.

Considering the relative ease of dispersion of high-modulus polyethylene fibres in mixes with no fibrillated polyethylene pulp, the following simpler mixing process was used: 1 Add cement, silica fume, cellulose ether and water, and mix for 5 min. 2 Add fibres and mix for 2 min. 3 Add the superplasticizer and silica sand, and mix for 2 min. The prepared fresh mixtures were then cast inside moulds and vibrated externally on a vibrating table for compaction. The following test specimens were manufactured: •

•

•

•

Impact - (ACI Committee 544) 7 : 6 in (150 mm) diameter x 2.5 in (64 mm) high cylinders; six specimens for each mix. F l e x u r e - ( A S T M C 1018)1.5 x 1.5 x 6 i n ( 3 8 x 38 x 165 mm) prisms tested by four-point loading on a span of 4.5 in (114.3 mm); six specimens for each mix. Compressive strength - (ASTM C 39) 3 in (76 mm) diameter x 6 in (152.4 mm) high cylindrical compression specimens; five specimens for each mix. Specific gravity, water absorption and volume o f permeable voids - (ASTM C 567) conducted on broken flexural specimens.

All the specimens were moist cured inside their moulds for 24 h and then moist curing was continued for another 8 days after demoulding. The specimens were then exposed to a normal laboratory environment until the test age o f 28 days. E x p e r i m e n t a l results

Table 2 and Figure 1 present the impact resistance test results. The figure also shows the regression lines and 90% confidence intervals for the impact resistance versus polyethylene pulp volume fraction at different polyethylene fibre contents. Factorial analyses of variance o f the impact resistance test data presented in Table 2 show that both the poly-

Table 2 Impactresistance test results*

Polyethykne pulp volume ~action (%)

0

4.5

Polyethykne fibre volume ~action (%) 0

12 7 5 8 12 Average = 9 50 57 20 20 12 Average= 34 95 35 50 40 52 Average = 55

0.1

30 45 38 27 50 Average= 38 80 69 51 30 55 Average= 57 35 45 55 65 40 Average= 48

0.2 43 59 50 25 55 Average= 46 53 71 49 55 38 Average= 54 76 309 85 95 150 Average= 143

0.3 58 59 52 38 50 Average= 52 90 63 85 65 45 Average= 70 225 230 190 120 180 Average= 189

*Number of blows to failure

ethylene pulp and fibre volume fractions have important effects at the 95% level of confidence; their interaction was also found to be significant. A comparison o f the relationships between impact resistance and polyethylene pulp volume fraction at different polyethylene fibre volume fractions (see Figure 2) indicates the positive interaction between the polyethylene pulp and fibre in improving the impact resistance of cement-based materials. Through the combined use of polyethylene pulp and fibre, the cementitious materials of this study reached relatively high levels of impact resistance. The average flexural load-deflection curves for different polyethylene pulp and fibre reinforcement conditions are presented in Figure 3. These load-deflection curves provide qualitative evidence for the favourable effects on flexural behaviour resulting from the combined use of polyethylene fibre and pulp in cementitious matrices. Detailed analyses of the flexural strength and toughness test results provide quantitative information on the interaction of polyethylene pulp and fibre in deciding the flexural performance of cement-based composite materials. Table 3 and Figure 4 present the flexural strength test results. Factorial analyses o f variance of the flexural strength test data indicate that both the polyethylene fibre and pulp volume fractions play important roles at the 95% level of confidence, in deciding the flexural strength of the hybrid fibrous cement composite. A comparison of the combined effects in Figure 5 indicates that the highest flexural strengths are achieved when both fibres are present, as shown in Figure 3 ( a ) - ( c ) . However, excessive amounts o f the two fibres, as shown in Figure 3(d), seem to influence the flexural strength of the hybrid fibrous composite negatively. The flexural toughness test results (defined as the area underneath the load--deflection curve up to a deflection equal to span length divided by 150) are presented in Table 4 and Figure 6; these values provide relative measures to compare toughness test results with those

Construction and Building Materials 1993 Volume 7 Number 4

223

Hybrid polyethylene-fibre-reinforced cement composites: P. Soroushian et al. Impact Resistance {Netof Blowsl

350

Impact Resistance (No. of Blows) 350

.....

300

eO~ Conf. B o u n d a r y

..... g o ~ Conf. eounOary

300

Reeteselon L~ne

" --

250

250

200

200

150

150

100

1O0

50

°.

. ...................

.- . . . . . . . . . . . . .

a

4

6

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. °.---

~

50

__

0 2

Regression Line

8

10

0

--

"""

o

I

I

I

I

2

4

0

8

C

Polyethylene Pulp (Vol. %)

Impact

Impact Resistance (NO.of Blows)

10

Polyethylene Pulp (Vol.%)

Resistance

(No. Of B l o w s )

350 3 5 0 /i

.....

3OO

- eo~ Conf. Boundary

gO~ Conf. 8 o u n d a r y 300 r ....

Regression Line

250

250

200

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150

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" °"/ ° ' ' ' -

2

d

Polyethylene Pulp (Vol. %)

......

I

I

4 o Polyethylene Pulp (Vol. %)

I

8

10

Figure I Impactresistanceversuspolyethylenepulp volumefraction relationshipsat differentpolyethylenefibrecontents: (a) 0% polyethylenefibre; (b) 0.1% polyethylenefibre; (c) 0.2% polyethylenefibre; (d) 0.3% polyethylenefibre

Impact

Resistance

(No. o f B l o w s )

350 .....

300 250

0% P o l y e t h . F i b e r 0,1~ Polyefh. Fibe~ 02%

--

Polyeth

Fiber

0 . 3 ~ Polyelh. Fioer

200 150 1OO 50 r

i

L

2

4

6

8

10

Polyethylene Pulp (Vol %) Figure 2 Combined effectsof polyethylenepulp and fibre on impact

resistance

obtained from specimens with similar dimensions. Factorial analyses of variance of the flexural toughness test results confirm the importance of the effects of polyethylene pulp and fibre volume fractions on flexural toughness at the 95% level of confidence. The trends observed in the combined effects of polyethylene pulp and fibre on flexural toughness (Figure 7) are comparable with those observed in the case of flexural strength (Figure 5). The compressive strength test results are given in Table 224

5 and Figure 8; the regression lines presenting the average trends in fibre reinforcement effects are shown in Figure 9. Fibre reinforcement effects on compressive strength generally are negative, or sometimes negligible. However, note that the reduction in compressive strength with polyethylene pulp reinforcement is more pronounced without polyethylene fibres (Figure 8a) than with polyethylene fibres (Figure 8b-d). This tendency also can be observed in Figure 9. A factorial analysis of variance of the compressive strength test results indicates that the effects of polyethylene pulp, but not polyethylene fibre, on compressive strength are important at the 95% level of confidence. The interaction of polyethylene pulp and fibre was also found to be statistically important. The effects of polyethylene pulp and fibre reinforcement on the bulk specific gravity of the hardened material are summarized in Figure 10. From this figure, and also by factorial analysis of variance of test results at the 95% level of confidence, one may conclude that polyethylene pulp tends to reduce the bulk specific gravity of the composite while polyethylene fibre has negligible effects; the interaction between polyethylene pulp and fibre in deciding bulk specific gravity is only moderate. The volume of permeable pores, as shown in Figure 11, tends to increase with both polyethylene fibre and particularly polyethylene pulp reinforcement. However, the interaction of these two was found to be negligible at the

C o n s t r u c t i o n a n d B u i l d i n g M a t e r i a l s 1993 V o l u m e 7 N u m b e r 4

Hybrid polyethylene-fibre-reinforced cement composites: P. Soroushian e t

al.

Load (KIps)

Load (Kil~)

1

1

..... 011 POlyelh. Pulp

..... Ot$ pOlyeth, I~llp ---- 4.§~ polyeth, p u l p --

0.75

0.75

0,0tl polyilth, pulp

0.5

0,5

0.25

0.25

0

0.5

1

a

1.5

2

2.5

a

0

3.5

4.5r4 Polyelh. Pulp g,O~ Polyeth, Pulp

I

[

f

I

I

I

0.5

1

1.5

2

2.5

3

C

Deflection x 100 (in.)

---

3.5

Deflection x 100 (in.)

Load (Kips)

Load {Kips)

1

1

..... OR PolyOth. Pulp

..... OR Polyeth. Pulp

0.75

---

4 , S l POlyeth. Pulp

--

O.Oil Polyeth, Pulp

.........

4,5~ Polyelh. Pulp 0,75

--

9,0~ Polyeth. Pulp

.-"-'"./

0.5

0.5

o

0.25

m

0.5

D

1

1.5

2

,

2.5

Deflection x 100 (in.)

0.25

i 3

3.5

O ,,,,,I

u

0.5

1

1.5

2

2.5

3

3.5

Deflection x 100 (in,)

Figure 3 Flexure load4eflection relationships: (a) 0% polyethylene fibre; (b) 0.1% polyethylene fibre; (c) 0.2% polyethylene fibre; (d) 0.3% polyethylene fibre

Tabk 3 Flexural strength test results (psi)* Polyethylene pulp volume fraction (%) 0 0

4.5

Polyethylene fibre volume fraction (%)

218 229 315 242 Average = 251 586 593 573 667 Average= 605 664 753 810 826 Average = 763

0.1 416 412 455 490 Average= 443 661 822 880 823 Average= 797 614 1077 861 Ill5.0 Average= 916

0.2 389 466 502 530 Average= 472 585 769 873 1008 Average= 810 940 952 911 1069 Average= 968

0.3 908 925 1016 1154 Average= 1001 567 713 785 649 Average= 679 943 1227 715 850 Average= 933

impact resistance and flexural strength and toughness of cement-based matrices were investigated experimentally. The combined effects of polyethylene fibre and pulp on the compressive strength, bulk specific gravity, volume of permeable pores and water absorption capacity of cementitious matrices were also investigated. Dispersing agents and a high-performance mixer were used to ensure the uniform dispersion of fibres in the matrix. A factorial experimental design was adopted to assess the joint action of the two reinforcing fibres at different volume fractions. The following conclusions can be derived from the test data generated in this investigation: 1

2

*1 psi = 0.0069 MPa

95% level of confidence. Similar conclusions could be derived for the effects o f polyethylene pulp and fibre reinforcement on the water absorption capacity of cement-based materials (see Figure 12).

3

Summary and conclusions The combined effects of a high-modulus polyethylene fibre and a fibrillated polyethylene pulp in improving the Construction

4

Both polyethylene pulp and fibre tend to increase the impact resistance of cementitious materials and their interaction is also important at the 95% level of confidence. Combined use of the two fibres leads to higher impact test results, where the interaction of the two fibres actually pronounces each other's effectiveness in increasing the impact resistance. Both polyethylene fibre and pulp have important effects on flexural strength and toughness at the 95% level of confidence. In general, the combined use of the two fibres leads to improved flexural performance characteristics; however, excessive amounts of the fibres have negative effects on flexural performance. While fibres generally have negative effects on the compressive strength of cement-based matrices, the presence of one fibre type was observed to reduce or eliminate the negative effects of the other one on compressive strength. There is a tendency in the bulk specific gravity of cementitious materials to decrease and in volume of

a n d B u i l d i n g M a t e r i a l s 1993 V o l u m e 7 N u m b e r 4

225

Hybrid polyethylene-fibre-reinforced cement composites: P. Soroushian et al. 1200

Flexural Strength (psi) ....

1000 " --

FlexuraJ Strength (psi}

[

1400

90~ ConL Boundary

....

1 2 0 0 [" ~

Regression Line

800

gO~ Conf. BoundRry Regreaalon Line

.--'"

100( )

"""

80O ann 600 4O0

400

20O

..--""

20O

I 0

I

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2

I

4 O Polyethylene Pulp (VoI,%)

a

I

8

0

10

C

..... e0tL Cone B o u ~ : l l t y "

I

I

I

4 6 Polyethylene Pulp (Vol. %)

8

10

Flexural Strength (psi) 14OO

Flexural Strength (psi) 1400

1200

2

.....

1200

Regression Line

10OO

gO~ Conf. Boundary Line

Regroaalon

1000

.- . . . . . . . " ' " "

800 600

600

400 ...--'"'"'"""

400 200

200

0 L_

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Polyethylene Pulp (Vol.%)

Polyethylene Pulp (Vol.%)

Figure 4 Flexural strength versus polyethylene pulp volume fraction relationships at different polyethylene fibre contents: (a) 0% polyethylenefibre; (b) 0. 1% polyethylene fibre; (c) 0.2% polyethylene fibre; (d) 0.3% polyethylene fibre

1400

Table 4 Flexural toughness test results (lb in)*

Flexural Strength (psi) ....

1200 - ~ 1000 -

Polyethylene pulp volume fraction (%) 0

O ~ P o l y e t h . Fiber

o.1~ P o l y e l l l . Fiber

......... 0.2~ Polyeth. Fiber O.3'!, Polyetl~. Fiber

0 600800 ~

.

.

.

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.

.

.

............

...........

400

4.5 200

0

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Polyethylene Pulp (Vol.%)

Figure 5 Combined effects of polyethylene pulp and fibre on flexural strength

p e r m e a b l e pores a n d water a b s o r p t i o n capacity to increase in the presence o f reinforcing fibres. The i n t e r a c t i o n between polyethylene p u l p a n d fibre in d e t e r m i n i n g these properties o f c e m e n t i t i o u s materials is either statistically negligible or only m o d e r a t e l y important.

Acknowledgements The authors thank the State of Michigan for providing this project with financial support from the Research Excellence F u n d . The materials used in this investigation were c o n t r i b u t e d by Allied Signal. Inc., E. I. D u p o n t de 226

Polyethylene fibre volume fraction (%)

0.001 0.002 0.001 0.1 Average = 0.025 6.67 3.03 6.70 6.74 Average = 5.79 4.61 7.71 5.24 6.6 Average = 6.04

0.1 3.30 5.84 3.99 4.20 Average= 4.33 7.45 9.66 8.3 9.90 Average= 8.83 5.81 13.61 18.34 8.58 Average= 11.59

0.2 6.30 4.45 7.10 3.56 Average= 5.35 11.94 9.15 6,36 11,22 Average= 9,67 12.83 11.24 12.04 11.50 Average= 11.90

0.3 22.30 25.73 5.59 15.6 Average= 17.3 10.546 5.11 3.81 7.91 Average= 6.84 11.0 9.67 12.81 10.37 Average= 10.97

*1 lbin = 0.113 Nm

N e m o u r s & C o m p a n y , D e w Chemical U S A , a n d Master Builders. These c o n t r i b u t i o n s are gratefully a c k n o w ledged. The a u t h o r s also t h a n k the C o m p o s i t e Materials a n d Structures Center at M i c h i g a n State University for providing this project with technical s u p p o r t a n d experimental research facilities. This technical p a p e r was first published in A C I Materials Journal, V o l u m e 90, N u m b e r 2, M a r c h - A p r i l 1993,

Construction and Building Materials 1993 Volume 7 Number 4

Hybrid polyethylene-fibre-reinforced cement composites: P. Soroushian et al. Flexure1 Toughness {Ib.in)

Flexural Toughness (Ib, ln)

32

32

28 "" .... 00~ Conf, Boundary

LI~

Regression

24

24

20

20

16

10

12

12 . . . . . . . . . - . . . . . ...

8

8

4

4

o o

i

i

I

i

2

4

6

8

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10

0

Polyethylene Pulp (Vol.%)

Flexure] Toughness (Ib.ln)

32

..... DOt, Conf. Boundary

28

I

I

I

4

O

8

24

24

20

20

16

16

12

10

Polyethylene Pulp (VOI.%)

Flexural Toughness {Ib.ln) ..... gO~ C0nf, BounOery --

Line

Regre8810n

I 2

C

32 28

..... O0~bConf, Boundary

28

Line

Reoreeelon

Regression Une

12

f

8

8

4

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Polyethylene Pulp (Vol.%)

t

I

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t

2

4

6

8

10

Polyethylene Pulp (Vol, %)

Figure 6 Flexural toughness versus polyethylene pulp volume fraction relationships at different polyethylene fibre contents: (a) 0% polyethylene fibre; (h) 0.1% polyethylene fibre; (c) 0.2% polyethylene fibre; (d) 0.3% polyethylene fibre

20

Flexural Toughness (Ib.ln)

Table 5

18

. . . . O~ Polyeth. Fiber

Polyethylene pulp volume fraction (%)

0.1~ Polyeth. Fiber

18 --14

0 . 2 ~ Polyeth. .

Fiber ,

0

10 8 6

4

4.5

( o

--o'" . . . . . . . . . . . . . . I

i

i

I

2

4

8

8

10

P o l y e t h y l e n e Pulp (VoI. %) Figure 7 Combined effects of polyethylene pulp fibre on flexural toughness

a n d is r e p r i n t e d b y k i n d p e r m i s s i o n Concrete Institute.

Polyethylene fibre volume ~action (%) 0

0. l

0.2

0.3

5000 4500 4744 7110 Average = 5339 2500 2150 2200 1950 Average = 2200 2453 1536 2514 2200 Average = 2151

3861.1 3598 3401 3200 Average = 3515 3450 3553 3100 3650 Average = 3438 3860 3865 3345 5317 Average = 4097

3919 4670 5437 4100 Average = 4532 2700 2930 2684 2354 Average = 2667 3246 4490 3860 4210 Average = 3952

5750 6500 4200 3990 Average = 5110 2094 3113 2231 3225 Average = 2666 2530.0 3791.0 3600.0 3900.0 Average = 3455

er

12

.............

Compressive strength test results (psi)*

of the American

* 1 psi = 0.0069 MPa

Construction and Building Materials 1993 Volume 7 Number 4

227

Hybrid polyethylene-fibre-reinforced cement composites: P. Soroushian et al. C o m p r e s s i v e S t r e n g t h (Psi)

BOO0 C o m p r e a a l v e S t r e n g t h (PsI)

8000 .....

gO11,Cont. Boundary

--

Regression Line

..... gO~ Conf. BounOary --

0000

Regre$elon Line

BOO0

4000

4000

2000

0

I 2

0

a

I 4

I O

I 8

0 10

0

Polyethylene Pulp (Vol. %)

Compressive

I

I

I

I

2

4

O

8

C

S t r e n g t h (Psi]

Compressive

8000

10

Polyethylene Pulp (Vol. %)

S t r e n g t h (Psi)

8000 ..... go11 Cont. Boun~ery --

..... (10% Conf, Boundary

Regroeelon Line

Regreellon Line

0000

BOO0

4000

4000

2000

2000

"---. ......

O 0

b

i

i

i

I

2

4

6

8

.. ........

0

t 2

10

Polyethylene Pulp (VoL ~)

d

I 4

t O

I

8

10

Polyethylene Pulp (Vol.%)

Figure 8 Compressive strength versus polyethylene pulp volume fraction relationships at different polyethylene fibre contents: (a) 0% polyethylene fibre; (b) 0.1% polyethylene fibre; (c) 0.2% polyethylene fibre; (d) 0.3% polyethylene fibre

Compresslv~ S t r e n g t h (Psi)

Bulk $ P e c l l l c G r a v i t y

8000

3 ---

.... O~ POlyeth. Fiber

2.5 " ~

0.1% Polyeth. Fiber 6000

O.lf* POlyeth. Fiber

.... 0,2~, Polyeth. Fiber

..... 0.2~ Polyeth, Fiber --

O! Potyeth. Fiber

2 "~

0.3~ Polyeth. Flioer

0.3~ Polyeth. Fiber

1.5

4000 i

1

2000 0.5

0

t

I

I

i

2

4

6

8

10

228

I

|

I

I

I

!

I

l

2

3

4

5

0

7

8

9

10

Polyethylene Pulp (Vol. %)

Polyethylene Pull:) (VoI. %) Figure 9 Combined effects of polyethylene pulp and fibre on compressive s t r e n g t h

L I

Figure 10 Combined effectsof polyethylene pulp fibre on bulk specific

gravity

Construction and Building Materials 1993 Volume 7 Number 4

Hybrid polyethylene-fibre-reinforced cement composites: P. Soroushian et al. Volume of Permeable Voids ('~)

Absorption After Immersion (~)

50 40

..... 0 ~ POlyeth. Fiber 40!., -l--I- 0.1~ Polyeth. Fiber

--

O~ Polyetb. Fiber

-t,-e- 0,1~ Polyeth, Fiber

0.2~ Pblyetb. F i b e r . . . . 0.3~ Polyeth. Fiber

2O

10

0

i

I

i

i

I

i

i

i

i

1

2

3

4

5

8

7

8

g

10

I

I

I

I

2

4

0

8

10

Polyethylene Pulp (Vol.%)

Polyethylene Pulp (Vol. %)

Figure 11 Combined effects of polyethylene pulp and fibre on volume of permeable voids

Figure 12 Combined effects of polyethylene pulp and fibre on absorption after immersion

References

4

1

5

2 3

High Performance Fibers, Allied Fibers, Allied Corporation, Petersburg, 1985 lnfoplus, V. 1 and 2, Dupont Company, 1989 Soroushian, P. and Khan, A. Allied Signal polyethylene fibre application to coarse aggregate concrete. Report No. MSUENGR 89-010, College of Engineering, Michigan State University, Lansing, June 1989

6 7

Cellulose Ether Technical Handbook, Dew Chemical Company, Midland, 1988 Production Information Brochure, Elkem Materials, Inc., Pittsburgh, 1986 Pyrament Cement Technical Information, Pyrament Division, Lone Star Industries, Houston ACI Committee 544. Measurement of the properties of fiber reinforced concrete (ACI 544.2R). ,4CI Mater. J. 1988, 85, (6), Nov.Dec., 583-593

Construction and Building Materials 1993 Volume 7 Number 4

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