macro fiber reinforced pervious concrete

Macro Fiber Reinforced Pervious Concrete

John Kevern and Dan BiddlePervious in Paradise 2014

Motivation• Raveling and surface

durability is still prevalent in pervious concrete

• Micro fibers have previously shown to improve pervious durability

• Limited anecdotal evidence suggested that macro-synthetic fibers

Study Scope• Determine the effect macro-synthetic fibers

have on pervious concrete propertiesand• Determine the best fiber length and dosage

Study MixturesMaterial Description Amount (pcy)Coarse Agg. 3/8 in. limestone 2175Fine Agg. C33 river sand 164Cement Lafarge TI/II 573Water   195Water Reducer BASF Glenium 7500 4 oz/cwtAir Entrainer BASF Everair Plus 2 oz/cwtHydration Stabilizer BASF Delvo 6 oz/cwt

FORTA Ferro-Green1.5 in. – 2.5 pcy, 5.0 pcy, 7.5 pcy2.25 in. – 2.5 pcy, 5.0 pcy, 7.5 pcy

*All samples individually placed to control voids at 25%

Tests• Unit weight (ASTM C1688 and ASTM

C1754) and voids (ASTM C1754)• Plastic workability• Strength• Permeability and infiltration• Abrasion• Freeze thaw durability

Gyratory Workability

8284

86

88

90

92

94

9698

100

102

0 20 40 60 80 100Gyrations @ 60kPa

Appa

rent

DoC

(%)

8

Workability Energy Index (WEI)

Compaction Densification Index (CDI)

Workability (WEI) Explanation Range

Self-Consolidating > 640 Acceptable Workability 640>WEI>600

Poor Workability WEI<600

Compactibility (CDI) Explanation Range

No Additional Compaction Required CDI<50 Normal Compaction Effort Required 50<CDI<450

Considerable Additional Compaction Effort Required CDI>450

Abrasion (ASTM C944)

Abrasion (ASTM C1747)

Freeze-Thaw Durability (ASTM C666a)

Results – Fresh Properties

At 25% design void content, not much impact on constructability

Workability (WEI) Explanation Range

Self-Consolidating > 640 Acceptable Workability 640>WEI>600

Poor Workability WEI<600

Compactibility (CDI) Explanation Range

No Additional Compaction Required CDI<50 Normal Compaction Effort Required 50<CDI<450

Considerable Additional Compaction Effort Required CDI>450

Fresh Unit WeightASTM C1688

Avg. (pcf)Control 121.8 659 382.5/1.5 119.2 670 05.0/1.5 121.4 660 37.5/1.5 124.8 646 38

2.5/2.25 124.4 662 15.0/2.25 125.1 651 77.5/2.25 125.8 647 12

WEI (DVC)Mixture

CDI (DVC)

Results-Unit Weight

Control 2.5pcy/1.5in 5.0pcy/1.5in 7.5pcy/1.5in 2.5pcy/2.25in 5.0pcy/2.25in 7.5pcy/2.25in110

112

114

116

118

120

122

124

126

128

130

ASTM C1688 Fresh Unit Weight ASTM C1754 Hardened Unit Weight

Uni

t Wei

ght (

pcf)

Results – Compressive Strength

Control 2.5pcy/1.5in 5.0pcy/1.5in 7.5pcy/1.5in 2.5pcy/2.25in

5.0pcy/2.25in

7.5pcy/2.25in

0

500

1,000

1,500

2,000

2,500

3,000

3,500

7d 28d

Com

pres

sive

Stre

ngth

(psi

)

Results – Tensile Strength

Control 2.5pcy/1.5in

5.0pcy/1.5in

7.5pcy/1.5in

2.5pcy/2.25in

5.0pcy/2.25in

7.5pcy/2.25in

0

50

100

150

200

250

300

350

400S

plitt

ing

Tens

ile S

treng

th (p

si)

Results – Abrasion

Control 2.5pcy/1.5in

5.0pcy/1.5in

7.5pcy/1.5in

2.5pcy/2.25in

5.0pcy/2.25in

7.5pcy/2.25in

0

2

4

6

8

10

12

Mas

s Lo

ss (g

)

MixtureAbrasion (%) Abrasion (g)ASTMC1747 ASTM C944

Control 28.6% 11.02.5/1.5 24.2% 3.85.0/1.5 26.5% 4.87.5/1.5 27.1% 4.8

2.5/2.25 26.0% 5.75.0/2.25 24.5% 4.77.5/2.25 26.2% 7.7

Results – Freeze ThawMixture

Durability Factor (Mass)

Durability Factor (RDM)

Control 53 142.5/1.5 38 125.0/1.5 53 77.5/1.5 85 212.5/2.25 89 405.0/2.25 91 417.5/2.25 96 44

Results – Freeze Thaw

Control – 187 cycles

2.5 pcy (1.5 in.) – 133 cycles

5.0 pcy (1.5 in.) – 188 cycles

Results – Freeze Thaw

Control – 187 cycles

2.5 pcy (2.25 in.) – 300 cycles

7.5 pcy (2.25 in.) – 300 cycles

• Ferro-Green® by FORTA macro fibers function like fine aggregate, increasing fresh unit weight of the mixtures.

• Fiber addition decreased infiltration and permeability. No trends were observed with respect to dosage rate.

• Fiber addition did not affect compressive strength.• The addition of fibers increased tensile strength

for all mixtures with increased strength corresponding to dosage rate. Similar strength increases were observed at each dosage rate, independent of fiber length.

Summary and Conclusions

• Raveling and abrasion was reduced for all fiber dosages.

• Freeze-thaw durability was improved for all mixtures containing 2.25 inch length fibers. Only the mixture containing 7.5 pcy of the 1.5 inch fibers had improved freeze thaw durability versus the control.

• Comparing tensile strength increase, raveling reduction, and freeze-thaw improvement, 5.0 pcy of the 2.25 inch fibers appears to be the optimum dosage of the combinations tested.

Summary and Conclusions

Contact Information

John T. Kevern, PhD, PE, LEED APAssociate Professor of Civil Engineering370A Flarsheim Hall, 5110 Rockhill Rd.University of Missouri – Kansas CityKansas City, MO 64110Phone: 816-235-5977Fax: 816-235-1260Email: kevernj@umkc.edu