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: [email protected]