A STUDY ON MIX PROPORTIONS AND PROPERTIES OF STEEL FIBER REINFORCED
ROLLER-COMPACTED CONCRETE FOR PAVEMENTS(Translation from Proceedings of JSCE, No.669/V-50, February 2001)

Makoto KAGAYA

Toru SUZUKI

Shuichi KOKUBUN

Hiroshi TOKUDA

Indented and hooked steel fibers were selected as two possibilities for use in roller-compacted concrete
for pavements. Appropriate unit water content, sand percentage, and fiber content were determined whilewater was reduced by a suitable degree by incorporating a superplasticizer in appropriate proportion. The
target consistency was given in terms of a vibration compaction value as measured by a Swedish-type Vebe
apparatus. Segregation was reduced by using steel fibers, and the fiber orientation in the concrete tended toapproach the horizontal when compaction was with a surface vibrator. Flexural strength, ductility, and frost
resistance were improved. Bond strength between the concrete and abraded asphalt pavement surface were
evaluated at the age of 7 days. Drying shrinkage was almost the same as for non-fiber roller-compacted
concrete despite the increase in unit water content for a given consistency.
Keywords: mix proportion, degree of segregation, fiber orientation, flexural strength, flexural ductility, frost
resistance, drying shrinkage

Makoto KAGAYA is a professor in Civil and Environmental Engineering at Akita University, with
25years research experience in concrete materials and technology. He is a member of JSCE, JCI, RILEM
and ACI, and his recent research themes include roller-compacted concrete, recycled aggregate concreteand self-compacting concrete.
Toru SUZUKI is a research engineer at Obayashi road CO., LTD., Technical Research Laboratory. He isa member of JSCE and engages in studying on concrete and asphalt road construction materials.
Shuichi KOKUBUN is a technical director of Kaihatsu Consultant CO., LTD., Transport andEnvironment. He is the expert engineer of pavement and road management, and obtained D. Eng. from
Akita University in 1997. He is a member of JSCE.
JSCE member Hiroshi TOKUDA is an emeritus professor of Akita University. He has publishednumerous papers on thermal properties of massive concrete and other properties of concrete materials.

1. INTRODUCTION
Roller-compacted concrete for pavements (RCCP) suffers from a number of problems. In particular, the use of tiebars or slip bars is difficult, because of the heavy compaction by vibratory roller. As a result, it is known that
RCCP is prone to cracking due to thermal stress or drying shrinkage, and this prevents the placing of pavementslabs with long joint spacing. On the other hand, steel-fiber reinforced concrete (SFRC) has been used for tunnel
linings and bridge deck strengthening, where it offers superior flexural strength and crack resistance, and thestrengthening effect of SFRC has been looked over again from a view point of compound materials. If rollercompacted concrete (RCC) could be given the properties of SFRC, it would offer advantages as a heavy traffic
pavement because of its rapid construction and shorter lead time. There is good reason, therefore, to accumulate
basic data on the properties of such a new type of pavement.
Ficheroulle1) indicated that one could lay pavement with steel-fiber-roller-compacted concrete (SFRCC)
containing 30mm corn type steel fibers as easily as with conventional RCC. From the results of observations, it
was clarified that the surface texture of the pavement could secured by paving with a thin layer of asphalt without
joints and that traffic noise was reduced. This method proved suitable for heavy traffic. However, details of mix
proportion and the mechanical and physical properties of the SFRCC were not described in the report. Nanni etal.2) carried out trial pavement construction with SFRCC containing 0.6 wt% of straight and hooked steel fibers(30 mm in length). They described how construction could be carried out appropriately, and demonstrated thatstrength and toughness were improved. However, accumulation of experimental results with various fiber contents
was still needed. In Japan, there has been little research with SFRCC, and data on mix proportions and theproperties of fresh and hardened SFRCC are needed before it can be applied to actual pavements.
In this study, four types of steel fiber are tested from the viewpoint of reinforcement effect. These are indented
and hooked steel fibers with different lengths. The first step in the study was to decide on the mix proportion. The
relation between water content and modified VC value as a consistency reading was obtained, and a unit watercontent and sand percentage for a given consistency were decided. Then relations between fiber content and bothmodified VC value and flexural strength were obtained, and appropriate fiber contents were decided from theviewpoints of workability and strength. The degree of unit water content reduction and the resulting change in
flexural strength when a superplastcizer was added were examined, and an appropriate dosage selected.
Secondly, the degree of coarse aggregate segregation and steel fiber segregation was clarified using drop test
apparatus. Then the angle of the steel fibers in the SFRCC to the horizontal after compacting by surface vibrator
was measured, and the angle was compared with the case of compacting by an immersed vibrator.
Thirdly, the mechanical properties of the concrete were investigated, and differences in flexural strength andtoughness depending on fiber type were clarified. Then, assuming that SFRCC would be overlaid on the abradedasphalt pavement surface, the bond strength between the concrete and asphalt was tested.
Finally the physical properties of the SFRC were investigated. The freezing and thawing resistance with andwithout AE agent was compared, and drying shrinkage properties were examined for each fiber type. A number of
useful results were obtained from these investigations.
2. EXPERIMENTAL OUTLINE(1) Materials and Mix Proportions
Normal Portland cement (density: 3.16g/cm3), river sand (density: 2.54g/cm3; absorption: 3.46%; FM: 2.74),
crushed stone (density: 2.67g/cm3; absorption: 1.46%; FM: 6.60), an AE water reducing agent (retarder type;lignin sulfonic acid compound), a superplasticizer (AE type; polycarbonate acid compound), an AE agent (natural
reginate), and a supplementary AE agent (degenerated alkilcarbonate acid compound) were used. All agents wereused in the form of undiluted solution or solution, and they were combined with the water.

Table 1 Shape and size of steel fibers
Symbol Gravity
I-1
I-2
F-1
F-2

7.85

Length (mm)Diameter (mm)Aspect ratio

50
30
60
30

0.7
0.6
0.8
0.6

71
50
75
50

Type
Indented
HookedTable 2 Mix proportions of concrete
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

Modified
WaterSand
Steel Fiber
Void ratio Air content
VC value
Cement percentage content
(%)
(%)
Water
(sec)
ratio (%)(%)
(vol%)
38～82
0.1～2.7 2.3～3.6 37.0～41.2
41.8
107～119－21～60
0.3～3.3 1.7～3.4 39.8～46.7
42.0
1.0
115～135
50～273 0.8～8.4 0.8～6.1
39.8
30～60
1.0
116
21～285 0.3～8.1 2.6～3.9
39.8
40.0
0～1.6
116
53
0.1
2.3
37.0
40.0
107
－
46
0.5
2.1
42.6
40.0
1.0
123
51
0.6
2.7
40.5
40.0
1.0
117
55
1.0
2.1
41.2
40.0
1.0
119
47
0.3
2.8
39.4
40.0
1.0
114
49～53
2.1～3.4 2.4～3.4 34.3～36.0
40.0
1.0
99～10445～51
0.6～2.3 1.8～3.1 39.8～41.9
40.0
1.0
115～12146～54
2.0～3.0 2.0～3.6 38.8～39.8
40.0
1.0
112～11545～49
2.4～3.8 3.0～4.3 38.1～40.1
40.0
1.0
110～11645～55
2.4～3.4 3.0～4.5 36.0～38.4
40.0
1.0
104～111
53
0.1
3.0
36.3
40.0
105
－
45
0.2
3.5
40.8
40.0
1.0
118
48
0.2
4.0
39.8
40.0
1.0
115
48
0.3
3.6
40.5
40.0
1.0
117
52
0.2
3.7
38.8
40.0
1.0
112
8**
4.2
40.0
45.5
1.0
185

*AE water reducer is used in 1～9. Super AE water reducer is used in 10～14.
** 20 is conventional SFRC and has 8cm slump

Unit weight (kg/m3)
Cement
289
289
289
289
289
289
289
289
289
289
289
289
289
289
289
289
289
289
289
463

Sand

Gravel845～858 1236～1255
821～842 1191～1222
597～1203 843～1476
791～806 1256～1281
811
1294
785
1252
791
1261
789
1258
794
1266
817～822 1296～1308
790～799 1256～1266
796～802 1266～1270
796～804 1263～1273
800～810 1271～1282
816
1298
793
1260
796
1266
794
1261
799
1270
703
892

Steel Fiber Admixture*
－
79
79
0～118
－
79
79
79
79
79
79
79
79
79
79
79
79
79
79
79

Type of
Fiber

0.72
－
0.72
F-2
0.72
F-1,2 I-1,2
0.72
F-1,2 I-1,2
0.72
－
0.72
I-1
0.72
I-2
0.72
F-1
0.72
F-2
1.45～4.34－
1.45～4.34
I-1
1.45～4.34
I-2
1.45～4.34
F-1
1.45～4.34
F-2
0.72 0.029－
0.72 0.029
I-1
0.72 0.029
I-2
0.72 0.029
F-1
0.72 0.029
F-2
0.14
F-2

AE water reducer (left side) and assistant AE agent (right side) is used in 15～19

Generally, for good reinforcing effect, fiber length is greater than the maximum size of aggregate and the diameterto length ratio (aspect ratio) is more than 50. However, the aspect ratio should be less than 100 because longer
fibers tend to form fiber balls. In this study, two fiber lengths were used. The fiber types, sizes, and aspect ratios
are shown in Table 1. The indented fiber has an indented surface and the hooked fiber has hooks at both ends.
Table 2 shows the mix proportions of the concrete used in the experiment. Mix proportions 1 to 4 and 10 to 14
were used to examine the characteristics of SFRCC mix proportions, while mixes 5 to 9 and 15 to 20 were used to
examine the degree of segregation, fiber orientation, mechanical characteristics, freezing and thawing resistance,and drying shrinkage.
(2) Manufacture of concrete
To produce SFRCC, the crushed stone, sand, cement, and water (containing the agents) were placed in a pan-type
mixer of 0.05m3 capacity and mixed for 60 seconds. The fiber was then manually added little by little and mixed
for 210 seconds. The total mixing time was therefore four and a half minutes. For conventional RCC, the concrete
was mixed for 90 seconds. After mixing, test sample was taken from the concrete and consistency was measured
using a Swedish-type VB consistency-meter. Compaction degree was measured after 60 seconds of vibration. The
air content was measured after the consistency test using the JIS A 1116 method (gravimetric method) and the JIS
A 1128 method (Washington-type air meter). In the case of JIS A 1128, the sample was placed in a vessel in threelayers and a rod inserted 25 times. The layers were compacted using a vibrating tamper until liquefied mortar roseup through the space between tamper plate and vessel wall. After compaction, the vessel was fitted with a cap andthe air content was measured by opening a pressure valve. The size of test specimen was 10×10×40cm and theconcrete was weighed so as to ensure a 96% compaction degree for each sample. The first layer of concrete wasplaced in the mold, and the rod inserted 25 times. A steel plate was placed on the concrete surface, and then theconcrete was compacted using a vibrating tamper (frequency: 50 Hz; weight: 15 kg) until liquefied mortar rose up
in the space between plate and mold. Before casting the second layer, the top surface of the first layer wasscratched and loosened using a steel rod so as to ensure the integrity of the two layers. The top surface wasfinished using a steel trowel.
(3) Test Method for Measuring Segregation Degree and Orientationa) Segregation degree
Segregation of RCC is particularly notable when concrete is discharged from hopper to dump truck and fromdump truck to the asphalt finisher at the construction site. The test apparatus was designed to replicate site
conditions in the laboratory3). It has a 160cm high and 80cm long vertical chute, and an 80cm diagonal chute at a
45 degrees angle. A vinyl sheet measuring 0.2mm in thickness was placed inside the chutes to provide a smoothsurface.
Concrete samples weighing about 10 kg were dropped into the inlet of the vertical chute in a single throw. Afterdischarge from the apparatus, samples were divided equally into one part near the outlet and the remainder. The
coarse aggregate and fiber were washed out from each 5 kg sample according to JIS A 1112 (test method forwashing analysis). Degree of segregation was calculated by using Eq.1.
Segregation degree Sg (%) = (CA2-CA1)/ CA0 ×100･････ (1)CA0：Ratio of unit coarse aggregate or steel fiber content to unit weight of concrete.
CA1, CA2：Ratio of weight of coarse aggregate or steel fiber in the sample to weight of concrete sample with
CA1 the sample taken near the outlet and CA2 the other sample.
b) Orientation
Since it was thought that the fiber orientation differed in SFRCC compacted by a surface vibrator and SFRC
compacted by an immersed vibrator, the orientation of steel fibers in SFRCC and SFRC specimens was measured.
Orientation angle θ (θ≦90 degrees) was defined as the angle of the fiber to the horizontal. In order to measure
this angle, the surface paste on one side of an SFRCC specimen was washed out with a water spray 4 or 5 hours
after casting. Then, the angle at the surface, which was divided into three blocks for measurement purposes, wasmeasured using a protractor 24 hours later. In the case of SFRC, a super retarder was spread on the side of therectangular mold so as to allow washing out of the paste. In this case, the paste was washed out 5 or 6 hours after
casting and measurements were carried out 24 hours later. There were 20 to 30 fibers in each block of the two
specimens (one specimen each for SFRCC and SFRC).
(4) Test Method for Mechanical Propertiesa) Flexural strength and toughness test method
Specimens of SFRCC and SFRC were cured in a water bath at 21℃ for 28 days. The flexural strength andtoughness of the concrete were measured according to JSCE-G552-1983. Three or four specimens were tested fora given test condition.
b) Bond strength test method
An asphalt specimen was taken from national highway 16 after being in service for several years. The specimen
was cut to obtain plates 10 cm in width, 40 cm in length and 5 cm in thickness. These were cured for 2 days in an
air bath at 20℃ and 60% relative humidity. The asphalt plates were placed in a mold measuring 40cm in length,
10cm in width and 10cm in depth, and a 5cm layer of SFRCC was placed directly onto the traffic-abraded surfaceof the asphalt plate. The mold was removed after 24 hours, and then the resulting beam specimens were cured bywrapping in wet cloth in the laboratory. After 1, 3, and 7 days of curing, test specimens were cut out withmeasurements 10cm width, 10cm height and 15cm length. The loading surface of the specimen was smoothedwith a concrete cutter and polisher, and tests were carriedout by the splitting tensile test method4) shown as Fig. 1.
An average splitting tensile strength was obtained by
testing six specimens.
(5) Test method for freezing-thawing resistance anddrying shrinkage strain

Loading Plate

Cement Concrete

Asphalt Concrete
5×10× 15cm 5×10× 15cm

The freezing-thawing test was conducted according to
JSCE-G501-1986. The ultrasonic velocity of concrete
was measured when the specified number of cycles had
been completed. Drying shrinkage strains of the concrete
specimens, which were cured in a water bath at 21℃ for
7 days, was measured over 190 days at 20℃ and 60%
relative humidity using a contact gage according to JIS A
1129. The percentage weight loss was also measured.

10cm
Fig. 1 Bonding test specimen and method

Fig.1 Bonding test specimen and method

3. EXAMINATION OF MIX PROPORTION CHARACTERISTICS
There have been no previous reports on mix proportions for SFRCC as applied to pavements, but it is thought thatthe design process basically begins with a decision on unit water content and sand percentage from a viewpoint ofgood workability, required strength, durability, crack resistance, and other factors.
The purpose of this chapter is to examine differences in mix proportion when steel fibers are used, based on themix design of conventional roller compacted concrete. To this end, the consistency of the concrete was measured
using a Swedish-type Vebe apparatus in terms of a vibrating compaction value (VC value), and then appropriate
unit water content, sand percentage and fiber content were determined. The water reducing effect of adding a
superplasticizer was also examined. Mix proportions 1 to 4 and 10 to 14 as shown in Table 2 were used in thischapter.
(1) Unit Water Content and Sand Percentage
N on-Fiber

90

SFRCC

80
Modified VC value (sec)Figure 2 shows the relationship between unit water content andmodified VC value when concrete is mixed with and without
steel fiber F-2 as shown in Table 1. Modified VC value tends
to decrease as the unit water content increases. The change inmodified VC value when the unit water content is above
115kg/m3 reaches almost 3 to 4 seconds per 1kg/m3 of unit
water content, both with and without steel fibers. These results
indicate that it is possible to estimate unit water content,
because the change in modified VC value is almost constantfor a given shape and size of fiber. In this respect, it is similar
to the relationship between unit water content and slump in
conventional SFRC.

M ix p rop ortion 1

70
60
50

M ix p rop ortion 2

40
30
20
105

115
125
135
3
Unit water content (kg/m )145

Figure 3 shows the relationship between water content of theFig. 2 Changes in modified VC value
mix proportions shown in Fig. 2 and flexural strength at theage of 7 days. Flexural strength decreases with rising water-cement ratio because the modified VC value falls withincreasing unit water content for a given unit cement content. The water cement ratios ranged from 40% to 47%

300
Modified VC value(sec)

250

I-1

I-2

F-1

F-2

200
150
100
50
0

100
Compac tion degree(% )2Flexural strength (N/mm )and from 37% to
842%, respectively,
for the cases with
7
and without steel
fibers. The strength
difference in the two
6cases was about 0.7
and 0.5 N/mm2,
5respectively.
The
strength of concretewith steel fibers was
4
1.5 times higher than
35
40
45
50
that without fibers
Water-c ement ratio (% )for a given waterFig.3 Relationship between water-cement ratio
cement ratio, so theand flexural strength
reinforcing effect of
the steel fibers is significant. Thus it is considered that theuse of steel fibers is advantageous in terms of early opening
to traffic.
Generally, unit water content is determined as the minimum
possible for a given consistency. Therefore, the sandpercentage was selected to suit the minimum unit watercontent of 115 kg/m3 for the consistency range of 40 to 60
seconds (modified VC value).

98
96
94
92
90

6

Air content(% )542Flexural strength at 7 days(N/mm )Figure 4 shows the relationship between sand percentage and3
modified VC value, compaction degree, and air content (asmeasured by a Washington-type air meter). The reason for2
use of this type of air meter was the desire to examine the1remaining air void content of the concrete, after compactingwith a surface vibrator. These graphs clearly show the0minimum modified VC value and maximum compaction
25
35
45
55
65
degree for the given sand percentage. The sand percentage
Sand perc entage (% )was about 40% independent of steel fiber type. According to
Fig.4 Relationship between sand percentage and modified
one reference5), these overall tendencies are the same as for
VC value, compaction degree, and air content
conventional RCC and generally, the sufficient compaction
I-1
I-2
11
degree are given more than 96 % of compaction degree. From
F-1
F-2
this specification, the optimum sand percentage of SFRCC was
10
decided 40 % for a given consistency and compaction degree.
The air content increased proportionally with rising sand9
percentage for a constant unit water content. This is probably
due to the lack of sufficient cement paste content to fill the voids
8
formed by the sand particles. Further, it was observed that when7
the sand percentage exceeded 48% that fibers gathered locallywithout proper dispersal in the case of I-1, and they remained
6
being combined with water-soluble glue in the case of type F
fibers, which were easier to add to the mixer than type I.
Figure 5 shows the relationship between sand percentage andflexural strength at the age of 7 days. The bold line shows
strength without steel fibers. It is clear that strength remains

5

25

35

45
55
Sand perc entage(% )65

Fig.5 Relationship betw een sand perc entage andflexural strengthFigure 7 shows the relationship between fiber content andflexural strength, corresponding to the data shown in Fig. 6.
Maximum strength was obtained at a fiber content of 1.0% in
the case of long fibers. This is explained by the fact that
insufficient dispersion and increased air content at 1.5% cause
a reduction in strength, as mentioned above. In the case of
short fibers, strength increased as the fiber content increased.
However, more compaction was required as indicated in theincrease in modified VC value. From these results, the mostsuitable fiber content was fixed at 1.0%. The unit watercontent was then determined through trial mixing to achieve a
45 to 55 second modified VC value, with 289 kg/m3 unit
cement content, 40.0% sand percentage and 1.0% fiber
content. Figure 8 shows the unit water content and watercement ratio for each fiber type. The lowest unit water content
was without fibers at 107 kg/m3, and the highest with I-1 was
123 kg/m3. Water-cement ratios ranged from 37.0% to 42.6%
corresponding to this range of unit water content. In thefollowing examination, these mixture proportions were used.

M odified VC value (s ec)

F-1
F-2

200
150
100
50
0

Compac tion degree (% )

100
98
96
94
92
90
88
2.0

Air c ontent (% )Figure 6 shows the relationship between fiber content andmodified VC value, compaction degree, and air content. The
modified VC value increased and compaction degree
decreased with an increase in fiber content. These tendencies
are particularly clear in the case of indented type I fibers andlong fibers, but the difference between fiber types iscomparatively small for fiber contents below 1%. In addition,
it was observed that type I-1 fiber gathered locally and formed
fiber balls and type F fiber remained being combined withwater-soluble glue at a fiber content of 1.5%. At this fiber
content, therefore, is necessary for the unit water content to be
increased to ensure sufficient compaction and fiber dispersion.
The air content increased with increasing fiber content withlong fibers, but ranged from 1.0% to 2.0% after sufficientcompaction.

I-2

250

1.5

1.0

0.5

0

0.5
1
Fiber content (% )1.5

Fig.6 Relationship between fiber content and modified
VC value, compaction degree, and air content
2(2) Fiber content

I-1

300

Flexural strength at age of 28 days (N/mm )almost constant up to a 48% sand percentage and is 1.3 to 1.8
times more than the strength without steel fibers. In case offiber F-2, the strength decreased drastically beyond 48% sandpercentage and was almost the same as in the case without
steel fibers. This lack of strengthening effect is explained asfollows. The fibers were dispersed insufficiently in theconcrete and air voids remained as a result of a shortage of
cement paste, even if the concrete was compacted sufficiently.
It is concluded that the unit water content should be greaterthan 115 kg/m3 when the sand percentage is 50% or more aswith conventional SFRC.

13

I-1
I-2

11

F-1
F-2

9
7
5
0

0.5
1
Fiber content (% )1.5

Fig.7 Relationship between fiber content and flexural strengthWater-cement ratio (% )3Water content (kg/m )

120

45

110
100

40

90
80

35
Vf=0

I-1

I-2

Fiber type

F-1

Vf=0
I-1
I-2
F-1
F-2

130

3

□ W ater co ntent (kg /m )■ W ater-cement ratio (% )130

Water c ontent (kg/m )

50
3

F-2

120
110
100
90
44

Water-c ement ratio (% )140

Fig.8 Water content and water-cement ratio of concrete

42
40
38
36
34

4
3
2
1

2

Figure 9 shows the relationship between dosage ofsuperplasticizer between 0.5% and 1.5%, and unit watercontent, water-cement ratio, air content and flexural strength.
The reduction in unit water content was 3 to 4 kg/m3 for an
increase of 0.5% in dosage of superplasticizer, and unit
water content could be reduced by 5 to 10 kg/m3 at 1.5%
dosage compared with the case without a superplasticizer.
The corresponding reduction in water-cement ratio was 1.7%
to 3.4%. The air content was almost unchanged or slightly
higher than without a superplasticizer when the dosage was
1.5%. The flexural strength without fibers increased with anincrease in dosage, but with fibers the strength at a dosage of
1.5% was the same or less than at 1.0% dosage.

Flexural strength (N/mm )(3) Reduction in Unit Water Content by use ofSuperplasticizer

Air c ontent (% )

5

12
11
10
9
8
7
6
0.0

0.5
1.0
Dosage of superplasticizer (% )1.5

Fig.9 Relationship between dosage of superplasticizer andwater content, water-cement ratio, air content, and flexural

The reason for this is as follows. The water-cement ratio decreased with increasing dosage, while the unit watercontent and cement paste content decreased. However, the air voids formed by the aggregate and fibers were notfilled by the reduced paste even after full compaction. These remaining air voids would not contribute to strength
improvement. These results clearly show that when a superplasticizer is used to reduce the unit water content of
SFRCC, an appropriate dosage must be chosen so as to ensure no strength reduction takes place. The appropriate
dosage was 1.0% in this study.
4. EXAMINATION OF SEGREGATION AND ORIENTAION OF FIBERS
It has been pointed out that segregation of coarse aggregate and the mortar component should not occur inconventional RCC for pavements6). Although an improvement in flexural strength can be expected if steel fiber
are added to conventional RCC, which cannot contain reinforcing bars, the degree of segregation compared withconventional RCC must be clarified and it is necessary to investigate differences in fiber orientation due todifferent compaction procedures such as surface vibration and immersed vibration.
In this chapter, the segregation of coarse aggregate and steel fibers is measured using mix proportions 5 to 9 and
20 in Table 2 and the results are compared with conventional RCC.

Figure 10 compares the degree of segregation of
aggregate and steel fiber in SFRCC for each fiber type. A
decrease of 1.3% to 11.5% in segregation was observed
as compared with conventional RCC (Vf=0), and fiber Ⅰ
and long fibers were more effective at preventing
segregation. These findings are explained as follows. The
mortar component of SFRCC, especially when indented
fibers are used, is more viscous than that of conventional
RCC because of the higher unit water content for a given
consistency. The surface texture of indented fibers is lesssmooth than hooked ones, and this restrains segregationof the coarse aggregate. Long fibers have a lower falling
velocity as a result of greater friction on the discharge
chute, and they tend to gather near the chute exit; at thesame time, coarse aggregate particles dispersed far fromthe exit. For this reason, long fibers are unable to restrain
the segregation of aggregate. However, as use of steel
fibers reduces segregation, they are an effective way toprovide good quality concrete pavement slabs.

Segregation degree(% )Coarse aggregat e

20
10
0
-10

Vf=0

I-1

I-2

F-1

F-2

St eel fiber-20Type of fiber
Fig. 10 Segregation of aggregate and steel fibers

I-130
Number of steel fibers(1) Segregation

30

A verage angle of I-1=29.1°
A verage angle of I-2=29.4°

20

I-2

10

0
0-15

16-30

31-45

46-60

61-75

76-90
F-1

30
Number of steel fibers

The orientation of fibers in SFRCC compacted with asurface vibrator is measured and compared with theresults using an immersed vibrator, and the effect ofdifferences in fiber orientation on flexural strength isclarified.

A verage angle of F-1=30.6°
A verage angle of F-2=29.8°

F-2

20

10

0

(2) Characteristics of Fiber Orientation

0-15

16-30

31-45

46-60

61-75

Orientation angle of steel fiber (degree)

76-90

Number of steel fibers

Figure 11 shows fiber counts by type at the surface of a
Fig. 11 Distribution of angle to horizontal
specimen for each 15 degrees of angle to the horizontal.
About 60 to 90 fibers were counted per specimen, and30
SFRCC
the average angle to the horizontal is shown in the figure.
SFRC
It can be seen that most fibers are oriented between 0 and
30 degrees, with about 50% of all fibers in this range.
20
Only 2% to 8% of fibers were in the range 76 to 90
degrees. The average angles for I-1, I-2, F-1 and F-2
10were 29.1, 29.4, 30.6 and 29.8 degrees, respectively, so
there is little variation with fiber type. Figure 12
compares the orientation in the case of short hooked
0fibers between SFRCC compacted with a surface vibrator
0-15
16-30
31-45
46-60
61-75
76-90
and 8cm-slump SFRC compacted using an immersed
Orientation (degree)
Fig. 12 Distributon of angle to horizontal
vibrator. The number of fibers with an angle of 0 to 30
degrees in SFRC is almost the same as in SFRCC,
however SFRC contains many fibers in the 30 to 90 degree range, and especially in the 76 to 90 degree range. The
average orientation of fibers in SFRCC and SFRC was 30 degrees and 41 degrees, respectively. This difference isdue to the different vibration compaction procedure. The surface vibrator used for SFRCC exerts pressure on theconcrete layer, and tending to force the fibers into a horizontal orientation, but this is not the case for theimmersed vibrator used for SFRC. In case of the immersed
vibrator, the mortar component tends to flow under the
influence of centrifugal force from the vibrator, and fibers
become oriented according to the flow of the mortar component.
Figure 13 compares the flexural strength of SFRCC and SFRC
with a 40% water-cement ratio. The strength of SFRCC ishigher than that of SFRC. The overall horizontal orientation offibers in SFRCC, as shown in Fig. 12, is thought to effectively
reinforce it against the bending moment.

F-2

2

Flexural strength (N/mm )

10
8
6
4
2
0
SFRC

SFRCC
Type of concrete

5. EXAMINATION OF MECHANICAL CHARACTERISTICS

Modified VC value (sec )W /C=39.8%
3

40
20
0
Vf=0

12

I-2
Type of fiber

F-1

F-2

W/C=39.8%
Water content 115kg/m 3

10
8
6
4
2
0
Vf=0

I-1

I-2
T ype of fiber

F-1

F-2

Fig. 15 Comparison of flexural strength122Figure 14 shows the consistency of SFRCC measured by
the modified VC value for each fiber type. The same mix
proportion was used in each case and the VC value wascompared with that of conventional RCC vf=0. The VC
value for SFRCC with indented fibers is higher than thatwith hooked fibers, and both are naturally higher than thatof conventional RCC. This tendency is clearer in the caseof long fibers. A lot of cement paste is needed to coverindented and long fibers compared to hooked and shortfibers because their surface area is greater, and it isconsidered that SFRCC using indented and long fibers
requires more vibration time to fill the air voids withcement paste. Figure15 shows flexural strengths
corresponding to Fig.14, in which the compaction degreeof the SFRCC specimen was 98.5% to 99.8%. The
strength of SFRCC is 26.3% to 82.1% higher than that of
RCC depending on the type of fiber. This difference canbe attributed to the reinforcement effect of the fibers
because the same mix proportion is used. The effect is

I-1

Fig. 14 Comparison of modified VC value

Flexural strength (N/mm )(1) Flexural Strength of Given Mix Proportion and
Modified VC Value

W ater con ten t 115kg/m

60

2

Flexural strength was examined for a given mixture or
modified VC value (mix proportions 2 and 5 to 9 asshown in Table 2). The load-deflection curve wasmeasured and characteristics of SFRCC deformation foreach fiber type were clarified. Furthermore, the bondstrength of SFRCC placed on a real used asphalt
pavement surface was obtained.

80

Flexural strength (N/mm )In this section, the flexural strength, flexural toughness
and bond strength of SFRCC overlaid on an abradedasphalt pavement surface are examined. Since the needfor research on white topping as a repair method forpavement has been pointed out7), the bond strength
examination was designed to obtain basic data of new
method.

Fig. 13 Flexural strength at 28 days

M o dified VC v alue 50±5s ec

10
8
6
4
2
0
Vf=0

I-1

I-2

F-1

T ype of fiber

Fig. 16 Comparison of flexural strengthF-2

(2) Load-deflection Curve and Flexural Toughness

4
Cracking point

3
Load (tf)

I-2

2
Vf=0

1

0
0

0.5

1

1.5

2

Deflection (mm)Fig. 17 Load - Deflection curve of SFRCC and RCC

102

Flexural toughness (N/mm )particularly evident in the case of the long hooked fibers.
Figure16 shows the flexural strength of SFRCC andconventional RCC for a given modified VC value. The
differences in strength are similar to those in Fig.15, andthe strength of SFRCC is 12.5% to 52.3% higher than
RCC. It is considered that the slightly reduced
reinforcement effect in this case results from the increasein water-cement ratio required to maintain the sameconsistency. Despite this, the reinforcement effect still
remains 10% more than conventional RCC. In addition,
the relative error of strength tested the same concrete,
defined as the difference between the maximum andminimum values divided by the average, is 7.9% for
RCC and 1.1% to 8.8% for SFRCC. The relative error of
SFRCC with type I fibers was lower than that of SFRCC
with type F fibers and RCC. It seems that this is related to
the low degree of segregation of SFRCC containing typeI fibers, as shown in Fig. 10.

8
6
4
2

2

Flexural toughness (N/mm )Figure 17 shows examples of load-deflection curves for
0
SFRCC and conventional RCC beam specimens. In the
I-1
I-2
F-1
F-2
case of conventional RCC, deflection increases linearlyType of fiberwith rising load before dropping at the maximum load.
Fig.18Comparisionofflexural
toughness with different fiber types
On the other hand, the deflection of SFRCC increases
linearly but at a lower rate. Cracking occurs at a certain
load that is higher than in the case of RCC. The curve
9turns at this point, but the beam continues to support the
F-1
load until the maximum load. After the maximum load,8
the deflection increases considerably and the beam canstill support the load. It is thought that the bearing
I-1
7
capacity of SFRCC is related to the fiber pulling-out
process. Figure18 shows the toughness of SFRCC for
F-2
6
each fiber type. The toughness of SFRCC with hooked
I-2
fibers is 0.31 to 1.88 N/mm2 higher than in the case of5
indented fibers, while the toughness of SFRCC with long
6
7
8
9
10
fibers is 1.42 to 2.99 N/mm2 higher than in the case of2
Flexural strength (N/mm )short fibers. Figure19 shows the relationship between
Fig.19 Relationship between flexural strength and toughness
flexural strength and toughness for SFRCC with different
fibers. The toughness increases with increasing strength,
so toughness is affected by fiber length and shape. This result is the same as with conventional SFRC8). The bettermechanical properties of SFRCC using hooked fibers result from a difference in anchorage effect, which depends
on fiber type. In addition, the relative error of SFRCC flexural toughness was 5.6% to 16.7%, and the relative
error of type F fibers was smaller than that of type I fibers.
(3) Bond Strength with Asphalt Pavement
Figure 20 shows the bond strength for each fiber. The bond strength between the asphalt surface and the two typesof concrete, SFRCC and conventional RCC, at the age of 1, 3 and 7 days was 0.43 to 0.50, 0.57 to 0.71, and 0.72

to 0.90 N/mm2, respectively. The difference between
maximum and minimum bond strength was 0.07, 0.14
and 0.18N/mm2 at the age of 1, 3 and 7 days. No
difference in bond strength depending on fiber shape andsize can be seen. In a past investigation9), the bondstrength between SFRC and asphalt pavement was 0.4
N/mm2 and, at the age of 7 days, was independent of thepresence of steel fibers. It is therefore concluded that thebond strength of SFRCC to an asphalt pavement is notaffected by the presence of steel fibers. Some asphaltmortar is observed on the concrete surface after bondstrength testing, so the bonds in the asphalt mixture aredestroyed. Some difference in bond strength among
specimens was observed for the some age and type offiber. It is thought that the bond strength with the asphalt
pavement surface depends on the roughness of theabraded asphalt pavement, which directly affects thebond area.

1.0
1日

3日

I-2
Type of fiber

F-1

7日

2

Bond strength (N/mm )

0.8
0.6
0.4
0.2
0.0
Vf=0

I-1

F-2

Fig.20 Bond strength between concrete and asphalt pavemnet
1.0

Vf=0
I-2
F-2

2

Bond strength (N/mm )Figure 21 shows the development of bond strength in
SFRCC and conventional RCC with age. Bond strength
increased with age regardless of the presence or type offibers. In this study, the bond strength of SFRCC at 7days was 0.7 to 0.9 N/mm2, much higher than in past
investigations.

0.8

0.6

0.4

The reason for this result seems to be use of direct pullout tensile strength method an SFRC and smooth asphalt
0.2plates prepared in the laboratory in the earlier
1
3
7
investigations whereas in this study the splitting tensile
Age (days)
strength method and asphalt blocks obtained from an
Fig.21 Change in bond strength with age
actual traffic route were used. The bond strength between
SFRCC and an asphalt pavement can be expected to reach 0.7 N/mm2. Further, the relative error of bond strength
at 3 days was 26.2% for conventional RCC and 23.7% to 38.5% for SFRCC.
6. EXAMINATIONS OF FREEZING-THAWING RESISTANCE AND DRYING SHRINKAGE

In this section, the freezing-thawing resistance anddrying shrinkage of SFRCC are examined. Freezingthawing resistance was examined using mix
proportions with and without an AE agent (mixes 5 to
9 and 15 to 19) while drying shrinkage wasinvestigated with and without fibers (mixes 5 to 9) toclarify the effect of using fibers.

Air content (%)

One of the known characteristics of conventional RCC is that freezing-thawing resistance can be secured bysufficient compaction and air entrainment while the drying shrinkage of RCC is lower than that of normal
concrete. On the other hand, it is well known that the
non-AE
5AE
freezing-thawing resistance and drying shrinkage of
4
SFRC are superior to those of normal concrete.
3
2
1
0
Vf=0

I-1

I-2

F-1

F-2

Type of fiber

Fig. 22 Comparison of air content with different fiber types

100

no n -AE

Relative dynamic modulus of elasticity(% )(1) Freezing-thawing ResistanceAE(2) Drying Shrinkage Characteristics
Figure 25 shows the drying shrinkage strain, length change ratio, andloss of weight of SFRCC for each fiber type and of conventional RCC at
190 days during the drying tests. The drying shrinkage strain is 5.4×10-4

Flexural strength ratio (% )Loss of weight (% )Ultrasonic velocity (m/s)

Figure 22 shows the air content of each type of SFRCC
and of non-fiber RCC. These air contents were measured
80
by a gravimetric method. According to Fig.22, the aircontent of SFRCC and conventional RCC with an AE
agent is 0.7% to 1.5%, more than when no AE agent is
(74)
(74)
(102)
(170)
(89)
used. The unit water content when the mix contains an AE
60
agent is 2 to 5 kg/m3 less than when no AE agent is used,
as shown in Table 2. Figure 23 shows the freezingthawing test results for SFRCC and conventional RCC.
40
The relative dynamic modulus of elasticity of SFRCC
with an AE agent after 300 cycles is 68.2% to 83.0%,
5000
while that of conventional RCC is 61.0%. In the case ofth
non-AE concrete, the modulus falls below 60% at the 74
to 170th cycle for SFRCC and at the 74th for conventional
RCC, respectively. The freezing-thawing resistance ofconcrete is therefore improved by including the steel fiber
4000
and adding the AE agent. The middle and bottom figures
in Fig.23 show the ultrasonic pulse velocity of SFRCC
and the weight loss of SFRCC and conventional RCC.
The ultrasonic velocity of SFRCC is higher than that of
the RCC, and when an AE agent is included it is higher
still. This reflects the results for relative dynamic modulus.
3000
The weight losses of SFRCC and RCC with an AE agent
1.5
are more than when no AE agent is used. Of particularnote is the result that the weight loss values of RCC and
1.2
SFRCC I-1 without an AE agent are negative. This means
0.9
the concrete absorbs water as it deteriorates under testing.
This phenomenon also seems to occur locally in other0.6
types of SFRCC without an AE agent. It has been pointed
0.3
out that the frost resistance of RCC is dramatically10), 11). The degree of
reduced if compaction is insufficient0compaction of the test specimens used in this study was-0.3
98% to 99% and the effect of this variation on frost
resistance was negligible. Surface mortar was observed to-0.6
peel off in the case of non-AE concrete, but not in the
Vf=0
I-1
I-2
F-1
F-2
case of SFRCC with an AE agent. Figure 24 shows theType of fiber
relationship between flexural strength ratio and durability
Fig. 23 Freezing-thawing resistance of SFRCC and RCC
factor when an AE agent is used. The strength ratio
represents the ratio of strength after and before the freezing-thawing test.
80
Strength ratio increases with increasing durability factor and for SFRCC
70
both values are plotted in the upper right-hand corner of this figure.
60
These various results allow us to conclude that the steel fibers restrain
50
cracking under frost action and improve the frost resistance of SFRCC.
40
30
20
50

60
70
80
Durability Factor (% )90

Fig.24 Relationship between durability factor andflexural strength ratio

Shrinkage strain (×10 )6

Loss of weight (% )7. CONCLUSIONSThis study clarifies that the mix design procedure for
SFRCC to be used as pavement material is the same asfor conventional pavement concrete in that the choice ofappropriate sand percentage and fiber content is very
important. The properties of hardened SFRCC, such as
flexural strength, are remarkably better than those of
conventional RCC. The conclusions reached with respect
to mix proportion and the properties of fresh andhardened SFRCC are given below.

Age 190days-4

Length change ratio (% )for RCC, and 5.0 × 10-4 to 5.7 × 10-4 for SFRCC,
respectively. The length change ratio of SFRCC ascompared with RCC is 91.7% to 104.2%. The loss ofweight is 1.65% for RCC and 1.61% to 1.88% for
SFRCC, respectively. Thus the drying shrinkage strain of
SFRCC is almost the same as that of RCC. The weightloss of SFRCC is no less than that of RCC. It is wellknown that the higher the unit water content, the moresignificant the drying shrinkage. In this study, the unit
water content of SFRCC was 7 to 16 kg/m3 more thanthat of the RCC, as required to maintain a constantmodified VC value. So the weight loss of SFRCC is morethan that of RCC, but the drying shrinkage is almost thesame. It is therefore concluded that steel fibers are able torestrict drying shrinkage strain in a dry environment.

5
4
3
2

110

100

90

80
2.0
1.8
1.6
1.4
1.2
Vf=0

I-1

I-2
Type of fiber

F-1

F-2

Fig. 25 Comparison of shrinkage properties of SFRCC and RCC(1) The modified VC value of SFRCC is greater than that of conventional RCC, and the change in VC value foreach 1 kg/m3 change in water content is about 3 to 4 seconds, regardless of the presence of fibers. For a given
unit water content, there exists a sand percentage at which the modified VC value reaches a minimum and thecompaction degree a maximum. This sand percentage is about 40% regardless of fiber type and the modified
VC value with type I fibers or long fibers at the minimum sand percentage is higher.
(2) Regardless of fiber type, a 1.0% fiber content appears to be the optimum, taking into account the unit watercontent, compaction degree, dispersion of fibers and flexural strength. The unit water content of conventional
RCC at a modified VC value of 50 seconds is 107 kg/m3 and that of SFRCC is 123 kg/m3 and 117kg/m3 forshort and long type I fibers, and 119 kg/m3 and 114 kg/m3 for short and long type F fibers.
(3) The unit water content can be reduced by 3 to 4 kg/m3 per 0.5% increase in the dosage of a superplasticizer,
but in some cases, a reduction in flexural strength is seen due to the formation of voids if the dosage exceeds
1.5%. Thus a 1.0% dosage of superplasticizer is the optimum as determined in this study.
(4) The segregation of coarse aggregate in SFRCC is less than in conventional RCC. SFRCC with indented fibers
or short fibers has better segregation resistance.
(5) The average orientation of fibers in SFRCC is 29.1 to 30.6 degrees irrespective of fiber type, about 10 degrees
less than in conventional steel fiber reinforced SFRC compacted by immersed vibrator. As a result, theflexural strength of SFRCC is about 30% higher than that of SFRC.

(6) The flexural strength of SFRCC for a given consistency is 12.5% to 52.3% higher than that of conventional
RCC. The flexural toughness of SFRC with hooked fibers is 0.31 to 1.88 N/mm2 higher than with indented
fibers. The toughness of SFRC with long fibers is 1.42 to 2.99 N/mm2 higher than with short fibers.
(7) The bond strength of SFRCC when applied as a white topping to an asphalt pavement surface is 0.7 N/mm2 at
7 days, regardless of fiber type and size.
(8) The freezing-thawing resistance of SFRCC with an AE agent is much better than that of conventional RCC.
The relative dynamic modulus of elasticity of SFRCC after 300 cycles of testing is 68.2% to 83.0%.
(9) In spite of the higher unit water content of SFRCC for a given consistency, the drying shrinkage strain of theconcrete is almost the same as that of conventional RCC after 190 days of drying.
References[1] Benoit, F., “Fiber-Reinforced Roller-Compacted Cement Concrete (Roll fiber) for Continuous Cement
Pavement”, 8th Int’l Symposium on Concrete Roads, Theme II “Progress in Concrete Road Materials and in theConstruction Process”, pp.319-323, (1998)[2] Antonio, N., and Aziz, J., “RCC Pavement Reinforced with Steel Fibers”, Concrete International, pp. 64-69,
March, (1989)[3] Kagaya, M., Fujita, H. and Inaba, Y. “Experimental Study on Improvement of Properties of Roller-Compacted
Concrete for Pavement with Superplasticizer and Viscous Agent”, Concrete Research and Technology, JCI,
Vol.10, No.1, pp.101-108, Jan. (1999)[4] Kokubu, M., “Construction Material Experiment”, pp.118-122, (1998)[5] Japan Road Engineering Association, “Technical Specification on Roller Compacted Concrete for Pavement”,(1990)[6] Japan Concrete Institute, “Committee Report on Very Stiff Concrete”, JCI-TC-962, pp.10-14, (1998)[7] Noda, E., Kong, Y. and Kasahara, Y. “Basic Study on Ultra-thin White Topping”, Proc. Of the 2nd Conference
on Pavement Engineering, PP.45-52, (1997)[8] JSCE, “Specification on the Design and Construction of Steel Fiber Reinforced Concrete”, pp.72-73, (1983)[9] Kokubun, S., “Experimental Study on Properties and Application for Pavement of Roller-Compacted ConcreteWith and Without Steel Fiber”, Doctorate Thesis, Akita University, pp55-56, (1997)[10] Kobayashi, S., Morihama, K. and Nishikawa, M., “Experimental Consideration on Strength and Frost
Resistance of Roller-Compacted Concrete for Pavement”, Civil Engineering Journal, Vol.33, No.7, pp.29-34,(1991)[11] Kuzu, T., Hara, J., and Kokubu, K., “Study on Resistance to Freezing and Thawing of Roller-Compacted
Concrete, Proc. of JCI, Vol.12, No.1, PP.697-702, (1990)