Fracture Energy of Roller Compacted Concrete Pavements Author 1: Emin Şengün, Asst. Prof. Dr., Ankara Yildirim Beyazit University, Ankara, Turkey

Author 2: Burhan Alam, Dr. Lecturer, Middle East Technical University, Ankara, Turkey

Author 3: Reza Shabani, Dr., Middle East Technical University, Ankara, Turkey

Author 4: İ. Özgür Yaman, Prof. Dr., Middle East Technical University, Ankara, Turkey

For the corresponding author: esengun@ybu.edu.tr

KEYWORDS: Roller compacted concrete pavement, bending properties, toughness, fracture energy, field compaction procedure.

Conflict of Interest: None

1. ABSTRACT

This study is set out to examine the bending, toughness and fracture energy of RCC pavements produced by double drum vibratory hand roller (DDVHR) to simulate the real performance of RCC in the laboratory environment. To this end, four different binder dosages (200, 300,400, and 600 kg/m3) and two different aggregate gradations (Dmax 12 and 19 mm) were selected to investigate the effect of mixture design on bending, toughness and fracture energy of RCC mixtures. The different mixtures were poured into a large pavement mold (LPM), which was fabricated in laboratory, and compacted by DDVHR. After that, in order to determine the bending, toughness and fracture energy of RCC mixtures, LPM were cut to beam specimens with sizes according to Japan Concrete Institute (JCI). In addition, cores were taken from LPM to compare 28 days’ compressive strengths and compaction ratios of the mixtures. At the end of the study, contrary to expectations, the fracture energies for all RCC mixtures except one combination were very close to each other. The increase in cement dosage or the maximum aggregate size did not lead to a significant change in the fracture energy. The mixture that was developed to obtain a high performance RCC appeared to have the lowest fracture energy. Above all, the compaction ratio of the mixtures was effective in the all results.

2. INTRODUCTION

Roller compacted concrete (RCC) can be compacted by using the heavy vibrating steel drum rollers and rubber tired rollers in the fresh state and be produced from the same components as the traditional concrete. Those components are the well graded aggregates, the cementitious materials and water, yet, RCC has different mixture proportions [1]. One of the most important advantages of RCC pavements compared to the traditional ones is the economic benefit due to their lower cement content and rapid construction. Another advantage of RCC pavements is that they can be produced by the same equipment used for the traditional flexible asphalt pavements. This equipment are widely used in rural and urban road constructions. Since the 1980s, especially in road construction, more than 100,000 m2 of RCC pavements have been constructed in France, Germany, Norway, Sweden, Finland, Denmark, Germany, Austria, Argentina and Japan. However, in the USA alone, RCC pavements have exceeded 12 million square meters starting from 2011 [2].

For RCC pavements, the choice of the correct layer thickness is the key for a successful field application. This thickness is largely dependent on the mechanical and fracture properties of the RCC mixture as well as its fatigue behavior. The literature studies on RCC primarily concentrate on the design of the mixtures and the effects of mixture parameters on the physical and mechanical performance [1,3–8]. However, the studies made on RCC’s fracture properties are very limited in the literature [9][10][11]. In these studies, the fracture energy was determined according to RILEM procedure (1985) [12] developed by Hillerborg [13]. According to this procedure, the deflection at the midpoint of the beam should be referenced to find the fracture energy, while the researchers have started to refer to the crack mouth opening displacement (CMOD) in order to obtain more accurate results. However, in 2003, a standard was developed by the Japan Concrete Institute (JCI-S-001-2003) to determine the fracture energy of concrete [14]. According to this standard, fracture energy can be determined by CMOD controlled test on notched beam samples with standard dimensions. On the other hand, it has been observed in the studies conducted until now that this standard was not used to determine the fracture energy of RCCs. One aim of this study is to find the fracture energies of RCC mixtures instead of the traditional RILEM procedure.

3. RESEARCH SIGNIFICANCE

In this study, four different binder dosages and two different aggregate gradations were selected to investigate the effect of RCC mixture design on RCC fracture energy and toughness. A total of seven different mixtures were poured into large pavement mold (LPM) and compacted with vibratory plate compactor (VPC) and double drum vibratory hand roller (DDVHR) to simulate field conditions. The beam specimens cut from the LPM were used to investigate bending, toughness and fracture energy of the mixtures. In order to determine fracture energy of RCC mixtures, Japan Concrete Institute (JCI- S-001-2003) procedure was applied on notched beam specimens. In addition, cores were taken from LPM to obtain 28 days compressive strengths and

compaction ratios of mixtures. At the end of the study, the effects of the changes in the contents of RCC mixtures on the bending properties, toughness, and fracture energy were investigated.

4. EXPERIMENTAL STUDY

Mixture Design and Sample Preparation

Ordinary type portland cement CEM I 42.5 R and crushed limestone aggregates were used in all the mixtures. The mixtures were produced with three different cement contents, 200 kg/m3 (low), 300 kg/m3 (medium), and 400 kg/m3 (high), and two different maximum aggregate sizes 12 mm and 19 mm, to investigate the effect of the mixture design on the bending properties and fracture energy of RCC specimens. One additional mixture was prepared using a binder dosage of 600 kg/m3 and a maximum aggregate size of 12 mm, to represent the behavior of high performance RCC. The desired gradation of the aggregate combination was determined by considering the recommended RCC gradation band from the American Concrete Pavement Association (ACPA) guide specification [15], as shown in Figure 1.

0

10

20

30

40

50

60

70

80

90

100

0 0.5 1 1.5 2 2.5 3 3.5 4

Pass

ing

(%)

Sieve Size (mm)0.3 1.18 2.360 4.75 9.5 12.5 19 25

Blended Aggregate(Dmax 19 mm)

ACPA-RCC Limits

0.45 Density Line

0

10

20

30

40

50

60

70

80

90

100

0 0.5 1 1.5 2 2.5 3 3.5

Pass

ing

(%)

Sieve Size (mm)4.75

ACPA-RCC Limtis

19

0.45 Density Line

Blended Aggregate(Dmax 12 mm)

(a) (b)

Figure 1. The combined aggregate gradations (a) Dmax 12 mm (b) Dmax 19 mm.

The water amount was determined based on the experimental study conducted by Sengun et al. (2019)[18] [19]. In that study, a total of twenty RCC mixtures designs were produced using two different aggregate gradations (Dmax 12 and 19 mm), two different binder dosages (200 and 400 kg/m3), and five different water amounts; 3-4-5-6-7%. Different laboratory compaction methods were applied to those mixtures, and the relationships between strength, density, and compactability were examined. Figure 2 shows the typical density-water amount relationships for 200 and 400 kg/m3 binder dosage mixtures. At the end of that study, the experimental results showed that ideal RCC mixtures could be achieved with water amount of 5-6% and Vebe times in the range of 30 ± 10 seconds. Furthermore, a Vebe time of 30 to 40 seconds suggested by ACI

309 for RCC concrete pavements was considered to be the acceptable range [16,17]. In this study, mixtures that had similar Vebe times of 30 ± 10 seconds were chosen to simulate field consistency conditions.

1800

1900

2000

2100

2200

2300

2400

2 3 4 5 6 7 8

Dry

den

sity

(kg/

m3 )

Water amount (%)

C-200kg/m3 and Dmax- 12 mm

1800

1900

2000

2100

2200

2300

2400

2 3 4 5 6 7 8

Dry

den

sity

(kg/

m3 )

Water amount (%)

C-200kg/m3 and Dmax- 19 mm

1800

1900

2000

2100

2200

2300

2400

2 3 4 5 6 7 8

Dry

den

sity

(kg/

m3 )

Water amount (%)

C-400kg/m3 and Dmax- 12 mm

1800

1900

2000

2100

2200

2300

2400

2 3 4 5 6 7 8

Dry

den

sity

(kg/

m3 )

Water amount (%)

C-400kg/m3 and Dmax- 19 mm

V. Hammer

Figure 2. Relationship between density and water amount.

In Table 1, the mixture proportions of the prepared seven six RCC mixtures ware presented, where the mix ID represents, respectively, the binder type, the cement dosage, the maximum aggregate size, and the water amount percentage. For the seventh mixture, a blend of fly ash and silica fume was added in the ratios of 45% and 5 % by the weight of cement to obtain high performance RCC mixture. Based on those combinations, 20 RCC mixtures were designed following the classical weight/volume calculations of concrete mixture proportioning described by CP Tech Center RCC guideline [1].

Vebe test (ASTM C1170) was performed to determine the RCC consistency. After determining the Vebe time for the mixture, and in order to simulate the vibratory roller used in RCC pavement compaction in field, first, a VPC with bottom plate dimensions of 35×45 cm, a weight of 100 kg, and a vibrating force of 18 kN was used, then a DDVHR was run over the LPM (85×200×15 cm3). The DDVHR used in this work weighed 700 kg and had a capacity of 3900 vibrations per minute provided by two vibrating cylinders with a width of 65 cm and a diameter of 40 cm each. In order to obtain the compressive strengths (ASTM C39 [20]) at 28 days, cores with dimensions of Ø15x15 cm were taken from LPMs. In addition, the compaction ratios of the 28 days cores were calculated by dividing the hardened densities of the cores over the theoretical air free density [19]. Beam samples with the dimension specified in JCI procedure [14] were cut out of the LPMs to determine the bending properties, toughness, and fracture energy of the RCC mixtures. After that, the notches specified in JCI procedure were made in the beam specimens by

using a suitable cutting machine. The preparation steps of the beam specimens from LPMs are shown in Figure 3.

Table 1 RCC mixture proportions (kg/m3).

No Mix ID C FA SF Dmax

(mm)Wate

r

Aggregates

W/C C (%) S/A0-5 mm

5-12 mm

12-19 mm

TAFD

1 C200-D12 W5 200 - - 12 117 974 1157 - 0.58 8.58 0.55 2498

2 C200-D19 W5 200 - - 19 117 946 866 325 0.58 8.56 0.45 2504

3 C300-D12-W5.5 300 - - 12 127 1095 922 - 0.42 12.94 0.55 2495

4 C300-D19-W5.5 300 - - 19 128 896 820 308 0.43 12.91 0.45 2501

5 C400-D12-W5.5 400 - - 12 128 1048 883 - 0.32 17.16 0.55 2510

6 C400-D19-W5.5 400 - - 19 129 857 785 294 0.32 17.12 0.45 2515

7 B600-D12-W8.5 400 180 20 12 169 863 727 - 0.28 27.39 0.55 2480

Note C: cement, FA: Fly Ash, SF: Silica Fume, W/C: Water to cementitious ratio, C %: cementitious ratio, S/A: Fine aggregate to total aggregate, TAFD: Theoretical air free density.

Figure 3. Preparation of beam specimens.

a0 = 30 mm

P

b=100 mm

d=100 mm

L=350 mm

n0 ≤=5 mm

S=300 mm

D≥4da D≥4da a0 =0.3D

 

L≥3.5D 

S≥3.0D 

b≥4da 

Determination of Fracture Energy-JCI procedure

In the method developed by the Japanese Concrete Institute (JCI-S-001-2003) [14], the load-CMOD curves of notched beams under third-point bending test were used to determine the flexural strength, toughness, and total fracture energy of RCC specimens. The specimen sizes and loading setup for the procedure are shown in Figure 4.

Figure 4 Specimen geometry and loading setup in JCI-S-001-2003.

Third-point bending fracture test was conducted at a constant crack mouth opening displacement (CMOD) rate by using servohydrolic universal testing machine, while a video extensometer was also used for accurate non-contact displacement measurements (Figure 5). The loading rate was selected as 0.05 mm/min. The measurement of the load and CMOD continued from the beginning of testing until the specimen completely failed.

Figure 5. Determination of fracture energy of RCC mixtures by three-point bending test applied on notched beam according to JCI-S-001-2003 standard.

At the end of the test, the following equation (Eq. 1) was used to calculate the fracture energy (GF) according to the related standard.

GF=0.75×W 0+0.75×( SL m1)×g×CMODc

A lig(1)

where; GF= Fracture Energy (N/m), W0= area below CMOD curve up to the rupture of the specimen (N.mm), m1=specimen weight (kg), S= span length (mm), L= total length of specimen (mm), g= gravitational acceleration (9.807 m/s2), CMODc= crack mouth opening displacement at the time of rupture (mm), Alig= area of broken ligament (mm2).

Flexural strengths of notched concrete beams are calculated by using below equation [21].

MRnotched beam=3.Pmax . S

2.b .(h¿¿ sp)2(2)¿

where; MR= modulus of rupture, flexural strength (MPa), Pmax= maximum load during the test (N), S=span length (mm), b=width of the specimen (mm), hsp= distance between tip of the notch and top of cross section (mm).

5. RESULTS

In order to determine the total fracture energies of the RCC mixtures using Eq.1, a third-point bending test was applied on notched beam specimens, as shown in Figure 5, according to the JCI-S-001-2003 procedure [14]. The average load versus CMOD curves for each RCC mixture are shown in Figure 6.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Load

(N)

CMOD (mm)

B600-D12

C400-D12

C400-D19

C300-D12

C300-D19C200-D19C200-D12

Figure 6 Average Load-CMOD curves for each RCC mixture obtained by JCI procedure.

The results of average 28 days compressive strengths (ASTM C39 [20]) and compaction ratios obtained by core samples as well as the results of three-point fracture tests are presented in Table2. Each result is the average of at least four specimens.

Table 2 Average values of compressive, flexural strength, toughness and fracture energy of RCC mixtures.

MIX IDVebe time (sec)

CR(%)

Comp. Strength (28 days)

(MPa)

Test Parameters from JCI Procedure (40±10 days)

Pmax

(kN)CMODc

(mm)MR

(MPa)W0

(N.mm)GF

(N/m)C200-D12-

W5 32 95.1 26.9 [4.9]

4.7[11.5]

0.88[43.9]

4.0[6.8]

649[25.2]

72.3[22.7]

C200-D19-W5 32 97.0 29.0

[9.3]5.6

[16.5]0.69

[31.1]4.7

[9.3]674

[27.7]72.4

[18.7]

C300-D12-W5.5 22 98.6 40.6

[6.6]5.3

[21.0]0.81

[24.2]5.1

[9.8]783

[26.8]92.0

[20.1]

C300-D19-W5.5 20 97.8 43.3

[7.1]4.7

[12.5]0.79

[19.1]4.1

[10.4]669

[22.1]77.0

[17.7]

C400-D12-W5.5 35 95.3 39.2

[3.9]5.4

[18.3]0.78

[15.6]4.8

[13.4]639

[16.0]73.2

[13.0]

C400-D19-W5.5 32 94.6 31.3

[4.3]4.3

[10.8]0.94

[26.2]3.8

[9.1]628

[17.2]72.1

[15.1]

B600-D12-W8.5 21 99.0 48.0

[3.7]8.6

[9.5]0.75

[15.8]6.3

[2.7]593

[20.5]63.8

[10.7]Note: CR: compaction ratio, fc: compressive strength at 28 days, Pmax: maximum load during the fracture test, CMODc: crack mouth opening displacement at the time of rupture, MR: flexural strength obtained by fracture test, W0: toughness (area below CMOD curve up to the rupture of the specimen), GF: total fracture energy.

Moreover, the relationship between total fracture energies and binder dosages are shown in Figure 7.

150 200 250 300 350 400 450 500 550 600 6500

10

20

30

40

50

60

70

80

90

100

f(x) = − 0.00162037289033194 x + 74.3092715761099R² = 0.00350160310277936

f(x) = − 0.0385884101073923 x + 89.8057050555662R² = 0.305935916697267

Binder Dosage (kg/m3)

Tota

l Fra

ctur

e En

ergy

(N/m

)

Figure 7 Relationship between total fracture energy and binder dosage.

As it can be seen from Table 2 and Figure 7, all RCC mixtures (except C300-D12) exhibited similar fracture energies (GF). Contrary to expectations, the increase in cement dosage or the maximum aggregate size did not lead to a significant change in the fracture energy. It should be kept in mind that C300-D12 and C400-D12 mixtures with quite different compaction ratios affected all the investigated relationships. The seventh mixture that was developed to obtain a high performance RCC appeared to have the lowest fracture energy. Increasing the brittleness of the material is thought to cause a decrease in toughness and fracture energy. Moreover, since the test was performed by controlling the crack mouth opening displacement under a low loading rate, the specimens were not completely failed at the end of the fracture test because the load amount needed to continue the test was close to zero. When the cracks reached a certain size, the specimen remained stable and its dead weight was almost enough to increase the value of the CMOD. For this reason, the load-CMOD graph exhibited significant differences between the specimens in the tail section (Table 2-CMODc). On the other hand, in the Eq.1 of the JCI-S-001-2003 procedure, the toughness (W0) and crack mouth opening displacement (CMODc) values were taken when a complete failure occurred in the specimen. In this study, the complete failure for this test was considered when the load goes down to 1% of the ultimate load.

When the strengths results are examined, it is seen that the mixtures with 400 kg/m3 give lower strengths contrary to expectations (Figure 8). However, as it is known, the expected strengths of the RCC mixtures can only be reached if sufficient compaction is achieved. In the study conducted by Sengun et al. (2019) [19] , it is stated that a compaction ratio of at least 96% is required for the RCC mixtures to reach sufficient strengths, especially in high binder dosage mixtures. The compaction ratio can varies depending on the mixture design, the consistency of mixture, the compaction process (e.g. type of compaction equipment, applied energy, time period, number of passes etc.) and quality of work. In this study, it is seen that mixtures of 300

kg/m3 binder dosage with higher compaction ratios have higher strengths than 400kg/m3 binder dosage mixtures with lower compaction ratios.

100 200 300 400 500 600 7000

10

20

30

40

50

60

f(x) = 0.0113569804372 x + 31.13196979323R² = 0.0217180023248943

f(x) = 0.045990789639 x + 21.40765906748R² = 0.80849086356165

Dmax-12 mm

Binder Dosage (kg/m3)

Com

pres

sive

Stre

ngth

(MPa

)

100 200 300 400 500 600 7000.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

f(x) = − 0.004501296363 x + 5.543152485709R² = 0.946590828717248

f(x) = 0.005226000651 x + 3.068416697408R² = 0.849540240745995

Dmax-12 mm

Binder dosage (kg/m3)Fl

exur

al s

treng

th-J

CI-

(MPa

)

CR 94.6%

Figure 8 Relationship between strengths and binder dosages.

Finally, typical fractured surfaces of the specimens obtained for each mixture are given in Figure9.

CR 94.6%

Figure 9 Typical fractured surface of the samples at the end of the experiment .

6. CONCLUSION AND DISCUSSION

In this study, the compressive strength, bending, toughness, and fracture energy of seven different RCC mixtures were determined and the effects of mixture design on those parameters were investigated. The mixtures were designed with four different binder ratios ranging from 200 kg/m3 to 600 kg/m3, and two different aggregate gradations with a maximum aggregate size of 12 mm and 19 mm. All RCC mixtures were compacted in an LPM with dimensions of 15×85×200 cm3 by using a DDVHR to represent the actual field compaction procedures. The 28 days compressive strength and compaction ratios were obtained through cores taken from LPM. Third-point bending test was applied to notched beams to determine the bending, toughness, and fracture energy by using JCI procedure [14]. The conclusions are as follows.

The compaction ratio of mixtures had a large effect on all the results. In this study, 300 kg/m3 binder dosage mixtures with higher compaction ratio showed better strengths than 400 kg/m3 binder dosage mixtures with lower compaction ratio.

All RCC mixtures except for C300-D12 exhibited similar fracture energies (~75 N/m). The seventh mixture that was developed to obtain a high performance RCC appeared to have the lowest fracture energy (63 N/m). Increasing the brittleness of the material is thought to cause a decrease in toughness and fracture energy.

Some difficulties were encountered when determining the fracture energy with the JCI procedure. Since the fracture energy test was performed by controlling the crack mouth opening displacement by applying a low rate displacement, the specimens were not completely failed at the end of the fracture test when the applied load reached a value near to zero. However, this did not have a notable effect on the fracture parameters, since the test lasted when the load went down to 1% of the ultimate force.

7. ACKNOWLEDGEMENTS

This study is conducted under a research project on RCC pavement (Project no. 116M523) funded by The Scientific and Technological Research Council of Turkey. The authors acknowledge the graduate student Mustafa Soytorun.

8. REFERENCES

[1] D. Harrington, F. Abdo, W. Adaska, C. V Hazaree, H. Ceylan, F. Bektas, Guide for roller-

compacted concrete pavements, (2010).

[2] İ.Ö. Yaman, H. Ceylan, Silindirle sıkıştırılmış beton yollar, T.H.B.B Hazır Bet. Derg.

(2013) 69–82.

[3] F. Vahedifard, M. Nili, C.L. Meehan, Assessing the effects of supplementary cementitious

materials on the performance of low-cement roller compacted concrete pavement, Constr.

Build. Mater. 24 (2010) 2528–2535.

[4] C. Hazaree, H. Ceylan, K. Wang, Influences of mixture composition on properties and

freeze–thaw resistance of RCC, Constr. Build. Mater. 25 313-319, (2011).

[5] M. Madhkhan, R. Azizkhani, M.E. Torki Harchegani, Effects of pozzolans together with

steel and polypropylene fibers on mechanical properties of RCC pavements, Constr.

Build. Mater. 26 102-112, (2012).

[6] C. Chhorn, S.W. Lee, Consistency control of roller-compacted concrete for pavement,

KSCE J. Civ. Eng. 211757-1763, (2016).

[7] S.A. Ghahari, A. Mohammadi, A.A. Ramezanianpour, Performance assessment of natural

pozzolan roller compacted concrete pavements, Case Stud. Constr. Mater. 7, 82-89

(2017).

[8] S.H. Song, S.W. Lee, A Study on the Gradation Effect of the Property of Roller

Compacted Concrete Pavement, Int. J. Highw. Eng. 17, 49–58 (2015).

[9] J. LaHucik, S. Dahal, J. Roesler, A.N. Amirkhanian, Mechanical properties of roller-

compacted concrete with macro-fibers, Constr. Build. Mater. 135 440–446, (2017).

[10] J. LaHucik, J. Roesler, Field and Laboratory Properties of Roller-Compacted Concrete

Pavements, Transp. Res. Rec. J. Transp. Res. Board. 33–40, (2017).

[11] E. Ferrebee, A. Brand, A. Kachwalla, J. Roesler, D. Gancarz, J. Pforr, Fracture properties

of roller-compacted concrete with virgin and recycled aggregates, Transp. Res. Rec. J.

Transp. Res. Board. 128–134, (2014).

[12] D.R. RILEM, 50-FMC Committee Fracture Mechanics of Concrete,“Determination of the

fracture energy of mortar and concrete by means of three-point bending tests on notched

beams,” Mater. Struct. 85 285–290, (1985).

[13] A. Hillerborg, The theoretical basis of a method to determine the fracture energyG F of

concrete, Mater. Struct. 18 291–296 (1985).

[14] Japan Concrete Institute Standard (JCI-S-001-2003), Method of test for fracture energy of

concrete by use of notched beam, 2003.

http://www.jci-net.or.jp/j/jci/study/jci_standard/JCI-S-001-2003-e.pdf (accessed

November 11, 2018).

[15] ACPA (American Concrete Pavement Association), Roller-Compacted Concrete Guide

Specificaiton, 2014. http://www.acpa.org/wp-content/uploads/2014/11/ACPA-Roller-

Compacted-Concrete-Guide-Specification-Version-1.2.pdf (accessed October 17, 2018).

[16] ACI 309.5R-00, Compaction of Roller-Compacted Concrete, 2000.

http://civilwares.free.fr/ACI/MCP04/3095r_00.pdf (accessed October 27, 2017).

[17] E. Sengun, M.A. Aykutlu, R. Sahabani, B. Alam, I.O. Yaman, Comparison of Laboratory

Practices for Roller Compacted Concrete Pavements, in: 13th Int. Symp. Concr. Roads,

Berlin, Germany, 2018.

[18] E. Şengün, Effects of mixture design parameters and compaction methods on the

properties of roller compacted concrete pavements, PhD Thesis, Middle East Technical

University, 2019. http://etd.lib.metu.edu.tr/upload/12624703/index.pdf.

[19] E. Şengün, B. Alam, R. Shabani, I.O. Yaman, The effects of compaction methods and mix

parameters on the properties of roller compacted concrete mixtures, Constr. Build. Mater.

228 116807 (2019).

[20] ASTM C39 / C39M-18, Standard Test Method for Compressive Strength of Cylindrical

Concrete Specimens, West Conshohocken, PA, 2018.

[21] RILEM TC 162-TDF, Test And Design Methods For Steel Fibre Reinforced Concrete,

2002.