Alexandria Engineering Journal (2015) 54, 1181–1191

H O S T E D BY
Alexandria University

Alexandria Engineering Journal

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REVIEW

Prediction of Self-Compacting Concrete homogeneity

by ultrasonic velocity
M. Benaicha a,*, O. Jalbaud a, X. Roguiez a, A. Hafidi Alaoui b, Y. Burtschell a

a
Laboratoire IUSTI UMR 7343, Polytech’Marseille, AMU, France
b
Laboratoire Ge´nie civil, Faculte´ des sciences et techniques de Tanger, Morocco

Received 2 June 2015; revised 29 July 2015; accepted 10 August 2015

Available online 30 August 2015

KEYWORDS Abstract To evaluate the filling capacity of self-compacting concrete SCC without segregation, a
Ultrasonic; technique based on the ultrasonic velocity has been adapted in order to estimate homogeneity and
Velocity; quality of concrete at very young age.
Transmission; To monitor local change in ultrasonic velocity, the process consists of using a pair of transducers
Homogeneity; at different depths of the concrete. The aim of our experimental study was to establish the relation-
Sieve stability; ship between ultrasonic velocity measured by sensors of 50 mm diameter and of 54 kHz frequency,
Segregation and homogeneity of fresh concrete. Measurements of wave propagation velocity are carried out
every half an hour on a vertical channel whose dimensions (in mm) are 160
160
700. These
measurements have been determined with three modes of transmission: direct, semi-direct and indi-
rect. The different mixtures were prepared with the same Water/Binder ratio (W/B) of 0.28. The
amount of binder is in the order of 520 kg/m3.
Comparison between ultrasonic velocity and empirical tests such as sieve stability test, slump flow
test, air content, and compressive strength, at 1 day, shows that the ultrasonic velocity can also be
very useful to evaluate homogeneity and quality of fresh concrete.
Ó 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an
open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1182
2. Experimental program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1182
2.1. Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1182
2.2. Mixture proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1183
2.3. Mixing and preparation of test specimens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1184
2.4. Ultrasonic velocity measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1185

* Corresponding author. Tel.: +33 671543968.

E-mail address: m.benaicha@hotmail.com (M. Benaicha).
Peer review under responsibility of Faculty of Engineering, Alexandria
University.
http://dx.doi.org/10.1016/j.aej.2015.08.002
1110-0168 Ó 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1182 M. Benaicha et al.

3. Test results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1187

4. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1190
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1190

1. Introduction applied to concrete is complex because it comprises various

coupled phenomena: porosity, heterogeneities of different
Static segregation process appears when coarse aggregate sep- types (cement, sand, aggregates, superplasticizer. . .) with
arates from the paste and settles down when the concrete is in dimensions ranging from nanometers to centimeters.
plastic state after casting [1]. Because the grains of different Taking into consideration the effect of superplasticizers, the
sizes behave differently, the segregation can occur further to main objective of this study is to evaluate the applicability of
any mixture movement. If the water content exceeds certain the ultrasonic velocity test to assess, using relatively large sam-
value, the frictions decrease and it occurs a separation by sed- ples, the segregation of SCC and to correlate the non-
imentation. Thus, the coarse grains settle rapidly, while fines destructive method results to empirical testing such as sieve
are swept away by the water (Fig. 1). On the other hand, in stability test, slump flow test and air content, and the destruc-
the case of high cohesive concrete mixtures, such as those con- tive method results to compressive strength at 1 day. The test
taining silica fume or VMA, even in the absence of external method is based on transducers measurements that consist in
bleed water, static segregation can still take place [2,3]. How- the monitoring, throughout a concrete column measuring
ever, to develop fundamental understanding of concrete stabil- 700 mm in height as a function of time, of ultrasonic velocity
ity, there is a few tools that can enable the generation of real- differences. The variations in ultrasonic velocities are used to
time data on the kinetics of bleeding [3,4]. derive indices that reflect stability of concrete and interpret
The coarse aggregate segregation can lead, with direct the material homogeneity. The stability deduced from the
impact on mechanical, transport properties, and durability, non-destructive ultrasonic velocity method is compared to
to heterogeneous properties of the hardened concrete. There- the stability indices determined by empirical testing.
fore, to achieve adequate mechanical properties and structural
performance, the control of segregation is critical for the mate- 2. Experimental program
rial [5–9,2,3]. Stability of fresh concrete is largely dependent on
the mixture composition and kinetic of cement hydration at 2.1. Materials
early age. The latter is greatly influenced by the supplementary
cementitious materials [8–11,2,4]. An ordinary Portland cement (CEM I 52.5 R), according to
In addition, the disadvantages resulting from the concrete European Standard EN 197-1, is used in all compositions. In
segregation are as follows: (1) low and irregular strength; (2) this study, Silica fume (SF) Sikacrete HD and Limestone Filler
gravel nests, permeable to air and water and allowing the cor- (LF) are used in order to modify viscosity. The superplasticizer
rosion of reinforcement; (3) porous regions by accumulation of (SP) is a polycarboxylate type based admixture, commercially
fine particles; (4) irregular surface, etc. branded as TEMPO 16, according to European Standard NF
For fresh concrete, segregation may occur in the following EN 934-2. The chemical composition and physical properties
cases: (1) incorrect granulometric composition of the aggre- of Portland cement and mineral admixtures are given in
gates; (2) use of large quantities of water and/or admixture Table 1.
(superplasticizer); (3) transport; (4) implementation; (5) intense
compaction, etc.
During the first hours after the implementation, the Table 1 Chemical and physical proprieties of the used
microstructure of fresh concrete remains very fragile. Unlike materials.
conventional testing methods, the ultrasonic waves do not sig-
nificantly affect the microstructure. Methods using the wave CEM LF SF SP
propagation and interaction with the concrete are among the C3S (%) 67 – – –
methods having the most potential for the non-destructive C2S (%) 12 – – –
evaluation of concrete [12–15]. The ultrasonic velocity method C4AF (%) 9 – – –
C3A (%) 9 – – –
SiO2 (%) 20.5 – 85 –
Fe2O3 (%) 2.6 0.04 – –
Al2O3 (%) 5.0 <0.4 – –
CaO (%) 65.0 – 1.0 –
MgO (%) 1.1 – – –
SO3 (%) 3.6 – 2.0 –
Loss on ignition (%) 1.2 43.10 4.0 –
NaO2 eq. (%) 0.43 – 1.0 <1.5
cl 0.01 – <0.1 <0.1
Density 3.15 2.70 2.24 1.055
Blaine (cm2/g) 4750 5550 2200 –
pH – – – 3
Figure 1 Schematic representation of segregation by Dry extract (%) – – – 24
sedimentation.
Prediction of Self-Compacting Concrete homogeneity 1183

Figure 2 Particle size distribution of sand and coarse aggregate.

Table 2 Mixture proportions.

Mixture SCC1 SCC2 SCC3 SCC4 SCC5 SCC6 SCC7 SCC8 SCC9 SCC10
3
Cement (kg/m ) 350 350 350 350 350 350 350 315 315 315
LF (kg/m3) 170 170 170 170 170 170 170 170 170 170
SF (kg/m3) – – – – – – – 35 35 35
Total cementitious materials (kg/m3) 520 520 520 520 520 520 520 520 520 520
Total water (kg/m3) 147 147 147 147 147 147 147 147 147 147
W/B 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28 0.28
Sand (0–2 mm) (kg/m3) 890 890 890 890 890 890 890 890 890 890
Coarse aggregate (6.3–10 mm) (kg/m3) 900 900 900 900 900 900 900 900 900 900
SP (kg/m3) 4.87 9.75 13 15.17 17.33 19.5 21.67 17.33 19.5 21.67

Figure 3 Experimental tool: Sonic auscultation of fresh concrete.

Local crushed sand with a maximum size of 2 mm, fineness 2.2. Mixture proportions
modulus was 2.3, specific gravity of 2.65, water absorptions of
0.81% and sand equivalent was 72.5, and gravel with a maxi- The aim of the experimental program is to evaluate the appli-
mum size of 10 mm, specific gravity of 2.65, water absorptions cability of ultrasonic velocities measurements and to assess the
of 1.4% and Los Angeles coefficient of 22 are used. The parti- segregation resistance of various SCC mixtures made with
cle size distributions of the sand and coarse aggregate are fixed sand-to-total aggregate ratio to 0.98, by mass, fixed
shown in Fig. 2. Water-to-Binder ratio (W/B) of 0.28 and binder content of
1184 M. Benaicha et al.

(a) Direct mode (b) Semi direct mode (c) Indirect mode

Figure 4 The three transmission modes of ultrasonic velocities measurements.

Figure 5 Plexiglas vertical channel used for sonic auscultation of fresh concrete.

520 kg/m3. In total, 10 SCC mixtures are designed in order to

Table 3 Rheological characterization and experimental data obtain different fresh-state properties. These 10 mixtures were
of stability. used to evaluate the sensitivity of ultrasonic velocities measure-
Mixture Slump Sieve Strength Air Visual ments to assess the stability of concrete. Stability was adjusted
flow stability at 1 day content appreciation by incorporating the various percentages of SP as well as SF
(cm) (%) (MPa) (%) and LF. The compositions of mixtures are presented in
SCC1 50 1.25 25 1.5 ++
Table 2.
SCC2 72.5 8.8 46 0.9 ++
SCC3 74 14.8 36 1.3 + 2.3. Mixing and preparation of test specimens
SCC4 75 20 33 0.6 +
SCC5 79 40 24 0.5 ± The mixing process is kept constant to supply the same homo-
SCC6 81 43.3 19 0.3 - geneity and uniformity in all mixtures. It starts by mixing all of
SCC7 83.5 51.2 13 0.35 –
the aggregates (gravel and sand) and binder for a minute using
SCC8 74 19 36 0.7 +
SCC9 77 24 25 0.5 -
a standard mixer of 40 l. Then, the mixing water is added and
SCC10 79 26 21 0.4 - mixed for an additional minute. Thereafter, the SP is added
and the concrete is mixed for an additional three minutes.
Visual appreciation of stability: ++ Very good, + good, ± Cri-
At the end of mixing, tests are immediately carried out on
tique, - Poor, – very bad.
fresh concrete to assess slump flow diameter, resistance to seg-
Prediction of Self-Compacting Concrete homogeneity 1185

Figure 6 Relationship between the sieve stability test and the air content.

Figure 7 Relationship between the sieve stability test and the compressive strength at 1 day.

Figure 8 Visual stability.

regation by Sieve segregation test and air content by concrete 2.4. Ultrasonic velocity measurements
aerometer test. The tests are performed in accordance with
EFNARC [16] standards. The test column used to evaluate The measurement principle consists in the determination of
segregation resistance is a Plexiglas mold measuring 700 mm propagation time of sound waves through a vertical channel.
in height and 160
160 mm in cross section where two trans- For this, we use a pair of transducers, one serving as a source
ducers are inserted at four heights (Fig. 3). (emitter) and the other as a receiver. According to European
The 16
32 cm cylindrical samples are used to determine standard EN 12504-4, we used 3 transmission modes [17–19]
the compressive strength after 1 day of hardening. (Fig. 4). The system is delivered with a sensor and a nominal
1186 M. Benaicha et al.

Table 4 Sonic auscultation, depending on time: measurement procedure (m/s).

Mixture Direct transmission Indirect transmission Semi-direct transmission
Side A–B Side B
1–1 2–2 3–3 4–4 r 1–4 1–3 1–2 r 2–4
30 min after casting
SCC1 1132 877 1008 871 123.99 2070 2309 3472 750.03 1424
SCC2 877 876 870 873 3.16 2583 2570 2585 8.14 1163
SCC3 862 873 875 858 8.29 2120 2145 2140 13.23 1145
SCC4 871 865 853 852 9.29 2160 2141 2153 9.61 1132
SCC5 1105 1086 890 1670 335.87 1920 2960 2816 563.49 1053
SCC6 1100 1052 780 1516 303.96 1820 2960 3240 752.15 1020
SCC7 1114 769 1047 1449 279.44 1694 1503 2469 511.58 1081
SCC8 865 864 848 852 8.54 2160 2135 2150 12.58 1098
SCC9 1020 865 902 858 75.03 2020 1241 3053 908.96 1002
SCC10 1008 908 1002 1250 146.03 1850 1212 3062 939.72 1520
60 min after casting
SCC1 1164 882 871 872 144.59 2083 2162 3125 580.14 1413
SCC2 874 873 868 869 2.94 2577 2563 2586 11.59 1164
SCC3 870 863 875 868 4.97 2140 2155 2148 7.51 1136
SCC4 868 860 863 877 7.44 2150 2148 2155 3.61 1126
SCC5 1210 1912 798 1470 467.09 1828 2660 2915 568.45 1002
SCC6 1112 1825 888 911 439.02 2142 3020 1622 706.60 1136
SCC7 1056 1134 1093 1458 184.60 1800 1801 2967 673.48 1626
SCC8 860 874 879 873 8.10 2163 2155 2148 7.51 1088
SCC9 1125 888 1202 958 145.21 2220 1985 2893 471.28 1125
SCC10 1212 1019 879 1850 428.97 2150 2518 2086 233.15 1257
90 min after casting
SCC1 995 860 876 890 61.08 1602 1484 2688 663.69 1057
SCC2 873 872 872 867 2.71 2573 2560 2580 10.15 1177
SCC3 865 858 871 878 8.52 2136 2148 2162 13.01 1152
SCC4 860 865 880 874 8.96 2130 2148 2135 9.29 1144
SCC5 1312 1854 828 1270 420.21 1928 3160 1826 742.49 1252
SCC6 1052 1862 1216 905 421.75 2014 1890 2980 596.75 1308
SCC7 1199 1515 1471 1596 172.14 2233 2567 3436 621.01 1749
SCC8 858 870 878 863 8.69 2173 2168 2152 10.97 1108
SCC9 1312 986 1422 867 262.79 2102 1885 3092 643.43 1205
SCC10 1802 1288 978 950 395.83 2088 2115 1186 528.74 1037
120 min after casting
SCC1 998 870 890 902 56.89 1590 1460 2644 649.32 1098
SCC2 870 865 872 866 3.30 2587 2580 2564 11.79 1183
SCC3 868 862 882 882 10.12 2142 2152 2170 14.19 1163
SCC4 866 862 870 878 6.83 2142 2148 2135 6.51 1124
SCC5 1845 1044 928 1370 410.61 1228 2188 1527 491.24 1082
SCC6 1520 896 985 1302 288.15 1580 2850 1210 860.17 1836
SCC7 1102 1500 1445 1580 210.59 2238 2430 3120 463.84 1805
SCC8 856 868 876 858 9.29 2164 2188 2166 13.32 1122
SCC9 1218 886 1222 886 192.84 2082 1988 2132 73.11 1005
SCC10 1715 1082 878 1050 366.94 2178 2524 1146 716.89 1147
150 min after casting
SCC1 1010 875 842 865 75.93 1582 1401 2624 660.08 1113
SCC2 873 870 872 864 4.03 2587 2578 2559 14.29 1160
SCC3 874 872 888 868 8.70 2152 2165 2176 12.01 1180
SCC4 868 866 885 884 10.14 2154 2158 2175 11.15 1148
SCC5 912 1145 1024 1288 161.50 1028 2878 3128 1147.10 1182
SCC6 998 1254 2014 1632 444.05 1680 1890 3052 739.00 1325
SCC7 1004 1478 1431 1536 242.66 2248 2249 2949 404.43 1905
SCC8 866 878 880 864 8.16 2172 2192 2178 10.26 1130
SCC9 1298 1084 1812 986 368.47 2172 1238 3035 898.73 1185
SCC10 1005 1182 988 1380 183.20 2268 2724 1246 756.85 1087
180 min after casting
SCC1 1211 1248 1137 1221 47.48 1643 2244 2457 422.13 1281
SCC2 872 877 871 873 2.63 2595 2588 2576 9.61 1171
Prediction of Self-Compacting Concrete homogeneity 1187

Table 4 (continued)
Mixture Direct transmission Indirect transmission Semi-direct transmission
Side A–B Side B
1–1 2–2 3–3 4–4 r 1–4 1–3 1–2 r 2–4
SCC3 878 888 898 887 8.18 2170 2183 2190 10.15 1205
SCC4 860 864 878 880 9.98 2146 2143 2162 10.21 1134
SCC5 1012 1225 984 1278 148.39 1127 1868 2223 559.21 1052
SCC6 1680 1312 986 1202 290.20 1850 3062 2114 637.36 1268
SCC7 1151 1289 1677 1553 240.30 2242 2162 2487 169.34 1744
SCC8 868 888 878 874 8.41 2162 2180 2164 9.87 1118
SCC9 1108 1244 912 1084 136.29 2078 1838 2338 250.07 1275
SCC10 989 1044 1215 890 136.16 2389 1708 3142 717.30 1005

Direct transmission-30 min

1800
Ultrasonic velocies (m/s)

1600
1400
1200
1000 1-1
800 2-2
600 3-3
400
4-4
200
0
SCC1 SCC2 SCC3 SCC4 SCC5 SCC6 SCC7 SCC8 SCC9 SCC10
Mixture

Figure 9 Ultrasonic velocities of various SCCs: direct transmission at 30 min after casting.

Direct transmission-180 min

1800
Ultrasonic velocies (m/s)

1600
1400
1200
1000 1-1
800 2-2
600 3-3
400
4-4
200
0
SCC1 SCC2 SCC3 SCC4 SCC5 SCC6 SCC7 SCC8 SCC9 SCC10
Mixture

Figure 10 Ultrasonic velocities of various SCCs: direct transmission at 180 min after casting.

frequency transmitter of 54 kHz, either the industry standard. The results of ultrasonic pulse velocity can be used to check
This nominal frequency limits the depth of propagation and the concrete homogeneity and to control the quality of con-
the minimum thickness of concrete that can be probed. crete products.
After a travel distance ‘‘L” and a propagation time ‘‘t” in
the material, the wave reaches the second transducer. Thus, 3. Test results and discussion
it is possible to determine the propagation velocity of sound
wave in the material: V = L/t. The results of empirical tests and visual appreciation are given
To fill the vertical channel, we used a standard V-Funnel in Table 3.
(Fig. 3). To take into account the total heterogeneity of the According to the recommendations of EFNARC [16], a
material tested, the measurements of ultrasonic velocity are self-compacting concrete should present both a slump flow
carried out on 4 points as shown in the following figure greater than or equal to 60 cm and a sieve stability less than
(Fig. 5). 15%. When sieve stability is between 15% and 30%, the stabil-
1188 M. Benaicha et al.

Indirect transmission-30 min

4000

Ultrasonic velocies (m/s)

3500
3000
2500
2000 1-4

1500 1-3

1000 1-2

500
0
SCC1 SCC2 SCC3 SCC4 SCC5 SCC6 SCC7 SCC8 SCC9 SCC10
Mixture

Figure 11 Ultrasonic velocities of various SCCs: indirect transmission at 30 min after casting.

3500

3000
Ultrasonic velocies (m/s)

2500

2000
1-4
1500
1-3

1000 1-2

500

0
SCC1 SCC2 SCC3 SCC4 SCC5 SCC6 SCC7 SCC8 SCC9 SCC10
Mixture

Figure 12 Ultrasonic velocities of various SCCs: indirect transmission at 180 min after casting.

2500
30 min 60 min 90 min 120 min 150 min 180 min
Ultrasonic velocies (m/s)

2000

1500

1000

500

0
SCC1 SCC2 SCC3 SCC4 SCC5 SCC6 SCC7 SCC8 SCC9 SCC10
Mixture

Figure 13 Ultrasonic velocities of various SCCs depending on time after casting: semi-direct transmission.

ity is considered critical and the specific tests of segregation By analyzing the results presented in Table 3, we can note
will be necessary [16,20]. that the instability risk becomes important when the slump
First, all the concretes studied have a slump flow higher flow exceeds 75 cm. In this case, we can admit that it is not nec-
than 60 cm (except SCC1). Thus, these concretes present an essary to carry out the tests for the determination of resistance
acceptable fluidity with no blockage risk. Therefore, the essen- to segregation.
tial point to be verified for all these concretes is the static seg- Table 3 shows that the concretes SCC1, SCC2, SCC3, SCC4
regation (sieve stability test). and SCC8 have a resistance to segregation less than 20%. These
The visual appreciation in terms of stability, bleeding and concretes are stable compared with other concretes.
segregation of our concretes in different tests, reveals a good In addition, the air content is a parameter that influences
stability of concretes whose value of sieve stability is less than the bleeding of concrete. More a mixture contains a large air
or equal to 20%. volume, less it is viscous. Indeed, the volume of paste available
Prediction of Self-Compacting Concrete homogeneity 1189

Direct transmission
1600

1400

Ultrasonic velocity (m/s)

1200

1000

800

600
30 min 60 min 90 min
400
120 min 150 min 180 min
200

0
8.8 14.8 19 20 24 26 40 43.3 51.2
Sieve stability (%)

Figure 14 Ultrasonic velocities of various SCCs depending on sieve stability.

to improve flow a mixture also depends on the air content [21]. In direct transmission mode, the concretes SCC2, SCC3,
Therefore, SCC which contains a value of air entrained higher SCC4, and SCC8 are very stable compared with other con-
than 0.6%, is of a very weak viscosity compared with other cretes. Regardless of the measuring point and time of ausculta-
mixtures and it represents a very important stability (less than tion, the ultrasonic velocities of these concretes remain almost
or equal to 20%). constant.
By analyzing the results presented in Fig. 6, we can note In indirect transmission mode, the concretes SCC2, SCC3,
that the instability risk increases when the air content SCC4, and SCC8 are very stable compared with other
decreases. concretes. Regardless of the measuring point and time of
As regards the compressive strength, at 1 day, we note that auscultation, the ultrasonic velocities of these concretes remain
when the stability decreases the compressive strength increases almost constant.
(Fig. 7), except for SCC1. This later contains very high air By analyzing the results presented in Figs. 9–13, it is possi-
content (1.5%) and a slump flow of about 50 cm (non-self- ble to make qualitative comparisons, based on homogeneity
compacting concrete), and the resistance becomes therefore very
low. Fig. 8 shows the presence of voids in the case of SCC1.
On the basis of the empirical test results and visual appre-
ciation of stability, we can conclude that the concretes
SCC2, SCC3, SCC4 and SCC8 represent a very satisfactory
stability compared to other concretes.
To confirm this stability conclusion and to validate the pro-
posed approach (ultrasonic velocity on fresh concrete), ultra-
sonic velocity measurements and its standard deviation r
applied on all SCCs are summarized in Table 4.
The velocity variation measurements are carried out every
half hour, until three hours after the casting phase.
Table 4 shows that, at 30 min after casting, the ultrasonic
velocity remains almost constant in the case of SCC2, SCC3,
SCC4 and SCC8. The variation between their values does
not exceed 20 m/s and 25 m/s for direct and indirect transmis-
sion mode, respectively. For these concretes, standard devia-
tion r does not exceed 10 m/s and 14 m/s for direct and
indirect transmission mode, respectively. For other concretes,
the variation of velocity values exceeds, in some cases,
700 m/s and 1800 m/s for direct and indirect transmission
mode, respectively. In some cases, standard deviation r
exceeds 300 m/s and 900 m/s for direct and indirect transmis-
sion mode, respectively.
In general, Table 4 also shows that the SCC2, SCC3, SCC4
and SCC8 have values of ultrasonic velocity almost constant
regardless of the transmission mode used and the auscultation
time after the casting phase. For these concretes, standard
deviation r does not exceed 11 m/s and 15 m/s for direct and
indirect transmission mode, respectively.
From Table 4 and Figs. 9–13, we can conclude that SCC2,
SCC3, SCC4 and SCC8 present a satisfactory stability com- Figure 15 Velocity propagation in side [1–1] and [4–4]: direct
pared with other concretes. transmission mode.
1190 M. Benaicha et al.

Table 5 Homogeneity coefficient of various SCCs depending on time after casting.

Mixture Homogeneity coefficient Hc for direct transmission mode
30 min after 60 min after 90 min after 120 min after 150 min after 180 min after
casting casting casting casting casting casting
SCC1 1.30 1.33 1.12 1.11 1.17 0.99
SCC2 1.00 1.01 1.01 1.00 1.01 1.00
SCC3 1.00 1.00 0.99 0.98 1.01 0.99
SCC4 1.02 0.99 0.98 0.99 0.98 0.98
SCC5 0.66 0.82 1.03 1.35 0.71 0.79
SCC6 0.73 1.22 1.16 1.17 0.61 1.40
SCC7 0.77 0.72 0.75 0.70 0.65 0.74
SCC8 1.02 0.99 0.99 1.00 1.00 0.99
SCC9 1.19 1.17 1.51 1.37 1.32 1.02
SCC10 0.81 0.66 1.90 1.63 0.73 1.11

U½side 1–1
Hc ¼
U½side 4–4
where U[side 1–1] and U[side 4–4] represent propagation
velocity in the [1–1] and [4–4] zone, respectively (Fig. 15).
Table 5 summarizes the Homogeneity coefficient of the var-
ious SCC mixtures evaluated from the ultrasonic velocity.
The concretes SCC2, SCC3, SCC4, and SCC8 represent a
coefficient equal to 1 ± 0.2. Consequently, concrete mixtures
with homogeneity coefficient between 0.98 and 1.02, and lower
than 0.98 or higher than 1.02 can be considered to have high
and low stability, respectively (Fig. 16).

Figure 16 Correlation between stability and homogeneity 4. Conclusion

coefficient.
Segregation is the separation of the constituent materials of
fresh concrete that can occur whenever it is implemented or
and quality study, between concretes by means of ultrasonic under the effect of gravity at rest. In these cases, the sonic aus-
velocity at fresh state. For the same concrete type, the results cultation on fresh concrete can be used to check the homo-
obtained, during our work, allow to verify the evolution of geneity of concrete and to control its quality. The results
ultrasonic velocity depending on time. show the effectiveness of the proposed approach.
At a given time, we can also note that the instability risk of In this study we found that the concretes SCC2, SCC3,
concrete is manifested during the evolution of its ultrasonic SCC4, and SCC8 are very stable compared with others.
velocity. The concretes SCC2, SCC3, SCC4, and SCC8 are Regardless of the measuring point, time of auscultation and
very stable compared with other concretes. Regardless of the mode of transmission used, the ultrasonic velocities of these
measuring point, time of auscultation and mode of transmis- concretes remain almost constant. The results found by ultra-
sion used, the ultrasonic velocities of these concretes remain sonic velocity and those found by empirical tests are similar.
almost constant. In the laboratory, instead of using all empirical tests, we
The results found by this approach and those found by can use ultrasonic velocity to evaluate the static stability of
empirical tests (Table 3) are similar. Both methods confirm self-compacting concrete.
the instability of SCC1, SCC5, SCC6, SCC7, SCC9 and
SCC10 with regard to the segregation. References
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