ISRN Civil EngineeringVolume 2013 (2013), Article ID 369387, 7 pageshttp://dx.doi.org/10.1155/2013/369387

Research Article

Pulse Velocity Measurements in Fly Ash Blended Cementitious Systems Containing 43 Grade Cement

V. M. Sounthararajan and A. Sivakumar

Structural Engineering Division, School of Mechanical and Building Sciences, VIT University, Vellore, Tamil Nadu 632014, India

Received 9 March 2013; Accepted 18 April 2013

Academic Editors: I. G. Raftoyiannis and I. Smith

Copyright © 2013 V. M. Sounthararajan and A. Sivakumar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Investigations on the different supplementary cementitious materials based on the hardening properties and the optimized dosage in cementitious systems find the right choice of pozzolanic material. It is essential to combine various additive/admixtures in concrete in proper proportions to maximize the benefits resulting in cost savings in construction. In the recent years, production technology and composition of hydraulic cements affect the setting and early age behavior of cementitious material. The addition of fly ash in cement is one viable technology to derive maximum benefits in terms of the economy and improved pozzolanic reaction. Ultrasonic pulse velocity testing is a feasible method for evaluating the hardening properties of cementitious materials. In this study, an attempt was made to derive the engineering basis for understanding the development of hardness during hydration of fly ash (FA) based cementitious systems. The tests conducted using pulse velocity technique proved to be an effective method for characterizing the early strength gain properties of different cementitious systems.

1. Introduction

During recent years many variations have been made in the production technology, and its performance exceeded expectations. In addition, mineral admixtures like fly ash have been combined with Portland cement content improve the demonstrated excellent performance, both in mechanical as well as in durability aspects [1, 2]. The addition of pozzolanic admixtures converts the leachable calcium hydroxide into insoluble nonleachable calcium hydroxide in the cementitious products [3]. One such effect relates to the setting and early strength gain of concrete. Such delays are not desirable on site as tasks cannot be completed as per schedule. It is well known that chemical reactions between cement and water react with cement pastes, mortars, and concrete from fluids to rigid bodies [4]. The term setting has been used to describe the onset of rigidity in fresh cement pastes, mortar, and concrete. The setting phenomena are altered some factors, such as water/binder (w/b) ratio, curing regime temperature, and admixtures [5–8]. Thermodynamically, the initial set is marked by a rapid temperature rise, which corresponds roughly to the beginning of the main factor of chemical reactions that temperature rise will reach a maximum rate around the final set [9]. Chemical admixture becomes inevitably an important component to make a high early strength of hardened concrete [10]. The objective of this study is to establish the scientific and engineering bases for understanding to improve the hardness during the hydration of cement-based materials by using the Vicat apparatus for determining the normal consistency and setting time for cement and measuring the pulse velocity through concrete using ultrasonic equipment. The detailed cement compositions of different percentage with different mixture proportions were studied.

2. Preparation of Specimens

Ordinary Portland cement 43 grade available in the local market was used in investigations. The cement used has been tested for various properties as per IS 4031-1988. The consistency of cement was 30% both ordinary Portland cement and Portland pozzolana cement and normal river sand passing through 2.36 mm IS sieve and conforming (IS 383-1978) to zone III and fineness modulus of 2.89 was used as fine aggregate and normal potable water was used. Mineral admixture like fly ash class F were used for pozzolanic material was greatly increased the workability at different level of replacement was 10%, 20%, 30%, 40%, and 50% by weight of cement and consistency of fly ash was 48%. Cement mortar mixture proportions were 1 : 3 (one part cement which is equally divided into number of percentage by replacement of cement and used as fly ash) and dosage of accelerator 1%, 2%, and 3% by weight of binder material and size of specimens as per standard  mm were prepared by using a special steel mould designed and cement mortar was made by mixing of water, cement with or without fly ash and also accelerator, an each mix three cubes were cast and tested. The glass plate mould fabricated the size of the mould  mm. The fluidity of cement paste after finishing the top surface was measured using the ultrasonic pulse velocity (m/sec) by the direct transmission method and the arragement was securred to ensure uniform contact with the transducer and the surface of the plexiglass mould.

3. Results and Discussions

3.1. Measurement of Ultrasonic Pulse Velocity Test in Cement Mortar

The cement mortar specimens were tested for 1, 3, 7, 14, and 28 days after sufficient curing in water tank, tested on the smooth surface of the both sides, fixed the length of specimen that was 0.076 m in UPV machine, recoded the values by using the ultrasonic pulse velocity techniques, and after that tested for the same specimen by using a universal testing machine for determining the compressive strength for each specimen with respect to day wise as shown in Table 1. It can be also observed that various mixture proportions of cement mortar cubes were recorded that the ultrasonic pulse velocity values with different curing days for all values are presented in Table 2.

Table 1: Average compressive strength (MPa) of cement mortar (1 : 3) for different mix proportions.

Mix ID
Constituents
7th day
14th day
28th day

A1
0PC + 1% acl
21
24
27.62

A2
0PC + 2% acl
14.45
16
23.92

A3
0PC + 3% acl
13.2
19
22.43

B1
0PC + 20% fly ash + 1% acl
17.1
20
22.47

B2
0PC + 20% fly ash + 2% acl
15
21
24.72

B3
0PC + 20% fly ash + 3% acl
16
18
22.2

C1
0PC + 30% fly ash + 1% acl
16
21
22.59

C2
0PC + 30% fly ash + 2% acl
15
16.5
25.28

C3
0PC + 30% fly ash + 3% acl
10.8
14.1
17.39

D1
0PC + 40% fly ash + 1% acl
11.8
13.5
17.86

D2
0PC + 40% fly ash + 2% acl
12.35
13.98
16.75

D3
0PC + 40% fly ash + 3% acl
13
17.5
18.32

Table 2: Ultrasonic pulse velocity (m/sec) for different mix proportion of cement mortar specimens.

Mix ID
7th day
14th day
28th day

A1
4020
3750
3880

A2
3590
3440
3670

A3
3740
3480
3730

B1
3580
3550
3800

B2
3740
3660
4000

B3
3660
3910
3810

C1
3640
4200
3810

C2
3310
4135
3900

C3
3140
3485
3520

D1
3180
3300
3640

D2
3580
3330
3630

D3
3880
3700
3720

3.2. Fresh Cement Pastes Monitoring by UPV Test

The experimental results obtained from the fresh cement paste studies using ultrasonic pulse velocity are shown in Figure 1. To observe the stiffens of early age properties of different cementitious materials by using Plexiglass, the size of the Plexiglass mould was  mm. The fresh cement paste was gently poured into the glass mould with three layer, for each layer compacted gently after finishing the top surface and measured the Ultrasonic pulse velocity in terms of m/sec and for each different mixtures were carried out immediately after finishing the top surface of the cement past by attaching the transmitter and the reading was taken at every 5 minute intervals for all mixture proportion investigated. A different mixture proportion of fresh cement paste was monitored, and all the values are tabulated in Tables 3, 4, 5, 6, 7, and 8 and plotted graphically in Figures 2, 3, 4, 5, 6, 7, 8, and 9. In general the fly ash-based mortar mixtures with different percentage of fly ash contents showed a decrease in UPV corresponding to setting times. This indicates that the degree of hydration at the same duration is reduced in the case of fly ash-based mixtures due to the prolonged dormant period and delay during the acceleration period of hydration. Some of the mixes showed different behavior. The fly ash-based mixes also showed normal changes in the ultrasonic pulse velocity with decrease in water to binder ratio. The mixtures incorporating fly ash as a binder at 10%, 20%, 30%, 40%, and 50% with a suitable selection of the water to binder ratio showed better improvement in the rate of hardening with the addition of accelerator. Also the grade of cement used plays a major role in the early setting reaction and faster reactivity due to the fineness of cement particles. However, an optimal addition of fly ash in cement shows a gradual increase in the early reaction with the cement hydration products and helps in improved microstructural formation.

Table 3: Ultrasonic pulse velocity for different mix proportions of fresh cement paste.

Time (min)
Velocity (meter/second)

0PC
PPC

0
1480
950

5
1430
1110

10
1810
1320

15
1350
1260

20
1500
1260

25
1270
1400

30
1500
1040

35
1570
1320

40
1660
1270

45
1590
1290

50
1300
1430

55
1120
1280

60
1250
1170

65
1360
1220

70
1000
1190

75
1100
1260

80
14 60
1310

85
1410
1220

90
920
1360

95
1620
1300

100
1240
1210

105
1610
1220

110
1630
1090

115
2140
1300

120
1200
1200

125
1630
1450

130
1440
1590

135
1910
1290

140
1600
1210

145
1980
1280

150
2240
1320

155
1730
1380

160
2240
1380

165
2180
1410

170
2220
1420

Table 4: Ultrasonic pulse velocity for different mix proportions of fresh cement paste.

Time (min)
Ultrasonic pulse velocity (meter/second)

0PC
0PC + 20% FA
0PC + 20% FA + 1% acl
0PC + 20% FA + 2% acl
0PC + 20% FA + 3% acl

0
1480
1370
1040
490
730

5
1430
1830
1130
570
1210

10
1810
1770
1080
490
1360

15
1350
1420
810
610
1320

20
1500
1970
1160
470
1200

25
1270
1790
910
630
1120

30
1500
1790
1090
700
1370

35
1570
1710
1280
550
1320

40
1660
1740
970
550
1200

45
1590
1620
800
570
1170

50
1300
1620
710
630
1130

55
1120
1700
940
630
1240

60
1250
1440
900
680
1200

65
1360
1380
1000
750
1060

70
1000
1340
810
570
1110

75
1100
1340
740
540
1140

80
1460
1360
900
660
1160

85
1410
1650
810
690
1130

90
920
1720
1020
700
1100

95
1620
1600
920
710
1150

100
1240
1710
960
710
1130

105
1610
1700
910
705
1200

110
1630
1720
890
700
1130

115
2140
1740
900
710
1160

120
1200
1690
910
720
1100

125
1630
1720
900
730
1030

130
1440
1730
920
720
1180

135
1910
1710
940
740
1110

140
1600
1730
960
760
1180

145
1980
1690
960
720
1030

150
2240
1800
980
750
1180

155
1730
1790
960
760
1360

160
2240
1780
920
780
1150

165
2180
1810
980
790
1160

170
2220
1820
1000
800
1130

Table 5: Ultrasonic pulse velocity for different mix proportions of fresh cement paste.

Time (min)
Ultrasonic pulse velocity (meter/second)

0PC + 30% FA
0PC + 30% FA + 1% acl
0PC + 30% FA + 2% acl
0PC + 30% FA + 3% acl

0
1290
660
750
1150

5
1150
310
800
1240

10
1150
550
750
1080

15
1060
340
780
1110

20
1070
660
740
1120

25
1200
650
770
1080

30
1100
510
700
1170

35
1120
530
760
1140

40
1180
420
440
1250

45
1220
430
710
1090

50
1290
400
720
1090

55
1290
350
730
1090

60
1360
620
740
1090

65
1120
390
690
1150

70
1090
510
700
1080

75
1270
420
550
1070

80
1270
340
720
1180

85
1290
420
680
1070

90
1130
340
550
1140

95
1220
410
690
1050

100
1240
410
740
1110

105
1300
500
660
1100

110
1220
490
660
1060

115
1260
390
700
1090

120
1110
430
680
1250

125
1240
270
700
1160

130
1140
700
700
1110

135
1130
730
640
1110

140
1270
690
760
1170

145
1140
950
730
1140

150
1170
710
650
1070

155
1240
940
710
1130

160
1240
960
600
1180

165
1290
740
710
1050

170
1220
960
550
1080

Table 6: Ultrasonic pulse velocity for different mix proportions of fresh cement paste.

Time (min)
Ultrasonic pulse velocity (meter/second)

0PC + 40% FA
0PC + 40% FA + 1% acl
0PC + 40% FA + 2% acl
0PC + 40% FA + 3% acl

0
1140
870
970
1000

5
1110
900
910
980

10
1110
890
560
900

15
1130
730
710
940

20
1060
890
920
960

25
1060
860
700
940

30
1150
950
710
880

35
1270
980
800
860

40
1190
920
710
640

45
1090
790
710
840

50
1060
1010
670
620

55
1090
950
680
900

60
1030
870
680
910

65
1110
900
560
990

70
1250
890
550
800

75
990
890
560
1060

80
1150
880
660
1030

85
1100
870
670
730

90
1130
870
670
930

95
1130
890
680
690

100
1160
870
650
990

105
1000
860
620
1010

110
1000
880
680
960

115
720
900
670
650

120
1140
910
690
920

125
820
920
700
950

130
1040
940
710
1040

135
1210
900
710
890

140
1150
890
690
650

145
1210
890
720
860

150
1220
910
710
910

155
1160
920
720
920

160
1240
930
690
930

165
1390
910
710
940

170
1320
950
700
960

Table 7: Ultrasonic pulse velocity for different mix proportions of fresh cement paste.

Time (min)
Ultrasonic pulse velocity (meter/second)

0PC + 50% FA
0PC + 50% FA + 1% acl
0PC + 50% FA + 2% acl
0PC + 50% FA + 3% acl

0
1110
640
1100
1070

5
1100
690
1090
1080

10
1240
660
1010
1000

15
1130
690
1060
1050

20
1120
640
970
1100

25
1090
680
1010
1130

30
1120
630
950
1070

35
1110
520
1080
1080

40
1100
520
1090
1240

45
1020
650
1090
1180

50
1120
520
1110
1260

55
1080
540
1110
1210

60
1080
540
1090
1240

65
1030
620
1120
1260

70
950
530
1130
1290

75
1100
520
1110
1200

80
1130
620
1060
1240

85
1060
610
1070
1210

90
1030
540
1160
1240

95
1130
560
1120
1190

100
1270
600
1190
1010

105
1130
560
1030
1010

110
1130
570
1090
1130

115
1210
590
1080
1310

120
1190
600
1100
1150

125
1200
610
1090
1060

130
1130
620
1130
1170

135
1150
620
1160
1160

140
1220
630
1120
1000

145
1130
640
1060
1210

150
1150
650
1140
1030

155
1220
660
1170
1270

160
1380
680
1180
1290

165
1210
700
1080
1270

170
1240
710
1240
1280

Table 8: Ultrasonic pulse velocity for different mix proportions of cement paste.

Time (min)
0PC
0PC + 1% acl
0PC + 2% acl

0
950
800
480

5
1110
1090
380

10
1320
1050
860

15
1260
1070
870

20
1260
1100
860

25
1400
1210
510

30
1040
1050
860

35
1320
1100
880

40
1270
1130
490

45
1290
1070
550

50
1430
1240
910

55
1280
1450
1020

60
1170
1390
920

65
1220
1230
950

70
1190
1210
900

75
1260
1140
920

80
1310
1350
960

85
1220
1310
930

90
1360
1390
900

95
1300
1150
1030

100
1210
1180
890

105
1220
1040
920

110
1090
1040
960

115
1300
1060
870

120
1200
1080
970

125
1450
1080
860

130
1590
1210
1100

135
1290
1220
1020

140
1210
1210
1040

145
1280
1220
1030

150
1320
1230
1020

155
1380
1220
1060

160
1380
1240
1060

165
1410
1230
940

170
1420
1210
1020

Figure 1: Test setup for Plexiglass ultrasonic pulse velocity for monitoring the various fresh cement paste.

Figure 2: Cement mortar test results for different mix proportions.

Figure 3: Ultrasonic pulse velocity for various fresh cmentitous systems.

Figure 4: Ultrasonic pulse velocity of fresh 0PC and 0PC systems.

Figure 5: Ultrasonic pulse velocity for 20% fly ash replaced with cement with various percentages of the accelerator.

Figure 6: Ultrasonic pulse velocity for 30% fly ash replaced with cement with various percentages of the accelerator.

Figure 7: Ultrasonic pulse velocity for 40% fly ash replaced with cement with various percentages of the accelerator.

Figure 8: Ultrasonic pulse velocity for 50% fly ash replaced with cement with various percentages of the accelerator.

Figure 9: Ultrasonic pulse velocity for 0PC with various percentages of accelerator.

4. Summary

The important conclusions arrived based on these investigations are as follows.

The UPV values show a varied pattern, which is very much affected by setting time, which in turn is affected by water-binder ratio and chemical admixture dosage. There is a need for development of a technique based on more reliable methods for prediction of setting times. The ultrasonic pulse velocity techniques the test result values observed a different pattern, which is very much affected by setting time, which in turn is affected by water-binder ratio and chemical admixture dosage. The pulse velocity measurements showed an increased rate of hardening in cementitious systems and thereby proves to be a worthy method of assessment of cement hydration. It was observed from the test results of UPV that the influence of accelerator provided a constant increase in strength gain at the early ages. It may be observed from the graphs that the hydration process occurs in 3 stages. In the 1st stage, the hydration occurs very rapidly in the first few minutes. In the 2nd stage, the hydration process ceases or remains constant for another few minutes. This period is known as “dormant period.” After this stage, the rate of hydration starts to increase again. At the end of the dormant period, the C₂S and C₃S in the cement start to react, with the formation of calcium silicate hydrate (C–S–H) and calcium hydroxide Ca(OH)₂. It observed that the test result value for 0PC with 20 percentage of fly ash showed an increase in UPV values up to 60 minutes, after that 60 to 90 minutes had a dormant period; that is, the heat of hydration was decreased, after further increasing the setting time will develop the stiffness of the cement paste.

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