METHOD OF MAKING, PROTECTING, CURING

& TESTING CONCRETE CYLINDERS

 

SCOPE

This method covers procedures for making, protecting, and curing, according to AASHTO) T23. This method also covers testing concrete cylinder specimens for compressive strength. This test procedure is a supplement and not a replacement for the beam test to determine when a structure may be put in service.

 

I.       MAKING, PROTECTING & CURING SPECIMENS

 

A.     Apparatus for Making Specimens

 

1.     6 in. x 12 in. (152.4 mm x 304.8 mm) or 4 in. x 8 in. (101.6 mm x 203.2 mm) steel, brass, or single-use plastic vertical molds meeting the requirements of AASHTO M205.

 

2.     Molds shall be the vertical type.

 

3.     Tamping rods shall comply with AASHTO T23 and the following:

 

Mold Size

Tamping Rod Diameter

4 in. x 8 in

(101.6 mm x 203.2 mm)

3/8 in. (9.5mm)

6 in. x 12 in.

(152.4 mm x 304.8 mm)

5/8 in. (16mm)

 

4.     Internal or external vibrators may be used. They shall comply with AASHTO T23 with the exception that the diameter of the vibrating element of the internal vibrator shall vary for each specimen size, as stated below. External vibrators shall be either a table type or a plank type.

 

5.     Rubber hammer

 

6.     Wood float or equivalent

 

B.     Making Test Specimens

 

1.     The concrete shall be sampled in accordance with IM 327, Sampling Freshly Mixed Concrete.

 

2.     Before casting specimens, the inside surfaces of the steel or brass molds should be clean and treated with a thin coating of light grease or form oil.

 

3.     Consolidation may be rodding with a tamping rod, or by vibration, either internal or external. Concrete with slump greater than 3 inches (75 mm) shall be consolidated by rodding. Concrete with slump of 1 inch to 3 inches (25 mm to 75 mm) shall be consolidated by rodding or vibration. Concrete with slump of less than1 inch (25 mm) shall be consolidated by vibration.

 

a.     Rodding. Specimens shall receive the proper number of roddings evenly distributed per layer as indicated in the table. The bottom layer shall be rodded throughout its depth. For each upper layer, the rod shall penetrate 1 inch (25 mm) into the underlying layer. After rodding each layer, the sides and ends of the mold shall be tapped with a rubber hammer until the surface of the concrete is relatively smooth. Use an open hand to tap the single-use molds. After consolidation, strike off the horizontal surface and finish with a float or trowel.

 

Mold Size

No. of Equal Depth Layers

No. of Roddings per Layer

4 in. x 8 in

(101.6 mm x 203.2 mm)

2

25

6 in. x 12 in.

(152.4 mm x 304.8 mm)

3

25

 

b.     Internal Vibration. Specimens shall receive the required number of insertions of a vibrator layer as indicated in the table. If more than one insertion is required, distribute the insertion uniformly in each layer. Each layer shall be vibrated only long enough to make the surface relatively smooth. The time required will vary with the consistency of the concrete. Over vibration may cause segregation. In compacting the concrete, the vibrator shall not rest on or touch the sides of the mold. When vibrating the top layer, the element shall penetrate about 1/2 inch (13 mm) into the bottom layer. After vibrating, tap the sides of the mold with a rubber hammer to ensure removal of entrapped air bubbles at the surface of the mold. Use an open hand to tap the single-use molds. When consolidation is complete, strike off and finish with a wood float or trowel.

 

Mold Size

Vibrator Diameter

No. of Equal Depth Layers

No. of Insertions per Layer

4 in. x 8 in

(101.6 mm x 203.2 mm)

to I inch

19 to 25 mm

2

1

6 in. x 12 in.

(152.4 mm x 304.8 mm)

to I 1/2 inch

19 to 38 mm

2

2

 

c.      External Vibration. Each layer shall be vibrated only until the surface is relatively smooth. Take care to ensure that the mold is rigidly attached or securely held against the vibrating table or vibrating surface. After consolidation, strike off and finish with a trowel or float.

 

C.    Protecting & Curing

 

1.     Initial Curing. During the first 24 hours after molding, specimens shall be stored under conditions that maintain the temperature immediately adjacent to the specimens in the range of 50F to 80F (10C to 27C) and prevent loss of moisture from the specimens. This may be done by covering specimens with wet burlap and placing a plastic sheet over the burlap, or use other suitable methods to ensure that the foregoing requirements are met.

 

2.     Curing to Determine Form Removal Time or When a Structure May be Put in Service. Cure test specimens as nearly as practicable in the same manner as the concrete in the structure. After 48 4 hours, remove specimens from the molds. They shall be stored as near as possible to the point in the structure they represent and shall be afforded the same temperature protection and moisture environment as the structure until the time of testing. Specimens shall be tested while in the moisture condition resulting from the curing they receive.

 

3.     Curing To Check the Adequacy of Laboratory Mix Proportions for Strength or As a Basis For Acceptance or For Quality Control. For this purpose, specimens are to be removed from the molds at the end of 16 to 24 hours and stored in a moist condition at 68F to 81.5F (20C to 27.5C) until the time of test. This condition can be met by immersion in saturated limewater. NOTE: Lime-saturated water is prepared by mixing 1 teaspoon (12 g) of hydrated lime, with 1 gallon (3.8 liters) of water. Hydrated lime should be a minimum of 90 percent calcium hydroxide (CaOH).

 

4.     Steam Curing. When artificial heat is used to accelerate curing, concrete specimens shall be placed with the unit being cured and shall receive the same curing as the concrete they represent. Prior to testing the specimens, the temperature of the concrete shall be lowered to the temperature of the surrounding air at a rate not to exceed 40F (22C) per hour.

 

5.     Special care must be given to ensure that specimens are not damaged during handling. For 16 to 24 hours after molding, specimens shall not be moved.

 

II.     TESTING CONCRETE SPECIMENS FOR COMPRESSION

 

A.     Apparatus

 

1.     The testing machine shall conform to AASHTO T22. Manually operated testing machines will be accepted.

 

B.     Time of Testing

 

1.     Make compression tests of moist cured specimens as soon as practicable after removal from curing. Keep specimens moist by use of wet burlap or other suitable covering, which will ensure similar protection until actual time of testing.

 

2.     The time to test specimens otherwise cured will be as directed by the engineer.

 

C.    Test Specimens

 

1.     Neither end of compressive test specimens when tested shall depart from the perpendicularity to the axis by more than 0.5 degrees [approximately 1/8 in. in 12 in. (3 mm in 300 mm)]

 

2.     The ends of the specimens that are not plane within 0.002 in. (0.05 mm) shall be capped. The planeness of the ends of every tenth specimen should be checked by means of a straightedge and feeler gauge, making a minimum of three measurements on different diameters, to insure that the end surfaces do not depart from a plane by more than 0.002 in. (0.05 mm).

 

3.     The top surface of vertically cast specimens shall be capped.

 

D.    Capping

 

1.     Capping equipment and procedures shall comply with that described in AASHTO T231.

 

2.     Unbound caps and equipment shall comply with ASTM C1231.

 

E.     Test Procedure

 

1.     Placing Specimen

 

a.     Place the plain (lower) bearing block with its hardened face up, on the table or platen of the testing machine directly under the spherically seated (upper) bearing block.

 

b.     Wipe clean the bearing faces of the upper and lower bearing blocks and of the test specimen.

 

c.      Carefully align the axis of the specimen with the center thrust of the spherically seated block.

 

d.     As the spherically seated block is brought to bear on the specimen, rotate its moveable portion gently by hand so that uniform seating is obtained.

 

2.     Rate of Loading

 

a.     Apply the load continuously and without shock. Apply the load at a constant rate within the range of 20 to 50 psi (138 kPa to 345 kPa) per second. During the application of the first half of the estimated maximum load, a higher rate of loading may be permitted.

 

b.     Do not make any adjustment in the controls of the testing machine while the specimen is yielding, especially in the period just before failure.

c.      Increase the load until the specimen yields or fails, and record the maximum load carried by the specimen during test.

 

d.     Note the type of failure (Figure 1) and the appearance of the concrete if the break appears to be abnormal.

 

F.     Calculations

 

1. Calculate the compressive strength of the specimen by dividing the maximum load carried by the specimen during the test by the cross sectional area, and express the result to the nearest 10 psi (0.1 MPa). The attached tables may be used to facilitate these computations.

 

Figure 1. Compressive Fracture Types

 

Figure 2. Compression Testing Machine


 

Table for Computing MPa/1000 kPa on 6 in. x 12 in. (154.mm x 304.8 mm) Cylinders

Area = 0.01824m

Load (kN)

MPa

Load (kN)

MPa

Load (kN)

MPa

Load (kN)

MPa

Load (kN)

MPa

175

9.59

425

23.30

675

37.01

925

50.71

1175

64.42

180

9.87

430

23.57

680

37.28

930

50.99

1180

64.69

185

10.14

435

23.85

685

37.55

935

51.26

1185

64.97

190

10.42

440

24.12

690

37.83

940

51.54

1190

65.24

195

10.69

445

24.40

695

38.10

945

51.81

1195

65.52

200

10.96

450

24.67

700

38.38

950

52.08

1200

65.79

205

11.24

455

24.95

705

38.65

955

52.36

 

 

210

11.51

460

25.22

710

38.93

960

52.63

 

 

215

11.79

465

25.49

715

39.20

965

52.91

 

 

220

12.06

470

25.77

720

39.47

970

53.18

 

 

 

 

 

 

 

 

 

 

 

 

225

12.34

475

26.04

725

39.75

975

53.45

 

 

230

12.61

480

26.32

730

40.02

980

53.73

 

 

235

12.88

485

26.59

735

40.30

985

54.00

 

 

240

13.16

490

26.86

740

40.57

990

54.28

 

 

245

13.43

495

27.14

745

40.84

995

54.55

 

 

250

13.71

500

27.41

750

41.12

1000

54.82

 

 

255

13.98

505

27.69

755

41.39

1005

55.10

 

 

260

14.25

510

27.96

760

41.67

1010

55.37

 

 

265

14.53

515

28.23

765

41.94

1015

55.65

 

 

270

14.80

520

28.51

770

42.21

1020

55.92

 

 

 

 

 

 

 

 

 

 

 

 

275

15.06

525

28.78

775

42.49

1025

56.20

 

 

280

15.35

530

29.06

780

42.76

1030

56.47

 

 

285

15.63

535

29.33

785

43.04

1035

56.74

 

 

290

15.90

540

29.61

790

43.31

1040

57.02

 

 

295

16.17

545

29.88

795

43.59

1045

57.29

 

 

300

16.45

550

30.15

800

43.86

1050

57.57

 

 

305

16.72

555

30.43

805

44.13

1055

57.84

 

 

310

17.00

560

30.70

810

44.41

1060

58.11

 

 

315

17.27

565

30.98

815

44.68

1065

58.39

 

 

320

17.54

570

31.25

820

44.96

1070

58.66

 

 

 

 

 

 

 

 

 

 

 

 

325

17.82

575

31.52

825

45.23

1075

58.94

 

 

330

18.09

580

31.80

830

45.50

1080

59.21

 

 

335

18.37

585

32.07

835

45.78

1085

59.48

 

 

340

18.64

590

32.35

840

46.05

1090

59.76

 

 

345

18.91

595

32.62

845

46.33

1095

60.03

 

 

350

19.19

600

32.89

850

46.60

1100

60.31

 

 

355

19.46

605

33.17

855

46.88

1105

60.58

 

 

360

19.74

610

33.44

860

47.15

1110

60.86

 

 

365

20.01

615

33.72

865

47.42

1115

61.13

 

 

370

20.29

620

33.99

870

47.70

1120

61.40

 

 

 

 

 

 

 

 

 

 

 

 

375

20.56

625

34.27

875

47.97

1125

61.68

 

 

380

20.83

630

34.54

880

48.25

1130

61.95

 

 

385

21.11

635

34.81

885

48.52

1135

62.23

 

 

390

21.38

640

35.09

890

48.79

1140

62.50

 

 

395

21.66

645

35.36

895

49.07

1145

62.77

 

 

400

21.93

650

35.64

900

49.34

1150

63.05

 

 

405

22.20

655

35.91

905

49.62

1155

63.32

 

 

410

22.48

660

36.18

910

49.89

1160

63.60

 

 

415

22.75

665

36.46

915

50.16

1165

63.87

 

 

420

23.03

670

36.73

920

50.44

1170

64.14

 

 

 


 

(Load in Thousands) Table for Computing lb./in. on 6 in. x 12 in. Cylinders

Area = 28.2744 in.

Load

Psi

Load

Psi

Load

Psi

Load

Psi

Load

Psi

40

1410

90

3180

140

4950

190

6720

240

8490

41

1450

91

3220

141

4990

191

6760

241

8520

42

1490

92

3250

142

5020

192

6790

242

8560

43

1520

93

3290

143

5060

193

6830

243

8590

44

1560

94

3320

144

5090

194

6860

244

8630

45

1590

95

3360

145

5130

195

6900

245

8670

46

1630

96

3400

146

5160

196

6930

246

8700

47

1660

97

3430

147

5200

197

6970

247

8740

48

1700

98

3470

148

5230

198

7000

248

8770

49

1730

99

3500

149

5270

199

7040

249

8810

 

 

 

 

 

 

 

 

 

 

50

1770

100

3540

150

5310

200

7070

250

8840

51

1800

101

3570

151

5340

201

7110

251

8880

52

1840

102

3610

152

5380

202

7140

252

8910

53

1870

103

3640

153

5410

203

7180

253

8950

54

1910

104

3680

154

5450

204

7220

254

8980

55

1950

105

3710

155

5480

205

7250

255

9020

56

1980

106

3750

156

5520

206

7290

256

9050

57

2020

107

3780

157

5550

207

7320

257

9090

58

2050

108

3820

158

5590

208

7360

258

9120

59

2090

109

3860

159

5620

209

7390

259

9160

 

 

 

 

 

 

 

 

 

 

60

2120

110

3890

160

5660

210

7430

260

9200

61

2160

111

3930

161

5690

211

7460

261

9230

62

2190

112

3960

162

5730

212

7500

262

9270

63

2230

113

4000

163

5760

213

7530

263

9300

64

2260

114

4030

164

5800

214

7570

264

9340

65

2300

115

4070

165

5840

215

7600

265

9370

66

2330

116

4100

166

5870

216

7640

266

9410

67

2370

117

4140

167

5910

217

7670

267

9440

68

2410

118

4170

168

5940

218

7710

268

9480

69

2440

119

4210

169

5980

219

7750

269

9510

 

 

 

 

 

 

 

 

 

 

70

2480

120

4240

170

6010

220

7780

 

 

71

2510

121

4280

171

6050

221

7820

 

 

72

2550

122

4310

172

6080

222

7850

 

 

73

2580

123

4350

173

6120

223

7890

 

 

74

2620

124

4390

174

6150

224

7920

 

 

75

2650

125

4420

175

6190

225

7960

 

 

76

2690

126

4460

176

6220

226

7990

 

 

77

2720

127

4490

177

6260

227

8030

 

 

78

2760

128

4530

178

6300

228

8060

 

 

79

2790

129

4560

179

6330

229

8100

 

 

 

 

 

 

 

 

 

 

 

 

80

2830

130

4600

180

6370

230

8130

 

 

81

2860

131

4630

181

6400

231

8170

 

 

82

2900

132

4670

182

6440

232

8210

 

 

83

2940

133

4700

183

6470

233

8240

 

 

84

2970

134

4740

184

6510

234

8280

 

 

85

3010

135

4770

185

6540

235

8310

 

 

86

3040

136

4810

186

6580

236

8350

 

 

87

3080

137

4850

187

6610

237

8380

 

 

88

3110

138

4880

188

6650

238

8420

 

 

89

3150

139

4920

189

6680

239

8450

 

 

 


 


(Load in Thousands) Table for Computing lb./in. on 4 in. x 8 in. Cylinders

Area = 12.5666 in.

Load

Psi

Load

Psi

Load

Psi

Load

Psi

10

800

50

3980

90

7160

130

10350

11

880

51

4060

91

7240

131

10420

12

950

52

4140

92

7320

132

10500

13

1030

53

4220

93

7400

133

10580

14

1110

54

4300

94

7480

134

10660

15

1190

55

4380

95

7560

135

10740

16

1270

56

4460

96

7640

136

10820

17

1350

57

4540

97

7720

137

10900

18

1430

58

4620

98

7800

138

10980

19

1510

59

4700

99

7880

139

11060

 

 

 

 

 

 

 

 

20

1590

60

4770

100

7960

140

11140

21

1670

61

4850

101

8040

141

11220

22

1750

62

4930

102

8120

142

11300

23

1830

63

5010

103

8200

143

11380

24

1910

64

5090

104

8280

144

11460

25

1990

65

5170

105

8360

145

11540

26

2070

66

5250

106

8440

146

11620

27

2150

67

5330

107

8520

147

11700

28

2230

68

5410

108

8590

148

11780

29

2310

69

5490

109

8670

149

11860

 

 

 

 

 

 

 

 

30

2390

70

5570

110

8750

150

11940

31

2470

71

5650

111

8830

151

12020

32

2550

72

5730

112

8910

152

12100

33

2630

73

5810

113

8990

153

12180

34

2710

74

5890

114

9070

154

12260

35

2790

75

5970

115

9150

155

12330

36

2860

76

6050

116

9230

156

12410

37

2940

77

6130

117

9310

157

12490

38

3020

78

6210

118

9390

158

12570

39

3100

79

6290

119

9470

159

12650

 

 

 

 

 

 

 

 

40

3180

80

6370

120

9550

160

12730

41

3260

81

6450

121

9630

161

12810

42

3340

82

6530

122

9710

162

12890

43

3420

83

6610

123

9790

163

12970

44

3500

84

6680

124

9870

164

13050

45

3580

85

6760

125

9950

165

13130

46

3660

86

6840

126

10030

166

13210

47

3740

87

6920

127

10110

167

13290

48

3820

88

7000

128

10190

168

13370

49

3900

89

7080

129

10270

169

13450

 


 


Table for Computing MPa on 4 in. x 8 in. (101.6 mm x 203.3 mm) Cylinders

Area = 0.008107 m

Load (kN)

MPa

Load (kN)

MPa

Load (kN)

MPa

Load (kN)

MPa

45

5.55

245

30.22

445

54.89

645

79.56

50

6.17

250

30.84

450

55.51

650

80.18

55

6.78

255

31.45

455

56.12

655

80.79

60

7.40

260

32.07

460

56.74

660

81.41

65

8.02

265

32.69

465

57.36

665

82.03

70

8.63

270

33.30

470

57.97

670

82.64

75

9.25

275

33.92

475

58.59

675

83.26

80

9.87

280

34.54

480

59.21

680

83.88

85

10.48

285

35.15

485

59.82

685

84.49

90

11.10

290

35.77

490

60.44

690

85.11

 

 

 

 

 

 

 

 

95

11.72

295

36.39

495

61.06

695

85.73

100

12.34

300

37.01

500

61.68

700

86.35

105

12.95

305

37.62

505

62.29

705

86.96

110

13.57

310

38.24

510

62.91

710

87.58

115

14.19

315

38.86

515

63.53

715

88.20

120

14.80

320

39.47

520

64.14

720

88.81

125

15.42

325

40.09

525

64.76

725

89.43

130

16.04

330

40.71

530

65.38

730

90.05

135

16.65

335

41.32

535

65.99

735

90.66

140

17.27

340

41.94

540

66.61

740

91.28

 

 

 

 

 

 

 

 

145

17.89

345

42.56

545

67.23

745

91.90

150

18.50

350

43.17

550

67.84

750

92.51

155

19.12

355

43.79

555

68.46

755

93.13

160

19.74

360

44.41

560

69.08

760

93.75

165

20.35

365

45.02

565

69.69

 

 

170

20.97

370

45.64

570

70.31

 

 

175

21.59

375

46.26

575

70.93

 

 

180

22.20

380

46.87

580

71.54

 

 

185

22.82

385

47.49

585

72.16

 

 

190

23.44

390

48.11

590

72.78

 

 

 

 

 

 

 

 

 

 

195

24.05

395

48.72

595

73.39

 

 

200

24.67

400

49.34

600

74.01

 

 

205

25.29

405

49.96

605

74.63

 

 

210

25.90

410

50.57

610

75.24

 

 

215

26.52

415

51.19

615

75.86

 

 

220

27.14

420

51.81

620

76.48

 

 

225

27.75

425

52.42

625

77.09

 

 

230

28.37

430

53.04

630

77.71

 

 

235

28.99

435

53.66

635

78.33

 

 

240

29.60

440

54.27

640

78.94