Control Tests for Concrete

ByProf. Adel El Kordi

&Dr. Meheddene Machaka

Structural EngineeringDepartment

Faculty of EngineeringBeirut Arab University

CVLE 321

Laboratory and Field Tests forFreshly Mixed Concrete

Sampling Consistency Temperature Air content Density Preparation of strength specimen Setting Time

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Sampling

ASTM C 172 (AASHTO T 141)Sampling Freshly MixedConcrete

Requirements: Sample size 28 L (1 ft3) Less than 15 min between first

and last portion of sample Sample should not be taken

from first or last portion of batchdischarge

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Tests Used to Measure Consistency Slump test

ASTM C 143 (AASHTO T 119)

K-Slump TesterASTM C 1362

Compacting factor Vebe Consist meter

ASTM C 1170

Thaulow test Kelly ball penetration test

ASTM C 360-92—now discontinued

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Slump Test

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Frequency of Testing — Slump First batch of concrete each day

Whenever the consistency ofconcrete appears to vary

Whenever strength-test cylindersare made at jobsite

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Temperature Measurement

ASTM C 1064(AASHTO T 309)

Temperature ofFreshly MixedPortland CementConcrete

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Density (Unit Weight) and YieldASTM C 138(AASHTO T 121)

Density (Unit Weight), Yield,and Air Content(Gravimetric) of Concrete

ASTM C 1040(AASHTO T 271)

Density of Unhardened andHardened Concrete inPlace By Nuclear Methods

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Air Content Pressure method

ASTM C 231(AASHTO T 152)

Volumetric methodASTM C 173(AASHTO T 196)

Gravimetric methodASTM C 138(AASHTO T 121)

Air indicator methodAASHTO T 199

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Frequency of Testing — Air Content

Made often enough at point ofdelivery to ensure proper aircontent.

Whenever strength-testcylinders are made at jobsite

Record of concretetemperature should be kept

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Molding of Strength Specimen

Field-molded specimenASTM C 31

Laboratory molded specimenASTM C 192

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Time Limit:Start molding 15 min aftersampling

Strength Specimen SizesCylinders : Max. aggregate size of 50 mm (2 in.):

150 × 300 mm (6 x 12 in.)—Stand. Cyl. Max. Aggregate size > 50 mm (2 in.):

Diameter = 3 x max. aggr. / Height = 2 xdiameter

High-Strength Concrete: 100 x 200 mm (4 x 8 in.)

Flexural Beams Max. aggregate size of 50 mm (2 in.):

150 × 150 mm (6 x 6 in.)—Stand. Beam Length: 500 mm (20 in.)

Max. Aggregate size > 50 mm (2 in.): Cross sect. = 3 x max. aggr. / Length = 3 x

depth + 50 mm (20 in.) 12

Frequency of Testing - Strength ACI 318 and ASTM C 94 require that

strength tests be taken — of each class of concrete placed

each day not less than once a day nor less than once for each 115 m3

Average strength of two 28-day testcylinders is required

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Cylinder Strengths 150 x 300 mm (6 x 12 in.) vs. 100 x 200 mm (4 x 8 in.)

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The difference between the two cylinder sizes is insignificant.

Curing Test Specimen

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Curing test specimens

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Standard testing procedures require that specimensbe cured under controlled conditions, either in thelaboratory or in the field. Controlled laboratory curing:1- In a moist room2- In a limewater storage tank. Limewater must besaturated with hydrated lime

Time of Setting

ASTM C 403 (AASHTO T 197)17

The initial and final time of setting is determined as the time when the penetrationresistance equals 3.4 Mpa and 27.6 MPa , respectively. Typically, initial set occurs between 2and 6 hours after batching and final set occurs between 4 and 12 hours.

Additional Tests for FreshlyMixed Concrete

1. Accelerated compression tests ASTM C 6842. Chloride content NRMCA method3. Cement content ASTM C 10784. Water content ASTM C 1079 (discontinued 1998)5. Bleeding of concrete ASTM C 232 (AASTO T 158)

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Bleeding of concrete

ASTM C 232 or (AASHTO T 158)

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Testing Hardened Concrete

1. Compressive strength ASTM C 39 (AASHTO T 22)2. Flexural strength ASTM C 78 and C 2933. Tensile strength ASTM C 4964. Air content ASTM C 4575. Density, absorption and voids ASTM C 6426. Portland cement content ASTM C 1084

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Testing Hardened Concrete (cont.)

7. SCM and organic admixture content8. Chloride content9. Petrographic analysis ASTM C 85610.Length Change—drying shrinkage ASTM C 15711.Modulus of Elasticity and Poisson’s Ratio ASTM C 46912.PH testing methods13.Permeability14.Moisture content

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Strength Test of Hardened ConcreteCan be performed on: Cured specimen molded

from samples of freshconcrete

Cored or sawed in-situspecimen

Cast-in-place cylinders

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Core Test

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Precautions that should be on cylinder concretecompression strength test ASTM 617

1- Capping Cylindrical Concrete Specimens2- L/D = 23- Cured under control conditions

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Unbonded Caps

ASTM C 1231Use of Unbonded Caps inDetermination ofCompressive Strength ofHardened ConcreteCylinders

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Testing Compressive Strength

Sulfur mortar capASTM C 617

Unbonded capsASTM C 1231

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Testing Compressive Strength

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Tensile Strength

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Tensile strength of concrete should be highenough to resist cracking from shrinkage andtemperature changes.

It can be measured using the following testa) From Compression Testb) Splitting tensile Testc) Flexural Test

Normally tensile strength is assessed usingflexural or split-cylinder test.

Splitting tensile Test test (ASTM 496)1. A cylinder specimen with dimension of 10x20

cm or 15x30 cm, placed with it’s axis in ahorizontal plane.

2.Then it is subjected to a uniform load alongthe length of the specimen.

LOADSide Elevation Of The CylinderFront Elevation

The load will split to 2 parts (P), so the splittingtensile strength can be calculated as

ft = 2P / ΠLdL = length of the cylinder

d = diameter of the cylinder

4. The type and shape of coarse aggregateparticles also affect the tensile strength.

5. Split Cylinder Test to determine the tensilestrength of concrete by splitting cylinders of theconcrete in a compression testing machine.

Flexural test1. Most common method for measuring the

tensile strength of concrete2. A concrete beam with span length equal to 3

times the beam depth ( the length of the beamshould be at least 2 in. (50mm) larger than thespan) is subjected to 3rd point loading (ASTMC78).

3. This produces tensile stresses at the bottom ofthe beam and compressive stresses at the top.

Since concrete is weaker in tension thancompression, the specimen fails where itbreaks into 2 following the formation of anearly vertical crack called a flexural crack,near the section of maximum moment.

From the failure load, the tensile strengthcalled the modulus of rupture (MOR) is thencalculated as followsbending stress = MY = strength in tension

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Testing Flexural Strength

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Compressive Vs. Flexural Strength

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Effect of Core Conditioning on Strength of drilled cores

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Evaluation of Compression Test ResultsFrom Cylinders ACI 318

Compress. strength satisfactory if —1. The average of all sets of three

consecutive strength tests equal to orexceed ƒc′ (Specified 28-daycompressive strength)

2. No individual strength test (average of 2-cylinders) is more than 3.5 Mpa belowthe specified strength.

If results do not meet criteria Strength evaluation by drilled cores

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Evaluation of Compressive Strength of Cores

1. Ave. strength of 3-cores is at least 85% ofƒc′ (Specified 28-day compressivestrength)

2. No single core less than 75% of ƒc′

Concrete represented by the cores areconsidered structurally adequate if —

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Air ContentASTM C 457

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Saturated Surface-Dry Density (SSD-Density)

whereDSSD is density in the SSD conditionM1 is the SSD mass in air, kgM2 is the apparent mass immersed in

water, kg is the density of water, 1000 kg/m3

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1

MMMDSSD

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Void Content and Absorption

Cement,kg/m3 w/cm

Compressivestrength at 90

days, MPa

Vol. ofperm.

voids, %

Absorptionafter im-

mersion, %

Absorptionafter im-

mersion andboiling, %

445 0.29 76.7 8.0 3.13 3.27327 0.50 38.2 12.7 5.45 5.56245 0.75 28.4 13.3 5.81 5.90

ASTM C 642

Concretes moist cured for 7 days

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Permeability

Cement,kg/m3 w/cm

Compressivestrength at

90 days, MPa

Permeability

RCPT,coulombs

90 daysponding,

% ClWater,

m/sAir,

m/sASTM C 39

AASHTO T 22ASTM C 1202AASHTO T 277

AASHTOT 259

API RP27

API RP27

445 0.29 76.7 852 0.022 — 3.19 x10-10

327 0.50 38.2 4315 0.076 1.94 x10-12

1.65 x10-9

245 0.75 28.4 5915 0.085 8.32 x10-12

1.45 x10-9

Concretes moist cured for 7 days41

Durability Tests Frost resistance

ASTM C 666, C 671, C 682 Sulfate resistance Alkali-aggregate Reactivity

ASTM C 227, C 289, C 295, C 441, C 586,C 1260, C 1293

Corrosion Resistance Abrasion Resistance

ASTM C 418, C 779, C 944, C 1138

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Carbonation ASTM C 856

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The depth of carbonation is determined by spraying phenolphthaleinsolution on a freshly broken concrete surface. Noncarbonated areas turn redor purple, carbonated areas stay colorless.

Nondestructive Test Methods (NDT) Rebound Hammer Penetration Maturity Pullout Break-Off Dynamic or Vibration Other

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Schmidt Rebound HammerASTM C 805

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Schmidt Rebound Hammer

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The results of a Schmidt rebound hammer test(ASTM C 805) are affected by:1- Surface smoothness2- size, shape, and rigidity of the specimen3- Age and moisture condition of the concrete 4-Type of coarse aggregate5- Degree of carbonation of the concrete surface.

Cold Bend Testing for Steel Reinforcement BarASTM A615

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Windsor ProbeASTM C 803

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Pullout TestASTM C 900

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Nondestructive Tests for ConcreteConcreteproperties

Recommended NDTmethods

Possible NDTmethods

Strength

Penetration probeRebound hammerPullout methodsBreak off

Generalquality anduniformity

Penetration probeRebound hammerUltrasonic pulse velocityGamma radiography

Ultrasonic pulse echoVisual examination

ThicknessRadarGamma radiographyUltrasonic pulse echo

Stiffness Ultrasonic pulse velocity Proof loading

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Concreteproperties

Recommended NDTmethods

Possible NDTmethods

Density Gamma radiographyUltrasonic pulse velocity Neutron density gage

Rebar sizeand location

CovermeterGamma radiography

X-ray radiographyUltrasonic pulse echo

Corrosionstate of rebar

Electrical potentialmeasurement

Presence ofsubsurfacevoids

Acoustic impactGamma radiographyUltrasonic pulse velocity

Infrared, X-ray,Ultrasound, Radar,Resonant frequency

Struct. integr.of con. struct.

Proof loading (load-deflection)

Proof testing usingacoustic emission

Density Gamma radiography Neutron density gage

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