concrete strength testing technician - cttp.uark.edu · 2019 2 course topics •astm c 617 (t 231)...

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Concrete Strength Testing Technician

developed by:The University of Arkansas, Dept. of Civil

Engineeringin conjunction with

The Arkansas Department of Transportation

Course Topics

• ASTM C 617 (T 231)o Capping Cylindrical Concrete Specimens

• ASTM C 1231o Use of Unbonded Caps in Determination of

Compressive Strength of Hardened Concrete Cylinders

• ASTM C 39 (T 22)o Compressive Strength of Cylindrical Concrete

Specimens• ASTM C 78 (T 97)

o Flexural Strength of Concrete

5Introduction

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Concrete Strength Testing Certification Program

• 5 Year Certificationo Written Examo Performance Exam

• Failure of Either Examo Requires retake of failed exam within 1 year• Entire written exam• Entire performance exam• If date is missed, student must retake both

examso Student is responsible for rescheduling of retake

6Introduction

Written Exam

• Questionso Standardso Special Applications

• ~ 40 Questionso Multiple Choiceo True / Falseo At least 8 questions

on each of the test methods

• Limitationso 1 Hour Examo Closed Book

• Passing Requirementso 60 % Each Standardo 70 % Overall

7Introduction

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Performance Exam

• Passing Requirementso Successfully perform all standards in the

laboratory• Two trials are allowed per standard• One additional retrial allowed per standard

o Student must request retrialo Proctor may not stop youo Student retrial starts over at beginning of test

o Failure to pass any standard within the allowable trials requires retaking of the entire performance exam

8Introduction

ARDOT Standard Specifications

9ARDOT Standard Specifications

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• 501.03 (Mix Design)o Minimum 28 day compressive strength: 4000 psio Test according to AASHTO T22 Compressive

Strength

Pavements


• 501.04 (a) (Quality Control)o Performed by Contractor in qualified laboratory

by a certified techniciano Contractor shall determine the specific locations

for samples and frequency of sampling for quality control

o AASHTO T 22 Compressive Strength• AASHTO T 24 Cores and T 23 Cylinders

o Compression Machine• Verify and Document

Pavements


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• 501.04 (b) (Acceptance Testing)o Acceptance by lot (4000 yd3)

• Each lot divided into four sublots (1000 yd3)• Engineer may establish a partial lot at anytime

o Thickness determination (AASHTO T148)• Shall be made from cores sampled for compressive

strength testso Compressive strength

• Determined by testing pavement cores 28 days and no more than 90 days after concrete placement

• Remove base course adhering to core

Pavements


• 501.04 (b) (Acceptance Testing)o Sampling

• Contractoro 1 sample taken at random from each subloto ARDOT will determine the location for each sample

using ARDOT Test Method 465• ARDOT

o A minimum of one sample taken at random from each lot, including partial lots

o ARDOT will determine the location for each sample using ARDOT Test Method 465

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Pavements

ARDOT Standard Specifications

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• 802.04 o Bridges, culverts, miscellaneous structures

Structures


• 802.06 (a) (Quality Control) o Contractor responsible for testingo Compressive strength• AASHTO T22• Minimum of two cylinders cast and tested

o Compression Machine• Verify and Document

Structures


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• 802.06 (b) (Acceptance Testing)o Acceptance by lot (400 yd3)

• Each lot divided into four sublots (100 yd3)• Engineer may establish a partial lot at anytime

o For Class S(AE) concrete the maximum sublot size will be 100 cubic yards or one deck pour, whichever is less

o A minimum of one set of tests per bridge structure is required

Structures


AASHTO T 24

OBTAINING AND TESTING DRILLED CORES AND SAWED

BEAMS OF CONCRETE

17Obtaining and Testing Drilled Cores and Sawed Beams of Concrete

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• Minimum diameter of 3.70”o Nominal diameter shall be at least 3.70 or at least

2x the NMAS, whichever is largero Less than 3.70 is permitted to obtain L/D greater

than 1, if justified

• Length – 1.9 to 2.1 times diameter• Less than 1.75 requires

correction

• Thickness determination – T148

Cores for Compressive Strength


• End preparationo No projections greater than 0.2” above endo End surface shall not depart from perpendicularity

by a slope of more than 1:8d (d is average core diameter)

o Diameter of ends shall not depart from mean diameter by more than 0.1”



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• Moisture conditioningo Wipe off surface moisture after drillingo When surfaces appear dry, but within one hour

store in plastic bagso Maintain at ambient temperatureo At least 5 days after last being wetted before

testing• To reduce moisture gradients



• Measure length for L/D ratio• Measure two diameters

o Do not test if largest and smallest diameter exceed 5 percent of average

• Test within 7 days, unless specified otherwise• Test according to T 22• Report



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MEASURING LENGTH OF DRILLED CONCRETE CORES

AASHTO T 148

22Measuring Length of Drilled Concrete Cores

• 3-point calipering device (Core length measuring device)

Apparatus


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• Measuring Rodo Shall be rounded to a radius of 0.125”o The spacing of the graduations shall be

0.10” or a decimal part thereof

• Each increment is 0.10”


Apparatus

Measuring Length of Drilled Concrete Cores

• Establish Calibrated lengtho Verification Gauges• Right circular cylinders with

flat ends• Diameter approximately

equal to diameter of cores to be measured

Apparatus


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• Load core in measuring deviceo Place smooth end of core down

(the end that represents the upper surface of the pavement slab)

o Center core in measuring device

Procedure


• Make 9 measurementso One at the center and one

each at 8 additional positions spaced at equal intervals along the circumference of the circle of measurement

o Read each of these 9 measurements to the nearest 0.05”

Procedure


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• What are these measurements?Procedure


• Report the length of the coreo Subtract the

measurement from the Calibrated Length for all 9 measurements (this gives you the core length of each measurement)

o Average each of these 9 measurements and report to the nearest 0.1”

Report

Subtract difference

Calibrated Length


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Example

Report


CONCRETE STRENGTH TESTING TECHNICIAN

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CAPPING CYLINDRICAL CONCRETE SPECIMENS

ASTM C 617AASHTO T 231

33Capping

Scope• Covers apparatus, materials, and

procedures for capping o Freshly molded concrete cylinders with neat

cement o Hardened cylinders and drilled concrete cores

with high-strength gypsum plaster or sulfur mortar

• SI units and inch-pound units are includedo May not be exact equivalents so not

interchangeable

34Capping

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• Capping Plateso Neat Cement Caps and

High Strength Gypsum-Paste• Glass Plate at least ¼” thick• Machined Metal Plate at least 0.45”

thick• Polished Plate of Granite or Diabase at

least 3” thicko Sulfur Mortar Caps

• Similar to above – recessed area for molten sulfur shall not be deeper than ½”

Capping Equipment

35Capping

• Capping Plateso Plates shall be at least 1” greater in diameter

than specimen

Capping Equipment

36Capping

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• Capping Plateso Working surface shall not depart from plane by

more than 0.002” in 6”

Capping Equipment

37Capping

• Capping Plateso Surface shall be free from gouges, grooves,

and indentations• Greater than 0.010” deep, or greater than 0.05 in.2

in surface area

Capping Equipment

38Capping

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• Alignment Deviceso Axis of the alignment device

and the surface of a capping plate• Perpendicular to 0.5°

oNote 2: 1 mm in 100 mm [1/8” in 12”]• Located so that no cap off-centered by

more than 1/16”

Capping Equipment

39Capping

• Melting Pots for Sulfur Mortaro Equipped with automatic

temperature controlso Metal or lined with material that

is not reactive with molten sulfuro Use in a hood to exhaust fumeso Open flame dangerous: flash

point of sulfur is 405°F

Capping Equipment

40Capping

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• WARNING:o Melting pot must be located

under a hood with an exhaust fan

o Well ventilatedo High concentrations are lethalo Lesser dosages may cause illness

Capping Equipment

41Capping

• Strength and Thickness shall conform to Table 1

Capping Materials

42Capping

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• Any materials, except neat cement paste, used to test concretes with strengths greater than 7000 psi, that has a strength less than the cylinder strength, shall provide the following documentationo Average strength of 15 cylinders capped with material not

less than 98% of companion cylinders capped with neat cement or ground plane to within 0.002”

o Standard deviation of strength should not be greater than 1.57 times standard deviation of reference cylinders

o Cap thicknesses were meto Hardening timeo Compressive strength of 2” cubes

Capping Materials

43Capping

• Compressive strength of capping materials shall be determined using 2” cubes (ASTM C109/AASHTO T106)o Cure same as material capping

cylinders

• Strength determined on receipt of new lot and at intervals not to exceed three months

Capping Materials

44Capping

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• Neat Hydraulic Cement Pasteo Make qualification tests on 2” cubes

• To determine effect of w/c ratio and ageo Mix to desired consistency generally 2 to 4 hours

before paste is to be used

Capping Materials

45Capping

• High-Strength Gypsum Cement Pasteo Make qualification tests on 2” cubes

• To determine effect of w/c ratio and ageo Mix to desired consistency and use promptly

Capping Materials

46Capping

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• Sulfur Mortaro Harden 2 hours – strengths less than 5000 psio Harden 16 hours – strengths 5000 psi or greater

Capping Materials

47Capping

• Sulfur Mortar o Qualification test

• Bring apparatus to temperature of 68 to 86°F• Lightly coat surfaces with mineral oil

Capping Materials

48Capping

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• Sulfur Mortaro Qualification test

• Bring mortar temperature to 265 to 290°F

Capping Materials

49Capping

• Sulfur Mortaro Stir sulfur

Capping Materials

50Capping

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• Sulfur Mortaro Fill to topo Allow for shrinkage• Approx. 15 minutes

o Refill with sulfur

Capping Materials

51Capping

• Sulfur Mortaro Allow to solidifyo Remove from molds without breaking knob

Capping Materials

52Capping

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• Sulfur Mortaro Remove oil, sharp edges, and finso Check planenesso Test cubes in compression – (ASTM C109)o Calculate compressive strength

Capping Materials

53Capping

• Freshly Molded Cylinderso Use only neat portland

cement pasteso Mix the material as

describedo Do not exceed the

water-cement ratio determined in qualification testing

Capping Procedures

54Capping

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• Freshly Molded Cylinderso Place conical mound of paste on specimen 2-4

hours after molding cylinder

Capping Procedures

55Capping

• Freshly Molded Cylinderso Press freshly oiled capping plate until plate

contacts rim of moldo Make as thin as possibleo Covero Remove after hardening

(after 12 hours)

Capping Procedures

56Capping

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• Hardened Concrete Specimenso General• Remove any coatings or deposits from

cylinder end

Capping Procedures

57Capping

• Hardened Concrete Specimenso General

• No point on the end of the cylinder shall exceed 1/8” from plane that is perpendicular to axis

• Cut/grind to correct

Capping Procedures

58Capping

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• Capping with High-Strength Gypsum Pasteo Mix the material as describedo Do not exceed the water-cement ratio

determined in qualification tests

Capping Procedures

59Capping

• Capping with High-Strength Gypsum Pasteo Form the caps

Capping Procedures

60Capping

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• Capping with High-Strength Gypsum Pasteo Generally, capping plates may be removed

within 45 minutes

Capping Procedures

61Capping

• Capping with Sulfur Mortaro Heat sulfur between 265

to 290°Fo Check temperature

hourlyo Five use limito No reuse for concrete

compressive strength greater than 5000 psi

Capping Procedures

62Capping

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• Capping with Sulfur Mortaro Warm capping device to slow rate of hardening

and permit production of thin caps

Capping Procedures

63Capping

• Capping with Sulfur Mortaro Oil capping plate lightlyo Stir sulfur before each use

Capping Procedures

64Capping

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• Capping with Sulfur Mortaro Ends of specimen must be dry so that steam

pockets or voids greater than ¼” do not form

Capping Procedures

65Capping

• Capping with Sulfur Mortaro Pour mortar onto surface of capping plate

Capping Procedures

66Capping

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• Capping with Sulfur Mortaro Lift cylinder and use guides to slide the cylinder

onto the capping plate

Capping Procedures

67Capping

• Capping with Sulfur Mortaro Cylinder end should rest on capping plate in

positive contact with alignment guideso Make contact until sulfur hardens

Capping Procedures

68Capping

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• Daily Check during cappingo Check planeness of caps before compression

testing on at least 3 specimens making 3 measurements across different diameters

Capping Procedures

69Capping

• Daily Check during capping o Check planeness of caps before compression

testing• Three specimens tested at random

o Representing start, middle, and end of run• Use straight edge and feeler gage• Three measurements on different diameters must not

depart from plane by more than 0.002”• Check for hollow areas [Note 15]

Capping Procedures

70Capping

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• Daily Check during compression testingo Thickness of caps on at least three specimens

• Recover at least six pieces of capping material• Measure thickness to the nearest 0.01”• Compare averages and maximum thickness to values

in Table 1

Capping Procedures

71Capping

• Maintain moist cured specimens in moist condition

• Do not store specimens with gypsum plaster caps immersed in water or for more than 4 hours in moist room

• Protect gypsum caps from dripping water• Do not test until strength has developed

in capping material

Protection of Specimens After Capping

72Capping

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UNBONDED CAPS FOR CONCRETE CYLINDERS

ASTM C 1231

78Unbonded Caps

• Practice covers requirements for capping system

• Unbonded neoprene pads are permitted for a specified number of uses up to a certain concrete strength level and then require qualification testing

• Qualification testing is required for all other elastomeric materials

• Unbonded caps not to be used for compressive strength below 1500 psi or above 12,000 psi

Scope

79Unbonded Caps

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• ASTM C42 now referencedo Test Method for Obtaining and Testing Drilled Cores and

Sawed Beams of Concreteo Cores are referenced throughout the specification

Referenced Documents

80Unbonded Caps

• Provides for use of an unbonded capping system in place of capping by ASTM C617

• Pads deform to the contour of the ends of the specimen in metal retainers to provide uniform distribution of the load

Significance and Use

81Unbonded Caps

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• Elastomeric padso Thickness – 1/2 + 1/16”

Materials and Apparatus

82Unbonded Caps

• Elastomeric padso Diameter – not more than 1/16” smaller than the

inside diameter of the retaining ring


83Unbonded Caps

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• Pads shall be made of neoprene• Table 1 provides requirements


84Unbonded Caps

• Elastomeric padso Other elastomeric materials that meet the

performance requirements are permitted.o All elastomeric pads must supply the following

information• Manufacturer or supplier name• Shore A hardness• Applicable range of concrete compressive strength


85Unbonded Caps

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• Elastomeric padso User shall maintain record indicating

• Date pads are put in service• Pad Durometer• Number of uses


86Unbonded Caps

• Retainerso Provide support for and alignment of pads and

test specimenso Height shall be 1.0 ± 0.1”


87Unbonded Caps

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• Retainerso Inside diameter shall not be less than 102% or

greater than 107% of the diameter of cylinder


88Unbonded Caps

• Retainers


89Unbonded Caps

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• Retainerso Surface shall be plane

to within 0.002”o Bearing surfaces of

retainers• No gouges, grooves, or

indents – larger than 0.01” deep or 0.05 in2 in surface area


90Unbonded Caps

• Made according to ASTM C31 or C192 or cores obtained according to C42 (6.1)

Test Specimens

91Unbonded Caps

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• Depressions under a straight edge shall not exceed 0.20”o Measured with round wire gage and straight

edgeo Corrections must be

made before testing• Sawing or grinding

Test Specimens

92Unbonded Caps

• Unbonded caps permitted on one or both ends

• Verify that pads meet specified requirements of Section 5:o ½” thicko Diameter not more that 1/16” smaller than inside

diameter of ringo Pad Hardness and Maximum uses in Table 1

• Insert pad into retainer before placing on cylinder

Test Specimens

93Unbonded Caps

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• Complete testing according to ASTM C39 – Compressive Strength of Cylindrical Concrete Specimens

Test Specimens

94Unbonded Caps

• Polychloroprene (neoprene) Table 1• Other elastomeric materials

• Must be qualified• By supplier or user• Unbonded cap testing compared to tests with

ground or capped cylinders• Average strength obtained using unbonded caps

must not be less than 98% of the average strength of capped/ground cylinders

Qualification of Unbonded Capping Systems and

Verification of Reuse of Pads

95Unbonded Caps

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• Establishing reuseso Additional uses to Table 1o Only tests that are within 2000 psi of highest

strength level can be includedo Records must be maintained



96Unbonded Caps

• Qualification and pad reuse testingo Pairs of cylinders cured alikeo Test one by grinding or capping and one by

unbonded cappingo 10 pairs at both highest and lowest strength

levelso Minimum of two samples made on different

days



97Unbonded Caps

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COMPRESSIVE STRENGTH OF CYLINDRICAL CONCRETE SPECIMENS


99Compressive Strength

• Compressive Strengtho Molded Specimenso Drilled Coreso Limited to concrete with density in excess of

50 lb/ft3

Scope


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• Lower Bearing Blocko Steel piece to distribute the load from the

testing machine to the specimen

• Upper Bearing Blocko Steel assembly suspended above the

specimen that is capable of tilting to bear uniformly on the top of the specimen

• Spacero Steel piece used to elevate the lower

bearing block to accommodate test specimens at various heights

Terminology


• A compressive load is applied to test specimens within a specified range• Compressive strength is

calculated by dividing the maximum load by the cross-sectional area of the specimen

Summary of Test Method


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• Care must be used in interpretation of the results:o Sizeo Shapeo Batchingo Mixing Procedureso Samplingo Moldingo Fabricationo Age, Temperature, and Moisture Conditions

during curing



• Testing Machineo Sufficient Capacityo Capability to provide rates of loading in section

7.5o Verification in accordance with Practice E4

• Within 13 months of last calibration• Original installation or relocation• After repairs or adjustments• Reason to doubt accuracy

Apparatus


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• Design of machine must include:o Continuous application of

load, without shock

Apparatus


• Accuracy:o Percent error shall not exceed + 1.0% of the

indicated loado Verified by five test loads in four equal

increments

Apparatus


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• Two steel bearing blocks with hardened faceso Minimum dimension – 3% larger

than specimen nominal diameter• Spherically seated - upper• Solid block - lower

Apparatus


• Bearing blockso Must not depart from plane by

more than 0.001” in 6”o Larger upper blocks shall have

concentric circles to facilitate centering when larger than specimen diameter more than 0.5”

Apparatus


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• Bearing blockso Top and bottom must be parallelo Concentric circles on bottom block are

optional• 1” thick when new• 0.9” after any

resurfacing

Apparatus


• Final centering of specimen made using upper spherical block• The dimensions of the bearing face

of the upper bearing block:

Apparatus


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• Clean and lubricate the curved surfaces o At least every six monthso As specified by the manufacturero Petroleum type oil

• Motor oil• As specified by

manufacturer

Apparatus


• Clean and lubricate the curved surfaces

Apparatus


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• Load Indicationo Dial• Readable to the nearest

0.1% of full scale loado Digital• Numerical increment

shall not exceed 0.1% of full scale load

Apparatus


• Spacerso If used, spacers shall be placed

under the lower bearing block• Shall be Solid steel• One vertical opening in the

center of the spacer is permissible• Shall fully support the lower

bearing block and any spacers above• Shall not be in direct contact with

the specimen or the retainers of unbonded caps

Apparatus


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• Ends must not depart from perpendicularity to the axis by more than 0.5º (1 mm in 100 mm [0.12” 12”])

Specimens


• Ends that are not plane within 0.002” shall be sawed or ground or capped

Specimens


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• Average diametero Two measurements at right angles taken at

midheight of specimen

Specimens


• Average diametero Measured to 0.01” at midheight

Specimens


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• Specimen shall not be tested if any individual diameter differs from any other diameter by more than 2%o Ratio Range = 0.98 – 1.02oDivide two measurements to find ratio

Specimens


• Do the individual diameters differ from each other by more than 2%? Determine the average diameter.

Ratio

Specimens

P

𝟒.𝟎𝟐 𝟒.𝟎𝟒

𝟐 = = 4.03”𝟖.𝟎𝟔

𝟐

𝟒.𝟎𝟐

𝟒.𝟎𝟒 = .9950

Average Diameter

Range = 0.98 – 1.02


Diameter 1 = 4.02”Diameter 2 = 4.04”

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Diameter 1 = 3.96”Diameter 2 = 4.06”

Practice Problem• Do the individual diameters differ from

each other by more than 2%? Determine the average diameter.


• Average diametero Number measured:• If made from molds that produce average

diameters within a range of 0.02”oOne for each ten specimenso Three per day

• If not, measure every specimen

Specimens


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• Determine length to diameter ratio when less than 1.8 or greater than 2.2

Specimens


• Test in a moist condition• Tolerances on test age for breaking:

Note: For test ages not listed, the test age tolerance is ± 2.0% of the specified age

• Unless otherwise specified, test age will start at the beginning of casting specimens

Procedure


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• Wipe clean the bearing faces of the upper and lower blocks

Procedure


• When using unbonded caps:o Wipe clean the bearing surfaces of the retaining

ringso Center the unbonded caps

on the cylinder

Procedure


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• Align specimen with center of thrust of the upper spherically seated block

Procedure


• Verify that the load indicator is zero

Procedure


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• Tilt the spherically seated block gently by hand so that uniform seating will be obtained

Procedure


• When using unbonded caps:o Verify alignment: • Before reaching 10% of specimen strength• Check that specimen does not depart from

alignment by more than 0.5°o Centered in rings

Procedure


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Procedure


• Apply load continuously and without shock • Stress rate on the specimen of 35 +

7 psi/s (maintained at least during latter half of the anticipated load)• Apply load until specimen failure• Calculate compressive strength

Procedure


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• Compressive Strength

ƒcm= 𝟒 𝑷𝒎𝒂𝒙

𝛑 𝑫𝟐

Pmax = Maximum Loadƒcm = compressive strength

D = average diameter (nearest 0.01”)

Results rounded to the nearest 10 psi

Calculation


• Compressive StrengthCalculate the compressive strength of the cylinder.

Average Diameter = 4.02”Maximum Load = 72,460

Calculation

𝟒 𝟕𝟐,𝟒𝟔𝟎𝛑 𝟒.𝟎𝟐 𝟒.𝟎𝟐

ƒcm

𝟒 𝑷𝒎𝒂𝒙

𝛑 𝑫𝟐

Reported Compressive Strength = 5,710 psi

= 5,709 psi𝟐𝟖𝟗,𝟖𝟒𝟎𝟓𝟎.𝟕𝟔𝟗𝟑𝟗


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• Compressive StrengthCalculate the Reported Compressive Strength of the cylinder.

Average Diameter = 6.01”Maximum Load = 118,550

Practice Problem


• When length to diameter is 1.75 or less:

• Multiply unrounded compressive strength by correction factor then round to the nearest 10 psi

L/D 1.75 1.50 1.25 1.00

Factor 0.98 0.96 0.93 0.87

Calculation


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• Density (if required)o Determine by either of the following 2 methods• Specimen Dimension Method• Submerged Weighing Method

o For either method use a scale that is accurate to within 0.3% of the mass being measured

Specimens


• Density - Specimen Dimension Methodo Remove any surface moisture with a towelo Weigh (before capping)o Measure length to 0.05” at 3 locations around

circumference and averageo Refer to section 9.3.1 for calculation

Specimens


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• Density – Submerged Weighing Methodo Remove any surface moisture

with a towelo Determine weight in airo Submerge the specimen in

water at a temperature of 73.5 ± 3.5°F and determine weight

o Refer to section 9.3.2 for calculation

Specimens


• Density (when required)Calculation

P𝐬𝟔𝟗𝟏𝟐 𝐖

𝐋 𝐃𝟐 𝛑

Where:

Ps = specimen density (lb/ft3)W = mass of specimen in air (lb.)L = average measured length (in.)D = average measured diameter (in.)

P𝐬𝐖 𝐘𝐰

𝐖 𝐖𝐬

Where:

Ps = specimen density (lb/ft3)W = mass of specimen in air (lb.)Ws = apparent mass of submerged

specimen (lb.)Yw = density of water at

73.5°F = 62.27 lb/ft3

Specimen Dimension Method

Submerged WeighingMethod


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Density

W = Mass of specimen (lbs)V = Volume of specimen (ft3)

Calculation

𝐃𝐞𝐧𝐬𝐢𝐭𝐲𝐖𝐕


Find the density of the specimenW = 8.33V = 0.058

Density = 𝐖

𝐕= 𝟖.𝟑𝟑

𝟎.𝟎𝟓𝟖= 143.6 lb/ft3

• Report the following information:

o ID numberoDiameteroCross-sectional areaoMaximum load

oCompressive Strength

o Type of FractureoDefectsoAgeoDensity

Report


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Calculation


Types of Fractures (AASHTO T-22)


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FLEXURAL STRENGTH OF CONCRETE (USING SIMPLE BEAM

WITH THIRD POINT LOADING)


150Flexural Strength

• Covers determination of flexural strength by use of simple beam with third-point loading


Scope

Flexural Strength

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• Standard Size Beam (6”x6”x20”)


Terminology

18”1” 1”

6”6”6”

6”

Span length: Distance between lines of support, or reaction, for the beam specimen, and it is equal to three times the nominal depth of the beam

Flexural Strength

• Flexural Strengtho Bending resistance of a specimen

• Modulus of RuptureoCalculated stress in the tensile face of a

beam specimen at the maximum bending moment

Terminology


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• Loading blocko Used to apply a force to

the beam

• Support blocko Used to support the beam

Terminology


• Strength may vary based on:o Size o Preparationo Moisture conditiono Curingo Molded or sawed

• Results o Used to determine compliance with specificationso Basis for proportioning, mixing and placingo Used in testing concrete for slabs and pavements



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• Shall conform to Practice E 4• Must be capable of applying

load at uniform rate without shock or interruption

Apparatus


• Capable of maintaining span length and distance between the lines of loading within + 0.05”

Apparatus


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• The ratio of the horizontal distance between the line of application of the force and the line of the nearest reaction to the depth of the beam shall be 1.0 + 0.03

Apparatus


• Loading blocks and support blockso Should not be more than 2 ½” higho Extend full width of specimen

Apparatus


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• Test span shall be within 2% of three times the tested depth• Sides shall be at right angles to the

top with smooth surfaces

Test Specimens


• Keep specimen moist between removal of storage and testing

• Turn molded specimen on side for testing

• Position sawed specimens with tension face up or down withrespect to parent material

Procedure


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• Center loading system in relation to applied force

Procedure

20”

3”3” 6”6”

Locate Middle


• Bring load applying blocks into contact and apply a load of between 3 and 6% of the estimated total load

Procedure


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75

• Use feeler gauges (0.004” and 0.015”) to check for gaps over a length of 1”

Procedure


• Grind, cap, or use leather shims to eliminate gaps in excess of 0.004”• Shims

• uniform to ¼” thickness• 1 to 2” wide• Full width of specimen

• Cap or grind only gapsin excess of 0.015”

Procedure


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76

• Load specimen continuously without shock until break occurs

• Apply at a rate that constantly increases the maximum stress on the tension face between 125 –175 psi/min until rupture

Procedure


• Loading rate:

o r = loading rate (lb/min)o S = rate of increase in max stress on

tension face (psi/min)o b = average width (assume 6.00”)o d = average depth (assume 6.00”)o L = span length (assume 18.00”)

𝐫𝑺𝒃𝐝𝟐

𝐋

Procedure


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77

• Loading rate:

𝒓𝑺𝒃𝐝𝟐

𝐋

Procedure𝒓 = loading rate (lb/min)S = 125 (psi/min)b = 6.00”d = 6.00”L = 18.00”

𝟏𝟐𝟓 𝟔.𝟎𝟎 𝟔.𝟎𝟎 𝟔.𝟎𝟎𝟏𝟖

𝒓𝑺 𝒃 𝒅 𝒅

𝐋𝟐𝟕,𝟎𝟎𝟎𝟏𝟖

𝒓 = 1,500 lb/min


Practice Problem

Loading rate:

𝒓𝑺𝒃𝐝𝟐

𝐋

𝒓 = loading rate (lb/min)S = 175 (psi/min)b = 6.00”d = 6.00”L = 18.00”

Given the following information, calculate the Loading rate.


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78

• Determine dimensions across fractured faceo Three measurements across each direction (center

and ends)o Measure to nearest 0.05”o If capped, include capped thickness in measurement

Measurement of Specimen After Test


Caliper Rounding ReviewBeams

= 6.05

6.00 6.056.025


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79

Caliper Rounding ReviewBeams

5.90 5.95 6.00 6.05 6.105.925 5.975 6.025 6.075


Measurement of Specimen After Test


2020

80

• 3 measurements – average width (b)

MEASUREMENT OF SPECIMENS AFTER TEST

(b) = 𝟔.𝟎𝟎 𝟔.𝟎𝟓 𝟔.𝟎𝟓

𝟑 = = 6.033 𝟏𝟖.𝟏

𝟑 = 6.05”


• 3 measurements – average depth (d)

Measurement of Specimens After Test

(d) = 𝟔.𝟎𝟎 𝟔.𝟎𝟎 𝟔.𝟎𝟓

𝟑 = = 6.017 𝟏𝟖.𝟎𝟓

𝟑 = 6.00”


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81

• Fracture in middle third:

o R = modulus of rupture (psi)o P = maximum applied loado L = span length (in.)o b = average width (nearest 0.05”)o d = average depth (nearest 0.05”)

Calculate to the nearest 5 psi

𝐑𝐏𝐋𝐛𝐝𝟐

Calculation


CalculationP = 8260L = 18”b = 6.05”d = 6.00”

𝟖𝟐𝟔𝟎 𝟏𝟖𝟔.𝟎𝟓 𝟔.𝟎𝟎 𝟔.𝟎𝟎

𝟏𝟒𝟖,𝟔𝟖𝟎𝟐𝟏𝟕.𝟖




R = 685 psi

682.64


2020

82

Practice ProblemA beam fractures within the middle third of the span length. Given the following information, calculate the modulus of rupture.


Maximum applied load = 9780Span Length = 18.0”Width 1 = 6.036” Depth 1 = 5.965”Width 2 = 6.012” Depth 2 = 5.982”Width 3 = 5.955” Depth 3 = 5.946”


• Outside the middle third but within 5% of span lengtho For a standard size beam, 18 x 0.05 = 0.9”


5%

5.1 – 6.0” in 5%Tension Face


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• Outside the middle third but within 5% of span lengtho 3 measurements – average width (b)

(b) = 𝟔.𝟎𝟓 𝟔.𝟏𝟎 𝟔.𝟏𝟎

𝟑 = = 6.083 𝟏𝟖.𝟐𝟓

𝟑 = 6.10”



• Outside the middle third but within 5% of span lengtho 3 measurements – average depth (d)


(d) = 𝟔.𝟎𝟓 𝟔.𝟏𝟎 𝟓.𝟗𝟓

𝟑 = = 6.033 𝟏𝟖.𝟏

𝟑 = 6.05”


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84

• Outside the middle third but within 5% of span lengtho 3 measurements – average distance between line

of fracture and nearest support (a)o Measure along the tension face



• 3 measurements – average distance between line of fracture and nearest support (a)

Calculation

5.4

5.7

4.8

(a) = 𝟓.𝟒 𝟓.𝟕 𝟒.𝟖

𝟑 = = 5.3” 𝟏𝟓.𝟗

𝟑

5%

5.1 – 6.0” in 5%Tension Face


2020

85

• Fracture outside middle third but not more than 5% of span length:

o R = modulus of rupture (psi)o P = maximum applied loado b = average width (nearest 0.05”)o d = average depth (nearest 0.05”)o a = average distance between line of fracture and

nearest support (in.)


𝐑𝟑𝐏𝐚𝐛𝐝𝟐

Calculation


CalculationP = 8190b = 6.10”d = 6.05”a = 5.3”

𝟑 𝟖𝟏𝟗𝟎 𝟓.𝟑𝟔.𝟏𝟎 𝟔.𝟎𝟓 𝟔.𝟎𝟓

𝟏𝟑𝟎,𝟐𝟐𝟏𝟐𝟐𝟑.𝟐𝟕𝟓𝟐𝟓

𝐑𝟑𝐏𝒂𝐛𝐝𝟐



R = 585 psi

583.23


2020

86

Practice ProblemA beam fractures outside the middle third but within 5% of the span length. Given the following information, calculate the modulus of rupture.

Maximum applied load = 10120Distance of fracture from nearest support = 5.6”Width 1 = 6.024” Depth 1 = 6.078”Width 2 = 6.029” Depth 2 = 6.083”Width 3 = 6.033” Depth 3 = 6.071”



• Fracture outside middle third by more than 5% of span length:

Calculation

5%

Discard Results

Tension Face


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87

• Id number• Average width (to nearest 0.05”)• Average depth (to nearest 0.05”)• Span length• Maximum applied load• Modulus of rupture• Curing history and apparent moisture at time

of test• If specimens were capped, ground, or if

shims were used• Whether sawed or molded and any defects• Age of specimen

Report
