Concrete Strength Testing Technician - University of Arkansas · PDF fileo AASHTO T 22 Compressive Strength •AASHTO T 24 Cores and T 23 Cylinders o Compression Machine

1

Concrete Strength Testing

Techniciandeveloped by:

The University of Arkansas, Dept. of Civil Engineering

in conjunction with

The Arkansas Department of Transportation

Basic Aggregates Certification

Renewal• 5 Year Certification

• To prevent expiration :

o Take online Basic Aggregates Certification Renewal course

o Pass final quiz after all online modules are

complete

o Cost - $0

o Extends Basic Aggregates Certification for 5 years

• If not completed prior to expiration date, other

CTTP certifications will be suspended

o Soils, Hot-Mix Asphalt, NPDES, Concrete Field, Concrete Strength

2

2

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

3

Concrete Strength Testing

Certification Program• 5 Year Certification

o Written Exam

o 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 exams

o Student is responsible for rescheduling of retake

4

3

Written Exam

• Questionso Standards

o Special Applications

• ~ 40 Questionso Multiple Choice

o True / False

o At least 8 questions

on each of the test

methods

• Limitationso 1 Hour Exam

o Closed Book

• Passing

Requirementso 60 % Each Standard

o 70 % Overall

5

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 retrial

o Proctor may not stop you

o 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

6

4

ARDOT Standard Specifications

7ARDOT Standard Specifications

• 501.03 (Mix Design)o Minimum 28 day compressive strength: 4000 psi

o Test according to AASHTO T22 Compressive

Strength


Pavements

5

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

by a certified technician

o 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

• 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 tests

o 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

6

• 501.04 (b) (Acceptance Testing)o Sampling

• Contractor

o 1 sample taken at random from each sublot

o ARDOT will determine the location for each sample

using AHTD 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 AHTD Test Method 465


Pavements

• 802.04 o Bridges, culverts, miscellaneous structures


Structures

7

• 802.06 (a) (Quality Control) o Contractor responsible for testing

o Compressive strength

• AASHTO T22

• Minimum of two cylinders cast and tested

o Compression Machine

• Verify and Document


Structures

• 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

8

AASHTO T 24

15Obtaining and Testing Drilled Cores and Sawed Beams of Concrete

OBTAINING AND TESTING

DRILLED CORES AND SAWED

BEAMS OF CONCRETE

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

2x the NMAS, whichever is larger

o 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

9

• End preparationo No projections greater than 0.2” above end

o 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”



• Moisture conditioningo Wipe off surface moisture after drilling

o When surfaces appear dry, but within one hour

store in plastic bags

o Maintain at ambient temperature

o At least 5 days after last being wetted before

testing

• To reduce moisture gradients



10

• Measure length for L/D ratio

• Measure two diameterso 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



MEASURING LENGTH OF

DRILLED CONCRETE CORES

20

AASHTO T 148

Measuring Length of Drilled Concrete Cores

11

• 3-point calipering

device (Core length

measuring device)

21Measuring Length of Drilled Concrete Cores

Apparatus

• 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

12

• Establish Calibrated

lengtho Verification Gauges

• Right circular cylinders with

flat ends

• Diameter approximately

equal to diameter of cores to

be measured


Apparatus

• 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

13

• 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

• What are these measurements?


Procedure

14

• 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

Example


Report

15

CONCRETE STRENGTH TESTING

TECHNICIAN

29

CAPPING CYLINDRICAL

CONCRETE SPECIMENS

30

ASTM C 617

AASHTO T 231

Capping

16

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

31Capping

• 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” thick

o Sulfur Mortar Caps• Similar to above – recessed area for

molten sulfur shall not be deeper than ½”

32Capping

Capping Equipment

17

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

than specimen

33Capping

Capping Equipment

• Capping Plateso Working surface shall not depart from plane by

more than 0.002” in 6”

34Capping

Capping Equipment

18

• 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

35Capping

Capping Equipment

• 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”

36Capping

Capping Equipment

19

• Melting Pots for Sulfur

Mortaro Equipped with automatic

temperature controls

o Metal or lined with material that

is not reactive with molten sulfur

o Use in a hood to exhaust fumes

o Open flame dangerous: flash

point of sulfur is 405°F

37Capping

Capping Equipment

• WARNING:o Melting pot must be located

under a hood with an exhaust

fan

o Well ventilated

o High concentrations are lethal

o Lesser dosages may cause illness

38Capping

Capping Equipment

20

• Strength and Thickness shall

conform to Table 1

39Capping

Capping Materials

• 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 met

o Hardening time

o Compressive strength of 2” cubes

40Capping

Capping Materials

21

• 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

41Capping

Capping Materials

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

• To determine effect of w/c ratio and age

o Mix to desired consistency generally 2 to 4 hours

before paste is to be used

42Capping

Capping Materials

22

• High-Strength Gypsum Cement

Pasteo Make qualification tests on 2” cubes

• To determine effect of w/c ratio and age

o Mix to desired consistency and use promptly

43Capping

Capping Materials

• Sulfur Mortaro Harden 2 hours – strengths less than 5000 psi

o Harden 16 hours – strengths 5000 psi or greater

44Capping

Capping Materials

23

• Sulfur Mortar o Qualification test

• Bring apparatus to temperature of 68 to 86°F

• Lightly coat surfaces with mineral oil

45Capping

Capping Materials

• Sulfur Mortaro Qualification test

• Bring mortar temperature to 265 to 290°F

46Capping

Capping Materials

24

• Sulfur Mortaro Stir sulfur

47Capping

Capping Materials

• Sulfur Mortaro Fill to top

o Allow for shrinkage

• Approx. 15 minutes

o Refill with sulfur

48Capping

Capping Materials

25

• Sulfur Mortaro Allow to solidify

o Remove from molds without breaking knob

49Capping

Capping Materials

• Sulfur Mortaro Remove oil, sharp edges, and fins

o Check planeness

o Test cubes in compression – (ASTM C109)

o Calculate compressive strength

50Capping

Capping Materials

26

• Freshly Molded Cylinderso Use only neat portland cement pastes

o Make as thin as possible

o Do not apply until 2 – 4 hours after

molding cylinder

51Capping

Capping Procedures

• Freshly Molded Cylinderso Place conical mound of paste on specimen

52Capping

Capping Procedures

27

• Freshly Molded Cylinderso Press freshly oiled capping plate until plate

contacts rim of mold

o Cover

o Remove after hardening

53Capping

Capping Procedures

• Hardened Concrete Specimenso General

• Remove any coatings or deposits from

cylinder end

54Capping

Capping Procedures

28

• 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

55Capping

Capping Procedures

• Capping with Neat Cement Pasteo Mix the material as described

o Form caps

o Do not exceed the water-cement ratio

determined in qualification tests

o Neat cement plates may be removed after 12

hours

56Capping

Capping Procedures

29

• Capping with High-Strength

Gypsum Pasteo Mix the material as described

o Do not exceed the water-cement ratio

determined in qualification tests

57Capping

Capping Procedures


Gypsum Pasteo Form the caps

58Capping

Capping Procedures

30


Gypsum Pasteo Generally, capping plates may be removed

within 45 minutes

59Capping

Capping Procedures

• Capping with Sulfur Mortaro Heat sulfur between 265

to 290°F

o Check temperature

hourly

o Five use limit

o No reuse for concrete

compressive strength

greater than 5000 psi

60Capping

Capping Procedures

31

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

and permit production of thin caps

61Capping

Capping Procedures

• Capping with Sulfur Mortaro Oil capping plate lightly

o Stir sulfur before each use

62Capping

Capping Procedures

32

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

pockets or voids greater than ¼” do not form

63Capping

Capping Procedures

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

64Capping

Capping Procedures

33

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

onto the capping plate

65Capping

Capping Procedures

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

positive contact with alignment guides

o Make contact until sulfur hardens

66Capping

Capping Procedures

34

• Daily Check during cappingo Check planeness of caps before compression

testing on at least 3 specimens making 3

measurements across different diameters

67Capping

Capping Procedures

• 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]

68Capping

Capping Procedures

35

• 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

69Capping

Capping Procedures

• 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

70Capping

Protection of Specimens

After Capping

36

UNBONDED CAPS FOR

CONCRETE CYLINDERS

71

ASTM C 1231

Unbonded 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

72

Scope

Unbonded Caps

37

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

Sawed Beams of Concrete

o Cores are referenced throughout the specification

73

Referenced Documents

Unbonded 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

74Unbonded Caps

Significance and Use

38

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

75Unbonded Caps

Materials and Apparatus

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

inside diameter of the retaining ring

76Unbonded Caps


39

• Pads shall be made of neoprene

• Table 1 provides requirements

77Unbonded 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

78Unbonded Caps


40

• Elastomeric padso User shall maintain record indicating

• Date pads are put in service

• Pad Durometer

• Number of uses

79Unbonded Caps


• Retainerso Provide support for and alignment of pads and

test specimens

o Height shall be 1.0 ± 0.1”

80Unbonded Caps


41

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

greater than 107% of the diameter of cylinder

81Unbonded Caps


• Retainers

82Unbonded Caps


42

• 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

83Unbonded Caps


• Made according to ASTM C31

or C192 or cores obtained

according to C92 (6.1)

84Unbonded Caps

Test Specimens

43

• Depressions under a straight edge

shall not exceed 0.20”o Measured with round wire gage and straight

edge

o Corrections must be

made before testing

• Sawing or grinding

85Unbonded Caps

Test Specimens

• Unbonded caps permitted on one or

both ends

• Verify that pads meet specified

requirements of Section 5:o ½” thick

o Diameter not more that 1/16” smaller than inside

diameter of ring

o Pad Hardness and Maximum uses in Table 1

• Insert pad into retainer before placing

on cylinder

86Unbonded Caps

Test Specimens

44

• Complete testing according to

ASTM C39 – Compressive Strength

of Cylindrical Concrete Specimens

87Unbonded Caps

Test Specimens

• 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

88Unbonded Caps

Qualification of Unbonded

Capping Systems and

Verification of Reuse of Pads

45

• Establishing reuseso Additional uses to Table 1

o Only tests that are within 2000 psi of highest

strength level can be included

o Records must be maintained

89Unbonded Caps


Capping Systems and


• Qualification and pad reuse testingo Pairs of cylinders cured alike

o Test one by grinding or capping and one by unbonded capping

o 10 pairs at both highest and lowest strength levels

o Minimum of two samples made on different days

90Unbonded Caps


Capping Systems and


46

COMPRESSIVE STRENGTH OF

CYLINDRICAL CONCRETE SPECIMENS

91

ASTM C 39

AASHTO T 22

Compressive Strength

• Compressive Strengtho Molded Specimens

o Drilled Cores

o Limited to concrete with density in excess of

50 lb/ft3

92

Scope


47

• 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

93

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

94Compressive Strength

Summary of Test Method

48

• Care must be used in interpretation of the results:o Size

o Shape

o Batching

o Mixing Procedures

o Sampling

o Molding

o Fabrication

o Age, Temperature, and Moisture Conditions during curing



• Testing Machineo Sufficient Capacity

o Capability to provide rates of loading in section 7.5

o 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

49

• 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 load

o Verified by five test loads in four equal

increments


Apparatus

50

• 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

51

• Bearing blockso Top and bottom must be parallel

o 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

52

• Clean and lubricate the curved

surfaces o At least every six months

o As specified by the manufacturer

o Petroleum type oil

• Motor oil

• As specified by

manufacturer


Apparatus

• Clean and lubricate the curved

surfaces


Apparatus

53

• Load Indicationo Dial

• Readable to the nearest

0.1% of full scale load

o 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

54

• 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

55

• Average diametero Two measurements at right angles taken at

midheight of specimen


Specimens

• Average diametero Measured to 0.01” at midheight


Specimens

56

111Flexural Strength

Caliper Rounding Review

Cylinders

4.00 3.98

3.99

3.98 3.99 4.00 4.01 4.023.985 3.995 4.005 4.015

4.02

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

oDivide two measurements to find ratio


Specimens

57

• 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 = 3.96”

Diameter 2 = 4.06”


Practice Problem

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

58

• Average diametero Number measured:

• If made from molds that produce averagediameters within a range of 0.02”

oOne for each ten specimens

o Three per day

• If not, measure every specimen


Specimens

• Determine length to diameter ratio when less than 1.8 or greater than 2.2 to nearest 0.05 D


Specimens

59

• Test in a moist condition

• Tolerances on test age for

breaking:

• Unless otherwise specified, test

age will start at the beginning of

casting specimens


Procedure

• Wipe clean the bearing faces of

the upper and lower blocks


Procedure

60

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

rings

o Center the unbonded caps

on the cylinder


Procedure

• Align specimen with center of

thrust of the upper spherically

seated block


Procedure

61

• Verify that the

load indicator

is zero


Procedure

• Tilt the spherically seated block

gently by hand so that uniform

seating will be obtained


Procedure

62

• 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


Procedure

63

• Apply load continuously and

without shock

• Stress rate on the specimen of 35 +

7 psi/s

• Rate of movement maintained at

least during the latter half of the

anticipated load

• Apply load until specimen failure


Procedure

• Compressive StrengthDivide maximum load by cross-sectional area

Cross-sectional area = 𝝅𝒅𝟐

𝟒=

𝛑 𝐝 𝐝

𝟒

d = average diameter (nearest 0.01”)

Compressive Strength = Maximum Load

Cross−sectional area

Results rounded to the nearest 10 psi


Calculation

64

• Compressive StrengthCalculate the compressive strength of the cylinder.

Average Diameter = 4.02”

Maximum Load = 72,460


Calculation

=𝛑 𝟒. 𝟎𝟐 𝟒. 𝟎𝟐

𝟒𝑨𝒓𝒆𝒂 =

𝛑 𝒅 𝒅

𝟒

Comp. Str =Max Load

Area=

𝟕𝟐,𝟒𝟔𝟎

𝟏𝟐.𝟔𝟗= 5,710 psi

= 12.69 in2

• Compressive StrengthCalculate the Reported Compressive Strength of the

cylinder.

Average Diameter = 6.01”

Maximum Load = 118,250


Practice Problem

65

• 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

• 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

66

• Density - Specimen Dimension Methodo Remove any surface moisture with a towel

o Weigh (before capping)

o Measure length to 0.05” at 3 locations around circumference and average

o Refer to section 9.3.1 for calculation


Specimens

• Density – Submerged Weighing Methodo Remove any surface moisture

with a towel

o Determine weight in air

o 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

67

• Density (when required)


Calculation

P𝐬 =𝟔𝟗𝟏𝟐 𝐖

𝐋 𝐃 𝛑

Where:

Ps = specimen density (lb/ft3)

W = mass of specimen in air (lb.)

L = average measured length (in.)

D = average measured diameter

(in.)

P𝐬 =𝐖 (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 Weighing

Method

Density

W = Mass of specimen (lbs)

V = Volume of specimen (ft3)

Volume by measuring specimen

L = Length of specimen (in.)

A = Area of specimen (in2.)

V = Volume in (ft3)


Calculation

𝐕𝐨𝐥𝐮𝐦𝐞 =𝐋 𝐀

𝟏𝟕𝟐𝟖

𝐃𝐞𝐧𝐬𝐢𝐭𝐲 =𝐖

𝐕

68

• DensityFind the density of the specimen

L = 8.00 in.

Area = 12.56 in2

Mass = 8.33 lbs


Calculation

Volume =𝑳 𝑨

𝟏𝟕𝟐𝟖=

𝟖.𝟎𝟎 𝟏𝟐.𝟓𝟔

𝟏𝟕𝟐𝟖=

𝟏𝟎𝟎.𝟒𝟖

𝟏𝟕𝟐𝟖= 0.058 ft3

Density =𝐌

𝐕=

𝟖.𝟑𝟑

𝟎.𝟎𝟓𝟖= 143.6 lb/ft3

• Report the following information:

o ID number

oDiameter

oCross-sectional area

oMaximum load

oCompressive Strength

o Type of Fracture

oDefects

oAge

oDensity


Report

69


Calculation

Types of Fractures (AASHTO T-22)


70

FLEXURAL STRENGTH OF

CONCRETE (USING SIMPLE BEAM

WITH THIRD POINT LOADING)


ASTM C 78

AASHTO T 97

• Covers determination of flexural

strength by use of simple beam

with third-point loading

• Span Length = 3x the depth140Flexural Strength

Scope

71

• Standard Size Beam (6”x6”x20”)


Scope

18”1” 1”

6”6”6”

6”

• Results reported as modulus of

rupture

• Strength may vary based on:o Size

o Preparation

o Moisture condition

o Curing

o Molded or sawed



72

• Results o Used to determine compliance with

specifications

o Basis for proportioning, mixing and placing

o Used in testing concrete for slabs and pavements



• Shall conform to Practice E 4

• Must be capable of applying

load at uniform rate without

shock or interruption


Apparatus

73

• Capable of maintaining span

length and distances between

load-applying blocks constant

within + 0.05”


Apparatus

• The ratio of the horizontal distance

between the point of application of the

load and the point of application of

the nearest reaction to the depth of

the beam shall be 1.0 + 0.03


Apparatus

74

• Loading blocks and support blockso Should not be more than 2 ½” high

o Extend full width of specimen


Apparatus

• 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

75

• 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 with

respect to parent

material


Procedure

• Center loading system in relation

to applied force


Procedure

20”

3”3” 6”6”

Locate Middle

76

• Bring load applying

blocks into contact

and apply a load of

between 3 and 6%

of the estimated

total load


Procedure

• Use feeler gauges (0.004” and

0.015”) to check for gaps over a

length of 1”


Procedure

77

• 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 gaps

in excess of 0.015”


Procedure

• 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

78

• 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”)

𝐫 =𝑺𝒃𝐝𝟐

𝐋


Procedure

• Loading rate:

𝒓 =𝑺𝒃𝐝𝟐

𝐋


Procedure

𝒓 = loading rate (lb/min)

S = 125 (psi/min)

b = 6.00”

d = 6.00”

L = 18.00”

=𝟏𝟐𝟓 𝟔. 𝟎𝟎 𝟔. 𝟎𝟎 (𝟔. 𝟎𝟎)

𝟏𝟖𝒓 =

(𝑺)(𝒃)(𝒅)(𝒅)

𝐋=𝟐𝟕, 𝟎𝟎𝟎

𝟏𝟖

𝒓 = 1,500 lb/min

79


Practice Problem

Loading rate:

𝒓 =𝑺𝒃𝐝𝟐

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.

• 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

80



Beams

= 6.05

6.00 6.056.025



Beams

5.90 5.95 6.00 6.05 6.105.925 5.975 6.025 6.075

81


Measurement of Specimen

After Test

• 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”

82

• 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”

• Fracture in middle third:

o R = modulus of rupture (psi)

o P = maximum applied load

o L = span length (in.)

o b = average width (nearest 0.05”)

o d = average depth (nearest 0.05”)

Calculate to the nearest 5 psi

𝐑 =𝐏𝐋

𝐛𝐝𝟐


Calculation

83


Calculation

P = 8260

L = 18”

b = 6.05”

d = 6.00”

=(𝟖𝟐𝟔𝟎)(𝟏𝟖)

(𝟔. 𝟎𝟓)(𝟔. 𝟎𝟎)(𝟔. 𝟎𝟎)=𝟏𝟒𝟖, 𝟔𝟖𝟎

𝟐𝟏𝟕. 𝟖

𝐑 =𝐏𝐋

𝐛𝐝𝟐

𝐑 =𝐏𝐋

𝐛𝐝𝟐


R = 685 psi

= 682.64


Practice ProblemA beam fractures within the middle third of the span

length. Given the following information, calculate the

modulus of rupture.

𝐑 =𝐏𝐋

𝐛𝐝𝟐

Maximum applied load = 9780

Span 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”

84

• Outside the middle third but within

5% of span lengtho For a standard size beam, 18 x 0.05 = 0.9”



After Test

5%

5.1 – 6.0” in 5%

Tension Face

• 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”


After Test

85

• Outside the middle third but

within 5% of span lengtho 3 measurements – average depth (d)



After Test

(d) = (𝟔.𝟎𝟓+𝟔.𝟏𝟎+𝟓.𝟗𝟓)

𝟑= = 6.033 𝟏𝟖.𝟏

𝟑= 6.05”

• 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



After Test

86

• 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

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

o R = modulus of rupture (psi)

o P = maximum applied load

o 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.)


𝐑 =𝟑𝐏𝐚

𝐛𝐝𝟐


Calculation

87


Calculation

P = 8190

b = 6.10”

d = 6.05”

a = 5.3”

=(𝟑)(𝟖𝟏𝟗𝟎)(𝟓. 𝟑)

(𝟔. 𝟏𝟎)(𝟔. 𝟎𝟓)(𝟔. 𝟎𝟓)=

𝟏𝟑𝟎, 𝟐𝟐𝟏

𝟐𝟐𝟑. 𝟐𝟕𝟓𝟐𝟓𝐑 =

𝟑𝐏𝒂

𝐛𝐝𝟐


𝐑 =𝟑𝐏𝐚

𝐛𝐝𝟐

R = 585 psi

= 583.23


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 = 10120

Distance 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”

𝐑 =𝟑𝐏𝐚

𝐛𝐝𝟐

88

• Fracture outside middle third by

more than 5% of span length:


Calculation

5%

Discard Results

Tension Face

• 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