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
Renewalโข 5 Year Certification
โข 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
โข 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
โข ASTM C 617 (T 231)o Capping Cylindrical Concrete Specimens
โข ASTM C 1231o Use of Unbonded Caps in Determination of
Compressive Strength of Hardened Concrete Cylinders
โข ASTM C 39 (T 22)o Compressive Strength of Cylindrical Concrete
Specimens
โข ASTM C 78 (T 97)o Flexural Strength of Concrete
3
Concrete Strength Testing
Certification Programโข 5 Year Certification
o Written Exam
o Performance Exam
โข Failure of Either Examo Requires retake of failed exam within 1 year
โข Entire written exam
โข Entire performance exam
โข If date is missed, student must retake both exams
o Student is responsible for rescheduling of retake
4
3
Written Exam
โข Questionso Standards
o Special Applications
โข ~ 40 Questionso Multiple Choice
o True / False
o At least 8 questions
on each of the test
methods
โข Limitationso 1 Hour Exam
o Closed Book
โข Passing
Requirementso 60 % Each Standard
o 70 % Overall
5
Performance Exam
โข Passing Requirementso Successfully perform all standards in the
laboratory
โข Two trials are allowed per standard
โข 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
โข 501.03 (Mix Design)o Minimum 28 day compressive strength: 4000 psi
o Test according to AASHTO T22 Compressive
Strength
8ARDOT Standard Specifications
Pavements
5
โข 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
โข AASHTO T 24 Cores and T 23 Cylinders
o Compression Machine
โข Verify and Document
9ARDOT Standard Specifications
Pavements
โข 501.04 (b) (Acceptance Testing)o Acceptance by lot (4000 yd3)
โข Each lot divided into four sublots (1000 yd3)
โข Engineer may establish a partial lot at anytime
o Thickness determination (AASHTO T148)
โข Shall be made from cores sampled for compressive
strength tests
o Compressive strength
โข Determined by testing pavement cores 28 days and no
more than 90 days after concrete placement
โข Remove base course adhering to core
10ARDOT Standard Specifications
Pavements
6
โข 501.04 (b) (Acceptance Testing)o Sampling
โข Contractor
o 1 sample taken at random from each sublot
o ARDOT will determine the location for each sample
using AHTD Test Method 465
โข 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
11ARDOT Standard Specifications
Pavements
โข 802.04 o Bridges, culverts, miscellaneous structures
12ARDOT Standard Specifications
Structures
7
โข 802.06 (a) (Quality Control) o Contractor responsible for testing
o Compressive strength
โข AASHTO T22
โข Minimum of two cylinders cast and tested
o Compression Machine
โข Verify and Document
13ARDOT Standard Specifications
Structures
โข 802.06 (b) (Acceptance Testing)o Acceptance by lot (400 yd3)
โข Each lot divided into four sublots (100 yd3)
โข 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
14ARDOT Standard Specifications
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
โข Minimum diameter of 3.70โo 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
โข Length โ 1.9 to 2.1 times diameterโข Less than 1.75 requires
correction
โข Thickness determination โ T148
16Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
Cores for Compressive Strength
9
โข End preparationo No projections greater than 0.2โ 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 0.1โ
17Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
Cores for Compressive Strength
โข 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
โข To reduce moisture gradients
18Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
Cores for Compressive Strength
10
โข Measure length for L/D ratio
โข Measure two diameterso Do not test if largest and smallest diameter
exceed 5 percent of average
โข Test within 7 days, unless specified
otherwise
โข Test according to T 22
โข Report
19Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
Cores for Compressive Strength
MEASURING LENGTH OF
DRILLED CONCRETE CORES
20
AASHTO T 148
Measuring Length of Drilled Concrete Cores
11
โข 3-point calipering
device (Core length
measuring device)
21Measuring Length of Drilled Concrete Cores
Apparatus
โข Measuring Rodo Shall be rounded to a radius of 0.125โ
o The spacing of the graduations shall be 0.10โ or a decimal part thereof
โข Each increment is 0.10โ
22Measuring Length of Drilled Concrete Cores
Apparatus
12
โข Establish Calibrated
lengtho Verification Gauges
โข Right circular cylinders with
flat ends
โข Diameter approximately
equal to diameter of cores to
be measured
23Measuring Length of Drilled Concrete Cores
Apparatus
โข 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
24Measuring Length of Drilled Concrete Cores
Procedure
13
โข 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 0.05โ
25Measuring Length of Drilled Concrete Cores
Procedure
โข What are these measurements?
26Measuring Length of Drilled Concrete Cores
Procedure
14
โข 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
0.1โ
27Measuring Length of Drilled Concrete Cores
Report
Subtract difference
Calibrated
Length
Example
28Measuring Length of Drilled Concrete Cores
Report
15
CONCRETE STRENGTH TESTING
TECHNICIAN
29
CAPPING CYLINDRICAL
CONCRETE SPECIMENS
30
ASTM C 617
AASHTO T 231
Capping
16
Scope
โข 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
โข SI units and inch-pound units are
includedo May not be exact equivalents so not
interchangeable
31Capping
โข Capping Plateso Neat Cement Caps and
High Strength Gypsum-Pasteโข Glass Plate at least ยผโ thick
โข Machined Metal Plate at least 0.45โ thick
โข Polished Plate of Granite or Diabase at least 3โ thick
o Sulfur Mortar Capsโข Similar to above โ recessed area for
molten sulfur shall not be deeper than ยฝโ
32Capping
Capping Equipment
17
โข Capping Plateso Plates shall be at least 1โ greater in diameter
than specimen
33Capping
Capping Equipment
โข Capping Plateso Working surface shall not depart from plane by
more than 0.002โ in 6โ
34Capping
Capping Equipment
18
โข Capping Plateso Surface shall be free from gouges, grooves,
and indentations
โข Greater than 0.010โ deep, or greater than 0.05 in.2
in surface area
35Capping
Capping Equipment
โข Alignment Deviceso Axis of the alignment device
and the surface of a capping plate
โข Perpendicular to 0.5ยฐ
oNote 2: 1 mm in 100 mm [1/8โ in 12โ]
โข Located so that no cap off-centered by more than 1/16โ
36Capping
Capping Equipment
19
โข 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 405ยฐF
37Capping
Capping Equipment
โข 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
โข Strength and Thickness shall
conform to Table 1
39Capping
Capping Materials
โข 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 0.002โ
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 2โ cubes
40Capping
Capping Materials
21
โข Compressive strength of
capping materials shall be
determined using 2โ cubes
(ASTM C109/AASHTO T106)o Cure same as material capping
cylinders
โข Strength determined on receipt
of new lot and at intervals not
to exceed three months
41Capping
Capping Materials
โข Neat Hydraulic Cement Pasteo Make qualification tests on 2โ cubes
โข 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
โข High-Strength Gypsum Cement
Pasteo Make qualification tests on 2โ cubes
โข To determine effect of w/c ratio and age
o Mix to desired consistency and use promptly
43Capping
Capping Materials
โข Sulfur Mortaro Harden 2 hours โ strengths less than 5000 psi
o Harden 16 hours โ strengths 5000 psi or greater
44Capping
Capping Materials
23
โข Sulfur Mortar o Qualification test
โข Bring apparatus to temperature of 68 to 86ยฐF
โข Lightly coat surfaces with mineral oil
45Capping
Capping Materials
โข Sulfur Mortaro Qualification test
โข Bring mortar temperature to 265 to 290ยฐF
46Capping
Capping Materials
24
โข Sulfur Mortaro Stir sulfur
47Capping
Capping Materials
โข Sulfur Mortaro Fill to top
o Allow for shrinkage
โข Approx. 15 minutes
o Refill with sulfur
48Capping
Capping Materials
25
โข Sulfur Mortaro Allow to solidify
o Remove from molds without breaking knob
49Capping
Capping Materials
โข Sulfur Mortaro Remove oil, sharp edges, and fins
o Check planeness
o Test cubes in compression โ (ASTM C109)
o Calculate compressive strength
50Capping
Capping Materials
26
โข Freshly Molded Cylinderso Use only neat portland cement pastes
o Make as thin as possible
o Do not apply until 2 โ 4 hours after
molding cylinder
51Capping
Capping Procedures
โข Freshly Molded Cylinderso Place conical mound of paste on specimen
52Capping
Capping Procedures
27
โข Freshly Molded Cylinderso Press freshly oiled capping plate until plate
contacts rim of mold
o Cover
o Remove after hardening
53Capping
Capping Procedures
โข Hardened Concrete Specimenso General
โข Remove any coatings or deposits from
cylinder end
54Capping
Capping Procedures
28
โข Hardened Concrete
Specimenso General
โข No point on the end of the
cylinder shall exceed 1/8โ
from plane that is
perpendicular to axis
โข Cut/grind to correct
55Capping
Capping Procedures
โข 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
โข 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
โข Capping with High-Strength
Gypsum Pasteo Form the caps
58Capping
Capping Procedures
30
โข Capping with High-Strength
Gypsum Pasteo Generally, capping plates may be removed
within 45 minutes
59Capping
Capping Procedures
โข Capping with Sulfur Mortaro Heat sulfur between 265
to 290ยฐF
o Check temperature
hourly
o Five use limit
o No reuse for concrete
compressive strength
greater than 5000 psi
60Capping
Capping Procedures
31
โข Capping with Sulfur Mortaro Warm capping device to slow rate of hardening
and permit production of thin caps
61Capping
Capping Procedures
โข Capping with Sulfur Mortaro Oil capping plate lightly
o Stir sulfur before each use
62Capping
Capping Procedures
32
โข Capping with Sulfur Mortaro Ends of specimen must be dry so that steam
pockets or voids greater than ยผโ do not form
63Capping
Capping Procedures
โข Capping with Sulfur Mortaro Pour mortar onto surface of capping plate
64Capping
Capping Procedures
33
โข Capping with Sulfur Mortaro Lift cylinder and use guides to slide the cylinder
onto the capping plate
65Capping
Capping Procedures
โข 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
โข 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
โข Daily Check during capping o Check planeness of caps before compression
testing
โข Three specimens tested at random
o Representing start, middle, and end of run
โข Use straight edge and feeler gage
โข Three measurements on different diameters must not
depart from plane by more than 0.002โ
โข Check for hollow areas [Note 15]
68Capping
Capping Procedures
35
โข Daily Check during compression
testingo Thickness of caps on at least three specimens
โข Recover at least six pieces of capping material
โข Measure thickness to the nearest 0.01โ
โข Compare averages and maximum thickness to values
in Table 1
69Capping
Capping Procedures
โข Maintain moist cured specimens in moist
condition
โข Do not store specimens with gypsum
plaster caps immersed in water or for
more than 4 hours in moist room
โข Protect gypsum caps from dripping water
โข 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
โข Practice covers requirements for capping system
โข Unbonded neoprene pads are permitted for a specified number of uses up to a certain concrete strength level and then require qualification testing
โข Qualification testing is required for all other elastomeric materials
โข Unbonded caps not to be used for compressive strength below 1500 psi or above 12,000 psi
72
Scope
Unbonded Caps
37
โข 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
โข Provides for use of an unbonded capping system in place of capping by ASTM C617
โข 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
โข Elastomeric padso Thickness โ 1/2 + 1/16โ
75Unbonded Caps
Materials and Apparatus
โข Elastomeric padso Diameter โ not more than 1/16โ smaller than the
inside diameter of the retaining ring
76Unbonded Caps
Materials and Apparatus
39
โข Pads shall be made of neoprene
โข Table 1 provides requirements
77Unbonded Caps
Materials and Apparatus
โข Elastomeric padso Other elastomeric materials that meet the
performance requirements are permitted.
o All elastomeric pads must supply the following
information
โข Manufacturer or supplier name
โข Shore A hardness
โข Applicable range of concrete compressive strength
78Unbonded Caps
Materials and Apparatus
40
โข Elastomeric padso User shall maintain record indicating
โข Date pads are put in service
โข Pad Durometer
โข Number of uses
79Unbonded Caps
Materials and Apparatus
โข Retainerso Provide support for and alignment of pads and
test specimens
o Height shall be 1.0 ยฑ 0.1โ
80Unbonded Caps
Materials and Apparatus
41
โข Retainerso Inside diameter shall not be less than 102% or
greater than 107% of the diameter of cylinder
81Unbonded Caps
Materials and Apparatus
โข Retainers
82Unbonded Caps
Materials and Apparatus
42
โข Retainerso Surface shall be plane
to within 0.002โ
o Bearing surfaces of retainersโข No gouges, grooves, or
indents โ larger than 0.01โ
deep or 0.05 in2 in surface
area
83Unbonded Caps
Materials and Apparatus
โข Made according to ASTM C31
or C192 or cores obtained
according to C92 (6.1)
84Unbonded Caps
Test Specimens
43
โข Depressions under a straight edge
shall not exceed 0.20โo Measured with round wire gage and straight
edge
o Corrections must be
made before testing
โข Sawing or grinding
85Unbonded Caps
Test Specimens
โข Unbonded caps permitted on one or
both ends
โข Verify that pads meet specified
requirements of Section 5:o ยฝโ thick
o Diameter not more that 1/16โ smaller than inside
diameter of ring
o Pad Hardness and Maximum uses in Table 1
โข Insert pad into retainer before placing
on cylinder
86Unbonded Caps
Test Specimens
44
โข Complete testing according to
ASTM C39 โ Compressive Strength
of Cylindrical Concrete Specimens
87Unbonded Caps
Test Specimens
โข Polychloroprene (neoprene) Table 1
โข Other elastomeric materialsโข Must be qualified
โข By supplier or user
โข Unbonded cap testing compared to tests with ground or capped cylinders
โข 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
โข 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
Qualification of Unbonded
Capping Systems and
Verification of Reuse of Pads
โข 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
Qualification of Unbonded
Capping Systems and
Verification of Reuse of Pads
46
COMPRESSIVE STRENGTH OF
CYLINDRICAL CONCRETE SPECIMENS
91
ASTM C 39
AASHTO T 22
Compressive Strength
โข Compressive Strengtho Molded Specimens
o Drilled Cores
o Limited to concrete with density in excess of
50 lb/ft3
92
Scope
Compressive Strength
47
โข Lower Bearing Blocko Steel piece to distribute the load from the
testing machine to the specimen
โข Upper Bearing Blocko Steel assembly suspended above the
specimen that is capable of tilting to bear
uniformly on the top of the specimen
โข Spacero Steel piece used to elevate the lower
bearing block to accommodate test
specimens at various heights
93
Terminology
Compressive Strength
โข A compressive load is applied to
test specimens within a specified
range
โข Compressive strength is
calculated by dividing the
maximum load by the cross-
sectional area of the specimen
94Compressive Strength
Summary of Test Method
48
โข 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
95Compressive Strength
Significance and Use
โข Testing Machineo Sufficient Capacity
o Capability to provide rates of loading in section 7.5
o Verification in accordance with Practice E4โข Within 13 months of last calibration
โข Original installation or relocation
โข After repairs or adjustments
โข Reason to doubt accuracy
96Compressive Strength
Apparatus
49
โข Design of machine
must include:o Continuous application of
load, without shock
97Compressive Strength
Apparatus
โข Accuracy:o Percent error shall not exceed + 1.0% of the
indicated load
o Verified by five test loads in four equal
increments
98Compressive Strength
Apparatus
50
โข Two steel bearing blocks
with hardened faceso Minimum dimension โ 3% larger
than specimen nominal diameter
โข Spherically seated - upper
โข Solid block - lower
99Compressive Strength
Apparatus
โข Bearing blockso Must not depart from plane by
more than 0.001โ in 6โ
o Larger upper blocks shall have
concentric circles to facilitate
centering when larger than
specimen diameter more than
0.5โ
100Compressive Strength
Apparatus
51
โข Bearing blockso Top and bottom must be parallel
o Concentric circles on bottom block are
optional
โข 1โ thick when new
โข 0.9โ after any
resurfacing
101Compressive Strength
Apparatus
โข Final centering of specimen made
using upper spherical block
โข The dimensions of the bearing face
of the upper bearing block:
102Compressive Strength
Apparatus
52
โข Clean and lubricate the curved
surfaces o At least every six months
o As specified by the manufacturer
o Petroleum type oil
โข Motor oil
โข As specified by
manufacturer
103Compressive Strength
Apparatus
โข Clean and lubricate the curved
surfaces
104Compressive Strength
Apparatus
53
โข Load Indicationo Dial
โข Readable to the nearest
0.1% of full scale load
o Digital
โข Numerical increment
shall not exceed 0.1% of
full scale load
105Compressive Strength
Apparatus
โข Spacerso If used, spacers shall be placed
under the lower bearing block
โข Shall be Solid steel
โข One vertical opening in the
center of the spacer is permissible
โข Shall fully support the lower
bearing block and any spacers
above
โข Shall not be in direct contact with
the specimen or the retainers of
unbonded caps
106Compressive Strength
Apparatus
54
โข Ends must not depart from perpendicularity to the axis by more than 0.5ยบ (1 mm in 100 mm [0.12โ 12โ])
107Compressive Strength
Specimens
โข Ends that are not plane within 0.002โ shall be sawed or ground or capped
108Compressive Strength
Specimens
55
โข Average diametero Two measurements at right angles taken at
midheight of specimen
109Compressive Strength
Specimens
โข Average diametero Measured to 0.01โ at midheight
110Compressive Strength
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
โข Specimen shall not be tested if any individual diameter differs from any other diameter by more than 2%o Ratio Range = 0.98 โ 1.02
oDivide two measurements to find ratio
112Compressive Strength
Specimens
57
โข Do the individual diameters differ from each other by more than 2%? Determine the average diameter.
Ratio
113Compressive Strength
Specimens
P
(๐.๐๐+๐.๐๐)
๐= = 4.03โ
๐.๐๐
๐
๐.๐๐
๐.๐๐= .9950
Average Diameter
Range = 0.98 โ 1.02
Diameter 1 = 3.96โ
Diameter 2 = 4.06โ
114Compressive Strength
Practice Problem
โข Do the individual diameters differ from each other by more than 2%? Determine the average diameter.
58
โข Average diametero Number measured:
โข If made from molds that produce averagediameters within a range of 0.02โ
oOne for each ten specimens
o Three per day
โข If not, measure every specimen
115Compressive Strength
Specimens
โข Determine length to diameter ratio when less than 1.8 or greater than 2.2 to nearest 0.05 D
116Compressive Strength
Specimens
59
โข Test in a moist condition
โข Tolerances on test age for
breaking:
โข Unless otherwise specified, test
age will start at the beginning of
casting specimens
117Compressive Strength
Procedure
โข Wipe clean the bearing faces of
the upper and lower blocks
118Compressive Strength
Procedure
60
โข When using unbonded caps:o Wipe clean the bearing surfaces of the retaining
rings
o Center the unbonded caps
on the cylinder
119Compressive Strength
Procedure
โข Align specimen with center of
thrust of the upper spherically
seated block
120Compressive Strength
Procedure
61
โข Verify that the
load indicator
is zero
121Compressive Strength
Procedure
โข Tilt the spherically seated block
gently by hand so that uniform
seating will be obtained
122Compressive Strength
Procedure
62
โข When using unbonded caps:o Verify alignment:
โข Before reaching 10% of specimen strength
โข Check that specimen does not depart from
alignment by more than 0.5ยฐ
o Centered in rings
123Compressive Strength
Procedure
124Compressive Strength
Procedure
63
โข Apply load continuously and
without shock
โข Stress rate on the specimen of 35 +
7 psi/s
โข Rate of movement maintained at
least during the latter half of the
anticipated load
โข Apply load until specimen failure
125Compressive Strength
Procedure
โข Compressive StrengthDivide maximum load by cross-sectional area
Cross-sectional area = ๐ ๐ ๐
๐=
๐ ๐ ๐
๐
d = average diameter (nearest 0.01โ)
Compressive Strength = Maximum Load
Crossโsectional area
Results rounded to the nearest 10 psi
126Compressive Strength
Calculation
64
โข Compressive StrengthCalculate the compressive strength of the cylinder.
Average Diameter = 4.02โ
Maximum Load = 72,460
127Compressive Strength
Calculation
=๐ ๐. ๐๐ ๐. ๐๐
๐๐จ๐๐๐ =
๐ ๐ ๐
๐
Comp. Str =Max Load
Area=
๐๐,๐๐๐
๐๐.๐๐= 5,710 psi
= 12.69 in2
โข Compressive StrengthCalculate the Reported Compressive Strength of the
cylinder.
Average Diameter = 6.01โ
Maximum Load = 118,250
128Compressive Strength
Practice Problem
65
โข When length to diameter is 1.75 or
less:
โข 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
129Compressive Strength
Calculation
โข Density (if required)o Determine by either of the following 2 methods
โข Specimen Dimension Method
โข Submerged Weighing Method
o For either method use a scale that is accurate to within 0.3% of the mass being measured
130Compressive Strength
Specimens
66
โข Density - Specimen Dimension Methodo Remove any surface moisture with a towel
o Weigh (before capping)
o Measure length to 0.05โ at 3 locations around circumference and average
o Refer to section 9.3.1 for calculation
131Compressive Strength
Specimens
โข Density โ 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 ยฑ 3.5ยฐF and determine weight
o Refer to section 9.3.2 for calculation
132Compressive Strength
Specimens
67
โข Density (when required)
133Compressive Strength
Calculation
P๐ฌ =๐๐๐๐ ๐
๐ ๐ ๐
Where:
Ps = specimen density (lb/ft3)
W = mass of specimen in air (lb.)
L = average measured length (in.)
D = average measured diameter
(in.)
P๐ฌ =๐ (๐๐ฐ)
๐โ๐๐ฌ
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 73.5ยฐF = 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)
134Compressive Strength
Calculation
๐๐จ๐ฅ๐ฎ๐ฆ๐ =๐ ๐
๐๐๐๐
๐๐๐ง๐ฌ๐ข๐ญ๐ฒ =๐
๐
68
โข DensityFind the density of the specimen
L = 8.00 in.
Area = 12.56 in2
Mass = 8.33 lbs
135Compressive Strength
Calculation
Volume =๐ณ ๐จ
๐๐๐๐=
๐.๐๐ ๐๐.๐๐
๐๐๐๐=
๐๐๐.๐๐
๐๐๐๐= 0.058 ft3
Density =๐
๐=
๐.๐๐
๐.๐๐๐= 143.6 lb/ft3
โข Report the following information:
o ID number
oDiameter
oCross-sectional area
oMaximum load
oCompressive Strength
o Type of Fracture
oDefects
oAge
oDensity
136Compressive Strength
Report
70
FLEXURAL STRENGTH OF
CONCRETE (USING SIMPLE BEAM
WITH THIRD POINT LOADING)
139Flexural Strength
ASTM C 78
AASHTO T 97
โข Covers determination of flexural
strength by use of simple beam
with third-point loading
โข Span Length = 3x the depth140Flexural Strength
Scope
71
โข Standard Size Beam (6โx6โx20โ)
141Flexural Strength
Scope
18โ1โ 1โ
6โ6โ6โ
6โ
โข Results reported as modulus of
rupture
โข Strength may vary based on:o Size
o Preparation
o Moisture condition
o Curing
o Molded or sawed
142Flexural Strength
Significance and Use
72
โข Results o Used to determine compliance with
specifications
o Basis for proportioning, mixing and placing
o Used in testing concrete for slabs and pavements
143Flexural Strength
Significance and Use
โข Shall conform to Practice E 4
โข Must be capable of applying
load at uniform rate without
shock or interruption
144Flexural Strength
Apparatus
73
โข Capable of maintaining span
length and distances between
load-applying blocks constant
within + 0.05โ
145Flexural Strength
Apparatus
โข 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
146Flexural Strength
Apparatus
74
โข Loading blocks and support blockso Should not be more than 2 ยฝโ high
o Extend full width of specimen
147Flexural Strength
Apparatus
โข Test span shall be within 2% of
three times the tested depth
โข Sides shall be at right angles to the
top with smooth surfaces
148Flexural Strength
Test Specimens
75
โข Keep specimen moist between
removal of storage and testing
โข Turn molded specimen on side for
testing
โข Position sawed specimens with tension
face up or down with
respect to parent
material
149Flexural Strength
Procedure
โข Center loading system in relation
to applied force
150Flexural Strength
Procedure
20โ
3โ3โ 6โ6โ
Locate Middle
76
โข Bring load applying
blocks into contact
and apply a load of
between 3 and 6%
of the estimated
total load
151Flexural Strength
Procedure
โข Use feeler gauges (0.004โ and
0.015โ) to check for gaps over a
length of 1โ
152Flexural Strength
Procedure
77
โข Grind, cap, or use leather shims to
eliminate gaps in excess of
0.004โ
โข Shimsโข uniform to ยผโ thickness
โข 1 to 2โ wide
โข Full width of specimen
โข Cap or grind only gaps
in excess of 0.015โ
153Flexural Strength
Procedure
โข Load specimen continuously without shock until break occurs
โข Apply at a rate that constantly increases the
maximum stress on the tension face between 125 โ175 psi/min until rupture
154Flexural Strength
Procedure
78
โข 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 6.00โ)
o d = average depth (assume 6.00โ)
o L = span length (assume 18.00โ)
๐ซ =๐บ๐๐๐
๐
155Flexural Strength
Procedure
โข Loading rate:
๐ =๐บ๐๐๐
๐
156Flexural Strength
Procedure
๐ = loading rate (lb/min)
S = 125 (psi/min)
b = 6.00โ
d = 6.00โ
L = 18.00โ
=๐๐๐ ๐. ๐๐ ๐. ๐๐ (๐. ๐๐)
๐๐๐ =
(๐บ)(๐)(๐ )(๐ )
๐=๐๐, ๐๐๐
๐๐
๐ = 1,500 lb/min
79
157Flexural Strength
Practice Problem
Loading rate:
๐ =๐บ๐๐๐
๐
๐ = loading rate (lb/min)
S = 175 (psi/min)
b = 6.00โ
d = 6.00โ
L = 18.00โ
Given the following information, calculate the Loading rate.
โข Determine dimensions across
fractured faceo Three measurements across each direction (center
and ends)
o Measure to nearest 0.05โ
o If capped, include capped thickness in measurement
158Flexural Strength
Measurement of Specimen
After Test
80
159Flexural Strength
Caliper Rounding Review
Beams
= 6.05
6.00 6.056.025
160Flexural Strength
Caliper Rounding Review
Beams
5.90 5.95 6.00 6.05 6.105.925 5.975 6.025 6.075
81
161Flexural Strength
Measurement of Specimen
After Test
โข 3 measurements โ average width (b)
MEASUREMENT OF SPECIMENS
AFTER TEST
162Flexural Strength
(b) = (๐.๐๐+๐.๐๐+๐.๐๐)
๐= = 6.033 ๐๐.๐
๐= 6.05โ
82
โข 3 measurements โ average depth (d)
163Flexural Strength
Measurement of Specimens
After Test
(d) = (๐.๐๐+๐.๐๐+๐.๐๐)
๐= = 6.017 ๐๐.๐๐
๐= 6.00โ
โข 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 0.05โ)
o d = average depth (nearest 0.05โ)
Calculate to the nearest 5 psi
๐ =๐๐
๐๐๐
164Flexural Strength
Calculation
83
165Flexural Strength
Calculation
P = 8260
L = 18โ
b = 6.05โ
d = 6.00โ
=(๐๐๐๐)(๐๐)
(๐. ๐๐)(๐. ๐๐)(๐. ๐๐)=๐๐๐, ๐๐๐
๐๐๐. ๐
๐ =๐๐
๐๐๐
๐ =๐๐
๐๐๐
Calculate to the nearest 5 psi
R = 685 psi
= 682.64
166Flexural Strength
Practice ProblemA beam fractures within the middle third of the span
length. Given the following information, calculate the
modulus of rupture.
๐ =๐๐
๐๐๐
Maximum applied load = 9780
Span Length = 18.0โ
Width 1 = 6.036โ Depth 1 = 5.965โ
Width 2 = 6.012โ Depth 2 = 5.982โ
Width 3 = 5.955โ Depth 3 = 5.946โ
84
โข Outside the middle third but within
5% of span lengtho For a standard size beam, 18 x 0.05 = 0.9โ
167Flexural Strength
Measurement of Specimens
After Test
5%
5.1 โ 6.0โ in 5%
Tension Face
โข Outside the middle third but
within 5% of span lengtho 3 measurements โ average width (b)
168Flexural Strength
(b) = (๐.๐๐+๐.๐๐+๐.๐๐)
๐= = 6.083 ๐๐.๐๐
๐= 6.10โ
Measurement of Specimens
After Test
85
โข Outside the middle third but
within 5% of span lengtho 3 measurements โ average depth (d)
169Flexural Strength
Measurement of Specimens
After Test
(d) = (๐.๐๐+๐.๐๐+๐.๐๐)
๐= = 6.033 ๐๐.๐
๐= 6.05โ
โข Outside the middle third but within
5% of span lengtho 3 measurements โ average distance between line
of fracture and nearest support (a)
o Measure along the tension face
170Flexural Strength
Measurement of Specimens
After Test
86
โข 3 measurements โ average distance
between line of fracture and nearest
support (a)
171Flexural Strength
Calculation
5.4
5.7
4.8
(a) = (๐.๐+๐.๐+๐.๐)
๐= = 5.3โ
๐๐.๐
๐
5%
5.1 โ 6.0โ in 5%Tension Face
โข 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 0.05โ)
o d = average depth (nearest 0.05โ)
o a = average distance between line of fracture and nearest support (in.)
Calculate to the nearest 5 psi
๐ =๐๐๐
๐๐๐
172Flexural Strength
Calculation
87
173Flexural Strength
Calculation
P = 8190
b = 6.10โ
d = 6.05โ
a = 5.3โ
=(๐)(๐๐๐๐)(๐. ๐)
(๐. ๐๐)(๐. ๐๐)(๐. ๐๐)=
๐๐๐, ๐๐๐
๐๐๐. ๐๐๐๐๐๐ =
๐๐๐
๐๐๐
Calculate to the nearest 5 psi
๐ =๐๐๐
๐๐๐
R = 585 psi
= 583.23
174Flexural Strength
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 = 5.6โ
Width 1 = 6.024โ Depth 1 = 6.078โ
Width 2 = 6.029โ Depth 2 = 6.083โ
Width 3 = 6.033โ Depth 3 = 6.071โ
๐ =๐๐๐
๐๐๐
88
โข Fracture outside middle third by
more than 5% of span length:
175Flexural Strength
Calculation
5%
Discard Results
Tension Face
โข Id numberโข Average width (to nearest 0.05โ)โข Average depth (to nearest 0.05โ)โข Span lengthโข Maximum applied loadโข Modulus of ruptureโข Curing history and apparent moisture at time
of testโข If specimens were capped, ground, or if
shims were usedโข Whether sawed or molded and any defectsโข Age of specimen
176Flexural Strength
Report