for an aci certification how do you make quality …...the precast show 1/30/2020 npca 1...
TRANSCRIPT
The Precast Show 1/30/2020
NPCA 1
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TIPS FROM AN EXPERT ON PREPARING FOR AN ACI CERTIFICATION
Luke M. Snell, P.E., FACI
Concrete Consultant
Edwardsville, IL
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How do you make Quality Concretethat will have durability?
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How do we make sure we get the Quality Concrete that we need?
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Research shows that we
need concrete that has:
1. low water/cementitious material
ratio
2. air content of about 6%
3. uniform and consistent mixtures
4. temperature control (40- 95 F)
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The ACI debated how to get quality concrete for three years!
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They decided one of the keys to Quality Concrete is qualified Concrete Technicians to provide accurate and reliable test results
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ACI started the first of many certification programs:
Field Grade I Certification Program – 1983
Missouri was one of the first certifications
Building Code now requires all Testing Technicians be ACI certified
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What is required to be certified?
Understand the American Society for Testing and Materials (ASTM) Standards for Concrete by:
Passing a 55 question Multiple Choice Test on the details of the test methods
AND
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WHAT IS REQUIRED TO BE CERTIFIED?
Demonstrate the ability to perform each test accurately:
1. Sampling
2. Making of Test Specimens (cylinders)
3. Slump
4. Unit Weight
5. Air Content – Volumetric
6. Air Content – Pressure
7. Temperature
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1. Sampling
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2. Making Test Specimens (Cylinders)
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3. Slump
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4. Unit Weight
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5. Air Content – Volumetric
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6. Air Content – Pressure
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7. Temperature
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PROGRAM HAS BEEN EXTREMELY SUCCESSFUL
▪ Over 100,000 Certified Technicians
This is now required by IBC, ACI 318 and ASTM C 94 as the standard for testing concrete in the field and at the precast plant
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FIELD GRADE I
Offered only by approved sponsoring groups
Each area has only one sponsoring group
You can send people to other areas to become certified
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FIELD GRADE I
The sponsoring group may or may not have a review class
You should NOT depend on the review class to train your employee
You must be pro-active and get your employees ready to pass the exam
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FIELD GRADE I
To pass the exam they should:
1. Have the current ASTM Standards
2. Answer all the questions in the ACI study book
3. Do each test with an experienced technician
4. Practice Practice, Practice !!!
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OTHER CERTIFICATIONS AVAILABLE
Laboratory Testing was added to qualify Technicians that doing routine testing in the Lab
Includes both Strength and Aggregates Certifications
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LABORATORY CERTIFICATIONS
Strength Testing
1. Capping a cylinder
2. Testing with unbonded caps
3. Compression testing
4. Flexural testing
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All people that break cylinders are suppose to have this certification
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LABORATORY CERTIFICATIONS
AGGREGATES TESTING1. Sampling
2. Reduction of sample size
3. Sieve Analysis and Fineness Modulus
4. Specific Gravity (Coarse and Fine)
5. Moisture content
6. % passing the #200 sieve
7. Organic Impurities
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LAB 2
1. Evaluations of Test Results
2. Developing a Concrete Mixtures
3. Evaluations of Cylinder Molds
(Multi Use and Single Use)
4. Obtaining and Testing Cores
5. Shrinkage Testing of Mortar and Concrete
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SPECIAL INSPECTOR
One of ACI Highest Inspector Certification
This person responsible for QC
Makes sure forms, reinforcement
placement, curing, testing, form removal,
etc. are done correctly
Recommended for your QA/QC Personal
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SPECIAL INSPECTOR
3 Day Class (optional) with a comprehensive 3 hour exam and a 1 hour plans reading exam
½ - 5 years of inspection experience required - depends on your education
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SPECIAL INSPECTOR
Excellent class for Beginning Engineers, QA/QC Managers, Field Engineer, Project Managers
Covers over 1000 pages of ACI Documents
Information not typically covered in Engineering Classes but needed on the jobsite/plant
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ACI CERTIFIED PERSONNEL RESIDE IN54 COUNTRIES, TRULY INTERNATIONAL
Aruba
Australia
Bahamas
Barbados
Bolivia
Brazil
Canada
Cayman Islands
Chili
China
Colombia
Costa Rica
Cuba
Dominican Republic
Ecuador
Egypt
El Salvador
Estonia
Panama
Peru
Philippines
Qatar
Singapore
Russia
Saint Lucia
Saudi Arabia
Sweden
SyriaTaiwanTajikistanTrinidad & TobagoTurks & Caicos Islands
UAEUK
USAVenezuela
Germany
Greece
GuatemalaIcelandIndiaIranJamaica
Jordan KuwaitLatviaLebanonMacau
MexicoMongoliaMoroccoNew ZealandNorway
Pakistan
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FOR MORE INFORMATION ON CERTIFICATION
Check your local ACI or ready mixed concrete association
or
www.concrete.org
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WHAT CAUSES LOW STRENGTH TESTS RESULTS
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Bad test results usually blamed
on defective sampling/testing
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a)How routine “mistakes” influence in sampling/testing influence compressive strength
b)Is the statement “Nothing you do in the field will increase the strength of the concrete test specimens” correct?
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Selected a long term concrete project
Make one set of cylinders per ASTM Standards
From the same sample, a second set of cylinders (with known violation to the procedure) were made
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A “snapshot” of the effects of a
defect
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Design Strength – 4000 psi
Slump – 5 - 6 inches
Air Content – 6 ± 1%
Average Range (difference between two cylinders @ 28 days for the ASTM testing) – 125 psi
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Violation # 1 - Etching top
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Etch top
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Etching: Note depth of etchprecast.org/education
Violation # 2 – Using Rebar
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Using Rebar
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Violation # 3
Using
Grade Pin
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Cylinder made with grade pinprecast.org/education
Cylinder made with grade pin
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Violation # 4 - Filling “Tubes”
(cylinder molds) by scooping
concrete into moldsprecast.org/education
Violation # 5 - Field curing
without covers
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Violation # 6
Cylinder made
without rodding
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Violation # 7
Cylinder made
without
tapping sides
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Violation of ASTM Strength
Gain (+) or
Loss (-)
7 day - %
Strength
Gain (+) or
Loss (-) 28
day - %
Range (Difference
between 2
cylinders) 28 day -
psi
No lids (-5) +3 300
No tapping sides +5 (-2) 350
1 lift (-17) (-7) 40
No rodding / tapping
sides
(-1) +2 440
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Violation of ASTM Strength
Gain (+) or
Loss (-)
7 day - %
Strength
Gain (+) or
Loss (-) 28
day - %
Range
(Difference
between 2
cylinders) 28 day
- psi
From chutes, no
rodding , no tapping
sides
(-9) (-12) 1130
Date “etched” on top
of cylinder, no lids
(-11) +2 510
Use rebar to rod
cylinders, no tapping
sides, no lids
(-1) (-6) 230
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Violation of ASTM Strength
Gain (+) or
Loss (-)
7 day - %
Strength
Gain (+) or
Loss (-) 28
day - %
Range
(Difference
between 2
cylinders) 28
day - psi
Initial cure (24 hr) air
temperature of 30F
(-3) (+3) 30
Initial cure (24 hr) air
temperature
exceeded 120F (in
curing box with 90
watt bulb)
(-29) (-29) 90
Hauled loosely in
truck
0 +2 70
6 day field cure,
hauled loosely in
back of truck
+2 +6 50
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Violation of ASTM Strength
Gain (+) or
Loss (-)
7 day - %
Strength
Gain (+) or
Loss (-) 28
day - %
Range
(Difference
between 2
cylinders) 28
day - psi
Dropped 2 ½ ´ (from
tailgate) onto
concrete slab after
24 hr cure
(-6) (-18) 60
Tipped over after 2
hours, hauled
loosely in truck
+1 (-1) 300
Rodded with grade
pin, holes in bottom
of molds
0 +3 110
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Violation of ASTM % LOSS
Initial cure (24 hr.) exceeded 120F (-29)
(in curing box with 90 watt bulb)
1 Lift (-17)
Date “etched” on top of cylinder, no lids (-11)
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Violation of ASTM % Loss
Initial cure (24 hr) exceeded 120F (-29)
(in curing box with 90 watt bulb)
Dropped 2 ½ ´ (from tailgate) (-18)
onto concrete slab after 24 hr cure
From chute, no rodding, no tapping (-12)
sides
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Violation of ASTM Range (Difference between
two cylinders at 28 days) psi
From chute, no rodding , 1130
no tapping sides
Date “etched” on top of 510
cylinder, no lids
No rodding / tapping sides 440
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Violation of ASTM Range (Difference between
two cylinders at 28 days) psi
No tapping sides 350
No lids 300
Tipped over after 300
2 hours, hauled
loose in truck
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What Problems are we likely to see?
Field Cured Cylinders
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Did multiple samples
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Variations Caused by Field Cured Cylinders
Field Conditions:
Air temperature 20°– 57°F
Average air temperature 37°F
Concrete temperatures (as placed) 47°– 80°F
Average concrete temperature 68°F
(30 Test Results)
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% Loss
7 day strength (-23)
28 day strength (-15)
28 day standard deviation - 28% higher
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7 day - field cured cylinders
28 day - field cured cylinders
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Condition Strength loss
Rough Ends up to 12%
Rough Handling up to 7%
Rebar Rodding up to 2%
Field Curing (7 days) up to 26%
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RESEARCH ON CURING
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• Bucket Air Cured
• Bucket Water Cured
• Cooler Water Cured
• Cooler Damp Sand
• Cooler Zonolite
• Control Standard Laboratory Water Cured
• Initial Curing 72 hours
• Design: 705 lbs Cement @ 0.41w/c ratio
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Water Cured
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100
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Te
mp
era
ture
oF
Time hrs.
Temperature (°F)of
Standard Laboratory Water Cured Cylinder
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Field Curing Five Gallon Bucket
Insulating Material - None Air Cured
4/4/2008 Start 9:23 am
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10.0
20.0
30.0
40.0
50.0
60.0
70.0
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90.0
100.0
110.0
120.0
130.0
140.0
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Time, hrs.
Te
mp
era
ture
F
Ambient
Cylinder Temp
Bucket Temp
Cylinder Avg. temp.
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Field Curing Five Gallon Bucket
Insulating Material - Water
4/4/2008 Start 9:32 am
0
10
20
30
40
50
60
70
80
90
100
110
120
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84
Time, hrs.
Te
mp
era
ture
F
Ambient
Cylinder Temp
Water Temp
Cylinder Avg. temp
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Cylinder Curing Conditions
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5500
6000
6500
7000
7500
8000
8500
9000
9500
Bucket + Cold
Water
Bucket + Air Bucket +
Water
Cooler + Water Cooler + Sand Cooler +
Zonzlite
Std Lab Cured
Water
Co
mp
ressiv
e S
tren
gth
psi
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• Our test results agree with other research results.
• Violation to ASTM can give you unexpected results.
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To keep cylinders from going bad,
you must eliminate the
“Effects of Defects”!!!
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WAYS TO BE IMPROVE YOUR SUCCESS RATE WITH ACI’S
CERTIFICATION EXAMS
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a. Answer is written in the box
b. If you change an answer, completely erase it– Do NOT cross off the answer and thenwrite the correct answer next to the crossedoff answer. Write the correct answer in thebox.
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The fuel used in the modern automobile engine is:
A. Salt Water
B. Uranium
C. Gasoline
D. Plutonium
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You may have read about a method of separating sea (salt) water into Hydrogen and Oxygen and using Hydrogen as a fuel; but this is NOT common.
Thus, the best answer is
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EXAMPLE:
Which of the following is not a part of the definition of the slump cone rod?
A. 5/8 inch (16 mm) diameter
B. Hemispherical tipped end
C. Straight steel rod
D. 48 inch (1200 mm) length
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The key words are: and slump cone rod– circle or underline these words.
The correct answer is D
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Some questions have more than one
answer
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Which of the following is part of the
description of the slump cone rod?
A. 5/8 inch (16 mm) diameter
B. Hemispherical tipped end
C. Straight steel rod
D. All of the above
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Step 1: Select the key words: is and slumpcone rod
Step 2: Read all of the answers: “A” is a correct answer but so is “B” and so is “C”
If you stopped reading at “A” and gave that as your answer, it would be wrong.
By reading ALL of the answers, you should select D
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Key words are: height and slump cone
If you don’t remember, close your eyes and visualize the slump cone. Hold your hands at the approximate height, likely you’ll remember it is 12 inches (300 mm); so the correct answer is B
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The temperature of cement as it enters a concrete mix is typically specified to be:
A. Between 180 – 185 F (82 – 85 C)
B. Less than 180 F (82 C)
C. 185 – 190 F (85 – 88 C)
D. 210 F (99 C)
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TEMPERATURE, CEMENT, ENTERS, AND SPECIFIED
If you do not know the correct answer:
Ask yourself – Do we heat the cement in cold weather to get it into a higher temperature or in a range?
The answer to that is NO, so we can cross off “A”, “C”, and “D” as possible answers. That leaves you with B as the correct answer.
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DO NOT GET HUNG UP ON THE QUESTIONS YOU DO NOT KNOW THE ANSWERS
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I recommend that you answer the questions in the exam book, then put answers on the answer sheet.
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If all else fails, guess at an the answer
Any answer is better than NO ANSWER.
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10. You MUST get an over all score of 70%
and
60% on each ASTM Standard
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The goal is to become
certified!
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