Quality Control Testing

Mississippi Concrete IndustriesAssociation

Robert Varner, P.E.

Topics For Discussion

Some Basis for Specifications Plastic Concrete Properties and Field

Test Curing & Handling Cylinders ASTM C94 Overview

Specification RequirementsCompressive Strength f’c

General-use concrete:3000 to 5000 psi

High-Strength: 6000to 20,000+ psi

Known relationshipswith other concreteproperties

Specification RequirementsFlexural Strength (MR)

Typical values: 450to 750 psi @ 28days

650 to 750 psicommon forpavements

Normal weightconcreteapproximation: MR= (7.5 to 10) (f’c)0.5

Specification RequirementsMix Proportions

Maximum Water Cement Ratio– Table 9-1, 9-2 Pg 150– Make sure w/c correlates with strength

Minimum Cement– Table 9-7 Pg 156

Specification RequirementsFreshly Mixed Properties

Air Content– Table 8-6 Pg 146

Slump– Table 9-3 Pg 155

Temperature– Maximum Pg 229– Minimum Temperature Table 14-1 Pg 243

Specification RequirementsMaterials Material Requirements

– Cement - ASTM C 150– Fly Ash - ASTM C 618– GGBFS - ASTM C 989– Aggregate - ASTM C 33

Note 2 – Allows the use of state agencygrading requirements.

Specification RequirementsMDOT VS ASTM Fine Agg.Sieve ASTM C33

Percent PassingMDOT

Percent Passing½ inch Na 1003/8 inch 100 97 – 100No. 4 95 – 100 92 – 100No. 8 80 – 100 75 – 100No. 16 50 – 85 45 – 100No. 30 25 – 60 25 – 70No. 50 10 – 30 3 – 35No. 100 2 - 10 0 – 10

Testing Freshly MixedConcrete

Sampling - ASTM C172 Slump - ASTM C143 Temperature - ASTM C1064 Density - ASTM C138 Air Content - ASTM C231/C173 Strength Specimens - ASTM C31

Sampling - ASTM C 172

1 ft3

Composite sample Middle of truck Protect sample

Slump - ASTM C143

Consistency: Theability of freshlymixed concrete toflow as measured inthe slump test.(expressed ininches of slump)

Temperature ASTM C1064• Affects concrete behavior• May be important in trouble-shooting problems• May be a specification issue

Density - ASTM C138 Density (Unit

Weight)– Weight of concrete

divided by a knownvolume.

– Conventional concretehas a unit weight inthe range of 137 to150 pcf Lightweight: 15 pcf Heavyweight: 375 pcf

– Measured primarily tocompute yield

Yield

Yield is the volume of concrete produced in abatch (typically expressed in yd 3)

yield = Batch weights (Cement,FA,CA,H2O)Unit Weight

Air ContentASTM C 173 - ASTM C231 Measures entrained (tiny) and entrapped

(larger) air voids, expressed as a percentageof the total volume of concrete

Entrained: generally 0.0004” to 0.04” Ø Entrapped: 0.04” Ø and up Somewhat a function of aggregate

characteristics– Non-air-entrained concrete w/ 1” coarse

aggregate has about 1-1/2% entrapped air

Volumetric MethodASTM C173

Pressure Method ASTM C231

Strength Specimens

Cylinders– 6 X 12– 4 X 8

Beams– 6 X 6 X 20

Curing Specimens– Standard curing– Field curing

Making & CuringConcrete Test Specimens

ASTM C31 Field

ASTM C192 Lab

Compressive Strength ofCylindrical Specimens

ASTM C39

ASTM C 78Flexural Strength -Third Point Loading

Making & Curing ConcreteTest SpecimensASTM C31 FieldASTM C192 Lab

Standard Curing

Curing procedures required by ASTMC 31 for strength specimens that aremade for:– Acceptance testing

– Checking adequacy of mix proportions– Quality control

Includes 2 curing stages:– Initial curing– Final curing

Initial Curing

Temperature– < 6000 psi – 60 to

80 ° F– ≥ 6000 psi – 68 to

78 ° F Moisture

– Prevent moistureloss

Time– Up to 48 hours

Transportation ofCylinders To Laboratory

Wait 8 hours after final set Protect with suitable cushioning material Protect from freezing Prevent moisture loss Transportation time not to exceed 4 hours

Final Curing

Temperature– 73° ± 3° F

Moisture– Free moisture on

surface at all times

Time– Within 30 minutes

after removing themolds until testing

Field CuringTemperature and moisture conditions as closeas possible to those of the in-place concretefor curing specimens that are made for:

– Strength verification prior to putting the structureor pavement into service

– Comparison with test results of standard curedspecimens or various in-place test methods

– Adequacy of curing and protection of concrete inthe structure

– Strength check for form or shoring removal

ASTM C 94 Overview

The Standard Specification forReady-Mixed Concrete

ASTM C 94: StandardSpecification For Ready-MixedConcrete By reference in project specifications

controls the following:– Materials– Mix-Design Procedures– Batching, Mixing, and Delivery Procedures– Acceptance Criteria– Acceptable Tolerances– Required Quality Control Testing

Sect. 4: Basis of Purchase

Sect. 4.2: Unit Weight C 138– Average of at least 3 measurements– Sample taken from midpoint of 3 different

trucks using C 172

Sect. 5: OrderingInformation

• Sect. 5.1: In the absence of applicablegeneral specifications, the purchaser shallspecify the following: Coarse Aggregate Size Slump Air Content Unit Weight - structural lightweightMix Design Options: A,B,C

Sect. 7.1.1: Slump Tolerances IfSpecified AS Maximum

To Be Used Only If One Addition Of Water IsPermitted

Plus Tolerance:Minus Tolerance:

Specified Slump:If 3 in. If more thanOr less 3 in.

0 01 1/2” 2 1/2”

Sect. 7.1.2: Slump TolerancesIf Not Specified AS Maximum

Tolerances For Normal Slumps

For Specified Slump of:

2 in. and lessMore than 2 through 4 in.More than 4 in.

Tolerance

± 1/2 in.± 1 in.

± 1 1/2 in.

Slump

Sect. 7.2– Producer responsible for slump to be in

tolerance range for a period of 30 min. startingeither on the arrival at the job site or after theinitial slump adjustment permitted in 12.7,whichever is later. Exemptions:

– First and Last 1/4 yd3

Sect. 12.7– Allows for one time addition of water.

Air

Sect. 8– Table 1 - Recommended Total Air

Content– Sect. 7.2: Tolerance of ± 1.5

Discharge of Concrete

Sect. 12.7– Completed within 1 ½ hours– Or before drum has revolved 300

revolutions– Whichever comes first

Sect. 12.8: Minimum ConcreteTemperature As Placed

Section Size, in.

<1212-3636-72>72

Temperature, min F

55504540

Concrete temperature shall not exceed 90F whenusing heated materials.

Required Quality ControlTesting Sect. 17.2 Technician Certification Sect. 17.4 Required Test

– Slump, Air Content, Density, Temperature,Strength

Sect. 17.5 Required Frequency– Strength

one per day per class of concrete or every150 yd3

– Slump, Air Content, Density, Temperature witheach strength test and as necessary for controlchecks .

Strength Criteria ForConcrete Acceptance

Sect. 18.1: Cylinders Made and Cured AccordingTo ASTM C 31

Sect. 18.2: One Test = Two Cylinder Breaks– Can a cylinder be discarded?

Sect. 18.4: Two Requirements For Strength– Average of any three consecutive test f’c

and f’c ≤ 5000 - No test more than 500psi below f ‘c f’c > 5000 – No test less than 0.90 f’c

Required Average CompressiveStrength With Standard DeviationTable X1.1

f’c ≤ 5000 psi– f ‘cr = f ‘c +1.34s– f ‘cr = f ‘c +2.33s-500(psi)

f’c >5000 psi– f’cr = f’c + 1.34s– f’cr = 0.90f’c + 2.33s

– s = Standard Deviation

Required Average CompressiveStrength Without Standard DeviationTable X1.2

Specified Compressive

Strength, f’c (psi)

Less Than 3000

3000 to 5000

Over 5000

Required AverageCompressive Strengthf’c (psi)

f ’c + 1000

f ’c + 1200

1.10f ’c + 700

QC / QA Concepts

Quality Control / Quality Assurance Responsibility to Contractor Performance Based

– Statistical Controlled– Data Comparisons– Pay Reductions

Questions?Mississippi Concrete IndustriesAssociationPhone: (601) 957-5274email:rvarner@mississippiconcrete.comwebsite: mississippiconcrete.com