Quality Control Testing Mississippi Concrete Industries Association Robert Varner, P.E.

Topics For Discussion Some Basis for Specifications Plastic Concrete Properties and Field Test Curing & Handling Cylinders ASTM C94 Overview

Specification Requirements Compressive Strength f’c General-use concrete: 3000 to 5000 psi High-Strength: 6000 to 20,000+ psi Known relationships with other concrete properties

Specification Requirements Flexural Strength (MR) Typical values: 450 to 750 psi @ 28 days 650 to 750 psi common for pavements Normal weight concrete approximation: MR = (7.5 to 10) (f’c)0.5

Specification Requirements Mix 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 Requirements Freshly 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 Requirements Materials 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 agency grading requirements.

Specification Requirements MDOT VS ASTM Fine Agg. Sieve ASTM C33 Percent Passing MDOT Percent Passing ½ inch Na 100 3/8 inch 97 – 100 No. 4 95 – 100 92 – 100 No. 8 80 – 100 75 – 100 No. 16 50 – 85 45 – 100 No. 30 25 – 60 25 – 70 No. 50 10 – 30 3 – 35 No. 100 2 - 10 0 – 10

Testing Freshly Mixed Concrete 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: The ability of freshly mixed concrete to flow as measured in the slump test. (expressed in inches 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 known volume. Conventional concrete has a unit weight in the range of 137 to 150 pcf Lightweight: 15 pcf Heavyweight: 375 pcf Measured primarily to compute yield

yield =  Batch weights (Cement,FA,CA,H2O) Unit Weight Yield is the volume of concrete produced in a batch (typically expressed in yd 3) yield =  Batch weights (Cement,FA,CA,H2O) Unit Weight

Air Content ASTM C 173 - ASTM C231 Measures entrained (tiny) and entrapped (larger) air voids, expressed as a percentage of 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 Method ASTM C173

Pressure Method ASTM C231

Strength Specimens Cylinders Beams Curing Specimens 6 X 12 4 X 8 Standard curing Field curing

Making & Curing Concrete Test Specimens ASTM C31 Field ASTM C192 Lab Compressive Strength of Cylindrical Specimens ASTM C39

Making & Curing Concrete Test Specimens ASTM C31 Field ASTM C192 Lab ASTM C 78 Flexural Strength - Third Point Loading

Standard Curing Curing procedures required by ASTM C 31 for strength specimens that are made for: Acceptance testing Checking adequacy of mix proportions Quality control Includes 2 curing stages: Initial curing Final curing

Initial Curing Temperature Moisture Time < 6000 psi – 60 to 80 ° F Prevent moisture loss Time Up to 48 hours

Transportation of Cylinders 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 Moisture Time 73° ± 3° F Free moisture on surface at all times Time Within 30 minutes after removing the molds until testing

Field Curing Temperature and moisture conditions as close as possible to those of the in-place concrete for curing specimens that are made for: Strength verification prior to putting the structure or pavement into service Comparison with test results of standard cured specimens or various in-place test methods Adequacy of curing and protection of concrete in the structure Strength check for form or shoring removal

The Standard Specification for Ready-Mixed Concrete ASTM C 94 Overview The Standard Specification for Ready-Mixed Concrete

ASTM C 94: Standard Specification For Ready-Mixed Concrete 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: Ordering Information Sect. 5.1: In the absence of applicable general specifications, the purchaser shall specify the following: Coarse Aggregate Size Slump Air Content Unit Weight - structural lightweight Mix Design Options: A,B,C

Sect. 7.1.1: Slump Tolerances If Specified AS Maximum To Be Used Only If One Addition Of Water Is Permitted Plus Tolerance: Minus Tolerance: Specified Slump: If 3 in. If more than Or less 3 in. 0 0 1 1/2” 2 1/2”

Sect. 7.1.2: Slump Tolerances If Not Specified AS Maximum Tolerances For Normal Slumps For Specified Slump of: 2 in. and less More 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. starting either on the arrival at the job site or after the initial 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 Concrete Temperature As Placed Section Size, in. <12 12-36 36-72 >72 Temperature, min F 55 50 45 40 Concrete temperature shall not exceed 90F when using heated materials.

Required Quality Control Testing 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 every 150 yd3 Slump, Air Content, Density, Temperature with each strength test and as necessary for control checks .

Strength Criteria For Concrete Acceptance Sect. 18.1: Cylinders Made and Cured According To 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 Compressive Strength With Standard Deviation Table X1 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 Compressive Strength Without Standard Deviation Table X1.2 Required Average Compressive Strength f’c (psi) f ’c + 1000 f ’c + 1200 1.10f ’c + 700 Specified Compressive Strength, f’c (psi) Less Than 3000 3000 to 5000 Over 5000

QC / QA Concepts Quality Control / Quality Assurance Responsibility to Contractor Performance Based Statistical Controlled Data Comparisons Pay Reductions

Questions? Mississippi Concrete Industries Association Phone: (601) 957-5274 email: rvarner@mississippiconcrete.com website: mississippiconcrete.com