T20- TS Mix Designs and Specs- CONAGG 2014 · • ACI 301 Specifications for Structural Concrete ...

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TT--2020Troubleshooting Concrete Troubleshooting Concrete

Mix Designs and SpecificationsMix Designs and Specifications

1 1www.conexpoconagg.com

Michelle L. Wilson, FACIDirector, Education

Portland Cement Associationwww.cement.org

Tuesday, March 4, 2014

Disclaimer and Waiver of Liability

This document is for informational purposes only and is not to be construed asexplicit engineering advice, or professional engineering services. This serviceis provided on the terms and understanding that the author(s) or companiesrepresented by the CONEXPO-CON/AGG 2014 or author(s) makes no warranty,guarantee, or promise, express or implied, concerning the content or accuracyof the material herein and accessible via this service.

No person or business entity should rely on the sole contents of this documentto make any decisions The CONEXPO-CON/AGG 2014 or author(s) or the


to make any decisions. The CONEXPO-CON/AGG 2014 or author(s) or thecompanies that they represent are not responsible for the results of any actionstaken on the basis of information in this service, nor for the actions of personsusing this document, nor for any error in or omission contained in thisdocument.

The CONEXPO-CON/AGG 2014 or author(s) or any represented companyexpressly disclaims all and any liability and responsibility to any person inrespect of anything, and of the consequences of anything, done or omitted tobe done by any such person in reliance, whether wholly or partially, upon thewhole or any part of the contents of this document.

Learning Objectives

1. Describe the general purpose of ASTM C94, Standard Specification for Ready Mixed Concrete and how it is applied in Concrete Specifications.

2. Introduce ACI 301-10, Specifications for Structural Concrete and how it is applied into contract


documents.

3. Define common confusion in current specifications and note how we can troubleshoot existing specifications to ensure concrete meets final performance criteria.

Portland Cement Association

• Founded in 1916

• Headquarters: Washington D.C.

• Labs: Skokie, Illinois


• Mission:

To improve and extend the uses of portland cement and concrete.

Why do concrete problems occur?


Avoiding Problems

• Design- Constructability

• Mix Design

• Materials Selection

DesignDesign


• Placement Procedures

• Environment

WorkmanshipWorkmanship

GOAL

EnvironmentEnvironment

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Concrete Mixtures


• Determine the most economical and practical combination

• Use readily available materials

Goals for Designing Concrete Mixtures


• Produce a concrete that satisfies the performance requirements under particular conditions of use.

Fresh Concrete Properties

• Consistency

• Workability

• Uniformity


• Bleeding

• Setting & Hardening

Hardened Concrete Properties

• Hydration rate and setting time

• Strength and durability

Permeabilit and


• Permeability and water tightness

• Volume Stability and Crack Control

• Aesthetics

Need for Innovation


Concrete Codes and Specifications

• ACI 318 Building Code Requirements for Structural Concrete

• ACI 301 Specifications for Structural Concrete


• ACI 301 Specifications for Structural Concrete

• ASTM C94 Standard Specification for Ready-Mixed Concrete

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Confusion in Current Concrete Specifications

• Prescription vs. Performance

• w/cm vs. Strength

• Min. Cement Content

• Cement Type


• Slump vs. Quality

• Temp. Limit vs. Thermal Control

• Durability Requirements

• Curing Regime

• Acceptance Criteria

Concrete Mix Design

Summary of Absolute Volume Method ACI 211.1

1. Strength Requirements

2. Determining W/CM

7. Cement Content

8. Cement Type


6. Water Content

3. Coarse Aggregates

4. Air Content

5. Workability

12. Trial Mixes

9. Admixture Effects

10. Sand Requirements

11. Moisture Corrections

Basis for Proportioning

ASTM C94 Sec 6

• Option A - Performance

• Option B - Prescriptive


• Option C - Combined

Make Concrete Good…


Performance Based Specifications

• Strength

• Air Void Spacing/ Durability Factor

• Permeability/


• Permeability/ Coulombs

• Shrinkage Tolerance

• Material Acceptability-ASR, Sulfate Testing

w/cm vs. Strength

-0.337000

Air-EntrainedNon-Air Entrained

W/CMRequired design

strength

fcr’ (psi)

ACI 211.1


0.337000

0.740.822000

0.590.683000

0.480.574000

0.400.485000

0.320.416000

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The Water-Cement Ratio Law

For given materials the strength of the concrete (so long as we have a plastic mix) depends solely on the relative quantity of water as compared with the cement, regardless of mix or size and grading of aggregate.

Duff A. Abrams


May, 1918

Optimum Water-CementitiousMaterials Ratio


From Hover 2003

Minimum Cementitious Content

• General recommendations (PCA/ACI):For workability, finishability, and durability in flatwork follow recommendations in table:

Max. Aggregate, mm (in)

Min Cement,

kg/m3 (lb/yd3)


37.5 (1½) 280 (470)

25 (1) 310 (520)

20 (¾) 320 (540)

12.5 (½) 350 (590)

10 (3/8) 360 (610)



Types of Cement

ASTM C150 (AASHTO M 85)

ASTM C595 (AASHTO M 240)

ASTM C1157


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Workability Requirements

ACI 211.1:Concrete construction Slump, mm (in.)

Maximum Minimum

Reinforced foundation walls and footings

75 (3) 25 (1)


Plain footings, caissons, and substructure walls

75 (3) 25 (1)

Beams and reinforced walls 100 (4) 25 (1)

Building columns 100 (4) 25 (1)

Pavements and slabs 75 (3) 25 (1)

Mass concrete 75 (3) 25 (1)

Slump vs. Concrete Quality

Slump should be based on placement conditions not as an indication of concrete quality.



On-site Water Addition?

• ASTM C94 Sec. 12.7 states,Water is allowed to be added on site if:

– Slump is less than desired

– Max water content is not exceeded

– Water add takes no more than


– Water add. takes no more than 15 min (can be multiple additions of water)

– Provided that no concrete has been discharged except for slump or slump flow testing

– 30 drum revolutions are added

Temperature Limit vs. Thermal Control


Thermal Control


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Durability Considerations

• Abrasion

• Reactive Aggregates

– ASR

• Freeze/Thaw


• Chemical Attack

– Sulfates

• Seawater Exposure

• Corrosion

Resistance to Abrasion

• Aggregate type

• Strength

• Finishing

• Curing


g

• Testing (ASTM C779 and C944)

Resistance to Alkali Silica Reactivity

• Pozzolans, Slag, and Blended Cement

• Low Alkali Portland Cement


• Limit Concrete Alkalies• Lithium• Aggregate Selection

and Beneficiation

Resistance to Alkali-Silica Reactivity

ASR

• Prism Test- ASTM C1293 < 0.04% expansion (1 year)

• Mortar Bar Test- ASTM C1260 < 0.10% expansion (14 days)

• Use of SCMs ASTM C1567 < 0.10% expansion (14 days)


Caution: Limiting the alkali level of cement (<0.6%) may not be enough to mitigate ASR- focus must be on TOTAL alkalies in concrete.

ACI 318 Exposure Conditions


ACI 318 Exposure ConditionsACI 318 Exposure Conditions


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Resistance to Freeze-Thaw

Criteria :

• Sufficient strength is attained

prior to first freezing

( 3 5 MP 500 i)

• The aggregate is frost-resistant


• Sufficient strength is attained

prior to cyclic freezing &

thawing (> 31 MPa or 4500 psi)

•• Adequate Air Void System

(> 3.5 MPa or 500 psi)

Total Air Content- ACI 318


ACI 318 Strength ACI 318 Strength & w/cm & w/cm Requirements Requirements for Freezefor Freeze--Thaw Resistance Thaw Resistance


ACI 318 Limits on Supplementary Cementing Materials for Resistance to Deicer Scaling

40 40www.conexpoconagg.comACI 318

Resistance to Sulfates

• Low w/cm

• Type of Cement (lower aluminate)

• Use of Pozzolans, Slag, and Blended Cement


• Expansion Tests (ASTM C1012)

Moderate- Class 1

< 0.10% at 6 months

Severe- Class 2

< 0.05% at 6 months

< 0.10% at 12 months

Very Severe- Class 3

< 0.10% at 18 months

ACI 318 Strength and w/cm Requirements for Sulfate Resistance


1See ACI 318 for definition of exposure classes

* Note- PCA Requirements include a w/cm < 0.40, and a minimum compressive strength of 35Mpa (5000psi) for Very Severe (S3) Sulfate Exposure

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Resistance to Corrosion

• Low w/cm

• 7 days Moist Cure

• Use of SCM’s

• Proper Cover Depth

E C t d R i f t


• Epoxy Coated Reinforcement

• Sacrificial Anode

• Cathodic Protection

• Surface Treatments

ACI 318 Strength ACI 318 Strength and w/cm Requirements and w/cm Requirements and Chloride and Chloride Limits for Corrosion ResistanceLimits for Corrosion Resistance


•Maximum water-soluble chloride ion expressed as a mass percentage of the cementitious material content

Low-Permeability Concrete -Corrosion Resistance

• Permeability- ASTM C1202

• Less than 2000 Coulombs

• Effect of test age?


Cracking vs. Durability


Volume Stability- Low Shrinkage Concrete

• Minimize water content

• Aggregate selection

– Top size, expansion

Testing (ASTM C157)


• Testing (ASTM C157)

Curing Regime

When not otherwise specified (ACI 301):

•Concrete shall be maintained above 50° F and in a moist condition for at least the first 7


condition for at least the first 7 days after placement.

•High-early strength concrete shall be maintained above 50° F and in a moist condition for at least the first 3 days.

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QA/QC

• Preconstruction meeting (proactive)

• Prequalification of finishing crew (proactive)


g (p )

• Test panels, Mock ups

Acceptance Criteria

General Acceptance criteria

-Architecturally acceptable concrete surfaces should be aesthetically compatible with minimal color and texture variations and minimal surface


color and texture variations and minimal surface defects when viewed at a distance of approximately 20 ft (6m) or more as agreed upon by architect, owner, and contractor, or as otherwise specified.

Acceptance Criteria (on-site)

• Temperature (ASTM C1064)

• Air content (ASTM C231 and C173)

• Workability (ASTM C143)

FRESHFRESH


• Strength (ASTM C31 and C39)

HARDENEDHARDENED

Acceptance Criteria (Fresh Concrete)

• ASTM C94, Sec 17.6.1 states,

If the measured slump or air content, or both is greater than the specified upper limit, a check test shall be made immediately on a new test sample. In the event the check test fails the concrete shall be considered to have


check test fails, the concrete shall be considered to have failed the requirements of the specification.

Acceptance Criteria (Fresh Concrete)


If the measured slump or air content, or both is less than the lower limit, permit adjustments… and obtain a new sample. If the sample of the adjusted concrete fails, a check test shall be made immediately on a new


a s, a c ec test s a be ade ed ate y o a esample of the adjusted concrete.

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Acceptance Criteria (Hardened Concrete)

• ASTM C94, Sec 18.1 states,

When strength is used as a basis for acceptance of concrete, standard specimens shall be made in accordance to Practice C31/C31M.




Immediately after molding and finishing, the specimens shall be stored for a period up to 48h in a temperature range from 60 and 80°F


[16 and 27 °C] and in an environment preventing moisture loss from the specimens.

57 57www.conexpoconagg.com 58 58www.conexpoconagg.com


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• ACI 301-05 1.6.2.2.d – Provide space, source of power and facilities to be

used on the project for initial curing of concrete test specimens as required by ASTM C31/C31M for the sole use of the Owner’s quality assurance


testing agency

• ACI 301-10 1.6.2.2.d– Provide space and source of electrical power on

the project site for initial curing of concrete test specimens as required by ASTM C31/C31M for the sole use of the Owner’s quality assurance testing agency.

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Responsibility-Owner and Testing Agency

ACI 311.6-09 2.5—Curing of strength test specimens• 2.5.1 Initial curing—Owner or Owner’s representative will provide and

maintain adequate facilities on the project site for initial storage and curing of the concrete specimens, unless otherwise specified. Specimens shall be stored under conditions that meet the requirements of ASTM C31 and shall be verified by Testing Agency. Such storage shall have temperature controls to maintain ASTM C31 temperature


shall have temperature controls to maintain ASTM C31 temperature requirements. Calibrated temperature recording devices shall be used to record daily maximum and minimum temperatures of the initial curing environment.


Responsibility-Owner and Testing Agency

ACI 311.6-09 2.5—Curing of strength test specimens

• 2.5.2 Transportation—Testing Agency will recover and transport concrete specimens in accordance with ASTM C31.


• 2.5.3 Final curing—Final curing of strength test specimens shall be done in accordance with ASTM C31 and C511 until time of test.

Be Clear on Desired Outcome

• Specify enough and the right “hoops” to jump through to get the performance you require for service conditions.


State the Obvious

• If it isn’t in the Specification, it probably won’t happen.

Ex:


– Curing Regime

– Thermal Control

Caution Requirements that Bind Contractors Hands

• Means and Methods

• Materials Types, Limits


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Default vs. Optional Requirements

• There is more than one way to get the job done.


Questions and Further Information

Michelle L. Wilson, FACIMichelle L. Wilson, FACI

Director, EducationPortland Cement Association

www cement org


www.cement.org

847.972.9034 phone

[email protected]

www.cement.org


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