proposed new aashto specification - astm … · determining the reactivity of concrete...

Proposed New AASHTO Specification

M.D.A Thomas, B. Fournier, K.J. Folliard, B R d d G AhlB. Resendez and G. Ahlstrom

ASTM Workshop on Alkali-Silica ReactionJune 6, 2010June 6, 2010

St-Louis, Missouri

FHWA – Protocol for Preventing ASR

Thomas, Fournier & Folliard, 2008Determining The Reactivity of Concrete A d S l i A iAggregates and Selecting Appropriate Measures for Preventing Deleterious Expansion in New Concrete Construction

FHWA HIF 09 001FHWA-HIF-09-001

Document developed under the ASR D l d D l PDevelopment and Deployment Program, consistent with the requirements of SAFETEA-LU legislation.

SAFETEA-LU specifies that “project and programs related to ASR should further result in the development and deployment of techniques to prevent and mitigate alkali silica reactivity, including q p g y, glithium based techniques, and assist states in inventorying existing structures.”

FHWA – Protocol for Preventing ASRComprehensive and progressive specification

Prescriptive & performance alternatives

Alkali-carbonate reactive aggregates must be rejected for use

Allows the use of alkali-silica reactive aggregates with the following gg g gpreventive measures:

• Limiting the alkali content of the concrete• Use of fly ash Use appropriate amount• Use of slag• Use of silica fume• Use of ternary blends

Use appropriate amount of efficient SCM

The actual level of prevention varies with “risk” as defined by:• Reactivity of the aggregate• Nature of the structure (includes. design life)N ( g )• Exposure conditions


Similar documents / approaches

• CSA Standard Practice A23 2-27ACSA Standard Practice A23.2-27A

• RILEM TC-219 ACS - International Specification to minimise damage f lk li ti i tfrom alkali reactions in concrete• 7.1 Alkali-Silica Reaction• 7.2 Specification to combat

damage from alkali reaction in carbonate aggregates

AASHTO Standard Recommended Practice

Scope This practice describes approaches for:• Identifying potentially deleteriously reactive• Identifying potentially deleteriously reactive

aggregates • Selecting appropriate preventive measures to minimize• Selecting appropriate preventive measures to minimize

the risk of expansion when such aggregates are used in concrete• Prescriptive approach• Performance approach

Figure 1Sequence of Laboratory Tests for EvaluatingTests for Evaluating Aggregate Reactivity

AASHTOT 303

Option: ASTM C 1105 (reducedalkali contentalkali content,

1.8 kg/m3)

AASHTO Standard Recommended Practice

Scope This practice describes approaches for:• Identifying potentially deleteriously reactive aggregatesIdentifying potentially deleteriously reactive aggregates

• Selecting appropriate preventive measures to minimize the risk of expansion when suchminimize the risk of expansion when such aggregates are used in concrete• Prescriptive approachPrescriptive approach• Performance approach

FHWA – Protocol for Preventing ASR – Prescriptive Approach

Step 1 – Determine Aggregate Reactivity

Aggregate-Reactivity

Description of aggregate

One-Year Expansion in 14-day Expansion

Table 1: Classification of Aggregate Reactivity

Reactivity Class

aggregate reactivity

Expansion in CPT (%)

y pin AMBT (%)

R0 Non-reactive < 0.040 ≤ 0.10

R1 Moderately reactive 0.040 – 0.120 0.10 > Exp ≤ 0.30

R2 Highly reactive 0.120 – 0.240 0.30 > Exp ≤ 0.45

R3 Very highly reactive > 0.240 > 0.45


Step 2 – Determine Risk of ASR

Table 2: Determining the Level of ASR RiskSize and exposure conditions

Aggregate-Reactivity ClassR0 R1 R2 R3

N i 1 t i

g

Non-massive1 concrete in a dry2 environment Level 1 Level 1 Level 2 Level 3

Massive1 elements in a dry2

environment Level 1 Level 2 Level 3 Level 4

All concrete exposed to humid air, buried or immersed

Level 1 Level 3 Level 4 Level 5

All t d tAll concrete exposed to alkalis in service3 Level 1 Level 4 Level 5 Level 6

1A massive element has a least dimension > 3 ft (0.9 m)2A dry environment corresponds to an average ambient relative humidity lower than 60% normally only found in2A dry environment corresponds to an average ambient relative humidity lower than 60%, normally only found in buildings3Examples of structures exposed to alkalis in service include marine structures exposed to seawater and highway structures exposed to deicing salts (e.g. NaCl) or anti-icing salts (e.g. potassium acetate, sodium formate, etc.)


Step 3 – Determine the Level of Prevention

Table 3: Determining the Level of Prevention

Level of ASR Risk (Table 4)

Classification of Structure (Table 4)

S1 S2 S3 S4

g

S1 S2 S3 S4

Risk Level 1 V V V V

Risk Level 2 V V W X

Risk Level 3 V W X Y

Risk Level 4 W X Y Z

Risk Level 5 X Y Z ZZ

Risk Level 6 Y Z ZZ ††

†† It is not permitted to construct a Class S4 structure (see Table 1) when the risk of ASR is level 6. Measures must be taken to reduce the level of risk in these circumstances.


Step 4 – Classify Structure based on the severity of the consequences should ASR occur


Step 5 – Select Preventive Measure

T bl 5 Li it Alk li C t t f C tTable 5 – Limit Alkali Content of Concrete

Table 6 – Use Supplementary Cementing Material (SCM)

Table 7 – Adjusting Level of SCM Based on Cement Alkalis

Table 8 – Limiting Alkali Content of Concrete and Using g gSCM (to provide exceptional levels of prevention)


Table 5 Maximum Alkali Contents (from Portland Cement) to


Maximum alkali content of concrete (Na2Oe)

( )Provide Various Levels of Prevention

Prevention Levellb/yd3 kg/m3

V No limit

W 5.0 3.0

X 4.0 2.4

Y 3.0 1.8

ZT bl 8Table 8

ZZ



Table 6: Minimum Levels of SCM to Provide Various Levels of Prevention

Type of SCM

Alkali level of

SCM(% Na Oe)

Minimum Replacement Level (% by mass)

Level W Level X Level Y Level Z Level ZZ(% Na2Oe)

Fly ash(CaO ≤ 18%)

< 3.0 15 20 25 35

3 0 4 5 20 25 30 40( )

Table 8

3.0 – 4.5 20 25 30 40

Slag < 1.0 25 35 50 65

1 2 LBA 1 5 LBA 1 8 LBA 2 4 LBASilica Fume†

(SiO2 > 85%) < 1.0

1.2 x LBAor

2.0 x KGA

1.5 x LBAor

2.5 x KGA

1.8 x LBAor

3.0 x KGA

2.4 x LBAor

4.0 x KGA

† The minimum level of silica fume (as a percentage of cementing material) is calculated on the basis of the alkali (Na2Oe) content of the concrete contributed by the portland cement and expressed in either units of lb/yd3 (LBA in Table 6) or kg/m3 (KGA in Table 6).



Using Combinations of SCM’s

When two or more SCM’s are used together to control ASR, the

g

minimum replacement levels given in Table 6 for the individual SCM’s may be reduced provided that the sum of the parts of each SCM is greater than or equal to one

For example: If Table 6 indicates that either 30% fly ash or 50% slag or 10% silica fume is required – it is permissible to use a blend of A% fly q p yash + B% slag + C% silica fume provided:

1CBA 1105030

≥++



Using Combinations of SCM’s

When two or more SCM’s are used together to control ASR, the

g

minimum replacement levels given in Table 6 for the individual SCM’s may be reduced provided that the sum of the parts of each SCM is greater than or equal to one

For example: If Table 6 indicates that either 30% fly ash or 50% slag or 10% silica fume is required – it is permissible to use a blend of A% fly q p yash + B% slag + C% silica fume provided:

1CBA 20% Fly ash + 3.3% Silica Fume1

105030≥++

30% Slag + 4% Silica Fume



Table 7: Adjusting Minimum SCM Level Based on Cement Alkalis

Cement Alkalis(% Na2Oe)

Level of SCM

Table 7: Adjusting Minimum SCM Level Based on Cement Alkalis

( 2 )

< 0.70 Reduce the minimum amount of SCM given in Table 6 by one prevention level

0.70 to 1.00 Use minimum SCM levels in Table 6

I th i i t f SCM> 1.00 Increase the minimum amount of SCM given in Table 6 by one prevention level

> 1 25 N id i i> 1.25 No guidance is given


Cement Alkalis(% Na2Oe)

Level of SCM

< 0.70Reduce the minimum amount of

SCM given in Table 6 by one prevention level

0.70 to 1.00 Use minimum SCM levels in Table 6

> 1.00Increase the minimum amount of

SCM given in Table 6 by one prevention level

Table 6: Minimum Levels of SCM to Provide Various Levels of Prevention

> 1.25 No guidance is given

Type of SCM

Alkali level of

SCM(% Na2Oe)

Minimum Replacement Level (% by mass)

Level W Level X Level Y Level Z Level ZZ

Fly ash(CaO ≤ 18%)

< 3.0 15 20 25 35

3.0 – 4.5 20 25 30 40

Table 8 Slag < 1.0 25 35 50 65

1.2 x LBA 1.5 x LBA 1.8 x LBA 2.4 x LBASilica Fume†

(SiO2 > 85%) < 1.0 or2.0 x KGA

or2.5 x KGA

or3.0 x KGA

or4.0 x KGA



Table 8: Using SCM and Limiting the Alkali Content of the Concrete to

SCM as sole Limiting concrete alkali content plus SCM

Table 8: Using SCM and Limiting the Alkali Content of the Concrete to Provide Exceptional Levels of Prevention

Prevention Level

prevention Limiting concrete alkali content plus SCM

Minimum SCM level

Maximum alkali content, lb/yd3

(kg/m3)

Minimum SCM level(kg/m3)

ZSCM level shown

for Level Z in Table 6

3.0 (1.8) SCM level shown for Level Y in Table 6

ZZ Not permitted 3.0 (1.8) SCM level shown for Level Z in Table 6






Prevention Level


Minimum SCM level


(kg/m3)


ZSCM level shown for Level Z in

Table 63.0 (1.8) SCM level shown for

Level Y in Table 6Table 6

ZZ Not permitted 3.0 (1.8) SCM level shown for Level Z in Table 6


Alkali Minimum Replacement Level (% by mass)

Selecting Preventive level Z

Type of SCM level of SCM

(% Na2Oe) Level W Level X Level Y Level Z Level ZZ

25 35Fly ash(CaO ≤ 18%)

< 3.0 15 20 25 353.0 – 4.5 20 25 30 40

SCM Slag < 1.0 25 35 50 65

Prevention LevelMaximum alkali content of concrete (Na2Oe)

lb/yd3 kg/m3

only

SCM + alkali

control

y g

V No limit

W 5.0 3.0

X 4.0 2.4control

Y 3.0 1.8

ZTable 8

ZZ






Prevention Level


Minimum SCM level


(kg/m3)


ZSCM level shown

for Level Z in Table 6

3.0 (1.8) SCM level shown for Level Y in Table 6

ZZ Not permitted 3.0 (1.8)

SCM level shown for Level Z in Table 6


Alkali Minimum Replacement Level (% by mass)

Selecting Preventive level ZZ

Type of SCM level of SCM

(% Na2Oe) Level W Level X Level Y Level Z Level ZZ

35 N !Fly ash(CaO ≤ 18%)

< 3.0 15 20 25 353.0 – 4.5 20 25 30 40

SCM

No !

Slag < 1.0 25 35 50 65

Prevention LevelMaximum alkali content of concrete (Na2Oe)

lb/yd3 kg/m3

only

SCM + alkali

control

y g

V No limit

W 5.0 3.0

X 4.0 2.4control

Y 3.0 1.8

ZTable 8

ZZ

FHWA – Protocol for Preventing ASR – Performance Approach

Performance Testing using the Concrete Prism Test (CPT)

1 Total cementitious content = 708 lb/yd3 (420 kg/m3) portland cement

Evaluating SCMs using the CPT

1. Total cementitious content = 708 lb/yd3 (420 kg/m3) – portland cement partially replaced with various levels of SCM (or combination of SCM’s)

2. Alkali content of portland cement component raised to 1.25% Na2Oe

3. W/CM = 0.42 to 0.45 Use high-range WRA if slump too lowUse VMA if high sl mp ca ses segregationUse VMA if high slump causes segregation

4. Expansion ≤ 0.04% at 2 years.


Performance Testing using the CPT

Evaluating Lithium Admixtures using the CPTEvaluating Lithium Admixtures using the CPT

1. Total cementitious content = 708 lb/yd3 (420 kg/m3) – with or without SCM’SCM’s

2. Alkali content of portland cement component raised to 1.25% Na2Oe

3 LiNO solution added to mix water at various levels3. LiNO3 solution added to mix water at various levels

4. W/CM = 0.42 to 0.45 (include water in LiNO3 solution) Use high-range WRA if slump too lowg g pUse VMA if high slump causes segregation

5. Expansion ≤ 0.04% at 2 years.


Th t i t t t b d t d t i th i fl f

Performance Testing using the CPT

The concrete prism test cannot be used to determine the influence of portland cement alkalis on ASR expansion, in other words:

• Portland cement alkalis must be raised to 1 25% Na Oe in the CPT• Portland cement alkalis must be raised to 1.25% Na2Oe in the CPT to compensate for leaching during test

• CPT cannot be used to determine the safe alkali level for a ti l tparticular aggregate

• CPT cannot be used to evaluate a combination of low-alkali cement and SCM


Performance Testing using the AMBT

First establish correlation between AMBT & CPT for aggregate1.0

%)

.

If AMBT vs CPT data fall ithi thi th

0.6

0.8

n A

MB

T (% within this range the

AMBT may be used to evaluate preventive measures

0.4

0.6

pans

ion

in

0.0

0.2

14-d

Ex

0 0.2 0.4 0.6

1-Y Expansion in CPT (%)


Performance Testing using the AMBT

Evaluating SCM’s using the AMBT

1. Use ASTM C 1567 except that the portland cement alkalis should be 0.90 ± 0.10% Na2Oe

2. Do not use this test if fly ash alkalis > 4.5% Na2Oe or alkali content of other SCM’s > 1.0% Na2Oe2

3. Expansion < 0.10% at 14 days


Performance Testing using the AMBTi• The accelerated mortar bar test cannot be used to determine the

influence of portland cement alkalis on ASR expansion, in other words:• AMBT cannot be used to determine the safe alkali level for a

particular aggregate• AMBT cannot be used to evaluate a combination of low-alkali

cement and SCM


Performance Testing using the AMBT LiNO3

Begin by Testing the Aggregate with the following two mixtures:1. Control mixture (Expansion at 28 days = E1) 2. Mixture with lithium: [Li]/[Na+K] = 0.74 in bar and [Li]/[Na]=0.148 in

soak solution (Expansion at 28 days = E2)

soak solution (Expansion at 28 days E2)

Is the ((E2-E1)/E1) < 0.1

Yes No

Use concrete prisms test to evaluate the ratio to use

Use the following equation: 1.0 + 0.7 x ((E2-E1)/E1) = Ratio The Ratio = [Li]/[Na+K] to use in

evaluate the ratio to useThe Ratio [Li]/[Na+K] to use in concrete

Tremblay et al. 2008

Modified C 1260 (Protocol A - FHWA)

1.1

1.2NS1

0.9

1

1.1co

ncre

te

yea

rs

00 + 0.7X

ON1

QC

0 7

0.8

0.9

/[Na+

K] i

n e

CPT

at 2

Y = 1.00

NM USE CPT

0 5

0.6

0.7

imum

[Li]/

to p

ass

the

ON2

TX

0 3

0.4

0.5

Min

i t

ULavalCanmetUTexas

-0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5(E2-E1)/E1

0.3


Other information provided

• Example of calculation of lithium nitrate addition in the CPT

• Example of calculation of lithium nitrate Performance approach

addition in the modified AMBT• Worked examples for selecting preventive

measures for ASR : prescriptive approachmeasures for ASR : prescriptive approach

AASHTO Specification – Next steps

• Specification balloted in 2009 and was approved• Attracted some negative votes but nothing that cannot be resolvedg g• States indicated that they will use the document as a baseline to

develop documents that will meet their own needs (education)

• The new Recommended Practice will be included in the 2010 printing of AASHTO Specifications and Standards

A i i• A commentary will be reviewed by the Task Force and presented at the August 2010 AASHTO SQM meeting

• Two articles will be published to present the specification• Two articles will be published to present the specification• Reactive solutions• Bridge Views (FHWA + Industry)

Thank You

Any Questions ?

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