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Publication Number: FHWA-RD-01-164
Date: March 2002

Appendix C: Laboratory Data Collection Forms, Flowcharts, and Diagnostic Tables

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C.1 LABORATORY DATA COLLECTION FORMS

To provide a uniform basis for approaching concrete analysis, the following data sheets are provided. The data sheets are organized into eight major groupings with a variable number of forms provided within each group. Analysts are expected to enter data and observations on these forms. A copy of these forms accompanies each core, following it through the analysis process. Additionally, a copy of the completed forms should be provided to the engineer along with the final laboratory report. The groupings and individual forms as presented in Guideline II are as follows:

Group 1: Core Receipt and Cataloging

Group 2: Visual Inspection

Group 3: Stereo Optical Microscope Examination

Group 4: Staining Tests

Group 5: Petrographic Optical Microscope Examination

Group 6: Scanning Electron Microscope Examination

Group 7: Chemical Tests

Group 8: X-ray Diffraction Analysis

LABORATORY LOG OF PCC PAVEMENT CORES

Sheet ____ of ____

Project Designation: State: Highway:
Nearby City and Distance: Direction:
No. of Through Lanes (in direction sampled): Lane Sampled:
Beginning Milepost/Station: End Milepost/Station:
Operator: Core Diameter:
Coring Date: Core Barrel Tip Type:
Job ID:

Note: Each column shown below should be used to record information for all cores/pieces extracted from a single panel. “Depth” should be measured from the pavement surface to the bottom of the core/piece and recorded to the nearest 2 mm. Front direction is the direction of traffic.

CORE NUMBER

A

B

C

D

E

Other

CORE ID

           

LOCATION/STATION

           

Offset From Joint

           

Offset From Shoulder

           

Number of Pieces?

           

Core Piece No. 1

           

Position
(Left, Right, Back, Front of core)

           

Depth (mm)

           

Core Piece No. 2

           

Position
(Left, Right, Back, Front of core)

           

Depth (mm)

           

Core Piece No. 3

           

Position
(Left, Right, Back, Front of core)

           

Depth (mm)

           

Core Piece No. 4

           

Position
(Left, Right, Back, Front of core)

           

Depth (mm)

           

Remarks

           


Analyst

Core taken by

Date Cored

Date

Core ID

Job ID

CORE SAMPLED FOR LABORATORY ANALYSIS

Location (circle one): A B C D E Other?:

Picture: Top View

Core Diameter: mm

No. of Pieces:

Ht. Piece #1: mm

Wt. Piece #1: kg

Ht. Piece #2: mm

Wt. Piece #2: kg

Ht. Piece #3: mm

Wt. Piece #3: kg

Ht. Piece #4: mm

Wt. Piece #4: kg

Total Ht.: mm

Total Wt.: kg

Sketch
Picture: Side View

 

Analyst

Job ID

Date

Core ID

Visual Inspection - General Condition of Concrete
Attach additional documentation and photographs as needed.

Diagnostic Feature

Options

Comments

Ring when struck lightly with a hammer?

Yes

No

 

Does it break with your fingers?

Yes

No

 

Is the concrete well consolidated?

Yes

No

 

Is segregation apparent?

Yes

No

 

Orientation/parallelism of aggregates?

Yes

No

 

Visible surface deposits or exudate?

Yes

No

 

Are cracks apparent in the paste?

Yes

No

 

Are the cracks widespread?

Yes

No

 

Cracks through aggregates?

Yes

No

 

Are there cracks around aggregates?

Yes

No

 

Deposits in cracks?

Yes

No

 

Embedded items present?

Yes

No

 

Adequate cover over the embedded items?

Yes

No

 

Are embedded items corroded?

Yes

No

 

Underside voids on elongated aggregates?

Yes

No

 

Are air voids filled?

Yes

No

 

Does paste hardness seem normal?

Yes

No

 

Is paste hardness uniform throughout?

Yes

No

 

High paste content?

Yes

No

 

Gradation of aggregates?

gap

uniform

 

Coarse aggregate top size?

   

Coarse aggregate type?

crushed

natural

 

Coarse aggregate rock type?

   

Fine aggregate type?

crushed

natural

 

Fine aggregate rock type?

   

Alteration/reaction with aggregates?

Yes

No

 

Comments_______________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________


Analyst

Job ID

Date

Sample ID

Stereo OM - Observations of the Concrete
Attach additional documentation and micrographs as needed.

Diagnostic Feature

Options

Comments

Bleeding?

bleed channels
pockets under aggregates

 

Fractures?

none through aggregates
in paste around aggregates

 

Air void infilling?

yes partial no

 

Air void shape

spherical irregular
ellipsoidal

 

Embedded item condition?

good corroded

 

Surface condition?

cracked carbonated
weathered leached
normal

 

Aggregate reaction products?

yes no

 

Location of reaction products?

air voids
cracks through aggregates
cracks around aggregates cracks in paste

 

Gaps around coarse or fine aggregates?

description
estimate occurrence

 

Gap widths larger for larger particles?

yes no

 

Are the gaps filled?

yes no

 

Coarse aggregate type?

gravel quarried
crushed gravel slag
other

 

Lithological types of coarse aggregate?

specify types identified

 

Orientation/parallelism of coarse aggregate?

specify which and specify
direction of orientation

 

Fine aggregate type?

natural other (specify)
crushed

 

Lithological types of fine aggregate?

specify types identified

 

Paste color – note uniformity of color.

white light gray
dark gray yellow
green other (specify)

 

Paste hardness – note uniformity of hardness.

soft hard
medium

 

Comments ______________________________________________________________

_______________________________________________________________________


Analyst

Job ID

Date

Sample ID

Stereo OM Observations - Alterations of the Aggregates

Attach additional documentation and micrographs as needed.

Coarse Aggregates

Diagnostic Feature

Options

Comments

Degree of alteration?

isolated extensive

moderate

 

Cracking in aggregates?

yes no

 

Internal cracks narrow from center of aggregate out?

yes no

 

Cracks through aggregates extend into the paste?

yes no

 

Dissolution or softening

of aggregates?

yes no

 

Reaction rims?

yes no

 

Reaction products

from alteration?

yes no

 

Location of reaction products?

air voids
cracks through aggregates
cracks around aggregates cracks in paste
pockets adjacent to aggregates

 

Fine Aggregates

Diagnostic Feature

Options

Comments

Degree of alteration?

isolated extensive
moderate

 

Cracking in aggregates?

yes no

 

Internal cracks narrow from center of aggregate out?

yes no

 

Cracks through aggregates extend into the paste?

yes no

 

Dissolution or softening

of aggregates?

yes no

 

Reaction rims?

yes no

 

Reaction products

from alteration?

yes no

 

Location of reaction products?

air voids
cracks through aggregates
cracks around aggregates cracks in paste
pockets adjacent to aggregates

 

Narrative Description of Alteration _______________________________________________

_______________________________________________________________________


Analyst

Job ID

Date

Sample ID

Results of ASTM C 457

Method Used:

Length Traversed

Area Traversed

Magnification

No. of Stops

Air-Void System Parameters

Specification

Typical Range for Acceptable Air Entrained Concrete

Calculated Value for Original Air-Void System (infilling counted as air)

Calculated Value for Filled Air-Void System (infilling counted as paste)

Spacing Factor (symbol )

0.01 - 0.02 mm

   

Specific Surface (a)

23.6 - 43.3 mm-1

   

Paste/Air Ratio

4 - 10

   

Void Frequency (n)

     

Phase Abundance Analysis

Phase

Volume Percent

Coarse Aggregate

Fine Aggregate

Paste

Original Air Content

Filled Voids

Comments______________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

 

Analyst

Job ID

Date

 

Sulfate/ASR Reaction Product Staining

Attach additional documentation and micrographs as needed.

Core ID

Method Used

Positive Staining

Comments

   

Yes No

 
   

Yes No

 
   

Yes No

 
   

Yes No

 

Depth of Carbonation

Attach additional documentation and micrographs as needed.

Core ID

Depth of Carbonation

Comments

     
     
     
     

Comments_______________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________


Analyst

Job ID

Date

Sample ID

Petrographic OM - Observations of the Concrete

Attach additional documentation and micrographs as needed.

Diagnostic Feature

Selected Descriptors

Comments

w/c in bulk?

specify method and value

 

w/c at surface if different than bulk?

specify method and value

 

Evidence of trapped bleed water?

water voids below horizontal aggregate faces

 

Air-void structure at surface intact?

specify

 

Calcium hydroxide depletion?

specify

 

Sub parallel cracking or delamination at surface?

specify

 

Paste density variations around the aggregates?

specify

 

Cracking?

cracks through aggregates
cracks around aggregates cracks in paste

 

Secondary deposits?

yes no

 

Location of secondary deposits?

air voids
cracks through aggregates
cracks around aggregates cracks in paste

 

Identify deposits.

specify

 

Lithological details of coarse aggregate?

specify

 

Lithological details of fine aggregate?

specify

 

Mineral admixtures?

present not present

 

Identification

fly ash silica fume
GGBF slag other

 

 

Narrative Description of Petrography Results: ________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________


Analyst

Job ID

Date

Sample ID

Petrographic OM Observations - Alterations of the Aggregates
Attach additional documentation and micrographs as needed.

Coarse Aggregates

Diagnostic Feature

Selected Descriptors

Comments

Degree of alteration?

isolated extensive
moderate

 

Cracking in aggregates?

yes no

 

Internal cracks narrow from center of aggregate out?

yes no

 

Cracks through aggregates extend into the paste?

yes no

 

Dissolution of aggregate?

yes no

 

Reaction rims?

yes no

 

Reaction products?

yes no

 

Location of reaction products?

air voids
cracks through aggregates
cracks around aggregates cracks in paste
pockets adjacent to aggregates

 

Identify reaction products

specify

 

Fine Aggregates

Diagnostic Feature

Selected Descriptors

Comments

Degree of alteration?

isolated extensive
moderate

 

Cracking in aggregates?

yes no

 

Internal cracks narrow from center of aggregate out?

yes no

 

Cracks through aggregates extend into the paste?

yes no

 

Dissolution of aggregate?

yes no

 

Reaction rims?

yes no

 

Reaction products?

yes no

 

Location of reaction products?

air voids
cracks through aggregates
cracks around aggregates cracks in paste
pockets adjacent to aggregates

 

Identify reaction products

specify

 

Narrative Description of Alteration _______________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________


Analyst

Job ID

Date

 

SEM - General Conditions

SEM or CSEM

Operating Pressure

Samples Conductive Coated (Y/N)

Coating Method/Thickness

Samples Dehydrated (Y/N)

Dehydration Method

SEM - Conditions for Quantitative Microanalysis

SEM or CSEM

Operating Pressure

Accelerating Voltage

Beam Current

Working Distance

Standardless or full-quantitative (with standards) analysis?

Oxygen measured or determined by stoichiometry?

Analysis done by EDS or WDS?

SEM - Conditions for X-ray Mapping

SEM or CSEM

Operating Pressure

Accelerating Voltage

Beam Current

Working Distance

Map Resolution

Map Dwell Time

Elements Mapped

Comments ______________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________


Analyst

Job ID

Date

Sample ID

Summary of Scanning Electron Microscope Analysis


Analyst

Job ID

Date

 
Summary of Chemical Tests

Determination of w/c

Specimen ID

Method Used

Measured w/c

Comments

       
       
       
       
       
       
       
       

Determination of Sulfate Concentration

Specimen ID

Method Used

Sulfate Concentration

Comments

       
       
       
       
       
       
       
       

Determination of Chloride Concentration

Specimen ID

Method Used

Chloride Concentration

Comments

       
       
       
       
       
       
       
       


Analyst

Job ID

Date

 

XRD - Analytical Conditions

Type of specimen (e.g., powder, slab)

Specimen mounting method? (Side drifted, pressed pellet)

X-ray tube kV and mA

X-ray tube target material

Was a primary beam filter used and what type?

Monochromater used? (Y/N)

Divergence slit (specify mm or degrees)

Receiving slit (specify mm or degrees)

Scan range (degrees 2q)

Scan rate (degrees/min)

Dwell time (seconds/step)

Step size (degrees/step)

Peaks identified by automatic or manual search (auto or manual)?

Background subtracted before analysis?


XRD - Results of Qualitative Analysis


C.2 FLOWCharts AND Diagnostic TABLES

This section contains copies of the flowcharts and diagnostic tables for reproduction. The flowcharts present a systematic method for diagnosing MRD in concrete pavements. The analyst inspects the concrete using the methods described in Guideline II, being guided by the hierarchy of questions presented in the flowcharts presented in figures C-1 through C-4 in this appendix (figures II-15 through II-17 in guideline). The responses to the questions presented in the flowcharts determine what analytical procedures will be performed. As the analyst moves through the flowcharts, there is the potential for more than one MRD being identified. The analyst needs to keep track of all possibilities identified and then use the diagnostic tables presented in tables C-1 through C-7 in this appendix (tables II-1 through II-7 in guideline) to help isolate the most likely MRD(s). The tables summarize the common diagnostic features associated with each MRD.

Possible Distress

Present

Additional Information

  Error in mix proportioning

Yes

No

See recommended literature

Poor placement

Yes

No

See recommended literature

Poor finishing/curing

Yes

No

See recommended literature

Poor steel placement

Yes

No

See recommended literature

Carbonation at depths > 5-10 mm

Yes

No

See recommended literature

 

Go to Alternative Text link to this image or the text link below
Alternative Text for Figure C-1

Figure C-1. Flowchart for assessing general concrete properties based on visual examination.

Possible Distress

Present

Additional Information

Shrinkage cracks or sample preparation cracks

Yes

No

See recommended literature

Corrosion of embedded steel

Yes

No

Table C-1

Paste freeze-thaw

Yes

No

Table C-2

Aggregate freeze-thaw

Yes

No

Table C-3

Sulfate attack

Yes

No

Table C-4

Deicer attack

Yes

No

Table C-5

Infilling material

Yes

No

Figure C-3

Go to Alternative Text link to this image or the text link below
Alternative Text for Figure C-2

Figure C-2. Flowchart for assessing the condition of the concrete paste and air.

Possible Distress

Present

Additional Information

Corrosion of embedded steel

Yes

No

Table C-1

Sulfate attack

Yes

No

Table C-4

Deicer attack

Yes

No

Table C-5

Alkali–silica reaction

Yes

No

Table C-6

Alkali–carbonate reaction

Yes

No

Table C-7

 

Go to Alternative Text link to this image or the text link below

Alternative Text for Figure C-3

Figure C-3. Flowchart for identifying infilling materials in cracks and voids.

Possible Distress

Present

Additional Information

Natural cracking of aggregate

Yes

No

See recommended literature

Sample preparation cracks

Yes

No

See recommendedlLiterature

Aggregate freeze-thaw

Yes

No

Table C-3

Natural weathering of aggregates

Yes

No

See recommended literature

Alkali–silica reaction

Yes

No

Table C-6

Alkali–carbonate reaction

Yes

No

Table C-7

Infilling material

Yes

No

Figure C-3

 


Alternative Text for Figure C-4

Figure C-4. Flowchart for assessing the condition of the concrete aggregates.

Go to Alternative Text link to this image or the text link below

Table C-1. Diagnostic features of corrosion of embedded steel.

Diagnostic Feature

Method of Characterization

Comments

Spalling and delamination of concrete over reinforcing steel

Field Evaluation
Visual Inspection

Visual inspections can be used to readily identify areas affected by corrosion of embedded steel. It is characterized by rusting steel at the bottom of the spalled out area and rust stains on the loose pieces.

Visible corrosion products

Field Evaluation
Visual Inspection
Stereo OM
Petrographic OM

The “rust” seen may contain crystalline magnetite but is primarily amorphous.


Table C-2. Diagnostic features of paste freeze-thaw damage.

Diagnostic Feature

Method of Characterization

Comments

Surface scaling or subparallel cracking

Field evaluation
Visual

Look for loss of paste at road surface, exposed coarse aggregate, and/or scaling. Can be isolated to surface or through slab depth.

Stereo OM
Petrographic OM

Look for delamination/ subparallel cracking at surface or evidence of an overworked surface such as decreased air content at the surface.

Inadequate air- void system

Stereo OM

Measure air-void parameters consistent with ASTM Method C 457. Typical parameters for good concrete are as follows:

Spacing Factor (symbol) = 0.1 - 0.2 mm
Maximum Spacing (symbol ) = 0.2 mm
Typical Specific Surface (a) = 23.6 - 43.3 mm-1
Paste/Air Ratio - 4 - 10

The air-void size distribution should also be noted as different size distributions can yield similar values of symbol and a.

Secondary deposits filling air voids

Staining

Deposits stained cannot be analyzed by any other method to determine their composition.

Stereo OM

Deposits result as water freely moves through the distressed paste. In extreme cases, the air-void system may be further compromised when significant numbers of voids are filled with secondary deposits. Common deposits include calcium hydroxide, calcium carbonate, ASR reaction products, and various sulfates including ettringite.

Petrographic OM

Secondary deposits are commonly identified using the petrographic OM.

SEM

The SEM operated at high vacuum is very useful for determining the composition of secondary deposits. Direct output of phase composition allows for absolute identification.

Microcracking around aggregates

Stereo OM
Petrographic OM

Cracking will be in the paste. If cracks pass through aggregates, check table C-3 for coarse aggregate freeze-thaw, table C-6 for ASR, and table C-7 for ACR. Cracks will fill with secondary deposits.

LVSEM

Severe cracking in the paste occurs if PCC is observed in a CSEM. Hydration products and ASR reaction products dehydrate in the high vacuum in the CSEM.


Table C-3. Diagnostic features of aggregate freeze-thaw deterioration.

Diagnostic
Feature

Method of Characterization

Comments

Cracking near joints/cracks

Staining/Spalling

Field evaluation

Has a very characteristic cracking pattern concentrated at corners, joints, and cracks (SHRP 1993).

Increased permeability results from the cracking. Calcium hydroxide is leached and re-deposits on surface where it carbonates.

Cracks through
nonreactive coarse aggregates

Visual inspection
Stereo OM
Petrographic OM
SEM

Cracks through nonreactive coarse aggregates are very typical of D-cracking. Be very careful to completely rule out alkali–aggregate reaction. See tables C-6 and C-7 for diagnostic features of ASR or ACR.

Nonuniform gaps around coarse aggregates

Visual inspection
Stereo OM

Gaps between the aggregate and paste form. These gaps may result from the dissolution of calcium hydroxide at the aggregate/paste interface or coarse aggregate dilation due to freezing. Subsequent redeposition of calcium hydroxide or calcite may occur in the cracks. Check for sulfate or ASR reaction products in cracks surrounding aggregates. A negative result helps to confirm aggregate freeze-thaw.

Known freeze-thaw susceptible aggregate

Large top size aggregate

Records review
Visual inspection
Stereo OM
SEM

Check aggregate sources for known freeze-thaw performance

Aggregate freeze-thaw is more common in large aggregates (> 38 mm) and rare in aggregates smaller than 12.5 mm.

Poor void structure in the aggregate

Petrographic OM
CSEM
LVSEM

As a percentage of the total aggregate void space, excessive amounts of voids in the aggregate with diameters less than 5 microns is thought to be detrimental to aggregate freeze-thaw resistance.


Table C-4. Diagnostic features of sulfate attack.

Diagnostic
Feature

Method of Characterization

Comments

Map cracking

Field evaluation

Paste expansion commonly results in map cracking over entire surface. In some cases, it is isolated to joints/cracks.

Deteriorated paste

Sulfate attack may result in paste “crumbling,” commonly at joints. Loose aggregate observed in resulting void.

External source
of sulfur only

Soil analysis
Deicer analysis

Identify a sole source of sulfate that is external to the concrete to confirm external sulfate attack. Having both external and internal sources confounds the diagnosis.

Internal source
of sulfur only

Records review SEM
XRD

Identify a sole source of sulfate that is internal to the concrete to confirm internal sulfate attack. Having both external and internal sources confounds the diagnosis.

Paste expansion

Stereo OM
Petrographic OM
SEM

Expansion occurs, usually over a large area. Gaps form around aggregates with the gap width proportional to the aggregate diameter.

Significant sulfate deposits in cracks and voids

Staining
Stereo OM

Stained deposits or stained paste cannot be accurately analyzed by SEM to determine their composition. A common sulfate deposit is ettringite. This is commonly recognized by acicular needle-like crystals infilling voids and cracks.

Petrographic OM

Common sulfate deposits can be identified. Mixtures with other phases may be more difficult to identify.

SEM

All deposits are readily identified using the SEM in high vacuum mode. Co-deposition with other phases may be more closely studied.

Significant sulfate deposits in the cement paste

Petrographic OM

Fluorescent dye epoxy impregnation assists in identifying microcracks in the paste. Cracks unfilled with epoxy should be assumed were created during sample polishing.

LVSEM/ESEM

Cracks resulting from sulfate expansion can be viewed in an LVSEM/ESEM but caution should be exercised in identification of micron scale microcracks. Even in an ESEM, some dehydration does occur, leading to possible cracking. Cracks unfilled with epoxy should be assumed were created in the SEM or during sample polishing. If viewing an unimpregnated specimen, cracks unfilled with secondary deposits should be assumed were created in the SEM or during sample preparation.

Microcracking

Stereo OM
Petrographic OM

For filled cracks, the cracks may have been present from other distress and secondary deposits formed in the cracks. Fluorescent dye epoxy impregnation greatly improves the identification of microcracks in the paste. Cracks not filled with epoxy are probably artifacts of sample preparation.

SEM

A characteristic spectrum for dehydrated ettringite has approximate element ratios of 1:2:4 (Al:S:Ca) by weight.


Table C-5. Diagnositc features of deicer scaling/deterioration.

Diagnostic
Feature

Method of Characterization

Comments

Staining at joints or cracks

Field evaluation

Staining results from calcium hydroxide depletion and subsequent carbonation at surface.

Scaling or crazing of slab surface

Field evaluation
Visual inspection
Stereo OM

Common visual diagnostic feature. Similar and possibly related to paste freeze-thaw damage. See table C-2 for more on paste freeze-thaw damage.

Calcium hydroxide depletion near joints

Stereo OM
Petrographic OM
SEM

Calcium hydroxide (CH) is most soluble near the freezing point of water. Cyclic freezing and thawing from repeated deicer applications can accelerate the dissolution of CH near joints/cracks.

Secondary deposits of chloroaluminates

Petrographic OM
SEM

Chloride ions released from dissolved salts can form these phases with aluminate phases in the paste.


Table C-6. Diagnostic features of ASR.

Diagnostic
Feature

Method of Characterization

Comments

Map cracking with or without exudate

Evidence of pavement expansion

Visual inspection

ASR is characterized by widespread map cracking. Can be more severe at joints and may be preferentially oriented perpendicular to the direction of least restraint (e.g., in pavement slabs, longitudinal cracks often predominate). Exudate common but not always observed.

Evidence of joint closing or shoving of shoulder or fixed structures are possible indicators of expansion.

ASR reaction product in cracks and voids

Stereo OM
Petrographic OM

A glassy clear to white amorphous reaction product resulting from an alkali–silica reaction. ASR reaction product is found within reacted particles, cracks, and air voids. The presence of ASR reaction product alone does not indicate ASR distress, as it must be of sufficient volume and composition to cause deleterious expansion.

SEM

ASR reaction product can be chemically characterized with the SEM operating at a high vacuum. Primarily high alkali (low calcium) ASR reaction products are expansive.

Reaction rims on aggregates

Visual inspection
Stereo OM
Petrographic OM
SEM

Reaction rims are often seen on most reactive aggregate. Reaction rims are common on aggregates that are undergoing ASR. Good gravel aggregates can exhibit rims that appear similar to ASR reaction rims. These are typically the result of weathering. Reaction products present help confirm ASR.

Aggregate known to be reactive

Records review

Check to see if the aggregates used were from a source that is known to be reactive.

Microcracking radiating from reacted cracked aggregates

Softening of the aggregate

Visual inspection
Stereo OM
Petrographic OM
LVSEM/ESEM

Reacted aggregates may break down internally and often partially dissolve. As the aggregate degrades, the ASR reaction product produced may be expansive and cause cracking to occur. The cracks are within the periphery of the aggregate but around the center. Often the cracks will narrow from the center of the aggregate out. Coarse and fine aggregates can both cause ASR distress. Common reactive aggregates are composed of or include chert, flint, siliceous shale, strained quartz, and porous volcanic glasses.


Table C-7. Diagnostic features of ACR.

Diagnostic
Feature

Method of Characterization

Comments

Map Cracking with or without exudate

Evidence of expansion

Visual inspection

ACR is characterized by widespread map cracking. Can be more severe at joints. Exudate common but not always observed.

Evidence of joint closing or shoving are possible indicators of expansion.

Cracks radiating from the coarse carbonate aggregate into the paste

Visual inspection
Stereo OM
Petrographic OM
LVSEM

Deterioration from ACR results from the expansion of the aggregate that causes cracks in the aggregate, which propagate into the paste. The expansion is the result of reaction products produced in the dedolomization reaction.

Aggregate known to be reactive

Records review

Check to see if the aggregates used were from a source that is known to be reactive.

Characteristic texture of ACR reactive aggregates

Petrographic OM

Most ACR reactive aggregates have a characteristic texture. ASTM C 856 states the basic texture as being relatively larger rhombic dolomite crystals in a fine-grained calcite matrix with clay and silt-sized quartz. Substantial amounts of both dolomite and calcite are present. Other textures have been reported as reacting, with a common thread being soluble magnesium phases that react to form expansive products.

CSEM
LVSEM

Calcium and magnesium silicate hydrates are common reaction products.

 

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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