ALKALI-SILICA REACTIVITY FIELD 

 IDENTIFICATION HANDBOOK 

 Technical Report Documentation Page 

1. Report No. 

FHWA-HIF-12-022 

2. Government Accession No. 3. Recipient’s Catalog No. 

4. Title and Subtitle 

Alkali-Silica Reactivity Field Identification Handbook 

5. Report Date 

December 2011 

6. Performing Organization Code 

7. Author(s) 

Thomas, M.D.A., Fournier, B., Folliard, K.J., Resendez, Y.A. 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 

The Transtec Group, Inc. 

6111 Balcones Drive 

Austin, TX 78731 

10. Work Unit No. 

11. Contract or Grant No. 

DTFH61-06-D-00035 

12. Sponsoring Agency Name and Address 

Office of Pavement Technology 

Federal Highway Administration 

1200 New Jersey Avenue, DE 

Washington, DC 20590 

13. Type of Report and Period Covered 

Final Report December 2011 

14. Sponsoring Agency Code 

15. Supplementary Notes 

Contracting Officer’s Technical Representative (COTR): Gina Ahlstrom, HIPT-20 

16. Abstract 

Two types of alkali-aggregate reaction (AAR) are currently recognized depending on the nature of the reactive mineral; these are alkali-silica 

reaction (ASR) and alkali-carbonate reaction (ACR). Both types of reaction can result in expansion and cracking of concrete elements, leading to a reduction in the service life of concrete structures. This handbook serves as an illustrated guide to assist users in detecting and distinguishing ASR in the field from other types of damages. 

17. Key Words 

Alkali-silica reactivity, alkali-aggregate reaction, reactive 

aggregates, concrete durability, field identification, concrete 

18. Distribution Statement 

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161. 

9. Security Classif. (of this 

report) 

20. Security Classif. (of this 

page) 

21. No of Pages 22. Price 

 

 

SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

in 

ft

yd 

mi

in2 

ft2 

yd2 

ac 

mi2 

fl oz 

gal 

ft3 

yd3 

oz 

lb 

T 

o

F 

fc 

fl 

lbf 

lbf/in2 

LENGTH inches 25.4 millimeters 

feet 0.305 meters 

yards 0.914 meters 

 miles 1.61 kilometers 

AREA square inches 645.2 square millimeters 

square feet 0.093 square meters 

square yard 0.836 square meters 

acres 0.405 hectares 

square miles 2.59 square kilometers 

VOLUME fluid ounces 29.57 milliliters 

gallons 3.785 liters 

cubic feet 0.028 cubic meters 

cubic yards 0.765 cubic meters 

NOTE: volumes greater than 1000 L shall be shown in m3 

MASS ounces 28.35 grams 

pounds 0.454 kilograms 

short tons (2000 lb) 0.907 megagrams (or "metric ton") 

TEMPERATURE (exact degrees) Fahrenheit 5 (F-32)/9 Celsius 

or (F-32)/1.8 

ILLUMINATION foot-candles 10.76 lux 

foot-Lamberts 3.426 candela/m2 

FORCE and PRESSURE or STRESS poundforce 4.45 newtons 

poundforce per square inch 6.89 kilopascals 

mm 

m 

m 

km 

mm2 

m 2 

m2 

ha 

km2 

mL 

L 

m3 

m 3 

g 

kg 

Mg (or "t") 

o

C 

lx 

cd/m2 

N 

kPa 

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

mm

m

m

km 

mm2 

m2 

m2 

ha

km2 

mL 

L

m3 

m3 

g 

kg 

Mg (or "t") 

o

C 

lx 

cd/m2 

N 

kPa 

LENGTH millimeters 0.039 inches 

 meters 3.28 feet 

 meters 1.09 yards 

kilometers 0.621 miles 

AREA square millimeters 0.0016 square inches 

square meters 10.764 square feet 

square meters 1.195 square yards 

 hectares 2.47 acres 

square kilometers 0.386 square miles 

VOLUME milliliters 0.034 fluid ounces 

liters 0.264 gallons 

cubic meters 35.314 cubic feet 

cubic meters 1.307 cubic yards 

MASS grams 0.035 ounces 

kilograms 2.202 pounds 

megagrams (or "metric ton") 1.103 short tons (2000 lb) 

TEMPERATURE (exact degrees) Celsius 1.8C+32 Fahrenheit 

ILLUMINATION lux 0.0929 foot-candles 

candela/m2 0.2919 foot-Lamberts 

FORCE and PRESSURE or STRESS newtons 0.225 poundforce 

kilopascals 0.145 poundforce per square inch 

in 

ft 

yd 

mi 

in2 

ft2 

yd2 

ac 

mi2 

fl oz 

gal 

ft3 

yd3 

oz 

lb 

T 

o

F 

fc 

fl 

lbf 

lbf/in2 

*SI is the symbol for th e International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. 

(Revised March 2003) 

 

 

 

 

 

 

 

 

TABLE OF CONTENTS 

FOREWORD.............................................................................1 


INTRODUCTION.............................................................................................. 3
 

REQUIREMENTS FOR ASR .......................................................................... 5
 

FIELD SYMPTOMS OF ASR .......................................................................... 7
 

CRACKING ......................................................................................................... 7 


EXPANSION CAUSING MOVEMENTS AND DEFORMATIONS ................................. 9 


LOCALIZED CRUSHING OF CONCRETE ............................................................... 9 


EXTRUSION OF JOINT-SEALING MATERIAL ...................................................... 11
 

SURFACE POP-OUTS ......................................................................................... 11
 

SURFACE DISCOLORATION AND GEL EXUDATIONS .......................................... 11
 

EFFECT OF EXPOSURE CONDITIONS.................................................... 13
 

MOISTURE ....................................................................................................... 13 


TEMPERATURE ................................................................................................. 13 


ASR IN COMBINATION WITH OTHER DETERIORATION 


PROCESSES .................................................................................................... 15
 

ASR AND STEEL CORROSION .......................................................................... 15 


ASR AND FREEZE-THAW DETERIORATION....................................................... 15 


ASR AND DELAYED ETTRINGITE FORMATION ................................................. 15 


NON-ASR-RELATED DISTRESS................................................................. 17
 

MANAGING STRUCTURES AFFECTED BY ASR................................... 19
 

REFERENCES................................................................................................. 21
 

APPENDIX A: ASR IN BRIDGE STRUCTURES....................................... 23
 

APPENDIX B: ASR IN CONCRETE PAVEMENTS................................... 49
 

APPENDIX C: ASR IN OTHER TRANSPORTATION 


STRUCTURES................................................................................................. 61 


 

FOREWORD 

This field identification handbook provides guidance in identifying alkali-silica 

reactivity (ASR) in concrete field structures, such as bridges and pavements. The 

handbook also provides fundamental information about ASR, including the 

requirements for ASR to take place and the chemical reaction that leads to the 

formation of ASR gel. Furthermore, this handbook provides images to assist the 

reader in identifying ASR in the field under several scenarios, such as the effect of 

moisture on ASR-affected structures, ASR in combination with other concrete 

distresses, and non-ASR related distresses. A section is also dedicated to assist the 

reader in managing ASR-affected structures. 

Moreover, the appendices in this handbook have been categorized to illustrate 

ASR in bridge structures, concrete pavements, and other transportation structures. 

This document is meant to serve as a guide for assessing potential ASR structures 

in the field. As such, laboratory testing, such as petrographic analysis, should be 

conducted in order to confirm the presence of ASR in hardened concrete. 

1 
INTRODUCTION 

Two types of alkali-aggregate reaction (AAR) are currently recognized depending 

on the nature of the reactive mineral; these are: 

 Alkali-silica reaction (ASR) which involves various types of reactive silica 

(SiO2) minerals, and 

 Alkali-carbonate reaction (ACR) which involves certain types of dolomitic 

rocks (CaMg(CO3)2). 

Both types of reaction can result in expansion and cracking of concrete elements, 

leading to a reduction in the service life of concrete structures. Visual symptoms, 

such as map-cracking (Figures 1 and 2), on concrete structures affected by either 

ASR or ACR are generally similar, and a petrographic examination conducted on 

samples taken from the structure (Figure 3) is usually required to differentiate 

between the two types of reactions. A reaction product, alkali-silica gel, is 

typically observed in concrete affected by ASR. 

Cases of ACR are limited and confined to a few locations in North America; 

however, ASR is widespread throughout North America and worldwide. 

Consequently, the vast majority of illustrations shown in this document are 

examples of ASR rather than ACR. 

In many cases, there may be other destructive forces contributing to the 

deterioration observed. For example, cyclic freezing and thawing in northern 

regions can exacerbate the cracking initiated by AAR. In addition, cracks caused 

by AAR in concrete exposed to deicing salts may provide pathways, allowing 

access to chloride ions which can promote the corrosion of embedded 

reinforcement. Consideration should be given to the possibility of these other 

processes when inspecting a concrete structure for AAR. 

2 
Figure 1. Map-cracking of a sidewalk 

caused by ASR. 

Figure 2. Map-cracking of a sidewalk 

caused by ACR. 

Figure 3. Alkali-silica gel in 

petrographic thin section of concrete 

taken from an ASR-affected 

structure. 

3 
 

 

 

REQUIREMENTS FOR ASR 

ASR is a chemical reaction between the alkali hydroxides in the pore solution of 

concrete and certain forms of reactive silica minerals occurring in some 

aggregates. The reaction product, an alkali-silica gel, is hygroscopic, and will 

absorb water and swell if the concrete is in a moist environment. The swelling of 

the gel can, under certain circumstances, lead to expansion and cracking of the 

concrete. Thus, as shown in Figure 4, there are three requirements for deleterious 

ASR to occur; these are: 

A sufficient concentration of alkali hydroxides in the pore solution of 

the concrete. The main source of alkalis in concrete is the portland 

cement, which contains minor amounts of sodium and potassium. In some 

cases, additional alkalis may be supplied by other components of the 

concrete (e.g. aggregates, admixtures and supplementary cementing 

materials) or from external sources (e.g. deicing salts or seawater). 

A sufficient quantity of reactive minerals in the aggregate. Reactive 

minerals include opal, cristobalite, tridymite, volcanic glass and various 

forms of microcrystalline, cryptocrystalline and strained quartz. 

A sufficient supply of moisture. ASR ceases below a relative humidity of 

80 percent, but increases in intensity as the relative humidity within the 

concrete increases from 80 percent to 100 percent. 

The sequence of ASR is illustrated in Figure 5. 

Damage due to ASR can be avoided in new construction by either avoiding 

reactive aggregates or by controlling the availability of alkali in the concrete. 

Two ways to control the availability of alkali include the use of low-alkali cement 

and the use of suitable supplementary cementing materials. 

In existing ASR-affected structures, the rate of reaction, and hence, the rate of 

damage accumulation, can be reduced by lowering the internal relative humidity 

where possible. 

4 
Figure 4. Requirements for ASR. Silica (SiO2)

Alkali (Na, K) Water

Figure 5. Sequence of ASR. 

Reaction between the alkali hydroxides 

(Na, K & OH) from the cement and unstable silica, SiO2, in some types of 

aggregate. 

5 

SiO2 

Na+

K+

OH 

OH 

Na+

K+

OH 

OH 

Gel The reaction produces an alkali-silica 

gel. 

The gel absorbs water from the 

surrounding paste ... 

... and expands. 

The internal expansion eventually leads 

to cracking of the surrounding 

concrete. 
 

 

 

 

 

 

 

FIELD SYMPTOMS OF ASR 

Common visual symptoms of ASR generally consist of: 

Cracking 

Expansion causing deformation, relative movement, and displacement 

Localized crushing of concrete 

Extrusion of joint material 

Surface pop-outs 

Surface discoloration and gel exudations 

Brief descriptions of the symptoms are given in this section. Multiple 

photographs of these features in various transportation structures are given in the 

appendices of this handbook. 

Cracking 

The classic symptom of ASR is map cracking (also called pattern cracking or 

alligator cracking), which takes the form of randomly-oriented cracks on the 

surface of concrete elements that are relatively free (unrestrained) to move in all 

directions. An example is shown in Figure 6. In some cases, discoloration occurs 

around the cracks, often due to gel exudation in the vicinity of the cracks. 

In many cases, expansion is restrained in one or more directions due to internal 

confinement from conventional reinforcement or prestressing, or by external 

forces from abutments or adjacent structures. In such cases, more expansion 

occurs in the direction of least confinement, and the cracks become oriented in the 

same direction as the confining stresses. For example, with concrete pavements, 

the expansion is restrained in the longitudinal direction; thus, a greater amount of 

expansion occurs in the transverse direction. Hence, cracks will show a preferred 

alignment in the longitudinal direction (see Figure 7). In the case of reinforced 

concrete columns, cracks tend to be aligned vertically due to the restraint imposed 

by the primary reinforcement and the dead load (see Figure 8). For prestressed 

bridge girders, the cracks will usually be aligned horizontally due to the 

confinement imposed by the prestressing tendons parallel to the axis of the beam 

(see Figure 9). 

6 
 

 

7 

 

Figure 6. Map cracking (a.k.a. pattern cracking or alligator cracking) in a concrete wall. 

Figure 7. Preferred alignment of 

cracks in an ASR-affected concrete 

pavement. 

Figure 8. Preferred alignment of 

cracks in an ASR-affected concrete 

column. 
 

 

 

Expansion causing deformation, relative movement, and displacement 

The extent of ASR often varies between or within the various members or 

components of an affected concrete structure, thus causing distresses such as: 

relative movement or misalignment of adjacent concrete members 

deflection 

collateral damage to adjacent structures 

Figure 10 shows an example of movement. 

Localized crushing of concrete 

Expansion leading to the closure of joints can lead to localized crushing of 

concrete if incompressible material becomes lodged in the joint prior to the joint 

closing completely. The presence of the incompressible material can lead to local 

high stress concentrations. For an example, see Figure 11. 

8 
Figure 9. Preferred 

alignment of cracks on an 

ASR-affected pre-stressed 

concrete girder. 

Figure 10. Differential movement 

of parapet wall on a bridge. 

Figure 11. Expansion with associated spalling of 

concrete in abutting Jersey barrier sections 

affected by ASR. 

9 
Extrusion of joint-sealing material 

Expansion of adjacent sections results in closure of the joint. If joint-sealing 

material is present, it may be “squeezed out” of the joint as it closes, as shown in 

Figure 12. 

Surface pop-outs 

Alkali-reactive aggregates undergoing expansion near the concrete surface may 

induce the detachment of a conical portion of the mortar overlying the aggregate 

and leaving the reactive aggregate exposed in the bottom of the resulting conical 

recess. Such features are termed popouts, and more frequently result from freezethaw action on frost-susceptible rock types, such as certain varieties of chert and 

argillaceous, clayey or porous particles. See Figure 13. 

Surface discoloration and gel exudations 

Cracks caused by ASR are often bordered by a broad “brownish” zone, giving the 

appearance of permanent dampness (Figure 14). Surface gel exudations are also a 

common feature of ASR. The exudation may be alkali-silica gel or lime (or both) 

leaching from the cracked concrete. 

10 
Figure 12. Extrusion of 

joint-sealing material 

between adjacent sections 

of concrete pavement. 

Figure 13. Map-cracking 

accompanied by numerous 

pop-outs caused by shaly 

limestone particles. 

Figure 14. Surface 

discoloration and 

exudation associated with 

cracks. 

11 
EFFECT OF EXPOSURE CONDITIONS 

Moisture 

The extent of ASR in a concrete structure will vary depending on a number of factors, including the exposure conditions. Concrete that is exposed directly to moisture is likely to exhibit more severe symptoms of ASR than concrete that is less 

exposed to moisture. As an example, Figure 15 shows a bent cap where only part 

of the cap has direct exposure to moisture and consequently shows signs of 

ASR. The part of the bent cap that is not directly exposed to moisture does not 

show signs of ASR, even though they are both part of the same concrete specimen. 

The moisture conditions can also affect the visibility of cracks. For example, fine 

cracks may not be readily visible on a concrete element viewed on a dry day, but 

may be easily seen shortly after a rainfall as the surface dries (see Figure 16). The 

reason for this effect is that the cracks retain the moisture longer, and this enhances the contrast between the crack and the concrete surface. 

Temperature 

The rate of reaction is highly dependent on the composition of the concrete and 

the exposure condition (moisture availability and temperature). Typically, symptoms are manifested 5 to 10 years after construction. However, concrete containing moderately-reactive aggregates and exposed to colder northern environments 

may not show symptoms of ASR until it reaches an age of 15 years or more. Conversely, concrete containing highly reactive aggregate and exposed to hot, humid 

climates may exhibit cracking due to ASR after less than 2 years, as in Figure 17. 

12 
Figure 15. Bent cap 

showing signs of ASR only 

where the element has 

direct access to moisture. 

Figure 16. ASR cracks 

enhanced as the concrete 

starts to dry following 

rainfall. 

Figure 17. ASR-affected 

pre-stressed concrete box 

girder. Cracking became 

visible after two years. 

13 
ASR IN COMBINATION WITH OTHER DETERIORATION 

PROCESSES 

ASR can occur simultaneously with other deterioration processes or may render 

the concrete more vulnerable to these processes after ASR damage has occurred. 

ASR and steel corrosion 

Cracking due to ASR provides pathways for chloride ions from deicing salts or 

seawater to rapidly penetrate the concrete cover and initiate corrosion of 

embedded reinforcement. One instance of corroded steel is shown in Figure 18. 

ASR and freeze-thaw deterioration 

ASR can reduce the resistance of concrete to cyclic freezing and thawing, even if 

the concrete is adequately air-entrained. If cracks induced by ASR become 

saturated the freezing water will propagate and widen the cracks. Horizontal 

surfaces, such as pavements, are particularly vulnerable to this combination of 

processes. An example is shown in Figure 19. 

ASR and delayed ettringite formation 

Delayed ettringite formation (DEF) has often been found in association with ASR. 

Indeed, ASR can accelerate DEF by reducing the pH of the concrete pore solution, 

thereby expediting the release of sulfates entrapped by the hydrates during 

elevated-temperature curing. The released sulfates are then free to form ettringite, 

and this delayed formation of ettringite increases the expansion and cracking 

already contributed by ASR. Figure 20 shows effects of ASR and DEF. 

14 
Figure 18. Corrosion of 

embedded steel in ASRaffected concrete parapet 

wall. 

Figure 19. ASR cracking 

exacerbated by freezing 

and thawing of concrete 

pavement. 

Figure 20. Cracking at the 

base of a concrete column 

affected by ASR and DEF. 

15 
NON-ASR-RELATED DISTRESS 

There are many causes of cracking and other symptoms of distress in concrete; 

however, the presence of one or more of the features discussed in the previous 

sections is not necessarily an indication that ASR is the main process responsible 

for observed damage. 

Volume increase and resulting deformations and misalignments can be caused by 

sulfate attack, delayed ettringite formation and unsoundness of cement—this will 

also result in cracking. 

Cracking can result from many deterioration processes, including processes that 

lead to a volume reduction such as thermal, autogenous, plastic and drying 

shrinkage. 

Popouts can be caused by freeze-thaw action in the absence of ASR and exudation 

and staining in the vicinity of cracks can be caused by moisture movements and 

leaching of salts (e.g. efflorescence). 

All forms of deterioration should be considered when performing a condition 

survey of a concrete structure. 

The extent to which ASR (or ACR) has contributed to the observed damage can 

only be unequivocally established by taking core samples and performing a 

laboratory study, including petrographic examination. 

Table 1 shows the various symptoms associated with ASR and provides an 

indication of the probability of ASR occurring based on the presence and extent of 

the symptoms. 

16 
Table 1. Classification System for the Condition Survey 

(modified from CSA, 2000). 

Feature Probability of ASR 

Low Medium High 

Expansion and/ 

or 

displacement of 

elements 

None Some evidence (e.g., 

closure of joints in 

pavements, Jersey 

barriers, spalls, 

misalignments between 

structural members) 

Fair to extensive signs of 

volume increase leading 

to spalling at joints, 

displacement and/or 

misalignment of 

structural members 

Cracking and 

crack pattern 

None Some cracking pattern 

typical of ASR (e.g., 

map cracking or cracks 

aligned with major 

reinforcement or stress) 

Extensive map cracking 

or cracking aligned with 

major stress or 

reinforcement 

Surface 

discoloration 

None Slight surface 

discoloration associated 

with some cracks 

Many cracks with dark 

discoloration and 

adjacent zone of light 

colored concrete 

Exudations None White exudations 

around some cracks; 

possibility of colorless, 

jelly-like exudations 

Colorless, jelly-like 

exudations readily 

identifiable as ASR gel 

associated with several 

cracks 

17 
MANAGING STRUCTURES AFFECTED BY ASR 

Performing a condition survey is one part in the process of managing structures 

affected by ASR. Depending on the structure and the requirements of the owner, 

there may be no further testing beyond a detailed site investigation. A great many 

ASR-affected structures remain in service without measures to mitigate the effects 

of or retard the rate of the reaction. Sudden structural collapse in concrete 

components affected by ASR is rare. However, if no measures are taken to 

address the symptoms or abate the reaction, continuing ASR may result in 

serviceability problems, increased maintenance costs, accelerated deterioration 

due to other mechanisms, and reduced service life. 

As mentioned previously, a confirmed diagnosis as to the presence and extent of 

ASR requires laboratory testing and petrographic examination of cores. By 

combining the results of the laboratory investigation and the symptoms from the 

site investigation, an experienced engineer can determine the likely contribution 

of ASR to the observed damage. From this diagnosis, it may be possible to 

immediately recommend measures to mitigate the reaction and its effects. On the 

other hand, a decision may be made to instrument the structure and monitor future 

behavior before deciding on a course of action. Alternatively, as discussed above, 

the decision may be to do nothing more than continue to inspect the structure on a 

routine basis. 

This handbook is only intended to aid the inspector in identifying the symptoms 

of ASR; Figure 21 shows where a routine inspection or detailed site investigation 

may fit within the scope of a comprehensive analysis of an ASR-affected 

structure. Guidelines on the management of affected structures including 

laboratory testing, field monitoring and mitigation techniques are provided 

elsewhere (CSA, 2000; FHWA, 2010). 

18 
Figure 21. General flowchart showing steps in a comprehensive ASR investigation 

(modified from CSA, 2000). 

19 
REFERENCES 

“Guide to the Evaluation and Management of Concrete Structures Affected by 

Alkali-Aggregate Reaction,” CSA A864-00, Canadian Standards Association, 

Toronto, p.108, 2000. 

Fournier, B., et al., “Report on the Diagnosis, Prognosis, and Mitigation of AlkaliSilica Reaction (ASR) in Transportation Structures,” Federal Highway 

Administration, Report. No. FHWA-HIF-09-004, Washington, D.C., 147 p., 2010. 

Sutter, L.L., Peterson, K.R., Van Dam, T.J., Smith, K.D., Wade, M.J., “Guidelines 

for Detection, Analysis, and Treatment of Materials-Related Distress in Concrete 

Pavements—Volume III: Case Studies Using the Guidelines,” Federal Highway 

Administration, Report No. FHWA-RD-01-165, Washington, D.C., August 2002. 

Van Dam, T.J., Sutter, L.L., Smith, K.D., Wade, M.J., Peterson, K.R., “Guidelines 

for Detection, Analysis, and Treatment of Materials-Related Distress in Concrete 

Pavements—Volume I: Final Report,” Federal Highway Administration, Report 

No. FHWA-RD-01-163, Washington, D.C., August 2002. 

Van Dam, T.J., Sutter, L.L., Smith, K.D., Wade, M.J., Peterson, K.R., “Guidelines 

for Detection, Analysis, and Treatment of Materials-Related Distress in Concrete 

Pavements—Volume II: Guidelines Description and Use,” Federal Highway 

Administration, Report No. FHWA-RD-01-164, Washington, D.C., August 2002. 

20 
COLLECTION OF PHOTOGRAPHS OF ASR-AFFECTED 

STRUCTURES 

Appendix A: ASR in Bridge Structures 

Appendix B: ASR in Concrete Pavements 

Appendix C: ASR in other Transportation Structures 

21 
APPENDIX A: ASR IN BRIDGE STRUCTURES 

Figure A1. Minor cracking in a concrete bridge deck. 

Initially cracks form close to the transverse or longitudinal joints and tend to be 

orientated perpendicular to the joint. 

Figure A2. Moderate cracking in a bridge deck. 

As ASR advances, the expansion in the longitudinal direction is restrained and 

increased expansion occurs in the transverse direction. Consequently, cracks tend 

to be oriented longitudinally. 

22 
23 

Figure A3. Moderate cracking in bridge abutment and parapet wall. 

Note the discoloration (staining) to the surface of the concrete adjacent to the 

crack. There are also indications that there is some corrosion of the embedded 

steel as revealed by the rust spots at the surface of the concrete. 

Figure A4. Severe cracking of bridge abutment. 

Crack widths in excess of 1⁄4 to 1⁄2 inch (5 to 10 mm) are evident in some locations. 

24 
25 

Figure A5. Moderate cracking in a precast, prestressed box-girder. 

Cracking occurred within a few years of construction. In the end block, adjacent 

to the abutment, cracking is randomly oriented, but is orientated longitudinally in 

the main span as the pre-stressing tendons restrain expansion in this direction. 

Figure A6. Moderate to severe cracking is a post-tensioned concrete bridge 

girder. 

Note that the main crack appears to follow the line of a draped post-tensioning 

tendon. 

26 
27 

Figure A7. Severe cracking in the top chord of a reinforced concrete arch 

bridge. 

The cracks follow the shape of the arch and are aligned with the direction of the 

primary reinforcement. 

Figure A8. Cracking on the underside of the arch shown in Figure A7. 

Crack widths up to 1⁄4 to 1⁄2 inch (5 to 10 mm) were observed. 

Note the white exudation associated with cracks in both figures. This was found 

to be predominantly calcium carbonate with lesser amounts of potassium 

indicating both lime and alkali leaching from the concrete. 

28 
29 

Figure A9. Severe cracking of reinforced-concrete bridge. 

Cracks are orientated in the longitudinal direction of the Y-shaped columns and 

the horizontal girder. Note there are signs of corrosion (rust spots) on the edge 

beam. 

Figure A10. Very severe cracking of column foundation in bridge shown in 

Figure A9. 

Note that the cracks are orientated randomly in the foundation block as there are 

lesser amounts of steel and no principle orientation of the steel. 

30 
31 

Figure A11. Misalignment of a parapet wall. 

The wall on the left of the photograph sits on the bridge abutment whereas the 

wall on the right sits on the bridge deck. The displacement between the walls is 

slightly more than 1 inch (25 mm). 

Figure A12. Crushing of concrete on a parapet wall. 

Expansion due to ASR has caused the joint between the adjacent wall sections to 

close. Incompressible material trapped between the two sections caused the buildup of concentrated stresses which led to crushing of the concrete. 

32 
33 

 

Figure A13. Moderate cracking of a reinforced concrete column. 

The wider cracks are aligned vertically due to the restraint imposed by the 

primary reinforcement and the dead load. Narrow randomly-orientated cracks are 

also visible. 

Figure A14. Moderate to severe cracking on a reinforced concrete column. 

As with the Figure A13, the main cracks are aligned vertically. There is some 

evidence from petrographic examination that delayed ettringite formation may 

have contributed to the cracking of the concrete in this case. 

34 
35 

Figure A15. Moderate cracking in a reinforced bridge column. 

ASR initiated cracking, thereby allowing deicer salts to penetrate the concrete 

cover and initiate corrosion of the embedded steel reinforcement. 

Figure A16. Moderate cracking in a reinforced concrete pier. 

Cracking is only apparent at the end of the pier which is exposed directly to 

moisture. Concrete under the cover of the bridge deck does not appear to be 

damaged. 

36 
37 

Figure A17. Minor cracking on an edge beam supporting the bridge railing. 

The tight cracks with associated discoloration are typical of the first symptoms of 

ASR 

Figure A18. Severe cracking on an edge beam supporting the bridge railing. 

Advanced ASR has led to an extensive network of cracks which has been opened 

up by freeze-thaw cycles leading to spalling of the concrete. 

38 
39 

Figure A19. Moderate cracking in a wing wall. 

The cracking of the wing wall is accompanied by surface discoloration and gel 

exudation. 

Figure A20. Moderate cracking in a wing wall. 

Expansion of the concrete has led to the formation of a vertical crack forming 

along the length of the wall. It is likely that the crack forms between two mats of 

reinforcement at the back and front face of the wall. 

40 
41 

Figure A21. Severe cracking of a bridge abutment. 

The damage is far more advanced in the part of the abutment that is exposed 

directly to moisture. The part of the abutment sheltered by the bridge deck shows 

only minor ASR cracking. 

Figure A22. Moderate cracking of a massive concrete pier. 

The combined effects of ASR and freeze-thaw cycles have led to cracking and 

surface spalling of the pier. There is also corrosion of the non-structural 

reinforcement, leading to some spalling of the surface (right of photo). 

42 
43 

Figure A23. Cracking of abutment of bridge undergoing demolition. 

ASR cracking is clearly visible in the portion of the abutment that was above 

grade and exposed to the elements during exposure but much less visible in the 

portion that was below grade in service. 

Figure A24. Enlargement of Figure A23. 

This photograph shows the contrast between the appearance of the concrete that 

was above grade (top) and below grade (bottom) during service. Wetting and 

drying, combined with freezing and thawing, tends to open up the cracks at the 

surface and promotes discoloration (staining) around the cracks. Below grade the 

cracks are finer and less visible; however, the extent of ASR within the concrete is 

the same above and below grade. 

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Figure A25. Cracking on underside of bridge. 

This photograph shows moderate ASR cracking on the underside of a bridge. The 

cracks are aligned longitudinally, reflecting the direction of the primary 

reinforcement and pre-tensioning. 

Figure A26. Cracking on the underside of a bridge deck. 

Some salt exudation is observed in association with the cracking (bottom of 

photo). 

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APPENDIX B: ASR IN CONCRETE PAVEMENTS 

Figure B1. Minor cracking in a concrete pavement. 

The first symptoms of ASR in a concrete pavement are often cracks starting at and 

running perpendicular to the transverse or longitudinal joints. 

Figure B2. Moderate cracking at the corner of pavement slabs. 

Map cracking often appears first at the corner of pavement slabs. 

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Figure B3. Moderate cracking following the perimeter of pavement slabs. 

As ASR advances, the cracks spread around the perimeter of the slabs and there is 

often little or no cracking in the center of the slab. The reason that the region 

around the joints is more prone to cracking is because (a) there is often more 

moisture available at the joints, (b) there is less restraint to expansion close to the 

joints, and (c) mechanical stresses to vehicular loading are higher at the joints. 

Figure B4. Moderate D-cracking of concrete. 

This photograph shows durability or D-cracking, and the pattern of the cracks is 

similar to that shown in Figure B3 above. However, the mechanism is very 

different as D-cracking results from the expansion of frost-susceptible aggregates. 

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Figure B5. Severe cracking of a concrete pavement. 

As ASR advances, the whole surface of the concrete pavement exhibits cracking. 

Usually the cracks become oriented in the longitudinal direction. 

Figure B6. Severe map cracking in a concrete pavement. 

Although it is usual to observe preferred orientation of cracks in pavements with 

advanced ASR, map-cracking is often observed. It is possible, in such cases, that 

drying shrinkage at the pavement surface contributes to the pattern of cracking. 

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Figure B7. Concrete pavement slab exhibiting drying shrinkage. 

The photograph shows extensive map-cracking of a pavement slab. Petrographic 

examination of the concrete revealed no evidence of ASR, and the cause of the 

cracking is assumed to be drying shrinkage; the pavement is located in an arid 

environment. 

Figure B8. Spall occurring at a joint in a concrete pavement. 

As ASR advances, the cracked concrete at the vicinity of the joint may be further 

distressed by the action of freezing and thawing, and vehicular loading. 

Eventually, spalling starts to occur at the joint. 

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Figure B9. Spall and “repaired” spall at a joint in a concrete pavement. 

In many cases, spalling at joints is likely to continue and may require patching. 

Figure B10. Severe deterioration of a concrete pavement. 

In severe cases, extensive patching can only delay the time until a major repair or 

replacement is required. 

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Figure B11. Severe cracking in a concrete pavement. 

Preferred orientation of cracks in the longitudinal direction. 

Figure B12. Crushing of concrete and extrusion of joint-sealing material in 

concrete pavement slabs. 

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APPENDIX C: ASR IN OTHER TRANSPORTATION 

STRUCTURES 

Figure C1. Moderate ASR map-cracking in a highway barrier. 

The photograph shows map-cracking and surface discoloration of a highway barrier wall. 

Figure C2. Moderate ASR oriented cracking in a highway barrier. 

In many cases, barrier walls, especially continuous slipformed barriers, will exhibit cracking with preferred orientation (horizontal) due to the restraint to expansion in the direction of the wall. 

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Figure C3. Light to moderate cracking at the top of a highway barrier wall 

and severe deterioration at the base of the wall. 

Light to moderate cracking due to ASR is evident in the top portion of the wall. 

Freeze-thaw action has exacerbated the damage in the bottom portion of the wall, 

and this has led to severe spalling of the haunches. 

Figure C4. Failure of concrete barrier wall. 

The photograph shows severe expansion, cracking and spalling of a barrier wall 

due to ASR. Freeze-thaw has most likely contributed to the deterioration. 

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Figure C5. Localized spalling of concrete barrier wall. 

The photograph shows moderate map-cracking of the barrier wall resulting from 

ASR. Freeze-thaw deterioration and spalling has occurred to the haunch just 

above grade. 

Figure C6. Moderate cracking of the foundation for a high-mast light pole. 

Cracking orientated vertically due to restraint imposed by reinforcement and 

embedded bolts for securing pole. 

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Figure C7. Moderate cracking of the foundation for a light pole. 

Random cracking with excessive exudation resulting from freeze-thaw 

deterioration (not ASR). 

Figure C8. Minor cracking of curb. 

Preferred orientation in the horizontal direction due to restraint. 

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Figure C9. Moderate cracking in sidewalk due to alkali-silica reaction (ASR). 

Figure C10. Severe cracking in sidewalk due to alkali-carbonate reaction 

(ACR). 

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FHWA-HIF-12-022