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Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction.

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Presentation on theme: "Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction."— Presentation transcript:

1 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. Description of Problem: Cracking, staining, exposure of aggregate in edge of concrete roof Possible Contributing Factors: Outdoor exposure Unprotected from rain Poor drip edge detail above No drip detailing at bottom of fascia The loss of cement paste and spalling on the fascia are suggestive of freezing damage to the surface of the concrete, and imply some poor curing practices during construction The staining cracks behind suggest that water has penetrated into the concrete and is causing the corrosion of the reinforcement. Consider Further Structural Cracking failure Freeze-thaw cracking Reinforcement corrosion D-cracking Extensive further tests are not warranted in this instance. Some structural analysis to determine whether any of the cracks are structural in origin may be useful, but the solution to both freeze-thaw and corrosion problems in this instance is to make sure that water ceases to run down the edge of the roof structure. This can be accomplished by providing proper flashing details, including a drip edge at the edge of the roofing.

2 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Shrinkage Cracking D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. This 5 year old exterior column has been treated with a light sandblasting, which removed some of the cement paste from the surface, and made the column susceptible to water penetration. This treatment has exposed a zone of poorly consolidated concrete at the column base. There is an extensive pattern of cracking in the columns, which is unlikely to be of structural origin. The incomplete consolidation of the concrete would make it vulnerable to shrinkage or structural cracking. Corrosion damage cannot be ruled out due to the continuous access to moisture. Consider Further failure Freeze-thaw cracking Reinforcement corrosion Shrinkage Cracking Alkali-aggregate reactionng Identification of the causes of damage to this column will require a testing program. Cores should be extracted from an inconspicuous location for petrography, to determine the extent of rock pockets and the presence of air entrainment. Half-cell potential testing of the reinforcement could rule out corrosion damage, while in-situ stress measurements could determine the likelihood of a structural origin for the vertical cracking. Click for View of Shaft Description of Problem: Cracking of architectural column Possible Contributing Factors: Outdoor exposure Unprotected from rain Ponding water at pedestal Architectural treatment Poor consolidation

3 Rule Out? Structural Cracking Structural failure Freeze-thaw effects Reinforcement corrosion Shrinkage cracking D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. Description of Problem: Spalling, exposed reinforcement in folded plate concrete roof Possible Contributing Factors: Outdoor exposure Unprotected from rain No drip edge detail above No roof membrane above Insufficient cover on reinforcement The spalling on the fascia is suggestive of freezing damage to the surface of the concrete. However, the spalling could also result from expansion due to accumulation of products of corrosion within the reinforcement of the shell roof. Both problems are exacerbated by the continual presence of water, due to the absence of a roof membrane and the edge detailing of the roof. Consider Further failure Freeze-thaw effects Reinforcement corrosion D-cracking Extensive further tests are not warranted in this instance. The solution to both freeze-thaw and corrosion problems in this instance is to make sure that water ceases to run down the edge of the roof structure. This can be accomplished by providing proper flashing details, including a drip edge at the edge of the roofing. It is probably of interest to determine the extent of the initiation of corrosion through half-cell potential testing of the reinforcement in the roof.

4 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Shrinkage Cracking D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. Description of Problem: Cracking, staining, spalling of concrete around interior downspout Possible Contributing Factors: Water ingress around downspout Exterior exposure Concrete consolidtion Although tbe basic problem here is obviously a leaking roof drain/downspout system, the initiation of concrete damage may be at a shrinkage crack, or a structural crack (the location is in a zone of stress concentrations), or may be due to freeze-thaw action. It apparent that corrosion of the reinforcement has initiated at this location. Consider Further Structural Cracking failure Freeze-thaw cracking Reinforcement corrosion Shrinkage cracking D-cracking Prior to undertaking repairs to these locations (all of the downspouts in this building are showing a similar pattern of damage), a delamination survey of the roof deck should be undertaken to estimate the areas of concrete requiring removal. The extent of corroded reinforcement should be investigated through half-cell potentials, and the extent of unsound concrete should be investigated through the use of a rebound hammer (ASTM C805) or other means.

5 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion Concrete quality Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. Description of Problem: Cracking, staining, exposure of aggregate in edge of concrete roof Possible Contributing Factors: Outdoor exposure Unprotected from rain Poor drip edge detail above Drip detailing at bottom Concrete cover The spalling of the concrete cover at this location is due to some combination of freeze-thaw and corrosion effects, possibly exacerbated by poor concrete quality (lack of air entrainment, reactive aggregate, etc. The corrosion is already widespread, and is threatening the structural integrity of the beam. Consider Further Structural failure Freeze-thaw cracking Reinforcement corrosion Concrete quality -cracking In addition to undertaking repairs of the obvious damage, it is necessary to investigate whether the concrete in this project in general is worth salvaging through petrographic analysis of cores extracted from damaged locations, and through in-situ cover and strength testing. The residual capacity of beams damaged to this extent also needs to be investigated by structural analysis.

6 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. Description of Problem: Map cracking of beam soffit in outdoor canopy; rust staining In an area that is displaying significant problems with reinforcement corrosion and other water damage to concrete, the presence of cracking in this beam is particularly suggestive of corrosion, especially given the rust staining. However, the extent and character of the cracking, and the extent of the problems throughout the project may also suggest some problem inherent to the concrete. Consider Further failure Freeze-thaw cracking Reinforcement corrosion Alkali-aggregate reaction cracking This area requires an extensive testing program to determine the extent of the issues. Petrographic analysis of specimens of the concrete should be undertaken to determine the source of some of the concrete problems. Other areas of concrete with inadequate cover on the reinforcement should be located with a cover meter. The extent of the corrosion activity should be surveyed, and the in-situ strength of the concrete at selected locations should be determined. Possible Contributing Factors: Outdoor exposure Concrete quality Inadequate reinforcement cover

7 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. Description of Problem: Cracking, staining, exposure of reinforcement in end of concrete beam Possible Contributing Factors: Outdoor exposure Unprotected from rain Inadequate cover on reinforcement No drip detailing Poor quality concrete Water draining from the roof has penetrated the end of the concrete beam, causing freeze-thaw damage, and initiating corrosion of the reinforcement. It is also possible that a bearing failure has initiated at the top of the pier. Consider Further Structural failure (bearing) failure Freeze-thaw cracking Reinforcement corrosion D-cracking Extensive further tests are not warranted in this instance. Some structural analysis to determine whether any of the cracks are structural in origin may be useful, but the solution to both freeze-thaw and corrosion problems in this instance is to make sure that water ceases to run down the edge of the roof structure. This can be accomplished by providing proper flashing details, including a drip edge at the edge of the roofing.

8 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. Description of Problem: Spalling of concrete on corner of column Possible Contributing Factors: Outdoor exposure poor quality concrete (probably high w/c ratio) The loss of cement paste and spalling on the fascia are suggestive of freezing damage to the surface of the concrete, and imply some poor curing practices during construction The staining cracks behind suggest that water has penetrated into the concrete and is causing the corrosion of the reinforcement. Consider Further failure Freeze-thaw cracking D-cracking Extensive further tests do not appear to be warranted in this instance. The tips of the corners are spalling due to penetration by moisture followed by freeze-thaw damage.

9 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. This balcony area admits large volumes of rainwater without adequate provisions for removal of the water. As a result, the water permeates the concrete, causing staining, promoting freeze-thaw damage, and causing corrosion of the reinforcement. The problem is exacerbated by apparently poor quality concrete, and totally inadequate cover over some of the reinforcement. Consider Further Structural Cracking failure Freeze-thaw cracking Reinforcement corrosion D-cracking This area requires a testing program to determine the extent of the issues. Petrographic analysis of specimens of the concrete should be undertaken to determine the source of some of the concrete problems. Other areas of concrete with inadequate cover on the reinforcement should be located with a cover meter. The extent of the corrosion activity should be surveyed, and the in-situ strength of the concrete at selected locations should be determined. Description of Problem: Cracking, staining, spalling, exposure of reinforcement in edge of concrete balcony Possible Contributing Factors: Outdoor exposure Unprotected from rain Poor drip edge details Lack of waterproofing or drainage of balcony slab

10 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. This sidewalk area admits large volumes of rainwater without adequate provisions for removal of the water. As a result, the water permeates the concrete,, promoting freeze-thaw damage, and possibly causing corrosion of the reinforcement. The problem is exacerbated by apparently poor quality consolidation of the concrete. Consider Further failure Freeze-thaw cracking Reinforcement corrosion D-cracking Alkali-aggregate reactionc This area requires a testing program to determine the extent of the issues. Petrographic analysis of specimens of the concrete should be undertaken to determine the source of some of the concrete problems. The extent of the corrosion activity should be surveyed,. Description of Problem: Map cracking on exterior wall Possible Contributing Factors: Outdoor exposure Unprotected from rain improper consolidation moisture intrusion from sidewalk edge

11 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. This canopy admits large volumes of rainwater without adequate provisions for removal of the water. As a result, the water permeates the concrete,, promoting freeze-thaw damage, and possibly causing corrosion of the reinforcement. The cracking has the characteristic pattern of D-cracking (freeze-thaw damage to the aggregate rather than to the cement matrix, but other factors must also be ruled out by testing. Consider Further failure Freeze-thaw cracking Reinforcement corrosion D-cracking Alkali-aggregate reactionc This area requires a testing program to determine the extent of the issues. Petrographic analysis of specimens of the concrete should be undertaken to determine the source of some of the concrete problems. The extent of the corrosion activity should be surveyed,. Description of Problem: Map cracking on underside of canopy beam Possible Contributing Factors: Outdoor exposure Unprotected from rain moisture intrusion from roof above

12 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. The diagonal cracks are characteristic of shearing forces in concrete, suggesting either uneven bearing on the bottom corner of the panel closer to the wall or pushing out of the wall. The most likely cause is differential expansion/contraction between the column enclosed by the panels and the wall. Consider Further Structural Cracking failure Freeze-thaw cracking This condition does not require an extensive diagnostic problem. The other columns should be monitored and a repair program should be initiated. Description of Problem: Diagonal cracking on precast concrete column enclosure Possible Contributing Factors: Outdoor exposure Unprotected from rain Improper provisions for expansion and contraction of underlying structure

13 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Shrinkage cracking D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. This column has been experiencing severe problems with cracking and spalling due to a combination of reinforcement corrosion and freeze-thaw action, exacerbated by low quality concrete. The column has been patched in several areas, including the exterior corner at the base shown here. Consider Further failure Freeze-thaw cracking Reinforcement corrosion Shrinkage cracking The regularly spaced cracks are characteristic of shrinkage, and in fact, the material is shrinking visibly. It is highly probably that the patching material was over-watered, causing it to shrink on drying. Improper curing of the patch material may also have contributed to the problem. The underlying reinforcement corrosion has apparently not been addressed. Description of Problem: Map cracking in a concrete patch Possible Contributing Factors: Outdoor exposure Unprotected from rain improper installation of patch

14 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. The concrete in this beam appears to have been very poorly consolidated, as honeycombing is evident in this photogrraph. The cracking is suggestive of shrinkage. Shrinkage cracking in across dimensions as small as the depth of this beam is uncommon, and would imply a very high water-cement ratio or improper curing of the concrete, the latter being more likely in this case. Consider Further failure Freeze-thaw cracking Reinforcement corrosion Alkali-aggregate reaction This area requires a testing program to determine the extent of the issues. Petrographic analysis of specimens of the concrete should be undertaken to determine the source of the problems, and to rule out reactive aggregate. The extent of the corrosion activity should be surveyed. Description of Problem: Cracking and rock pockets on end of canopy beam Possible Contributing Factors: Outdoor exposure Improper consolidation

15 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. The pattern of cracking is suggestive of bending in the thin flange of the double tee along a diagonal axis. The cause appears to be the restaint of the flanges in the vertical and horizontal direction. As the supports of the tee settle, the flanges tend to be bent upwards. Consider Further Structural crackingfailure Freeze-thaw cracking Reinforcement corrosion No testing is warranted in this case. Drainage should be maintained the the development of the cracks should be monitored, especially for evidence of corrosion. Description of Problem: Diagonal cracks in flange of precast double tee in a parking garage. Possible Contributing Factors: Exposure to water, salt Restraint of vertical and horizontal movements

16 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. The concrete in this four year old structure is generally of very poor quality, as evidenced by premature cracking and freeze-thaw damage. This crack has the appearance of a shear crack in a short cantilever bracket that is seriously overloaded. The crack may also be due to shrinkage of the concrete, or freeze-thaw action. Consider Further Structural cracking Structural failure Freeze-thaw cracking Reinforcement corrosion It is necessary in this case to rule out a structural effect that might precipitate a failure of the structure. This can be done by carefully examining the loading conditions on this bracket and determining whether large loads from the upper floor are being transferred directly to the short cantilever. It is also necessary to determine whether continuous reinforcing is present, especially in the top of the bracket. If a structural failure can be ruled out, it is still necessary to determine the extent of the corrosion and to arrest the further progression of the corrosion. Description of Problem: Vertical crack and staining of a short beam cantilever in a parking garage Possible Contributing Factors: Exposure to water and salt Concrete quality

17 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. This crack results from transfer of beam loads to the corner of the panel, rather than the column that is designed to support the beam. The resulting overstress in the wall panel has caused the development of a shear crack. Consider Further Structural Cracking Reinforcement corrosion This crack does not appear to be severe, or to be associated with any impending structural failure. Monitoring of the development of the crack, or removal of a small amount of concrete and patching are sufficient. Consideration should be given to testing for the initiation of corrosion activity by testing half-cell potentials. Description of Problem: Diagonal crack in solid panel between columns and beam Possible Contributing Factors: Outdoor exposure

18 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. The fact that the cracking is located adjacent to aluminum handrail posts is suggestive of galvanic corrosion due to the influence of reinforcing steel on the embedded aluminum. Freeze-thaw and corrosion of the reinforcement are other potential causes of the observed cracking that must be ruled out. Consider Further failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metal corrosion This area requires a testing program to determine the extent of the issues. Specimens of the embedded aluminum should be examined for evidence of corrosion activity. The extent of the corrosion activity should be surveyed. Description of Problem: Diagonal cracks at anchorage for handrail posts on balcony Possible Contributing Factors: Outdoor exposure Exposure to rainwater

19 Rule Out? Structural Cracking Structural failure Freeze-thaw cracking Reinforcement corrosion Dissimilar metals corrosion D-cracking Alkali-aggregate reaction Click to see factors to consider further Click once for explanation of factors ruled out. Click again for review of appropriate testing procedures. This beam has been previously repaired due to corrosion of the bottom reinforcement and delamination of the cover concrete from the bottom of the beam. A further longitudinal crack has developed in the top of the beam. The crack could be due to corrosion along the length of the top reinforcement, or it could signal the initiation of a more serious compression failure of the concrete in the top of the beam. Consider Further Structural cracking Freeze-thaw cracking Reinforcement corrosion This area requires a testing program to determine the extent of the corrosion, in particular to check for the presence of top reinforcement, and for evidence of corrosion activity in the top reinforcement. If corrosion is ruled out, it is necessary to consider the possibility that the cracking is a structural effect. Description of Problem: Longitudinal cracking at the top of a repaired concrete beam Possible Contributing Factors: Outdoor exposure Poor quality concrete


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