16 Types of Distresses in Concrete Pavements
Concrete pavements are widely used for roads, runways, and other heavy-duty applications due to their durability, strength, and low maintenance requirements. Nevertheless, concrete pavements can still develop distresses that can impact their performance, safety, and aesthetics. These distresses can be caused by a range of factors, including environmental conditions, traffic loads, material properties, construction practices, and maintenance activities.
It is helpful to separate the different defects that are common to rigid pavements. These are distresses, including their possible causes, are described below.
1. Blowups
Blowups occur when pavement surfaces experience localised upward movement at joints or cracks, causing concrete to shatter. Blowups typically occur during hot weather when concrete slabs cannot expand due to narrow joints or cracks, and this is often caused by incompressible materials filling the joint space. When expansion cannot release enough pressure, the slab edges may buckle or shatter near the joint. Additionally, blowups may happen near utility cuts and drainage inlets. Due to the potential for severe damage to aircraft, blowups are often repaired almost immediately.
2. Corner break
This is when a crack separates a corner portion of the slab. The crack intersects the adjacent transverse and longitudinal joints at a 45-degree angle with the direction of traffic. The sides of the crack measure from 0.3m to half the width of the slab on each side of the corner. This defect is usually caused by exposure to load repetition, combined with loss of support and curling stresses.
3. Durability cracking (D-cracking)
These cracks are usually closely spaced crescent-shaped hairline cracks. Durability cracking (D-Cracking) in concrete is caused by the material’s inability to withstand environmental factors, such as freeze-thaw cycles. If left unaddressed, D-Cracking may lead to concrete disintegration within 0.3 to 0.6 m of the joint or crack.
4. Faulting
Faulting or settlement is a common pavement distress characterised by a difference in elevation at a joint or crack, which is caused by either upheaval or consolidation.
5. Joint seal damage
Damages to joint sealants refers to any condition that allows for the accumulation of soil or rocks in the joints or conditions which are susceptible to significant water infiltration. This accumulation of incompressible materials can hinder slab expansion and lead to buckling, shattering, or spalling. The probable causes of joint seal damage include stripping of the joint sealant, extrusion, weed growth, hardening of the filler, loss of bond to slab edges, and the lack of sealant in the joint.
6. Longitudinal cracking
Longitudinal cracks occur parallel to the pavement centerline. They are most likely caused by repeated loads, curling stresses, and shrinkage stresses. While low-severity longitudinal cracks are related to warping or friction and are not considered significant structural issues, medium or high-severity longitudinal cracks (known as "working" cracks) and are considered major structural distresses.
7. Map cracking (related to shrinkage cracking)
Map cracking, also known as crazing, is a term used to describe a series of shallow, interconnected cracks that only penetrate the upper surface of the slab. Typically, larger cracks appear in the longitudinal direction of the lane and are joined with finer transverse or random cracks. Map cracking is likely caused during the setting and curing of the concrete.
8. Patching
A patch refers to an area larger than 0.1 square metre where the original concrete slab has been replaced or removed, or where additional material has been applied to the pavement after initial construction. Patches are usually employed as a remedy for pavement distresses or to repair pavement following a utility cut.
9. Polished aggregate
Polished aggregate is the loss of surface mortar and paste which smooths and exposes the coarse aggregate, resulting in a noticeable decrease in surface friction. As traffic repeatedly passes over a pavement, the rough, angular particles that protrude from the surface can become polished, especially as the pavement ages.
10. Popouts
A popout is a pavement distress that results from freeze-thaw cycles as well as expansive aggregates. This distress is characterised by small pieces of pavement breaking loose from the surface, measuring 25 to 100 mm in diameter and 13 to 50 mm deep.
11. Pumping and Water Bleeding
Pumping is the expulsion of material through joints or cracks by water, which is caused by the deflection of the slab when it is subjected to passing loads. The ejected water carries particles of sand, clay, silt, or gravel, leading to a gradual loss of pavement support. Evidence of pumping includes surface staining, and base or subgrade material on the pavement close to the joints or cracks. The presence of pumping near joints indicates inadequate joint sealing and loss of support, which can cause cracking following repeated loads. Defective joint sealing must be identified before pumping can be considered present. Pumping can also happen on the joint and crack itself.
12. Punchout
Punchouts refer to broken areas that are enclosed by two closely spaced transverse cracks, a short longitudinal crack, and either the edge of the pavement or a longitudinal joint. "Y" shaped cracks that exhibit spalling, breakup, or faulting are also considered as punchouts. Punchouts can indicate a localised construction defect such as inadequate consolidation. In continuously reinforced concrete pavement (CRCP), they can be caused by steel corrosion, insufficient steel, excessively wide shrinkage cracks, or shrinkage cracks that are too close to each other.
13. Lane-to-shoulder Separation
Lane-to-shoulder separation is the widening of the joint between the edge of the slab and the shoulder. When flexible shoulders are adjacent to concrete main lanes, a slow deterioration process may occur that makes it difficult to maintain a proper seal between the concrete and the shoulders. This can allow moisture to penetrate, which leads to degradation of the underlying layers. The same logic applies to shoulder drop-offs.
14. Shoulder drop-off
A lane-to-shoulder drop-off refers to a variation in height between the traffic lane and the shoulder. Often, this occurs when the outer shoulder settles.
15. Spalling of transverse joints
The spalling of joints refers to the occurrence of cracks, chips, breaks, or fraying of the edges of a pavement slab, typically located within 0.3 metres from the transverse joint. The spalling of joints can be potentially attributed to several factors, such as the infiltration of incompressible materials or the accumulation of traffic loads that generate excessive stresses at the joint. Weak concrete at the joint in conjunction with traffic loads, can also contribute to this type of damage.
16. Transverse cracking
Transverse cracking refers to stress-induced cracks that usually run perpendicular to the centerline of a pavement. This type of cracking is likely caused by a combination of factors, including repeated loading, curling stresses, and shrinkage stresses.
All the distresses can be visualised in the figure below.
Figure 1: Distresses in Concrete Pavements
With all the potential defects that can occur on rigid pavements, is crucial for asset managers to continue monitoring their pavements. By identifying and addressing these issues in a timely manner, appropriate maintenance and repair strategies can be implemented to prevent further damage to ensure safe and efficient travel for motorists. Overall, such efforts will enable the pavement to maintain its structural integrity, thus prolonging the pavement’s lifespan.
At Pavement Management Services, we have extensive experience in the collection and analysis of road and pavement data. We perform a wide range of surveys to gather data on flexible and rigid pavement using the latest technologies. Click here to view our range of advanced pavement testing equipment.
References
FHWA (2014). Glossary - Distress Identification Manual for The Long-Term Pavement Performance Program (Fifth Revised Edition) , May 2014 - FHWA-HRT-13-092. [online] Available at: https://www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/13092/004.cfm [Accessed 31 Mar. 2023].
Indiana Department of Transportation. (2023). Indiana 2021 IDEA — PCC Distress Measurement. [online] Available at: https://www.in.gov/indot/div/aviation/pavement-inspection/pci-review/distress-measurement-pcc-main.html [Accessed 31 Mar. 2023].
Mallick, R. B. and El-Korchi, T. (2018). Pavement Engineering Principles and Practice. New York: CRC Press.