Concrete pavements can suffer from a variety of distresses that can lead to failure. These pavement distresses, as well as their specifics, are explored.
Distresses in Concrete Pavements:
Types and Causes The following are the various forms of concrete pavement distresses and their causes:
a) Cracking of Concrete Pavements
Cracks in concrete pavements are frequently created by forces caused by the pavement’s expansion and contraction or warping. Overloading, a lack of subgrade support, and insufficient and/or incorrectly cut joints, operating separately or in combination, are all possibilities. There are several forms of cracking that can occur:
(I) Cracks in the longitudinal, transverse, and diagonal directions This sort of distress is frequently caused by a combination of recurrent loads and shrinking pressures. It’s distinguished by fissures that split the slab into two or three sections. Poor construction procedures or weak underlying pavement layers can cause these types of fissures.Corner Breaks
(iii) Longevity Cracking “D” cracking is characterised by a pattern of cracks running parallel to and near a joint or linear crack. It’s caused by concrete’s inability to endure environmental conditions including freeze-thaw cycles due to fluctuating temperatures. Within 1 to 2 feet (30 to 60 cm) of the joint or crack, this form of cracking can lead to concrete disintegration.
(iv) Damage to Joint Seals (Any situation that causes soil or rocks to build in the joints or allows water infiltration is considered joint seal degradation. The buildup of materials inhibits the slabs from expanding, which can lead to buckling, shattering, and spalling. Pumping or subbase deterioration can be caused by water intrusion through joint seal damage.Stripping of joint sealant, extrusion of joint sealant, hardening of the filler (oxidation), loss of binding to the slab edges, and lack of sealant in the joint are all common kinds of joint seal deterioration. Improper joint width causes joint seal degradation.
b) Disintegration of Concrete Pavements
Shattered Slab shattered slab is one that has been broken up into four or more fragments by intersecting fissures. Overloading and/or insufficient foundation support are to blame. The breaking up of a pavement into small, loose particles, which includes the dislodging of aggregate particles, is known as disintegration. This distress can be caused by poor concrete curing and finishing, the use of inappropriate particles, and poor concrete mixing. There are four types of disintegration: I Sizing, Cracking, and Crazing of Maps The erosion and loss of the wearing surface is referred to as scaling. Scaling can occur on a surface that has been compromised by incorrect curing or finishing, as well as freeze-thaw cycles. A network of small hairline cracks that only extend through the upper surface is referred to as map cracking or crazing.
Crazing is caused by faulty concrete curing and/or finishing, and it can result in surface scale. Another form of discomfort linked with map cracking is alkali-silica reactivity (ASR). ASR is generated by an expanding reaction between silica-containing aggregates and the cement paste’s alkaline pore solutions. Joint Spalling (ii)The breakdown of the slab edges within 2 feet (60 cm) of the joint side is known as joint spalling. A joint spall does not normally run vertically through the slab, but rather intersects it at an angle. Excessive strains at the joint or fracture caused by infiltration of incompressible materials or poor concrete at the joint (induced by overworking) mixed with traffic loads are common causes of joint spalling.
Dowels, which help limit slab movement, can also cause joint spalling if they become misaligned due to faulty placement or slippage preparation.Corner Spalling The ravelling or breakdown of the slab within 2 feet (60 cm) of the corner is known as corner spalling. The spall, unlike a corner break, frequently angles downhill to cross the joint, whereas a break runs vertically through the slab. Corner spalling is caused by the same mechanisms that generate joint spalling, but because of higher exposure, this type of pain may emerge sooner. Blowups Blowups commonly happen when a transverse crack or joint isn’t broad enough to allow the concrete slabs to expand. Infiltration of incompressible materials into the system can cause insufficient width.
When expansion pressure cannot be released, the slab edges will buckle or fracture in the region of the joint. Blowups are most common in thin pavement portions, however they can also occur around drainage features (manholes, inlets, etc.). Due to the additional heat absorbed by the dark asphalt surface, the frequency and severity of blowups may increase with an asphalt overlay. They are more common in warmer weather due to the concrete’s increased thermal expansion.
c) Distortion in Concrete Pavements
Distortion is a shift in the initial position of the pavement surface caused by foundation settlement, expansive soils, frost-susceptible soils, or fines loss due to poorly built subdrains or drainage systems. There are two forms of distortion that commonly occur: Pumping is defined as the ejection of water and subgrade (or subbase) material through joints or fissures in a pavement due to the deformation of the slab when loaded. When water is ejected, it brings gravel, sand, clay, or silt with it, causing a gradual loss of pavement support that can lead to cracking.Surface staining and base or subgrade material on the pavement near seams or fissures are signs of pumping. Poor joint-loading is indicated by pumping near joints.
d. Skid Resistance of Concrete Pavements
A change in elevation at a joint or crack caused by upheaval or non-uniform consolidation of the subgrade or subbase material is known as settlement or faulting. Loss of fines, frost heave, loss of weight transfer device (key, dowel, etc.) or swelling soils can all cause this situation.d. Concrete Pavement Skid Resistance The ability of a pavement to offer a surface with the necessary friction characteristics in all weather circumstances is referred to as skid resistance. It is caused by the roughness of the surface or the accumulation of pollutants. I Aggregates that have been polished Under heavy traffic, some aggregates polish quickly. When utilised in the pavement without being crushed, naturally polished aggregates create a hazard. The natural polished stones are crushed to produce rough angular sides that provide good skid resistance.
Rubber deposits that accumulate over time will diminish a pavement’s surface friction properties. Surface friction will also be reduced by oil spills and other pollutants.
Fatigue cracking, also known as alligator cracking, is a network of interconnected fissures created by fatigue failure of the asphalt surface due to repeated traffic pressure. Under a wheel load, tensile stress and strain are highest at the bottom of the asphalt surface (or stable base), when cracking begins. The fractures begin as a succession of parallel cracks that spread to the surface. The fissures unite and generate multi-sided, sharp-angled fragments that develop a pattern resembling chicken wire or alligator skin after repetitive traffic loads. The longest side of the pieces is less than 2 feet (0.6 metres). Only areas susceptible to frequent traffic loadings, such as wheel tracks, experience alligator cracking. As a result, it would not happen over a large area until.
Corner Breaks.Durability Cracking (“D” Cracking)Longitudinal Cracking.Transverse Cracking.
In terms of this principle, through the manual inspection, this study identified 12 major distress types of asphalt pavements.
These distresses may include rutting, shoving, depressions, swelling and patch failures.