Transportation affects everyone on earth on a daily basis , People, countries, governments, business, whole economy rely on effective, reliable transportation in one form or another.
The understanding, learning, and application of highway engineering is essential for a sustainable economy and ease of life, highway engineering is defined as : “Highway engineering is an engineering discipline branching from civil engineering that involves the planning, design, construction, operation, and maintenance of roads, bridges, and tunnels to ensure safe and effective transportation of people and goods.”1
Roads are one of many modes of transportation and are the most important one, because roads are the facilities that allow people to move, companies to supply goods thus a functional economy. The road surface or Pavement is the surface of which a material would sustain moving loads such as vehicles or pedestrians.
In the past roads were paved from bricks and masonry which we can still see now in many places like Rome, nowadays most of our roads are paved with asphalt or concrete , which are called Flexible pavement and rigid pavement respectively.
These pavements withstand and resist huge amount of loads each day, some major highways have a traffic volume of 500,000 AADT, thus the analysis, design, and maintenance of these roads is essential, and must be safe and economical.
Typically a flexible pavement consists of four layers : subgrade, subbase, base, surface ; and usually flexible pavements are constructed of Hot Mix Asphalt (HMA) , in these types of pavements , high stresses happen on the surface of the pavement and decreases with the depth, usually designed for a period of 20-30 years
While rigid pavements are not that commonly used , they are used for constructing airports , seaports and some major highways; rigid pavements are most commonly constructed with Portland cement concrete because of the low cost , and higher lifespan, rigid pavements can reach double the design period of a flexible pavement.
As pavements age and experience traffic repetitions, pavement distresses begin to accumulate. Also distresses can compound themselves; for example, a crack can allow water to enter the pavement and lead to the development of a pothole or stripping. So it is important to perform timely maintenance. In this research we will showcase some types of rigid pavement distresses
(A FRAMEWORK FOR INCORPORATION OF SPALLING IN THE DESIGN OF CONCRETE PAVEMENTS)
Sanjaya P. Senadheera and Dan G. Zollinger
“Spalling, which is an often encountered form of distress in concrete pavements has
not received the same attention in pavement design as the other distresses such as
cracking and punch-outs in continuously reinforced concrete pavements (CRCP) and
joint failure in jointed concrete pavements (JCP). It is a very important distress in
concrete pavements form the standpoint of the road user because it results in a rough
ride and gives a negative perception of lack of structural integrity in the pavement.
From a technical standpoint, since spalling takes place at the transverse joints or random
cracks in the pavement, it may take away from the load transfer efficiency which is
important to minimize stress levels in the pavement. Unless adequate load transfer is
maintained, spalls may develop into more serious forms of distress such as punch-outs in
CRCP, or joint failure in JCP.
The lack of attention given to the spalling distress on a fundamental basis may
have been due to a lack of understanding of the mechanisms involved. At Texas
Transportation Institute (TTI) of the Texas A & M University System, research is
currently underway to identify the mechanisms of spalling which would enable the
modelling of spalling in concrete pavements by incorporating a number of factors that
appear to significantly influence spalling.”
(Analysis of Concrete Pavement Blowups)
By A. D. Kerr, Newark, Delaware, and P. J. Shade,
:Florham Park, New Jersey (Received August 15, 1983; revised November 28, 1983)
“Concrete pavement blowups are caused by axial compression forces induced into the
pavement by a rise in temperature and moisture. Although many papers and reports were
published on this subject, research in this area has not resulted in an understanding of the
blowup mechanism and the derivation of a generally accepted analysis.
Recently, A. D. Kerr and W. A. Dallis, Jr., presented an analysis based on the assumption
that blowups are caused by lift-off buckling of the pavement, due to a rise in pavement
temperature and moisture. In their analysis the nonlinear axial resistance between pavement
and base was represented by a bilinear approximation. In the present paper this assumption
is dropped, and a nonhnear expression is used instead. Although the resulting formulation
is nonlinear (geometrical nonlinearity in the lift-off region and material nonlinearity in the
adjoining regions) it was possible to solve it exactly and in closed form. The solutions
yield the post-buckling displacements and the corresponding axial forces.
A “safe range” of temperature and moisture increases was defined and it is shown,
using the obtained solutions, how this range is affected by the thickness of pavement, the
axial shearing resistance at the interface of pavement and base, and other pavement parameters.
The presented results should contribute to a better understanding of the mechanics of
pavement blowups and the determination of the essential parameters. It also provides
guidelines for prescribing measures to reduce or totally eliminate blowups in concrete
CAUSES OF PAVEMENT DETERIORATION
Pavement Deterioration and its Causes
(Civil,J.J.Magdum college for Engineering/ Shivaji University,India)
“(i)Sudden increase in traffic loading especially on new roads where the design is based on lesser traffic is a major cause of cracking. After construction of good road, traffic of other roads also shifts to that road. This accelerates the fatigue failure (Alligator Cracking).
(ii)Temperature variation ranging from 50º C to below zero conditions in the plain areas of North and Central India leads to bleeding and cracking.
(iii) Provision of poor shoulders leads to edge failures.
(iv) Provision of poor clayey subgrade results in corrugation at the surface and increase in unevenness.
(v) Poor drainage conditions especially during rainy seasons, force the water to enter the pavement from the sides as well as from the top surface. In case of open graded bituminous layer, this phenomenon becomes more dangerous and the top layer gets detached from the lower layers.
(vi) If the temperature of bitumen/bituminous mixes is not maintained properly, then it also leads to pavement failure. Over heating of bitumen reduces the binding property of bitumen. If the temperature of bituminous mix has been lowered down then the compaction will not be proper leading to longitudinal corrugations.”
“D-Cracking of Concrete Pavements,”
Prepared by Donald Schwartz as
NCHRP Synthesis 134
” Concrete pavement D cracking is a terminal condition. Once it starts, there’s no known cure. The cause is known—coarse aggregates susceptible to freezing and thawing deterioration.
But the only way to prevent D-cracking is to avoid using these aggregates in concrete pavements. Even that isn’t as simple as it sounds. How do you identify susceptible aggregates? And what do you do when the only economically available aggregates in the area cause D-cracking?
Some of the answers are in a just published report from the National Cooperative Highway Research Program. It explores the causes and potential ways of avoiding or treating D – cracking distress.
Causes and symptoms Aggregates that cause D-cracking absorb moisture from the pavement base and from surface water entering through cracks and joints. If aggregate pores are full when freezing occurs, internal pore pressure c racks the particles causing the mortar to crack as well. More cracks develop with repeated freezing and thawing cycles.
The cracks usually begin in the lower portion of the slab and move upward, but they may also start at the top or in the interior. They always start along cracks, joints, or free edges. Eventually a pattern of cracks forms at the pavement we a ring surface.
This pattern appears as a series of closely spaced fine cracks. These cracks are generally adjacent and parallel to joints and cracks and to the free edges of the pavement slab.”
I- Blowup : is a Localized upward movement of the pavement surface at transverse joints or cracks, often accompanied by shattering of the concrete in that area2FHWA
As mentioned above in the literature review, “Concrete pavement blowups are caused by axial compression forces induced into the pavement by a rise in temperature and moisture”
the main source for blowup distress is thermal conditions, during winter season concrete slabs tend to shrink thus leaving openings to be filled with soil, rocks or any incompressible material, and when the summer season arrives the slab will expand which will result that the pressure builds up until the slab cannot resist it any longer and they either buckle or shatter, crumbling along the transverse joint or crack.3 Airfiekd
Blowups may be repaired using the following procedures:4airf
“a. Make a full-depth vertical cut with a concrete saw approximately 6 inches (15 cm) outside of each end of the broken area.
b. Break out the concrete with pneumatic tools, and remove concrete down to the subbase/subgradematerial.
c. Add subbase material, if necessary, and compact.
d. In reinforced pavement construction, use joint techniques to tie the new concrete to the old reinforced material. Dowel any replacement joints, and build them to joint specifications.
e. Dampen the subgrade and the edges of the old grout.
f. Place concrete on the area to be patched. Ready-mixed concrete may be used if it is satisfactory and can be obtained economically. Consider using a mixture providing high early strength in order to permit the earliest possible use.
g. Finish the concrete so the surface texture approximates that of the existing pavement.145
h. Immediately after completing finishing operations, properly cure the surface with either a cure or a curing compound.”
The cost for full-depth repairs on jointed concrete pavements varies significantly, depending on the locality and site conditions (e.g., traffic). Typical recent costs in 2000 for 1.8 m (6 ft) repairs on a 250-mm(10 in) slab range from $60/m2 to $120/m2 ($50/yd2 to $100/yd2, with many falling between $78/m2 and $84/m2($65/yd2 and $80/yd2 ). Repair costs for CRCP are significantly higher.5 https://www.fhwa.dot.gov/pavement/concrete/full6.cfm
II- Spalling : Cracking, breaking or chipping of joint/crack edges. Usually occurs within about 0.6 m (2 ft.) of joint/crack edge.6 http://www.pavementinteractive.org/spalling/
Water expands about 9% of its size when it freezes and when there is no place for that water to go when it freezes it is going to cause internal stresses in the concrete, which mainly causes spalled concrete.
Porosity of concrete is the reason behind water presence in concrete which indicates weak concrete due the voids it contains , these voids can be filled with water during winter and if the droplets of water doesn’t have a place to escape its imminent to freeze under low temperatures and thus expanding and causing stresses.
Joints spalling result from: 7airf
– excessive stress at the joint
– infiltration of incompressible materials
– traffic load
– weak concrete at the joint (cause by over working) combined with traffic loads is another cause of spalling.
Partial-depth repair is typically used to repair spalling either at joints or at mid-slab locations. The purpose of partial-depth repair for the PCC pavement is to correct localized areas of concrete pavement distress. Repair of this type restores ride ability, deters further deterioration, reduces foreign object damage potential, and provides proper edges so that joints can be effectively resealed.
The procedure for the repair of spalls is as follows:
” a. Make a vertical cut with a concrete saw 2 inches (5 cm) in depth and approximately 2 inches (5 cm) back of the spalled area.
b. Remove all unsound concrete until sound, intact material has been reached. Break out the unsound concrete with air hammers or pneumatic drills and blow out the area with compressed air.
c. Clean the area to be repaired with high-pressure water. Allow patch area to dry completely if required by the patch material specification.
d. Treat the surface with a grout mixture to ensure a good bond between the existing pavement and the new concrete. Apply the grout immediately before placing the patch mixture and spread with a stiff broom or brush to a depth of 1/16 inch (2 mm). 144
e. Place a thin strip of wood or metal coated with bond-breaking material in the joint groove and tarp the new mixture into the old surface. The mix should be air-entrained and designed to produce a no slump concrete, which will require tamping to place in the patch.
f. After edging the patch, finish it to a texture matching the adjacent area.
g. After a proper cure period, fill the open joint with joint sealant prior to opening to traffic.”8air
Estimate for concrete work: $3-5 per square foot.
Estimate for brickwork: $0.35-$0.75 per brick 9 https://www.homeadvisor.com/cost/garages/repair-a-driveway/#spalling
Pumping is defined as the ejection of material by water through joints or cracks caused by deflection of the slab under passing loads PAVER™ DISTRESS IDENTIFICATION MANUAL DEVELOPED BY: US ARMY CORPS OF ENGINEERS ERDC-CERL
seeping of water and subgrade material from beneath the pavement through the cracks under heavy loads is caused by pumping. And sometimes deposits of fine material lifter by water are left on the surface.
The deflection of the slab when loaded may cause pumping. As the water is ejected, it carries fine particles with it, resulting in a loss of pavement support that can lead to cracking.
Evidence of pumping includes surface staining and base or subgrade material on the pavement close to joints or cracks. Pumping near joints indicates poor joint-load transfer, a poor joint seal, and/or the presence of ground water.