Road Cracks and Damages
In designing a road, the aspect of durability is normally considered. Most of the roads are made to last for more than 20 years but in most cases, cracks and damages occur before the end of the expected span. Road crack and damages are common phenomena along most of the roads and pavements. However, during the construction, the contractors intend to make roads free of crack. They consider the ratio of mixing the construction materials carefully, but at the end, the roads end up having some cracks and damages after a certain duration. These crack and damages usually become safety hazards that can lead to road accidents and damage the vehicles. There are many reasons that usually cause such unfortunate occurrences. Some causes are environmental, climatic, traffic loading and sometimes poor construction.
Cracks and Damages
They are also known as alligator or fatigue cracks. They are normally interconnecting cracking in the top layer of asphalt resembling crocodile hide, as indicated in the above photo. They usually occur due to poor drainage, brittle base, low modulus base, sub-base failure, and high pressure due to overloading.
These are cracks that form bigger blocks than those of crocodile cracks. This is caused by weak joints on the underlaying layer, shrinkage cracks on the bitumen surface, fatigue cracks formed in the bitumen course, and also shrinkage and fatigue found in the underlaying cement material.
They are elongated cracks along the roads or pavements as shown in the picture above. They normally occur because of poor paving lane construction in the bituminous surface. In addition, displacement of joints at the windings of pavement and differential settlement aligning between the cut and fill causes longitudinal cracks.
This is the disintegration of physical chipping or scaling wearing the top surface. It is either caused by moisture or thermal stress. In some cases, it is poor construction or poor materials mixing like using excess water and surface overworking. Normally, it brings roughness and shortens the lifespan intended for the road.
It is normally caused by dragging off a paver during the actual laying when the bitumen mix temperatures are low. Moreover, high stress on the roads and pavements due to braking and accelerating vehicles causes shoving. This sometimes leads to a thin wearing occurring frequently on course. Such damages occur on a module base course which is low.
Causes of Road Cracks and Damages
One of the main causes of road cracks and damages is traffic loading. Usually, the vehicles have varying weight. Heavy vehicles like trucks and Lorries project great pressure to the roads. Depending on the strength that the road has to overcome such pressure, damages may occur. If the pressure on the road or pavement is too high, the damages and cracks occur. Normally, up and down movement caused by vehicle subjects the roads and pavements to some vibrations that lead to cracks and damages. Long-term pavements, which are made by increasing the thickness of asphalt should be put in place. This kind of pavements tend to overcome high pressure without incurring cracks.
Another cause of road cracks and damages is varying climatic conditions. Normally, in arid and semi-arid zone, there are huge temperature differences. The temperatures are normally too high during the day and too low at night. When the temperatures are high, the soil generally expands due to heating. As the soil elements enlarge, spaces are created connecting the particles. When the temperatures fall at night, the soil particles contact causing cracks in the spaces that had been created by expansion. This alternating temperature variation causes widening of the cracks. Normally, asphalt pavements are most preferable in such zone compared to rigid concrete pavements because they are flexible, and have some tolerance to displacement. Rigid pavements are prone to cracks in such zones. Roads are designed to last for certain duration of time. Aging is also a factor that may lead to road damages. Immediately the hot tarmac is put down and begins to cool, the aging factor comes in. The materials used for construction becomes weak when the time intended for them to work well expires. Therefore, cohesive and adhesive force that causes particles to attract one another is weakened, and the particles are made to split. Heat also increases the speed of deterioration. This splitting of particles becomes crack.
Poor drainage on the roads and pavement can lead to cracking. Crocodile cracking is also caused by poor drainage on the pavements. When the pavement is subject to high moisture content for a long period of time, it tends to break up and loosen the particles. How penetrated water causes cracks can be explained in simplier terms. When the water finds its way underneath the asphalt, it settles in tiny voids between the base of the road and asphalt layer. When heavy trucks drive along the road, they render high pressure that pushes the accumulated water downwards. As the water goes, further down it displaces some soil particles or dirt. This creates pockets underneath the roads or pavements. The air and water pockets created eventually lead to bulging of the pavements, which matures to cracks.
Prevention of Cracks and Damages
Poor designs and construction renders the road vulnerable to cracks and damages. The quality assurance body that monitors the standards of roads and highways should put strict and punitive measures to contractors who fail to meet the expected standards.
Since poor drainage on the roads and pavements leads to cracking, it is important to ensure that proper drainage system is maintained. This can be done by ensuring the pavements and roads are constructed with a certain inclination to ensure that no water accumulate on the pavement. The underground drainage system should be put in place to ensure that water flows preventing any kind of water logging. Water drainage channels should be made along the roads to ensure that the pavements or the roads are always kept dry. Storm sewers are also necessary for clearing rainwater.
When the affected area is small, it can be repaired by scooping the affected area and replacing it with new asphalt surface. Sometimes, sealing the cracks may be necessary. This is done using crack sealant. If the affected area is extensive, a complete reconstruction may be the most appropriate method in order to ensure a firm layout.
The most effective treatment for these cracks are strengthening the pavements or reconstructing it in zones with inadequate thickness of the pavement. In addition, strengthening the base or reconstructing should be done on low modulus base. The drainage should be improved or reconstructed where there is poor drainage system. Nevertheless, brittle wearing course the can be treated or replaced by using fog seal, slurry seal or armor coat.
These can be treated by cutting and patching zones with shrinkage cracks, or replacing the bituminous surfacing on poor paving construction. In addition, it can be treated by reconstruction of joins in an area with joint displacements at the pavement widening. Crushed aggregate overlay is necessary in areas with differential settlements occurring between cut and fill. These are treatments that are made in order to remove longitudinal.
The treatment for shoving includes removing the surface and base where necessary and replacing it with a more stable material. Reconstruction of base is necessary in cases of low modulus base. In cases where shoving has occurred due to high pressure exerted on the pavement by accelerating vehicles it is advisable to overlay bitumen with a stiffer mix or using mix of high compaction.
Maintenance and Rehabilitation Plans
Construction deficiency leads to cracks on the road. Usually, materials are supposed to be mixed at certain ratios considering the required procedures and conditions. Asphalt is heated and laid when it is hot. As it cools down, a firm and solid layer is formed due to the chemical processes involved. Failure to follow the required procedure may lead to crack after the asphalt has just cooled down. This may cause pealing of layers.
Road monitoring systems should be put in place to ensure that overloading does not take place on asphalt pavements. Very heavy commercial vehicles damage most of the roads. It is appropriate to have specific road channels for the heavy vehicles that are designed to overcome high pressure. Tractors and fight tanks should not be allowed to move on pavements and roads since the cause physical damage on the roads and pavements.
Local and International Comparison
In different countries, different techniques are used to deal with cracks and damages. Actually, different places are vulnerable to different cracks and damages depending on transportation policy, environment, and climatic conditions. Zones that fall near the pole zones are mostly affected by water seepage in the soil while zones that are found near deserts are affected by a wide range of varying temperature. Some zones in the United States of America like Alaska are prone to ice formation. When the ice melts, it causes moisture penetration in the roads and pavements. This penetration normally interferes with the structure of the asphalt, leading to Cracks.
Different countries have different construction techniques. The ratio of mixing the construction materials also varies widely. In Autobahn road in German, a very thick layer is applied on a strong solid foundation. This curbs cracking and reduces the cost of maintenance.
In Africa, the place near Sahara desert as Chad is normally subject to high temperatures during the day and very low temperatures at night. Therefore, the rocks and the soil expand and contract often. This leads to cracking due to varying temperature conditions.
In order to work on the damages and cracks, it is important to conduct a survey to establish the figures of the areas that need to be attended. Prevention mostly depends on the plan and construction of the transport roads. It is also crucial to establish the reason of cracking before repairing the road or the pavement.