ROAD SURFACE /PAVEMENT.
Pavement is durable surface material that is laid down with the intention for sustainability of vehicular or foot traffic, such as walkways or roads. Unlike the past when gravel roads surfaces, curbstone, and granite cell were used extensively that have been replaced by asphalt or concrete raided on a complacent base course.
The acceptable paving method is beginning to be used for low impact roads, walkways. Pavement is also crucial in countries such as the USA which depend heavily on road transportation. Or research project long-term pavement performance has been launched to optimize the life cycle of road surfaces.
Asphalt is also referred to flexible nature, in which it distributes roads. The viscous nature of bitumen allows plastic deformation which provided by asphalt. Most asphalt surfaces are laid on gravel basis that is as thick the asphalt layers though some full depth surfaces are arranged directly on the native subgrades.
Areas with soft all expansive subgrades this is pit, clay, thick gravel bases or stabilization of the subgrades by use of Portland cement or lime is required. In additional asphalt is categorized as war mix or cold mix and also hot mix this depends on the temperature that is applied.
Moreover, to get a better understanding of hot mix asphalt process, it undergoes a temperature of more than 300 degrees Fahrenheit equivalent to 150 degree Celsius with a screed that is freely floating. Additionally, a cold mix asphalt is frequently applied on lower-volume roads that are in rural areas. In this site hot asphalt could cool too much on the long trip from the asphalt plant to the locations of construction
Generally, an asphalt concrete surface will be constructed from high volume primary highways with an average higher than 1200 vehicles per day. Asphalt roadways have several benefits which include relatively low noise, low cost compared to other paving method and easy to repair.
However, asphalt roadways do have several setbacks which provide for less durability as compared to another paving method, lower tensile strength compared to concrete, have a tendency to become slick and soft in hot weather and they have a certain amount of hydrocarbon which may pollute soil and water.
Rubberized asphalt was used for the first time, mixing crumb rubber from used tires with asphalt in the mid of 1960s. By use of tires it provides a potential that would otherwise fill landfills and present a fire hazard, rubberized asphalt has shown major incidents of wear in freeze-thaw cycles in the temperate zone. This may arise because of non- homogenous expansion and contraction with components that are non-rubber.
Application of rubberized asphalt is temperature sensitive and can only be applied at certain times of the year in many places. Results from the study of long-term acoustic benefits of rubberized asphalt are inconclusive. An initial application of rubberized asphalt may provide 3-5 decibels reduction in tire pavement source emissions which however translates to 1-3 decibels in total traffic noise level reduction.
Rubberized asphalt provides shorter lasting and lesser acoustic benefits at the typically much more significant expense as compared to traditional passive attenuating measures.
Concrete surfaces are created using a specific mix of Portland cement, coarse aggregate, sand, and water. All modern combinations will also have various admixtures added to increase workability, reduce the required amount of water, mitigate harmful chemical reactions and for other beneficial purposes. Fly ash may also be added as other Portland cement substitutes which can reduce the cost of the concrete and improve its physical properties.
The material is applied to a freshly mixed slurry and then worked at mechanically to compact the interior and force some of the cement slurries to the surface to produce smoother denser surface free from honeycombing hence the water allowing the mix to combine molecularly in a chemical reaction known as hydration.
There are three common types of concrete surfaces which include, the jointed plan, the jointed reinforced and continuously reinforced. The jointing system used to control crack development is the one item that distinguishes each joint. Concrete pavements do have benefits. One of the significant advantages is that concrete sidewalks are typically stronger and more durable as compared to asphalt roadways.
The other benefits may include: they can be grooved to provide a durable skid resistant surface. In as much as the concrete pavements have various interests, they also do have setbacks which are: they typically can have a higher initial cost and can be more time consuming to construct.
Concrete pavement can also be maintained over time utilizing a series of methods known as real pavement restoration which may include diamond grinding, dowel bar retrofits, joint and crack sealings and cross stitching. Diamond grinding may also be useful in reducing noise and restoring skid resistance in concrete pavements that are older.
Composite pavements consist of a Portland cement concrete sublayer with an asphalt. These concrete pavements are usually used to rehabilitate existing roadways rather than in new construction. To restore as smooth wearing surface asphalt overlays are laid over distressed concrete.
However, this method has some limitations which are reflective cracks in the asphalt which is caused but the movement in the joints between slabs, the underlying concrete, whether from thermal expansion and contraction or it might be from the reflection of concrete slabs. To decrease reflective cracking concrete pavement is broken apart through a break and seat, crack and seat or process of rubberization.
Geosynthetic is a process that can be used to minimize reflective crack. With break and seat and crack and seat processes, heavyweight is dropped on the concrete to induce cracking thereby a heavy roller is used to seat the resultant pieces into sub-base.
The significant differences between the two processes are equipment which is used to break the concrete pavement and the size of the resulting compositions. The theory is small cracks tend to spread thermo stress over a wider area compared to infrequent large joints thus to reduce stress rubberization is a complete fracturing of the old worn out concrete. This effectively converts the old pavement into an aggregated piece for a new asphalt road.