|
Flexible Pavement
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."Highway engineering." McGraw-Hill Concise Encyclopedia of Science and Technology. New York: McGraw-Hill, 2006. Credo Reference. Web. 13 February 2013. Highway engineering became prominent towards the latter half of the 20th century after World War II. Standards of highway engineering are continuously being improved. Highway engineers must take into account future traffic flows, design of highway intersections/interchanges, geometric alignment and design, highway pavement materials and design, structural design of pavement thickness, and pavement maintenance. History The beginning of road construction could be dated to the time of the Romans. With the advancement of technology from carriages pulled by two horses to vehicles with pow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Civil Engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads, bridges, canals, dams, airports, sewage systems, pipelines, structural components of buildings, and railways. Civil engineering is traditionally broken into a number of sub-disciplines. It is considered the second-oldest engineering discipline after military engineering, and it is defined to distinguish non-military engineering from military engineering. Civil engineering can take place in the public sector from municipal public works departments through to federal government agencies, and in the private sector from locally based firms to global Fortune 500 companies. History Civil engineering as a discipline Civil engineering is the application of physical and scientific principles for solving the problems of society, and its history is intricately linked to advances in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asphalt Pavement
A road surface (British English), or pavement (American English), is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, hoggin, cobblestone and granite setts were extensively used, but these have mostly been replaced by asphalt or concrete laid on a compacted base course. Asphalt mixtures have been used in pavement construction since the beginning of the 20th century and are of two types: metalled (hard-surfaced) and unmetalled roads. Metalled roadways are made to sustain vehicular load and so are usually made on frequently used roads. Unmetalled roads, also known as gravel roads, are rough and can sustain less weight. Road surfaces are frequently marked to guide traffic. Today, permeable paving methods are beginning to be used for low-impact roadways and walkways. Pavements are crucial to countries such as United States and Canada, which heavily depend on road transpo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the internal frictional force between adjacent layers of fluid that are in relative motion. For instance, when a viscous fluid is forced through a tube, it flows more quickly near the tube's axis than near its walls. Experiments show that some stress (such as a pressure difference between the two ends of the tube) is needed to sustain the flow. This is because a force is required to overcome the friction between the layers of the fluid which are in relative motion. For a tube with a constant rate of flow, the strength of the compensating force is proportional to the fluid's viscosity. In general, viscosity depends on a fluid's state, such as its temperature, pressure, and rate of deformation. However, the dependence on some of these properties is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asphalt
Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used. Full text at Internet Archive (archive.org) The word is derived from the Ancient Greek ἄσφαλτος ''ásphaltos''. The largest natural deposit of asphalt in the world, estimated to contain 10 million tons, is the Pitch Lake located in La Brea in southwest Trinidad (Antilles island located on the northeastern coast of Venezuela), within the Siparia Regional Corporation. The primary use (70%) of asphalt is in Road surface, road construction, where it is used as the glue or binder mixed with construction aggregate, aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs. In material sciences an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Road Surface
A road surface (British English), or pavement (American English), is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, hoggin, cobblestone and granite setts were extensively used, but these have mostly been replaced by asphalt or concrete laid on a compacted base course. Asphalt mixtures have been used in pavement construction since the beginning of the 20th century and are of two types: metalled (hard-surfaced) and unmetalled roads. Metalled roadways are made to sustain vehicular load and so are usually made on frequently used roads. Unmetalled roads, also known as gravel roads, are rough and can sustain less weight. Road surfaces are frequently marked to guide traffic. Today, permeable paving methods are beginning to be used for low-impact roadways and walkways. Pavements are crucial to countries such as United States and Canada, which heavily depend on road transpor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Course
The base course or basecourse in pavements is a layer of material in an asphalt roadway, race track, riding arena, or sporting field. It is located under the surface layer consisting of the ''wearing course'' and sometimes an extra ''binder course''. If there is a sub-base course, the base course is constructed directly above this layer. Otherwise, it is built directly on top of the subgrade. Typical base course thickness ranges from and is governed by underlying layer properties. Generally consisting of a specific type of construction aggregate, it is placed by means of attentive spreading and compacting to a minimum of 95% relative compaction, thus providing the stable foundation needed to support either additional layers of aggregates or the placement of an asphalt concrete wearing course which is applied directly on top of the base course. Aggregate base (AB) is typically made of a recipe of mixing different sizes of crushed rock together forming the aggregate which has cer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer Soil Stabilization
Polymer soil stabilization refers to the addition of polymers to improve the physical properties of soils, most often for geotechnical engineering, construction, or agricultural projects. Even at very small concentrations within soils, various polymers have been shown to increase water retention and reduce erosion, increase soil shear strength, and support soil structure. A wide range of polymers have been used to address problems ranging from the prevention of desertification to the reinforcement of roadbeds. Polymers that have been tested for soil stabilization effects include a range of synthetic polymers and biopolymers. Biopolymers in particular offer a more eco-friendly alternative to traditional chemical additives, such as ordinary cement, which may generate a large amount of carbon dioxide during production or cause lasting environmental damage. Polymers mainly affect the aggregation and strength of soils through their interactions with fine clay particles. Coatings of ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subbase (pavement)
In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles. Subbase is often the main load-bearing layer of the pavement. Its role is to spread the load evenly over the subgrade. The materials used may be either unbound granular, or cement-bound. The quality of subbase is very important for the useful life of the road and can outlive the life of the surface, which can be scraped off and, after checking that the subbase is still in good condition, a new layer can be applied. Unbound granular materials are usually crushed stone, crushed slag or concrete, or slate. Cement-bound materials come in multiple types. Mass concrete is used where exceptional loads are expected, with thickness usually , and optional reinforcement with steel mesh or polymer fibers. Other cement bound materials (CBM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erosion Control
Erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development, coastal areas, river banks and construction. Effective erosion controls handle surface runoff and are important techniques in preventing water pollution, soil loss, wildlife habitat loss and human property loss. Usage Erosion controls are used in natural areas, agricultural settings or urban environments. In urban areas erosion controls are often part of stormwater runoff management programs required by local governments. The controls often involve the creation of a physical barrier, such as vegetation or rock, to absorb some of the energy of the wind or water that is causing the erosion. They also involve building and maintaining storm drains. On construction sites they are often implemented in conjunction with sediment controls such as sediment basins and silt fences. Bank erosion is a natural process: without it, rivers would not meander and change course. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drainage
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic conditions that harm root growth), but many soils need artificial drainage to improve production or to manage water supplies. History Early history The Indus Valley civilization had sewerage and drainage systems. All houses in the major cities of Harappa and Mohenjo-daro had access to water and drainage facilities. Waste water was directed to covered gravity sewers, which lined the major streets. 18th and 19th century The invention of hollow-pipe drainage is credited to Sir Hugh Dalrymple, who died in 1753. Current practices Geotextiles New storm water drainage systems incorporate geotextile filters that retain and prevent fine grains of soil from passing into and clogging the drain. Geotextiles are synthetic textile fabrics specially ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concrete
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $600 billion in revenue by 2025. This widespread use results in a number of environmental impacts. Most notably, the production process for cement produces large volumes of greenhouse gas emissions, leading to net 8% of global emissions. Other environmental concerns include widespread illegal sand mining, impacts on the surrounding environment such as increased surface runoff or urban heat island effect, and potential public health implications from toxic ingredients. Significant research and development is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
