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Concrete is a composite material composed of aggregate bonded together with a fluid cement that 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 aluminium combined.
A road is a thoroughfare for the conveyance of traffic that mostly has an improved surface for use by vehicles and pedestrians. Unlike streets, whose primary function is to serve as public spaces, the main function of roads is transportation.
Highway engineering is a professional engineering discipline branching from the civil engineering subdiscipline of transportation engineering that involves the planning, design, construction, operation, and maintenance of roads, highways, streets, bridges, and tunnels to ensure safe and effective transportation of people and goods. 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.
A road surface or pavement 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past, gravel road surfaces, macadam, hoggin, cobblestone and granite setts were extensively used, but these have mostly been replaced by asphalt or concrete laid on a compacted base course.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 or dirt roads, are rough and can sustain less weight. Road surfaces are frequently marked to guide traffic.
A thermographic camera is a device that creates an image using infrared (IR) radiation, similar to a normal camera that forms an image using visible light. Instead of the 400–700 nanometre (nm) range of the visible light camera, infrared cameras are sensitive to wavelengths from about 1,000 nm to about 14,000 nm (14 μm). The practice of capturing and analyzing the data they provide is called thermography.
Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared imaging science. Thermographic cameras usually detect radiation in the long-infrared range of the electromagnetic spectrum and produce images of that radiation, called thermograms. Since infrared radiation is emitted by all objects with a temperature above absolute zero according to the black body radiation law, thermography makes it possible to see one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature; therefore, thermography allows one to see variations in temperature. When viewed through a thermal imaging camera, warm objects stand out well against cooler backgrounds; humans and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography is particularly useful to the military and other users of surveillance cameras.
Permeable paving surfaces are made of either a porous material that enables stormwater to flow through it or nonporous blocks spaced so that water can flow between the gaps. Permeable paving can also include a variety of surfacing techniques for roads, parking lots, and pedestrian walkways. Permeable pavement surfaces may be composed of; pervious concrete, porous asphalt, paving stones, or interlocking pavers. Unlike traditional impervious paving materials such as concrete and asphalt, permeable paving systems allow stormwater to percolate and infiltrate through the pavement and into the aggregate layers and/or soil below. In addition to reducing surface runoff, permeable paving systems can trap suspended solids, thereby filtering pollutants from stormwater.
Delamination is a mode of failure where a material fractures into layers. A variety of materials, including laminate composites and concrete, can fail by delamination. Processing can create layers in materials, such as steel formed by rolling and plastics and metals from 3D printing which can fail from layer separation. Also, surface coatings, such as paints and films, can delaminate from the coated substrate.
Acoustic emission (AE) is the phenomenon of radiation of acoustic (elastic) waves in solids that occurs when a material undergoes irreversible changes in its internal structure, for example as a result of crack formation or plastic deformation due to aging, temperature gradients, or external mechanical forces.
A dowel bar retrofit (DBR) is a method of reinforcing cracks in highway pavement by inserting steel dowel bars in slots cut across the cracks. It is a technique which several U.S. states' departments of transportation have successfully used in repairs to address faulting in older jointed plain concrete pavements. The typical approach is to saw cut and jackhammer out the slots for the dowels. Following dowel placement the slots are then typically backfilled with a non-shrink concrete mixture, and the pavement is diamond-ground to restore smoothness.
A thermal bridge, also called a cold bridge, heat bridge, or thermal bypass, is an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer. Thermal bridges result in an overall reduction in thermal resistance of the object. The term is frequently discussed in the context of a building's thermal envelope where thermal bridges result in heat transfer into or out of conditioned space.
Thermographic inspection refers to the nondestructive testing (NDT) of parts, materials or systems through the imaging of the temperature fields, gradients and/or patterns ("thermograms") at the object's surface. It is distinguished from medical thermography by the subjects being examined: thermographic inspection generally examines inanimate objects, while medical thermography generally examines living organisms. Generally, thermographic inspection is performed using an infrared sensor.
Infrared vision is the capability of biological or artificial systems to detect infrared radiation. The terms thermal vision and thermal imaging, are also commonly used in this context since infrared emissions from a body are directly related to their temperature: hotter objects emit more energy in the infrared spectrum than colder ones.
Cellular confinement systems (CCS)—also known as geocells—are widely used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth retention. Typical cellular confinement systems are geosynthetics made with ultrasonically welded high-density polyethylene (HDPE) strips or novel polymeric alloy (NPA)—and expanded on-site to form a honeycomb-like structure—and filled with sand, soil, rock, gravel or concrete.
Infrared and thermal testing refer to passive thermographic inspection techniques, a class of nondestructive testing designated by the American Society for Nondestructive Testing (ASNT). Infrared thermography is the science of measuring and mapping surface temperatures.
"Infrared thermography, a nondestructive, remote sensing technique, has proved to be an effective, convenient, and economical method of testing concrete. It can detect internal voids, delaminations, and cracks in concrete structures such as bridge decks, highway pavements, garage floors, parking lot pavements, and building walls. As a testing technique, some of its most important qualities are that (1) it is accurate; (2) it is repeatable; (3) it need not inconvenience the public; and (4) it is economical."
Concrete has relatively high compressive strength, but significantly lower tensile strength. The compressive strength is typically controlled with the ratio of water to cement when forming the concrete, and tensile strength is increased by additives, typically steel, to create reinforced concrete. In other words we can say concrete is made up of sand, ballast, cement and water.
Terahertz nondestructive evaluation pertains to devices, and techniques of analysis occurring in the terahertz domain of electromagnetic radiation. These devices and techniques evaluate the properties of a material, component or system without causing damage.
Carbon fiber testing is a set of various different tests that researchers use to characterize the properties of carbon fiber. The results for the testing are used to aid the manufacturer and developers decisions selecting and designing material composites, manufacturing processes and for ensured safety and integrity. Safety-critical carbon fiber components, such as structural parts in machines, vehicles, aircraft or architectural elements are subject to testing.
Active thermography is an advanced nondestructive testing procedure, which uses a thermography measurement of a tested material thermal response after its external excitation. This principle can be used also for non-contact infrared non-destructive testing (IRNDT) of materials.
Welding of advanced thermoplastic composites is a beneficial method of joining these materials compared to mechanical fastening and adhesive bonding. Mechanical fastening requires intense labor, and creates stress concentrations, while adhesive bonding requires extensive surface preparation, and long curing cycles. Welding these materials is a cost-effective method of joining concerning preparation and execution, and these materials retain their properties upon cooling, so no post processing is necessary. These materials are widely used in the aerospace industry to reduce weight of a part while keeping strength.
References
- ↑ Kirk, Robert S.; Mallett, William J. (January 17, 2018). Highway Bridge Conditions: Issues for Congress (PDF). Washington, DC: Congressional Research Service. Retrieved 27 January 2018.
- ↑ Weil, Gary J. “Nondestructive Testing of Large Concrete Structures.” SPIE 3397 (1998).
- ↑ Weil, Gary J. Non Destructive Testing of Bridge, Highway and Airport Pavements, Gateway Engineer Magazine, 1992, pages 5-7
- Weil, Gary J. “Nondestructive Testing of Large Concrete Structures.” SPIE 3397 (1998).
- Weil, Gary J. "Non Destructive Testing of Bridge, Highway and Airport Pavements", Gateway Engineer Magazine, 1992, pages 5-7
- Weil, Gary J. "Toward an Integrated Nondestructive Pavement Testing Management Information System Using Infrared Thermography," Proceedings of the U.S. Transportation Research Board, Washington D.C., June 22, 1989
- Weil, Gary J. "Detecting the Defects", Civil Engineering Magazine, American Society of Civil Engineering, Volume 59, Number 9, 1989, pages 74-77