A paver (road paver finisher, asphalt finisher, road paving machine) is a piece of construction equipment used to lay asphalt concrete or Portland cement concrete on roads, bridges, parking lots and other such places. It lays the material flat and provides minor compaction. This is typically followed by final compaction by a road roller.
The asphalt paver was developed by Harry Barber of the Barber Greene Co., that originally manufactured material handling systems. In 1929 the Chicago Testing Laboratory approached them to use their material loaders to construct asphalt roads. [1] This did not result in a partnership but Barber did develop a machine based on the concrete pavers of the day that mixed and placed the concrete in a single process. This setup did not prove as effective as desired and the processes were separated and the modern paver was on its way. [2] In 1933 the independent float screed was invented and when combined with the tamper bar provided for uniform material density and thickness. [2] Barber filed for a patent a "Machine for and process of laying roads" on 10 April 1936 and received patent U.S. patent 2,138,828 on 6 December 1938. [3] The main features of the paver developed by the Barber-Greene have been incorporated into most pavers since, although improvements have been made to control of the machine. [1]
The asphalt is added from a dump truck or a material transfer unit into the paver's hopper. The conveyor then carries the asphalt from the hopper to the auger. The auger places a stockpile of material in front of the screed. The screed takes the stockpile of material and spreads it over the width of the road and provides initial compaction. [4]
The paver should provide a smooth uniform surface behind the screed. In order to provide a smooth surface a free floating screed is used. It is towed at the end of a long arm which reduces the base topology effect on the final surface. The height of the screed is controlled by a number of factors including the attack angle of the screed, weight and vibration of the screed, the material head and the towing force. [4]
To conform to the elevation changes for the final grade of the road modern pavers use automatic screed controls, which generally control the screed's angle of attack from information gathered from a grade sensor. Additional controls are used to correct the slope, crown or superelevation of the finished pavement. [5]
In order to provide a smooth surface the paver should proceed at a constant speed and have a consistent stockpile of material in front of the screed. [6] Increase in material stockpile or paver speed will cause the screed to rise resulting in more asphalt being placed therefore a thicker mat of asphalt and an uneven final surface. Alternatively a decrease in material or a drop in speed will cause the screed to fall and the mat to be thinner. [4]
The need for constant speed and material supply is one of the reasons for using a material transfer unit in combination with a paver. A material transfer unit allows for constant material feed to the paver without contact, providing a better end surface. [5] When a dump truck is used to fill the hopper of the paver, it can make contact with the paver or cause it to change speed and affect the screed height.
Large freeways are often paved with Portland cement concrete and this is done using a slipform paver. Trucks dump loads of readymix concrete in heaps along in front of this machine and then the slipform paver spreads the concrete out and levels it off using a screed.
Bitumen is an immensely viscous constituent of petroleum. Depending on its exact composition it can be a sticky, black liquid or an apparently solid mass that behaves as a liquid over very large time scales. In American English, the material is commonly referred to as asphalt. Whether found in natural deposits or refined from petroleum, the substance is classed as a pitch. Prior to the 20th century, the term asphaltum was in general use. The word derives from the Ancient Greek word ἄσφαλτος (ásphaltos), which referred to natural bitumen or pitch. The largest natural deposit of bitumen in the world is the Pitch Lake of southwest Trinidad, which is estimated to contain 10 million tons.
A sidewalk, pavement, footpath in Australia, India, New Zealand and Ireland, or footway is a path along the side of a road. Usually constructed of concrete, pavers, brick, stone, or asphalt, it is designed for pedestrians. A sidewalk is normally higher than the roadway, and separated from it by a curb. There may also be a planted strip between the sidewalk and the roadway and between the roadway and the adjacent land.
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.
Asphalt concrete is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams. Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. It consists of mineral aggregate bound together with bitumen, laid in layers, and compacted.
The free floating screed is a device pioneered in the 1930s that revolutionized the asphalt paving process. The device is designed to spread and smooth out, or screed, the material below it.
A loader is a heavy equipment machine used in construction to move or load materials such as soil, rock, sand, demolition debris, etc. into or onto another type of machinery.
Heavy equipment, heavy machinery, earthmovers, construction vehicles, or construction equipment, refers to heavy-duty vehicles specially designed to execute construction tasks, most frequently involving earthwork operations or other large construction tasks. Heavy equipment usually comprises five equipment systems: the implement, traction, structure, power train, and control/information.
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.
A paver is a paving stone, tile, brick or brick-like piece of concrete commonly used as exterior flooring. They are generally placed on top of a foundation which is made of layers of compacted stone and sand. The pavers are placed in the desired pattern and the space between pavers that is created with the integrated spacer bar is then filled with concrete sand or a polymeric sand. No actual adhesive or retaining method is used other than the weight of the paver itself except edging. Pavers can be used to make roads, driveways, patios, walkways and other outdoor platforms.
A curb or kerb is the edge where a raised sidewalk or road median/central reservation meets a street or other roadway.
Mighty Machines is a Canadian educational children's television series that teaches about machines and how they work and the jobs they do. The show premiered in October 1994 on Family Channel. The show aired 39 episodes over three seasons until 2008.
A heavy equipment operator operates heavy equipment used in engineering and construction projects. Typically only skilled workers may operate heavy equipment, and there is specialized training for learning to use heavy equipment.
Roller-compacted concrete (RCC) or rolled concrete (rollcrete) is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for portland cement. The partial substitution of fly ash for Portland Cement is an important aspect of RCC dam construction because the heat generated by fly ash hydration is significantly less than the heat generated by portland cement hydration. This in turn reduces the thermal loads on the concrete and reduces the potential for thermal cracking to occur. RCC is a mix of cement/fly ash, water, sand, aggregate and common additives, but contains much less water. The produced mix is drier and essentially has no slump. RCC is placed in a manner similar to road paving; the material is delivered by dump trucks or conveyors, spread by small bulldozers or specially modified asphalt pavers, and then compacted by vibratory rollers.
Screed has three meanings in building construction:
Blaw-Knox is a manufacturer of road paving equipment. The company was created in 1917 from the merger of Blaw Collapsible Steel Centering Company and the Knox Pressed and Welded Steel Company. Blaw-Knox was sold to new owners in 1968, changed owners a few times thereafter, and continues as the Volvo Blaw-Knox brand of paving equipment, sold to Volvo Construction Equipment since 2007. Since July 2020 it is owned by Gencor Industries Inc.
A snowmelt system prevents the build-up of snow and ice on cycleways, walkways, patios and roadways, or more economically, only a portion of the area such as a pair of 2-foot (0.61 m)-wide tire tracks on a driveway or a 3-foot (0.91 m) center portion of a sidewalk, etc. It is also used to keep entire driveways and patios snow free in snow prone climates. The "snow melt" system is designed to function during a storm to improve safety and eliminate winter maintenance labor including shoveling, plowing snow and spreading de-icing salt or traction grit (sand). A snowmelt system may extend the life of the concrete, asphalt or under pavers by eliminating the use of salts or other de-icing chemicals, and physical damage from winter service vehicles. Many systems are fully automatic and require no human input to maintain a snow/ice-free horizontal surface.
Soil stabilizers and road recyclers are engineering vehicles that were once similar machines; however, they are now specialised pieces of road making machinery and have developed into different machines. Other terms that are sometimes used are: road profiler, road reclaimer, road miller, road planer and pavement profiler. They are used in the process of full depth recycling.
Barber-Greene Company was a company founded in 1916 by American mechanical engineers Harry H. Barber and William B. Greene. It was formed to sell standardized material-handling machines to mechanize small manual tasks in an economical way. Though the company began by offering conveyors and bucket loaders, it is best known for its contributions to the asphalt field. In 1959, the company went public and was sold to Astec in 1986.
CMI Roadbuilding, Inc. of Oklahoma City began in 1961, when engineers headed by Bill Swisher started looking for new methods in the road building industry. Little had changed since the early 1900s in the methods of building roads, however, labor costs were skyrocketing and inflation meant taxpayers dollars were buying less and less. In the same period Society was becoming increasingly more mobile creating demand for better roads and highways. The CMI group believed that many road failures were due to poor riding surface which was mainly caused by inaccuracies in the subgrade.
Pavement milling is the process of removing at least part of the surface of a paved area such as a road, bridge, or parking lot. Milling removes anywhere from just enough thickness to level and smooth the surface to a full depth removal. There are a number of different reasons for milling a paved area instead of simply repaving over the existing surface.
