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Otta seal is a type of bituminous surface treatment that was developed by the Norwegian Road Research Laboratory (NRRL). Its name is based on the location in which it was created, the Otta Valley. Otta seal was developed to be used as a temporary surfacing on new roads; however, after seeing its strength, it has been used as permanent roads as well. [1]
Otta seal is formed by adding graded aggregate to a soft bituminous binding agent. The agent is usually emulsified asphalt. Bituminous binder application rates are between 1.9 liter/m2 (0.42 US gallon/yard2) and 2.4 liter/m2 (0.53 US gallon/yard2) – the value is dependent on aggregate gradation and type. Low quality, local aggregates are often used in Otta seal. The largest aggregate size used is between 13 and 25mm (0.5 and 1 inch). The aggregate can contain up to 10% fine gravels. Aggregate quantities are usually close to 27 kg/m2 (50 lbs/yard2). Otta seal is easily cured by blinding with sand because of its soft binders. The soft binders quickly coat the sand; this is not possible for seals with harder binders. Cutback bitumens in the viscosity range of MC3000 to MC800 are the most common binders used. [1] [2]
Otta seal is formed in the following procedure:
Otta seal is primarily used in places that do not have strict requirements for strength, grading, particle shape, binder adhesion, and dust content, which have low capital and expect relatively low traffic (up to 500 vehicles per day). [1] [3] Currently, Otta seal is most prevalent in Norway, Sweden, Iceland, and Botswana and common in Bangladesh, Australia, and parts of Africa.
Politically Otta seal is a useful alternative versus other types of road surfaces. A city council member of a city that uses Otta seal explained that it is very cost efficient since with Otta seal they can resurface a road every 5–10 years without having to tear the whole road up every time it needs to be resurfaced. This lengthens the road life and makes it very economical.[ citation needed ]
Otta seal does not cause prolonged delays in traffic, it takes few hours to resurface a road and is usable almost immediately afterwards. Since this is mainly used on side roads it is important that it is done quickly to prevent people from not being able to get to their houses. One negative impact is the loose gravel can cause chips or damage to windshields, but odds of this happening is lowered in slower moving traffic areas.[ citation needed ]
Environmentally, Otta seal helps to lower the dust level. This helps the environment in many ways; helps with driving visibility, decrease health problems caused by dust, and reduce harm done to crops. Another environmental benefit is that the materials used in its production are easily acceptable. There is also a reduction in environmental degradation. [1]
Otta seal is considered to be a low cost seal. With its low initial cost and less demanding maintenance, it is a very cheap alternative for road surfaces. The cost for a double layer Otta seal is about US $2.00 to US $2.70 per square meter (US $2.40 to US $3.25 per square yard) and will last from 8 to 15 years. For a road that is 1.6 km (1 mile) long and 12 m (40 feet) wide it would cost between US $39,000 to US $52,000. [4]
Otta seal is a type of road surfacing consisting of a bituminous binding substance and aggregate rocks ranging from gravel to fine particles. It is stronger than similar inexpensive surfacing techniques such as chip seal.
The type of bitumen used can greatly affect the strength of the road. Bitumen binders that are more viscous tend to move through the aggregate faster, but are not as hard and cannot handle heavier loads.
A huge advantage of Otta seal over other seals is the ability to use almost any type or size of crushed rocks as the aggregate. Depending on where in the world the road is being constructed and therefore what types of rock are available, the strength of an Otta seal can vary greatly. Commonly, the gravel used contains sandstone, basalt, and even coral or volcanic stones. Also, size of the particles varies greatly, with a preferred maximum of 16 mm and 19 mm (0.63 inch and 0.75 inch) for single and double Otta seals, respectively. Typically, the concentration of fine particles of less than 0.075 mm (0.003 inch) should be less than 10%.
Adhesive agents are generally added to increase the strength between the aggregate and the bituminous binder. It is this interaction that gives Otta seal its strength and durability. [1] [5]
Since Otta seal is a combination of materials, it is beneficial to look at the molecular structures of the materials used.
Rocks are in the material family of ceramics. They have very rigid crystalline structures that stand up well to compressive forces. In contrast, sheer or tensile forces can easily form cracks in ceramics and cause failure. The bitumen acts the opposite way. It is more amorphous, meaning it is weaker under compressive forces, but can hold the rocks together and limit cracking under tensile stress.
The bitumen molecular structure is composed mostly of compressed hydrocarbons, sometimes containing many other elements like nitrogen, oxygen, sulfur, and nickel. [6]
There are many factors when considering what type of road surfacing is necessary. [7] Most advantages to Otta seal over other inexpensive surfacing techniques spring from its ability to use a wide range of materials and material sizes during construction. Pros and cons are listed here:
Otta seal is more durable than many alternative seals. It is impermeable and resistant to cracking from the sun’s radiation. Cracks form in all roads due to changes in temperature, but Otta seal performs better than other seals. Overall, Otta seal can be expected to last 50 to 60 percent longer than a chip seal. This results in a lifespan between 6 and 12 years if properly maintained, and even longer if a sand seal is used on top of the Otta seal.
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 the U.S., 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 ἄσφαλτος ásphaltos, which referred to natural bitumen or pitch. The largest natural deposit of bitumen in the world, estimated to contain 10 million tons, is the Pitch Lake of southwest Trinidad.
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.
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th century by Joseph Aspdin, and is usually made from limestone. It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum. Several types of portland cement are available. The most common, called ordinary portland cement (OPC), is grey, but white portland cement is also available. Its name is derived from its resemblance to portland stone which was quarried on the Isle of Portland in Dorset, England. It was named by Joseph Aspdin who obtained a patent for it in 1824. His son William Aspdin is regarded as the inventor of "modern" portland cement due to his developments in the 1840s. The term portland in this context refers to a material or process, not a proper noun like a place or a person, and should not be capitalized.
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, 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.
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 pothole is a depression in a road surface, usually asphalt pavement, where traffic has removed broken pieces of the pavement. It is usually the result of water in the underlying soil structure and traffic passing over the affected area. Water first weakens the underlying soil; traffic then fatigues and breaks the poorly supported asphalt surface in the affected area. Continued traffic action ejects both asphalt and the underlying soil material to create a hole in the pavement.
A flat roof is a roof which is almost level in contrast to the many types of sloped roofs. The slope of a roof is properly known as its pitch and flat roofs have up to approximately 10°. Flat roofs are an ancient form mostly used in arid climates and allow the roof space to be used as a living space or a living roof. Flat roofs, or "low-slope" roofs, are also commonly found on commercial buildings throughout the world. The U.S.-based National Roofing Contractors Association defines a low-slope roof as having a slope of 3 in 12 (1:4) or less.
Soil cement is a construction material, a mix of pulverized natural soil with small amount of portland cement and water, usually processed in a tumbler, compacted to high density. Hard, semi-rigid durable material is formed by hydration of the cement particles.
A gravel road is a type of unpaved road surfaced with gravel that has been brought to the site from a quarry or stream bed. They are common in less-developed nations, and also in the rural areas of developed nations such as Canada and the United States. In New Zealand, and other Commonwealth countries, they may be known as metal roads. They may be referred to as "dirt roads" in common speech, but that term is used more for unimproved roads with no surface material added. If well constructed and maintained, a gravel road is an all-weather road.
Washboarding or corrugation is the formation of periodic, transverse ripples in the surface of gravel and dirt roads. Washboarding occurs in dry, granular road material with repeated traffic, traveling at speeds above 8.0 kilometres per hour (5 mph). Washboarding creates an uncomfortable ride for the occupants of traversing vehicles and hazardous driving conditions for vehicles that travel too fast to maintain traction and control.
Chipseal is a pavement surface treatment that combines one or more layer(s) of asphalt with one or more layer(s) of fine aggregate. In the United States, chipseals are typically used on rural roads carrying lower traffic volumes, and the process is often referred to as asphaltic surface treatment. This type of surface has a variety of other names including tar-seal or tarseal, tar and chip, sprayed sealsurface dressing, or simply seal.
Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined materials in the world. Aggregates are a component of composite materials such as concrete and asphalt; the aggregate serves as reinforcement to add strength to the overall composite material. Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under foundations, roads, and railroads. In other words, aggregates are used as a stable foundation or road/rail base with predictable, uniform properties, or as a low-cost extender that binds with more expensive cement or asphalt to form concrete. Although most kinds of aggregate require a form of binding agent, there are types of self-binding aggregate which do not require any form of binding agent.
Stone mastic asphalt (SMA), also called stone-matrix asphalt, was developed in Germany in the 1960s with the first SMA pavements being placed in 1968 near Kiel. It provides a deformation-resistant, durable surfacing material, suitable for heavily trafficked roads. SMA has found use in Europe, Australia, the United States, and Canada as a durable asphalt surfacing option for residential streets and highways. SMA has a high coarse aggregate content that interlocks to form a stone skeleton that resists permanent deformation. The stone skeleton is filled with a mastic of bitumen and filler to which fibres are added to provide adequate stability of bitumen and to prevent drainage of binder during transport and placement. Typical SMA composition consists of 70−80% coarse aggregate, 8−12% filler, 6.0−7.0% binder, and 0.3 per cent fibre.
Filler materials are particles added to resin or binders that can improve specific properties, make the product cheaper, or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers are used every year in application areas such as paper, plastics, rubber, paints, coatings, adhesives, and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black. Filler materials can affect the tensile strength, toughness, heat resistance, color, clarity, etc. A good example of this is the addition of talc to polypropylene. Most of the filler materials used in plastics are mineral or glass based filler materials. Particulates and fibers are the main subgroups of filler materials. Particulates are small particles of filler that are mixed in the matrix where size and aspect ratio are important. Fibers are small circular strands that can be very long and have very high aspect ratios.
Crushed stone or angular rock is a form of construction aggregate, typically produced by mining a suitable rock deposit and breaking the removed rock down to the desired size using crushers. It is distinct from naturally occurring gravel, which is produced by natural processes of weathering and erosion and typically has a more rounded shape.
Bituminous waterproofing systems are designed to protect residential and commercial buildings. Bitumen is a material made up of organic liquids that are highly sticky, viscous, and waterproof. Systems incorporating bituminous-based substrates are sometimes used to construct roofs, in the form of "roofing felt" or "roll roofing" products.
Resperion is a company based in Scottsdale, Arizona that is involved in the creation and development of a variety of products used in road construction, soil stabilization, dust control, and natural paving alternatives.
Soil stabilization is a general term for any physical, chemical, mechanical, biological, or combined method of changing a natural soil to meet an engineering purpose. Improvements include increasing the weight-bearing capabilities, tensile strength, and overall performance of unstable subsoils, sands, and waste materials in order to strengthen road pavements.
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