Math Is Fun Forum

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,218

Re: Miscellany

2251) Asphalt

Gist

Asphalt concrete (commonly called asphalt, blacktop, or pavement in North America, and tarmac or bitumen macadam in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams.

Asphalt is known as a mixture of bitumen (as binding material) and a significant amount of inert minerals such as sand, gravel, and crushed stone. It has a blackish-brown colour and is available as a solid at low temperatures and as a liquid at temperatures above 50°C.

Summary

asphalt, black or brown petroleum-like material that has a consistency varying from viscous liquid to glassy solid. It is obtained either as a residue from the distillation of petroleum or from natural deposits. Asphalt consists of compounds of hydrogen and carbon with minor proportions of nitrogen, sulfur, and oxygen. Natural asphalt (also called brea), which is believed to be formed during an early stage in the breakdown of organic marine deposits into petroleum, characteristically contains minerals, while residual petroleum asphalt does not.

The use of asphalt is very old, dating back to its use as a water stop between brick walls of a reservoir at Mohenjo-Daro (about the 3rd millennium bc) in Pakistan. In the Middle East it was extensively used for paving roads and sealing waterworks, important applications even today. The Pitch Lake on the island of Trinidad was the first large commercial source, but natural sources have since declined in importance as petroleum became the major source. Gilsonite, wurzilite, and similar vein asphalts have special uses in heat-resistant enamels; they are hard and are mined like coal. Petroleum asphalt is produced in all consistencies from light road oils to heavy, high-viscosity industrial types.

Asphalt softens when heated and is elastic under certain conditions. The mechanical properties of asphalt are of little significance except when it is used as a binder or adhesive. The principal application of asphalt is in road surfacing, which may be done in a variety of ways. Light oil “dust layer” treatments may be built up by repetition to form a hard surface, or a granular aggregate may be added to an asphalt coat, or earth materials from the road surface itself may be mixed with the asphalt.

Other important applications include canal and reservoir linings, dam facings, and other harbour and sea works; asphalt so used may be a thin, sprayed membrane, covered with earth for protection against weathering and mechanical damage, or thicker surfaces, often including riprap (crushed rock). Asphalt is also used for roofs, coatings, floor tilings, soundproofing, waterproofing, and other building-construction elements and in a number of industrial products, such as batteries. For certain applications an asphaltic emulsion is prepared, in which fine globules of asphalt are suspended in water.

Details

Asphalt is a mixture of aggregates, binder and filler, used for constructing and maintaining roads, parking areas, railway tracks, ports, airport runways, bicycle lanes, sidewalks and also play- and sport areas.

Aggregates used for asphalt mixtures could be crushed rock, sand, gravel or slags. Nowadays, certain waste and by-products, such as construction and demolition debris, are being used as aggregates, which increases the sustainability of asphalt.

In order to bind the aggregates into a cohesive mixture a binder is used. Most commonly, bitumen is used as a binder, although nowadays, a series of bio-based binders are also under development with the aim of minimising the environmental impact of the roads.

An average asphalt pavement consists of the road structure above the formation level which includes unbound and bituminous-bound materials. This gives the pavement the ability to distribute the loads of the traffic before it arrives at the formation level.

How is asphalt produced?

Asphalt is produced in an asphalt plant. This can be a fixed plant or even in a mobile mixing plant. It is possible to produce in an asphalt plant up to 800 tons per hour. The average production temperature of hot mix asphalt is between 150 and 180°C, but nowadays new techniques are available to produce asphalt at lower temperatures.

Different kinds of asphalt

To be able to provide the best performance to different applications, a large variety of asphalt mixes can be used. Due to the different requirements (amount of traffic, amount of heavy vehicles, temperature, weather conditions, noise reduction requirements, etc.) the respective mix used needs to have an sufficient stiffness and resistance to deformation in order to cope with the applied pressure from vehicle wheels on the one hand, yet on the other hand, they need to have an adequate flexural strength to resist cracking caused by the varying pressures exerted on them. Moreover, good workability during application is essential in order to ensure that they can be fully compacted to achieve optimum durability.

Asphalt mixtures can be produced at different temperatures:

Hot Mix Asphalt (HMA)

Hot asphalt mixes are generally produced at a temperature between 150 and 180 °C. Depending on the usage, a different asphalt mixture can be used. For more details of the different asphalt mixtures, go to “Asphalt products”

Warm Mix Asphalt (WMA)

A typical WMA is produced at a temperature around 20 – 40 °C lower than an equivalent Hot Mix Asphalt. Significantly less energy is involved and, consequently, less fumes are produced (as rule of thumb, a reduction of 25ºC produces a reduction of 75% of fumes emission). In addition, during the paving operations, the temperature of the material is lower, resulting in improved working conditions for the crew and an earlier opening of the road.

Cold Mix Asphalt

Cold mixes are produced without heating the aggregate. This is only possible, due to the use of bitumen emulsified in water, which breaks either during compaction or during mixing. Producing the coating of the aggregate. Over the curing time, water evaporates and strength increases. Cold mixes are particularly recommendable for lightly trafficked roads.

Different asphalt layers

An asphalt pavement consists of different asphalt layers.

In general the asphalt layers are paved on a bound or unbound road base layer. Starting at the road surface, the first layer is called the surface course. The second layer is mostly called the binder course. The lower layers are the base courses.

Surface course

The surface course constitutes the top layer of the pavement and should be able to withstand high traffic- and environmentally-induced stresses without exhibiting unsatisfactory cracking and rutting. Its main mission is to provide an even profile for the comfort of the user, while providing enough texture to ensure minimum and safe skid resistance. Depending on local conditions, functional characteristics such as skid resistance, noise reduction and durability are often required for wearing courses. In some cases, rapid drainage of surface water is desired while in other cases, the wearing course should be impermeable in order to keep water out of the pavement structure. A wide range of surface layer products can be used depending on specific requirements.

Binder course

Binder courses are designed to withstand the highest shear stresses that occur about 50 – 70 mm below the asphalt surface. The binder course is therefore placed between the surface course and base course to reduce rutting by combining qualities of stability and durability. Stability can be achieved by sufficient stone-on-stone contact and stiff and/or modified binders.

Base course

The base course is perhaps the most important structural layer of the pavement, which is intended to effectively distribute traffic and environmental loading in such a way that underlying unbound layers are not exposed to excessive stresses and strains. This often implies comparatively high stiffness of the base course. Next to this the base course should also show adequate fatigue resistance.

Unbound materials and foundation

Since the formation and sub-soil often constitute relatively weak materials, it is of utmost importance that the damaging loadings are effectively eliminated by the layers above. In this case, unbound road-base or sub-base layers consisting of uncrushed or crushed aggregate can be suitable.

Additional Information

Asphalt is a dark brown to black, highly viscous, hydrocarbon produced from petroleum distillation residue. This distillation can occur naturally, resulting in asphalt lakes, or occur in a petroleum refinery using crude oil. In 2020, the U.S. produced about 21 million tons of asphalt (US EIA). Roads and highways constitute the largest single use of asphalt at about 80 percent of the total (Fredonia Group). In HMA, asphalt functions as a waterproof, thermoplastic, viscoelastic adhesive. By weight, asphalt generally accounts for between 4 and 8 percent of HMA and makes up about 25 – 30 percent of the cost of an HMA pavement structure depending upon the type and quantity. The paving industry also uses asphalt emulsions, asphalt cutbacks and foamed asphalt.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,218

Re: Miscellany

2252) Millenium

Gist

A millennium is a period of one thousand years, especially one which begins and ends with a year ending in `000,' for example the period from the year 1000 to the year 2000. [formal]

Since in Latin mille means "thousand", a millennium lasts 1,000 years.

A millennium ( pl. millennia or millenniums) is a period of one thousand years or one hundred decades or ten centuries, sometimes called a kiloannum (ka), or kiloyear (ky).

Summary

A millennium is a period of 1,000 years. The Gregorian calendar, put forth in 1582 and subsequently adopted by most countries, did not include a year 0 in the transition from bc (years before Christ) to ad (those since his birth). Thus, the 1st millennium is defined as spanning years 1–1000 and the 2nd the years 1001–2000.

A millennium is a period of 1,000 years. The Gregorian calendar, put forth in 1582 and subsequently adopted by most countries, did not include a year 0 in the transition from bc (years before Christ) to ad (those since his birth). Thus, the 1st millennium is defined as spanning years 1–1000 and the 2nd the years 1001–2000. Although numerous popular celebrations marked the start of the year 2000, the 21st century and 3rd millennium ad began on January 1, 2001.

Details

A millennium (pl. millennia or millenniums) is a period of one thousand years or one hundred decades or ten centuries, sometimes called a kiloannum (ka), or kiloyear (ky). Normally, the word is used specifically for periods of a thousand years that begin at the starting point (initial reference point) of the calendar in consideration and at later years that are whole number multiples of a thousand years after the start point.[clarification needed] The term can also refer to an interval of time beginning on any date. Millennia sometimes have religious or theological implications.

The word millennium derives from the Latin mille, thousand, and annus, year.

There was a public debate leading up to the celebrations of the year 2000 as to whether the beginning of that year should be understood as the beginning of the "new" millennium. Historically, there has been debate around the turn of previous decades, centuries, and millennia, but not so much for decades. The issue arises from the difference between the convention of using ordinal numbers to count years and millennia, as in "the third millennium", or using a vernacular description, as in "the two thousands". The difference of opinion comes down to whether to celebrate, respectively, the end or the beginning of the "-000" year. The first convention is common in English-speaking countries, but the latter is favoured in, for example, Sweden (tvåtusentalet, which translates literally as the two thousands period).

Those holding that the arrival of the new millennium should be celebrated in the transition from 2000 to 2001 (i.e., December 31, 2000, to January 1, 2001) argued that the Anno Domini system of counting years began with the year 1 (there was no year 0) and therefore the first millennium was from the year 1 to the end of the year 1000, the second millennium from 1001 to the end of 2000, and the third millennium beginning with 2001 and ending at the end of 3000. Similarly, the first millennium BC was from the year 1000 BC to the end of the year 1 BC.

Popular culture supported celebrating the arrival of the new millennium in the transition from 1999 to 2000 (i.e., December 31, 1999, to January 1, 2000), in that the change of the hundreds digit in the year number, with the zeroes rolling over, is consistent with the vernacular demarcation of decades by their 'tens' digit (e.g. naming the period 1980 to 1989 as "the 1980s" or "the eighties"). This has been described as "the odometer effect". Also, the "year 2000" had been a popular phrase referring to an often utopian future, or a year when stories in such a future were set. There was also media and public interest in the Y2K computer bug.

A third position was expressed by Bill Paupe, honorary consul for Kiribati: "To me, I just don't see what all the hoopla is about ... it's not going to change anything. The next day the sun is going to come up again and then it will all be forgotten." Even for those who did celebrate, in astronomical terms, there was nothing special about this particular event.

Stephen Jay Gould, in his essay "Dousing Diminutive Dennis' Debate (or DDDD = 2000)", discussed the "high" versus "pop" culture interpretation of the transition. Gould noted that the high culture, strict construction had been the dominant viewpoint at the 20th century's beginning, but that the pop culture viewpoint dominated at its end.

The start of the 21st century and 3rd millennium was celebrated worldwide at the start of the year 2000. One year later, at the start of the year 2001, the celebrations had largely returned to the usual ringing in of just another new year, although some welcomed "the real millennium", including America's official timekeeper, the U.S. Naval Observatory, and the countries of Cuba and Japan.

The popular approach was to treat the end of 1999 as the end of "a millennium" and to hold millennium celebrations at midnight between December 31, 1999, and January 1, 2000, with the cultural and psychological significance of the events listed above combining to cause celebrations to be observed one year earlier than the formal date.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,218

Re: Miscellany

2253) Liquid Paraffin

Gist

Liquid paraffin is primarily used as a pediatric laxative in medicine and is a popular treatment for constipation and encopresis. Because of its ease of titration, the drug is convenient to synthesize.

Liquid Parafin belongs to the group of medicines called 'laxatives' used to treat constipation in conditions like piles, fistula, fissures, pre/post-operative conditions, elderly and bed-ridden patients. Constipation refers to infrequent bowel movements in which the stools are often dry, painful, and hard to pass.

Summary

Liquid paraffin is a mixture of liquid hydrocarbons. Its main use has been as a lubricant laxative but it is not recommended, because of its adverse effects. Nevertheless, it continues to be used for this purpose and is reportedly as effective as lactulose . However, the erstwhile Committee on Safety of Medicines in the UK recommended the following precautions :

• pack sizes to be limited to 160 ml;
• liquid paraffin to be used only for the symptomatic relief of constipation;
• prolonged use to be avoided and the package label to state “repeated use is not recommended”;
• to be contraindicated in children under 3 years of age.

Liquid paraffin has also been used in ointments, as an emollient in skin diseases, and as a lubricant in treating dry eyes. Injection of liquid paraffin into the pleural cavity (oleothorax) was a widely used treatment for pulmonary tuberculosis before effective antituberculosis drugs became available. Long-term complications continue to be reported.

Details

Liquid paraffin, also known as paraffinum liquidum, paraffin oil, liquid paraffin oil or Russian mineral oil, is a very highly refined mineral oil used in cosmetics and medicine. Cosmetic or medicinal liquid paraffin should not be confused with the paraffin (i.e. kerosene) used as a fuel. The generic sense of paraffin meaning alkane led to regional differences for the meanings of both paraffin and paraffin oil. It is a transparent, colorless, nearly odorless, and oily liquid that is composed of saturated hydrocarbons derived from petroleum.

The term paraffinum perliquidum is sometimes used to denote light liquid paraffin, while the term paraffinum subliquidum is sometimes used to denote a thicker mineral oil.

History

Petroleum is said to have been used as a medicine since 400 BC, and has been mentioned in the texts of classical writers Herodotus, Plutarch, Dioscorides, Pliny, and others. It was used extensively by early Arabians and was important in early Indian medicine. Its first use internally is attributed to Robert A. Chesebrough, who patented it in 1872 for the manufacture of a "new and useful product from petroleum." After Sir W. Arbuthnot Lane, who was then Chief Surgeon of Guy's Hospital, recommended it as a treatment for intestinal stasis and chronic constipation in 1913, liquid paraffin gained more popularity.

Usage in medicine

Liquid paraffin is primarily used as a pediatric laxative in medicine and is a popular treatment for constipation and encopresis. Because of its ease of titration, the drug is convenient to synthesize. It acts primarily as a stool lubricant, and is thus not associated with abdominal cramps, diarrhea, flatulence, disturbances in electrolytes, or tolerance over long periods of usage, side effects that osmotic and stimulant laxatives often engender (however, some literature suggests that these may still occur). The drug acts by softening the feces and coats the intestine with an oily film. Because of this it reduces the pain caused by certain conditions such as piles (haemorrhoids). These traits make the drug ideal for chronic childhood constipation and encopresis, when large doses or long-term usage is necessary.

Consensus has not been entirely reached on the safety of the drug for children. While the drug is widely accepted for the management of childhood constipation in North America and Australia, the drug is used much less in the United Kingdom. The drug is endorsed by the American Academy of Pediatrics and the North American Society for Gastroenterology and Nutrition, with the latter organization outlining it as a first choice for the management of pediatric constipation. The drug is suggested to never be used in cases in which the patient is neurologically impaired or has a potential swallowing dysfunction due to potential respiration complications. Lipoid pneumonia due to mineral oil aspiration is thus a recognized severe complication of this medication, and there is a need for a heightened awareness among caregivers about the potential dangers of inappropriate mineral oil use. Some go as far as saying that it should never be used with children due to this risk.

Liquid paraffin is also used in combination with magnesium as an osmotic laxative, sold under the trade name Mil-Par (among others).

Additionally, it may be used as a release agent, binder, or lubricant on capsules and tablets.

Usage in cosmetics

Liquid paraffin is a hydrating and cleansing agent. Hence, it is used in several cosmetics both for skin and hair products. It is also used as one of the ingredients of after wax wipes.

Health

Upon being taken orally, liquid paraffin might interfere with the absorption of fat-soluble vitamins, though evidence does not seem to fully support this. It can be absorbed into the intestinal wall and may cause foreign-body granulomatous reactions in some rat species. These reactions might not occur in humans, however. Some evidence suggests that it engenders a lack of carcinogenicity. If liquid paraffin enters the lungs, it can cause lipoid pneumonia.

If injected, it can cause granulomatous reactions.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.