Hot summer, walking on the asphalt road feel soft, feel at any time will be a foot down. And the asphalt gives us a taste of summer

What is asphalt?

Bitumen is a product of crude oil processing. It is a black or black brown viscous liquid or solid at room temperature. It mainly contains soluble trichloroethylene hydrocarbon derivatives, whose properties and composition vary with the source and generation method. Bitumen, like petroleum, is a complex organic mixture with no fixed chemical composition or physical constants

History of asphalt

At that time pitch was made from pine oil and tar. Bitumen is sometimes found in nature as a mineral. Today's bitumen is the residue of crude oil refining, which is not done in a perfect way. The most common extraction method is to obtain raw oil by fractionating.

When asphalt is heated to 230T, it becomes sticky, and when it cools it becomes a hard solid. In ancient Mesopotamia, bitumen was often collected as a mineral in surface sediments.

The Sumerians in the Mesopotamia and the Palestinians at both ends of Asia used asphalt for their walls.

Excavations in the city of Jericho revealed a brick wall of asphalt bonded together, which was built between 2500 and 2100 BC. In ancient Babylon, asphalt was used to pave roads, seal brick houses, build embankments and reservoirs. In 2500 BC, Indians often used bitumen to plug up cracks when building houses.

At a religious shrine in Mohentzo Daro, India, asphalt is used to seal the crevices in the brick walls of a pool where worshippers bathe. Asphalt can play the same role as mortar, it is often used in combination with burned brick, plant fibers, to make the strength of the bond greatly increased.

In addition to protecting brick houses, it is also used for insulation, and some people use it as a moisture barrier. There is an ancient bridge over the Euphrates River. The dry parts of the piers of the bridge are coated with asphalt to prevent corrosion of the piers.

In the late 18th century, British engineers John Lawton McAdam and Thomas Telford led a team of road builders that revolutionized the system of dirt roads.

McAdam's road-building system is made of gravel and compacted with heavy milkers. This type of gravel is called gravel road. But it wasn't until the 19th century that asphalt was discovered to be the perfect material for modern roads. The inventor of asphalt roadbed was a man named Telford.

In 1838, in Nordingshire, England, asphalt was first used to pave a tarred road. By the 1920s, the old highway and the development of The Times more and more unsuitable, asphalt as the material of the asphalt road increasingly become the main body of the modern highway. Later, Britain, the United States developed a great deal of railways, road construction therefore stalled.

For almost all of the 19th century, many major cities in the United States were connected by rail or water and lacked a major highway system. The road system in and around the city was connected only by dirt roads unpaved with asphalt, which in bad weather made it impossible for wagons and trucks to travel.

After the 1890s, the bicycle was introduced into the United States, and the research of air tire was gradually improved. Political pressure forced the U.S. government to invest in roads. Local governments began to use pervious concrete and asphaltic concrete when levelling roads, and asphalt-infused gravel was often used to pave roads.

At that time, the road gained the name "tarmac road" in public. In the 1920s, states began using gasoline taxes to pay for the maintenance and construction of arterial roads, which greatly increased the intercity highway network. Asphalt concrete and tarmac are used on many roads in the highway network.

Why asphalt?

The use of asphalt road has many advantages, such as small dust, low noise, comfortable driving, and asphalt road maintenance is relatively easy, cement board rotten to chisel are laborious, new paved open traffic to wait for a long time, so now a lot of cement road is broken with asphalt to repair a piece. Cement is also fading.

Hazard of asphalt

Asphalt harm to human body: skin damage, such as phototoxic dermatitis, melanism, occupational acne and verrucous growth and accident caused by heat burn; There will also be asphalt smoke and dust through the respiratory tract and pollution of the skin and cause poisoning, serious will cause cancer.

For the environment

1, harm farmland, green belt after the use of snow melt agent often piled up on both sides of the road in the green belt or farmland, after the spring of the salt residues all piled up in the farmland and green belt, crops and trees afraid of salt, will cause a large number of green plants death, even devastating. Even if it is replanted, it is necessary to replace all the soil, and the farmland is even more doomed, and its loss is self-evident. 2. Shorten road life salt substances and asphalt will produce chemical reactions, which will greatly reduce the gripping capacity of asphalt materials and sand and stone, resulting in asphalt surface shedding, and large area pavement damage under the action of traffic load. After salt meets water, salt rise will occur, and it will cause roadbed damage, which will greatly increase the difficulty of later road maintenance. Salt is also harmful to cement concrete pavement. The expensive salt-resistant cement will not be used on the side of cement concrete pavement on urban roads. 3. Environmental pollution After salt substances enter the ground, they will inevitably pollute the local groundwater resources.

Taste of summer

Living in asphalt-polluted air, easy to reduce immunity. The main components of asphalt and its flue gas are phenols, compounds, anthracene, naphthalene, pyridine, etc., which are irritating to the skin and mucous membranes. The skin is coated with 30% coal tar asphalt toluene solution for three times, and the local inflammation is followed by excessive keratosis and chapping.

The damage caused by asphalt dust and smoke to the eyes is mainly blepharoconjunctivitis, sometimes accompanied by superficial spotted keratitis, and pterygium occupies a certain proportion in the elderly. Nasopharynx often dry, burning, can also cause rhinitis, pharyngitis and so on.

After smelling the asphalt smell, dizziness, head swelling, headache, chest tightness, fatigue, nausea or cough, palpitation, tinnitus and other discomfort may occur, especially when operating under the hot sun. Disengagement (such as after work) symptoms often resolve quickly. Severe cases (such as severe phototoxic dermatitis) may be accompanied by fever.

Asphalt has brought us a lot of convenience, but also to speed up the development of our traffic, but its harm is immeasurable. So that's all for today's popular science sharing.