Make up a detailed plan of the text.
Retell the text according to your plan.
1.3 The general classification of road materials:
Concrete, chipseal
New words and phrases to learn:
cementitious materials –
цементирующие материалы
chemical admixtures – химические примеси
to solidify – застывать
crack reflection – образование трещин
stone retention – сцепление камней
volatile organic compounds – летучие органические вещества
solvent content – растворимый компонент
patch – заплата
ditch – канава
1. Read and translate the text:
- Concrete
Concrete is a construction material composed of cement (commonly Portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate such as gravel, limestone or granite plus a fine aggregate such as sand), water, and chemical admixtures. Concrete solidifies and hardens after mixing with water and placement due to a chemical process known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a stone-like material. Concrete is used to make pavements, pipe, architectural structures, foundations, motorways/roads, bridges/overpasses, parking structures, brick/block walls and footings for gates, fences and poles.
- Chipseal
Chipseal is a pavement surface treatment that combines a layer(s) of asphalt with a layer(s) of fine aggregate. Chipseals are typically used on rural roads carrying lower traffic volumes, and the process is often referred to as "asphaltic surface treatment". It is cheaper than resurfacing an asphalt concrete or a Portland Cement Concrete pavement, but not as long lasting.
Chipseals are constructed by evenly distributing a thin base of hot bitumen or asphalt onto an existing pavement and then embedding finely graded aggregate into it. The aggregate is evenly distributed over the seal spray, then rolled into a smooth pavement surface. A chipseal surfaced pavement can optionally be sealed with a top layer which is referred to as a fog seal or cape seal.
The introduction of polymer-modified bitumen and emulsion binder has increased the chipseal's ability to prevent crack reflection and improve stone retention by improving the properties of the bitumen binder. Newer techniques use asphalt emulsion (a mixture of liquid asphalt, surfactant, and water) instead of asphalt. This has been shown to help reduce aggregate loss and reduce cost of installation, but can increase the occurrence of stripping. It reduces emissions of volatile organic compounds (VOCs) due to the lower solvent content.
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It can keep good pavement in good condition by sealing out water, but provides no structural strength and will only repair minor cracks. While the small stones used as surface yield a relatively even surface without the edges of patches, it also results in a very rough surface that leads to significantly louder rolling noises of automobile wheels.
Although chipseal is an effective low cost way to repair road, it has some drawbacks. Loose crushed stone is often left on the surface, due to under-application of emulsion or over application of stone. If not removed, this can cause safety and environmental problems such as cracked windshields, loss-of-control crashes (especially for motorcyclists and bicyclists), and deposition of foreign material into drainage courses. Therefore, it is very important to sweep the road after the emulsion sets.
2. Answer the questions:
- Give the definition of concrete. Say what it is used for.
- What is another name of chipseal?
- What is the main task of chipseal as a structural material?
- What are the advantages of chipseal use?
- What are the drawbacks of chipseal?
3. Match the words from the given columns:
| portland coarse chemical asphalt solvent structural crushed bitumen cementitious hot | concrete materials content stone admixtures binder cement bitumen aggregate strength |
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