Scan the text and speak on a concrete mixer

A concrete mixer (also commonly called a cement mixer) is a device that homogeneously combines cement, aggregate such as sand or gravel, and water to form concrete. A typical concrete mixer uses a revolving drum to mix the components. For smaller volume works portable concrete mixers are often used so that the concrete can be made at the construction site, giving the workers ample time to use the concrete before it hardens. An alternative to a machine is mixing concrete or cement by hand. This is usually done in a wheelbarrow; however, several companies have recently begun to sell modified tarps for this purpose.

Today's market increasingly requires consistent homogeneity and short mixing times for the industrial production of ready-mix concrete. This has resulted in new technologies for concrete production. Worldwide, therefore, twin-shaft batch mixers are becoming more important for high-quality concrete production. They introduce very high turbulence into the mix and achieve about 95% homogeneity at only around 30 seconds mixing time per batch.

Special concrete transport trucks are made to transport and mix concrete from a factory to the construction yard. They are charged with dry materials and water, with the mixing occurring during transport. The interior of the drum on a concrete truck is fitted with a spiral blade. In one rotational direction, the concrete is pushed deeper into the drum. This is the direction the drum is rotated while the concrete is being transported to the building site. This is known as "charging" the mixer. When the drum rotates in the other direction, it forces the concrete out of the drum. From there it may go onto chutes to guide the viscous concrete directly to the job site. If the truck cannot get close enough to the site to use the chutes, the concrete may be discharged into a concrete pump connected to a flexible hose, or onto a conveyor belt which can be extended some distance (typically ten meters). A pump provides the means to move the material to precise locations, multi-floor buildings, and other distance prohibitive locations.

Notes:

portable – переносный; передвижной

ample – достаточный

homogeneity – однородность; гомогенность

turbulence - турбулентность

charging - загрузка

viscous - вязкий, густой, тягучий

Section II. Lexical - Grammar Tests.

Для того, чтобы правильно выполнить контрольные работы, необходимо усвоить следующий грамматический материал:

1. Неличные формы глагола и конструкции с ними:

сложное подлежащее (Complex Subject),сложное дополнение (Complex Object), инфинитивные обороты с предлогом for , независимый причастный оборот.

2. Сослагательное наклонение. Типы условных предложений.

3. Повторение основных грамматических конструкций, представляющих наибольшую трудность для понимания и перевода.

Test 1. Crane

Crane is a hoisting machine so constructed as to move loads both vertically and in other directions. Cranes are commonly employed in the transport industry for the loading and unloading of freight; in the construction industry for the movement of materials; and in the manufacturing industry for the assembling of heavy equipment. Cranes move heavy loads by means of ropes or cables that ride over pulleys. Nearly all of them move loads both vertically and horizontally. Machines that can only raise and lower loads are called hoists, or winches. Small cranes are operated by a hand crank, most large cranes are powered by electric motors or diesel engines. Originally large cranes were powered by steam engines.

A crane picks up a load by means of an attachment such as a hook, bucket or platform. A long arm called a boom moves the load about. On most cranes, the attachment is connected to a block and tackle, a system of pulleys and a cable. The end of the cable winds around a winch. Turning the winch raises or lowers the load. Various devices prevent the weight of the load from tipping the crane.

There are three types of cranes: (1) mobile cranes, (2) stationary cranes, and (3) traveling cranes. In mobile and stationary cranes, the cable that leads from the block and tackle passes around a pulley at the end of a boom, then winds around the winch. The entire boom can swing about to move the load along an arc. In addition, all mobile cranes and some stationary cranes can raise and lower the boom. Raising the boom moves the load toward the base of the crane. Lowering the boom moves the load away from the base.

On most mobile cranes, the base is mounted on wheels or crawler tracks. To prevent tipping when the boom is extended, mobile cranes use counterweights, rollers, or long legs that extend outward from the base.

Stationary cranes also use these devices to prevent tipping. In addition, they use guy lines, long cables connecting the crane with a massive object such as a concrete column that has been driven into the ground.

A traveling crane has no boom. Its hoisting equipment is mounted in a trolley, a device that travels on wheels along a horizontal bridge. In overhead cranes, which are permanently installed in buildings, the bridge extends the entire width of a room. On the ends of the bridge are wheels that travel along elevated, horizontal tracks. These tracks extend the length of the room. In straddle carries, the ends of the bridge are attached to long, vertical columns. The columns are on wheels.

Notes:

hoist -подъемник

winch – лебедка

hook - грузоподъемный крюк

bucket - ковш

boom –вылет стрелы (крана)

block and tackle – веревка с блоком

pulley- ролик, блок

straddle carrier – контейнеровоз-погрузчик