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Vocabulary notes.

Predetermined property – визначена властивість Watertight - водонепроникний

According to the purpose – згідно призначенню Thaw - відлига

To meet requirements – задовільняти вимоги Environment - середовище

Average density – середня щільнист Admixture – домішка, суміш

Exercises

1. Find in the text the English equivalents to the following word combinations:

Механичні властивісті, високий опір, захистити від ржавіння, заповнювач бетону, теплостійкістьь, ставати твердим за будь-які умови, необхідні складові частини, кількість поронеч у суміші.

2. Answer the following questions:

1. What properties must concrete have? 2. What requirements must concrete meet?

  1. How may concrete be classified? 4. What kinds of concrete are mentioned in the text? 5. What aggregates do coarse concrete use? 6. What aggregates do fine concrete use? 7. What kinds of concrete are used in bearing structures? 8. What must we to do produce concrete having a predetermined strength and durability? 9. What does the strength of concrete depend on?

Text 19 Reinforced Concrete Members.

Reinforced concrete members should be designed so that their overall dimensions,

cross-sections and reinforcement would be optimal for manufacture at precasting plants and erection on the site. Members which can be mass-produced by high efficiency equipment without labour-consuming manual operations are always preferable. The design of a member and the manufacture procedures are v closely related. There exist several technologies for precast concrete manufacture.

Line Production. With this type of manufacture, concrete members are made in forms installed on cars moving by rail from one work station to another. As a car moves on, workmen successively carry out all the necessary operations, namely erect the reinforcement, tension the prestressing steel, install void formers into hollow- core slabs, place and compact the concrete mix, remove the void formers, and cure the concrete in a moist atmosphere and at elevated temperature in order to accelerate its hardening. All cars are advanced at a predetermined speed. This high-efficiency type of manufacture is utilized by major plants in the quantity production of members having a relatively small mass.

Stage-by-Stage Production. With this type of manufacture, all operations are carried out by appropriate plant shops, and a form with a member is transported from station to station by cranes. Here, no speed is predetermined.

Casting-Bed Technology. A distinction of this technology is that members remain at the same place during their manufacture and heat curing, and the units carrying out the necessary operations move along the stationary forms. Casting beds are equipped with traveling cranes, concrete placers, and vibrators to compact the concrete mix. Structural members are fabricated in plain or shaped forms (matrices or cassettes). This technology is used to manufacture large and prestressed members for industrial buildings (such as trusses, roof beams, crane beams, columns, and so on).

Panels for floors, ceilings and walls of civil buildings are widely made in cassettes. Members are made in stationary beds consisting of a faggot of vertical metal cassettes, so that several panels may be produced at a time. The assembly and disassembly of cassettes are mechanized. Reinforcing cages are installed inside each compartment of a cassette. Concreting is by a thin-consistency mix pneumatically applied through pipes. Owing to their vertical position, the surface of such members is even and smooth.

In the vibration-rolling process, thin floor, ceiliug and wall panels are manufactured on a continuously moving belt whose smooth or corrugated surface serves as a mould. After a reinforcing cage has been installed, the concrete mix is placed on the belt, which is then vibrated and compacted from above by rollers. The members being rolled are covered from above and heated from below. During their motion with the belt (for several hours), they attain the necessary strength; after cooling on racks, finished products are transported to a storehouse. The operations are carried out at a rate keyed to the speed of the forming belt.