Vocabulary notes

strength of concrete прочность бетона

reinforced concrete армированный бетон

ferroconcrete железобетон

prestressed concrete предварит. напряженный бетон

structural material строительные материалы

sand песок

gravel гравий

cement цемент

lime известь

gypsum гипс

aggregate заполнитель

fine aggregate мелкий заполнитель

coarse aggregate крупный заполнитель

binder вяжущее

curing выдерживание

pouring заливка бетона, укладка бетонной смеси

shrinkage усадка

to mold отливать в форму

EXERCISES

I. Read and translate the text.

II. Find synonyms for the following words:

structural material; amount of cement; to affect; construction; essential; aggregate; to erect.

III. Explain the meaning of the following words:

aggregate; mixture; to be free from; water-to-cement ratio; environmental factors; masonry construction.

IV. Form nouns from the following words:

to mix; practical; to produce; to develop; to design; strong; to measure; to shrink; to invent; to contribute; to apply.

V. Put the questions:

Q: ...

A: I know that concrete is compound structural material.

Q: ...

A: The main aggregates are sand, lime, and clay.

Q: ...

A: The character of concrete is determined by a water-to-cement ratio.

Q: …

A: The strength of concrete is measured in pounds per square inch.

VI. Retell the text using words and word combinations from the vocabulary list.

Requirements for concrete quality

Uniform quality of a concrete is of great importance for modern construction. Procedures for obtaining high quality concrete are given in many publications.

Both normal weight and structural lightweight concrete can be made uniform with proper mix proportioning and production controls. Normally concrete for segmental construction will have a slump of 3 to 5 in., and 28-day strength greater than the strength specified by structural design. It is recommended that statistical methods be used to evaluate concrete mixes

The methods and procedures used to obtain the characteristics of concrete required by the design may differ somewhat depending on whether the segments are cast in the field or in a plant. The results will be influenced by curing temperature and type of curing. Liquid or steam curing or electric heat curing may be used.

A sufficient number of test mixes should be made to assure uniformity of strength and modulus of elasticity. Careful selection of aggregates, cement, admixtures and water will improve strength and modulus of elasticity and will also reduce shrinkage and creep. Soft aggregates and poor sands should be avoided. Creep and shrinkage data for concrete mixes should be available or should be determined by tests.

It is better not to use corrosive admixtures such as calcium chloride or those containing substantial chlorides, nitrates, sulfates and fluorides. Water-reducing admixtures which improve concrete resistance to environmental effects, such as de-icing salts and freeze and thaw actions are highly desirable. However, their use should be rigidly controlled in order not to increase undesirable variations in strength and modulus of elasticity of the concrete.

Mixes should be designed to minimize creep and shrinkage. Reliable data on the potential of the mix in terms of strength gain and creep and shrinkage performance should be used as a basis for improved design parameters.