Lesson 6

Exercises

I. Утворіть слова у відповідності із моделлю та перекладіть їх українською.

Модель I: основа дієслова + - ion (-tion, - ation) →іменник

construct, select, determine, combine, discuss, reduce, compact;

Модель II : прикметник + - ly →прислівник

sufficient, wide, ideal, full, fair. essential, new;

Модель III : основа дієслова + -able ( ible ) →прикметник

work, suscept, compact;

Модель IV : основа дієслова + - ment→іменник

move, place, require.

П. Перекладіть групи слів одного кореня українською.

essence - essential - essentially - essentiality; to determine -determinative - determined /a/ - determination - determinate /a/ - to determinate - determinant; to select - selected /a/ - selection - selectionist - selective – selector.

III. Перекладіть наступні складові слова українською.

peak-point, right-hand, better-graded, overflow, fully-compacted.

IV. Дайте українські еквіваленти сполучень іменників.

mix design, water/cement ratio law, concrete strength, workability requirement, concrete engineer, shrinkage factor, slump test.

V. Складіть англо-українські пари словосполучень, еквівалентних за значенням.

1. concrete mix; 2. concrete strength; 3. water content; 4. rich mix; 5. lean mix;

6. specific gravity; 7. surface area.

1. міцність бетону; 2. жирна суміш; 3. тоща суміш; 4. бетонна суміш; 5. площа поверхні; 6. вміст води; 7. питома вага.

DESIGN OF MIXES

As has already been discussed, concrete is composed of cement, water and aggregate. Before construction of a concrete road can begin it is necessary therefore to determine what proportions of each ingredient should be present in the mixture. This determination is known as the mix design.

There are a number of different methods for "designing" mixes, all of which have either directly or indirectly the ultimate aim of obtaining, a concrete of the desired strength and workability at the lowest cost. Another characteristic which all the methods have in common is that, even though the selection of the initial combination may be based on well-tried, data obtained from previous experience, the ultimate design is always a result of extensive trial mixes which are tested at the site.

In the discussion so far free use has been made of the term workability. This is the term, which is easily understood but is relatively hard to define. Perhaps the easiest way to do so is to say that the more workable a mix, the less work is required to compact it fully. The degree of workability required of the concrete on any road scheme is dependent on the nature of the construction and the method of compaction. Thus, a road slab in which mesh reinforcement is utilized, requires a mixture with greater workability than a plain mass concrete slab, while a concrete mix which is to be compacted by mechanical vibration can be less workable than one which is to be tamped by hand.

Factors, which effect the workability of the mixture, are as follows:

1. Water/cement ratio. Provided that the cement and aggregate proportions remain constant the workability of a mix increases as the water content is increased.

2. Cement/aggregate ratio. If the water/cement ratio is kept constant, a rich mix, i.e. one having a high cement content, is more workable than a lean mix.

3. Shape, size and grading of the aggregate. The effects of these factors can be observed by noting the results of adding aggregate to a neat cement paste of a particular water/cement ratio. It is found that the smaller the surface area of the added material in relation to the given quantity of cement, the greater is the workability, since more water is available to wet the surfaces of the particles. Thus it is that a concrete mix having smooth and round aggregate particles is more workable than one having rough angular particles of a similar grading. Flaky aggregates result in the harshest and least workable concrete mixes. Workability also increases as the maximum size of the aggregate is increased. A corollary to this is that for a given degree of workability the fine content of a mixture may be reduced as the maximum size of the aggregate is increased. In general the better-graded a mix, the more workable it is: this effect is more noticeable as the mix gets leaner.

Unfortunately, there is no single test, which is universally accepted as truly measuring workability. Two tests, however, which are of particular interest are the Slump and the Compacting Factor tests.

Завдання I. Перекладіть письмово перший абзац.

Завдання II. Розкажіть про фактори, які впливають на зручність укладання суміші.