Test II

Match words in columns A and B (synonym match):

A B

1. to reference a). to approve b). to perform

c). to complete d). to consult

2. to describe a). to list b). to depict

c). to cite d). to hire

3. to measure a). to determine b). to insulate

c). to assume d). to suspend

4. flexibility a). reinforcement b). replacement

c). plasticity d). settlement

5. schedule a). enclosure b). timetable

c). partition d). substance

6. challenge a). perfection b). resistance

c). ornamentation d). invocation

7. regardless a). despite b). densely

c). continuously d). exceptionally

8. issue a). reason b). problem

c). base d). load

9. substantial a). reliable b). vertical

c). significant d). supportable

10. to preclude a). to prevent b). to differ

c). to excavate d). to cause

Test III

Select the best possible answer out of the choices from the list to the statements (multiple choice):

1. Workers precast concrete panels … .

a. setting up forms at the job site.

b. after preparation of the job site .

c. directly at the job site.

d. at a large manufacturing facility.

2. Tilt-up and tiltwall are two terms used … .

a. for the activity that can take place regardless the weather conditions.

b. for a precast construction project.

c. to describe the same process.

d. for prefabricated panel process providing a controlled environment.

3. Architects and tilt-up concrete contractors … .

a. have greater design restrictions and limits for the applications.

b. have a great deal of flexibility in planning and creating their buildings.

c. are at the mercy of climatic conditions.

d. emphasize the remarkable speed of the process.

4. When temperatures drop below freezing, … .

a. curing the concrete panels becomes more difficult and expensive.

b. construction schedules are more difficult to meet.

c. contractors are at the mercy of climatic conditions.

d. environmental factors preclude tiltwall as a viable option.

5. The precast concrete building process is similar to tilt-up construction,… .

a. but in the first case the panels must be smaller and more manageable to allow trucks to haul them.

b. but it provides a more controlled environment for consistent quality.

c. but it addresses the challenges presented by weather.

d. but presents different limitations not found in tilt-up construction.

Test IV

Complete the sentences by filling in the correct word that fits a statement (gap fill). Choose the appropriate words from the word bank given below.

A. trucked B. outdoors C. limits D. process

E. extremely F. predictable G. crews H. preparation

I. transportation J. benefit K. flexibility L. similar

1. Tilt-up and tiltwall are two terms used to describe the same …… .

2. Because the concrete tiltwall forms are assembled and poured at the job site, no …… of panels is required.

3. Because concrete tilt-up walls are poured …… , contractors are at the mercy of climatic conditions.

4. After curing, the precast concrete panels are …… to the job site.

5. Tilt-up concrete buildings are built in northern areas, but the window of time for temperate weather is much smaller and less …… .

6. Tilt-up or tiltwall construction and precast concrete are …… processes.

7. Tiltwall panels can sometimes be …… wide and/or tall.

8. One major …… of this is that the size of the panels is limited only by the needs of the building and the strength of the concrete panels.

9. For precast concrete buildings, work …… do not set up forms at the job site to create the panels.

10. Because tilt-up affords more …… , it is the method of choice in locations where the weather allows it.

UNIT 20 Concrete Curing Compounds

Read, translate the following text and be ready to fulfil the tests:

Need for curing. The necessity for curing arises from the fact that hydration of cement can take place only in water-filled capillaries. That is why a loss of water by evaporation from the capillaries must be prevented. Evaporation of water from concrete, soon after placing, depends on the temperature and, relatively, humidity of the surrounding air and on the velocity of wind over the surface of the concrete. Curing is essential in the production of concrete to have the desired properties. The strength and durability of concrete will be fully developed only if it is properly cured. The amount of mixing water in the concrete at the time of placement is normally more than required for hydration & that must be retained for curing. However, excessive loss of water by evaporation may reduce the amount of retained water below what necessary for development of desired properties. The potentially harmful effects of evaporation must be prevented either by applying water or preventing excessive evaporation.

Curing method. The two systems of maintaining a satisfactory moisture content are: (1) continuous or frequent application of water through ponding, sprays, steams, or saturated cover materials such as burlap or cotton mats, rugs, earth, sand, sawdust and straw. (2) prevention of excessive loss of water, from the concrete, by the application of a membrane forming curing compound to the freshly placed concrete.

Water curing .Curing by water is one of the most efficient ways for curing concrete. The curing should begin as soon as possible after the casting of concrete. Any delay in curing will lead to evaporation of mixing water, and the early drying may lead to shrinkage and cracking of concrete. However, in practice, on some construction sites regular supply of potable water for curing may not be available or it may be inconvenient and expensive. To such sites, concrete curing compound is recommended in place of water curing. Concrete curing compound consists essentially of waxes, natural and synthetic resins, and solvents of high volatility at atmospheric temperatures. The compound forms a moisture retentive film shortly after being applied on fresh concrete surface. White or gray pigments are often incorporated to provide heat reflectance, and to make the compound visible on the structure for inspection purpose. Curing compound should not be used on surfaces that are to receive additional concrete, paint, or tile which require a positive bond, unless it has been demonstrated that the membrane can be satisfactorily removed before the subsequent application is made, or that the membrane can serve satisfactorily as a base for the later application. Curing compound can be used with advantage where wet curing is not possible. It is very suitable for large areas of concrete which are directly exposed to sunlight, heavy winds and other environmental influences. It can be used for curing of:

•Concrete pavements, airport runways, bridge decks, industrial floors.

•Canal linings, dams and other irrigation related structures.

•Sport arenas and ice rings.

•Precast concrete components.

•Roof slabs, columns and beams.

•Chimneys, cooling towers and other tall structures.

Read and memorize the active vocabulary to the text: