120 Section 2 Construction Materials
Summary
Concrete is made by mixing Portland cement, fine and coarse aggregate,
and water. Admixtures can be used to change the characteristics of concrete.
Steel reinforcing bars are used to improve the tensile strength of concrete.
The quality of concrete is determined by the materials from which it is made,
the way it is mixed, how it is placed and finished, and the curing procedures
employed.
Concrete forms need to be level and well braced. The inside of the
form should be clean and coated to aid in form removal. Concrete should
be placed in the forms carefully to avoid segregation of fine and coarse
aggregate. Consolidating removes air pockets and voids. Finishing involves
screeding, darbying, edging, jointing, and troweling. Curing, the final step,
requires time, above-freezing temperatures, and the presence of moisture.
T
est
Y
our
Knowledge
Write your answers on a separate piece of paper. Do not write in this book.
1. List the three ingredients in concrete.
2. What type of Portland cement is used to make concrete that cures
quickly?
3. In the Western United States, soils tend to contain
______,
so Type V
Portland cement is often used when mixing concrete.
4. The
______
in concrete consists of fine sand and stones.
A. admixture
B. mixture
C. aggregate
D. None of the above.
5. True or False? Air-entrained concrete contains an admixture that causes
small air bubbles to form in concrete.
6. Steel reinforcing bars increase the
______
strength of concrete.
7. Name four important properties of concrete.
8. List four factors that determine the quality of concrete.
9. Devices that maintain and control the thickness of a concrete wall are
known as
______.
10. What formula is used to calculate cubic yards?
11. True or False? Moving fresh concrete a long distance does not cause any
problems with the concrete.
12. For concrete to cure,
______
must be present.
13. The results of a
______
test indicate the workability of a batch of
concrete.
A. slump
B. compression
C. strength
D. smoothness