Deck 7: Concrete

Question 1

What does a unit weight test involve and what does it determine?

Answer 1

The unit weight test involves weighing a properly consolidated specimen in a calibrated container following ASTM C138 standards. It can determine the quantity of concrete produced per batch and give indications of air content.

Question 2

What does a gas-forming agent do when added to concrete?

Answer 2

Gas-forming agents are added to concrete or grout to cause a slight expansion in it before it hardens. Aluminum powder, one of several gas-forming agents in use, reacts with the hydroxides in hydrating cement and produces small hydrogen-gas bubbles. This also helps eliminate voids caused by settlement of the concrete or grout. A typical application consists of expanding the grout under a difficult-to-reach machine base or column to be certain the area is fully grouted. After concrete or grout has hardened, gas-forming agents will not overcome shrinkage. When they are used in large amounts, gas-forming agents produce lightweight cellular concrete.

Question 3

____ admixtures reduce the amount of water needed to produce concrete of a given consistency.

A) Retarding
B) Air entraining
C) Water-reducing
D) Pozzolan

Answer 3

C

Question 4

Describe environmental pollution concerns associated with Portland cement and some possible solutions.

Question 5

What are heavyweight aggregates, for what purpose are they used, and what are some examples of those frequently used?

Question 6

Describe resistance to abrasion and skidding as it relates to aggregates.

Question 7

The ____ test is used to ascertain the resistance to wear of hardened concrete samples.

A) freeze-thaw
B) curring
C) abrasion
D) compressive strength

Question 8

The ____ test is used to determine the water and cement content of fresh concrete.

A) slump
B) cement content
C) air-content
D) unit weight

Question 9

What do water reducing admixtures do and what are some examples of agents?

Question 10

____ is a measure of the relative density of an aggregate.

A) Specific gravity
B) Compressive strength
C) Freeze resistance
D) Absorption rate

Question 11

How is a freeze-thaw test performed and what does it determine?

Question 12

____ is a measure of the amount of water that passes through channels running between the outer faces of the concrete.

A) Bonding ability
B) Hardening ability
C) Workability
D) Permeability

Question 13

A(n) ____ admixture speeds up the strength development of concrete.

A) pozzolan
B) water reducing
C) accelerator
D) retarding

Question 14

When should entrained air be used and what does it do to concrete?

Question 15

A ____ test requires that a steel rod with an enlarged end be cast in the concrete.

A) rebound
B) vibration
C) penetration
D) pull-out

Question 16

____ agents are added to concrete or grout to cause a slight expansion in it before it hardens.

A) Gas-forming
B) Grouting
C) Hardening
D) Bonding

Question 17

Describe Type II Portand cement.

Question 18

____ admixtures are used to entrain microscopic air bubbles in concrete.

A) Retarding
B) Air-entraining
C) Water reducing
D) Pozzolan

Question 19

Briefly describe how concrete is made and describe its beneficial properties.

Question 20

Type ____ Portland cement is used only in concrete that is exposed to severe sulfate conditions.

A) IIA
B) III
C) IV
D) V