bcds 1

Question 1

In this test, a 2 in (51) diameter sampler is driven into the bottom of the borehole by a 140 lbm (63 kg) hammer falling 30 in (760). The number of blows, N, required to drive the cylinder 12 in (305) is recorded.

Answer 1

standard penetration test SPT

Question 2

is used to form continuous surfaces such as tunnels and high-rise building cores. The entire form is constructed along with working platforms and supports for the jacking assembly

Answer 2

slip forming

Question 3

are large fabricated sections of framework that are removed, once the concrete has cured, to be reused in forming an identical section above. They are often used in buildings with highly repetitive units, such as hotels and apartments.

Answer 3

flying forms

Question 4

perm of a vapor barrier

Answer 4

.04 perm

Question 5

are metal wire devices placed on the form to hold the rebars above the bottom of the form at the proper distance.

Answer 5

chairs

Question 6

is the binding agent in concrete. It is made from lime, silica, iron oxide, and alumina under strictly controlled conditions.

Answer 6

portland cement

Question 7

Generally, for complete hydration to occur, an amount of water equal to –% · of the weight of the cement is required.

Answer 7

25%, An extra 10% to 15% or more is required to make a workable mix.

Question 8

This is a chalky surface deposit of low-strength concrete.

Answer 8

laitance

Question 9

Typically, aggregates occupy about —- of the total volume of the concrete.

Answer 9

70% to 75%

Question 10

are chemicals or other materials added to concrete to impart certain qualities.

Answer 10

admixtures

Question 11

form tiny, dispersed bubbles in the concrete. These agents increase the workability and durability of the concrete and improve its resistance to freezing and thawing cycles. They also help reduce segregation of the components during placing of the mix into forms.

Answer 11

air-entraining agents

Question 12

educe the amount of water needed while maintaining the necessary consistency for correct placement and compaction. Reducing the water, of course, makes it possible to mix higher- strength concrete.

Answer 12

plasticizers

Question 13

is a waste material obtained from coal fired power plants. It is used in concrete to increase strength, decrease permeability, reduce temperature rise, increase sulfate resistance, and improve workability. It can also be used to decrease the total amount of cement needed.

Answer 13

fly ash

Question 14

is a precast concrete product manufactured by adding aluminum powder to concrete, hardening it in molds, and then curing the molds in a pressurized steam chamber. The resultant blocks have about one-fifth the density of conventional concrete.

Answer 14

Autoclaved aerated concrete(AAC)

Question 15

is a concrete mixture that can be placed purely by means of its own weight without the use of vibration.

Answer 15

self consolidating concrete SCC

Question 16

Concrete can even be placed underwater with a long, cylindrical steel chute called a

Answer 16

tremie