BDC - General

Question 1

what are the 4 types of soils?

Answer 1

Sands, Gravels, Silts & Clays

Question 2

What are the two types of soils that are best suited for foundations?

Answer 2

Sands & Clay

Question 3

why is clay unpredictable?

Answer 3

It swells when it absorbed water and shrinks when it dries.

Question 4

what is Hardpan

Answer 4

it refers to an unbroken mixture of clay, sand and gravel. Its a good base for building foundations.

Question 5

What is bedrock?

Answer 5

Its a solid rock that forms the earths crust. Bedrock has the highest baring capacity of all soil types.

Question 6

what are the two most common soils tests method for finding bearing capacity?

Answer 6

Borings and test pits

Question 7

what is the max spacing for sewer manholes?

Answer 7

500’

Question 8

what is the recommended expansion joint spacing in conc slabs?

Answer 8

20’

Question 9

what is the Control Joint spacing on a conc. walk?

Answer 9

5’

Question 10

What did John Smeaton found?

Answer 10

he found in the late 18th c. that quicklime containing clay would harden underwater.

Question 11

what were significant works by Pier Luigi Nervi?

Answer 11

Exhibition Building in Turin and Sports Palace in Rome.

Question 12

for columns what is the acceptable tolerances?

Answer 12

1/4” / 10’

Question 13

for slabs what is the acceptable tolerances?

Answer 13

1/8” / 10’

Question 14

what is a necessary element for slabs on grade?

Answer 14

install a vapor barrier. it prevents moisture migration

Question 15

what is a vapor retarder?

Answer 15

it only slows the rate of water vapor transmission.

Question 16

what is a perm?

Answer 16

Permeance: its the measure of a materials resistance to water-vapor transmission. Its the passage of one grain of water vapor per hour through one square foot of material at an equatable pressure on both sides.

Question 17

what are rebar grades?

Answer 17

common grades are 40 & 60. the number refers to the yield strength in kips per square inch.

Question 18

what is guage sizing system for welded wire fabric?

Answer 18

first numbers is the (inches) square of the spacing of the wire. the W__ means the area in hundredths of the guage. eg W1.4 = .014in2

Question 19

what makes up portland cement?

Answer 19

its made from lime, silica, iron oxide and alumina.

Question 20

what are the 5 different types of cement?

Answer 20

Type 1: is standard cement f
Type 2: modified cement its used in place where modest amounts of sulfate resistance is needed and where hydration needs to be controlled (damns)
Type 3: High Early strength and is used where a quick set is needed. Also used in cold climates.
Type 4: used to minimize cracking in big structures. and is called low heat.
Type 5: is sulfate resisting cement & is used when in contact with high alkaline soils etc.

Question 21

for most concretes what is the minimum water to cement ratio?

Answer 21

.35 to .4. It works out to 4gal to 4.5 gal/ 94lb sack of cement.

Question 22

what % of volume do aggregates occupy in concrete?

Answer 22

70 to 75%

Question 23

what is proportioning (concrete)?

Answer 23

its the ratio of cement to sand top gravel.

Question 24

in concrete what is plasticizers?

Answer 24

they reduce the amount of water needed while maintaining the necessary consistency for correct placement & compaction.

Question 25

in concrete what are retarders?

Answer 25

they slow down the setting time to help reduce the heat of hydration.

Question 26

what are waterproofing agents in concrete?

Answer 26

they decrease the permeability of the concrete.

Question 27

in concrete what is fly ash?

Answer 27

its waste material from coal fired power plants and its used to increase the strength and decrease the permeability .

Question 28

how does concrete gain strength?

Answer 28

by curing through a chemical reaction between the water and the cement. If concrete dries too fast, it can lose strength, up to 30%.

Question 29

what is a slump test in concrete?

Answer 29

it measures the consistency of the concrete. In this test concrete is placed in a 12in high truncated cone, 8in at the base and 4in at the top. its compacted by hand with a rod. and then mold is removed from the concrete and placed next to it. The distance the conc. slumps from the original 12in height is then measured in inches. To much slump indicates excessive water, little slump indicates that the mix will be difficult to place properly.

Question 30

What is the cylinder test in concrete?

Answer 30

it measures compressive strength. As the concrete is being placed, samples are put in cylinder molds that are 6in in dia & 12in high and are moist cured & tested . The compressive strength in lbs / sq in is calced & composed.

Question 31

what is a core cylinder test?

Answer 31

it is used when a portion of the structure is in placed & cured but needs to be tested. A cylinder is drilled out & tested in a lab to determine its compressive strength.

Question 32

in concrete what is the Kelly Ball test?

Answer 32

a circular ball mass of steel is dropped onto a fresh slab & the amount of penetration of the ball intpo the concrete is measured & compared to one-half the values of the slump test.

Question 33

in concrete what is the impact hammer test.

Answer 33

its a nondestructive way to test concrete strength after it has hardened. A spring-loaded plunger is snapped against a concrete surface, and the amount of rebound is measured. The amount of rebound gives an approximate reading of the concrete strength, If this this is not accurate enough, then cylinder cores can be cut from hardened concrete & tested in the lab.

Question 34

what are 3 types of asbestos?

Answer 34

Chrysotile. amosite, Crocidolite

Question 35

what are ways to minimize asbestos for removal?

Answer 35

wet methods, HEPA vacuum, Area isolation, avoid sanding or sawing.