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Concrete Flashcards

(49 cards)

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1
Q

what are some of the raw materials in Portland Cement

A
  • limestone
  • cement rock
  • oyster shells
  • marl (lime rich mud-lake sediment)
  • clay
  • silica sand
  • iron ore
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2
Q

Raw materials are ground down and heated to temperatures between ______ and ______ degrees (F) to form hard pellets called “_____”

A

2,000 and 3,000

Clinkers

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3
Q

what is air entrainment

A

the intentional creation of tiny air bubbles in concrete

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4
Q

what is the composition of concrete

A

mix of aggregates and entrained air held together by hardened paste made of cement and water

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5
Q

what is the most commonly used cement by the military

A

portland cement

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6
Q

what is the chemical reaction when portland cement is mixed with water

A

hydration

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7
Q

what causes concrete to harden and what is the desired temp.

A

hydration and 73 degrees

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8
Q

what are the three major components of concrete

A
  • water
  • aggregates
  • portland cement
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9
Q

what are two types of aggregate

A

coarse (rock) and fine (sand)

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10
Q

what is the primary purpose of aggregates in concrete

A

to gain economy

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11
Q

what is the total percent of volume in concrete

A

60 to 80 percent

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12
Q

what are the most common contaminating materials of aggregate

A

dirt, clay and salt

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13
Q

what are the five types of portland cement

A
  • type 1: normal portland
  • type 2: modified
  • type 3: high early
  • type 4: low heat
  • type 5: sulfate resistant
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14
Q

what is the normal cure time and some uses of type 1 portland cement

A

28 days

pavement, sidewalks, bridges

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15
Q

what is the normal cure time and uses of type 2 portland cement

A

45 days

large super structures, large piers

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16
Q

what is the normal cure time and uses of type 3 portland cement

A

7 days

used in cold weather and high heat

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17
Q

what is the normal cure time and uses of type 4 portland cement

A

90 days

large massive structures

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18
Q

what is the normal cure time and uses of type 5 portland cement

A

60 days

used where the soil, or water, in contact with the concrete has a high sulfate content

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19
Q

what types of portland cement are air entrained

A

types 1, 2 and 3

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20
Q

what does calcium chloride do to portland cement

Study These Flashcards
A

accelerates both hardening and strength gain by 2 percent the weight of cement 2 hrs vs 6 hrs

21
Q

how does portland cement ship

Study These Flashcards
A

bags- 94lbs, contain one cu ft of loose measurement

barrels- 376 lbs = four bags

rail cars

22
Q

what is “warehouse pack”

Study These Flashcards
A

sacked cement in storage packed too tightly

23
Q

what are the types of concrete

Study These Flashcards
A
  • reinforced
  • prestressed
  • precast
  • lightweight
24
Q

what is reinforced concrete

Study These Flashcards
A

when steel rods are embedded in the concrete

25
what is prestressed concrete
steel or welded wire mesh that is strecthed out with tension before the concrete is poured
26
what is precast concrete
concrete cast into something other than its final position
27
what does a good "plastic state" for concrete mean
* readily moldable * changes shape slowly if forms are removed * uniform
28
what are some advantages of concrete
* high compressive strength * can be cast, molded or shaped * little maintenance * durable
29
what are some disadvantages of concrete
* low tensile strength * expands and contracts * shrinks when dry * heavy
30
expansion joints should never be less than ____ in wide
1/4 inch
31
what is the difference between construction joints and e​xpansion joints
construction joints do not allow for movement and expansion joints do
32
if concrete must be placed underwater, what should the max velocity of the current be
ten ft per min
33
when hand mixing cement, one man can mix approx. _______ cu yd per hour
one
34
when hand mixing concrete the sand, gravel and cement should be dry mixed how many times before adding water
three times
35
what is the formula for Project Volume (PV)
PV= Length x width x depth x # of structures, make sure to convert for inches
36
what is the formula for Loss Factor (LF) for cu ft
LF= PV x LF (\<5400 cu ft x 1.1 , \>5400 cu ft x 1.05)
37
what is the formula for Loose Volume (LV)
LV= LF amount x 1.5
38
what rule do you use when calculating for materials when laying concrete
1-2-3 rule 1/6 cement 2/6 sand 3/6 gravel
39
how do you convert cu ft to cu yrds
cu ft/27 = cu yards
40
how do you convert cu yrds to cu ft
cu yards x 27 = cu ft
41
when estimating for concrete work what is the rule called
the 3/2 rule
42
what is the formula for **Loss Factor (LF)** for cu yards
LF= PV x LF(\<200 cu yards x 1.1 or \>200 cu yards x 1.05)
43
**forms** can represent up to ___ of conrete scructure's total cost
1/3
44
**forms** are generally made of what four materials
* wood * fiber * earth * metal
45
what are the elements of **wooden forms** (concrete wall)
* sheathing * studs * wales * strong backs * braces * shoe plates * spreaders * tie wires
46
what are the elements of wooden forms (concrete column)
* sheathing * batten * yokes * bracing
47
the rate of filling should not exceed ____ ft per hour vertically, to avoid over-pressure on the forms
4 ft per hour
48
what is **screeding**
the process of _striking_ off the excess concrete in order to bring the surface to the right elevation
49
what will produce a smoother finishing surface ## Footnote **floating or troweling**
troweling will be smoother

Concrete (1 decks)

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