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Construction Materials 2026 > Aggregate > Flashcards

Aggregate Flashcards

(47 cards)

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1
Q

Aggregate

A

Any hard, inert material composed of fragments in a wide range of sizes. Can be natural or manufactured.

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2
Q

Size distribution

A
  • As fine as 5 microns

- As large as 150 mm

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3
Q

Natural Aggregates

A

Breakdown of large rock masses

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4
Q

What are the 3 basic types of aggreagtes

A
  1. Igneous
  2. Sedimentary
  3. Metamorphic
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5
Q

What are some sources of aggregates?

A
  1. Gravel pits
  2. River run deposits
  3. Rock quarries
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6
Q

Where does gravel generally come from?

A

Pits and rivers deposits

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7
Q

What are crushed stones?

A

The result of processing rocks from quarries

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8
Q

How are lightweight aggregates produced?

A

Expanded shale and clays

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9
Q

Is Styrofoam Beads used as an aggregate? Yes or no and state why it is used?

A

Yes, for insulation

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10
Q

Which aggregates are used for heavyweight concrete and what are they used for?

A

Steel slugs and bearings for radiation shields

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11
Q

What other materials could potentially be used as aggregates?

A

Glass and recycled concrete

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12
Q

What can be done to increase the tensile strength of aggregate

A

Fibre

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13
Q

Can we recycle aggregates? Applications?

A

Yes! Concrete and tires( affects concrete, but very elastic

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14
Q

The physical and chemical properties pf the rocks determine what?

A

The acceptabillty of an aggregate source for a construction project. Due to it’s varying characteristics, samples must be continually tested as the aggregates are being produced.

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15
Q

How are aggregates evaluated?

A
  1. Quality of the larger pieces
  2. The nature and the amount of fine material
  3. The gradation of the aggregate
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16
Q

What are two main uses of aggregates in C.Eng?

A
  1. Underlying material for foundations and pavements

2. Ingredients in portland Cement Concrete (PCC) and Asphalt Concretes

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17
Q

What properties should an aggregate have to be used as part of a road sub-base? What about as part of a regular Portland Cement Concrete mix?

A
  • impact resistance
  • compressive strength
  • moisture content
  • gradation
  • porostiy
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18
Q

In PCC, what percentages of volume and weight is made up of aggregates?

A

In Portland Cement Concrete, 60-75% of volume and 70-85% of weight is made up of aggregates.

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19
Q

Why does aggregate act as a filler?

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A

To reduce amount of cement paste ($$$) needed in the mix

20
Q

Does aggregate generally have greater volume stability than the cement paste?

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A

Yes! Because cement is just a paste

21
Q

What does the Strength and Stability of asphalt cement concrete depend on?

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A

Inter-particle friction between the aggregates

22
Q

Particle shape determines what?

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A

Determines how the material will pack into a dense configuration and the mobility of the stones within a mix

23
Q

What is angularity?

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A

Crushed rocks produce angular particles with sharp corners

24
Q

Define Flakiness

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A

Describes the relationship between the smallest and the largest dimension of the aggregate

25
State a pro and a con for angular aggregates?
High Stability then round aggregates, but more difficult to work into place!
26
Are rough texture aggregates more difficult to compact than smooth aggregates? Why, explain?
Yes due to interparticle friction
27
Why are rounded and smooth aggregates particles more desirable than rough aggregates?
They increase workability
28
Why is angular and rough particles desirable for asphalt concrete and base courses?
To increase stability and reduce rutting (environmental effect on material)
29
Flaky and elongated aggregates are undesirable for what reason?
They are difficult to compact and easy to break
30
The ability of an aggregate to withstand weathering is _______ or _______
Soundness or durability
31
What is Abrasion resistance and what does it resist?
Ability of an aggregate to resist damaging effect of loads; the aggregates must resist crushing, degradation and disintegration
32
Tensile strength range?
0.7-16 MPa (100 to 2300 psi)
33
Compressive strength range:
35-350 MPa (5000-50,000 psi)
34
Can Aggregates capture water and asphalt binder in surface voids?
Yes!
35
Why must absorption be evaluated?
To determine the appropriate amount of water to mix into the concrete
36
Highly absorptive aggregates require greater amounts of asphalt binder the mix less ______?
Economical
37
What is Simplified Soil Particle?
- Consists of solid materials with some pores and voids. | - Relate WEIGHT and VOLUME aggregate particles
38
What the four types of moisture states?
- Oven-Dry (OD) - Air Dry (AD) - Saturated Surface Dry (SSD) - Wet
39
What is Oven Dry?
All moisture is removed from the aggregate by heating in an oven at 105.
40
What is Air dry?
All moisture from the surface is removed, but internal pores are partially full
41
What is Saturated Surface Dry?
All pores filled with water, but no film of water on the surface
42
What is Wet?
All pores completely filled with water with a film on the surface
43
Of the four which two correspond to specific moisture content?
OD and SSD
44
Why is the SSD state the best choice as a reference state?
- represents "equilibrium moisture"; aggregate will neither absorb water nor give up water to the paste. - moisture content of aggregates is much closer to SSD state than the OD state - Bulk Relative Density (BRD) is more accurately determined by the displacement method in the SSD condition.
45
What is absorption capacity?
The max amount of water the aggregate can absorb. Equation: AC = (Wssd - Wod) / (Wod) x 100%
46
Effective Absorption:
The amount of water required to bring an aggregate from the AD state to SSD. Equation: EA: (Wssd- Wad) / (Wad) x 100%
47
Surface moisture:
Represents water in excess of the SSD state Equation: SM = (Wwet-Wssd) / (Wssd) x 100%

Construction Materials 2026 (1 decks)

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