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Construction Materials 2026 > Aggregate > Flashcards

Aggregate Flashcards

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?

A

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

20
Q

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

A

Yes! Because cement is just a paste

21
Q

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

A

Inter-particle friction between the aggregates

22
Q

Particle shape determines what?

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?

A

Crushed rocks produce angular particles with sharp corners

24
Q

Define Flakiness

A

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

25
Q

State a pro and a con for angular aggregates?

A

High Stability then round aggregates, but more difficult to work into place!

26
Q

Are rough texture aggregates more difficult to compact than smooth aggregates? Why, explain?

A

Yes due to interparticle friction

27
Q

Why are rounded and smooth aggregates particles more desirable than rough aggregates?

A

They increase workability

28
Q

Why is angular and rough particles desirable for asphalt concrete and base courses?

A

To increase stability and reduce rutting (environmental effect on material)

29
Q

Flaky and elongated aggregates are undesirable for what reason?

A

They are difficult to compact and easy to break

30
Q

The ability of an aggregate to withstand weathering is _______ or _______

A

Soundness or durability

31
Q

What is Abrasion resistance and what does it resist?

A

Ability of an aggregate to resist damaging effect of loads; the aggregates must resist crushing, degradation and disintegration

32
Q

Tensile strength range?

A

0.7-16 MPa (100 to 2300 psi)

33
Q

Compressive strength range:

A

35-350 MPa (5000-50,000 psi)

34
Q

Can Aggregates capture water and asphalt binder in surface voids?

A

Yes!

35
Q

Why must absorption be evaluated?

A

To determine the appropriate amount of water to mix into the concrete

36
Q

Highly absorptive aggregates require greater amounts of asphalt binder the mix less ______?

A

Economical

37
Q

What is Simplified Soil Particle?

A
  • Consists of solid materials with some pores and voids.

- Relate WEIGHT and VOLUME aggregate particles

38
Q

What the four types of moisture states?

A
  • Oven-Dry (OD)
  • Air Dry (AD)
  • Saturated Surface Dry (SSD)
  • Wet
39
Q

What is Oven Dry?

A

All moisture is removed from the aggregate by heating in an oven at 105.

40
Q

What is Air dry?

A

All moisture from the surface is removed, but internal pores are partially full

41
Q

What is Saturated Surface Dry?

A

All pores filled with water, but no film of water on the surface

42
Q

What is Wet?

A

All pores completely filled with water with a film on the surface

43
Q

Of the four which two correspond to specific moisture content?

A

OD and SSD

44
Q

Why is the SSD state the best choice as a reference state?

A
  • 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
Q

What is absorption capacity?

A

The max amount of water the aggregate can absorb.

Equation:

AC = (Wssd - Wod) / (Wod) x 100%

46
Q

Effective Absorption:

A

The amount of water required to bring an aggregate from the AD state to SSD.

Equation:

EA: (Wssd- Wad) / (Wad) x 100%

47
Q

Surface moisture:

A

Represents water in excess of the SSD state

Equation:

SM = (Wwet-Wssd) / (Wssd) x 100%

Construction Materials 2026 (1 decks)

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