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LARE Section 4 > Materials > Flashcards

Materials Flashcards

1
Q

Expected Asphalt Pavement Life

A

20 years for surface maintenance or resurfacing overlays when properly constructed
Durability factors: traffic volume, quality of construction, frequency of maintenance, severity of climate, and the quality of the materials involved

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2
Q

Full-Depth design
Asphalt pavement construction

A

Asphalt concrete or asphalt aggregate placed directly on a subgrade without an aggregate base

Subgrade should be finished to uniform grade and compacted at or near optimum moisture level
If plastic, wet soil, replace soil 4in+ with untreated, coarse aggregate

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3
Q

Aggregate base design
Asphalt pavement construction

A

Asphalt concrete or asphalt-aggregate mixture that is placed on an untreated aggregate base over a prepared subgrade.
Most appropriate in areas where soils are highly susceptible to frost action
The prepared base and subbase aggregate layer minimizes frost heave and helps distribute the imposed loads, allowing for a slightly thinner base coarse of asphalt concrete or asphalt-aggregate mixture than is necessary in full-depth design
Untreated aggregate base and sub base should be compacted at or near optimum moisture levels

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4
Q

Minimum total thickness of combined asphalt concrete layers in a pavement designed to carry very light loads (walkways, playgrounds)

A

3-4 in.

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5
Q

Subgrade requirements for asphalt pavement

A

- stable and designed to minimize possible heaving due to frost
- adequate compaction to ensure maximum strength and bearing potential
- good drainage, reasonably and informally dry so localized poor drainage does not affect strength
- subgrades should drain parallel to pavement surface

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6
Q

When granular materials are unsuitable for base courses, because of issues like poor interlocking ability, they can be treated with a

A

Stabilized base course
Bituminous stabilization

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7
Q

Needs of top surface of asphalt

A

- smooth
- resistant to wear
- distortion
- deterioration by weathering and deicing chemicals

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8
Q

To allow for expansion of the pavement and compaction of the aggregate over time, what percent voids by volume should a finished asphalt concrete pavement contain?

A

2-7%

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9
Q

What is the purpose of voids in finished asphalt concrete pavement?

A

To allow for expansion of the pavement and compaction of the aggregate over time

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10
Q

Ratio of thickness of any layer of asphalt concrete to aggregate

A

Twice the nominal maximum size (or maximum particle size) of aggregate

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11
Q

What are surface treatments used for?
Asphalt

A

Color coating, sealing, improving skid resistance, or prolonging the service life of a fair to good pavement surface

Laid in 1 in. thickness
They do not increase structural strength

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12
Q

What do block pavements require?

A

Base course
Subbase course
Some type of edging for containment

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13
Q

Typical compacted thickness of asphalt concrete

A

3/4 in. to more than 1 ft.

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14
Q

Asphalt concrete consists of

A

Dense graded aggregate heated to 300F
Then mixed with asphalt cement heated to 275F
Heated mixture taken to site to be placed

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15
Q

Selection criteria for aggregates

A

1. Hardness (toughness) - ability to withstand loads and wear
2. Resistance to stripping - hydrophilic aggregate strip away from asphalt bond, reducing stability and skid resistance of pavement. Anti-stripping compounds can be added
3. Surface texture - rough texture aids in bonding and makes pavement more stable and resistant to abrasion and skidding
4. Crushed shape - cubic, angular, crushed shapes interlock and give pavement more strength than do smooth, rounded aggregate

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16
Q

Properties of Asphalt Cement or Binder

A

Thermoplasticity
Viscosity and Grades
Weathering
Insolvency
Color

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17
Q

Thermosplasticity

A

Asphalt cement or binder is an adhesive which deforms under loads or liquefies with heat. These properties cause it to be classified as a flexible type of pavement.

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18
Q

Viscosity and Grades

A

The viscosity of asphalt is directly influenced by temperature. A temperature/viscosity slope can be plotted to define the temperature for mixing and compaction. An increase in temperature means a decrease in viscosity.

Asphalt cement or binder can have grades of hardness or viscosity. Each grade is intended for specific purposes.

There are three different methods for grading asphalt cement or binders used in the US and Canada. All three grade asphalt according to degree of hardness.

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19
Q

Weathering

A

The oxidation of the surface and the evaporation of lighter hydrocarbons (volatilization) causes asphalt to lose its plasticity and to become brittle with age.
Properly sloped subbases and subgrades, proper compaction of layers, and timely sealing and surfacing treatments keep weathering to a minimum.

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20
Q

Insolvency

A

Asphalt is resistant to the chemical effects of water and of most salts, acids, and alkali’s except petroleum-based materials, such as gasoline and oil-based paints if applied on concentrated amounts. Tar dealers are used on a asphalt surface where concentrated spillage is expected.

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21
Q

Color

A

Asphalt is naturally black, but certain proprietary products or paving processes can alter that color.

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22
Q

Sizes of aggregate for asphalt pavements

A

Fine aggregate
Coarse aggregate
Macadam aggregate

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23
Q

Fine aggregate

A

Aggregate that passes the 2.36 mm (No. 8) sieve.
Mineral dust refers for to the portio ,of fine aggregate that passes the 0.075 mm (No. 200) sieve, and mineral filler refers to that portion of fine aggregate that passes the 0.60 mm (No. 30) sieve.
Mineral dust and mineral filler are typically used in precise percentages to fill voids of coarse aggregate to produce a cohesive, dense, water-tight asphalt concrete mixture

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24
Q

Coarse aggregate

A

Aggregates retained to the 2.36 mm (No. 8) sieve.
The interlocking and friction of coarse aggregates provide the major stability function in a pavement.

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25
Q

Macadam Aggregate

A

This refers to coarse aggregates of uniform size, nominally sized between 40 to 65 mm (1- 1/2 to 2- 1/2 in.), usually of crushed stone, slag, or gravel.
Such aggregate is typically used in macadam construction.
Macadam construction mixes asphalt cement with the aggregates to form an inexpensive coarse wearing surface.

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26
Q

Maximum particle or stone size

A

Smallest sieve that 100 percent of the aggregates will pass

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27
Q

Nominal maximum size

A

Largest sieve that retains any of the aggregates
But generally not more than 10 percent of the larger-size aggregates

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28
Q

Four common aggregate gradations

A

(Asphalt mixtures are commonly referred to by their nominal maximum size)

Fine-graded aggregate
Coarse-graded aggregate
Dense-graded (well-graded) aggregate
Open-graded aggregate

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29
Q

Fine-graded aggregate

A

Produces a surface of finer texture and less road noise than a coarse aggregate

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30
Q

Coarse-graded aggregate

A

Produces a more stable with coarser surface texture and, therefore, more road noise.

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31
Q

Dense-graded (well-graded) aggregate

A

Produces a surface that is very watertight, highly stable, and durable

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32
Q

Open-graded aggregate

A

Contains little or no mineral filler, therefore, its larger aggregates create larger voids which interlock and produce a pavement with good strength, rough texture, and high permeability.
This pavement is suitable for porous drainage pavements located in regions free of frost/thaw conditions.

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33
Q

Recycled glass as aggregate

A

Required for use by some federal projects

Glass must be carefully ground and rolled to minimize sharp edges that may become exposed with gradual wearing.

Recycled glass works well in asphalt pavements of heavy use, such as roadways, because constant wearing continually grinds the glass edges.
Lighter uses, such as bicycle paths, can gradually expose the glass and increase the chances of sharp edges coming to the surface.

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34
Q

Climate and Asphalt

A

Severely cold temperatures may require very soft asphalt to minimize cracking

Very hot climates require harder asphalt to maintain stiffness and resist rutting

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35
Q

The larger the size of aggregates in a gradation

A

The greater will be the strength and durability of the pavement
Larger aggregates result in rougher pavement (or surface texture) than do gradations with finer aggregate
The greater the road noise generated by vehicular traffic
The color of a weathered asphalt pavement is also a function of the color of the larger aggregates

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36
Q

Thickness of asphalt concrete for roads

A

1. traffic weight and number of vehicles: the heavier and/or more numerous the load, the thicker the pavement required.
2. Subgrade support: weaker subgrades require stronger pavement design. The use of a strong aggregate subbase to achieve desired strength is recommended rather than thicker and/or more layers of asphalt concrete
3. Materials in the pavement structure: hot-mix asphalt concrete gives more strength and the aggregate base distributes loads better than a full-depth design

37
Q

Thickness design procedure - roads

A

1. Classify the traffic
2. Classify the subgrade
3. Determine the optimum asphalt concrete specifications of the local governing authority responsible for asphalt pavement specifications. If these are not available, determine the optimum asphalt cement and aggregate combination, considering the proposed load and subgrade. Any untreated aggregate should meet ASTM D2940) requirements. The subgrade should be compacted at or near optimum moisture content to achieve maximum density. The bases and subbases should also be compacted at optimum moisture content to achieve a minimum density of 100 percent maximum laboratory density.
4. Determine the thickness

38
Q

Bike paths and walkways

A

Total asphalt concrete thickness of 3-4 in. in a full-depth or untreated aggregate base design

39
Q

Golf cart paths

A

Require a softer surface to minimize golf shoe spike wear.
Similar to bike path/walkway construction, but the surface course should be a sand-asphalt mixture with an asphalt content slightly higher than for normal highway paving.
Alternatively, an open graded mix may be used as a surface course.

40
Q

Tennis courts

A

Require a higher degree of smoothness with a maximum irregularity of 3mm (1/8 in) over a 3-m (10-ft) distance.
Achieved with asphalt concrete base of 20mm (3/4 in.) of nominal maximum size designation covered either with sand-asphalt for surface course or with proprietary surfacing.
Base course is 3in. And surface course is 1in. creating a minimal total thickness of 4in.
If sand-asphalt is used, a latex paint of minimum thickness should be used no sooner than 30 days after construction.

41
Q

Playgrounds and Recreational Areas

A

Same as those for tennis courts
Asphalt concrete can serve as base for proprietary products like sealers, color coats, resilient surface coatings, and artificial turf.
The asphalt concrete can be molded on a prepared subgrade to produce any desired gradient. Erosiónala undermining of pavement edges should be prevented.

Combining a small percentage of cork with asphalt cement, sharp coarse sand, and limestone dust produces a resilient playground surface. Cork granules max. dia. size of 1/4 in.

42
Q

Asphalt curbs

A

Although not affected by snow- and ice-melting chemicals, asphalt curbs can be sheared off or deformed when struck by heavy loads.
Curbs should be back-filled with a solid granular material or well-compacted soil.
Set by a curbing machine at rate of 2000 fr per day.
Must be installed on top of a solid, impervious pavement that will not erode or fail.
Curbs are made of specially proportioned asphalt-aggregate mixtures.
Asphalt concrete berms are an alternative.

43
Q

Asphalt gutters

A

Formed in variety of cross sections.
Placed mostly by hand or on occasion by a small paving machine adapted for a particular job (for special large projects)

44
Q

Asphalt underlayments

A

For surface courses, including brick, stone block, and proprietary products.
Underpayment must fulfill remaining strength requirements.

45
Q

Colored Asphalt Pavements

A

Asphalt mixtures with higher amounts of finer sand and filler produce darker-tones. Dark color helps hide grease drippings, accelerates melting of snow, and provides a good background for the striping.

Additional color can be added through:
1. Paints and applied coatings used on tennis courts, pools, playgrounds, and bikeways. Only paints designed for use on asphalt pavements should be used. These are typically sprayed on. The paint and proprietary surface manufacturers recommendations should be followed.
Oil based paints should not be used.
2. Colored stone chips can be embedded in a single or a multiple surface treatment procedure. May require much handwork and should only be done by competent specialists. Precautionary measures are necessary to protect nearby objects from the splatter of the spray applicator. This method provides a very coarse surface texture.
3. Asphalt concrete can be composed of selected color aggregate and when the asphalt film wears off, there will be exposed the color of the aggregate. Smaller stone sizes 3/8in. are standard.
4. Asphalt block pavements with exposed colored aggregate are commercially available.

46
Q

Recycled asphalt granular base courses

A

Asphalt pavement can be recycled for use as base courses in pavement design.
The used asphalt pavement is ground into granular material by either an on-site grinder or at a recycling facility and trucked to the site.
Its use is similar to crushed rock.

47
Q

Concrete

A

Mixture of aggregate, Portland cement, water, and sometimes special admixtures

most outstanding qualities are strength, durability, stability, availability, adaptability, and, in most cases, its relatively low cost in terms of construction and lifetime maintenance

48
Q

Properties of concrete are determined by

A

1. the quality of its constituents, including type of cement used, soundness of aggregate used, relative proportion of coarse and fine aggregate, ratio of water to cement, and type and amount of any chemicals, admixtures, and other compounds added to the mix
2.skills used in placing, consolidating, finishing, and curing the concrete

49
Q

Five Major Properties to consider when producing finished concrete

A

Strength
Resistance to Freeze/Thaw and Deicing chemicals
Resistance to abrasion and wear
Reduction of water penetration
Control of setting time for concrete

50
Q

Concrete
Strength

A

Usually the first consideration (except for lightweight and insulating concrete)
Relative strength is function of type of cement and aggregate selected
Full strength reached after 28 days, continue to increase past if sufficient moisture is available

51
Q

Resistance to Freeze/Thaw and Deicing Chemicals

A

Can be increased by the use of an air-entraining agent
Admixtures may reduce, or enhance somewhat, the potential strength of the concrete mix

52
Q

Resistance to Abrasion and Wear

A

Can be increased if the concrete mix contains well-graded strong aggregate and is well-consolidated when placed.
For some purposes, special aggregate and finishes may be required.
Finishing procedures are extremely critical for achieving abrasion resistance.

53
Q

Reduction of Water Penetration

A

Can be achieved by four means:
1. by keeping the water/cement ration to less than 0.50 by weight
2. by carefully treating all joints and cracks to prevent leaks
3. by adding chemicals and admixtures to the concrete mix to reduce water penetration
4. by applying a waterproof surface seal or compound.
Adding certain chemicals and admixtures to reduce water penetration often requires adding more mixing water, which may increase the permeability of the concrete

54
Q

Control of Setting Time for Concrete

A

Needed in order to:
1. reduce the setting time when temperatures are low enough to cause the water in the mix to freeze
2. to increase the time for working concrete during very hot weather
3. to control bleeding, or the movement of water to the surface of freshly placed concrete
Also, normal bleeding will be a problem if finishing is performed while bleed water is on the surface

55
Q

Methods of Placing Concrete

A

1. Formed and molded (cast in place or precast)
2. Sprayed or air-blown (shotcrete)
3. Mixed in place (such as soil cement or dry-casting)
Most common technique is formed and molded method

56
Q

Sprayed concrete

A

applied to complex horizontal and vertical surfaces
applied in relatively thin cross sections
will attain a very high density and strength
Widely used for swimming pools, sculpture elements, repairing deteriorating structures

57
Q

Mixed-in-place / soil concrete

A

create low-cost stabilized surfaces
typically involves mixing dry cement into the existing soil or surface materials, adding water, and then remixing and compacting

58
Q

Process of Hydration

A

When cements are mixed with water, a chemical reaction called hydration occurs which results in hardening of the cement paste

59
Q

Heat of Hydration

A

Heat is released during the hydration process between the cement and water. The amount of water released increases with the type of cement, the mass of the concrete, and/or higher ambient temperatures.
Heat should be retained in cold weather and dissipated in hot weather to maintain ideal curing temperatures

60
Q

portland cement

A

lime, silica, alumina, and gypsum

gypsum is used to slow the setting time of the concrete

61
Q

Aggregate for Concrete

A

aggregate constitutes 65-70 percent of volume of most types of normal concrete
most common types: sand, gravel, crushed stone
Fine is particles are smaller than 1/4 in.
coarse if larger than 1/4 in. in dia.
Both quality and cost of concrete are affected by type of aggregate used in mixture
Choice of aggregate often based on its local availability, give indigenous quality if aggregate is exposed in final finishing process

62
Q

Selection of aggregate based on criteria:

A

1. Resistance to abrasion if in a wearing surface
2. Performance record under conditions of similar use
3. Resistance to pop-outs or spalls caused by freezing or chemicals
4. Range of aggregate sizes needed for the required mix
5. Unit weight of the aggregate when used for lightweight concrete on rooftop gardens, plazas, decks, etc.

63
Q

Rules to consider for size and shape of aggregate

A

1. size of aggregate should not exceed
a. one-fifth the dimension of non-reinforced elements
b. three-fourths the clear spacing between reinforcing bars and/or forms
c. one-third depth of slabs.
Use of the largest-size aggregate practical will generally reduce shrinkage and cracking on concrete.
2. Use of a proper mix of both large (coarse) and small (fine) aggregates will reduce the amount of necessary water in the mix.
3. Rough angular-shaped aggregate (such as crushed stone) will provide a better bond for the cement paste. Rough angular aggregates will not necessarily result in a concrete of greater tensile and compressive strength than smooth, rounded aggregate because the angular aggregate requires more water in concrete and thereby somewhat reduces the ultimate strength of the concrete.
4. Elongated or flat aggregate should be avoided or limited to no more than 15 percent of the total aggregate by weight.

64
Q

Admixtures

A

substances added before or during the mixing of concrete
Used to enhance one or more properties of the resulting concrete

65
Q

Purposes of using admixtures

A

1. to improve the workability of the concrete mixture by minimizing the separation of coarse and fine aggregate while it is being cast and/or worked
2. To reduce the water requirement of concrete significantly and thereby increase its strength
3. To entrain air in the mixture and thereby improve the concrete's durability and resistance to freeze/thaw damage, and its resistance to scaling caused by deicing chemicals
4. To accelerate or retard the hardening or setting of concrete
5. To increase the flowability of concrete to aid in placement

66
Q

Considerations when selecting admixture

A

1. Whether the admixture will be compatible with the cement, aggregate, and any other admixtures that may be used
2. whether the admixture will affect the workability, setting time, shrinkage, strength, and/or permeability of the concrete.
3. whether the admixtures will actually produce the desired results

67
Q

Air-entraining admixture

A

Improves the concrete's resistance to freeze and thaw damage as well as to scaling due to deicing chemicals

68
Q

Water-reducing admixture

A

Reduces the amount of water required for a given consistency of mix, and may affect the setting time.
Some will increase drying shrinkage.
May entrain some air.

69
Q

Set-accelerating admixture

A

Used to accelerate the set of concrete resulting in higher early strength.
Some will increase dry shrinkage of the concrete during curing.

70
Q

Set-retarding admixture

A

Used to decelerate the set of concrete which results in lower early strength

71
Q

Pozzolans admixture

A

Used to reduce the amount of cement required in a concrete mix.
Improves workability
Strength is enhanced at later ages
Heat of hydration is reduced

72
Q

Superplasticizers admixture

A

Allows use of a much lower water to cement ration in a concrete mixture.
Can produce a more flowable concrete so that it can be pumped to the area of placement

73
Q

Types of Admixtures

A

Air-entraining
Water-reducing
Set-accelerating
Set-retarding
Pozzolans
Superplasticizers

74
Q

Water Quality and Concrete

A

Water should be clean and free of oils, alkali's, acids, organic materials, and other deleterious substances
Water containing high concentrations of sulfates or salts should also be avoided.
Potable water is typically satisfactory for use in concrete.

75
Q

Water Quantity in Concrete

A

Water needed always measured in relative proportion to the amount of cement used
An increase in the amount of water to cement will always result in concrete with less strength.
For protection against frost damage, air entrained concrete should have a maximum water to cement ration of 0.45
For protection of reinforcing steel against corrosion, water to cement ration should be no more than 0.40

76
Q

Mixing Concrete

A

If ready-mixed concrete is available from local suppliers, then on-site mixing is seldom justified except on exceptionally large projects.
Ready-mixed concrete should be delivered and placed within 90 minutes after cement has been added to the mixture.
If concrete is less than 90 minutes old and has started to stiffen or dry out before it has been placed, it may still be used but only if it can be completely consolidated into forms.
Adding water to the concrete to make the mixture more workable (retempering) is not ideal but ASTM C94 (standard for ready-mixed concrete) does allow one retempering to bring the mix up to design slump requirements

77
Q

Three Common Ways of Testing Concrete

A

Slump Test
Air Content Test
Cylinder Test

78
Q

Slump Test

A

determines the relative consistency among batches of concrete of the same design by measuring the amount of slump for a given-size cone of concrete.

Changes in slump typically reflect the amount of water in the mix, but they may also indicate changes in air content, sand content, aggregate gradation, temperature or hydration, and setting

79
Q

Air Content Test

A

Determines the air entrainment at the time of use, thereby allowing an opportunity to adjust the mixture, if necessary, by adding more air entraining agent.

An insufficient amount of air results in a concrete with poor resistance to freeze/thaw damage, and too much air results in a lower-strength concrete.
The air content should be 5-8% to protect concrete frost and deicer damage.

80
Q

Cylinder Test

A

Used to determine the compressive strength of cured concrete
Involved putting concrete into a cylindrical mold 6in. in dia. and 12in. high
After the concrete has cured, the concrete cylinder is prepared and put into a special testing machine and subjected to increasing pressure until it fails.
The point of failure is recorded as the concrete's strength in megapascals or pounds per square inch.
Typically, cylinder tests are conducted at 7 days and 28 days following placement.

81
Q

Site Preparation of Concrete

A

Most landscape uses require construction of appropriate granular subbase over a prepared (compacted) subgrade
Subgrade should be uniformly compacted, moist, and free of organic matter and expansive clays. Soft or muddy areas should be excavated, filled with soil similar to the abutting subgrade (or with a granular material such as sand, gravel, or crushed stone) and then compacted to the required density.
Subbase can be composed of a variety of granular materials as long as it is free-draining, durable, and capable of being compacted.

82
Q

Formwork for Concrete

A

- provides a container and supports concrete while it is setting
- designer will determine configuration of a completed work, contractor/builder will be responsible for actual strength design of forms
- used once of reused many times, sometimes left in place as concealed or exposed part (deadform)
- curved formwork for construction of walks/drives/walls can be made from thin plywood (1/4 to 1/2 in.), hardboard, sheet metal, or thicker lumber that is saw-kerfed
- Slip forms are used where continuous placing is advantage, especially for paving, curb, and gutter operations

83
Q

Pattern Making concrete

A

Form liners made of plastic, rubber, or other materials can be placed between the form's face and the concrete to provide special finishes, textures, and patterns
- wood, plastic strips, special plastic lines, or small cones or other shapes to the faces of forms

84
Q

Placement of Reinforcement

A

Used to give concrete structures and slabs greater tensile strength and to control cracking

85
Q

Types of Reinforcement

A

Welded wire fabric
Reinforcing bars
Secondary reinforcement (plastic, glass, or steel fibers)

86
Q

Welded Wire Fabric (WWF)

A

Consists of electrically welded grids of steel wire with or without galvanized coating or epoxy treatment.
Mesh available in rolls or flat sheets. Various gauges of wire and grid spacing available. Sizes referred by system of four numbers (6x6xW1.4xW1.4 - first longitudinal spacing, second transverse spacing, third and fourth respective wired sizes)

87
Q

Reinforcing Bars

A

Have irregularities or embossments called deformations which keep the bars from slipping within the concrete.
Bar size is indicated by a number which, when multiplied by 1/8in., gives the nominal diameter of the bar in inches (No. 4 bar area equal to bar of 1/2 in. dia.)
Steel reinforcing can be galvanized or coated with paints, plastic, or epoxy coatings. Some type of coating is essential where high corrosion is a factor (bridges, waterfront seawalls, docks)

88
Q

Secondary Reinforcement

A

Plastic fibers can be added to a concrete mix prior to pouring to create three-dimensional secondary reinforcement and to act as moderate inhibitors of plastic shrinkage cracks.
They are lightweight, noncorrosive, and inert to alkali attack. Can be used for precast and cast-in-place concrete.
Most manufacturers call for 1-1/2 lb/yd3 of concrete.
Fiber in lengths from 3/4 to 2-1/2 in.
Steel fibers are also available for use when the concrete will not be exposed to the elements.

LARE Section 4 (6 decks)

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