Highway Materials, Soils, and Concrete Aggregates

1
Highway Materials, Soils, and ConcreteAggregates

• Soil Definition (Engineering)
• refers to all unconsolidated material in the
  earths crust, all material above the bedrock
• mineral particles (gravel, sand, silt, clay)
• organic material (top soil, marshes)
• Aggregates
• mineral particles of a soil
• specifically, granular soil group
• gravel, sand, silt

2
Highway Materials, Soils, and ConcreteAggregates

• Granular Soil Group (Aggregates)
• Physical weathering
• action of frost, water, wind, glaciers,
  plant/animals
• particles transported by wind, water, ice
• soils formed are called granular soil type
• grains are similar to the original bedrock
• Larger grain sizes than clays
• Particles tend to be more or less spheres/cubes
• Bound water is small compared to overall mass

3
(No Transcript)
4
Highway Materials, Soils, and ConcreteAggregates

• Granular Soil Group (Aggregates)
• ability to achieve greater densities
• well graded granular material
• increased soil strength
• lower permeability
• reduced future settlement
• These improvements dictate the use of aggregates
  in pavement layers where wheel loads are greater

5
Highway Materials, Soils, and ConcreteAggregates

• In combination with asphalt cement or portland
  cement to form asphalt concrete or cement
  concrete respectively
• In subbases and bases of a roadway structure
• drainage structures
• concrete blocks

6
Highway Materials, Soils, and ConcreteAggregates

• Types of Aggregates
• Basic properties of these aggregates
• Tests used to evaluate these properties

7
Highway Materials, Soils, and ConcreteAggregates

• Aggregate Sources
• natural sand or gravel deposits
• crushed rock
• slag and mine refuse
• rubble and refuse
• artificial and processed materials
• pulverized concrete and asphalt pavements
• other recycled and waste materials

8
Highway Materials, Soils, and ConcreteAggregates

• Natural sand and gravel deposits
• sand and gravel pits
• sand and gravel soils that have been naturally
  sorted to eliminate most of the silt or clay
  sizes then deposited in
• glacier formations (eskers, outwash plains)
• river deposits
• beaches of current and previous lakes and seas

9
Highway Materials, Soils, and ConcreteAggregates

• Sand / Gravel Pit Development
• Stripping of topsoil, vegetation from surface
• Excavation of material
• material is loose - front end loaders
• Crushing of the material
• larger size aggregate is broke down to desired
  size
• crushed gravel is considered high quality
  aggregate
• washing of aggregate cleans dust removes
  silt/clay
• Type of material depends on bedrock source
• Limestone, sandstone,granite,etc.

10
Highway Materials, Soils, and ConcreteAggregates

• Crushed Rock
• Type of aggregates produced from quarries
  depends on the type of bedrock
• Classes of Rocks
• Igneous rocks
• Sedimentary rocks
• Metamorphic rocks

11
Highway Materials, Soils, and ConcreteAggregates

• Crushed Rock
• Igneous Rocks
• Original bedrock formed from the cooling of
  molten material
• Coarse grained igneous rock (granite) cooled
  slowly
• Fine grained igneous rocks (basalt) cooled
  rapidly
• Sedimentary Rocks
• Solidification of chemical or mineral sediments
  deposited under ancient seas
• Layered since original material was deposited in
  this manner

12
Highway Materials, Soils, and ConcreteAggregates

• Crushed Rock
• Sedimentary Rocks
• Limestone Calcium Carbonate
• Dolomite Calcium/Magnesium Carbonate
• Shale Clay
• Sandstone Quartz
• Chert Fine sand
• Conglomerate Gravel

13
Highway Materials, Soils, and ConcreteAggregates

• Crushed Rock
• Metamorphic Rocks
• Igneous or Sedimentary rocks that have been
  metamorphosed due to intense heat and pressure
• Slate shale
• Marble limestone
• Quartzite sandstone
• Gneiss granite

14
Highway Materials, Soils, and ConcreteAggregates

• Crushed Rock
• Igneous and Metamorphic rocks are very hard and
  make an excellent source for aggregates
• Limestone and Dolomite are common sedimentary
  rocks, are softer than igneous rocks but are
  acceptable for aggregates
• Shale primarily composed of clay grains is weak
  and disintegrates easily
• Chert also disintegrates easily

15
Highway Materials, Soils, and Concrete Aggregates

• Quarry Pit Development
• Opening and Stripping of the face of the quarry
• Blasting of rock with dynamite into sizes that
  can be transported
• Crushing of rock into the required aggregate
  sizes

16
Highway Materials, Soils, and Concrete Aggregates

• Slag and Mine Refuse
• Slag is a waste material resulting from the
  treatment of ore to produce iron, steel, nickel,
  ..
• Blast furnace slag from iron mills is a common
  aggregate
• Mine tailings can also be used for aggregates
• Rubble and Refuse
• recycling of pulverized concrete from structures
• recycled asphalt pavements in base courses
• recycled rubber, crushed glass in base courses

17
Highway Materials, Soils, and Concrete Aggregates

• Types of Aggregates
• Fine Aggregate
• aggregate particles mainly between the 4.75 mm
  size and the 75um sieve.
• Coarse Aggregate
• aggregate particles mainly larger than 4.75 mm
• Pit Run
• aggregate from a sand or gravel pit with no
  processing

18
Highway Materials, Soils, and Concrete Aggregates

• Types of Aggregates
• Crushed Gravel
• pit gravel (or sand) that has been put through a
  crusher either to break the rounded gravel
  particles into smaller sizes or to produce
  rougher surfaces
• Crushed Rock
• aggregate from the crushing of bedrock. All
  particles are angular and not rounded as in
  gravel
• Screenings
• chips, dust, powder that are produced from
  crushing

19
Highway Materials, Soils, and Concrete Aggregates

• Types of Aggregates
• Concrete Sand
• sand that has been washed to remove dust and
  fines
• Fines
• silt, clay, or dust particles smaller than 75um
  usually the undesirable impurities in aggregates

20
Highway Materials, Soils, and Concrete Aggregates

• Types of Aggregates
• Nominal Size
• Not economical to have 100 of the particles of
  an aggregate be within a specified size range.
• Reduce as much reject as possible from a pit in
  order to efficiently use the material resources
  of a pit
• Usually 5 - 10 of the aggregate particles can
  be allowed to be larger or smaller than specs

21
Highway Materials, Soils, and Concrete Aggregates

• Types of Aggregates
• Nominal Size
• Coarse aggregates 19-4.75 mm nominal aggregate
• Fine aggregate 4.75 mm nominal aggregate
• Clear
• a single size coarse aggregate is called clear.
  Most of the particles are between the specified
  maximum size and a minimum size which is defined
  as one-half of the maximum
• 19 mm clear aggregate

22
Highway Materials, Soils, and Concrete Aggregates

• Aggregate Properties
• Gradation (grain size analysis)
• grain size distribution for highway bases and
  asphalt mixes that will provide a dense strong
  mixture
• ensure that the voids between the larger
  particles are filled with medium particles. The
  remaining voids are filled with still smaller
  particles until the smallest voids are filled
  with a small amount of fines.
• Ensure maximum density and strength using a
  maximum density curve

23
Highway Materials, Soils, and ConcreteAggregates

• Theoretical Maximum Density Curves
• Fuller Maximum Density Curve
• P (d/D)0.5
• P passing sieve size d and D represents
  the maximum sieve size (100 passing)
• Federal Highway Administration
• P (d/D)0.45
• plotted on semi-log paper where sieve sizes are
  raised to power 0.45

24
Highway Materials, Soils, and ConcreteAggregates
25
Highway Materials, Soils, and ConcreteAggregate
Gradations

• Strength or resistance to shear failure in road
  bases and pavements is increased greatly if the
  mixture is dense graded

26
Highway Materials, Soils, and ConcreteAggregate
Gradations

• a) larger particles are in contact with each
  other developing frictional resistances to
  shearing failure. Particles are tightly bond
  together due to the inter-locking effect of
  smaller particles. This effect is higher in (a)
  than (b)

27
Highway Materials, Soils, and ConcreteAggregate
Gradations

• b) Must limit the amount of fines
• silt and clay particles are relatively weak
• dust on larger aggregates will interface with the
  aggregate/asphalt bond
• Excessive fines in a base or subbase may lead to
  drainage on frost leaving problems
• Excessive fines (smaller aggregates) results in
  weak structures because larger particles are not
  in contact with each other strength
• Sn (smaller particles) are weaker. Therefore
  managing of fines is important.

28
Highway Materials, Soils, and ConcreteAggregates

• Washed Sieve Analysis
• as a result it is important in determining the
  amount passing the 75mm sieve
• sample is dried and washed, wash water poured out
  over the 75 um sieve
• material retained is returned to the sample for
  sieve analysis
• total amount passing 75 um is equal to the amount
  lost in washing and passing 75 um sieve

29
Highway Materials, Soils, and ConcreteAggregates

• Example 4-1
• Mass of sample 446.7 g
• Mass after washing 414.1 g
• Results of dry sieving
• Retained in 4.75 mm 0.0g
• 1.18 mm 205.3g
• 300 mm 127.9g
• 75 mm 76.4g
• Pan 3.8g
• Find the grain-size distribution
• Lost in washing over 75 mm 446.7 g - 414.1 g
  32.6 g
• Passing 75 mm in sieving 3.8 g
• Total finer than 75 mm 36.4 g

30
Highway Materials, Soils, and ConcreteAggregates

• Note Only 0.7 g was lost during sieving, which
  is an acceptable loss.) If a washed sieve
  analysis is not required, usually for coarse
  aggregates the procedure for grain-size analysis
  of soils (see Section 1-3.3) is used

31
Highway Materials, Soils, and Concrete Aggregates

• Aggregate Properties
• Gradation (grain size analysis)
• High density mixtures are important in terms of
  density and asphalt cement required. Asphalt must
  coat each particle and fill in most of the void
  space. If you fill in void space with cheaper
  material such as aggregates you save asphalt

32
Highway Materials, Soils, and ConcreteAggregates

• The relative density (specific gravity) and
  absorption of aggregates are important properties
  especially in asphalt cement mixtures
• In the mix designs, it is important to measure
  accurately the volumes occupied by the aggregate
  and any water that may have seeped into the pores
  in the particles. Therefore voids must be
  considered in the aggregate.

33
Highway Materials, Soils, and ConcreteAggregates

• For aggregates
• Dry Mass MD
• Total Mass MSSD
• (dry mass MD absorbed water MWA)
• Bulk Volume VB
• (includes volume of absorbed water)
• Net Volume VN
• VN VB - volume of absorbed water

34
Highway Materials, Soils, and ConcreteAggregates

• Relative density calculations are made as
  follows
• Apparent RDA MD/(VN x rW)
• Bulk RDB MD/(VB x rW)
• Saturated, surface-dry RDSSD MSSD/(VB x rW)
• Percentage absorption Abs MWA/MD

35
Highway Materials, Soils, and ConcreteAggregates
36
Highway Materials, Soils, and ConcreteAggregates

• Saturated Surface Dry
• all permeable pores filled with water
• Bulk Volume VNET VABSORBED WATER

37
Highway Materials, Soils, and ConcreteAggregates
38
Highway Materials, Soils, and ConcreteAggregates
39
Highway Materials, Soils, and Concrete Aggregate
Properties

• Aggregate Hardness (resistant to wear)
• It is important that aggregates for pavement
  surfaces not become rounded or polished thereby
  reducing skid resistance
• Load cycles in the pavement structure tend to
  break aggregates or fines will result changing
  the gradation (finer) resulting in reduced
  strength of the pavement structure
• Broken aggregates are not cemented into the
  structure, again reducing strength

40
Highway Materials, Soils, and Concrete Aggregate
Properties

• Aggregate Hardness (contd)
• Resistance to degradation during mixing,
  transportation, placing and compacting is
  important as soft particles may break changing
  the gradation
• Los Angeles Abrasion Test measures the hardness
  of aggregates
• Deval Apparatus
• Aggregate Impact Value Test
• Polished Stone Value Test

41
Highway Materials, Soils, and Concrete Aggregate
Properties

• Aggregate Durability
• resistance to degradation due to cycles of
  wetting and drying, heating and cooling, and
  freezing and thawing
• freezing and thawing
• pore spaces in the aggregate are often saturated
  and on freezing expands
• repeated cycles can cause the aggregate to break
• sedimentary rocks are vulnerable because of
  planes of weakness between layers
• Soundness Test Field Performance / Absorption
  Value

42
Highway Materials, Soils, and Concrete Aggregate
Properties

• Aggregate Particle Shape/Surface Texture
• bonding capability with asphalt cement
• particles with rough fractured faces allow a
  better bond with asphalt cements than rounded
  smooth particles
• resistance to one particle sliding over another
• flat, thin, long aggregate particles break easier
  than cubical particles
• Specifications restrict the percentage of long
  thin particles and require aggregates particles
  having at least one fractured face

43
Highway Materials, Soils, and Concrete Aggregate
Properties

• Deleterious Substances
• harmful or injurious materials including various
  types of weak or low quality particles or
  coatings found on the surface of aggregates
• dust (material passing the 75 um sieve)
• clay lumps, shale, coal particles, friable
  particles, chert (weak in terms of freezing and
  thawing)
• These substances effect the bond between cements
  and aggregates and break easily
• Petrographic analysis Sand Equivalency Test

44
Highway Materials, Soils, and Concrete Aggregate
Properties

• Aggregate Crushing Strength
• crushing strength is the compressive load that
  aggregate particles can carry before breaking
• relatively unimportant for most aggregates
  strength is higher than the strength of an
  asphalt mix
• Chemical Stability
• refers to specific problems due to chemical
  composition

45
(No Transcript)
46
Highway Materials, Soils, and Concrete Aggregate
Specifications

• Specifications by highway departments takes into
  account the aggregate properties we just
  discussed
• Requirements for aggregates to be used in bases
  and subbases differ from aggregates to be used in
  asphalt mixes
• specifications include local experience,
  availability of materials and type of project

47
(No Transcript)
48
Highway Materials, Soils, and Concrete Aggregate
Properties

• Abrasion test
• Original mass 5009g 5009-3267 34.8
• Final mass 3267 g 5009
• Soundness test
• Original mass 2649g 2649-2115 20.2
• Final mass 2115 g 2649
• -lower strength fines content
• -drainage and frost heave potential
• -durability question freeze/thaw resistance

49
Highway Materials, Soils, and Concrete Aggregate
Sampling and Testing

• The characterization of an aggregate source
  depends on how representative the samples are
  taken from the aggregates
• size of samples are specified
• samples should be obtained from the final product
  if possible, after all the steps in processing
  and transportation have been completed

50
Highway Materials, Soils, and Concrete Aggregate
Sampling and Testing

• Samples taken from a production or discharge
  should be taken at various times and across the
  entire cross section of discharge and combined to
  form one sample
• Sampling from stockpiles requires care due to
  possible segregation of material. Three samples
  should be taken, one from the top third, middle
  third, bottom third and combined
• Sample tubes for fine aggregate stockpiles should
  be used, five tube samples combined

51
Highway Materials, Soils, and Concrete Aggregate
Sampling and Testing

• Samples taken from a truck or railway car should
  be done from a cross sectional trench, three
  combined to form one sample
• Combined samples should be done with equal size
  component samples
• Randomness should be used to determine location
  or time to eliminate personal bias
• Ensure proper identification of the sample
• Samples should be properly secured

52
Highway Materials, Soils, and Concrete Aggregate
Sampling and Testing

• Samples tested in the lab must be representative
  of the samples delivered to the lab
• Sample Splitting
• testing aggregates composed of significant
  amounts of both coarse and fine aggregates the
  sample must be split on the 4.75 mm sieve and the
  two fractions sieved separately
• If not, the amount of sample on the fine sieves
  may be too great for effective sieving

53
Highway Materials, Soils, and Concrete Aggregate
Sampling and Testing
54
(No Transcript)
55
Highway Materials, Soils, and Concrete Aggregate
Sampling and Testing
56
Highway Materials, Soils, and Concrete Aggregate
Sampling and Testing

57
Highway Materials, Soils, and Concrete Aggregate
Sampling and Testing