aggregates · aggregate processing • excavation • transportation • crushing • sizing •...

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Aggregates

Usually refers to a soil that has in some way been processed or sorted.

• Natural sands and gravels

• Crushed stone and rock

Soils are materials that are used as-is. An example would be a finished subgrade surface. Aggregates are materials that have been specifically sorted or processed to achieve given properties. This block will present general background information about how aggregates are obtained and processed.

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Aggregate Processing

• Excavation• Transportation• Crushing• Sizing• Washing

There are five general steps needed to prepare individual stockpiles of aggregates. Once stockpiles have been prepared, two or more stockpiles are typically blended together to produce a final gradation for a given construction application.

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* Natural sands and gravels- Underwater sources

+ Rivers, Wadis & lakesRelatively clean

- Land sources+ Gravel or sand pits

Bucket loader

Excavation

Excavation of natural sands and gravels from under water sources requires the use of barge-mounted dredges, draglines, scoops, conveyors, or pumps to bringthe material above the water line. Sand and gravel pits (land sources) are excavated using back hoes and bucket loaders. The following photos show examples of these procedures.

Natural sands and gravels have a rounded appearance due to the weathering action of water. Rounded natural sands are commonly used in portland cement concrete applications but crushing is required to obtain a more angular shape for use in asphalt concrete.

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5Sand and Gravel Excavation

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Excavation

Some aggregate sources are obtained by removing materials from the bottom of lakes and rivers.

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* Crushed stone and rock

- Rock depths > 15 m., remove overburden+ Soil stripped with bulldozers

and scrapers

- Rock depths < 15 m., overburden washed out during processing

- Blasting required

Excavation

Excavation of rock ledges requires blasting the solid ledges into transportable sizes. However, this can still leave very large blocks of rock to be moved. One or more crushing operations are needed to further reduce the size of the material. As a result of the blasting and crushing operations, quarried aggregates always have an angular particle shape.

The following photographs show examples of these types of operations.

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Excavation

This photograph shows typical operations in a limestone quarry.

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Crushing

The first step in preparing stockpiles for specific uses is the crushing the larger boulders and aggregates into usable sizes.

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Scalping.

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12Impact Crusher


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Horizontal Shaft Impactor

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14Impact & Grinding Crusher


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15Hammermill

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16Shear, Impact & Compression Crusher


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Sectional View of Jaw Crusher

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18Impact & Compression Crusher


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Gyratory Crusher


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20cone crusher

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Roller Crusher

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River Gravel Partially Crushed River Gravel

Crushing

Crushing of river gravels is used to change the shape of the aggregate particles.

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Transportation

Once materials are obtained,they are usually transported by land, rail, or barge to a centrally located plant for separation into specific sizes.

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Transportation

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Transportation

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Sizing

Once the rock has been sufficiently reduced in size, it is separated into individual stockpiles with specific ranges of particle sizes. Large screening operations have a number of wire mesh screen decks with each deck having progressively smaller openings between the wires. These screens are slanted and empty the material retained on each screen out onto conveyor belts. These belts then move the material into individual stockpiles of a particular size.

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Belt Segregation

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* Prevent segregation and contamination* Good stockpiling = uniform gradations

- Short drop distances- Minimize moving- Don't use "single cone" method- Separate stockpiles

Stockpiling

- Wind direction- Rain effect

Poor stockpiling practices can result in particle size separation even within a pile of limited particle sizes. Good stockpiling practices limit the drop distance and prepare a number of small stockpiles for a particular gradation of aggregate. This minimizes the separation of the fine and coarse particles. Moving stockpiles with trucks and dozers should be minimized in order to prevent excessive degradation of the aggregate (that is, more very fine particles). The following photographs show examples of good stockpiling practices.

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Stockpiling

This photograph shows a typical stockpiling operation.

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• Why Sampling Is Important– To evaluate the potential quality of a proposed

aggregate source.• Does new source meet aggregate

specifications?– To determine compliance with project

specification requirements.• Do current aggregates meet specifications?

Sampling

Once stockpiles have been produced, it is necessary to determine the final gradation and aggregate properties of each stockpile. There are specific guidelines which need to be followed in order to obtain samples of aggregates which represent the entire stockpile. Samples can be obtained from the stockpiles themselves or from the conveyor belts which move the aggregate from storage bins into the hot mix asphalt (HMA) plant.

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square-nosed shovel

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Sampling from Stockpile

Sampling from Aggregate Stockpile

Samples can be carefully obtained from an individual stockpile.

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Stockpile sampling with a sampling tube

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40Stockpiles or Transportation Units

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48

48Streamflow Sampling

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55Roadway (Bases and Subbases)

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SUPERPAVE TM

Level I- volumetric mix design

Level II- volumetric mix design- performance prediction

Level III- volumetric mix design- enhanced performance prediction

EA

Ls

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RECOMMENCED DESIGN LEVELS & TRAFFIC

Design Level Design Traffic (ESALS)

1 LOW

2 INTERMEDIATE

3 HIGH

LESS THAN 106

LESS THAN 107

MORE THAN 107

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SUPERPAVE TM

Aggregate Test/Selection

Binder Selection and Tests

Design Aggregate Structure ( Trial Blend Analysis )

Volumetric Design

Moisture Sensitivity

Performance Based Tests

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Aggregate TestsAggregate Tests

Source Properties Set by agency- Toughness (T 96)- Soundness (T 104)- Deleterious Materials (T 112)- Gradation

Consensus Properties Fixed- Coarse Aggregate Angularity- Fine Aggregate Angularity (NAA)- Elongated Particles (D 4791)- Clay Content (T 176)

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Definitions* Coarse Aggregate

- Retained on 4.75 mm (No. 4) ASTM D692- Retained on 2.38 mm (No. 8) Asphalt Institute- Retained on 2.00 mm (No. 10) HMA Book

* Fine Aggregate.

- Passing 4.75 mm (No. 4) ASTM D1073- Passing 2.38 mm (No. 8) Asphalt Institute

* Mineral Filler- At least 70% Pass. 0.075 mm ASTM D242

Source aggregate property tests evaluate specific fractions of each stockpile. Toughness evaluates the percent change in coarse aggregate particle size while aggregate soundness and the amount of deleterious material (clay lumps and friable particles) can be assessed for both fine and coarse aggregate. For Superpave testing, coarse aggregate is usually that which would be retained on a 4.75 mm sieve and fine aggregate the fraction which would pass this sieve. However, each test method needs to be checked to determine which definition is being used. Depending upon the test requirements, the very fine aggregate, called mineral filler, may or may not be included in the fine aggregate.

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Toughness* Los Angeles Abrasion (AASHTO T96, ASTM C131):

Resistance of coarse agg to abrasion and mechanical degradation during handling, construction and use

* Aggregate at standard gradation subjected to damage by rolling with prescribed number of steel balls in large drum for a given number of rotations

* Result expressed as % changes in original weight

This test subjects the coarse aggregate (in this case, retained on the 2.36 mm sieve) to impact and grinding by steel spheres. Each sphere has a mass between 390 and 445 g. The number of spheres introduced into the drum depends on the gradation of the aggregate to be tested. The number of spheres increases with increasing size of aggregate.

Once the aggregate and spheres are placed in the steel drum, the machine is rotated at between 30 and 33 rpm’s for 500 revolutions. The aggregates are then removed from the drum and sieved to determine the degradation as a percent loss. The percent loss is the difference between the original mass at the required gradation and the final mass of the test sample)

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LA Abrasion Test

- Approx. 10% loss for extremely hard igneous rocks- Approx. 60% loss for soft limestones and sandstones

This photo shows the equipment needed for the Los Angeles abrasion test. The panel on theside of the drum is removed and the aggregate and steel balls are placed inside. The panel is replaced and the drum rotated the prescribed number of cycles.

Examples of typical values are noted at the bottom of this photo.

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• Los Angeles Abrasion• Typical values 35 - 55• Most specifications 45 max.

Toughness

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LOS ANGELES ABRASION LIMITS

L.A. ABRASION LOSS (MAX.)

TRAFFIC WEARING NON WEARING LEVEL, EAL COURSE COURSE

50 5050 5045 5045 50 40 5040 5035 50

< 3 x 105

< 1 x 106

< 3 x 106

< 1 x 107

< 3 x 107

< 1 x 107

> 1 x 108

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Soundness* Estimates resistance to weathering .

* Simulates freeze/thaw action by successive wetting and drying of aggregate in sodium sulfate or magnesium sulfate solution

- One immersion and drying is considered one cycle

* Result is total percent loss over various sieve intervals for a prescribed number of cycles

- Max. loss values typically range from 10 to 20%per 5 cycles

Weathering of aggregates is simulated by repeated immersion in saturated solutions of either sodium or magnesium sulfate followed by oven drying. The internal expansive force from the expansion of the rehydration of the soluble salts upon re-immersion simulates freeze-thaw damage. The difference between the original and final mass, expressed as a percent of the original mass is the percent loss. A weighted percentage is used when several fractions are tested. The soundness of both fine (passing the 4.75 mm sieve) and coarse aggregate can be determined using this test.

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Soundness

Minimal supplies are needed for this test. Either sodium or magnesium sulfate can be used by dissolving the appropriate amount in water. Aggregates are placed in a wire mesh basket and then submerged in the solution (not shown).

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Soundness

Before After

Damage to the aggregate after a number of wet-dry cycles can be seen by visual examination as well as in the change in gradation.

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Soundness

• Sodium or magnesium Sulfate

• Typical values 10 - 20 %

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Clay Lumps and Friable ParticlesASTM C 142

Dries a given mass of agg., then soaks for 24 hr., and each particle is rubbed. A washed sieve is then performed over several screens, the aggregate dried, and the percent loss is reported as the % clay or friable particles.

Deleterious material is the mass percent of contaminants such as clay lumps, shale, wood, mica, and coal in the blended aggregate. This test can also be performed for both fine and coarse aggregates. The mass percentage of the material lost during a wet sieve is reported as the percent of clay lumps and friable particles.

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Deleterious Materials

• AASHTO T 112

• Both C. A. and F. A.

• Values range 0.2 - 10 %

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• Aggregate Gradation– The distribution of particle sizes expressed as

a percent of total weight.– Determined by sieve analysis

Gradations

A complete sieve analysis of the blended aggregate gradation consists of two parts. The first part determines the percent of particles finer than the 0.075 mm sieve. The second part is a discrete mechanical separation of various aggregate particle sizes and incorporates the results from the first part in the final gradation reported.

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Steps in Gradation Analysis

• Part 1 - Washed sieve analysis– Dry aggregate and determine mass– Wash and decant water through 0.075

mm sieve until water is clear– Dry aggregate to a constant mass

For this test (ASTM C117), a portion of aggregate is dried and the original mass of the sample is recorded. The aggregate is then placed in a bowl, gently washed with water, and the water decanted over a 0.075 sieve. When the water being decanted is reasonably clear, the aggregate is removed container. Any aggregate retained on the sieve used for decanting is returned to this sample and then dried to a constant mass. Once the dry mass is recorded, it is used for the mechanical particle size analysis.

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Washed Sieve

This photograph shows a mechanical washing system. The aggregate is placed in the large bucket and a gentle stream of water is started. Once the bucket is full of water, the excess water pours out the side and over a nest of two sieves. The larger sieve on top is there to protect the 0.075 mm sieve below in case larger aggregate particles are washed out of the bucket. The bucket is slowly rotating during this process.

Once the water pouring over the sieves is clear, the aggregate in the bucket is emptied into a pan. Any material retained on either of the two wash screeens is also added to the pan. The aggregate is then dried to a constant mass. The amount of 0.075 mm material lost during washing is the difference between the original mass and the dry mass after washing.

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Steps in Gradation Analysis

Part 2 - Mechanical sieve analysis– Place dry aggregate in standard stack

of sieves– Place sieve stack in mechanical shaker– Determine mass of aggregate retained

on each sieve

In the second step, the oven dry aggregate is placed in a stack of increasing smaller sieves, placed in a shaker and agitated for about 5 to 10 minutes. Gently separate the sieves and determine the mass of the sieve and aggregate. Dump aggregate out of sieve, thoroughly clean the sieve, and determine the mass of the sieve without the aggregate.

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Mechanical Sieve

Individual Sieve Stack of Sieves

Each sieve has wire mesh in the bottom. The sieve size (4.75 mm, 2.36, mm etc.) denote the distance between each wire. Sieves are stacked from largest openings on the top to smallest openings on the bottom. There is always a pan (no openings) at the bottom of the stack.

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Mechanical Sieve

Stack in Mechanical

Shaker

Once the stack is assembled and the oven dry aggregate added to the top, it is placed in a mechanical shaker. This is run from 5 to 15 minutes. Care needs to be taken to ensure that any given sieve is not overloaded. That is, that there is so much material on the screen that material cannot be efficiently separated.

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Gradations - ComputationSieve Mass Cumulative

Retained Mass Retained % Retained % Passing

9.54.752.361.180.600.300.150.075Pan

0.06.5

127.4103.472.864.260.083.022.4

Once the shaker stops, the stack is removed and the mass of aggregate retained on each screen is determined. These masses are recorded and used in subsquent calculations (next slides).

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Gradations - Computing

% Passing =Cum. Wt RetainedOriginal Dry Wt. * 100

% Retained = Cum. Wt RetainedOriginal Dry Wt. * 100

[ 1 - ]

The percent retained on each sieve is a ratio of the mass of aggregate on each sieve divided by the original mass (before washing). The cumulative percent retained is simply the sum of the percent retained on each sieve above the one of interest. The cumulative percent passing, commonly referred to as “percent passing”, is 1 minus the cumulative percent retained.

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Gradations - ComputationSieve Mass Cumulative

Retained Mass Retained % Retained % Passing

9.54.752.361.180.600.300.150.075Pan

0.06.5

127.4103.472.864.260.083.022.4

0.06.5

133.9237.3310.1374.3434.3517.3539.7

0.01.2

24.844.057.569.480.595.8

100.0

100.098.975.256.042.630.619.54.20.0

This is an example of the calculations necessary for a sieve analysis. What is not shown is that the 22.4 g of material in the pan is the sum of the mass which was washed past the0.075 mm sieve in the first part and the mass of the aggregate retained in the pan after the mechanical sieve analysis. This is an important point as the final gradation reported needs to reflect the true percentage of fractions in the stockpile which will be used during construction.

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* Uniformly graded- Few points of contact- Poor interlock (shape dependent)- High permeability

* Well graded- Good interlock- Low permeability

* Gap graded- Only limited sizes- Good interlock- Low permeability

Types of Gradations

There are several general types of aggregate gradations. Uniform gradations have large percentages of one size. Well graded aggregates have approximately equal amounts on each sieve in the stack. Gap graded aggregates have large and small but few intermediate sizes.

The properties of the aggregate gradation depends strongly on the distribution of aggregates sizes.

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Specific Gravity Tests for Specific Gravity Tests for AggregatesAggregates

• Two tests are needed– Coarse aggregate (retained on the

4.75 mm sieve)– Fine aggregate (passing the 4.75

mm sieve)

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Coarse Aggregate Specific Coarse Aggregate Specific GravityGravity

• ASTM C127– Dry aggregate– Soak in water for 24 hours– Decant water– Use pre-dampened towel to get SSD condition– Determine mass of SSD aggregate in bucket– Determine mass under water– Dry to constant mass– Determine oven dry mass

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Coarse Aggregate Specific GravityCoarse Aggregate Specific Gravity

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Coarse Aggregate Specific GravityCoarse Aggregate Specific Gravity

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Coarse Aggregate Specific GravityCoarse Aggregate Specific GravityCalculations

• Gsb = A / (B - C)– A = mass oven dry– B = mass SSD– C = mass under water

• Gs,SSD = B / (B - C)• Gsa = A / (A - C)• Water absorption capacity, %

– Absorption % = [(B - A) / A] * 100

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Fine Aggregate Specific GravityFine Aggregate Specific Gravity

• ASTM C128– Dry aggregate– Soak in water for 24 hours– Spread out and dry to SSD– Add 500 g of SSD aggregate to pycnometer of known volume

• Pre-filled with some water– Add more water and agitate until air bubble have been removed– Fill to line and determine the mass of the pycnometer, aggregate

and water– Empty aggregate into pan and dry to constant mass– Determine oven dry mass

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Fine Aggregate Specific Fine Aggregate Specific GravityGravity

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Fine Aggregate Specific GravityFine Aggregate Specific GravityCalculations

Gsb = A / (B + S - C)• A = mass oven dry• B = mass of pycnometer filled with water• C = mass pycnometer, SSD aggregate and water• S = mass SSD aggregate

Gs,SSD = S / (B + S - C)Gsa = A / (B + A - C)Water absorption capacity, %

Absorption % = [(S - A) / A] * 100

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Aggregate TestsAggregate Tests

Source Properties Set by agency- Toughness (T 96)- Soundness (T 104)- Deleterious Materials (T 112)- Gradation

Consensus Properties Fixed- Coarse Aggregate Angularity- Fine Aggregate Angularity (NAA)- Elongated Particles (D 4791)- Clay Content (T 176)

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Percent Crushed Fragments in GravelsPercent Crushed Fragments in Gravels0% Crushed 100% with 2 or More

Crushed Faces

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Coarse Aggregate AngularityCoarse Aggregate Angularity

Traffic Level (EAL) Surface (d<100mm) Base (d>100mm)

< 3 x 105

< 1 x 106

< 3 x 106

< 1 x 107

< 3 x 107

< 1 x 107

> 1 x 108

55/-65/-75/-

85/8095/90

100/100100/100

-/--/--/-

65/-80/7595/90

100/100

Percent Crushed Faces(1/2)

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Flat and Elongated ParticlesFlat and Elongated Particles

• ASTM D4791– Flat– Elongated– Total flat and elongated

• Superpave– Flat and Elongated– Maximum to minimum dimension

• 5:1• 3:1• 2:1

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Flat and ElongatedFlat and ElongatedMaximum Minimum

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Flat and ElongatedFlat and ElongatedMaximum Minimum

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Flat and Elongated Particles

• ASTM D 4791• Length

—————— < 5 Thickness

• 7 traffic levels

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Flat and Elongated CriteriaFlat and Elongated CriteriaTraffic Maximum, Percent

Millions of ESALs

< 0.3< 1< 3< 10< 30< 100> 100

----1010101010

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Fine Aggregate AngularityFine Aggregate Angularity

fine aggregate sample

known volume (V)

Uncompacted voids = ———— x 100%V – W/Gsb

V

high voids = high angularitylow voids = low angularity

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Fine Aggregate Angularity

Natural sands: typically < 45

Manufactured sands: typically > 42

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Fine Aggregate AngularityFine Aggregate Angularity

- -40 -40 4045 40 45 4045 4545 45

Surface (d <100mm) Base (d >100mm)Traffic Level, EAL

Percent Void Content

< 3 x 105

< 1 x 106

< 3 x 106

< 1 x 107

< 3 x 107

< 1 x 107

> 1 x 107

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Clay Content(Sand Equivalent Test)

* ASHTO T176, ASTM D2419- Used to estimate the relative proportions

of fine agg. and clay-like or plastic fines and dust.

SE = Sand ReadingClay Reading

Sand Reading

Clay Reading

Flocculating Solution

SuspendedClay

Sedimented Aggregate

*100

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105

Bottle of Solution on Shelf Above Top of Cylinder

Hose and Irrigation Tube

Measurement Rod

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Marker on Measurement Rod

Top of Suspended MaterialTop of Sand Layer

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SAND EQUIVALENT VALUES

Traffic Level SAND EQUIVALENTEAL MINIMUM %

40404045455050

< 3 x 105

< 1 x 106

< 3 x 106

< 1 x 107

< 3 x 107

< 1 x 107

> 1 x 108

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Aggregate Size Definitions

• Nominal Maximum Aggregate Size– one size larger than the first sieve

to retain more than 10%

• Maximum Aggregate Size– one size larger than nominal

maximum size

10010010010090907272656548483636222215159944

100100999989897272656548483636222215159944

For HMA pavements these are the definitions for gradations.

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SUGGESTED NOMINAL MAXIMUMAGGREGATE SIZES

SIZE

PAVE MENT LAYER mm inch

SURFACE 9.5 3/8

BINDER 25.4 – 37.5 1 – 1 1/2

BASE >37.5 > 1 1/2

1 INCH

¾ INCH

½ INCH

3/8 INCH

No. 4

No. 8

No. 30

No. 100

No. 200

SIVE SIZE PERCENT PASSING

100

98 -100

80 - 91

77-87

58-71

45-56

24-35

9-18

4-6

110

111

111

Example: Example:

4.75 mm sieve plots at (4.75)4.75 mm sieve plots at (4.75)0.450.45 = 2.02= 2.02

Sieve Size (mm) Raised to 0.45 PowerSieve Size (mm) Raised to 0.45 Power

00

2020

4040

6060

8080

100100

00 11 22 33 44

Percent PassingPercent Passing

0.45 Power Grading Chart0.45 Power Grading Chart

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112

100100

00.075.075 .3.3 2.362.36 4.754.75 9.59.5 12.5 19.012.5 19.0

Percent PassingPercent Passing

control pointcontrol point

restricted zonerestricted zone

max density linemax density line

maxmaxsizesize

nomnommaxmaxsizesize

Sieve Size (mm) Raised to 0.45 PowerSieve Size (mm) Raised to 0.45 Power

To specify aggregate gradation, two additional features are added to the 0.45 chart: control points and a restricted zone. Control points function as master ranges through which gradations must pass. They are placed on the nominal maximum size, an intermediate size and the dust size.The restricted zone resides along the maximum density gradation between the intermediate size (either 4.75 or 2.36 mm) and the 0.3 mm size. It forms a band through which gradations should not pass. Gradations that pass through the restricted zone have often been called “humped gradations” because of the characteristic hump in the grading curve that passes through the restricted zone. In most cases, a humped gradation indicates a mixture that possesses too much fine sand in relation to total sand. This gradation practically alwaysresults in tender mix behavior, which is manifested by a mixture that is difficult to compact during construction and offers reduced resistance to permanent deformation during its performance life. Gradations that violate the restricted zone possess weak aggregate skeletons that depend too much on asphalt binder stiffness to achieve mixture shear strength. These mixtures are also very sensitive to asphalt content and can easily become plastic.

Design Aggregate Structure

100

0

0.075 1.18 2.36 4.75 9.5 19 25mm

max density line

restrictedzone

control pointnonmaxsize

maxsize

% Passing

Sieve Size (0.45 power)

113

114

114

100

0200 50 8 4 3/8” 1/2” 3/4”

% Passing




100

0

% Passing


0.075 1.18 2.36 4.75 9.5 19 25mm

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Table A-1. 37.5 mm ( 1 1 /2 in.) NOMINAL MAXIMUM SIZE

CONTROL POINT (PERCENT PASSING)

MINIMUM MAXIMUM

75μm ( No. 200 ) 0 6

2 .36 mm (No.8) 15 -

Nominal maximum 90 100(37.5 mm) (1 1 / 2)

Maximum (50.0 mm) (2 in.) 100 -

SIEVE SIZE

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Table A-2. 25.4 mm ( 1 in.) NOMINAL MAXIMUM SIZE


MINIMUM MAXIMUM

75μm ( No. 200 ) 1 7

2 .36 mm (No.8) 19 -

Nominal maximum 90 100(25.4 mm) (1 in.)

Maximum (37.5 mm) (1 1/2 in.) 100 -

SIEVE SIZE

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Table A-3. 19.0 mm (3/4 in.) NOMINAL MAXIMUM SIZE


MINIMUM MAXIMUM

75μm ( No. 200 ) 2 8

2 .36 mm (No.8) 23 -

Nominal maximum 90 100(19.0 mm) (3/4 in)

Maximum (25.4 mm) (1 in.) 100 -

SIEVE SIZE

118



MINIMUM MAXIMUM

75μm ( No. 200 ) 2 10

2 .36 mm (No.8) 28 -


Maximum (19.0 mm) (3/4 in.) 100 -

SIEVE SIZE

119



MINIMUM MAXIMUM

75μm ( No. 200 ) 2 10

2 .36 mm (No.8) 32 -


Maximum (12.5 mm) (3/8 in.) 100 -

SIEVE SIZE

120

-

47.2 / 47.2

31.6 / 37.6

23.5 / 27.5

18.7 / 18.7

Table A-6. Boundaries of Aggregate Restricted Zone

Sieve Size WithinRestricted Zone

Minimum & Maximum Boundaries of Sieve Size forNominal Max. Aggregate Size. (Min. / Max. % Passing)

1 ½ in 1 in ¾ in ½ in 3/8 in

4.75mm (No. 4)

2.36mm (No.8)

1.18mm (No.16)

0.60mm (No. 30)

0.30mm (No. 50)

34.7 / 34.7

23.3 / 27.3

15.5 / 21.5

11.7 / 15.7

10.0 / 10.0

39.5 / 39.5

26.8 / 30.8

18.1 / 24.1

13.6 / 17.6

11.4 / 11.4

-

34.6 / 34.6

22.3 / 28.3

16.7 / 20.7

13.7 / 13.7

-

39.1 / 39.1

25.6 / 31.6

19.1 / 23.1

15.5 / 15.5

121

0.01 0.10 1.00 10.00

Sieve size, mm

0

20

40

60

80

100

Perc

entp

ass in

g

1.0013/43/8#4#10#40#200

123


Sieve Size (mm) Raised to 0.45 Power

0

20

40

60

80

100

Perc

entp

ass in

g

MOC Specification for Wearing Course type BWC-1 with SHRPRestricted Zone and Control Points.

MOC Specs.

BWC-1 Gradation Envelope

0.075 2.36 12.5 19.0 25.0

124

Design Aggregate Structure%

PA

SSIN

G

75 μ m 2.36mm 19.0 mm 25mm

Trial Blend 3

Trial Blend 2

Trial Blend 1

100.090.080.070.060.050.040.030.020.010.0

0.0

Trial Gradations19.0 mm Nominal Mixture

SIEVE SIZE (raised to 0.45 power)

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