ROAD MATERIAL

A. AGGREGATES a broad category of coarse particulate material used in construction, including sand, gravel, crus

hed stone, slag, recycled concrete and geo- synthetic aggregates. used as a stable foundation or road/rail base with predictable, uniform properties, or as a low-

cost extender that binds with more expensive cement or asphalt to form concrete.

Three Types of Aggregates

Coarse aggregate Fine aggregate Mineral filler

Physical Properties

Absorption Density Porosity Specific Gravity Permeability Hardness Surface Texture Particle shape Strength Coatings Elasticity

Primary Uses of Aggregates in Highway Construction

1. As compacted aggregates in bases, sub- bases and shoulders2. As ingredients in hot mix asphalt3. As ingredients in Portland cement concrete

B. AGGREGATES FOR BITUMINOUS PAVEMENT composed of compacted aggregate and bitumen the aggregate transmits the load from the surface to the base and the bitumen (bituminous

binder) holds the aggregate together for bituminous construction, aggregate is classified according to particle size

The AASHTO standards specifications provide that:

“The aggregate shall consist of hard, durable particles of fragments of stone or gravel and sand or other fine mineral particles free from vegetable matter and lumps or balls of clay and of such nature it can be compacted readily to form a firm, stable layers. It shall conform to the grading requirements shown in table 3when tested by AASHTO T-11 and 27”.

The following materials are classified under Item 300 of the DPWH standard specifications.

The coarse aggregate material retained on the 2.00 mm (No.10) sieve shall have a mass per cent of wear by the Los Angeles Abrasion Test (AASHTO T-96) of not more than 45.

When crushed aggregate is specified, not less than 50 mass per cent of the particles retained on the 4.75 mm (No. 4) sieve shall not have at least one fractured face.

The fraction passing the 0.75mm (No. 200) sieve should not be greater than two thirds of the fraction passing the 0.425 mm (No.40) sieve.

The fraction passing 0.425 mm (No.40) sieve shall have a liquid limit of not greater than 35 and a plasticity index range of 4 to 9 when tested by AASHTO T-89 and T-90respectively.

C. AGGREGATES FOR PORTLAND CEMENT CONCRETE

Important Properties for Aggregates that are used in Concrete Paving Mixtures:

1. Gradation The size distribution of the aggregate particles affects the relative proportions, cementing

materials and water requirements, workability, pump ability, economy, porosity, shrinkage, and durability. The size distribution of the aggregate particles should be a combination of sizes that results in a minimum of void spaces.

2. Absorption The absorption and surface moisture condition of aggregates must be determined so that the

net water content of the concrete can be controlled.

Particle Shape and Surface Texture

Rough textured, angular, or elongated particles require more water to produce workable concrete.

Smooth, rounded, compact aggregates require more cementing materials to maintain the same water- cement ratio.

Angular or poorly graded aggregates may result in the production of concrete that is more difficult to pump and also may be more difficult to finish. The hardened concrete strength will generally increase with increasing coarse aggregate angularity, and flat or elongated coarse aggregate particles should be avoided.

Abrasion Resistance

The abrasion resistance of an aggregate is often used as a general index of its quality. Abrasion resistance applies only to coarse aggregates. Aggregates vary in their resistance to fracturing under impact (toughness); and breaking down into smaller pieces from abrasive action (hardness).

Durability

Aggregates must be resistant to breakdown and disintegration from weathering (wetting/drying and freezing/thawing) or they may break apart and cause premature pavement distress. Durability and soundness are terms typically given to an aggregate’s weathering resistance characteristic.

Soundness Test

The soundness test repeatedly submerges an aggregate sample in a sodium sulfate or magnesium sulfate solution. This process causes salt crystals to form in the aggregate’s water permeable pores. The formation of these crystals creates internal forces that apply pressure on aggregate pores and tend to break the aggregate.

Deleterious Materials

Aggregates should be free of potentially deleterious materials such as clay lumps, shales, or other friable particles, excess dust and vegetable matter are not desirable because they generally affect performance by quickly degrading, which causes a loss of structural support and/or prevents binder-aggregate bonding.

Particle Strength

For normal concrete pavements, aggregate strength is rarely tested. However, aggregate characteristics other than strength, such as the size, shape, surface texture, grading and mineralogy are known to affect concrete strength in varying degrees. Particle strength is an important factor in high-strength concrete mixtures.

D. MINERAL FILLERS

Purpose of mineral fillers in asphalt mixes:

The portion of the mineral filler that is finer than the thickness of the asphalt film and the asphalt cement binder form a mortar or mastic that contributes to improved stiffening of the mix.

The particles larger than the thickness of the asphalt film behave as mineral aggregate and hence contribute to the contact points between individual aggregate particles.

The gradation, shape, and texture of the mineral filler significantly influence the performance of hot mix asphalt.

Important Properties of Mineral Filler used in asphalt concrete application

Gradation – mineral fillers should have 100 percent of the particles passing 0.60 mm (No. 30 sieve), 95 to 100 percent passing 0.30 mm (No. 40 sieve), and 70 percent passing 0.075 mm (No. 200 sieve)

Plasticity – mineral fillers should be non-plastic so the particles do not bind together Deleterious Materials – the percentage of deleterious materials such as clay and shale in the

mineral filler must be minimized to prevent particle breakdown

E. BITUMINOUS MATERIALS AND BINDERS

Testing Methods:

Penetration graded bitumen Viscosity graded bitumen Osidized bitumen grades

Penetration Graded Bitumen

Bitumen is classified by the depth to which a standard needle will penetrate under specified test conditions. This “pen” test classification is used to indicate the hardness of bitumen, lower penetration indicating a harder bitumen.

Viscosity graded bitumen

Bitumen is also graded and specified by their viscosity at a standard temperature (typically 60°C). Specifications for viscosity graded bitumen normally give the nominal viscosity prefixed by a V, e.g. V1500.

Oxidised bitumen grades

The degree of oxidation can range from very small, often referred to as air- rectification, or semi-blowing, which only slightly modifies the bitumen properties, through to “full” blowing, whereby the properties of the bitumen are significantly different to penetration grade bitumens.

Nomenclature and grading for the oxidised bitumen products is based on a combination of the temperature at which the bitumen reaches a certain “softness” when being heated up as expressed by the ring and ball softening point test, and the penetration value.

Bitumen Preparations:

a) Cut-back bitumenb) Fluxed bitumenc) Modified bitumen

Cut-back bitumen

Cut-backs are bitumen preparations in which the viscosity of the binder has been reduced by the addition of a volatile solvent, normally derived from petroleum. Typically the solvents used are white spirit and kerosene. Cut- back products are typically used for spraying and some mixing applications.

Fluxed bitumen

Fluxed bitumens are bitumen preparation where the viscosity of the binder has been reduced by the addition of relatively non-volatile oils. Typical fluxants include gas oil and vegetable based oils.

Modified bitumen

Modified bitumens are bituminous binders whose performance properties, such as elasticity, adhesive or cohesive strength, have been modified by the use of one or more chemical agents. These agents may be polymers, crumb rubber, Sulphur and Polyphosphoric acid, among other materials. Modified bitumens are widely used in the production of roofing felt and in paving applications.

Bitumen emulsion

Bitumen emulsions are products in which tiny droplets (the dispersed phase) of bitumen or bituminous binder are dispersed in an aqueous medium (the continuous phase). Bitumen emulsions are used largely in road surfacing applications, such as surface dressing, cold mixtures and slurry seals.

Asphalt

Asphalt is a mixture of a bituminous binder with mineral aggregate (stone), sand and filler, typically containing approximately 4-7%m bitumen.

F. BITUMINUOUS CONCRETE PAVEMENT

Bituminous concrete

Is a type of construction material used for paving roads, driveways, and parking lots Made from a blend of stone and other forms of aggregate materials joined together by a binding

agent. This binding agent is called “bitumen” Has a thick, sticky texture like tar when heated, then forms a dense solid surface once it dries. Is also widely known as asphalt in many parts of the world.

Bituminous concrete is quite different than standard concrete, and contains no cement. Bituminous concrete is known for its distinctive black appearance. Asphalt paving is also fully recyclable. Some manufacturers add recycled tires or glass aggregate to recycled asphalt to increase its strength and resilience.

Bituminous concrete is strong enough to handle years of vehicle traffic, and is relatively easy to repair or refinish. It also provides a smoother and quieter ride than cement surfaces, which helps to reduce noise pollution around highways and other busy roads.

G. ASPHALT CONCRETE PAVEMENT composite material used in the construction of roadways and parking lots

mixture of a petroleum byproduct, asphalt bitumen and aggregate materials

Methods of mixing asphalt

1. Hot mix asphalt concrete, HMAC produced by heating the asphalt binder to decrease its viscosity, and drying the aggregate to

remove moisture from it prior to mixing

** Mixing is generally performed with the aggregate at about 300 °F (roughly 150 °C) for virgin asphalt and 330 °F (166 °C) for polymer modified asphalt, and the asphalt cement at 200 °F (95 °C)

2. Warm mix asphalt concrete, WMA produced by adding either zeolites, waxes, asphalt emulsions, or sometimes even water to

the asphalt binder prior to mixing

**This allows significantly lower mixing and laying temperatures and results in lower consumption of fossil fuels, thus releasing less carbon dioxide, aerosols and vapors

3. Cold mix asphalt concrete produced by emulsifying the asphalt in water with (essentially) soap prior to mixing with the

aggregate commonly used as a patch for road surfaces

4. Cut-back asphalt concrete same process as in cold mix, but instead of soap and water, kerosene or light petroleum

products are employed to emulsify the asphalt binder5. Mastic asphalt concrete

produced by heating hard grade blown bitumen (oxidation) in a green cooker (mixer) until it has become a viscous liquid after which the aggregate mix is then added, and then to be cooked again for another 6 to 8 hrs.

Used for footpaths, roofing, flooring and other light-use paving projects6. Natural asphalt concrete

occurs as the result of upwelling bitumen exist below the Earth’s surface, but can seep its way up through porous sedimentary rocks

and stones

H. BITUMINUOUS PAVEMENTFAILURE Caused by excessive loads. Heavy loads creates deflection on the road surface, with insufficient underlying strength. Repetitious underlying of the excessive load with roughen and crack the road pavement will

ultimately result to complete failure of the roadway.

1. Bleeding or Flushing

This distress is caused by excess asphalt in the surface layer Major bleeding can be corrected by cutting off excess asphalt with a motor grader or removing it

with a “heater planer”.2. Corrugations and Shoving

To repair corrugations in an aggregate base overlain with a thin surface treatment, scarify the pavement, add aggregate as needed, mix well, re-compact, prime, and then resurface. Where the surface has 2 inches or more of asphalt plant mix, corrugations can be removed with a “heater planer”. After removal of corrugations, cover with a new surface treatment or new asphalt overlay. To repair shoved areas, remove surface and base as necessary and replace with a more stable material to prevent a recurrence. For out-of-season inclement weather repairs, smooth shoved areas with patching if the surface unevenness is hazardous to traffic.

3. Cracking, Alligator Interconnected cracks forming a series of small polygons resembling an alligator’s skin are called

alligator cracks.

Types of Alligator Cracks

Alligator Cracking without Surface Distortion Alligator Cracking with Distortion of Intact Surfaces Alligator Cracking with Broken Surfaces Alligator Cracking with Surface Distortion and Pumping

4. Cracking Edge Cracking without surface distortion is usually caused by lack of shoulder (lateral) support.

Types of Cracking Edge

Edge Cracks without Surface Distortion Edge Cracks with Distortion of Intact Surfaces Edge Cracks with Broken Surfaces Edge Cracks with Surface Distortion and Pumping

5. Cracking Joint Joint cracks occur where the shoulder or paved wedge separates from the mainline pavement or

along weak seams of adjoining pavement spreads in the surface layers.

Types of Cracking Joint

Joint Crack at Pavement Edge Joint Crack at Lane Joints

6. Random Cracking The causes of random cracking are numerous and, in its early stages, difficult to determine.

Consequences range from severe, such as deep foundation settlement, to slight, such as a construction error or mishap.

Types of Random Cracking

Narrow Cracks Wide Cracks Reflection Cracking Shrinkage Cracking Slippage Cracking Transverse Cracking

7. Polished Aggregate Although uncrushed gravels often have surfaces that are initially smooth and potentially

hazardous, crushed rock initially has a rough, skid-resistant texture. Under the action of traffic, however, some aggregates - including many limestones - become polished and slick, especially when wet. The likelihood of aggregate become polished increases with the volume of traffic. Because polished aggregate results in a loss of skid resistance, itis potentially hazardous. The most economical repair is to apply a skid-resistant surface treatment.

8. Potholes Potholes are caused by water penetrating the surface and causing the base and/or subgrade to

become wet and unstable. They also may be caused by a surface that is too thin or that lacks sufficient asphalt content, lacks sufficient base, or has too many or too few fines.

Potholes in Surface Treatments over Aggregate Base

To repair potholes in surface treatments, take the following actions:

Clean out hole. Remove any wet base. Shape hole so that it has vertical sides. Prime hole. Fill hole with Asphalt Concrete.

Potholes in Asphalt Concrete

To repair potholes in Asphalt Concrete,take the following actions:

Clean out hole. Remove any wet base. Square up pothole so that it has neat lines both perpendicular and parallel to the center line

and have vertical sides. Prime the pothole. Fill the pothole with Asphalt Concrete.

9. Raveling

Raveling is caused by a dry brittle surface; dirty, dusty, or soft aggregate; patching beyond base material; lack of compaction of surface during construction; too little asphalt in mix; or excessive heating during mixing.

Note: If the raveling is not a part of the paved surface, no action should be taken. In other words, don’t patch beyond the edge of the pavement.

10. Channels or Rutting Channels are caused by heavy loads and high tire pressures, subgrade settlement caused by

saturation, poor construction methods, or asphalt mixtures of inadequate strength.

11. Intact Surface Where the depression is 1 inch or less and the surface is cracked but still largely intact, skin

patch the area. Where the depression is more than 1 inch and the surface is cracked but still largely intact, repair with asphalt concrete.

12. Disintegrated Surface Where the surface is badly cracked and loose (regardless of amount of depression), remove the

old surface. If the area shows signs of mud being pumped to the surface, remove all wet material, replace base material, compact, prime, and build up with Asphalt Concrete.

13. Upheaval or Frost Boil Upheaval is caused by expansion of freezing moisture in the lower courses of the pavement or

subgrade or by the swelling effect of moisture in expansive soils. When this distress occurs, repair by installing combination drains as necessary and replacing base and surface.

I. Macadam Asphalt Pioneered by Scottish engineer John Loudon McAdam in around 1820

** he discovered that massive foundations of rock upon rock were unnecessary, and asserted that native soil alone would support the road and traffic upon it, as long as it was covered by a road crust that would protect the soil underneath from water and wear

The lower 200-millimetre (7.9 in) road thickness was restricted to stones no larger than 75 millimeters (3.0 in).

The upper 50-millimetre (2.0 in) layer of stones was limited to 20 millimeters (0.79 in) size and stones were checked by supervisors who carried scales

Tar-bound macadam or tarmac

The area of low air pressure created under fast-moving vehicles sucks dust from the road surface, creating dust clouds and a gradual unravelling of the road material. This problem was approached by spraying tar on the surface to create tar-bound macadam.

J. SURFACETREATMENT

A surface treatment is an application of asphalt materials to any type of road surface with or without cover of mineral aggregate.

This application produces an increase in thickness usually less than 1 inch. Have a variety of uses

PURPOSES

1. Waterproof the surface2. Provide a wearing surface.3. Make the surface nonskid.4. Prevent hydroplaning.5. Rejuvenate an old road or runway.6. Make permanent improvements

TYPES

Surface treatments may be applied to the base course of a new road or to the surface of an old road as a method of repair. Surface treatments are grouped into these categories:

1. Sprayed Asphalt Surface Treatment2. Aggregate Surface Treatment

Sprayed Asphalt Surface Treatment

Sprayed asphalt treatments contain no aggregates. They are simply applications of different types of asphaltic materials to a prepared surface. Three types of sprayed asphalt surface treatment:

1. FOG SEAL2. DUST LAYING3. ROAD OILING

FOG SEAL

A fog seal is a light application of diluted slow-setting asphalt emulsion, used to renew old asphalt surfaces and seal small cracks and surface voids. Fog seals are especially useful for pavements carrying a low volume of traffic.

Other uses: To seal surface voids in new asphalt plant mixes To prevent dust on sprayed asphalt with cover aggregate surface treatments To increase aggregate retention To provide a uniform dark color

The asphalt emulsion is diluted with an equal amount of water, and the diluted material is sprayed at the ROA of 0.1 to 0.2 gallon per square yard, depending on the texture and dryness of the old pavement. In normal conditions, the separation and evaporation of the water is rapid, permitting traffic within 1 or 2hours.

DUST LAYING

Consists of spraying an untreated surface with a low-viscosity liquid asphalt, such as SC-70, MC-30, MC-70, or a diluted slow setting asphalt emulsion. The asphalt and dilutant penetrate and coat the fine particles and temporarily relieve the nuisance of dust. The material is sprayed at a ROA of 0.1 to0.5 gallon per square yard.

When emulsion is used, it should be diluted with 5 or more parts of water by volume. Diluted emulsion dust-laying treatments usually require several applications. The dust stirred by traffic between applications eventually conglomerates and no longer rises.

This is an effective treatment in a very dusty environment where one application of asphalt is insufficient.

ROAD OILING

Differs from dust laying in that it is usually accomplished as part of a planned build up of low-cost road surfaces over several years. Each application may be mechanically mixed with the material being treated, or it may be allowed to penetrate. The light oils in the road oil penetrate into the subgrade and tend to repel moisture absorption.

The objective in all roads oiling work is to form a dustless wearing surface, combined with a strong water-repelling subgrade. Because soils vary widely, procedures for oiling area matter for local trial and error, rather than scientific analysis.

The amount of road oil, required in the first year of work will vary from0.75 to 1.0 gallon per square yard. The first application is applied at the ROA of about one half of the total; succeeding applications are made in equal amounts. Road oiling treatments are placed several weeks apart, depending upon the character of the asphalt soil mat.

Aggregate Surface Treatment

The sprayed asphalt with aggregate cover surface treatments are applications of liquid asphalt, followed by an application of aggregate. This can be done in one or more layers of construction.

Two types of sprayed asphalt with covered aggregate surface treatments:

SINGLE-SURFACE TREATMENT MULTIPLE-SURFACE TREATMENT

SINGLE-SURFACE TREATMENT

Single-surface treatments are thin, bituminous-aggregate toppings, applied to existing bases or surfaces, such as concrete or asphalt. Construction involves applying a bituminous prime or tack coat to the base or surface. This coating is followed by an application of bitumen and small-sized aggregate. Single-surface treatments are sometimes called seal coats, because they seal the surface of the road or runway.

Sequence of Operationsa.

a. Applying prime coatb. Binder applicationc. Aggregate applicationd. Rolling

Applying Prime Coat

The first steps, such as sweeping, priming or tacking, and curing The binder (bituminous material) is applied over the prime coat with an asphalt distributor

Binder Application

When you are applying the binder, it should be hot enough to spray properly and cover the surface uniformly. After the binder cools and cures, it should bind the aggregate tightly to prevent dislodgement by traffic. Individual aggregate stones should be pressed into the binder but must not be covered by the binder. Approximately one half of the individual aggregate stones should be exposed to traffic. The ROA for the binder material should be between 0.25and 0.30 gallon of asphalt per square yard. For a single-surface treatment, the bitumen must be heated and applied to the surface while hot. The aggregate must be spread and rolled before the bitumen cools. Under no circumstances is traffic permitted to travel upon uncovered fresh bitumen. The distributor should NOT apply bitumen until the aggregate is on hand and ready for application. When the distributor moves forward to spray the asphalt, the aggregate spreader should start right behind it. The bitumen should be covered within 1 minute if possible; otherwise, the increase in asphalt viscosity may prevent good binding of aggregate.

Aggregate Application

The size and amount of aggregate, used for surface treatments, are important. You must use a size that matches the bitumen application rate. For a single-surface treatment, one-half inch to sieve number 4 is needed. The amount of aggregate should be 25-30 pounds per square yard. When aggregate is distributed properly, very little hand work is required. At longitudinal joints, the aggregate cover is stopped 8 inches from the edge of the bitumen to ensure ample overlap of the bitumen coat. All bare spots should be covered by hand spreading, and any irregularities of the distribution should be corrected with hand brooms. Excess aggregate in limited areas should be removed immediately with square-pointed shovels. When the aggregate spreader is properly set and operated, handwork is reduced to a minimum.

Rolling

The aggregate is usually rolled by pneumatic-tired rollers. Steel-wheeled rollers are not recommended by themselves. If used, they should make only one pass (one trip in each direction). The rolling operation should then be completed with the pneumatic-tired rolls. Steel-wheeled rollers produce maximum compaction but must be used with care to prevent excessive crushing of the aggregate particles. Also, these rollers will bridge over smaller size particles and small depressions in the surface and will fail to press the aggregate in these places in the asphalt.

Procedures for Rolling

1. Rolling should be parallel to the center line of the roadway to reduce the number of times the roller must change direction.

2. Succeeding passes should overlap one half of the wheel width of the roller. This action ensures that the aggregate becomes well embedded in the bitumen.

3. Rolling should be completed before the bitumen hardens. This will ensure that the aggregate becomes well embedded in the bitumen.

4. Succeeding passes should be made from the low side to the high side of the surface. This operation maintains the surface crown and prevents feathering at the edges.

5. Rolling should be done at a slow speed.6. Rollers should be only wet enough to prevent bitumen from sticking to the wheels.7. The power wheel of the roller should pass over the unrolled surface before the steering wheel(s)

of the rollers. After rolling and curing, the surface is ready for traffic.

MULTIPLE-SURFACE TREATMENT

A multiple-surface treatment is essentially the same as the single-surface treatment. However, the multiple-surface treatment consists of two or more successive layers of binder and aggregate. This type of treatment is done in stages. Each stage is accomplished in the same manner as a single-surface treatment. The only difference is that each additional layer of aggregate should be about one-half of the size of the previous layer. This allows the smaller aggregate to interlock with the larger aggregate when rolled.