Road materials

 Generally for bituminous or asphalt pavement, the
aggregates constitute 88% to 96% by weight or
more than 75% by volume. The AASHTO standard
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 3 when tested
by AASHTO T-11 and 27”.

SIEVE DESIGNATION MASS PERCENT PASSING

Alternate US
Standard mm Std. Grading A Grading B Grading C Grading D

25 1" 100 100 100 100

10 3/8 50-85 60-100

5 No. 4 35-65 50-85 55-100 70-100

2 No. 10 25-50 40-70 40-100 55-100

0.5 No. 40 15-30 25-45 20-50 30-70

0.075 No. 200 5-20 5-20 6-20 8-25

GRADING REQUIREMENTS

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 percent 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 percent of the particles retained on the 4.75 mm
(No. 4) sieve shall not have at least one fractured face.
 The fraction passing the 0.75 mm (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.

 The presence of organic impurities in the intended for concreting
road pavement may cause slow or non-hardening of the concrete.
Under AASHTO T-21 standard test, the aggregate is treated with a
mixture of Sodium Hydrochloride Solution and when the treated
aggregate turns dark, organic materials are said to be present in
the aggregate.
 The strength of fine aggregate is measured by the compression
tests of sand-cement mortar.
 Soundness of fine aggregate is measured by their resistance to
deterioration under the action of solutions of Sodium or
Magnesium Sulfate. The sodium sulfate test is five cycle. The
maximum loss under AASHTO specifications is 10%.

 For coarse aggregate the requirement consists of
crushed stone, gravel, blast furnace slag, or approved
inert materials of similar characteristics or combination
thereof having hard, strong durable pieces free from
adherent coatings.

The Department of Public Works and Highways standard
specifications classify aggregate under Item 703, and
specifically provides that:
 Aggregate shall consist of hard, durable particles of fragments of
crushed stone, crushed slug or crushed or natural gravel.
 Coarse aggregate is the material retained on the 2.00 mm (No.
10) sieve and shall have a percentage of water or more than 50
for sub-base and not more than 45 for base and surface courses
as determined by AASHTO designation test T-96.
 Fine aggregate is the material passing the No. 10 sieve (2.00 mm)
consisting of natural, crushed sand and fine minerals particles.
The Fraction Passing the 0.075 mm (No. 200) sieve should not be
greater than 0.66 (2/3) of the fraction passing the 0.425 mm (No.
40) sieve.

 The strength of the road pavement will be
increased if dust additives which denses the
graded mixture is added. It is called mineral
filler which reduces the void contents in the
mixture. This dust additive is not the ordinary
dust that is being found in our floor or tables.

Dust additive is classified into:

 Finely powdered limestone
 Slag
 Hydrated lime
 Portland cement
 Trap rock dust
 Fly ash

 The DPWH standard specifications relative to mineral
filler states that:
 “Mineral filler shall consist of finely divided mineral matter
such as rock dust, slag dust, hydrated lime, hydraulic
cement, flyash or other suitable mineral matter. It shall be
free from organic impurities and at the time of use shall be
sufficiently dry to flow freely and shall be essentially free
from agglomerations.”
AASHTO M-17 provides that:
 Percentage passing by weight shall be as follows:
 No. 30 (0.66 mm) sieve 50
 No. 50 (0.30 mm) sieve 95-100
 No. 200 (0.75 mm) sieve 70-100
AASHTO further stipulates that for all materials
other than hydrated lime or Portland cement, the
Plastic Index (PI) value shall be 4 or less.

Bituminous material or asphalt is a viscous (gelatinous) liquid
used as binder for aggregates in road construction. At normal
temperature, asphalt is either lightly thicker than water or hard
but brittle material that breaks under a hammer blow when
cold.
 Bituminous material is in liquid form when mixed or combined
with aggregates. This liquid form maybe produced either by
heating the hard asphalt, by dissolving in solvent or by
emulsifying in water. However, there are bituminous liquid
materials available and ready to use.
 The action of the asphalt binder depends on its type and the
aggregate it is combined with. The purpose of the asphalt
binder is to resist the abrasive force brought about by heavy
traffic.

 If the pavement is of the open type, consisting entirely of
coarse particles and asphalt, heavy binder is needed
requiring more asphalt. On the other hand, if the
aggregates on the pavement contain fine particles,
cohesion will be developed by the surface tension in
the thin asphalt film surrounding these fine [articles
hence, less viscous asphalt is required.

 Asphalt cement is used as binder for almost high types
of bituminous pavement. Asphalt cement is a semi-
solid hydrocarbons retained after fuel and lubricating
oils are removed from petroleum. The softest grade
used for pavement is the 200-300 penetration and the
hardest is the 60-70 penetration.

 Penetration refers to the consistencies of asphalt
cement as describes under AASHTO T-49. It is the
distance that a standard needle penetrates a sample
under known conditions of loading time and
temperature. Recently, the procedure used in grading
asphalt cement is viscosity test rather than the
penetration test.


 Cutback or Liquid Asphalt
 The liquid asphalt is a petroleum product
consisting of asphalt cement with a liquid distillate
(diesel, kerosene or gasoline). The less viscous
asphalt contains up to 50% diluent and the more
viscous contains diluent as little as 15%.
 The use of cutback is being frowned for two
reasons:
 It is a usable fuel.
 It is an air pollutant.
 Cutback or liquid asphalt is classified into:
 Slow Curing (SC) road soils
 Medium Curing (MC) cutback asphalt
 Rapid Curing (RC) cutback asphalt

 Emulsified Asphalt is a kind of mixture
wherein the minute globules or asphalt
disperses in water. Asphalt content ranges
from 55% - 75% by weight. Emulsion could be
applied or mixed at normal temperature,
because when the water content evaporates the
asphalt remains.

Oxidized Asphalt and Road Tar
 Oxidized asphalt is suitable only for roofing and
similar applications. Highway uses of oxidized
asphalt are limited to water proofing of structures
and filling joints of concrete pavement.
 Road tar is a by-product of the distillation process
of coal. Tars are produced from gashouse coal tar;
cook ovens tars and water gas tar.

Bitumen – Rubber Mixture for road pavement was
experimented in Holland way back in the year
1929. It was adapted in the United States in 1947
and later in European countries.

Epoxy Resins as Binders
 Epoxy binders are produced in clear, dark,
rigid and flexible forms for application to either
concrete or asphalt pavement. Hardening is
attained by mixing resin and catalyst hardener
immediately before application. The result is
thermosetting. Meaning, it will not soften
under the influence of heat or the action of
solvent such as water or petroleum products.
But the prohibitive cost of the resin has
restricted its use to bridge surfacing and to
other special non-skid seal coating surface
only.

Road materials

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Road materials