Aggregates in highway construction

Τίτλος

Aggregates in highway construction

Θέμα

Aggregates (Building materials)

Aggregates (Building materials)--Testing

Roads--Design and construction

Δημιουργός

Andreou, Ioannis

Πηγή

Higher Technical Institute

Το πλήρες κείμενο είναι διαθέσιμο από το Υπουργείο Ενέργειας, Εμπορίου Βιομηχανίας και Τουρισμού

Εκδότης

Library of Cyprus University of Technology

Ημερομηνία

1993

Δικαιώματα

Απαγορεύεται η δημοσίευση ή αναπαραγωγή, ηλεκτρονική ή άλλη χωρίς τη γραπτή συγκατάθεση του δημιουργού και κάτοχου των πνευματικών δικαιωμάτων.

Μορφή

pdf

Γλώσσα

eng

Τύπος

text

Αναγνωριστικό

CED0183

Σύνοψη

Since aggregates is the basic material used in the
construction of a pavement the knowledge of the various
characteristics and properties of aggregates, and as well
the way these influence the performance of a pavement is of great importance.
Aggregates are used in various types of bound materials in the upper layers, and unbound granular mixtures in the
lower layers of a flexible pavement.
Aggregates make a major contribution to the structural
strength of the pavement. They provide a stony skeleton
upon which the direct traffic loads are supported.
The strength and toughness properties of an aggregate is a function of the petrology of the rock from which they were produced. Igneous rocks are stronger than sedimentary rocks due to the silica content and the intergranular bond.
Especially, medium-grained basic igneous rocks, e.g. diabase are of the best roadstones and are widely used in bituminous mixes in Cyprus.
The size and shape also affect the strength and stiffness
of a mix. The grading of aggregates is used in the
designing of the pavement in determining the strength of
the pavement. Angular aggregates provide high strength and stiffness due to the interlocking of particles. The size
and shape is a function of the production process.
Aggregates are produced from rock deposits. Through
artificial crushing jagged edge particles are produced and
through screening the crushed material is sorted into the
various sizes.
The mechanical properties, and soundness of aggregates influence the performance of aggregates in a bituminous mix. Aggregates with high resistance to crushing. abrasion
and polishing increase the strength, toughness, hardness
and durability of a bituminous pavement. These properties contribute to the stability and durability of a pavement.
The quality of aggregates are examined through tests on
aggregate samples. The aim of testing is to check whether a certain type of aggregate is suitable to be used in the
construction of the pavement.
The quality of aggregates must comply with the standards
and specifications according to the use in the pavement.
High quality aggregates are required in the upper layers of.
a pavement due to the higher stresses and the direct
contact with the traffic. Aggregates in the wearing course
must be dense gradod, impermeable with low voids content
strong and tough to resist wear due to abrasion by traffic,
to retain the required skid-resistance and stability of the
surface. The requirements for aggregates in the 1 over
unbound layers are less strict and aggregates with not as
high properties are used, e.g. limestone aggregates.