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Influence of installation damage on the tensile strength of asphalt reinforcement
products
Influence de l’endommagement de mise en place sur la traction des produits de renforcement en
asphalte
Sakou Touole L., Thesseling B.
Huesker Synthetic GmbH, Gescher, Germany
ABSTRACT: One of the major problems associated with the use of asphaltic pavements is reflective cracking. This phenomenon is
commonly defined as the propagation of cracks from an existing pavement or base course into and through a new asphalt overlay,
resulting from load- and/or temperature-induced stresses. One of the proven techniques to reduce/delay reflective cracking is the use
of asphalt reinforcement. The properties of asphalt reinforcement (e.g. tensile strength, tensile strain) are influenced during the paving
and compaction procedures of the asphalt. The loss of tensile strength during those procedures is known as installation damage. The
degree of installation damage largely depends on the raw material used, the number of passes of trucks and compactors. There is
currently a lack of experience and knowledge concerning the real residual properties (what could be termed “effective tensile
strength”) of asphalt reinforcement products after the paving and compaction procedures. This paper describes a test procedure
developed at the University of Aachen. The research illustrates a considerable difference in loss of tensile strength, due to the effects
of installation damage.
RÉSUMÉ : Un des problèmes majeurs liés à l'utilisation d'asphalte pour les chaussées est la fissuration réflective. Ce phénomène est
défini comme la propagation des fissures à partir de la couche d´usure ou de base existante à travers la nouvelle couche d´usure
d'asphalte, résultant des contraintes induites par le trafic et/ou la température. Une des techniques prouvées pour réduire/retarder la
fissuration réflective est l'utilisation d’armature d'asphalte. Les propriétés de l´armature d'asphalte (notamment résistance à la traction,
allongement à la rupture) sont influencées durant la pose et le compactage de l'asphalte. La perte de résistance à la traction lors de ces
procédures, connue sous le terme «Endommagement mécanique», dépend en grande partie de la matière première utilisée, du nombre
de passage de camions et compacteurs. Il existe actuellement un manque d'expérience et de connaissances concernant les propriétés
réelles résiduelles «résistance à la traction efficace» des produits d´armature d'asphalte après la pose et le compactage de l´asphalte.
Le présent article décrit la méthode d'essai développée à l'Université de Aachen. La recherche révèle une différence notable de perte
de résistance à la traction, en raison des effets des endommagements mécaniques.
KEYWORD: installation damage, asphalt reinforcement, effective tensile strength
MOTS-CLÉS : Endommagement mécanique, Armature d´asphalte, résistance à la traction efficace
1 INTRODUCTION
It is well known that cracks appear due to external forces, such
as traffic loads and temperature variations. The temperature
influence leads to the binder content in the asphalt becoming
brittle; cracking starts at the top of a pavement and propagates
down (top-down cracking). On the other hand, high stresses at
the bottom of a pavement, from external dynamic loads, such as
traffic, lead to cracks that propagate from the bottom to the top
of a pavement (bottom-up cracking).
A conventional rehabilitation of a cracked pavement involves
milling off the existing top layer and installing a new asphalt
course, but cracks are still present in the existing (old) asphalt
layers. As a result of stress concentrations at the crack tips
caused by external forces from traffic and natural temperature
variations, the cracks will propagate rapidly to the top of the
rehabilitated pavement.
Deteriorated concrete pavements are typically rehabilitated by
installing new asphalt layers over the old concrete slabs.
Temperature variations lead to a rapid crack propagation
especially at the expansion joints to the top of the new asphalt
overlay.
Asphalt reinforcement has been used worldwide for many years
to delay or even prevent the development of those reflective
cracks in asphalt layers. Currently there are a number of
different asphalt reinforcement and systems made of different
raw materials (e.g. polyester, fiberglass, carbon fiber,
polypropylene...) available in the market. It is not disputed that
each of these systems has a positive effect in the battle against
reflective cracking; however there are differences concerning
the real residual properties “effective tensile strength” of each
asphalt reinforcement after the paving installation procedure.
The properties of asphalt reinforcement (e.g. tensile strength,
tensile strain) are influenced during their installation, the paving
procedure (paver and truck passes) and the compaction of the
asphalt (Figure 1). The result, specifically the loss of tensile
strength of the asphalt reinforcement grid during the paving
procedure, is known as installation damage.
After an asphalt reinforcement product is placed, many asphalt
delivery trucks have to pass over the grid. Additionally there is
the compaction of the hot mix asphalt, during which the
individual filaments or strands of the asphalt reinforcement are
largely influenced by the movement of aggregates, in particular
of coarse and sharp-edged aggregates. Next to the reinforcement
characteristics (flexible or brittle raw materials), the degree of
installation damage by roller compaction not only depends on
the number of passes and the type of compaction (e.g. rubber
tired, static, dynamic), but the weight of the compactor and the
condition of the base layer (e.g. smooth, rough/milled) as well.
