TECHNICAL
COMPETENCIES OF TLA
Improvement in mix
stability
The “job
mix”, or the “design mix” as it is also sometimes called, refers
to the ratio of bituminous binder to aggregates of varying sizes as
outlined by the job’s specification. Because of the integration of
dissimilar components, in this case, a hydrocarbon with stony matter,
there exists the tendency for the entire mixture to lose its
homogeneity, or breakdown. The inclusion of TLA to the mixture
presents inorganic matter that is evenly distributed in such a way as
to reduce the natural tendency of the mix to breakdown, or become
prematurely unstable.
Increased stability
at high temperatures
Due to the
hardness of TLA (possessing a penetration of between 0 and 4), its
softening point is naturally higher (930C) than soluble
bitumen; therefore, its tendency to react to imposed forces (heat,
pressure) is deferred significantly. This augurs well for any design
mix, since it is an indicator that a TLA paving would be resilient to
extreme temperatures.
Increased strain
performance at low temperatures
Strain,
being an
engineering materials phenomenon defined by the elongation of a
material as a ratio to its natural length due to applied tension, the
ability of a TLA-blended mix to resist cracking under low temperatures
is yet another performance-related characteristic. This allows it to
yield incomparable results over a wide spectrum of extreme conditions.
Despite its hardness, TLA outperforms the strain resistance of
refinery bitumen by 28% at –100C.
Source: Graph # 3,
performance at low temperature, “Trinidad Lake Asphalt; A unique
naturally occurring bitumen binder for improving the performance of
asphalt pavements in roads, airports, tunnels and similar heavy duty
sites.”
Reduced cracking
Pavements
are subject to the harshest of conditions that include extreme
temperatures, sharp temperature gradients, and heavy loads, promoting
unwanted compression, shear and other mechanical drawbacks. Many of
these manifest themselves as cracks in the surface, which are
unsightly at best. The worst of these continue for such length as to
eventually result in a total divorce of one part of the roadway from
the other. As a consequence of improved mix stability, the incidence
of these is either reduced or negated by the use of TLA.
Reduction in surface breakup
Being an
amalgamation of mainly aggregate and polymer-based binders with
optional or recommended additives, a pavement’s entire section is
always under a series of varying stresses. It is the occurrence of
abrasion and the direct ultraviolet exposure that can result in
loosening and eventual dispersion of the surface, for which, the
higher quantities of maltenes promote binding capabilities and
therefore suppresses the likeliness of surface breakup.
Increased resistance to fatigue
As a result
of its higher specific gravity (up to 40% more than conventional,
straight-run bitumen), TLA is remarkably resistant to fatigue in
several forms, including compression and shear. Its higher density
encourages a reduced tendency for inorganic matter movement and hence,
higher fatigue-resistance.
Reduced maintenance costs
The costs
associated with downtime arising out of routine or remedial
maintenance is a woe of even many a first class paving, which TLA is
never purported to eradicate, but rather, reduce tremendously. Due to
longitudinal shear, surface shear, daily positive
and negative temperature gradients and other natural and subjective
pressures, the asphalt’s entire section is eventually compromised to
result in failure that warrants routine maintenance, and sometimes
unforeseen costs. The use of TLA automatically reduces the maintenance
effort sometimes by as much as 70%, quite often making it an eventual
lower-costing alternative that many other modifiers.
Improved skid-resistance and road
safety
This
being the flagship
of TLA characteristics, high speed and heavy-duty users know of the
virtue of anti-skid performance related to safety. Because better
coatability is achieved in using a TLA binder over a soluble binder or
other modified binder, the surface of the aggregate, as well as the
force of cohesion between them, is more ‘polish-resistant’,
allowing for a surface that is yields better tyre-to-asphalt traction,
and thus, far less tendency to skid.
Improved ease of handling in bad
weather conditions
Low
temperatures and rain always present a problem for the smooth and easy
handling of many road-surfacing applications. For hot mix pavements,
this is an increased issue since the preferred temperature of laying
the asphalt lies within a reasonably close tolerance. Although bad
weather conditions only serve to promote the counterproductive
environment of cooling, the heat-retention properties of TLA tend to
counteract the urgency of any undesirable cooling, making it easier to
handle in bad weather as a result of the material staying in its
loose, mixed form longer.
Ability to be mixed with almost all
other binders
As a
testament to its affinity for binders, TLA can be mixed with all known
polymers and polymer-related bituminous compounds. Being essentially a
hydrocarbon that is chemically bound to interlocked inorganic matter,
TLA resists the tendency for separation and sedimentation of other
non-TLA binders, and this is what has enabled TLA to be used in 31
different countries around the world, each with equal success. In its
native origin of Trinidad, it is blended with 180-200 penetration
bitumen in measured proportions to produce a superior blend of 60-70
penetration TLA that is used on highways, airports and marine
terminals.
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