Affiliation(s)
1. Department of Civil Engineering, University of Palermo, Granada 18015, Italy;
2. Department of Civil, Materials and Environmental Engineering, University of Palermo, Palermo 90134, Italy
ABSTRACT
The impact of temperature on the mechanical properties and thermal
susceptibility of the railway bituminous sub-ballast layer, has served as
motivation to develop the advanced measurement of thermal cycles in this layer
and, an evaluation of the average seasonal temperatures interpolated by sinusoidal functions, of which
characteristic parameters are determined. According to weather situation, Barber’s temperature model
was used to prove the effectiveness for the
railway superstructure. It is included the assessment of improved modified
asphalt mixes performed with coarse rubber from scrap tires, having 1.5 to 3
percent of crumb rubber (particle size 0.2-4 mm) by weight of the total mix, as sub-ballast layer in railway and base
layers on roads, recurring to the Superpave mix design compaction enhanced
after computer simulations to evaluate real stresses derived from the rail
traffic and climatic conditions. This article
following the assessment of the average seasonal temperatures, involves the
characterization of rubberized materials with attention to crumb rubber
properties, designed with dry technology, to enhance the bitumen-rubber and binder-voids ratios. Indirect tensile
strength and water sensitivity tests were applied for the evaluation of its mechanical properties including dynamic complex
modulus at elevated temperature to measure the amount of bitumen absorbed by
the rubber. The rubberized mix-results obtained and the comparison with a
conventional HMA (hot mix asphalt) show that these dry
rubber bituminous mixtures are particularly effective in damping vibrations.
The purpose of using rubber modifiers in hot mix asphalt to obtain a
stiffer-elastic sustainable material has been achieved for the assessment of
its behavior in sub-ballast/base layers.
KEYWORDS
Superpave, rubber-modified asphalt, bituminous mixtures, temperature,
compaction, sub-ballast, railway, indirect tensile strength, trackbed design.
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