Abstract:
Thin Asphalt surfacing (TAS) is an innovative idea that has the potential to lower
construction and maintenance costs of road construction in Sri Lanka. Laboratory based
studies conducted in Sri Lanka have shown that the local materials can be used to produce
TAS, and this study focuses on the usability of TAS in the field. Few concerns were found
when applying this new technology in the field was taken into consideration before field
trial. Such as: (1) The possibility that variations in the gradation of aggregates within the
specification limit could negatively affect the characteristics of asphalt mix. Investigations
were conducted to look at the impact of coarser and finer gradations on Marshall Properties:
these grades represent the upper and lower limits of the proposed specification range, where
both mixtures fulfilled the requirements. (2) The impact of the top level of longitudinal
profile tolerance on the actual thickness of the asphalt mat. Increase in the proposed layer
thickness from 25 mm to 30 mm, and adding additional surface top level correction of the
base layer to meet the top level of longitudinal profile tolerance of ±10 mm are the options
that have been suggested to meet the specified thickness conditions for TAS, where it was
found that both approaches can be advantageous. (3) The rate at which heat is released by an
asphalt layer that is thinner than traditional asphalt layer. The results of the laboratory-based
testing show that paving around 8 a.m. leaves the least amount of time for compaction. This
occurred because the temperature of the ground and the surrounding air was low . Findings
on the time for compaction in the morning and evening are quite comparable. This similarity
shows that base temperature is more significantly impacted by solar flux than the mix
temperature. After the conclusion of surveys and laboratory experiments, it was decided to
trial TAS in a road in the Gampaha district with low volume traffic. Construction was done
in two sections. Section 1 was constructed with a 30 mm thickness and Section 2 with a 25
mm thickness. Under the test section's field conditions, the results for 30 mm layer thickness
were significantly better. The temperature reduction of the asphalt layer surface over time
was observed during the trial and the time available for compaction was less than 20
minutes. Through this study it was verified that TAS mixtures within the proposed aggregate
gradation limit, satisfy specification requirement, top level surface tolerance of the base layer
should be adjusted to ±10 mm, it is advantageous to have 30 mm thick TAS layer rather than
25 mm TAS layer considering the fluctuations of surface level of base layer and sunny noon
time is more favourable to lay TAS considering the time available for compaction. It was
identified that 30 mm thick TAS sections is more attainable than 25 mm thick TAS section
during field applications
Citation:
Dishan, M. (2022). Field evaluation of thin asphalt application in low volume roads in Sri Lanka [Master's theses, University of Moratuwa]. Institutional Repository University of Moratuwa. http://dl.lib.uom.lk/handle/123/21688