LABORATORY MIXTURE DESIGN FOR FOAMED ASPHALT
ABSTRACT: Foamed asphalt is a
green road material which normally generated using cold-mix system and
frequently used in recycling technology. Due to the unique method to generate
this mixture, it is very demanding to develop mixture design of foamed asphalt
mixture in laboratory. This paper describes the mixture design in three points,
i.e. mixture design considerations, mixture
design process, and a case study. The
mixture design considerations were developed based upon the results of previous
researches. Whereas the mixture design
process was described in step by step.
The case study aplied a mixture generated using a blend of virgin crushed
limestone and RAP aggregates, and bitumen pen. 50/70. The results can be
deduced as follows. It should be considered several kinds for foamed asphalt
mixture design, that are foamed bitumen characteristics, bitumen grade, foamed
bitumen content, aggregate properties, moisture content, mixing process,
compaction process, curing and temperature condition. The mixture design
procedure is proposed in seven steps, i.e. (a) determine the optimum foamed bitumen
properties, (b) prepare the aggregate, (c) mixing process, (d) compaction
process, (e) curing process, (f) property testing, and (g) select the optimum
foamed bitumen content. After running the seven steps, the case study gave the
results as follows. Foams generated at a temperature of 160◦C were selected as
the most stable foamed bitumen. The optimum foaming water content was found to
be around 1.9%. The plasticity index of
the virgin crushed limestone aggregate was 2.7%. The maximum dry density was
2.2 Mg/m3 and optimum moisture content was 4.5%. All mixtures were added water
at 72% OMC, mixed using the Hobart mixer, and compacted using Marshall Hammer.
All specimens were oven cured at 40oC for 3 days. After ITS testing, it was
decided to select foamed bitumen contents of 2.6%.
Key words: Mixture design,
foamed asphalt, foamed bitumen, foaming water content, foamed bitumen content
Author: Sri Sunarjono
Journal Code: jptsipilgg110020
