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Asphalt Recycling -Experiences from Germany
Dipl.-Ing. Sven Gohl
Leonberger Straße 208/1
71063 Sindelfingen
+49 7031 / 708 79 24
Germany in the European context
Facts from the EAPA report for Germany
Over all 39 million tons of asphalt mix produced
in 2015
Approximately 610 mixing plants
About 10 million tons of reclaimed asphalt are
used for the production of new asphalt mixes
90 % of the recycled asphalt is reused in hot mix
asphalt
Germany in the European context
Some facts from the EAPA report „Asphalt in figures 2015“
Country Total pro-
duction of
hot mix
asphalt in
mio. tons
recycling
rate in hot
mix asphalt
Germany 39,0 25 %
Denmark 3,7 18 %
Netherlands 8,0 39 %
Sweden 8,2 15 %
France 31,5 15 %
Asphalt recycling in Germany
Requirements for increased reuse of RA in Germany
Tender documents allowing increased reuse of RA
Layer wise milling, also as a claim in the construction contract
Better storage conditions
Better technical features of mixing plants
(use of parallel drum for gentle heating of RA)
Selective feeding of RA in various hoppers
Constant updating of the technical rules for asphalt recycling and re-using
Expected impressions
Asphalt recycling in Germany
(picture from the German asphalt association)
Asphalt is milled separately for
each asphalt layer
Separate storage of recycled
asphalt stockpiles from different
job sites
Well-prepared for reusing in hot
mix asphalt
5
©dav
Expected impressions
Asphalt recycling in Germany
In best-case there are storage facilities / warehouses at mixing plants
6
Storage in real life
Asphalt recycling in Germany (the current problem)
7
~50.000 to ~10.000 to ~20.000 to
Actual problems at mixing plants / at jobsite
Asphalt recycling in Germany (in reality)
Storage capacities will be overloaded for a long time
Contract for the supply of hot mix asphalt is often won by the bidder, who can
storage the highest amount of RA (or the bidder who is even able to store RA)
Selective storage of RA is not possible due to lack of storage capacity
Usually there are 3 big stockpiles
for asphalt wearing courses
for asphalt binder course
for asphalt base course
with varying quality
8
Oversupply of reclaimed asphalt
Reasons for the oversupply of reclaimed asphalt
1. Public tendering focuses on the maintenance of the existing road network; new
roads in planning do barely exist
► The total amount of reclaimed asphalt corresponds with the required hot mix
asphalt / warm mix asphalt at jobsites
2. Limitation for re-using of reclaimed asphalt by the technical regulations
9
Technical regulations in Germany
10
connect
implementation
in construction contract
supplemented
Technical supply
conditions for
reclaimed asphalt
Code of practice
for utilisation of
reclaimed asphalt
Technical supply
conditions for
asphalt used in
road constructions
Additional
technical contract
conditions and
guidelines for road
constructions
Limitations of the technical regulations
Contract rules for Stone Mastic Asphalt
According to EN 13108-5 and TL Asphalt-StB 07/13 it is allowed to reuse reclaimed
asphalt in SMA
It is excluded in the construction contract (ZTV Asphalt-StB 07/13)
► 1.2 million tons of asphalt wearing course mixes is SMA,
the addition of 25 % reclaimed asphalt to SMA mixes would lead to an increase of
the total amount of reused reclaimed asphalt of about 300.000 tonnes (3 % higher
recycling rate for whole Germany)
11
Limitations of the technical regulations
Mix design according to the Technical supply conditions (TL Asphalt-StB)
The maximum amount of reclaimed asphalt which can be added depends on:
The homogeneity of the reclaimed asphalt,
The suitability of the reclaimed asphalt for the designated asphalt mixture (mix
design) and
the technical set-up of the respective asphalt mixing plant
12
The lowest of these three values is to be used
as the basis for the amount of RA to be added.
Limitations of the technical regulations
Homogeneity of the reclaimed asphalt
based on the following characteristic values:
binder content,
softening point ring-and-ball
particle fractions
0 to 0.063 mm and
0.063 to 2 mm and
> 2 mm
at the relevant extracted aggregate mixture.
13
Limitations of the technical regulations
Overall tolerances Tperm of relevant characteristics
14
TPerm
Property
Asphalt mixture for asphalt wearing
courses, Asphalt mixture
asphalt binder courses and for
combined asphalt base and wearing
courses
Asphalt mixture for asphalt base
courses
Softening point Ring-and-ball °C 8 8
Binder content M.-% 0,8 1,0
Particle fraction < 0,063 mm M.-% 6,0 10,0
Particle fraction 0,063 to 2 mm M.-% 16,0 16,0
Particle fraction > 2 mm M.-% 16,0 18,0
Zi =
0,5 ● Tzul,i
● 100ai
AC T
AC TDZi =
0,33 ● Tzul,i
● 100ai
AC D
AC B
Formula 1: Formula 2:
- generally for softening point ring and ball
Tolerance of ZTV Asphalt-StB 07/13
+/- 0,4
+/- 3,0
+/- 8,0
+/- 8,0
+/- 8,0
+/- 9,0
+7,0/- 3,0
+/- 0,5
Limitations of the technical regulations
Homogeneity of the reclaimed
asphalt
The maximum amount of RA to be
added can also be determined
graphically as a function of the range of
the characteristics using the nomogram.
15
A classification for a stockpile with an
amount of, for example, 5.000 tons RA is
possible and practicable.
Limitations of the technical regulations
Homogeneity of the reclaimed asphalt
when there is stockpile with 30.000 tons (for example) of RA, you need a very
intensive support of a laboratory because of varying characteristics and conditions
daily control of the part of the stockpile which is added in asphalt mixture
continuous re-adjustment of the recipes according to the actual test results
…
Quality management (QUALITY IS NO COINCIDENCE!!!)
Communication
Transparency
16
With a high intensity of quality control you can achieve high quality standards !
Limitations of the technical regulations
Mix design:
Mix design has to ensure, that the resulting mixture meets all requirements of the
technical supply conditions
binder content and properties
grain size distribution and aggregate properties
asphalt properties (void content, deformation resistance, etc.)
► Maximum addition of RA is often restricted by the resulting amount of filler,
the softening point ring-and-ball and the elastic recovery
17
Limitations of the technical regulations
Determine the maximum possible amount of RA depending
on the filler content (example)
Typical value for the filler content in reclaimed asphalt is about 12 M.-%
For example the range for filler in asphalt binder courses is 3,0 to 7,0 M.-%
With regards to the filler coming from other components, the recycling rate is limited to
maximum 50 M.-%
18
Maybe additional regulations
for binder content are
necessary when filler content
is exceeded ???
Limitations of the technical regulations
Determine the maximum possible amount of RA depending
on the softening point ring-and-ball
19
requirement
(specified) bitumen
50/7050/70 TR&B
70/10050/70 TR&B
Softening point of the
reclaimed asphalt
Softening point of the
neat bitumen added
it is also allowed to use a one grade softer bitumen
Limitations of the technical regulations
Problems / Challenges
More consideration is given to the binder, especially the hardness due to aging
► Is the softening point the right test to sufficiently describe binder properties?
► Do we need other relevant practical tests or performance tests to describe binder
characteristics?
Effect of double coating ! The softest bitumen which can be used is 70/100, maximum one
grade softer as the required bitumen.
► To prevent the effect, validation of mixing time is necessary !
20
Double coating?
- no transfer from „old“ binder
to „fresh“ aggregates
- „old“ binder is coated by „new“
softer binder
Particle with 15 °C
new aggregates
► Sufficient mixing time
Limitations of the technical regulations
Quelle: STORIMPEX
Limitations of the technical regulations
Mixing time 15 sec
Mixing time 45 sec
► Sufficient mixing time
test mixtures to determine
the dry mixing time are
absolutely necessary
Limitations of the technical regulations
Example: parallel drum of an old
mixing plant
Maximum achievable temperature of
RA: ca. 140 °C
Maximum RA ratio in asphalt base
courses: ca. 70 M.-%
23
A homogeneous binder coating of all
mineral aggregates and a sufficient
temperature of the resulting asphalt mix
require an adjustment of the temperature
of the virgin aggregates
Cold addition of RA requires much
higher temperatures of the virgin
aggregates („super-heating“)
This can be the reason for rapid ageing
of the binder
Limitations of the technical regulations
The key to high quality asphalt mixes incorporating high amounts of RA is to ensure that the
binder homogeneously coats all aggregates, hence the viscosity of the binder is also crucial
Reducing viscosity to make coating easier has generally been achieved by elevating the
binder temperature.
24
WARM MIX ASPHALT
technology Germany ???
Production of warm mix
asphalt in million tons (EAPA)
Summary
In Germany there is a very high recycling rate for RA in hot mix asphalt
Neverless there is an oversupply of RA due to the de-balance of maintenance
work and the expansion of the road network
That`s why we have to change our view on some details in the technical
regulations
Inflexible requirements need to be opened with regards to:
Re-using of RA in all asphalt mixtures
Release the limits for the softening point ring-and-ball, elastic recovery
Relevant and practical performance tests for binder and asphalt mixture are necessary to
describe the real performance
Application of reliable technologies (warm mix asphalt)
Focussing on the resulting mixture, not on single parameters ! 25
26
Thank you for listening !