Asphalt Recycling - Experiences from Germanydoccdn.simplesite.com/d/26/73/282600885181707046/4bf0830c-3435-4465...Germany in the European context Facts from the EAPA report for Germany

Asphalt Recycling -Experiences from Germany

Dipl.-Ing. Sven Gohl

Leonberger Straße 208/1

71063 Sindelfingen

[email protected]

+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


(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


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


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

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The lowest of these three values is to be used

as the basis for the amount of RA to be added.


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


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


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.


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

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With a high intensity of quality control you can achieve high quality standards !


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


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 ???


Determine the maximum possible amount of RA depending

on the softening point ring-and-ball

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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


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 !

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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


Quelle: STORIMPEX


Mixing time 15 sec

Mixing time 45 sec

► Sufficient mixing time

test mixtures to determine

the dry mixing time are

absolutely necessary


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


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.

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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

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Thank you for listening !

Documents

Asphalt Recycling - Experiences from Germanydoccdn.simplesite.com/d/26/73/282600885181707046/4bf0830c-3435-4465...Germany in the European context Facts from the EAPA report for Germany