Production of bitumen-emulsions

Document Sample
Production of bitumen-emulsions Powered By Docstoc
					Production of bitumen-emulsions
Application of emulsions in different road construction technologies
Surface dressing
Cold mixes
Slurry Seal
Valga Teed Ltd

   1. Production of bitumen-emulsions
Valga Teed Ltd started production of Bitumen-emulsions since 2005. Technology and recipes
are French origin.

2005 three types of emulsions were produced:

   1) BE 50 R (C50B3) – for tack coating
   2) BE60M (C60B4) – for patching and stabilization works
   3) BE65R (C65B3) – for surface dressing works
      After first season additional type of emulsion were introduced:
   4) BE65R (C65B3) – specially for surface dressing with crushed gravel
      Earlier the emulsion BE65R (C65B3) was used for surface dressing works only with
      granite stone.
      As result of second season of working the emulsion with bigger bitumen content was
      introduced. New standard (EN 13808:2005) enabled to determine more precisely new
      type of emulsion:
   5) C 67 B 3 – used for surface dressing with granite stone and crushed gravel. Mentioned
      emulsion enables to do work requiring bigger content of binder. At the same time the
      emulsion rates used could be reduced due to larger bitumen content in emulsion.
      In 2007 also new emulsion type especially for cold mixes with longer reacting time
      was introduced:
   6) C65 B 4 – it was tested in three different technologies: construction of pavement
      milling in site crushed gravel and emulsion; construction of pavement milling in site
      crushed limestone and emulsion; construction of pavement using surface dressing
      technology with crushed lime stone and emulsion.
      In future bitumen-emulsion C 69 B 3 will be introduced.

Main differences from other bitumen-emulsions produced in Estonia:

     • Faster breaking of emulsions in surface dressing works. In hot weather breaking stars
         immediately after spraying. Technologically it means that laying of crushed stone
         and compaction must follow immediately the spraying of emulsion and pouring of
         sand is not necessary
     • Better mixing if used as binder in cold mixes
Application of emulsions

Description of some widespread technologies with emulsions

       2. Surface dressing
2.1.     Surface dressing creates to the road surface protection against tear wear and weather.
     Surface dressing layer is built by spreading binder and filling material with appropriate
     gradation composition.
2.2. Surface dressing is used to improve pavement surface performance, to create dust-free
     surfaces, to form fresh wearing course, to improve friction qualities as well as enhance
     aesthetic values of pavement.
2.3. Following aggregates can be used for surface dressing:
- aggregate corresponding to certain grading requirements;
- all-in aggregate;
- aggregate corresponding to certain grading requirements pre-treated with bitumen.

2.4.       Selection of suitable surface dressing method depends on state of pavement and traffic
       conditions. Recommendable range of use most common surface dressing types are as
       follows:
       - Single surface dressing. Used in light and medium traffic road where pavement is
           uniformly damaged
       - Single surface dressing with double application of chippings. Used in heavy traffic
           roads, crossings, sharp curves and ascents.
       - Single surface dressing with pre-application of aggregate. Analogous as above.
       - Double surface dressing. Strongly damaged surface with ravelling, cracks, unevenness
           or heavy traffic
       - Double surface dressing with pre-application of aggregate. On gravel roads and
           heavily damaged asphalt pavements.
       - Surface dressing with crushed gravel and all-in aggregate. On gravel roads and roads
           with light traffic.

Binders for surface dressing can be bitumen-emulsions, shale-oil bitumen, bitumen, modified
bitumen.

Advantage in use of emulsions: it can be applied warm or cold; emulsifier containing in
emulsion acts as surface-active agent and improves adhesiveness between binder and
aggregate; water in emulsion improves adhesiveness with wet aggregate.



3. Cold mixes using milled old asphalt
First preliminary mix design will be determined where following is indicated:
    - percentage of added fresh aggregate and its qualities;
    - percentage ant type of added binder;
    - necessary moisture content in mixture for optimal compaction
Base on experiences, in preliminary mixture design, following composition of materials can
be considered:
    - milled old asphalt – 65–75 %
    - crushed stone 12-16 mm – 25-35%
    - Bitumen-emulsion – 1,2-2,2%

Mixing and construction of cold mix layers is recommended to do in site. It helps to prevent
the fragmentation of mix.

In site mixing procedures:
    - Laying of required quantity of old milled asphalt on the road
    - Planning and compacting of old milled asphalt layer
    - Laying of required quantity of crushed stone on top of old milled asphalt layer
    - Planning and compacting crushed stone layer
    - Mixing of old milled asphalt and crushed stone layers with cold recyclers adding at the
        same time bitumen-emulsion
    - Laying and compacting of mix should be performed before breaking of emulsion (no
        later than 5 hours after adding emulsion)
    - Cold mix layers should be covered with weatherproof layers (usually surface
        dressing). Moisture content must not exceed before covering 2-2,5%


4. Slurry seal
Slurry shall consist of mixture of approved bitumen-emulsion, fine mineral aggregate, filler,
water and specified additives, proportioned, mixed and uniformly spread over properly
prepared surface. The completed slurry seal shall leave a homogeneous material, adhere
firmly to the prepared surface, and have friction-resistant surface texture throughout its
service life.
Exact composition of slurry mixture shall be determined by the laboratory tests.
The application of slurry seal will significantly extend the life of existing pavements by
protecting the under-surface from effects of aging and the environment, filling smaller cracks,
preventing of evolving of new cracks. It improves also the surface performance, friction-
resistance and aesthetic values of pavement.
Slurry seal technology can be applied on highways, streets and parking lots, squares etc.
Advantages of slurry seal compared to surface dressing:
    - Very quickly practicable (about after half an hour the road can be opened to then
        traffic)
    - There will be no loos aggregate on road surface
    - Creates very good surface for road marking
    - Ability to repair smaller defects of pavement
    - Pavement surface doesn’t rise
    - No need for adjustment of manhole covers
    - Quit cheep method for improving of durability, appearance, and performance qualities
        of pavement
The thickness of slurry seal layer depends on the size of aggregate and is usually in range of 3
to 20 mm. Most usually about 10 mm thick layers are used. Slurry seal with finer aggregate is
used on road and lots with less traffic whereas slurry with coarser aggregate on roads with
bigger traffic. Depending on aggregate size the rate of application is 4-14 kg/m2.
For manufacturing and spraying of slurry seal special equipment mounted on truck is used.
5. Summary
Before bitumen-emulsions were introduced in Estonia somehow similar binder was used here.
It is local material shale oil. Shale oil has proved as a good material in past and is still in some
extent used in road industry in Estonia. But environmental issues, shortage of shale oil and
need to implement number of new methods and technologies in road keeping have resulted to
look for different binders. Bitumen-emulsion is material which has been used in other world
widely for many decades. Now we may say that many years in Estonia as well. It has been
given us possibility to apply wide range of new technologies and methods for road
construction, repair and keeping. However continuous development and learning how to make
bitumen-emulsions which would fit with local conditions, materials, technology requirements
and standards must be carried on.

				
DOCUMENT INFO
Shared By:
Stats:
views:24
posted:5/18/2012
language:English
pages:4
Description: Production of bitumen-emulsions