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.