Category Archives: Road construction industry

Bitumen emulsion for road construction is a colloidal dispersion consisting of two components, bitumen and water that do not blend.

The emulsion for road construction is made by the dispersion of bitumen in water solvent of emulsifier.

The performance characteristics of the latter influences the process of bitumen emulsion production.  One way (direct) is that bitumen is dispersed in water.  The other one (reverse) is that drops of water are distributed in the bitumen.

In the road construction industry, bitumen emulsion is more desirable because of its relatively low viscosity.  The name of this emulsion, bitumen emulsion for road construction, gives us a rough idea of the fact that this emulsion is used for paving or treating road surfaces such as repairing potholes and providing a tack coat for the road base.

There are many production methods as well as applications for bitumen emulsions.  The emulsion for road construction usually will consist of 50-70% bitumen, 30-50% water and 0.6 to 1.6% emulsifier.  The exact mix will depend on the application and the recipe.

Emulsification of bitumen can be realized by using special equipment.  In producing bitumen, the components are mixed by means of a colloid mill or ultrasound hydrodynamic cavitation.

The usage of an ultrasound system for blending is unique ans special.  The system is based on ultrasound hydrodynamic cavitation.  This system is used to make solution homogeneous by means of pressure fall and the separation of bitumen particles.

Additionally, this equipment also operates according to a colloid mill principle with a minor load.  The advantages of such a blending of emulsions are as follows: (1) exact metering control of the components; (2) blending cycle time reduction; and (3) non-use of blending containers that ensure a homogeneous final product.

Such performance characteristics such as safety, environmental friendliness and service life extension should be mentioned while speaking about the advantages and quality of the bitumen emulsion itself.

It is therefore, bitumen emulsion for road construction that enjoys a wide popularity in many branches of the economy.  The performance characteristics listed above  can be supplemented with the following: (1) no need to warm up the mixture before using; (2) possibility to work with this emulsion at a low temperature (up to +5°C/41º); (3) fire prevention; (4) energy and labor cost reduction; (5) compatibility with multiple kinds of solid materials; (6) better adhesion to mineral materials owing to the emulsifier; and (7) less discharge of pollutants into the air.

The rapid technological and scientific development changes the traditional compositions of bitumen emulsion. In combination with progressive technology, these allow to produce a wide spectrum of emulsified materials with improved performance in comparison with traditional asphalt technology.

Research of the trends in bitumen material development shows some of the most promising directions, such as:

– production of multiple emulsions with structure similar to inverse emulsions. The production is possible by preparing reverse emulsions or highly concentrated bitumen emulsions.

Amounf the many advantages of bitumen emulsion is the higher viscosity and mobility compared to regular emulsions. The disadvantage is the lack of flow during application.

Such emulsions are also quite economical even with low dispersed phase content.

Most innovations into multicomponent emulsions are related to selection of the corresponding components: polymer surfactants for better stability and surface contact etc. A method for formulating the composition of multicomponent emulsions with consideration of material for application and stability in extreme operating conditions has also been developed. The result is a material that adapts to the existing road top.

– production of monodispersed emulsions. In the general case, the composition of road construction emulsions is polydispersed, but that does not mean that such emulsions are of no interest. Application of such emulsions makes a material with better optical properties, as well as colored materials with minimum amounts of dye.

Dispersion consist of water bitumen emulsion defines its viscosity and settling rate. The latter is defined by size distribution emulsion droplets. In theory, production of an emulsion with the required drop size would allow control of the above parameters.

– production of “dry” emulsion. This product can be made from regular emulsion by mixing a special polymer into the water phase. This polymer causes formation of capsules with water droplets. The advantage of “dry” emulsions is the ability to mix several components, which do not usually mix. The ability allows to combine several various construction materials in the emulsion.

A new age in road construction began on 9 May 1922. Hugh Alan McKey registered the first bitumen emulsion patent. Within several years the application of this new material significantly changed road construction.

The amount of bitumen emulsions made in France in 1923 was several hundred tons. In 1924 it increased to 2500, and to 6000 tons in 1925. Other countries followed. By the end of 1926 the total amount of emulsion made in Germany, Britain, India, Australia and Denmark reached 150000 tons.

France increased production as well (2000000 in 1935 and 300000 tons before the start of WWII).

After the war the amount of emulsion production kept increasing.

Cationic emulsions first appeared in 1951. Their performance pushed anionic emulsion from the market. If in 1962 the ratio was 50/50, in 1971 cationic emulsions accounted fro 92% of the market. At the time the portion of bitumen in the emulsions was 60-69%.

The United States used 100000 tons of emulsion for road construction in 1953, West Germany used 140 000 tons. The amount of material used in other countries was slightly less.

Mineral materials used in road construction are silicate materials. On contact with water these materials become negatively charged, hence the higher adhesion with cationic emulsions.

The British standard BS 812:1960 regulates sampling and testing of filling material used in road construction in the UK.

It should be noted that anionic bitumen emulsion could react well with positively charged materials, but such materials are not often seen naturally.

One of the possible explanations of the advantages of the cationic emulsion is the high kinetic energy of cationic emulsifiers, allowing better adhesion to almost all solid materials.

Bitumen particles pass through a water layer around the filling material and then contact directly the solid surface. Even if the surface is positively charged, the adhesion is good due to the Van der Vaals forces.

There is another theory explaining the interaction of cationic emulsions with alkaline materials. It states that cationic emulsions always contain some free acids. They have low pH and can interact with alkali on the surface of the filling material. The results of the reaction are carbonate ions with negative charge. They neutralize ions of the cationic emulsifier. An insoluble product forms on the boundary between bitumen and mineral, strong enough for adhesion between the components.

Development of special equipment for production of bitumen emulsions (UVB-1) and polymer modified bitumen (UVB-2) by GlobeCore allows the use of these materials not only in road construction, but also in civil engineering.

Bitumen emulsion were first tried as a road construction material in the beginning of the 20th century. Originally, the use of emulsion was limited due to low experience and knowledge in the area of emulsion formation, mixing and the technology of emulsion production and application. With time, the use of emulsion grew steadily from the 1920s to 1950s.

It was in the mid 1950s when the rapid increase of traffic load made the emulsions inadequate for the task. The interest in emulsions fell, however, bitumen emulsion continued to be used for some purposes.

At that period, hot asphalt mix was mostly prepared with bitumen binder. In road construction emulsion were used mostly for ground reinforcement or on secondary roads.

A new hope for the emulsion came in the beginning of the 1970s, when the energy crisis hit Western Europe and the US. Import of oil became a serious problem, especially so for the US.

At this time the manufacturers of road construction materials remembered about bitumen emulsions, which, as before, required no petroleum based solvents or additional heating for the mineral material. The advantages of bitumen emulsion in comparison with thinned bitumen in terms of the ecology were also obvious.

This caused significant extension of the use of the emulsions. Emulsion preparation and application methods saw rapid development, quality requirements became higher, test methods were developed. Emulsion production systems keep improving all the time. One of the latest and most efficient solutions is the UVB-1 type unit made by GlobeCore. Beside other advantages of the emulsion, (economic, environmental and performance), it became possible to use the emulsion almost all year long from spring to autumn in temperature above +5 ºС.

To efficiently used bitumen emulsion and emulsion based materials, it is important to know how the emulsion interacts with materials of a different origin, how it behaves in different conditions and then formulate the composition of the emulsion with the consideration of all factors.

Application of bitumen emulsions increases performance of roads, their durability and offers an efficient and inexpensive road maintenance solution.

Each year more construction materials are used for construction of roads, mostly asphalt concrete based on bitumen binder.

Traditional production process for road top with hot materials has been used in road construction since the middle of the previous century; it takes a lot of energy and is not very environmentally friendly. Therefore the use of anionic bitumen emulsions is considered by the specialists as very promising. It allows to transfer from hot to cold technology of road construction and increase quality and durability of roads.

GlobeCore manufactures the UVB-1 type bitumen emulsion production units. To make the process less expensive, byproducts of the chemical industry can be used as surfactant emulsifiers.

Analysis of the existing technologies of anionic bitumen emulsion production shows that the best method is combined emulsification, which allows production of a finely dispersed product.

The traditional bitumen emulsification method uses prepared soap. In the combined method, half of the fatty acids are mixed in bitumen, and the other half is saponified in water solution. Then both phases are mixed in KLM type disperser for final emulsification of bitumen.

Pit roads, crossings and driveways are by nature very dusty. In the general case, the amount of dust kicked up into the air depends on the surface of the road, its condition, weight and speed of vehicle movement. A large amount of dust in the air causes accelerated engine wear, limits visibility and causes serious lung conditions in affected people.

The problem is made worse by the wind. If wind speed is 3 – 5 meters per second, the amount of dust falling outside the road may be 1/3 or 1/2 of the toral dust amount. In standard units this is 0.15-0.9 kg/m3. The factors listed above cause visibility problems, forcing traffic to move slowly.

The negative consequences can be alleviated by using modern dust control methods and road surfaces.

The existing methods can be roughly divided into three groups. The first group includes mechanical techniques: washing, blowing, vacuuming. Special equipment may be used: graders, brushes etc. The second group includes techniques of mixing the road top material with special binding and adhesive materials. This results in dust-free agglomerates. The third method is to treat the surface with adhesive materials and chemicals.

The most commonly used method is also the least efficient. The road is rinsed with water and dusted with special brushes. However, the source of dust remains. Besides, at the temperatures above 25 ºС and relative humidity below 50% the water evaporates and the dust returns in half an hour.

The International Road Association suggests the following. First, the surface of the road is prepared, then moisturized and profiled. Then bitumen emulsion is applied to the road. The emulsion may be made with GlobeCore’s UVB-1 units with production capacity range from 1 to 8 cubic meters per hour. The UVB-1 allows dust control measures to be taken almost year round, from early spring to late autumn (as long as the temperature is above +5 ºС). After introducing the bitumen emulsion, the ground is compacted.

A certain amount of water may be used to dampen the ground and thin the emulsion. This will allow uniform distribution of the emulsion on the surface and easier mixing with the top layer of the road.

Application of bitumen emulsion for dust control on dirt roads has the following advantages:

• process economy. The amount of bitumen emulsion used is relatively small;
• materials treated with bitumen emulsion are more durable;
• it is possible to work with wet materials.

There are also limitations:

• bitumen emulsion cannot be applied to clay materials or materials oversaturated with water;
• flexibility of the reinforced material is low.

For long term dust prevention, the top layer of the road should be treated to the depth of 5 – 6 cm.

Road top degrades during operation sue to two groups of factors: mechanical and climatic. Mechanical damage is caused by fatigue of the road top due to transportation load, made worse by uneven surface. This happens, for instance, when heavy trucks (30 tons and above) pass along the road in summer in temperatures in excess of 30ºС.

Climatic factors influence the asphalt due to poor quality of the binder (bitumen) and/or due to sharp changes of bitumen properties during production of bitumen-mineral mix.

The former case is mostly cause by inadequacy of bitumen or polymer-modified bitumen properties. For instance, traction on glass can somewhat characterize adhesion properties of bitumen. It can be determined but not regulated: the important thing is to determine bitumen viscosity and the content of paraffin and cohesion of bitumen-polymer material.

Sharp changes in bitumen characteristics during production of road top is caused by oxidation of bitumen in traditional hot process, which increases the rate of its aging.

Aging of bitumen in a road top under the influence of oxygen, elevated temperature, moisture and catalytic minerals occurs in four stages: strengthening of the structure, stabilization, beginning of destructive processes and destruction. An accelerated transition from the first two to the last two due to heating of bitumen during mixing with mineral material occurs due to two key factors.

First, bitumen heating causes local or general overheats. Regardless of mix composition and bitumen quality, the aging processes accelerate sharply above 160 °С.

Second, the rate of aging depends on the way bitumen was heated: in volume or in film covering mineral particles. Film bitumen in asphalt-concrete ages faster  with all other conditions equal. Today, bitumen plants use collection tanks to store ready asphalt mix from one shift to several days at high temperature. The rate of aging of the film layer during storage and transportation at elevated temperature significantly accelerates aging during operation. In such conditions aging is so quick that bitumen increases consistency by the hour. In the result, the mix contains bitumen with lower penetration and viscosity and higher softening point than originally intended. This is one of the most important causes for reduction of road top service duration.

Reduction of influence on asphalt concrete of the above mechanical and climatic factors can be achieved by changing the regulations defining the consist and quality of the material and the binder. Reduction of bitumen aging rate in operation conditions can be achieved by changing of bitumen-mineral mix production technology.

There are two alternative approaches to reduction of bitumen viscosity to the point where it can be efficiently mixed with mineral filling material: using solvents and the use of bitumen emulsions. The former method increase the cost of bitumen products and causes significant damage to the environment by releasing vapors of organic solvents.

The emulsion base technology of bitumen based road top has become wide spread in recent decades. Beside reducing the bitumen’s aging rate, using emulsions has other advantages (less energy consumption, ability to lay the road top on wet surface etc) over the traditional hot technology.

The amount of asphalt mix based on bitumen emulsion increases. In 2006 over 30% of all binding materials in France were emulsified.

It is necessary that the consist and method of emulsion preparation ensure the required viscosity and stability in transportation and storage, with relatively low cost of raw material. The component which influences the above parameters the most is the emulsifier.

The components used for the production of bitumen emulsion and the production process is mainly defined by the process equipment.

Among the currently available plants for production of cationic or anionic emulsions, the UVB-1 plant by GlobeCore is one of the most efficient. By choosing the model of the required production capacity, the client can optimize the process of bitumen emulsion production at the facility with guaranteed production of the required quantity and quality of the product.