Category Archives: Solutions

Improving Bitumen Properties with Additives

bitumen properties

Bitumen properties. Petroleum bitumen is widely used in construction. It is due to the versatility of this binding material. And it is successfully used in road works, roofing, waterproofing, sealing, for protection of pipelines, canals etc.

But when used in cold weather conditionsб bitumen becomes brittle, which leads to the rapid failure of bitumen coating. This leads to excess expenditure of bituminous materials. Also, bitumen aging is intensified by sunlight and temperature fluctuations.

The solution is the introduction of additives that can improve the performance properties of road bitumen. For example, adding rubber into bitumen reduces brittleness while increasing temperature and heat resistance. The use of polymers for bitumen modification improves the durability of pavement. These conclusions were made by a long-term observation of the road surfaces dressed with modified bitumen. Also, modifications improve bitumen resistance to deformation at low and high temperatures, water resistance, durability and other characteristics.

First, the use of polymer additives to improve the properties of bitumen was explained by chemical bonds between bitumen and polymers. But the infrared analysis showed the absence of new bonds in bitumen-polymer compositions.

The electron microscopic analysis and optical analysis showed the particle distribution of bitumen and polymer. It was noted that a small portion of polymer (1-2%) dissolves in bitumen oils with low molecular weight. Adding 5-10% of polymer increases particle size due to aggregation, 10-15% of polymer produces a cross-linked structure. When the polymer content exceeds 25%, the bitumen enters the polymer cell structure.

In addition to polymer additives, bitumen cracking resistance is improved by adding oil or oligomers, also called plasticizers, which enhance bitumen properties at low temperatures.

Bitumen Roofing Materials

Bitumen Roofing Materials

Bitumen Roofing. Bitumen has been used roofing for many years. Bitumen-impregnated cardboard is the most popular due to its relatively low cost and versatility: this material can be used not only for roofing, but also for waterproofing.

Rolled bituminous materials absorb water quite well and cannot guarantee completely watertight seals. So roofs are made of 3-4 layers of bituminous material.

If the seals are not watertight, water accumulates in the spaces between layers. At subzero temperatures, water expands the already existing microcracks, breaking the roof cover.

The expected time between roof construction and its first repairs is 2-3 years. Repairing the damage is also complicated. This is due to the fact the the location of the water between the layers very seldom coincides with the location of the leak. Every time the number of layers increases, but they gradually break in the cycle of freezing and melting of ice. With time, the costs of repairs exceed the costs of construction and continue growing.

To improve cold resistance and elasticity of a soft roof, special SBS modified bitumen is used. This material is bitumen with a special artificial rubber additive.

A soft roof made with SBS-modified bitumen is stable to high temperatures and UV, and also retains its elasticity at subzero temperature.

GlobeCore has developed and manufactures the UVB-2 type units for bitumen modification. Bitumen produced by this machine fully meets the requirements to roofing and waterproofing operations. UVB-2 units can be used either outdoors under a canopy or indoors in well-ventilated structures.

Modification of Bitumen as a Method to Improve Performance

Modification of Bitumen

Modification of Bitumen. The performance of bitumen in road construction can be improved in two ways. First, to improve the production process. Second, to mix bitumen with special additives. At the production stage, tar oxidation is often improved. IT is difficult to do without the process, but it alone is not sufficient. Improving tar oxidation cannot achieve the results required of the modern bitumen materials.

Bitumen application experience shows that the time when bitumen can be used is defined by the time when bitumen remains plastic, i.e. the difference between softening and brittle points. To increase this interval, it is reasonable to reduce settling point and increase softening temperature of the medium.

This can be achieved by one of the following techniques:

  • mix bitumen with large amount of asphaltene with products containing low molecular aromatic oils with low viscosity and low settling point. Such oils are extracts from selective oil purification, tower bottoms, deasphalting asphalts, etc;
  • oxidize molten bitumen with air. One drawback of the method is that undesired free bonds form in the reaction, which react with ozone and become the centers of binder destruction;
  • oxidation by phosphorus oxide or iron chloride. These substances act as catalysts, forming complexes with polar molecules present in asphaltenes and resins. These complexes are poorly soluble in bitumen and form a colloid structure;
  • Modification of bitumen by special fillers, stabilizers, plasticizers, synthetic polymers etc.

Using fillers improves the strength of road construction bitumen, but reduces plasticity and elasticity of the bitumen compounds. It also increases material viscosity. Antioxidants may be added to bitumen to reduce aging; antipyrene improve fire resistance.

The addition of plasticizers reduces bitumen viscosity and improves its stability in cold weather, stretching and water resistance. At the same time, this additive reduces heat resistance of bitumen. Some of the plasticizers used are transformer, spinning oil, diesel fuel and other oils.

Production of Modified Bitumen

Production of Modified Bitumen

Production of Modified Bitumen. Traffic intensity has grown significantly in recent decades. Each year, the number of motor vehicles grows along with the load on the road top. This results in deformation of the road surface, which require increased number of unscheduled repairs.

The situation can be addressed by improving thermal stability, brittleness and aging parameters of the road top. The solution is to add special materials to bitumen; these materials are known as modifiers. The binder processed in this manner is referred to as modified bitumen.

Natural rubber and rubber crumbs were originally used to improve bitumen elasticity and strength. It was later notices that some polymers, such as styrol butadien styrol (SBS), allows to create a more complex colloid structure of bitumen, improving such parameters as thermal stability, adhesion, elasticity and strength. SBS-modified bitumen retains its form better. It preserves its properties both in storage and in use.

The modifier acts as follows. The polymer in bitumen absorbs the low molecular fractions of the binder, improving the strength of the material and reducing its volatility. When selecting type and quantity of polymer to add, the requirements to the road surface, traffic load and climatic conditions must be considered.

GlobeCore has developed and prodices the UVB-2 unit for modification of bitumen at the rate of 1 m3/hour to 22 m3/hour.

This equipment allows to:

  • operate with all known polymers, waxed and various modifier additives;
  • operate with various forms of modifiers, such as granules, powder etc;
  • modify bitumen with any conceivable process;
  • add extra plasticizer and adhesion bitumens during modification and pumping;
  • add more polymer during pumping;
  • reduce the cost of electrical power with the oil heating system.

Polymer modifiers for bitumen: caoutchouc

Various polymers can be used for bitumen modification, including caoutchouc. The key property of caoutchouc is stretching 2-10 times with application of a stretching force and return to initial state afterwards.

This is due to the structure of caoutchouc. Macromolecules of this substance are coiled, therefore, interaction between them is much weaker than intermolecular bonds. Also, macromolecules are only connected in certain locations.

Due to the large size of caoutchouc macromolecules the material solves in organic solvents poorly. The situation can be improved by:

  • intensive stirring;
  • milling at elevated temperature;
  • thermomechanical destruction of molecules.

Consider the types of caoutchouc which can be used in modification of road bitumens.

Butadiene-styrol caoutchouc includes 21-25% styrol and methyl styrol. These substances have a molecular weight of 150 to 400 thousand and a density of 930 kg/m3. Butadiene-styrol caoutchouc is produced by polymerization of divinyl with styrol.

Butyl caoutchouc is produced by copolymerization of isobutylene with 1-5% isoprene. With 910-920 kg/m3 density, the molecular weight of this caoutchouc is 300-700 thousand. Composition and structure of butyl caoutchouc is similar to those of natural caoutchouc. This substance is resistant to cold and acids, flexible, gas tight and stable to oxidation.

Butyl caoutchouc is widely used in construction industry as a base material for production of sealants, adhesive mastics and modification of bitumen. Caoutchouc comes in the form of liquid, water dispersion and solid elastic product.

Ethylene propylene caoutchouc is a copolymer of ethylene, propylene and diene hydrocarbon. Due to its structure, this material is resistant to weather, water and cold. The same properties are assumed by bitumen-caoutchouc binders.

SBS Based Polymer Modified Bitumen Production Process

Modified bitumen is produced in asphalt-concrete plants by special units.

To produce polymer-bitumen binders of proper quality the following materials are used: viscous road bitumens and block copolymers of SBS type, surfactants and plasticizers (if required).

When choosing equipment and production capacity, technical and economic parameters of production, as well as the required production volume must be considered.

There are currently two approaches to the production of modified bitumen. The first one is called single stage, since all initial components taken in the required amounts are blended in one tank. If plasticizer is required, it is added to bitumen first, then the product is blended to uniformity. Then the polymer batch is added in the form of crumble or powder, with constant mechanical agitation.

If the block copolymer of SBS type does not contain a surfactant, the missing component is added at the last stage of polymer bitumen binder production, and the mix is homogenized.

The double stage method involves preliminary preparation of polymer solution in plasticizer, or bituminous polymer solution in a mix of plasticizer and bitumen. Component concentrations are compliant with the concentrations selected for the polymer bitumen binder. This solution is mixed with dehydrated hot bitumen. At the end of the process, a surfactant is added and the mix is uniformly blended.

Polymer Bitumen Roofing Mastic

The modern roofing material market is quite diverse. Nevertheless bitumen-polymer mastics attract attention among other materials.

Physically, this compound is a liquid, viscous and uniform mass, which after surface application hardening becomes solid coating. Polymer bitumen roofing mastic is mostly used for construction and maintenance of roofs, as well as waterproofing.

Depending on application mode, there are hot and cold mastics. Hot mastics harden relatively fast. When treating well-prepared materials, several minutes are enough for strong and reliable setting.

There are two alternative approaches to the application of mastic. The first method involves heating the mastic to 160-180ºС and only then applying it by a brush or an applicator. The second method involves pouring a preheated mastic on the prepared surface then evening out the coating.

Roofing mastic combines the advantages of bitumen and polymer materials. It prevents the spread of fungus and mold, protects the base surface from moisture and adds strength to the coating. It can be applied in combination with concrete, metal, wood and other materials.

A roofing mastic contains bitumen, modified by polymer additives, and a filler. Before application, the surface must be cleaned from grease, dust and dirt, which may hinder reliable contact. If the base surface is porous, a special primer is applied. After the primer is dry, the mastic is applied on one of the surfaces.

Polymer bitumen mastics have the following advantages:

  • no joins and seals on the roofing surface;
  • high level of adhesion to any material;
  • no blisters caused by moisture evaporation;
  • simple application.

Modifiers and types of roofing bitumens

Either air blown bitumen or modified bitumen can be used for production of bitumen shingles. The question is which material is better.

Modified bitumen is a mix containing various modifiers for performance improvement. In recent years there is an emerging trend: manufacturers of roofing materials prefer modified bitumens to air blown bitumens more often than not. This approach allows to make material with high cold resistance, elasticity and severe load durability. Due to these factors, service life of roofs is extended.

Let us describe in detail the types of bitumen used for shingle production.

SBS-modified bitumen is a mix containing styrol butadiene styrol (artificial rubber). Due to this additive, the resulting product has improved flexibility and durability at subzero temperatures.

SBS- modified bitumen is fairly elastic, returning to its original shape after stretching. Among other advantages of this material there are the precize duplication of the surface shape it is applied to. Styrol butadiene styrol modifiers make bitumen insensitive to extreme temperatures.

Advantages of SBS-modified bitumens are as follows:

  • ability to stretch 20 times its length without breaking;
  • after stretching, only 10% of length is irreversible;
  • flexibility at very low temperatures with no cracking.

The optimum content of SBS in bitumen does not exceed 3-6%. While using this material, storage and the technology of roof construction should be considered.

APP-modified bitumen, according to its physical and chemical properties, belongs to thermoplastics. This material is produced by adding atactic polypropylene to bitumen mix. APP improves high temperature endurance. One of the disadvantages of APP-bitumen is its inability to revert to initial shape after deformation.

APP material is resistant to ultraviolet exposure as well acids and alkalies. Besides, it demonstrates good adhesion to both glass and metal.

APP roofing is applied predominantly in regions with hot climate, but if applied correctly,  it can serve for a long time even in cold areas.

Air blown bitumen is produced by artificial aging of material. It is very popular in the USA. The main advantage of air blown bitumen is its high heat resistance, as well as good stability to wind loads. Properties of this material depend on the properties of the original material and the equipment used for production.

Production of modified bitumen

The quality of modified bitumen depends on the technology used for additive mixing. One of the plants which can do the job well is the GlobeCore UVB-2 unit.

This equipment can:

  • operate with absolutely all currently known polymers, waxes and various specific additives;
  • use various forms of modifiers: powders, granules, etc;
  • implement almost any process of bitumen modification;
  • inject additional amount of polymer in a product transfer mode;
  • reduce your electric bill by using an oil heating system.

Materials for soft roofing

Until recently rolled roofing materials were the most popular. They attracted customers by their relatively low cost. Besides, this roofing material did not have many alternatives. The situation has changed with the appearance of heat hot roofing materials, liquid rubber and roofing bitumen.

Modern roofing materials have a more complicated structure, new types of base and are more elastic and cold-proof. Experts note that the so called “patch repair” of existing roofing can extend roof service life only for so long. Production of bitumen mix used as a base for roofing materials:

  • is based on air blown bitumen;
  • involves application of polymer additives.

The first case is characterized by instability to ultraviolet exposure and fast aging. In particular, we can note the reduced plasticity, excessive stiffness and brittleness. For the above reasons, materials based on air blown bitumen are predominantly used as the lower layer of roof coating. In other cases, protection from solar radiation is required. This can be achieved by application of special roofing sand. Application of air blown bitumen is feasible in places without large temperature variations. In this case it can serve up to 15 years.

Polymerized bitumens are classified according to the kind of polymer used. For roofing purposes the following polymers can be applied:

  • isotactic polypropylene;
  • atactic polypropylene;
  • styrene butadiene styrene.

Isotactic polypropylene (IPP) is a plastomer of high density, high tear strength, cold resistance and good resistance to static loads. The main limitation to mass application of materials based on isotactic polypropylene in the roofing industry is their high cost.

Atactic polypropylene (APP) is also a plastomer produced from IPP. It inherits some properties of its predecessor: extended aging period, cold resistance, reliable adhesion to various surfaces.

Styrol butadiene styrol (SBS) is an elastomer adding increased elasticity and high cold resistance to roofing mixes. Beside these advantages, SBS can replicate the surface texture precisely. A mix produced on the basis of SBS is also known as artificial rubber or bituminous-rubber.

Beside impregnating, hot fusing material consist of a base, which is an equally important component. Most often this function is performed by fiberglass cloth, polyester fiber and fiberglass mats. Hybrid bases from polyester and fiberglass cloth are known to have been used also.

All polymer fibers have an important advantage over cardboard: they do not decay.

Fiberglass mats are made by chaotic placement of glass fibers fixed together by glue or by any other method. It has the lowest cost compared to other bases, due to the use of various byproducts in production. However, with the low cost fiberglass mats have a short lifespan. Compared with fibreglass mats, fiber glass cloth is 3-5 times more durable, although the durability comes at a cost.

Polyester – is the most expensive and convenient base, with increased durability and plasticity. It adsorbs grout compounds and ensures good adherence perfectly.

Roofs based on polymer or latex solutions

Sometimes a rolled roof cannot be constructed. Originally, the alternative was proposed in 1957 in the United States. Solutions of polymers were applied layer by layer, creating a solid coat after settling.

Specifically, a solution of polychloroprene rubber and chlorosulfonated polyethylene with fillers and vulcanizing agents are applied to roof base. In both cases, when the solvent evaporates, cold vulcanization occurs: a 1 to 1.5 mm elastic and non-porous film is created. This technology was applied from 1957 till 1963 in the USA and Canada, but was discontinued due to the toxicity of the organic solvents. Subsequently, liquid polymer compositions based on polyurethane with tar pitch were applied in the USA.

Liquid roofing materials can also be produced from chloroprene and acrylic latexes. Such solutions can be found on the roofs of skyscrapers in Chicago and New-York. In recent years, Japanese and American roofing workers began using acrylic mixes.

In the 1990s, a new latex-based composition, non-toxic and nonflammable, was developed. It protected the treated surface from moisture and retained its properties through many freezing/melting cycles.

For modification of roofing bitumens, special equipment is used, such as GlobeCore UVB-2 plants. They can produce roofing materials based on all currently known polymers in the form of either powder or granules. Plant capacity varies from 4 to 40 m3/hour, there are models for small companies and big construction concerns dealing with roofing and waterproofing.