I am not sure which is worse.
Bitumen is one of, if not the most widely used compounds in construction having also been used in various forms and applications for many years. Some of the most common uses are as a sprayed seal (hot or ambient) for road surfaces or as a binder in asphaltic concrete. It is also growing in use as a component in foam bitumen stabilisation and even as a dust or erosion control agent.
The critical questions you should ask yourself before using a wet dust suppression system are:
• What is the life cycle of my product?
• Is it safe for the environment?
• Is it safe for animals?
• Is it safe for plants?
• Is it biodegradable?
In this compare series article, we compare the marketplace between bitumen emulsion dust and erosion control systems vs GRT dust and erosion control systems.
The chemical fingerprint of bitumen consist of saturates, aromatics, resins as the maltene fraction and asphaltenes. The rich chemistry that bitumen possesses is what it brings to the bitumen emulsion by product.
Saturates are mainly branched and long with aliphatic chains and traces of heteroatoms and few crystalline n-alkanes. Aromatics have dominant chemical structures slightly aliphatic in nature and a carbon skeleton with lightly condensed aromatic rings. Resins are polar peptizers that act as dispersing agents for asphaltenes and are made up of 2-4 fused rings. Asphaltenes possess condensed polycyclic aromatic rings which are known to be carcinogenic and traces of transition metals nickel, vanadium, and iron in the form of metallo-porphyrins.
Bitumen emulsions are ambient derivatives of bitumen consisting of bitumen dispersed in water or water dispersed in bitumen in the presence of a surface-active agent or surfactant. Phase chemistry of bitumen emulsions is based on the premise of either oil in water or water in oil emulsions with a dispersed and continuous phase. Bitumen emulsions are formulated as low temperature applications of bitumen. The bitumen phase of the bitumen emulsion can also be modified with polymers.
Surfactants concentrate and are active at the surface showing strong tendencies to migrate to the bitumen-water interface and orientate to harness polar-apolar duality. It lowers the surface tension as bitumen is sparingly soluble in water. Anionic, cationic, non-ionic and zwitterionic surfactants are the four different types of surfactants of interest:
Anionic – dissociate in water to an amphiphilic anion and an alkaline metal cation usually sodium and potassium or quaternary ammonium.
Cationic – dissociate in water into an amphiphilic cation and an anion mostly halogen in nature.
Non-ionic – consist of non-dissociable hydrophilic group such as an alcohol, phenol, ether, ester or amide and it does not ionize in aqueous solution.
Zwitterionic or amphoteric – consist of a single surfactant molecule that exhibits both anionic and cationic dissociations.
In a bitumen emulsion, the selection of emulsifier is not always related to stabilisation, but that depends also on the rate of destabilization, associated to final emulsion application. For charged bitumen emulsion, this destabilization rate is evaluated in terms of a breaking test consisting in measuring the quantity of a specific filler needed for droplet breakage to occur which in cases of cationic emulsion the filler Sikaisol is used. This forms the basis of classification as:
• Rapid setting
• Medium setting
• Slow setting
The experimentally controlled breaking value depends on bitumen content, aqueous phase composition, and droplet size distribution, as well as external parameters including environmental conditions, spraying apparatus and breaking agents.
Bitumen emulsion properties depend mainly upon three kinds of variables namely physicochemical formulation, composition and manufacturing protocol. Physicochemical formulation consists of the chemical structure of surfactant and bitumen and temperature. Composition focuses on the relative ratio between phases in the water oil ratio (WOR) and surfactant concentration. Manufacturing protocols include emulsification equipment, agitation and its intensity and the emulsion preparation methodology involved.
Global Road Technology (GRT) is a world leader in innovative and superior dust suppression and erosion control products.
GRT’s dust suppression technology helps overcome the global challenge caused by dust in various industries and sectors such as mining, quarries, civil projects, and more.
When it comes to soil erosion control, and protecting exposed land against the ravages of wind and water, GRT’s advanced polymer technology delivers the complete soil erosion control solution.
GRT offers a dust and erosion product portfolio that is non-hazardous, non-corrosive and safe, non-leaching, non-dissipating, biodegradable and environmentally safe.
Our polymer-based products have been used with good success at many sites – simply by virtue of their formulation flexibility which means there are many variant options that can be tailored to a client’s specific requirements.
Bitumen emulsion binds, seals and suppresses fugitive dust. Not all bitumen emulsions are the same as depicted in the different types of surfactants that are used in the formulation of bitumen emulsions. This also means there are many variables which can affect stability in various water qualities and ease of penetration into the wearing course of a haul road for example.
The unfavourable effects of bitumen on living organisms form the basis of its toxicology. It is even worse with its use as a mix-in product in the wearing course layer of newly established haul and access roads. Product application rates vary from 0.1 to 4.5 litres/m2 depending on road surface condition, dilution and product.
Bitumen has been considered as a possible carcinogen owing to its polycyclic aromatic hydrocarbons. Solubility of bitumen chemical constituents in water because of the presence of the surfactant makes it susceptible to leaching and runoff which affects aquatic flora and fauna.
GRT: Haul-Loc works through binding the fines (which can become airborne dust) both to the ground and to each other. This holds them down, and also makes the particles heavier and drop out of suspension. The product will help maintain the surface of the road, so you should see the requirement for grading reduce and there is no risk of turning the dusty surface into a muddy surface as the moisture content is optimised.
Bitumen emulsion chemistry looks straightforward but there is more to it because the fingerprint from the crude oil and the refining technology increases the potential of carcinogenic hydrocarbons which remain active even when used as bitumen emulsion more so with the presence of water, making it much more dangerous than expected.
Bitumen consists of different hydrocarbons that have a range of aqueous solubilities. The inherent mobility of these compounds present toxicity to surface water and ground water systems.
GRT Soil-Loc is a cost effective, broad-acre wind erosion technology designed to protect cropping lands when they are most vulnerable. High seasonal winds or storm events can remove as much as 50-100mm of valuable topsoil from cropping and agricultural lands. This top layer of soil is also the layer that contains valuable seed, fertilisers and herbicides.
Hydrophilicity of alky-polyaromatic hydrocarbons relative to their unsubstituted counterparts leads to more accumulation in aquatic and terrestrial flora. Factually, solubility of compounds that result in chronic toxicity is reported low but post use and over time continued residence in water affects fish negatively.
Accumulation of polyaromatic cyclic hydrocarbons in fish and aquatic species leads to distortion of the lipid membrane’s structure and function. The 3-5 ringed alkyl polycyclic aromatic hydrocarbons seem to be the most toxic in fish leading to embryotoxicity. In amphibians such as frogs, lower mitochondrial oxygen consumption signals toxicity from polyaromatic hydrocarbons whereas in birds impaired lipid homeostasis is observed.
The extend of bioaccumulation vary depending on volume of bitumen emulsion exposed and the metabolic capacity of biotransformation varies from one species to the next.
GRT dust suppression products are non-hazardous, non-dangerous goods. Our products and systems are designed to improve the safety of workers and protect the environment. Ecotoxicity, Food Safety and WHS testing has been undertaken by GRT and independently verified.
Research shows that toxicity in early-stage development of fish is linked to concentration of 3-5 ringed alkyl polycyclic aromatic hydrocarbons, metals, and naphthenic acids in bitumen. Degradation chemistry of naphthenic acids is rapid given the presence of unsaturation and cyclization and its by-products have a very short half-life in water.
There is a lot of chemistry that is seldom paid attention to. For all we know the chemistry of bitumen is very complex so why risk with facts of the knowns even daring to play with the unknowns. It is dangerous and risky to use bitumen emulsions.
GRT soil erosion control products are non-toxic and environmentally friendly. They can be applied in the most environmentally sensitive areas where very low to nil impacts to environmental values are guaranteed for up to 12 months.
Bitumen in water emulsions are designed to physically bind road materials together and suppress dust on haul roads, LV roads, secondary roadways, hardstands and industrial yard roads. The formulation of bitumen emulsion targets minimizing wheel generated dust on the roads.
Although many benefits have been credited to use of bitumen emulsions, there has been omission of the effects of toxic polyaromatic hydrocarbon precursors over a duration of time. Polyaromatic cyclic hydrocarbons are complicated because they are inevitably found as complex mixtures with other contaminants and photo-transformed products.
Metabolites of polyaromatic hydrocarbons mono-oxygenation are often very highly reactive and more toxic than the parent compound and are related to chemically induced cancers and oxidative stress in vertebrates.
GRT: Haul-Loc is sprayed onto the road surfaces to bind fine dust particles and prevent them from becoming airborne dust. It is a specially formulated liquid polymer that suppresses dust on unsealed haul roads while saving you water and truck utilization expenses. In this Bowen Basin Coal Mine Case Study, GRT Haul-Loc was used to bind surface dust particles and created a sustainable stable layer resistant to heavy traffic wear, wind erosion, and rainfall impact. As GRT is dedicated to developing sustainable, environmentally friendly products, GRT Haul-Loc is safe, non-toxic, has a low carbon footprint and is biodegradable.
Mining tailings can be stored in two ways: dry or wet. When it’s dry, this tailing is stored in the form of stockpiles and can suffer wind erosion or dust generation due to the content of fine materials, especially the fraction of silt. Bitumen emulsions are also used for capping dust on tailing dams.
However, acute toxicity in diluted bitumen is associated with lower molecular weight hydrocarbons, naphthalene, alkyl naphthalene and short-chain alkanes. Chronic toxicity on the hand is related to polycyclic aromatic hydrocarbons and alkyl-polyaromatic hydrocarbons.
The acute and chronic health and environmental impacts are much harder to manage and quantify as the degrees of bioaccumulation vary depending on the volume of bitumen exposed and the metabolic capacity for biotransformation varies from one species to the other.
GRT: Ore-Loc, is a robust liquid polymer applied to stockpiles to create a protective layer to prevent the influence of wind and dust generation. The application is simple and fast being carried out by spraying a mixture of GRT: Ore-Loc and water on the stockpile surface.
For wet tailings dams that are prone to leakage GRT developed the GRT: DamSealer is a complex matrix of soluble and insoluble polymers designed to find and seal leaks from tailings and water storage dams. Through the currents caused by the leaks, the product finds problem areas sealing leaks. GRT: DamSealer is applied on the dam surface at a rate of approximately 100g per square metre.
Erosion of tailing dam walls by rainfall and overland flow leads to scouring and the channelization of water further increasing the effects of water erosion. GRT: Enviro-Binder is a hydraulically applied, highly effect erosion prevention solution, simply sprayed onto to any soil surface. This prevents water erosion damaging embankments, limits the infiltration of water into the structure, and stops the siltation of downstream waterways.
Bitumen emulsion is used for rehabilitation and revegetation efforts, particularly in mine sites. When mixed in with seedlings, it can be sprayed over large areas of land. The bitumen emulsion will help stabilise the soil and prevent erosion. This gives the seedlings time to germinate and helps to return the site back to the state it was before any mining work occurred.
However, in soil and sediments, di- and tri-atomic compounds of lower molecular weight tend to be volatile even when bound therefore their release into water bodies is very easy. On the contrary, higher molecular weight polyaromatic compounds are more tightly bound to soil and sediment for much longer periods.
The hydrophilicity of alkyl-polyaromatic hydrocarbons relative to their unsubstituted counterparts has led to more accumulation in aquatic and terrestrial flora. Accumulation of polyaromatic cyclic hydrocarbons in fish and aquatic species lipid membranes leads to distortion of membrane structure and function. 3 to 5 ringed alkyl polycyclic aromatic hydrocarbons seem to be the most toxic in fish.
Their sources are bitumen especially in diluted form and over a prolonged exposure can lead to embryotoxicity. In amphibians such as frogs, lower mitochondrial oxygen consumption is indicative of toxic polyaromatic hydrocarbons whereas in birds impaired lipid homeostasis is observed.
Coating of aquatic macrophytes impairs photosynthesis by blocking light. Coating of shoots can block gaseous exchange and coated leaves may lead to occlusion of stomata which prevents carbon dioxide uptake as well as release of transpiration water vapor.
GRT Nature Plus is an environmentally friendly product that is immediately effective upon application by binding directly to soil. It accelerates germination reducing impact erosion, sheet erosion, topsoil loss and sediment. Application of GRT Nature Plus minimises wash away of seed and aids fertiliser retention around the root zone.
GRT Enviro Binder keeps the soil in place – where you want it! Offering fast results and proven to outperform in any situation, our non-toxic, environmentally friendly formula has been extensively tested and trialled in multiple environments – bushfire recovery, airport projects, rail projects and civil construction projects.
GRT’s innovative sprayed on polymer erosion control solution works quickly to immediately penetrate the top layer of the soil and form a durable layer, that is bound to underlying material. Unlike other soil erosion control methods, GRT’s product supports seed and vegetation growth, while maintaining its effective erosion and dust suppression properties over the long term.
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