FI126809B

FI126809B - Method and composition for controlling the water content of the surface layer

Info

Publication number: FI126809B
Application number: FI20145447A
Authority: FI
Inventors: Timo Nissinen; Jorma Pottala
Original assignee: Kemion Oy; Jp Konsultointi
Priority date: 2014-05-16
Filing date: 2014-05-16
Publication date: 2017-05-31
Also published as: FI20145447A; WO2015173478A1

Description

A method and composition for controlling water content of a surface layer

The present invention relates to a composition and method for controlling water content of particulate aggregate surface layers. More particularly, the invention relates to improving water balance of surfaces such as gravel roads or other similar particulate constructions.

Background art

In the northern hemisphere seasonally changing weather causes a variety of challenges for construction materials used. Air humidity and large annual fluctuations in temperature, especially around zero degrees Celsius, have a negative impact on materials, and cause severe economic losses. One of the most typical issues in the northern regions is rain water penetrating into the structures resulting in freeze-thaw cycle and deterioration of structures.

The construction and maintenance of unpaved roads, i.e. earth roads or gravel roads, meet two major challenges: the deterioration of road due to water and the loss of surface cohesion and compaction due to traffic.

Water causes the unpaved road structure a variety of problems. In the beginning of the frost time wet road structures will freeze and cause frost damage, which greatly complicate the use of road in the spring. In cold weather, moisture that penetrates the base layers of roads freezes and rips cracks into the road substrate that seriously undermine the load bearing capacity and longevity of the roadway. Likewise, in milder weather, when water seeps into the base layers of roads the result is softening and erosion that cause potholes that are expensive and recurring problems. When the road structure has dried it starts to dust and fine adhesive particles of road aggregate are disappearing. In autumn, rain water starts again wetting the structure which in turn will freeze later when temperature drops below 0 °C.

The problems typically associated with unpaved roads are surface deterioration and surface deformation. An example of surface deterioration is loss of fine binder particles from road surfaces. This can be seen as dust and the loss of fine particles leads to other types of road distress such as loss of cohesion and compaction of the road fill material and reduced capacity to maintain the requisite moisture in the road structure.

Surface deformations in turn include ruts, corrugations, depressions, and potholes.

Both surface deterioration and deformation are caused by the harmful effects of water and high moisture content resulting in the lack of surface cohesion and loss of road compaction caused by loss of fine particles, dust and the heavy traffic loads exerted on roads.

There is a need for useful low-cost capillary barrier systems for limiting water infiltration and controlling seepage at solid waste landfills. The application in wet regions can be problematic due to loss of water-impermeable properties under high-frequency precipitation. A potential solution is to alter soil grain surfaces to become water repellent by mixing or coating the soil cover material.

Mines, the rest of the industry and power plants have a variety of fields, landfills and heaps where water absorption and subsequent dissolution of various materials cause problems. Dust is also a very typical problem in these areas.

Industry has provided various chemical additives to impart water resistance of unpaved road structures with variety of success and environmental impacts.

Water repellent chemicals are, however, not binders and load bearing capacity, stability, and frost resistance are not improved. In many cases, dust can be also separately reduced by applying chemical additives, “dust suppressors” or “dust control agents”, which draw moisture from air to improve fine aggregate cohesion. So called “soil stabilizers” which are chemicals designed to act as binders and coalesce forming bonds between the soil or aggregate particles, have shown promise in greatly improving the load bearing and traffic capacity of the road.

Existing soil stabilizing solutions and dust control agents are difficult to apply and use in cold climates. They tend to have long curing times, short life-cycles and do not provide the required protection against water damage; particularly excessive moisture content resulting from capillary action. A variety of chemical agents have been developed to balance the water content of aggregate surface and to reduce dust problems. Typically dust binding agents are hygroscopic chloride salts, such as calcium or magnesium salts, and for example forestry by-products from lignosulfocarbonate. One of the most recent developments within hygroscopic materials comprises biodegradable salt of formic acid, such as potassium formate. Furthermore, there is a variety of mineral oil based polymer products, such as acrylic and methacrylic-based polymers. The purpose of these chemicals is to bind the particles of earth material together and thereby reduce fines in the formation of dust. Mineral oil based polymers are often a problem for their environmental impact and high price. Potassium formate in turn is clearly more expensive than traditional chloride salts and its rapid biodegradation and high water solubility prevents extensive use as gravel road dust-binding agent.

Furthermore, commonly used and efficient but highly soluble chloride salts must typically be reapplied approximately 2-3 months after the previous treatment. This will incur additional costs, and the chloride pollution into the environment increases. CN 102660227 A discloses a method for controlling the water content of a particulate aggregate surface layer, such as open mining roads. In the method, a composition comprising 0.1-2 % by weight of a biopolymer is applied onto said surface layer. The composition also comprises CaCI2 or MgCI2 and glycerol. US 201011224 A1 also discloses a method for controlling the water content of a particulate material, such as coal or mine ores, during transport or storage. In the method a composition comprising biopolymer, CaCI2 and glycerol is applied onto said particulate material to create a temporary protective film. CN 102604597 A discloses a method for controlling the water content of a particulate material (coal) during transport. In the method a composition comprising biopolymer and binder is applied to the particulate material. GB 882139 A discloses a method for controlling the water content of a particulate material, such as ore, during storage. In the method a composition comprising biopolymer is applied to the particulate material, resulting in a protective film in the surface layer. CN 103074034 A discloses a composition comprising a biopolymer in an amount of 0.5-2 % by weight, CaCI2 and glycerol. The composition may be used for controlling water content of a particulate material (coal) during transport.

There is a great need for an improved method of maintenance of unpaved roads or other similar constructions to effectively control water balance in particulate aggregate surfaces layers.

Summary of the invention

One object of the present invention is to provide a method for enhancing the control of water balance in particulate aggregate surface layers.

Another object of the present invention is to provide a composition and method for decreasing the amount of damage caused by ambient temperature variations around freezing point of water to particulate aggregate surfaces, such as the road network.

Yet, another object of the present invention is to provide a composition and method for decreasing mechanical damages and the environmental load caused by dusting of particulate aggregate surfaces or surface layers.

The present invention provides a method for treating particulate aggregate surface layers, for example unpaved road surfaces. Moreover, a composition for use in the method is provided, as well.

The use of the method and the composition provided by the present invention will reduce the time, costs and environmental impacts associated with conventional maintenance of for example unpaved roads.

Detailed description of the invention

By a biopolymer is meant polymers which are naturally found in nature. Like polymers biopolymers are chain-like molecules made up of repeating chemical blocks and can be very long in length. The prefix bio means that they are produced by living organisms and thus are biodegradable. Biopolymers contain monomeric units that are covalently bonded to form larger structures.

By particulate aggregate surface layer is meant a surficial layer of a thickness of about 0-0.1 m, preferably about 0.05 m, from the surface towards the bulk.

This layer is typically called wear or abrasion course or layer when the surface is a gravel road, for example.

In the first aspect, the present invention provides a method for controlling the water content of a particulate aggregate surface layer. In this method a composition comprising a biopolymer is applied onto the particulate aggregate surface layer. The biopolymer forms a film and aids in binding the particulates together i.e. increasing the surface cohesion and providing a surface resistant to leaching by water.

The present invention relates to a method for controlling the water content of a particulate aggregate surface layer as defined in claim 1.

Preferably, the solid content of the composition comprising the biopolymer is from 1 to 100 % by weight i.e. it may be applied as particulate material, essentially as a solid composition, or as an aqueous mixture, such as dispersion or solution. More preferably, the solid content of the composition comprising the biopolymer is from 1 to 50 % by weight, the balance being water.

Biopolymers may be classified into three groups, depending on the nature of the repeating unit. They may comprise polynucleotides, which are long polymers composed of nucleotide monomers; polypeptides, which are short polymers comprising amino acid chains; and polysaccharides i.e. sugars, which are polymeric carbohydrate structures comprising long chains of monosaccharide units bound together by glycosidic linkages.

Polysaccharide based polymers can be linear or branched, and they are typically joined together with glycosidic bonds. The exact placement of the linkage can vary, and the orientation of the linking functional groups is also important, resulting in a- and β-glycosidic bonds with the numbering being definitive of the linking carbons' location in the ring. Many saccharide units may further undergo various chemical modification reactions. Preferably, the biopolymer of the present invention comprises a polysaccharide. Polysaccharides are generally occurring plant biopolymers and industrially applicable and commercially readily available. More preferably, the polysaccharide is selected from the group consisting of cellulose derivatives and starch. Cellulose and starch and deriva tives thereof are well-known polymers. They are easily globally available as products of food and forest industry, low cost and easy to modify and use.

Starches are glucose polymers in which glucopyranose units are bonded by alpha-linkages. It is made up of a mixture of amylose and amylopectin. Amyl-ose consists of a linear chain of several hundred glucose molecules and amylopectin is a branched molecule made of several thousand glucose units. Starches are insoluble in water but they can be digested by hydrolysis. Potato, rice, wheat, and maize are major sources of starch.

The starch of the present invention may comprise tapioca starch, wheat starch, oak starch or rice starch. Most preferably, the starch of the present invention is potato starch, such as native waxy potato starch, or corn starch, such as native waxy corn starch. Waxy potato starch and corn starch are readily available and comprise pure amylopectin starch without amylose. High amylopectin content enables a composition with good product stability. Furthermore, waxy starches have less retrogradation resulting in a more stable product.

In one embodiment the biopolymer comprises starch having an amylopectin content of at least 50 % by weight, preferably more than 70 %, more preferably more than 90 %, or even more than 95 %.

In another embodiment the starch is produced from potato or corn waste or byproduct material. This waste material may originate from potato producers, and typically comprises potato peals or the like. Recycled use of this waste product enables to reduce the environmental load caused by additional processing for destroying the undesired by-products by conventional ways.

Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. The structural components of plants are formed primarily from cellulose. Wood is largely cellulose and lignin, while paper and cotton are nearly pure cellulose. It is the most abundant carbohydrate in nature. Humans and many animals lack an enzyme able to break the beta-linkages, so they cannot digest cellulose. Cellulose is insoluble in water but yields glucose in hydrolysis. The hydroxyl groups of cellulose can be partially or fully reacted with various reagents to produce a variety of derivatives with a wide range of useful properties, like cellulose esters and cellulose ethers.

Preferably, the cellulose derivative to be used in the present invention comprises nanocellulose, carboxyl methyl cellulose (CMC), sodium carboxy methyl cellulose (NaCMC), hydroxyl propyl methyl cellulose (HPMC), hydroxyl ethyl cellulose (HEC) or hydroxyl propyl cellulose (HPC). More preferably, the cellulose derivative is NaCMC. These are most common cellulose derivatives, globally available and technically capable of efficiently forming a polymer film. Some of the most developed and tailored versions of cellulose derivatives, like HPC, can form durable and elastic polymer film without the use of any further additives. They are, however, quite expensive which limits their large scale use. Moreover, e.g. HPC is well suited for crosslinking. Solubility of a biopolymer is a practical issue of selection process; depending on the carbon chain length, molecular size and microstructure the resulting product may become highly viscous posing constraints to the application apparatus.

In one embodiment the amount of HPC in the composition comprising the biopolymer is at least 50 % by weight of the dry composition, preferably more than 70 % by weight, and more preferably more than 90 % by weight, such as 98 % by weight.

In another embodiment the composition comprising biopolymer comprises NaCMC and the amount of NaCMC is at least 50 %, preferably more than 70 %, most preferably more than 90 %, such as from 95 to 100 % by weight.

In another embodiment the biopolymer comprises nanocellulose and the amount of nanocellulose of the biopolymer is at least 50 %, preferably more than 70 % most preferably more than 90 %, such as from 95 to 100 % by weight. Nanocellulose is typically very effective even in the small application dosages and a smaller amount will suffice.

In another embodiment the biopolymer is produced from cellulose waste or byproduct material originating from the forest industry, biofuel industry or the pulp and paper production processes.

Preferably, a further composition comprising a hygroscopic metal halide is applied onto the particulate aggregate surface layer, in combination with the composition comprising the biopolymer. The halide is used to maintain the moisture content, to provide better elasticity to the surface layer and to increase cohesion between aggregate materials.

The hygroscopic metal halide of the present invention preferably comprises alkali metal halides or alkaline earth metal halides. Most preferably the metal halide is highly hygroscopic and low cost CaCl2 or MgCl2 or a mixture thereof. The dust binding ability of calcium chloride is particularly high, especially when the relative humidity is high.

In one embodiment the composition comprising a hygroscopic metal halide and the composition comprising a biopolymer are mixed together prior to application onto the particulate aggregate surface layer. In this manner the treatment of the present invention can be made at the same time saving on labour costs and decreasing the amount of traffic disturbance. Especially, if only one treatment round is due, this type of application is a good solution.

In another embodiment the method of the present invention is carried out by first applying the composition comprising a hygroscopic metal halide onto the particulate aggregate surface layer to be treated, and subsequently applying on top of the resulting surface the composition comprising a biopolymer. Using the separate treatments more freedom to formulate biopolymer solutions is provided ensuring higher stability to the biopolymer solution Preferably, the amount of the biopolymer when used in combination with the metal halide is less than 50 % by weight of the dry matter. More preferably the amount is from 0.5 to 30 % by weight, most preferably from 0.5 to 20 %, especially when the mixture is in an aqueous form, such as from 0.5 to 10 %. The final ratio of formulation between the biopolymer and the halide is optimized on the basis of technical requirements such as durability and efficiency, and by environmental and cost reasons. Typically biopolymers are at least an order of magnitude more expensive than the preferred halides, calcium and magnesium chloride.

Moreover, the application of metal halide prior to biopolymer application enables more appropriate environment for the biopolymer film formation resulting in faster film formation and better film properties which in turn decrease highly soluble halides from leaching into the environment.

In one embodiment aqueous solution of halide and biopolymer, preferably calcium chloride and/or magnesium chloride in an amount of from 20 to 40 % by weight, and starch and/or CMC in an amount of from 1 to 20% by weight, is preferably manufactured at the production facility of the halide, which can be found all around the world. Most preferably, CMC or starch can be dissolved in a warm halide solution to produce different ratios of halide and biopolymers. In this case it is possible to use production facilities, utilities, storage tanks and other equipment of the halide production unit, already available at the site. Product is later supplied as prefabricated mixtures to the final destination, and the already existing halide logistics set up can be fully utilized. Liquid mixture is easy to apply with high accuracy on the aggregate surface layers. The final ratio of formulation between the biopolymer and the halide is optimized on the basis of technical requirements such as durability, efficiency and by environmental and cost reasons.

Preferably, the amount of the metal halide, preferably calcium chloride or magnesium chloride, when used together with the composition comprising the biopolymer is less than 99 % by weight, more preferably from 5 to 99 % by weight, most preferably from 30 to 99 % by weight, such as from 50 to 99% by weight, or even 60 to 99% or 70 to 99% by weight of dry matter.

In one embodiment the method of the present invention includes the use of a composition consisting of 1-10 % by weight of biopolymer and 20-40 % of MgCb or CaCh, the balance being water, for controlling the water content of a particulate aggregate surface layer.

In one embodiment the biopolymer and the metal halide are both essentially in solid form. Composition consisting of from 5 to 40 % by weight of biopolymer and from 60 to 95 % of MgCh or CaCh is applied as a solid mixture. The solid application has the advantages that the mixing is easy, better availability of solid spreading systems and easier logistical solutions and better global availability of solid halides. A solid mixture can be made in the facility of halides industrial production process. After mixing the solid mixture can be placed in varying size of packagings or supplied as a bulk. The solid product mixture is then logistically easy to transfer to the final destination by utilising already existing and well-functioning halide logistics setup. Solid mixture is also easy to spread on the aggregate surface by utilising existing spreading systems and equipment. The final ratio of the solid formulation between the biopolymer and the halide is optimized on the basis of technical requirements such as durability, efficiency and by environmental and cost reasons.

The preferred viscosity of the aqueous composition comprising the biopolymer is less than 2000 cP, more preferably from 10 to 1000 cP, most preferably from 50 to 500 cP, to comply with readily available application equipment.

Typically, a degradable plastic is defined by ASTM and ISO as material which undergo a significant change in chemical structure under specific environmental conditions. This degradation results from the action of naturally occurring microorganisms such as bacteria, fungi and algae. In general, biodegradable is taken to mean to be consumed by microorganisms and returned to compounds found in nature. Some microorganisms have a naturally occurring, microbial catabolic diversity to degrade, transform or accumulate a wide range of compounds including hydrocarbons.

In the present invention controlled biodegradability is measured by the ability of the biopolymer to remain intact and perform its desired function. Preferably, the functionality of the slowly biodegradable polymer composition of the present invention remains unchanged for at least 3 months, more preferably at least 4 months, possibly for a year. Once dissolved into ambient a swift degradation of the polymer takes place. Especially, the close presence of the metal halide was found to decrease the degradation rate of the polymer. Once leached from the surface layer and aparted from the halide, the degradation rate of the polymer is increased in the less halidic soil surroundings. Thus, the use of the combined compositions according to the present invention provides a self-controlling effect on the degradation behaviour.

In one embodiment the biopolymer of the present invention comprises a slowly biodegrading biopolymer, maintaining its functionality from 3 to 12 months.

In another embodiment the composition comprising the biopolymer further comprises a binder. Binders enhance the effective adherence of the polymer film to particulate aggregates. The selected binder has a clear effect on the technical characteristics, such as waterproofness, colour, hardness, elasticity, biodegradability and longevity, of the forming film.

Binders can be emulsions and/or dispersions based on the following chemicals: polyvinyl alcohol, styrene-butadiene, vinyl acetate, vinyl versatate, ethylene, acrylic acid, polyacrylate, polyester resins, silicon based binders, and mixtures, and/or monomers, and/or polymers and/or copolymers thereof. Preferably, the binder is polyester resin, vinyl acetate, vinyl versatate, the mixture or polymer, monomer or copolymer thereof.

Optionally, biopolymer and/or binder can be applied as their monomeric compounds for making in situ polymerization.

In one embodiment of the present invention the binder comprises polyester such as polyester resins, vinyl acetate, vinyl versatate or mixtures thereof or copolymers thereof. These can be made from renewable plant-based materials, and were found particularly suitable for use in the present combination of biopolymers and metal halides. The aliphatic biopolyesters can be polyhydrox-yalkanoates (PHAs), like the poly-3-hydroxybutyrate (PHB), polyhydroxy-valerate (PHV) and polyhydroxyhexanoate (PHH). Vinyl acetate based products are commercially available (e.g. Wacker’s Vinnapas, DPX-271 and EP 400). An example of vinyl acetate and versatate copolymer (VAC/VeoVA) is for example redispersible polymer powder (e.g. AP-2080, Shanghai Rongou Chemical Technology). Vinyl acetate, and vinyl acetate and versatate copolymer are globally available, cost-efficient and very capable of making a strong bonds.

In one embodiment the binder comprises a polymer or a copolymer capable of film forming and bonding in situ after water evaporation from the film after application onto the particulate aggregate surface layer.

In another embodiment the binder comprises monomeric compound or compound undergoing polymerisation in situ once applied onto the particulate aggregate surface layer.

This film forming preferably takes place within less than 48 h, more preferably less than 24 h, most preferably less than 12 h. Possibly even in a few hours. Film forming is highly dependent on the rate of water evaporation level, in optimal conditions the film can be formed in a few hours. Crosslinking agents, binders and initiators may have a favourable impact on the rate of film forming and final properties of the film, such as colour, adhesion to an aggregate, hardness, flexibility and waterproofness.

Preferably, the amount of the binder is less than 20 % by weight. More preferably the amount is from 0.1 to 10 % by weight, most preferably from 0.1 to 5 % by weight, such as from 0.1 to 2.5 % by weight. Binder amount is optimised into as low level as possible in order to avoid extra cost and possible environmental load.

In one embodiment the composition comprising a biopolymer further comprises a crosslinking agent. Possible crosslinking agents include aldehydes, such as glyoxal or glutaraldehyde, urea formaldehyde resins, melamine formaldehyde resins, glyoxylated polyacrylamide resins, zirconium based compounds, such as ammonium zirconium carbamate (AZC), polycarboxylic acids, such as citric acid, phosphoric compounds, such as trimetaphosphate or polymetaphosphate, metals in ionic form, such as aluminium or zinc. Preferably, the cross-linking agent of the present invention comprises glyoxal, zirconium-compounds, polycarboxylic compounds and metal based cross-linking agents, most preferably glyoxal or ammonium zirconium carbonate (AZC). Glyoxal and AZC are specifically effective CMC and starch crosslinking agents. By the use of a crosslinking agent the resulting polymer film can be formed faster and at lower temperatures. Furthermore, the weather resistance of the formed film may be improved.

The amount of the crosslinking agent is preferably less than 5 % by weight, more preferably from 0.01 to 2.5 % by weight, most preferably from 0.01 to 1 % by weight, such as from 0.01 to 0.50 %. For cost and environmental reasons amount of crosslinking agent is as low as possible.

Preferably, the composition comprising the biopolymer further contains at least one plasticizer. Plasticizers assist in balancing the forces coming from traffic or other external and internal sources, such as ground freezing. The plasticizer may include carboxylic acid derivatives, glycols, glycerol and polyethers, or-ganophosphates and polymeric plasticizers. Preferably, the plasticizers of the present invention comprise carboxylic acid derivatives like dibutyl sebacate, dioctyl sepacate and dioctyl adibate, and/or glycols like propylene glycol and/or glycerol. Most preferred plasticizer comprises glycerol which is easily available and effective in the low concentrations to give elastic properties for the film.

The composition comprising the biopolymer may yet further contain a water repellent. These agents reduce water (in liquid form) penetration into the polymer film, and therefore increase the water resistance of the film. Preferred hydrophobic agents comprise fatty acids, such as oleic or stearic acids and their derivatives. As an example, vegetable based stearine and stearites may be used. Stearites are advantageously salts of magnesium, calcium, sodium and zinc.

In addition, the composition of the present invention comprising the biopolymer may yet further contain biocides or preservatives, which may be used to improve storage stability of solution and hinder the biodegrability of the formed polymer film. Preferred biocides include biodegradable or food preservation agents like sorbic acid and its salts, citric acid and its derivatives, benzoic acid and its salts, propionic acid and its salts like calcium propionate, sodium nitrite, sulfites such as sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, and traditional industrial biocides like sodium hypochlorite.

Moreover, initiators may be used to initiate the polymer reactions. On the road surface or near the surface layer, it is advantageous to accelerate the polymer film formation and possibly photolysis may be utilised, as well. Preferred initiators include metal iodides, metal alkyls, or azo compounds.

The composition of the present invention may further comprise an emulsifying agent, surfactant and/or a colouring agent. The emulsifying agent can be for example PVA and polyvinyl alcohol, and the surfactant can be for example fatty alcohol sulfate, FAS, polyether, or polyethyleneglycol, PEG.

In one embodiment the amount of biopolymer is from 5 to 20 % by weight and it further comprises PEG from 0.1 to 2.0 % by weight as a surfactant. This enables deeper penetration of aqueous biopolymer solution to the aggregate surface layer.

In the method of the present invention the composition comprising the biopolymer is applied onto the particulate aggregate surface layer, preferably in an amount of from 10 to 500 g/m2, preferably from 10 to 250 g/m2, calculated based on the solid content. The dosage is dependent on the properties of the particulate aggregate surface layer, as well. For long-term applications higher dosages, like 100-500 g/m2 are recommended. For the retreatment or shortterm applications smaller dosages like 10-100 g/m2 can be applied. Weather conditions (rain, moisture content and temperature), aggregate surface properties and traffic conditions also influence in the need of the dosage. The composition may be easily diluted to a desired concentration.

The biopolymer film forms on the surface layer, and to some extent, such as into 0.1 m, or at least 0.05 m into the layer below the surface. The formation of the polymer film takes place within a few days, preferably within 48 hours, more preferably within 24 hours, depending on the ambient conditions, aggregate surface and the quality and quantity of the biopolymer. The formed polymer film prevents the penetration of water from total rainfall into the aggregate structure. Preferably, the biofilm is formed at a time with little or no rain water.

The application methods may include any suitable apparatus typically used for applying solid materials or aqueous solutions onto planar particulate aggregate surfaces.

The particulate aggregate surface layer may comprise any locations suffering from surface deterioration, deformation and dusting. The method of the present invention is particularly useful for unpaved surfaces comprising sand, gravel or other earth materials. Preferably, this composition is applied onto gravel roads, mine landfill areas, industrial areas and by-product fields, dumps, coal fields, coal mines, raw material heaps, port areas and building sites.

The method of the present invention is useful also for football fields, sports fields, parking places, yards, playgrounds, maneges and horse tracks.

In one embodiment the composition comprising a biopolymer from 1 to 20 % by weight and a plasticizer from 0.5 to 2 % by weight is used on gravel roads to prevent road structure from aggressive winter time deterioration and deformation by preventing excessive water from penetrating and thus saving road structure from harmful freeze-thaw cycle and frost heaves or surficial frost heaves.

In another embodiment the composition comprising a biopolymer from 1 to 20 % by weight and a halide from 20 to 40 % by weight, and preferably a plasticizer from 0.5 to 2 % by weight is used on gravel roads to maintain the desired moisture content in the road structure during warm and dry weather conditions and to prevent fine particles to detach from road surface and to form dust.

In another embodiment the composition comprising a biopolymer from 1 to 20 % by weight and preferably a plasticizer from 0.5 to 2 % by weight is used on mine land fill areas or raw material heaps to prevent surface dusting during warm and dry weather conditions.

In another embodiment the composition comprising a biopolymer from 1 to 20 % by weight and preferably a plasticizer from 0.5 to 2 % by weight and a binder from 0.5 to 5 % by weight is used on the dump or landfill area where the hazardous or harmful materials are stored. By forming a water-proof polymer film it is possible to prevent rain water from penetrating inner to the damp or landfills and thus prevent hazardous or harmful material leaching into the environment.

The surfaces treated with the compositions according to the present invention remain moist and nondusting for a long period. The treated surface becomes water repellent and the rain water is removed from the treated surface without being absorbed into the particulate bulk. Especially, the combination of metal halide and the polymer was found particularly resistant and unaffected by ambient condition changes.

The method of the present invention does not include harmful chemicals which would have negative effects on ambient flora or fauna. Moreover, the composition is economical even in large quantities. The method of the present invention enables maintaining the particulate surface and bulk moist for a long period and the film formed by the biopolymer is water resistant decreasing dusting and hygroscopic halide or harmful chemicals leaching into the surroundings. The film formed on the surface binds effectively the aggregates and particles and due to heavy loads the disrupted film provides fewer fines than a surface without the biofilm. Advantageously, the biofilm is flexible enough to withstand well the load and stress due to heavy traffic.

The advantages of the present invention further include savings in the maintenance work, materials and labour cost. In addition the use of the scarce natural resources like gravel and sand can be decreased. Unpaved roads are in better condition enabling fluent traffic and reduced dust formation improves human health and the comfort of living.

In the second aspect, the present invention provides a composition for controlling the water content of a particulate aggregate surface layer. A composition of the present disclosure comprises i. a metal halide comprising CaCh or MgCU preferably in an amount of from 50 to 95 % by weight of the dry matter, and ii. a biopolymer comprising comprises nanocellulose, carboxyl methyl cellulose (CMC), sodium carboxy methyl cellulose (NaCMC), hydroxyl propyl methyl cellulose (HPMC), hydroxyl ethyl cellulose (HEC) or hydroxyl propyl cellulose (HPC), preferably NaCMC, or starch or a mixture thereof, preferably in a total amount of from 1 to 20 % by weight of the dry matter, and iii. a plasticizer comprising glycerol, preferably in an amount of from 0.5 to 5 % by weight of the dry matter, and iv. optionally, a binder comprising polyester resins or vinyl acetate polymer or copolymer, preferably in an amount of from 0.1 to 10 % by weight of the dry matter, and v. optionally, a crosslinking agent comprising glyoxal or AZC, preferably in an amount of from 0.1 to 1.5 % by weight of the dry matter.

The present invention relates to a composition for controlling the water content of a particulate aggregate surface layer as defined in claim 17.

The composition of the present invention may further contain an additive selected from emulsifying agent, initiator, hydrophobic agent, colouring agent and/or biocide. The additives may be used for enhancing solubility and stability of monomers and polymers, to initiate and accelerate polymer film forming in ambient conditions, to increase hydrophobicity and waterproofness of polymer film, to use colour as marking agent for better visibility and separation of layers and for preserving biopolymer solutions from microbial growth and biopolymer film from too fast biodegradation.

The preferred features for the selected compositions are the same as already disclosed in connection with the method.

In one embodiment the composition comprises an aqueous mixture of starch 1-10 % by weight and calcium chloride 20-40 % by weight. This mixture can be produced by utilizing a nearby halide production unit or separately in other location. Liquid mixture is easy to apply with high accuracy on the aggregate surface layers.

In another embodiment composition comprises an aqueous mixture of NaCMC 1-10 % by weight and calcium chloride 20-40 % by weight. This mixture can be produced by utilizing a nearby halide production unit or separately in other location. Liquid mixture is easy to apply with high accuracy on the aggregate surface layers.

In another embodiment composition comprises an aqueous mixture of starch 1-10 % by weight and magnesium chloride 20-40 % by weight. This mixture can be produced by utilizing a nearby halide production unit or separately in other location. Liquid mixture is easy to apply with high accuracy on the aggregate surface layers.

In another embodiment composition comprises an aqueous mixture of NaCMC 1 -10 % by weight and magnesium chloride 20-40 % by weight. This mixture can be produced by utilizing a nearby halide production unit or separately in other location. Liquid mixture is easy to apply with high accuracy on the aggregate surface layers.

In one embodiment composition comprises a solid mixture of starch 5-35 % by weight and calcium chloride 65-95 % by weight. A solid mixture can be made in the facility of halides industrial production process. After mixing the solid mixture product can dosed into different size of packages or supplied further as a bulk. Solid mixture is then logistically easy to transfer to a destination. Solid mixture is also easy to spread on the aggregate surface by utilising existing spreading systems.

In one embodiment composition comprises a solid mixture of NaCMC 5-35 % by weight and calcium chloride 65-95 % by weight. A solid mixture can be made in the facility of halides industrial production process. After mixing the solid mixture product can dosed into different size of packages or supplied further as a bulk. A product mixture is then logistically easy to transfer to a destination. Solid mixture is also easy to spread on the aggregate surface by utilising existing spreading systems

In one embodiment the composition comprises a solid mixture of starch 5-35 % by weight and magnesium chloride 65-95 % by weight. A solid mixture can be made in the facility of halides industrial production process. After mixing the solid mixture product can dosed into different size of packages or supplied further as a bulk. A product mixture is then logistically easy to transfer to a destination. Solid mixture is also easy to spread on the aggregate surface by utilising existing spreading systems

In one embodiment the composition comprises a solid mixture of NaCMC 5-35 % by weight and magnesium chloride 65-95 % by weight. A product mixture can be made in the facility of halides industrial production process. After mixing the solid mixture product can dosed into different size of packages or supplied further as a bulk. A product mixture is then logistically easy to transfer to a destination. Solid mixture is also easy to spread on the aggregate surface by utilising existing spreading systems

In a preferred embodiment the composition of the present invention comprises a biopolymer comprising starch 5 % by weight, a binder comprising vinyl acetate 2 % by weight, a crosslinking agent AZC 0.5 % by weight and plasticiser comprising glycerol 1.5 % by weight and optionally, a hydrophobic agent comprising vegetable stearine/stearate 0.1 % by weight and/or a halide comprising calcium chloride 32 % by weight.

In yet another embodiment, the composition further comprises an emulsifying agent comprising polyvinyl alcohol 0.05 % by weight and a biocide comprising sodium hypochlorite 0.25 % by weight.

The invention is further illustrated by the following non-binding examples. Examples

Example 1 (Water controlling of gravel road) A mixture was prepared consisting of 5 % by weight of potato starch derivative (AVEBE, GF-107), 5 % by weight of a dispersion of vinyl acetate polymer including an emulgator (WACKER, VINNAPAS DPX 271), 1 % by weight AZC crosslinking agent (Brenntag, Zirlink) and the balance water. A 20 g sample of this mixture was poured onto a gravel road sample (10 cm x 10 cm x 5 cm) and the treated sample was dried at 60 °C for 48 hours. The gravel surface of the sample was hardened and water resistance increased significantly compared to untreated samples.

Example 2 (Water controlling of gravel road) A mixture was prepared consisting of 3 % by weight of sodium carboxy methyl cellulose (CP Kelco, Finnfix 5), 2.5 % by weight of dispersion of vinyl acetate and ethylene polymers (WACKER, VINNAPAS EP 400), 1.5 % by weight of glycerol and 0.1 % by weight of vegetable based stearin/stearate (AVEBE, GLISSOFIL EXTRA) and the balance water. A 20 g sample of this mixture was poured onto a gravel road sample (10 cm x 10 cm x 5 cm) and the treated sample was dried at 60 °C for 48 hours. The gravel surface of the sample was hardened and water resistance increased significantly compared to untreated samples. Plasticizing glycerol was observed to modify polymer film more elastic compared to the treated sample of example 1.

Example 3 (Water controlling of gravel road) A mixture was prepared consisting of 3 % by weight of hydroxypropyl cellulose (Ashland, Klucel E), 0.3 % by weight of crosslinking glyoxal (Brenntag, Sequa-rez 755), 32 % by weight of calcium chloride and the balance water. A 20 g sample of this mixture was poured onto a gravel road sample (10 cm x 10 cm x 5 cm) and the treated sample was dried at 60 °C for 48 hours. The gravel surface of the sample was hardened and water resistance increased significantly compared to untreated samples. After drying the hygroscopic calcium chloride was observed to draw new moisture into the sample.

Example 4 (Long term water controlling test)

Four cylinder-shaped sample containers (end point area 80 cm2) were prepared and to each of them was added 10 cm authentic sample of gravel road. Samples of 20 g of water controlling solutions from the examples 1-3 were mixed uniformly to three gravel road cylinders. One cylinder was kept untreated reference sample without solution addition. Subsequently, all samples were allowed to stand at room temperature for 7 days.

Next, all samples were wetted with water simulating summer total rainfall so that a total of 168 grams of water was irrigated into the surface of the samples. Water absorption was monitored immediately after irrigation, and the next inspection was carried out after one week. In the reference sample water was absorbed immediately and with other three samples the surface was still wet a week after the water addition.

Example 5 (Separate calcium chloride and biopolymer treatments)

Four cylinder-shaped sample containers (end point area 80 cm2) were prepared and to each of them was added 10 cm authentic sample of gravel road. Next, 20 g samples of calcium chloride (32 % by weight) solution were poured to all cylinders. A week later samples of biopolymer solutions (listed in the examples 1 -3, but without calcium chloride in the sample 3) were added to three gravel road cylinders. One cylinder remained as a reference sample without biopolymer solution addition. Subsequently, all samples were allowed to stand at room temperature for 7 days.

Next, all samples were wetted with water simulating summer total rainfall i.e. a total of 168 grams of water was poured onto the surface of the samples. Water absorption was monitored immediately after irrigation, and the next inspection was carried out after one week. In the reference sample water was absorbed immediately and with the other three samples the surface was still wet a week after the water addition.

Example 6 (Long term weather durability test)

Samples from the tests described in the example 5 were taken to perform the long term weather durability test for 3 months. A test cycle of wetting (1 week), drying (1 week), freezing (1 week) and wetting (1 week) was applied. After the test the reference sample without biopolymer addition behaved like a sample with no treatment. All the calcium chloride was dissolved by leaching and column surface started to dust immediately when getting in dry conditions. After wetting clear deformation on the surface structure could be seen and freezing test further increased this deformation.

All the biopolymer treated samples showed with good weather durability. Surface of the columns were firm and no dust formation took place, and no significant deformation was observed during the test period.

Claims

A method for controlling the water content of a particulate aggregate surface layer, which is an unpaved surface comprising sand, gravel or other earth materials selected from unpaved roads, gravel roads, harbor areas, construction sites, football pitches, sports grounds, sports grounds, a composition comprising 3 to 50% by weight of a biopolymer and further a crosslinking agent, plasticizer, binder or water repellent, is applied over said surface layer and said composition is capable of forming a film on said surface.

The method of claim 1, further comprising applying to said surface a composition comprising a hygroscopic metal halide.

The method of claim 2, comprising mixing the biopolymer-containing composition with the hygroscopic metal-halide composition prior to application to said surface.

The method of claim 2, comprising the steps of (i) first applying a composition comprising a hygroscopic metal halide to said surface to be treated, and then (ii) applying a composition comprising a biopolymer.

The method of any one of claims 1 to 4, wherein the composition comprising the biopolymer further comprises a binder.

The process according to any one of claims 1 to 5, wherein the biopolymer contains a polysaccharide, preferably a polysaccharide, selected from the group consisting of cellulose derivatives and starches.

The process according to any one of claims 1 to 6, wherein the biopolymer is produced from cellulosic waste.

The process according to any one of claims 1 to 6, wherein the biopolymer is produced from by-product material from the forest industry, the biofuel industry, or from the pulp and paper production processes.

A process according to any one of claims 1 to 6, wherein the biopolymer is starch produced from potato or cereal waste or by-product material, preferably potato waste containing potato peel.

The process of any one of claims 1 to 9, wherein the amount of biopolymer is less than 30% by weight, more preferably 3-20% by weight.

The process according to any one of claims 2 to 10, wherein the metal halide comprises alkali or alkaline earth metal halides, preferably CaCl 2 or MgCl 2, or a mixture thereof.

The process according to any one of claims 2 to 11, wherein the metal halide is present in an amount of less than 99% by weight, preferably 5-99% by weight, more preferably 30-99% by weight, most preferably 50-99% by weight.

The method of claim 5, wherein the binder comprises polyester, vinyl acetate, vinyl versatate, or a mixture thereof, or copolymers thereof.

The method of claim 5, wherein the amount of binder is less than 10% by weight, preferably 0.1-5% by weight, more preferably 0.1-2.5% by weight, most preferably 0.1-1% by weight.

The process of any one of claims 1 to 14, wherein the biopolymer-containing composition further comprises a crosslinking agent.

The method according to any one of the preceding claims, wherein the biopolymer-containing composition is applied to said surface in an amount of 10-500 g / m 2, preferably 10-250 g / m 2, based on the solids content.

17. A composition for controlling the water content of a particulate aggregate surface, which is an uncoated layer containing sand, gravel or other earth materials and selected from unpaved roads, gravel roads, harbor areas, construction sites, football pitches, sports grounds, parking lots, parking lots, comprising i. a metal halide containing CaCl 2 or MgCl 2, preferably in an amount of 50-95% by weight, and ii. a biopolymer containing nanocellulose, carboxylmethylcellulose (CMC), sodium carboxymethylcellulose (NaCMC), hydroxypropyl methylcellulose (HPMC), total hydroxyethylcellulose (HEC) or hydroxypropyl cellulose, and iii. a plasticizer containing glycerol, preferably in an amount of 0.5 to 5% by weight based on the dry matter; and iv. a binder containing polyester resins or a vinyl acetate polymer or copolymer, preferably in an amount of 0.1 to 10% by weight based on dry matter and v. a crosslinking agent containing glyoxal or AZC, preferably in an amount of 0.1 to 1.5% by weight dry matter basis.