The invention relates to a buffer system for storing a hot asphalt mixture, an asphalt storage and/or asphalt buffer storage system, and a method for storing a hot asphalt mixture.

Asphalt is typically produced as a hot mixture of mainly mineral granulates, such as sand, stones and filler, and a binding agent of bitumen. The mineral aggregate forms a mineral skeleton which, after curing of the asphalt, provides the load bearing capacity to the asphalt mixture. The interstices between the sand grains and stones in this mineral skeleton are filled up with fillers and binders, often bitumen, so that a coherent whole is formed. Bitumen is a viscous liquid which occurs naturally in crude petroleum, and which is thin-fluid at higher temperatures. The

deformability of the asphalt, for example in a road surface, strongly depends on both the type of bitumen used in the asphalt production, the temperature of the asphalt, and the load to which the asphalt is subjected. In order that, when applying hot asphalt, the processability and the adhesion of the bitumen to the other asphalt components be kept as optimal as possible, in the production of asphalt, the bitumen is mixed as hot bitumen with the mineral granulate, mostly at a mixing temperature of about 160-190°C. At present, also asphalt mixtures having a lower temperature, typically of 105-160°C, can be produced.

Asphalt is produced in asphalt plants, mostly according to strict recipes, tailored to the intended application. Thus, asphalt intended for application in a sublayer for a bituminous pavement for a road surface has its own recipe, which differs from the recipe for asphalt intended for use in an upper layer of a road surface built up with a bituminous pavement. The recipe may further be tailored to the construction class of the road surface to be made. In the asphalt plant, the hot asphalt can be temporarily stored in large storage silos. Asphalt produced in the asphalt plant is mostly loaded into insulated trucks and transported in these trucks to the location where the asphalt is processed. In constructing a road surface or bituminous paving, hot asphalt is applied in a flat firm layer. After compaction, for example by rollers and cooling, the asphalt hardens and the bearing power is gained.

To ensure that the asphalt is dehvered on site while hot, for the transport of the asphalt from the asphalt plant to the site where the asphalt is processed, use is made of trucks with an insulated loading body.

Applying asphalt on the site and manufacturing the road surface is done mostly by means of machines which are supplied with asphalt by the trucks, and which then spread, distribute and at least partially compact the asphalt. In a second operation, rollers take care of compacting and kneading of the asphalt to form a finished asphalt layer, with a compaction typically varying from 95-98%.

If the construction of a full-quality asphalt is intended, it is advisable to avoid a standstill of the machines of more than 10 to 15 minutes. If not, in most cases an unwanted transverse construction joint arises which requires a specific treatment to prevent cracking. This, however, is an additional operation which entails an additional expense and requires time. To prevent the formation of construction joints, it is hence important that the application of asphalt proceeds as a continuous process and that the machines for applying and spreading out the asphalt can be supplied continuously to enable working as continuously as possible.

Ensuring a continuous supply to the asphalt processing machines on a site is regularly compromised due to, inter alia, the increasing amount of traffic coupled to countless traffic jams. A delayed delivery of the asphalt on the site can give rise to unduly long waiting times in the processing on the site. Such delay during transport not only jeopardizes the continuous supply to the asphalt machines, but also entails the risk of settlement of bitumen in the unprocessed asphalt during standstill in the traffic jam. Moreover, there is a risk of the asphalt cooling down to a temperature that is too low to guarantee an optimum and qualitative asphalt processing.

Another problem is associated with the organization of the asphalt production in the asphalt plant where multiple trucks in the morning at the crack of dawn gather around the same time to be supplied with asphalt, which leads to waiting times at the asphalt plant.

A problem arising from this is associated with the driving and rest times the transporters of the asphalt have to observe. Since asphalt is transported by transport firms which often carry out transport for multiple customers, it often happens that a truck has already served other customers before commencing with the asphalt transport for the planned sites.

Because of the regulations governing driving hours, a regularly occurring problem is that a transporter is obliged to take a break, as a result of which the asphalt logistics suddenly halt, asphalt processing halts, with the risk of asphalt quality loss. To attain the planned production, the asphalt team then needs to work costly overtime.

In addition to the logistic pitfalls, also the site organization should be reckoned with: a site is not always an uninterrupted continuous road surface that is a few kilometers long. Also, sites may comprise multiple discrete smaller sections of road surface to be repaired which are at a distance from each other. This distance may vary from a few hundreds of meters to a few tens of meters and consequently requires the asphalt processing machines to be moved from one location to another, which in turn requires the asphalt supply to the machines to be interrupted.

An analysis of the above -outlined problems concerning asphalt transport shows that increasing waiting times, both at the asphalt plant where production takes place and in traffic and on the site, not only entail additional costs but also give rise to a loss of quahty of the asphalt. Once this problem is clear, it is obvious that a solution can be sought in optimizing the asphalt transport or logistics, and this from the place where asphalt production takes place to the place where the asphalt is processed.

Known from GB2329631 is a transport system including an insulated, heatable container in which a conveyor screw is provided for discharging the asphalt from the container. The container is height- displaceable relative to the vehicle to facilitate discharge. At the bottom of the container, slide-out supports are provided to facilitate discharge.

However, GB2329631 does not recognize the necessity of interim storage of hot asphalt in a supply container, to counteract quahty loss and prevent an amount of asphalt that was not used from cooling off and not being suitable for use the day after. This is also true of GB2058178, from which a thermally insulated container is known for transporting bituminous materials. The container can be set up at an angle with respect to the road for facilitating the loading and unloading of the container.

WO2012/049568 describes an apparatus and method for supplying a mixture of a constant quality for carrying out reconstructions. The apparatus includes a torpedo-shaped container having an insulated wall, which can be heated. The container includes two compartments, the first compartment is provided for taking up an aggregate, the second

compartment is provided for taking up a stabilizer. The container contains a plunger for discharging the mixture. WO2012/049568 does not recognize the necessity for interim storage of hot asphalt.

JPH0706373 describes a heat insulated container for transporting an asphalt mixture to an asphalt processor. The container includes an opening at the top for supplying hot asphalt and an opening at the bottom for discharging asphalt. The container further includes handles for hoisting and legs for setting up the container in a raised position.

The problem of long waiting times and transport times of the asphalt is resolved according to the invention with a buffer system which has the technical features of the characterizing clause of the first claim. To this end, the buffer system of this invention for storing a hot asphalt mixture is characterized in that it comprises a container for taking up the hot asphalt mixture, the container including one or more heat insulating walls, which, possibly, can even be heated, which surround an inner space for taking up the hot asphalt mixture, wherein the buffer system includes means to keep the hot asphalt, during storage in the container, in motion; wherein the one or more walls include a closable supply opening for supplying the hot asphalt mixture to the container and a closable outlet for discharging asphalt from the container, while preferably the container is also tiltable between a first position for loading the container with the hot asphalt mixture via the supply opening and a second position for discharging asphalt via the outlet.

The presence of the heat insulating and/or heatable wall ensures that the hot asphalt mixture present in the container remains at a suitable temperature and does not cool off during the storage time in the container. Meanwhile, an internal and/or external mechanism ensures that the hot asphalt mixture is kept in motion. The hot asphalt mixture can therewith be kept moving during the period when no asphalt mixture is dispensed from the container. This provides the advantage that not only setthng of the bitumen and segregation of the asphalt components are counteracted, but also the temperature of the hot asphalt mixture is kept homogeneous and also the quality of the asphalt is thereby maintained.

The one or more heat heatable walls can comprise an inner wall and an outer wall with heating means between them. The heating means may for example comprise a thermal oil which is heated by means of a heating apparatus.

The closable supply opening is preferably heat-insulated, and more preferably includes means for the heating thereof, and simplifies the access to the inner space for loading the container with a new load, for example fresh asphalt mixture. The container thus provides a buffer in which a hot asphalt mixture can be temporarily stored, at a location between the production plant where the asphalt production takes place, and the site where the asphalt is processed. Such additional storage locations contribute towards the shortening of waiting times at the asphalt plant. A geographically strategic setup of the buffer system of this invention can moreover ensure a better accessibility. Due to the possibihty of temporarily storing the hot asphalt mixture in the buffer system of this invention, asphalt collection can be spread in time and optimized. This provides the advantage that also the asphalt production can be spread over a larger portion of the day, and can continue even at night and in the off-peak hours of traffic.

The hot asphalt can be discharged from the container to a truck or any other storage volume or transport means, via the insulated and heatable outlet provided on the container.

The tiltabihty of the container of this invention between a first position for loading the container with asphalt via the supply opening and a second position for discharging asphalt via the outlet facilitates the accessibility of both the supply opening and the outlet.

Known from CN204453417 is a rectangular asphalt box for transporting asphalt, which comprises a frame built up from a number of hollow posts filled with a heat insulating material. Mounted on the frame are a top plate and a bottom plate, and a number of plates which form the sidewalls. Each of these plates in implemented as a double plate, with an outer plate and an inner plate which are set up in spaced-apart relation, with a hollow space between them, for taking up a heat-insulating material. The outer plates may be corrugated, to increase strength and impact resistance. The inner plates may likewise be corrugated. The problem of deformation of the asphalt box due to the presence of residual cold or hot bitumen is resolved by the double, insulated wall limiting it to a minimum. The box is arranged to enable transport, not only with trucks but also with other transport means over land and water.

While the asphalt box described in CN204453417 is heat insulated, there still remains a risk of settlement of bitumen present in the asphalt, upon storage of asphalt in this box, for example during prolonged transport or when stopping nights. The problem of settling bitumen is not recognized by CN204453417.

W02015051710 describes a heatable tank for storing asphalt. At the bottom of the tank is a furnace with a chimney which runs through the tank for heating the contents of the tank. Provided in the wall are conduits for heating liquid to flow through. The presence of a heating makes it possible to keep the costs of storage and recycling of asphalt low and to improve production efficiency. While this tank can keep the asphalt at a defined temperature, a risk of bitumen settlement remains. Moreover, there is a risk that the asphalt, in contact with the hot wall, gives rise to incrustation: combustion and oxidation. Nor does this prior art solve the problem of having the asphalt available at a location that is more in the vicinity of the site where the asphalt will be processed.

In a preferred embodiment of the buffer system of this invention, the closable supply opening for the hot asphalt mixture is in a

circumferential part of the wall, more preferably in a part of the

circumferential wall that is at the top in the first, supply position of the container. This is beneficial to the accessibility of the supply opening and facilitates the supply of the asphalt to the inner space of the container from an external volume, for example asphalt from a truck or asphalt coming from an interim storage container.

In another preferred embodiment of this invention, the closable outlet is in a bottom part of the wall, which is at the bottom of the container in the second position of the container. This is beneficial to the accessibility of the outlet and facilitates the discharge of the hot asphalt mixture from the inner space, to trucks set up under the container, for transporting asphalt from the container to the site where the asphalt is applied. The closable outlet may also be heat insulated. The closable outlet may also be provided with means for the heating thereof.

Preferably, the first position of the container corresponds to a lying position, with the longitudinal axis of the container extending parallel to the lying position, and the second position corresponds to an upright position of the container, with the longitudinal axis extending in height direction of the container.

The shape of the container is not essential to this invention, and may be any shape known to the skilled person, for example substantially cube-shaped, beam-shaped, cylinder-shaped or spherical or any other suitable shape. The shape of the container used in this invention is preferably substantially cylinder-shaped, so that the presence of corners in which bitumen could precipitate and deposit, is limited to a minimum.

The means used for keeping the container and the contents of the container in motion are not critical to this invention and may comprise all means deemed suitable by the skilled person. Suitable examples include inter alia rotatable baffles in the inner space of the container, a stirring device and the like. Preferably, however, the buffer system comprises means for rotating the container about its longitudinal axis. Rotating an asphalt- containing container about its longitudinal axis keeps the contents of the container moving, thereby counteracting incrustation on the surface of the asphalt by solidification, as well as settlement of the bitumen present in the asphalt. The container may then be rotatable through 360° or through a smaller angle. The container may rotate in one single direction, for example in the sense of rotation of the hands of the clock, or in two opposite directions, for example clockwise and counterclockwise. In a further preferred embodiment, the container wall is provided with means for the heating thereof, chiefly with the objective of prolonging the storage duration of the hot asphalt mixture in the container.

In order for the risk of oxidation of the asphalt during storage of the hot asphalt mixture to be limited to a minimum, in the buffer system of this invention, the container in which the asphalt is stored is preferably provided with an inlet for supplying a non-oxidizing gas. The nature of the gas is not critical to this invention and may be chosen by the skilled person from the non-oxidizing gases known to him. The non-oxidizing gas can for example comprise one or more gases from the group of nitrogen, helium, argon, neon, or CO2. The temperature and flow velocity at which the gas is supplied may be suitably chosen by the skilled person taking into account the dimensions of the container and the amount of hot asphalt mixture present. In an alternative embodiment for reducing the risk of oxidation, the container is provided with a vacuum pump for lowering the gas pressure above the asphalt surface in the container, or even to make the container completely vacuous or for removing air from the container. It will be clear that supplying the non-oxidizing gas can also be done additionally to the lowering of the gas pressure above the asphalt surface in the container. A pump may also be used for, once, batchwise or continuously, discharging air and/or gas present in the container above the asphalt surface, for example to render and keep the container completely vacuous.

Oxidation takes place mainly in the hght parts of the bitumen present in the asphalt, especially saturated hydrocarbons and aromatics, which may result in the formation of asphalt stones, with an increase of the viscosity as a consequence.

This invention further relates to an asphalt storage or buffer system which comprises an assembly of a displaceable undercarriage and an apparatus placed on the displaceable undercarriage, for storing asphalt as described hereinabove. The displaceable undercarriage can be a generally known undercarriage such as, for example, one or more undercarriages from the group of a trailer, a ship, a train undercarriage. The displaceability of the buffer system of this invention makes it possible to make hot asphalt mixture available at any desired location, for example a location which is located as closely as possible to the site: such location will be chosen especially in the case of sites which consume a large volume of asphalt, or which are at a location easy to reach in terms of traffic. Such location is particularly useful if also smaller volumes of asphalt are to be made available, if transport from the asphalt plant entails a risk of traffic jams, etc. On the other hand, it may be chosen to set up the displaceable undercarriage with the container at, among other options, a railway or a quay, for keeping a better control of the run times for conveyance of a defined amount of asphalt. This applies especially if the system for asphalt storage or buffering is intended for provisioning multiple different sites.

The use of such asphalt storage or buffer systems increases the number of locations where asphalt can be loaded, and thus contributes to the lowering of the waiting times in the loading of trucks with a new load of asphalt. In fact, practice shows that in the morning at the beginning of the workday, long queues are formed at the asphalt plants by trucks that need to be loaded with freshly produced hot asphalt. The use of such asphalt storage or buffer systems increases the number of locations where asphalt can be loaded, and thus contributes to the lowering of the waiting times in the loading of trucks with a new load of asphalt. In fact, practice shows that in the morning or at the beginning of a production, long queues are formed of trucks that need to be loaded with freshly produced hot asphalt. The use of such an asphalt storage or buffer system simplifies not only a continuous asphalt supply to the sites, but also facilitates compliance with the driving and resting times imposed on the truckers by law. For in practice, for the transport of asphalt, reliance is made on transport companies which do not convey freights only for one particular principal but which often carry out and combine transports for multiple companies. Possibly, these transporters have already used up a portion of their driving and rest times before they present themselves at the asphalt plant. When this is not communicated to the processors of the asphalt, or to dispatching, which is often the case, during processing the supply of asphalt is suddenly interrupted in

consequence of compliance with driving and rest times. Still getting the production processed requires expensive overtime.

The use of such asphalt storage or buffer systems also makes it possible to limit overproduction in the asphalt plants. The amount of asphalt is calculated on the basis of production statistics. Practice shows that always some extra is ordered and called off to prevent deficits at the end of the workday. When production has been stopped, machines have been cleaned and have cooled down, it is unprofitable and ecologically not acceptable to re-start asphalt production for additional production to make up a deficit.

In the asphalt storage or buffer system of this invention, the container in which the asphalt is stored is preferably provided with an inlet for supplying a non-oxidizing gas as described above to the inner space of the container and at least partly or whohy filling the volume above the asphalt with this non-oxidizing gas. Alternatively, or additionally, the container is provided with a vacuum pump for removing air normally speaking present above the asphalt layer, from the container. The skilled person is able to determine what gas pressure is to be optimally maintained to guarantee asphalt having the intended quality.

This invention further relates to a method for storing asphalt, which asphalt can be conventional high-viscous asphalt or low-viscous melted asphalt, wherein use is made of an asphalt storage or buffer system as described above, placed at a location located between a plant where asphalt is produced and a site where the asphalt is used. With this invention, the day or week production of asphalt, i.e., the period in which asphalt is produced, can be prolonged to some extent. The production can be carried out with a greater continuity, production can also take place during the off-peak hours and may even be extended to

consecutive shifts, because asphalt storage is no longer limited by the storage capacity of the plant, and asphalt collection is not exclusively determined by the processing on the sites. This provides the advantage that the asphalt production in an asphalt plant can go on quasi continuously and constantly and is not mainly hmited to the period between the early morning and the early afternoon as is currently the case. The production is better controllable and the amount of asphalt produced can possibly even be doubled. With this system, asphalt remains available more uniformly in sufficient amounts throughout the day. As a consequence, a larger number of hours are available for producing and collecting asphalt, so that not only waiting times before loading of the trucks can be lowered, but traveling time as well. A better spread also entails less stress, in production, in logistics and in processing. A continuous supply of asphalt to the sites furthermore ensures a more agreeable working environment. Moreover, this prevents undue variation in the speed at which the asphalt is processed to form a road surface, which is beneficial to the quahty of the road surface produced.

The invention is further elucidated on the basis of the appended figures and the description below.

Figure 1 shows a view of a preferred embodiment of the buffer system of this invention, with the container in the lying position.

Figure 2 shows a view of a preferred embodiment of the buffer system of this invention, with the container in the upright position.

As shown in Figures 1 and 2, the buffer system of this invention includes a container 10 for taking up hot asphalt 1. The container includes a wall 15, which is heat-insulating and which surrounds an inner space 11 for taking up the asphalt 1. The container 10 shown in Figure 1, for taking up liquid asphalt 1, which can have a higher or lower viscosity, is substantially cyhnder-shaped. The container has a wall 15 with a sidewall 16, a bottom 17 and an upper wall 18. Provided in the sidewall 16 is an opening 20 which can be opened so that asphalt can be passed to the inner space 11 of the container. The opening 20 is closable. The opening 20, or the means closing this opening 20, is preferably heat insulated. The opening 20, or the means closing this opening 20, is preferably also provided with means for the heating thereof. This can be effected in different manners known to the skilled person, for example through one or two adjoining hatches which can be folded open, but any other manner deemed suitable by the skilled person can be used. The hatches which can be folded open are preferably heat insulated, more preferably they are also heatable.

The dimensions of the closable opening 20 are not critical to this invention, but preferably the opening 20 extends over a substantial part of the length l of the sidewall 16 to facilitate the asphalt supply to the inner space 11, taking into account the viscosity of the asphalt and the supply thereof which is often done via trucks.

In the bottom 17 of the container 10, preferably, also a closable opening 13 is provided, along which asphalt can be discharged from the inner space 11, in the upright position of the container. By analogy with opening 20, the closable opening 13 is preferably also heat insulated and more preferably heatable.

The container is tiltable between a lying position as shown in Figure 1, and an upright position as shown in Figure 2. The lying position is provided for facilitating the asphalt supply to the inner space 11. In the lying position, the supply opening is preferably in an upper part of the container 10. In the upright position of Figure 2, the container is positioned such that the outflow opening 13 is at the bottom of the container. The outflow opening 13 is preferably closable in such a manner that it is closed off in the lying position of the container, for temporarily storing asphalt 1; and that is can be opened in the upright position of the container as shown in Figure 2 if loading of a truck or another transport means with asphalt is intended.

The buffer system further includes means for keeping the asphalt 1 in motion, so that the risk of settling of bitumen can be kept at a minimum. To this end, all means deemed suitable by the skilled person can be used. The means for keeping the asphalt in motion are for example arranged so as to subject the container to a back and forth movement, whereby the container, for example, is rotated through 90° or more in a first direction about its longitudinal axis, and then in turn is rotated over a same distance in the opposite direction. It is also possible, however, to rotate the container around its longitudinal axis, or to subject the contents of the container to vibrations or any other technique deemed suitable by the skilled person.

To be able to keep the asphalt in motion optimally, in the inner space of the container or on the inner wall of the container, baffles or blades or fins or similar may be arranged, or a stirring mechanism may be present in the inner space 11.