GB2578162A

GB2578162A - Apparatus and method for providing concrete mix components

Info

Publication number: GB2578162A
Application number: GB1817077.9A
Authority: GB
Inventors: Hamilton Jardine Mark
Original assignee: Ec Mix Ltd
Current assignee: Ec Mix Ltd
Priority date: 2018-10-19
Filing date: 2018-10-19
Publication date: 2020-04-22
Also published as: GB201817077D0

Abstract

A pre-loaded flexible intermediate bulk container (FIBC) 10, 20 for providing concrete mix components has an open top 22 and lifting loops 24. The contents of container 20 include a quantity of cementitious material 44, possible contained in waterproof bags 40, a quantity of aggregate material 42, and an admixture container 48 having a chemical admixture 50. Admixture 50 may be a plasticiser, accelerating and/or retarding compounds, water reducing compounds, corrosion inhibitors etc. The quantities of materials 42, 44, 48 are selected such that, when substantially the entire contents of the container are mixed, a resulting concrete mix has predetermined properties. Materials 42, 44, 48 within container 20 may be separated by sub-containers, separate bags and/or barriers. Labels (60, Figs 1 & 3) may be included with instruction, property information and pictorial representation. Methods for providing components for a concrete mix for producing a concrete mix are also disclosed.

Description

APPARATUS AND METHOD FOR PROVIDING CONCRETE MIX COMPONENTS

FIELD OF THE INVENTION

The invention relates to apparatus and methods for providing components that can be mixed to form concrete. In particular, but not exclusively, the invention relates to a pre-loaded flexible intermediate bulk container containing cement and aggregate components in a suitable ratio to form a concrete mix with specific properties.

BACKGROUND TO THE INVENTION

Concrete is produced by mixing aggregate with cement and water to form a slurry that can be poured and shaped into a desired form. The concrete hardens by hydration of the cement, forming a solid, stone-like material. Chemical admixtures are often added to the mix to modify various properties of the slurry or the resulting concrete.

To achieve acceptable quality and uniformity in the resulting concrete, and to meet specific criteria in relation to strength, setting time, workability and so on, the ratio of components in the mix must be carefully controlled, and the components must be mixed thoroughly before the concrete is poured. Both of these factors can be challenging to control, particularly in environments such as construction sites.

For small volumes, concrete can be mixed on-site using a portable concrete mixer comprising a rotating drum mounted on a portable chassis. Typically, the aggregate and cement are transferred manually to the drum by shovelling and water is added with a bucket or hosepipe. For larger volumes of concrete, this method is generally too labour-intensive. Furthermore, it can be difficult to control accurately the quantity of each component, leading to substantial variability in the properties of the resulting concrete.

An alternative approach is to deliver pre-mixed concrete, usually referred to as "ready-mix" concrete, to a construction site in a form that is ready to lay using an in- -2 -transit mixer truck. In-transit mixer trucks include a revolving mixing drum having mixing blades mounted on a truck body. Typically, an in-transit mixer truck is first loaded at a concrete plant with dry aggregate and cement, and suitable admixtures, and then a metered quantity of water is added. The components are mixed by rotation of the drum during transit to the construction site, and are then discharged at the site by rotating the drum in the opposite direction. Alternatively, the truck may be loaded with a pre-mixed concrete mixture including water, produced at a wet mix concrete plant, in which case the rotating drum of the mixer truck keeps the mixture agitated during transit.

Although ready-mix concrete delivered by an in-transit mixer can be more consistent than manually-mixed concrete in terms of the ratio of components in the mix, variability can still arise as a result of mixing time and therefore transit time from the concrete plant to the site.

Ready-mix concrete can also be supplied using volumetric concrete mixers. A volumetric concrete mixer is a truck-mounted device that stores the component materials in separate compartments and then mixes volumetrically-measured quantities of the components together after it arrives at the construction site. Whilst volumetric mixers eliminate variability due to transit time, volumetric measurement itself can introduce inconsistencies in the resulting concrete, for example due to settling and compaction of the granular components during transit.

Delivery of ready-mix concrete by either in-transit or volumetric mixer trucks is only possible when access for such trucks to the site is available, which is not always the case. Also, for practical and economic reasons, the concrete must be laid soon after the truck arrives on site, which may not always be convenient and can lead to logistical problems and construction delays.

For large projects where substantial volumes of concrete are required, portable or semi-portable batch plants can be set up at or close to the construction site. These units are able to produce large quantities of concrete with an accurate and -3 -reproducible mix, but are clearly impractical and not economically viable for smaller projects.

Against that background, it would be desirable to provide apparatus and methods that are useful for the preparation of quantities of mixed concrete in a convenient way on-site, and which offer improved accuracy in the mix of components.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a pre-loaded flexible intermediate bulk container with contents comprising a quantity of cementitious material and a quantity of aggregate material. The relative quantities of cementitious material and aggregate material are selected such that, when substantially the entire contents of the container are mixed, a resulting concrete mix having predetermined properties is obtained.

Advantageously, the container can be delivered to a construction site or similar location, and the whole contents can be mixed together using a suitable mixer on-site to form a concrete mix with desired specifications. No further measurement of the aggregate or cementitious materials is required on-site. Instead, the correct quantities of material can be accurately and reliably measured during pre-loading of the container, which can take place where suitable measuring facilities exist.

Because all of the solid components of the concrete mix are provided together in a flexible bulk intermediate container, it is not necessary to store separate quantities of bulk material on-site. Instead, one or more containers can be delivered to the site and stored until the concrete mix is required. Furthermore, by moving the whole container, all of the components can be moved together to any desired location, potentially reducing labour and time.

Preferably the resulting concrete mix is of a predetermined strength class.

The contents may further comprise a quantity of admixture material. The admixture -4 -material may include one or more chemical admixtures such as plasticisers, accelerating and/or retarding compounds, water-reducing compounds, corrosion inhibitors, air-entraining additives, workability enhancers and so on, as may be known in the art. The admixture material may be enclosed in a sub-container, such as a bottle, pouch or packet, to avoid the admixture material mixing with the other components prematurely and/or to avoid evaporation, reaction or degradation of the admixture material.

The cementitious material is preferably separated from the aggregate material by a barrier. This prevents the cementitious material from mixing with the aggregate material, which could otherwise result in premature setting of the cementitious material due to moisture in the aggregate material. Conveniently, the barrier can be removed from the container before transferring the contents of the container to a mixer. In one embodiment, the cementitious material is contained within one or more bags, which may be waterproof. The bag or bags can be slit and removed before transferring the contents of the container to the mixer.

The container may comprise a label attached to the container, which includes an indication of the predetermined properties of the resulting concrete mix. In this way, the properties or specification of the concrete mix that will result from mixing the contents of the bag can be immediately identified and verified by a user on-site. Furthermore, different containers with contents intended to produce concrete mixes with different properties can be readily distinguished from one another.

The label may include instructions for obtaining the resulting concrete mix. For example, the instructions may specify a mixing time and/or other mixing variables that will produce a concrete mix having the required properties. The instructions may specify an amount of water to be added to the contents of the container to produce the desired mix.

The label may include test information for the resulting concrete mix to allow verification that the resulting concrete mix has the predetermined properties. Test -5 -information may comprise details of how to perform a suitable test on the resulting concrete mix and how to determine if the test is passed or failed. For example, the test information may comprise an acceptable range of slump when a standard slump test is performed on the concrete mix. Alternatively or in addition, the test information may relate to a non-standard and/or qualitative test that can readily be performed on-site without special equipment. The test information may include a pictorial representation of a test procedure and/or a test result. The pictorial representation could for example be a photograph of the result of a slump test on a representative concrete mix having the predetermined properties.

The quantity of aggregate material may comprise a first portion of fine aggregate material, such as sand, and a second portion of coarse aggregate material, such as gravel. The ratio of fine to coarse aggregate material is preferably carefully controlled during pre-loading of the bag or preparation of the aggregate material.

More generally, it is preferable if the aggregate material has a controlled particle size distribution.

The contents of the container may further comprise a quantity of water. The water may be distributed in the aggregate material and/or provided separately, for example in a bottle or other container. The water may be combined with the admixture materials. The quantity of water may be provided separately to the container, in a separate barrel, intermediate bulk container or other container. If provided, the quantity of water is preferably selected so that no additional water need be added when preparing the concrete mix.

However, the container of the invention may not include all of the water necessary to prepare the concrete mix, for example to limit the mass and volume of the container. In this case, a suitable amount of water can be added during mixing from a suitable source on-site. The instructions, when present, may provide a guide to how much water is required. It will be appreciated that, unless dried aggregate material is used, it is likely that some water will already be present in the aggregate material, and that the water content may vary depending on conditions during transit -6 -and storage. The instructions may therefore provide guidance on how to ensure that the correct amount of water is added during mixing, for example by checking the consistency of the mix. Photographs or other pictorial representations may be provided in the instructions for this purpose.

The cementitious material preferably comprises cement, such as Portland cement. However, the cementitious material could also include other components such as fly ash or blast furnace slag.

In a second aspect, the invention resides in a method for providing components for a concrete mix having predetermined properties, comprising loading, into a flexible intermediate bulk container, a quantity of cementitious material and a quantity of aggregate material, wherein the relative quantities of cementitious material and aggregate material are selected such that, when substantially the entire contents of the container are mixed, a resulting concrete mix having predetermined properties is obtained.

Loading the quantity of cementitious material preferably comprises placing one or more bags of the cementitious material on top of the aggregate material after loading the aggregate material into the container.

The method may comprise loading a quantity of admixture material into the container.

The method may comprise attaching a label to the container, the label may include an indication of the predetermined properties of the resulting concrete mix.

The method may comprise transporting the loaded container to a work site.

In a third aspect, the invention provides a method of producing a concrete mix having predetermined properties, comprising providing components for the concrete mix by performing the method of the second aspect of the invention, and mixing -7 -together substantially the entire contents of the container to produce the concrete mix.

Preferred and/or optional features of each aspect of the invention may also be used, alone or in appropriate combination, in the other aspects of the invention also.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which like reference numerals are used for like features, and in which: Figure 1 is a perspective view of a flexible intermediate bulk container according to the invention; Figure 2 is a cross-sectional view of the container of Figure 1; and Figure 3 is an enlarged view of an information tag of the container of Figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 shows a pre-loaded container 10 according to an embodiment of the invention. The pre-loaded container 10 comprises a flexible intermediate bulk container (FIBC) 20, quantities of materials 40 contained in the FIBC, and a label 60 attached to the FIBC 20.

The FIBC 20 is of a type generally known in the art, and may also be referred to as a bulk bag, big bag or builder's bag. The FIBC 20 is of flexible fabric construction, and may be made from polyethylene, polypropylene or similar materials. The FIBC 20 is square in plan, has an open top 22, and includes a lifting loop 24 at each top corner.

The materials 40 that are pre-loaded into the FIBC 20 consist of all of the components (except water) required, and in the correct proportions, to form a -8 -concrete mix with predetermined properties.

Referring additionally to Figure 2, the materials 40 include a quantity of aggregate material 42, loaded into the lowermost part of the FIBC, a quantity of cementitious material 44 contained within a plurality of waterproof bags 46, stacked on top of the aggregate material 42, and an admixture container 48 containing chemical admixture material 50.

The aggregate material 42 comprises a suitable mixture of fine and coarse aggregates, such as sand and crushed stone or gravel. Preferably the aggregate material 42 has a specific particle size distribution, which can for example be controlled by sieving during production of the aggregate mixture and/or during loading of the aggregate mixture into the FIBC 20.

The cementitious material 44 preferably comprises Portland cement, but other cementitious materials could be used for specific applications.

The waterproof bags 46 prevent premature hydration of the cementitious material 44, and also provide a barrier to stop the cementitious material 44 mixing with the aggregate material 42 while in the FIBC 20.

The admixture material 50 comprises one or more chemical admixtures. The admixtures may include additives such as plasticisers, accelerating and/or retarding compounds, water-reducing compounds, corrosion inhibitors, air-entraining additives, workability enhancers and so on, as are known in the art. The correct quantity of each admixture component for the resulting mix is filled into the admixture container 48 and sealed before loading the admixture container 48 into the FIBC 20.

The pre-loaded container 10 can be delivered to a construction site and stored until the concrete is needed. Then, shortly before use, the bags 46 are opened by cutting or tearing to release the cementitious material 44 back into the FIBC 20. The empty -9 -bags 46 can then be removed. The admixture container 48 is also opened and the admixture material 50 emptied back into the FIBC 20.

After emptying and removal of the bags 46 and the admixture container 48, the 5 whole contents of the FIBC 20 can then be transferred to a suitable mixer for production of the concrete mix.

When all of the materials 40 contained within the pre-loaded container 10 are mixed together with a suitable quantity of water, the resulting concrete mix has predefined properties, arising from the selection of the materials 40 and the relative quantities of each of the components of the pre-loaded materials 40.

The predefined properties may relate to the performance of the set concrete that results from the mix. For example, the predefined properties may relate to the compressive strength of the set concrete. Most commonly, the compressive strength of set concrete is quantified as the compressive failure strength of a cylinder after setting for 28 days (referred to as the specified characteristic cylinder strength), although several other measurements can be used in addition or as an alternative, including the compressive failure strength of a cube after setting for 28 days.

The predefined properties may relate to other physical characteristics of the set concrete, such as tensile strength, elastic modulus, hardness, toughness and so on. The predefined properties may relate to the setting behaviour of the concrete, such as workability, curing time, curing shrinkage, creep and so on.

The predefined properties may be expressed by way of a standard classification system. Various classification systems are in use throughout the world, and typically allocate a strength class to the concrete mix based on the strength of the resulting concrete. One example, used in the European Standard EN 1992 (Eurocode 2: Design of Concrete Structures), identifies strength classes as "CX", where X is the 28-day cylinder strength of the concrete, expressed in megapascals (MPa). Examples include C12, C16, C20, C25 and so on. Each of the strength classes specifies further properties, such as modulus of elasticity, tensile strength, shrinkage, and others. Strength classes may also refer to the 28-day cube strength of the concrete, usually indicated by a code starting with the letter "M" instead of The relative quantities of cementitious material and aggregate material in the container may for example be selected such that, when substantially the entire contents of the container are mixed, the resulting concrete mix has a strength class of C20 and of medium workability. As an example, the aggregate material 42 may comprise 365 kg of sand and 550 kg of 4/20 mm grade gravel, and the cementitious material 44 may comprise 165 kg of standard cement. With these quantities, the FIBC contains enough material to produce 0.5 cubic metres of concrete mix when combined with 90 kg of water.

Referring again to Figure 1, the label 60 is securely attached to the FIBC 20 by a webbing strap 62 that extends around one of the lifting loops 24. The label 60, shown in more detail in Figure 3, is of robust, waterproof construction and may for example be of a plastic or plastic-laminated paperboard material. In this way, the likelihood of damage to the label 60 during handling of the container 10 is minimised. A slot 64, which may be reinforced, is provided for attachment of the strap 62.

The label 60 includes a first part 66 that indicates the predetermined properties of the resulting concrete mix. In this example, the indication 68 denotes a strength class of C25. The first part 66 may include additional information about the predetermined properties.

A second part 70 of the label 60 provides instructions 72 for how to obtain a concrete mix with the predetermined properties using the contents of the container 10. In the illustrated example, the instructions 72 are in the form of a numbered list of steps.

The instructions 72 may provide various pieces of information to the user, such as one or more of: (a) how to prepare the contents of the container 10 for mixing, for example to empty and remove the bags 46 and the admixture container 48; (b) what type and volume of mixer should be used; (c) that substantially all of the contents of the FIBC 20 should be transferred to the mixer; (d) what quantity of water should be added; and (e) how long the mixing time should be.

Additional or alternative information could also be provided in the instructions 72. The instructions 72 thereby allow a user to be confident of the steps required to obtain a concrete mix having the predetermined properties indicated by the first part 66 of the label 60.

A third part 74 of the label 60 provides test information. The test information provides the user with a guide for performing a simple, on-site test on the concrete mix after mixing, to verify that the concrete mix (and therefore the resulting concrete) is within

the intended specification.

In the illustrated example, the test information is in the form of a pictorial illustration 76 of a concrete mix slump test. As is known in the art, a slump test is a means of assessing the consistency of the mix, in particular to verify that the correct amount of water has been added and that the components have been correctly mixed. The test involves filling a slump cone with the mix and then lifting the cone vertically to remove it from the concrete mix. The concrete mix then slumps and the distance between the top of the mix and the top of the slump cone is measured and compared with a target range.

The illustration 76 includes a first diagram 78 illustrating a filled slump cone, and a second diagram 80 illustrating the shape of the concrete mix after removal of the cone and the acceptable range of slump values (denoted by the sign "x"). In this way, the label 60 provides a convenient reference to allow the user to perform a suitable test to verify that the mix has been correctly prepared.

The pre-loaded container of the invention can have any suitable capacity and dimensions. The FIBC is conveniently of a standard size, such as a "one tonne" FIBC bag, with typical dimensions of 900 x 900 x 900 mm or a "half tonne" FIBC bag, with typical dimensions of 800 x 800 x 800 mm. Because the entire contents of each pre-loaded container are used at the same time, it may be advantageous to make pre-loaded containers available in several different sizes and/or to fill the containers with different total quantities of material so that a container that produces a desired quantity of concrete mix can be selected.

In the illustrated embodiment, it is intended that a suitable quantity of water would be added to the materials after transferring the contents of the container to the mixer.

The instructions on the label preferably provide a guide as to how much water is required. It is however conceivable that an appropriate quantity of water could be pre-loaded into the FIBC. For some applications, is also possible to spray or otherwise soak the mixed concrete in water in situ after it has been laid.

If necessary, more than one admixture container could be provided to prevent premature reactions between different admixture components. It is also possible to mix certain admixture components with the cementitious material and/or the aggregate material before loading those materials into the FIBC. If all of the admixture material can be pre-mixed in this way, the admixture container can be omitted.

When the cementitious material comprises two or more different materials, such as cement and fly ash, each of the bags may contain a mixture of the cementitious materials. Alternatively, the different materials may be provided in separate bags.

The test information provided on the label may be designed to allow verification that the mix has been correctly prepared without the use of special equipment such as a slump cone. For example, the test information may include or comprise one or more photographs of a correctly-prepared mix, in addition to or instead of other test information. When the test information does relate to a slump test (or another test that requires the use of special equipment), a suitable slump cone (or other equipment) could be included in the container, or with a delivery of a plurality of containers.

Further modifications and variations not explicitly described above are also possible 5 without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A pre-loaded flexible intermediate bulk container with contents comprising: a quantity of cementitious material; and a quantity of aggregate material; wherein the relative quantities of cementitious material and aggregate material are selected such that, when substantially the entire contents of the container are mixed, a resulting concrete mix having predetermined properties is obtained.
2. A container according to Claim 1, wherein the resulting concrete mix is of a predetermined strength class.
3. A container according to Claim 1 or Claim 2, wherein the contents further comprise a quantity of admixture material.
A container according to Claim 3, wherein the admixture material is enclosed in a sub-container.
5. A container according to any preceding claim, wherein the cementitious material is separated from the aggregate material by a barrier.
A container according to Claim 5, wherein the cementitious material is contained within one or more bags.
7. A container according to Claim 6, wherein the bags are waterproof.
8. A container according to any preceding claim, comprising a label attached to the container, the label including an indication of the predetermined properties of the resulting concrete mix.
9. A container according to Claim 8, wherein the label includes instructions for 10. 11. 12. 13. 14. 15. 16.obtaining the resulting concrete mix.
A container according to Claim 8 or Claim 9, wherein the label includes test information for the resulting concrete mix to allow verification that the resulting concrete mix has the predetermined properties.
A container according to Claim 10, wherein the test information includes a pictorial representation of a test procedure and/or a test result.
A container according to any preceding claim, wherein the quantity of aggregate material comprises a first portion of fine aggregate material and a second portion of coarse aggregate material.
A container according to any preceding claim, wherein the contents further comprise a quantity of water.
A container according to any preceding claim, wherein the cementitious material comprises cement.
A method for providing components for a concrete mix having predetermined properties, comprising loading, into a flexible intermediate bulk container, a quantity of cementitious material and a quantity of aggregate material, wherein the relative quantities of cementitious material and aggregate material are selected such that, when substantially the entire contents of the container are mixed, a resulting concrete mix having predetermined properties is obtained.
A method according to Claim 15, wherein loading the quantity of cementitious material comprises placing one or more bags of the cementitious material on top of the aggregate material after loading the aggregate material into the container.
17. A method according to Claim 15 or Claim 16, comprising loading a quantity of admixture material into the container.
18. A method according to any of Claims 15 to 17, comprising attaching a label to the container, the label including an indication of the predetermined properties of the resulting concrete mix.
19. A method according to any of Claims 15 to 18, comprising transporting the loaded container to a work site. 10
20. A method for producing a concrete mix having predetermined properties, comprising providing components for the concrete mix by performing the method of any of Claims 15 to 19; and mixing substantially the entire contents of the container to produce the concrete mix.