CA2061541A1 - Concrete and its prestressing process and container manufactured with this concrete - Google Patents
Concrete and its prestressing process and container manufactured with this concreteInfo
- Publication number
- CA2061541A1 CA2061541A1 CA002061541A CA2061541A CA2061541A1 CA 2061541 A1 CA2061541 A1 CA 2061541A1 CA 002061541 A CA002061541 A CA 002061541A CA 2061541 A CA2061541 A CA 2061541A CA 2061541 A1 CA2061541 A1 CA 2061541A1
- Authority
- CA
- Canada
- Prior art keywords
- concrete
- fibres
- shape
- concrete according
- alloy
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000004567 concrete Substances 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims description 10
- 230000008569 process Effects 0.000 title claims description 9
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 239000002901 radioactive waste Substances 0.000 claims abstract description 8
- 229910001092 metal group alloy Inorganic materials 0.000 claims abstract description 3
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 9
- 239000000835 fiber Substances 0.000 claims description 7
- 239000004568 cement Substances 0.000 claims description 6
- 238000007789 sealing Methods 0.000 claims description 6
- 230000009471 action Effects 0.000 claims description 5
- 229910045601 alloy Inorganic materials 0.000 claims description 5
- 239000000956 alloy Substances 0.000 claims description 5
- 239000004576 sand Substances 0.000 claims description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 4
- 239000011230 binding agent Substances 0.000 claims description 4
- 238000003860 storage Methods 0.000 claims description 4
- 239000002699 waste material Substances 0.000 claims description 4
- 241000446313 Lamella Species 0.000 claims description 3
- 229910001369 Brass Inorganic materials 0.000 claims description 2
- 239000004411 aluminium Substances 0.000 claims description 2
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- 239000010951 brass Substances 0.000 claims description 2
- 229910001285 shape-memory alloy Inorganic materials 0.000 claims description 2
- 229920002994 synthetic fiber Polymers 0.000 claims description 2
- 229910000990 Ni alloy Inorganic materials 0.000 claims 1
- 229910001069 Ti alloy Inorganic materials 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 5
- 239000011513 prestressed concrete Substances 0.000 abstract description 4
- 239000012530 fluid Substances 0.000 abstract description 2
- 239000000047 product Substances 0.000 description 18
- 239000000463 material Substances 0.000 description 8
- 230000002093 peripheral effect Effects 0.000 description 4
- 230000006870 function Effects 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 230000002787 reinforcement Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 206010037660 Pyrexia Diseases 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000002019 doping agent Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 239000011872 intimate mixture Substances 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 241000965754 Chenopodium acuminatum subsp. virgatum Species 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000006399 behavior Effects 0.000 description 1
- 231100000481 chemical toxicant Toxicity 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000011210 fiber-reinforced concrete Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910001000 nickel titanium Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 229910052716 thallium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000003440 toxic substance Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
- E04G21/12—Mounting of reinforcing inserts; Prestressing
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
- E04C5/012—Discrete reinforcing elements, e.g. fibres
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/07—Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal
- E04C5/073—Discrete reinforcing elements, e.g. fibres
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/08—Members specially adapted to be used in prestressed constructions
Landscapes
- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Mechanical Engineering (AREA)
- Processing Of Solid Wastes (AREA)
- Manufacturing Of Tubular Articles Or Embedded Moulded Articles (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
DESCRIPTIVE ABSTRACT
The concrete according to the invention has durability and mechanical strength characteristics equivalent to prestressed concretes.
It comprises fibres (20) embedded in a conventional concrete, said fibres either being shape memory metal alloy fibres, or thenmoretract-able fibres. A subsequent heat treatment makes it possible for these fibres to assume a shape making it possible to impose compressive stresses throughout the volume of the cast or fluid concrete.
Application to the manufacture of radioactive waste containers.
(single drawing)
The concrete according to the invention has durability and mechanical strength characteristics equivalent to prestressed concretes.
It comprises fibres (20) embedded in a conventional concrete, said fibres either being shape memory metal alloy fibres, or thenmoretract-able fibres. A subsequent heat treatment makes it possible for these fibres to assume a shape making it possible to impose compressive stresses throughout the volume of the cast or fluid concrete.
Application to the manufacture of radioactive waste containers.
(single drawing)
Description
coNcKErE AND ITS PRESTRESSING PROCESS AND CONTADNER
MANUF~CTUK~ WrrH THIS CONCRETE
DESCRIPTION
_ ELD OF THE INVENTION
In general te~ms the invention relates to high performance ccncretes, i.e. having to withstand high mechanical stresses, such as in the case of prestressed concretes. It more particularly relates to high dura-bility concretes more particularly suitable for producing drums or enclosures having to contain solid or liquid, dangerous industrial waste and in particular highly toxic chemical or radioactive waste.
It also applies to any civil engineering structure.
PRIOR ART
Conventional concretes are generally constituted by a mixture of cement, natural or artificial mineral aggregates such as gravel, sand, possible additives and a hydraulic binder such as water.
The conventional proces~ for the production of a cast concrete prcduct is as foll~s:
1. The mixing takes place with the aid of a mixer in order to obtain an intimate mixture of the different components.
MANUF~CTUK~ WrrH THIS CONCRETE
DESCRIPTION
_ ELD OF THE INVENTION
In general te~ms the invention relates to high performance ccncretes, i.e. having to withstand high mechanical stresses, such as in the case of prestressed concretes. It more particularly relates to high dura-bility concretes more particularly suitable for producing drums or enclosures having to contain solid or liquid, dangerous industrial waste and in particular highly toxic chemical or radioactive waste.
It also applies to any civil engineering structure.
PRIOR ART
Conventional concretes are generally constituted by a mixture of cement, natural or artificial mineral aggregates such as gravel, sand, possible additives and a hydraulic binder such as water.
The conventional proces~ for the production of a cast concrete prcduct is as foll~s:
1. The mixing takes place with the aid of a mixer in order to obtain an intimate mixture of the different components.
2. The thus obtained concrete is transferred into the form, whose shape corresponds to the product to be obtained.
3. The concrete is po~Led into the form, possibly accompanied by a vibrating action during filling.
4. The moulded product is demculded by removing the fonm.
5. The concrete is hardened during a ~cure~, which can last f~cm one day to one month, as a function of the type of concrete used and the product produced.
2~
The quality of the product produced with this concrete is significantly dependent on the concrete curing conditions. Thus, microcracks can e~ppear and deteriorate the final mechanical prcperties of the product.
1'hese microcracks then lead to the start of a decay phenomenon with respect to the structure of the product and which can advance with the appearance of macrocracks carried along by the mechanical stresses reaching the strength limits of the concrete.
It is known to reinforce concretes by the introduction of fibres into the mixture in order to improve the mechanical strength and signifi-cantly reduce the appearance of microcracks prior to the appearance ofvisible cracks. However, it d oe s not make it possible to delay the appearance of macrocracks in the structure of the product, when ccm-pression or tension is applied to the latter.
As is described in French patent d~lication, published under No. 2 640 410, such a concrete is used for manufacturing radioactive waste stor-age containers. The container comprises a drum having an opening for the introduction of the waste and a tight sealing cover. The container is entirely melde from cancrete reinforced by metal fibres.
It is cansidered necessary to imprcve the performance characteristics of such cancretes in order to manufacture containers, whose strength and durability characteristics are better than in the prior art. It has therefore been proposed to supply a prestressed concrete, which can have superior mechanical characteristics to the presently produced prestressed cancretes. The main process for prestressing a concrete block at present consists of embedding in the block one or more sheaths within which are located metal cables, which are tensioned once the hardening of the cancrete has been obtained, so as to compressively prestress the concrete block.
The object of the invention is to supply a concrete which can meet the existing require~ents with respect to the production of radioactive waste containers, whilst avoiding the use of the concrete prestressing type described in the preceding paragraph.
2 ~
SUMMARY OF THE INVENTION
To this end, a first object of the invention is a process for prestres-sing a cancrete produced fram a given mixture consisting of intr~ducing in a randcm manner into the mixture fibres, whose shapes or sizes can evolve in time under the action of an energy transfer, pouring the S concrete into a fonm, de~oulding the cast concrete, hardening the con-crete during a curing period and then carrying out a heat treatment in such a way that the dimensions or shape of the fibres evolve, so as to impose mechanical campressive stresses within the concrete.
Thus, at all points of the concrete product obtained it is possible to impose a cpressive stress, which can have the same effects as the campressive stresses imposed by the metal cables under tension used conventionally in prestressed concrete blocks.
A second main object of the invention is cansequently a fibre-containing concrete canstituted by an agglamerate of sand, gravel and ce~ent cambined by means of a hydraulic binder and artificial fibres e~bedded in the agglcmerate at various, randcm positions.
According to the inventian, the fibres used are of the type whose shapes or dimensions can evolve in time under ~le actian of an energy transfer in order to create a compressive stress in the cancrete.
It is possible to use two fibre types, namely shape memory metal alloy fibres and thermoretractable fibres.
m e preferred shape of the said fibres is a very flat lamella, whose length is between 1 and 10 centimetres.
The third main object of t'ne invention is a radioactive waste storage container incorporating a drum provided with a waste introduction cpening and a cover for the tight sealing of said cpening. According to the inventian, the container is entirely made from cancrete of the type described in the preceding paragraphs.
DETAILED DESCRIPTION OF A PREFERRED EME~ODIMENT
The invention and its technical characteristics will be better under-stood frcm reading the following description, illustrated by the single S drawing showing a container according to the invention.
In order to prcduce the ooncrete according to the invention, use is made of the base materials necessary for the prGduction of a conven-tional concrete. These materials are Gonstituted by mineral aggregates, i.e. natural or artificial gravel, sand and cement. To this mixture of solid products in powder fa~m are added loose fibres, i.e. said fibres can assume any randam position. Once this mixture has been made, the hydraulic binder, preferably oonstituted by water, is added. This is followed by mixing in a machine, so as to obtain an intimate mixture of the different components.
The second phase of the process aocording to the invention obviously Gonsists of pouring the fresh ooncrete into the foIm, whose internal shape Gorresponds to the external shape of the praduct to be obtained.
In order to facilitate this operation, the form or mould is generally plaoed an an operating vibrating table. The vibratians make it pos-sible to obtain a very oompact concrete and give a product having avery low porosity. A good surfa oe appearance and a high mechanical strength can also be obtained by using the said vibrating table.
Internal vibrating means can be used far large parts. It should be noted that the po~ition of the fibres is of a randam nature.
Certain products require the use of an internal reinforcement, such as a metal reinforcement, with a view to reinforcing the mechanical prop-erties of the product obtained. The reinforcement is then intraduced into the mould prior to the pouring of the concrete.
Following a first drying period, the concrete is demoul~ed, i.e. the fram is dismantled and removed fram the fluid or cast cancrete. This is followed by a drying phase with respect to the product obtained for the purpose of hardening the concrete. This phase is a cure, which can last fram one day to one month. The duration of the cure varies as a function of the cement type used and the type of praduce manufac-tured. During this cancrete cure, there is a cement hydratian reaction, which is known as concrete setting.
According to the invention, this is followed by a heat treatment per-mitting an energy transfer by varying the temperature of the fibres so that their shapes or sizes evolve. Thus, under the action of a slight temperature rise or fall, such a fibre type assumes a retracted shape or reassumes an initial shape.
A first category of fibres used for this purpose is constituted by so-called shape memory metal fibres. Thus, when a metal or an ordinary alloy is subject to a mechanical stress in excess of its yield point, it underg oe s a plastic defonmation which persist~ after the stress has been discontinued. Its shape and size are then v1rtually subject to no further evolution if the alloy or metal undergoes subsequently a heat treatment of any type. However, shape memory alloys do not have this behaviour, because within a certain temperature range, a sa~ple of such a material can undergo an apparently plastic deformation of several percent and integrally reassume its initial shape by simply heating at a later time. This shape memory phenamen~n is associated with a reversible structural transformation of the ~martensitic thermo-elastic~ type occurring between a first temperature Tl, at which the sample was fonTed, and a second temperature T2 higher or lower than Tl, to which the sa~ple must be heated or cooled fa,r it to reassume its shape.
In the process according to the invention use is made of fibres whose initial shape was that which it was wished to give them to enable the concrete to be compressed, i.e. prestressed. This shape is preferably a retracte~, curved, more or less curled up sh~pe compared with an intermedLate shape, which will tend to be linear or completely straight.
?
hmong the materials used, reference can be made to alloys of the NiTi type (nickel, titanium and dopants) and the CuZnAl type (brass, aluminium and dopants). For such alloy types, the temperature varia-tion can be a rise between 50 and 70C, i.e. for a concrete prcduct at 20C, a heat treatment at a temperature between 70 and 90C can make it possible to return to the initial shape of the metal fibres cast in the concrete. The same result can be obtained by cooling to a temper-ature between -10 and -30C.
The duration of the application of the heat treatment is a function of the shape of the product produced with the concrete. In general tenms the entire product, i.e. even the product core, must reach the phase transfonnation temperature.
If the product produced is transportable, the heat treatment can be applied in the oven. However, if the product is moulded in situ, i.e.
is not transportable as a result of its weight and dimensions, the heat treatment application process can take place by means of high fre-quencies or microwaves using heating sheaths or jackets.
Tension tests by bending at three points were carried out on 4 x 4 x 16 om testpieces. The concrete used had the following constitution:
oenent CLC 45 890 g Bayeux sand 2660 g water 450 g fluidifier 8 g The incorporation of the shape memory fibres takes place after mixing the four components. The heat treatment takes place for 24 hours at 80% in a tight pack to avoid dIying out and then for 24 hours at ambient temperature fo,r cooling prior to the mechanical tests. The tests were carried out in the aOGEMA, m e Hague, concrete laboratory in a 1.5 litre mixer.
The following table summarizes the values obtained:
AGE 14 days 28 days FIBRES (kg/m ) O 50 90 0 50 105 No heat treatment 6.17 6.89 7.65 6.987.68 7.21 With heat treatment 7.37 7.89 7.43 7.758.00 7.84 For fibre-free testpieces, the heat treatment impr~ves the bending strength of the cancrete or mortar (improvement of the cement setting process) by approximately 1 MPa.
For fibre-oontaining testpieces, the tests performed with fibre con-cretes with 50 and 100 kg of fibres per m3 of f m ished concrete shcws that the results are more conclusive (excluding experimental err~rs) with the fibres than without them and with the heat treatment than without it.
A second category of fibre used consists of thermoretractable fibres.
Such a fibre is subject to a reduction in size with a slight temper-ature rise or fall. If the shape is not rect;linear and preferably well curved, the thermoretractable fibres, an retracting, impart a compressive stress to the concrete in which they are embedded. The shape of the fibres used is preferably that of flat lamellas, whose length can be between 1 and 10 centimetres. The thickness can be less than one tenth of a millimetre.
Any randam product can be prcduct with the aid of such a concrete.
However, a special application of the invention is the prcduction of radioactive waste storage containers. Thus, with reference to the single drawing, the container according to the invention essentially comprises a drum 10,, whose upper cpening is sealed by a cover 12.
The sealing is tight in order to make it possible to store low or medium activity radioactive waste coated with a filling material. In the example shown in the drawing, the container is parallelepipedic, ~5~
has a flat bottom and a side wall with a square section. The upper end of the latter defines the opening permitting the closure with the aid of the co~er 12.
According to the invention, the complete container, i.e. the drum 10 and the cover 12 is made fram a concrete reinforced by fibres 20 either of the shape memory, or of the thermoretractable type.
me drum 10, like the cover 12, is produced by moulding. In particular, the upper end of the side wall of the drum 10 has a stepped shape successively defining, passing from the outside to the inside of the drum 10, a planar end faoe 13 and a planar support or bearing face 7 parallel to the first planar fa oe 13, but set back with respect thereto.
me bearing face 7 is connected to the upper surface 13 by an inclined, intem al, peripheral edge 6 forming a Z in cross-section with its two first surfa oes 7 and 13. me diameter of the inclined edge 6 increases on approaching the bearing surfaoe 7, 80 that said inclined edge 6 forms an angle of at least 10- with the axis of the drum 10.
The cover 12 also has a peripheral stepped zone with, starting fram its upper surface, an inclined, outer, peripheral edge 11 and a vert-ical edge 15 set back from the inclined edge 11. These edges 11 and 15 are connected by a second planar bearing face 5 parallel to the upper and lower faces of the cover 12. The diameter of the inclined edge 11 increases on appr~aching the second bearing surface 5, so that said inclined edge 6 fo,rms an angle of at least 10- with the axis of the cover 12.
When the co~er 12 is placed an the drum 10, the lower part of the oover12 defined by the edge 15 is fitted into the opening fonmed at the top of the drum 10, until the horizontal bearing surface 5 of the cover 12 bears on the horizantal bearing surface 7 of the drum 10. As can be seen in the drawing, the inclined edges 6 and 11, which have the same height, then face ane another and define between them a do~etail-shaped annular space 14, whose width is substantially canstant from the upper ~fi~ ~L,~
face 13 of the ccntainer 10 to the bearing surface 7. This annular space 14 constitutes a keying slot.
In order to tightly flx the said cover 12 to the drum 10, into the aforementioned annular space 14 is cast a keying joint produced frcm the same material as the remainder of the container, i.e. concrete reinforced by shape memory or thenmoretractable fibres 20.
This fo~mation of the keying joint in the upwardly c~en annular space 14 ensures the tight sealing of the container without it being neces-sary to use a fonm. Moreover, the shape of the key mg joint avoids any risk of the cover flying off when the joint is prcduced.
Advantageously, the cover 12 is centrally provided with a large opening 8 in which is formed a keying slot 9. Therefore the container 10 can be filled follcwing the sealing of its cover 12. When the waste has been intrcduced by the c~ening 8, the filling material is introduced until the opening 8 is completely sealed. When the f~lling material i8 constituted by thermoretractable or shape memory fibre-reinforced concrete identical to that forming the actual container, a hamogeneous assembly is formed, where the risks of cracks and breaks are eliminated.
Finally, to permit the handling of the container, various means can be provided. In exemplified manner reference can be made to rods or rings 4 sealed anto the upper, planar end face 13 of the drum 10. A handling groove or slot 3 can be fonmed by moulding on the outer peripheral sur-face of the drum lO in the vicinity of said upper end face 13.
This descriptian of a container only represents an exemplified embcdi-ment of objects which can be manufactured with the aid of the concrete according to the invention. Thus, it is possible to prestress any randam object made in general terms from an ordinary cancrete by simply introducing such fibres into the mixture prior to the praduction of the concrete. A heat treatment subsequently applied after the object has been dried makes it possible to obtain within the concrete ccmpressive stresses equivalent to the prestresses imposed by canventional methods used far prestressed cancrete.
2~
The quality of the product produced with this concrete is significantly dependent on the concrete curing conditions. Thus, microcracks can e~ppear and deteriorate the final mechanical prcperties of the product.
1'hese microcracks then lead to the start of a decay phenomenon with respect to the structure of the product and which can advance with the appearance of macrocracks carried along by the mechanical stresses reaching the strength limits of the concrete.
It is known to reinforce concretes by the introduction of fibres into the mixture in order to improve the mechanical strength and signifi-cantly reduce the appearance of microcracks prior to the appearance ofvisible cracks. However, it d oe s not make it possible to delay the appearance of macrocracks in the structure of the product, when ccm-pression or tension is applied to the latter.
As is described in French patent d~lication, published under No. 2 640 410, such a concrete is used for manufacturing radioactive waste stor-age containers. The container comprises a drum having an opening for the introduction of the waste and a tight sealing cover. The container is entirely melde from cancrete reinforced by metal fibres.
It is cansidered necessary to imprcve the performance characteristics of such cancretes in order to manufacture containers, whose strength and durability characteristics are better than in the prior art. It has therefore been proposed to supply a prestressed concrete, which can have superior mechanical characteristics to the presently produced prestressed cancretes. The main process for prestressing a concrete block at present consists of embedding in the block one or more sheaths within which are located metal cables, which are tensioned once the hardening of the cancrete has been obtained, so as to compressively prestress the concrete block.
The object of the invention is to supply a concrete which can meet the existing require~ents with respect to the production of radioactive waste containers, whilst avoiding the use of the concrete prestressing type described in the preceding paragraph.
2 ~
SUMMARY OF THE INVENTION
To this end, a first object of the invention is a process for prestres-sing a cancrete produced fram a given mixture consisting of intr~ducing in a randcm manner into the mixture fibres, whose shapes or sizes can evolve in time under the action of an energy transfer, pouring the S concrete into a fonm, de~oulding the cast concrete, hardening the con-crete during a curing period and then carrying out a heat treatment in such a way that the dimensions or shape of the fibres evolve, so as to impose mechanical campressive stresses within the concrete.
Thus, at all points of the concrete product obtained it is possible to impose a cpressive stress, which can have the same effects as the campressive stresses imposed by the metal cables under tension used conventionally in prestressed concrete blocks.
A second main object of the invention is cansequently a fibre-containing concrete canstituted by an agglamerate of sand, gravel and ce~ent cambined by means of a hydraulic binder and artificial fibres e~bedded in the agglcmerate at various, randcm positions.
According to the inventian, the fibres used are of the type whose shapes or dimensions can evolve in time under ~le actian of an energy transfer in order to create a compressive stress in the cancrete.
It is possible to use two fibre types, namely shape memory metal alloy fibres and thermoretractable fibres.
m e preferred shape of the said fibres is a very flat lamella, whose length is between 1 and 10 centimetres.
The third main object of t'ne invention is a radioactive waste storage container incorporating a drum provided with a waste introduction cpening and a cover for the tight sealing of said cpening. According to the inventian, the container is entirely made from cancrete of the type described in the preceding paragraphs.
DETAILED DESCRIPTION OF A PREFERRED EME~ODIMENT
The invention and its technical characteristics will be better under-stood frcm reading the following description, illustrated by the single S drawing showing a container according to the invention.
In order to prcduce the ooncrete according to the invention, use is made of the base materials necessary for the prGduction of a conven-tional concrete. These materials are Gonstituted by mineral aggregates, i.e. natural or artificial gravel, sand and cement. To this mixture of solid products in powder fa~m are added loose fibres, i.e. said fibres can assume any randam position. Once this mixture has been made, the hydraulic binder, preferably oonstituted by water, is added. This is followed by mixing in a machine, so as to obtain an intimate mixture of the different components.
The second phase of the process aocording to the invention obviously Gonsists of pouring the fresh ooncrete into the foIm, whose internal shape Gorresponds to the external shape of the praduct to be obtained.
In order to facilitate this operation, the form or mould is generally plaoed an an operating vibrating table. The vibratians make it pos-sible to obtain a very oompact concrete and give a product having avery low porosity. A good surfa oe appearance and a high mechanical strength can also be obtained by using the said vibrating table.
Internal vibrating means can be used far large parts. It should be noted that the po~ition of the fibres is of a randam nature.
Certain products require the use of an internal reinforcement, such as a metal reinforcement, with a view to reinforcing the mechanical prop-erties of the product obtained. The reinforcement is then intraduced into the mould prior to the pouring of the concrete.
Following a first drying period, the concrete is demoul~ed, i.e. the fram is dismantled and removed fram the fluid or cast cancrete. This is followed by a drying phase with respect to the product obtained for the purpose of hardening the concrete. This phase is a cure, which can last fram one day to one month. The duration of the cure varies as a function of the cement type used and the type of praduce manufac-tured. During this cancrete cure, there is a cement hydratian reaction, which is known as concrete setting.
According to the invention, this is followed by a heat treatment per-mitting an energy transfer by varying the temperature of the fibres so that their shapes or sizes evolve. Thus, under the action of a slight temperature rise or fall, such a fibre type assumes a retracted shape or reassumes an initial shape.
A first category of fibres used for this purpose is constituted by so-called shape memory metal fibres. Thus, when a metal or an ordinary alloy is subject to a mechanical stress in excess of its yield point, it underg oe s a plastic defonmation which persist~ after the stress has been discontinued. Its shape and size are then v1rtually subject to no further evolution if the alloy or metal undergoes subsequently a heat treatment of any type. However, shape memory alloys do not have this behaviour, because within a certain temperature range, a sa~ple of such a material can undergo an apparently plastic deformation of several percent and integrally reassume its initial shape by simply heating at a later time. This shape memory phenamen~n is associated with a reversible structural transformation of the ~martensitic thermo-elastic~ type occurring between a first temperature Tl, at which the sample was fonTed, and a second temperature T2 higher or lower than Tl, to which the sa~ple must be heated or cooled fa,r it to reassume its shape.
In the process according to the invention use is made of fibres whose initial shape was that which it was wished to give them to enable the concrete to be compressed, i.e. prestressed. This shape is preferably a retracte~, curved, more or less curled up sh~pe compared with an intermedLate shape, which will tend to be linear or completely straight.
?
hmong the materials used, reference can be made to alloys of the NiTi type (nickel, titanium and dopants) and the CuZnAl type (brass, aluminium and dopants). For such alloy types, the temperature varia-tion can be a rise between 50 and 70C, i.e. for a concrete prcduct at 20C, a heat treatment at a temperature between 70 and 90C can make it possible to return to the initial shape of the metal fibres cast in the concrete. The same result can be obtained by cooling to a temper-ature between -10 and -30C.
The duration of the application of the heat treatment is a function of the shape of the product produced with the concrete. In general tenms the entire product, i.e. even the product core, must reach the phase transfonnation temperature.
If the product produced is transportable, the heat treatment can be applied in the oven. However, if the product is moulded in situ, i.e.
is not transportable as a result of its weight and dimensions, the heat treatment application process can take place by means of high fre-quencies or microwaves using heating sheaths or jackets.
Tension tests by bending at three points were carried out on 4 x 4 x 16 om testpieces. The concrete used had the following constitution:
oenent CLC 45 890 g Bayeux sand 2660 g water 450 g fluidifier 8 g The incorporation of the shape memory fibres takes place after mixing the four components. The heat treatment takes place for 24 hours at 80% in a tight pack to avoid dIying out and then for 24 hours at ambient temperature fo,r cooling prior to the mechanical tests. The tests were carried out in the aOGEMA, m e Hague, concrete laboratory in a 1.5 litre mixer.
The following table summarizes the values obtained:
AGE 14 days 28 days FIBRES (kg/m ) O 50 90 0 50 105 No heat treatment 6.17 6.89 7.65 6.987.68 7.21 With heat treatment 7.37 7.89 7.43 7.758.00 7.84 For fibre-free testpieces, the heat treatment impr~ves the bending strength of the cancrete or mortar (improvement of the cement setting process) by approximately 1 MPa.
For fibre-oontaining testpieces, the tests performed with fibre con-cretes with 50 and 100 kg of fibres per m3 of f m ished concrete shcws that the results are more conclusive (excluding experimental err~rs) with the fibres than without them and with the heat treatment than without it.
A second category of fibre used consists of thermoretractable fibres.
Such a fibre is subject to a reduction in size with a slight temper-ature rise or fall. If the shape is not rect;linear and preferably well curved, the thermoretractable fibres, an retracting, impart a compressive stress to the concrete in which they are embedded. The shape of the fibres used is preferably that of flat lamellas, whose length can be between 1 and 10 centimetres. The thickness can be less than one tenth of a millimetre.
Any randam product can be prcduct with the aid of such a concrete.
However, a special application of the invention is the prcduction of radioactive waste storage containers. Thus, with reference to the single drawing, the container according to the invention essentially comprises a drum 10,, whose upper cpening is sealed by a cover 12.
The sealing is tight in order to make it possible to store low or medium activity radioactive waste coated with a filling material. In the example shown in the drawing, the container is parallelepipedic, ~5~
has a flat bottom and a side wall with a square section. The upper end of the latter defines the opening permitting the closure with the aid of the co~er 12.
According to the invention, the complete container, i.e. the drum 10 and the cover 12 is made fram a concrete reinforced by fibres 20 either of the shape memory, or of the thermoretractable type.
me drum 10, like the cover 12, is produced by moulding. In particular, the upper end of the side wall of the drum 10 has a stepped shape successively defining, passing from the outside to the inside of the drum 10, a planar end faoe 13 and a planar support or bearing face 7 parallel to the first planar fa oe 13, but set back with respect thereto.
me bearing face 7 is connected to the upper surface 13 by an inclined, intem al, peripheral edge 6 forming a Z in cross-section with its two first surfa oes 7 and 13. me diameter of the inclined edge 6 increases on approaching the bearing surfaoe 7, 80 that said inclined edge 6 forms an angle of at least 10- with the axis of the drum 10.
The cover 12 also has a peripheral stepped zone with, starting fram its upper surface, an inclined, outer, peripheral edge 11 and a vert-ical edge 15 set back from the inclined edge 11. These edges 11 and 15 are connected by a second planar bearing face 5 parallel to the upper and lower faces of the cover 12. The diameter of the inclined edge 11 increases on appr~aching the second bearing surface 5, so that said inclined edge 6 fo,rms an angle of at least 10- with the axis of the cover 12.
When the co~er 12 is placed an the drum 10, the lower part of the oover12 defined by the edge 15 is fitted into the opening fonmed at the top of the drum 10, until the horizontal bearing surface 5 of the cover 12 bears on the horizantal bearing surface 7 of the drum 10. As can be seen in the drawing, the inclined edges 6 and 11, which have the same height, then face ane another and define between them a do~etail-shaped annular space 14, whose width is substantially canstant from the upper ~fi~ ~L,~
face 13 of the ccntainer 10 to the bearing surface 7. This annular space 14 constitutes a keying slot.
In order to tightly flx the said cover 12 to the drum 10, into the aforementioned annular space 14 is cast a keying joint produced frcm the same material as the remainder of the container, i.e. concrete reinforced by shape memory or thenmoretractable fibres 20.
This fo~mation of the keying joint in the upwardly c~en annular space 14 ensures the tight sealing of the container without it being neces-sary to use a fonm. Moreover, the shape of the key mg joint avoids any risk of the cover flying off when the joint is prcduced.
Advantageously, the cover 12 is centrally provided with a large opening 8 in which is formed a keying slot 9. Therefore the container 10 can be filled follcwing the sealing of its cover 12. When the waste has been intrcduced by the c~ening 8, the filling material is introduced until the opening 8 is completely sealed. When the f~lling material i8 constituted by thermoretractable or shape memory fibre-reinforced concrete identical to that forming the actual container, a hamogeneous assembly is formed, where the risks of cracks and breaks are eliminated.
Finally, to permit the handling of the container, various means can be provided. In exemplified manner reference can be made to rods or rings 4 sealed anto the upper, planar end face 13 of the drum 10. A handling groove or slot 3 can be fonmed by moulding on the outer peripheral sur-face of the drum lO in the vicinity of said upper end face 13.
This descriptian of a container only represents an exemplified embcdi-ment of objects which can be manufactured with the aid of the concrete according to the invention. Thus, it is possible to prestress any randam object made in general terms from an ordinary cancrete by simply introducing such fibres into the mixture prior to the praduction of the concrete. A heat treatment subsequently applied after the object has been dried makes it possible to obtain within the concrete ccmpressive stresses equivalent to the prestresses imposed by canventional methods used far prestressed cancrete.
Claims (8)
1. Process for prestressing a concrete produced from a given mixture consisting of introducing in a random manner into the mixture fibres (20), whose shapes or sizes can evolve m time under the action of an energy transfer, pouring the concrete into a form, demoulding the cast concrete, hardening the concrete during a curing period and then carrying out a heat treatment in such a way that the dimensions or shape of the fibres (20) evolve, so as to impose mechanical compres-sive stresses within the concrete.
2. Fibre concrete constituted by an agglomerate of sand, gravel and cement joined by means of a hydraulic binder, artificial fibres (20) embedded in the agglomerate at various, random positions, characterized in that the fibres (20) are of the type whose dimensions or shape can evolve in time under the action of an energy transfer in order to create a compressive stress in the concrete.
3. Concrete according to claim 2, characterized in that the fibres (20) are made from a shape memory metal allay.
4. Concrete according to claim 3, characterized in that the shape memory metal alloy is an alloy of titanium and nickel.
5. Concrete according to claim 3, characterized in that the shape memory alloy is an alloy of brass and aluminium.
6. Concrete according to claim 2, characterized in that the fibres (20) are thermoretractable.
7. Concrete according to any one of the claims 2 to 6, characterized in that the fibres (20) are very flat lamellas, whose length is between 1 and 10 centimetres.
8. Radioactive waste storage container, incorporating a drum (10) pro-vided with a waste introduction opening (8) and a cover (12) for tightly sealing the opening (8), characterized in that it is made from a concrete according to any one of the claims 2 to 7.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9102340 | 1991-02-27 | ||
| FR9102340A FR2673223A1 (en) | 1991-02-27 | 1991-02-27 | CONCRETE AND PRECONTROLLING METHOD, CONTAINER MADE WITH THE CONCRETE. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2061541A1 true CA2061541A1 (en) | 1992-08-28 |
Family
ID=9410151
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002061541A Abandoned CA2061541A1 (en) | 1991-02-27 | 1992-02-19 | Concrete and its prestressing process and container manufactured with this concrete |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0501879B1 (en) |
| JP (1) | JPH058217A (en) |
| KR (1) | KR920016682A (en) |
| CA (1) | CA2061541A1 (en) |
| DE (1) | DE69203895D1 (en) |
| FI (1) | FI920848A (en) |
| FR (1) | FR2673223A1 (en) |
| TW (1) | TW199228B (en) |
| ZA (1) | ZA921409B (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2705824B1 (en) * | 1993-05-24 | 1995-07-28 | Electricite De France | Aerated concrete container for the storage of radioactive waste. |
| FR2709291B1 (en) * | 1993-08-27 | 1995-09-22 | Electricite De France | Storage container for toxic waste with watertight closure and its manufacturing process. |
| WO1996012588A1 (en) * | 1994-10-19 | 1996-05-02 | Dpd, Inc. | Shape-memory material repair system and method of use therefor |
| DE4439534A1 (en) * | 1994-11-04 | 1996-05-09 | Horst Dr Ing Kinkel | Concrete body with reinforcement |
| US5858082A (en) * | 1997-09-15 | 1999-01-12 | Cruz; Hector Gonzalo | Self-interlocking reinforcement fibers |
| IT1296234B1 (en) * | 1997-10-21 | 1999-06-18 | Larco Astori S P A | USE OF FIBERS IN CONCRETES INTENDED FOR THE PRODUCTION OF STRUCTURAL ELEMENTS IN PRE-PRESSED CONCRETE AND RELATED PRODUCTS |
| JP2002323593A (en) * | 2001-04-27 | 2002-11-08 | Ishikawajima Harima Heavy Ind Co Ltd | Concrete cask |
| JP2004077244A (en) * | 2002-08-14 | 2004-03-11 | Mitsubishi Heavy Ind Ltd | Fiber reinforced concrete cask, support frame body for forming the same, and method for manufacturing concrete cask |
| WO2006038225A2 (en) * | 2004-10-06 | 2006-04-13 | Patwa Saurabh S | A reinforcing fiber for concrete, a flexible concrete and a method to prepare the concrete |
| GB0715123D0 (en) * | 2007-08-03 | 2007-09-12 | Univ Cardiff | Prestressing or confinement of materials using shape memory polymers |
| DE102012019125B4 (en) * | 2011-10-06 | 2016-07-07 | Peter Markwirth | Radiation protection container for light and medium weight radioactively contaminated material. |
| JP5187603B1 (en) * | 2012-04-25 | 2013-04-24 | 豊 土屋 | Plastic compound and waste treatment, storage container and storage method using the same |
| JP5768197B1 (en) * | 2014-08-11 | 2015-08-26 | 昌樹 阿波根 | Prestressed concrete for non-main structural members |
| JP7017672B2 (en) * | 2016-04-01 | 2022-02-09 | 株式会社Ｈｐｃ沖縄 | Manufacturing method of fiber cell structure concrete |
| DE102018107926A1 (en) * | 2018-04-04 | 2019-10-10 | Universität Kassel | Microfiber reinforced high performance concrete |
| CN111189768B (en) * | 2018-11-14 | 2023-03-10 | 青岛理工大学 | Corrosion-driven intelligent fiber and preparation method and application thereof |
| CN111364759A (en) * | 2020-03-18 | 2020-07-03 | 重庆交通建设(集团)有限责任公司 | Prepressing device of full-scale support of giant open-web girder steel pipe and construction method thereof |
| CN112759291B (en) * | 2020-12-31 | 2022-06-17 | 东南大学 | High-temperature burst resistant UHPC (ultra high Performance polycarbonate) mixed with shape memory alloy fibers and preparation method thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1297243A (en) * | 1961-05-16 | 1962-06-29 | Kogyogijutsuin Cho | Method for imparting stress to steel bars inside reinforced concrete |
| FR1434373A (en) * | 1965-02-26 | 1966-04-08 | Commissariat Energie Atomique | Manufacturing process of prestressed materials and materials thus obtained |
| JPS56100162A (en) * | 1980-01-11 | 1981-08-11 | Mitsui Petrochemical Ind | Fiber reinforced concrete and its reinforced material |
| CH663758A5 (en) * | 1983-06-03 | 1988-01-15 | Bbc Brown Boveri & Cie | METHOD FOR PRODUCING A COMPOSITE WITH HIGH TENSILE STRENGTH CONSISTING OF A PLASTIC MATRIX WITH EMBEDDED REINFORCEMENT. |
| DE3345592A1 (en) * | 1983-12-16 | 1985-08-01 | Gerhard 7274 Haiterbach Dingler | LARGE AREA, PANEL-SHAPED COMPONENTS |
-
1991
- 1991-02-27 FR FR9102340A patent/FR2673223A1/en not_active Withdrawn
-
1992
- 1992-02-19 CA CA002061541A patent/CA2061541A1/en not_active Abandoned
- 1992-02-26 TW TW081101449A patent/TW199228B/zh active
- 1992-02-26 EP EP92400491A patent/EP0501879B1/en not_active Expired - Lifetime
- 1992-02-26 DE DE69203895T patent/DE69203895D1/en not_active Expired - Lifetime
- 1992-02-26 FI FI920848A patent/FI920848A/en not_active Application Discontinuation
- 1992-02-26 ZA ZA921409A patent/ZA921409B/en unknown
- 1992-02-27 JP JP4041576A patent/JPH058217A/en active Pending
- 1992-02-27 KR KR1019920003029A patent/KR920016682A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| TW199228B (en) | 1993-02-01 |
| FR2673223A1 (en) | 1992-08-28 |
| FI920848A0 (en) | 1992-02-26 |
| KR920016682A (en) | 1992-09-25 |
| DE69203895D1 (en) | 1995-09-14 |
| EP0501879B1 (en) | 1995-08-09 |
| FI920848A (en) | 1992-08-28 |
| EP0501879A1 (en) | 1992-09-02 |
| JPH058217A (en) | 1993-01-19 |
| ZA921409B (en) | 1992-11-25 |
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