FR2836502A1 - A method of reinforcing a structure in a material such as concrete by applying to its surface fibers and a substance containing micro-organisms which then mineralize and produce a solid coating - Google Patents

Abstract

A method of reinforcing a structure by applying to it reinforcing fibers and a substance containing micro-organisms and allowing part of the substance to mineralize in situ, thereby creating a matrix coating the fibers The fibers may either be applied in successive layers each with a quantity of the substance containing the micro-organisms and allowed to mineralize or drying and/or mineralization may take place between coats. A coat of the substance may be applied to the substrate before the fibers and/or over the final fiber coat. The fibers, or a majority of them are oriented effectively parallel to the surface of the structure. A mesh of fibers with the substance may also be inserted into holes drilled into the structure. In addition to the micro-organisms the substance may contain cement powder with a particle size below 10 micronsm and also nutrients for the micro-organisms. An Independent claim is included for a structural reinforcement comprising a composite material incorporating reinforcing fibers coated in a matrix adhering to the structure to be reinforced which comprises at least one mineral part obtained by the in situ mineralization of micro-organisms. The fibers form 40 wt.% and the coating 60 wt.% of the reinforcement.

Description

in position by means of a handle (15).

  METHOD FOR STRENGTHENING A STRUCTURE WITH A MATERIAL

  COMPOSITE AND REINFORCE OBTAINED BY THIS PROCESS

  The present invention relates to composite structural reinforcements

used in construction.

  In particular, it concerns fiber reinforced reinforcements which are placed on certain structures to increase the load resistance.

to which they are subject.

  These reinforcements are often flat and glued on surfaces of concrete structures, or on other types of structure. It may also include elongated portions penetrating into the volume of a building structure or a natural massif. They typically consist of carbon fibers embedded in a synthetic adhesive resin, especially a resin

epoxy type.

  Carbon fibers have excellent mechanical properties when working in tension. In these reinforcements, they are arranged in unidirectional locks or fabrics. In the latter case, the chain of the fabric is oriented in a main reinforcement direction and a greater or smaller proportion of fibers in the weft direction makes it possible to obtain a certain degree of reinforcement perpendicularly to the main direction. The solidification of the resin is obtained by polymerization or polycondensation of compounds that it incorporates. After solidification, the resin constitutes a fiber coating matrix which gives its cohesion to the composite reinforcement. Advantageously, it can also be used to ensure the adhesion of the reinforcement to the substrate which is coated therewith. Epoxy resins are used which have a very good adhesion to building materials such as concrete, as well as excellent resistance to shear stresses.

  to which the gluing plan is subjected.

  A disadvantage of using an epoxy resin in these composite reinforcements is its poor behavior at high temperatures. A glass transition of the resin causes a strong attenuation of the reinforcement

  when the temperature becomes higher than 50 - 60 C approximately.

  By law, the structural behavior of certain structures in the event of fire must be such that the structure withstands minimum durations when exposed to temperatures of the order of 100 C. If flat composite reinforcements are used, it is necessary to then make arrangements to slow down the progress of the heat towards the gluing planes. These provisions

  are expensive, and they lead to an undesirable bulk.

  An object of the present invention is to provide a method of reinforcing a structure whose reinforcing effect is preserved in

  a large measure when the temperature rises.

  The invention provides a method of reinforcing a structure, wherein reinforcing fibers and a substance containing microorganisms are applied to the structure, and at least a portion of said substance is mineralized in situ to produce a embedding matrix of the reinforcing fibers. An advantage of the reinforcing process according to the invention lies in the fact that the coating matrix of the reinforcing fibers is of a mineral nature, which makes it possible to retain the reinforcing effect of the structure when the temperature rises, for example above 50 C.

  reinforcing fibers are typically, but not exclusively, carbon.

  Furthermore, the reinforcement method according to the invention is particularly suitable when the structure has a material on the surface.

  such as concrete, brick, cement, mortar or mineral conglomerate.

  Indeed, the coating matrix of the reinforcing fibers then has a similarity of composition with the surface material of the structure, which is

  favorable for a good adhesion of the composite reinforcement on the structure.

  In one embodiment of the method, at least one layer of reinforcing fibers is applied to one surface of the structure, each layer being applied with a quantity of the substance containing microorganisms, and said substance is mineralized in situ in each layer. . The following advantageous arrangements can be used in this embodiment: several layers of reinforcing fibers are successively applied to said surface of the structure, and eVou drying is carried out at least partially in each layer prior to the application of the next layer; a preliminary phase of application of an underlayer of the substance containing microorganisms on said surface of the structure is carried out; an additional step of applying a surface layer of the substance containing microorganisms is carried out over the last layer of reinforcing fibers; the reinforcing fibers are oriented substantially parallel to said surface of the structure; a majority of the reinforcing fibers are oriented substantially parallel to a principal direction of reinforcement parallel to said surface of the structure; each layer of reinforcing fibers comprises at least one fiber fabric. In another embodiment of the method, which may optionally be combined with the preceding one, at least one wick of reinforcement fibers is introduced with substance containing microorganisms in a borehole present in the structure. mineralize in situ said

substance in the drilling.

  The invention proposes other characteristics which advantageously combine with the above process, in particular: the reinforcing fibers can be impregnated with a substance containing microorganisms before they are applied to the structure; at least part of said substance containing microorganisms may further contain a cement powder, preferably having a particle size of less than 10 m; at least a part of the substance containing microorganisms

  may further contain nutrients for microorganisms.

  Another aspect of the present invention relates to a structural reinforcement, comprising a composite material incorporating reinforcing fibers embedded in a matrix adhering to a structure to be reinforced, wherein the matrix comprises at least one mineral part obtained by mineralization in situate of microorganisms. In volume, such a composite reinforcement typically comprises approximately

  % of reinforcing fibers and 60% of coating matrix.

  Other features and advantages of the present invention

  will appear in the following description of an example of a non-implementation

  limiting, with reference to the single attached figure, which shows a beam

  reinforced according to the invention.

  Biological compositions containing microorganisms capable of forming an inactivated mineral material are known, in particular according to European Patents 0 388 304 and 0 708 836 to which reference may be made. These compositions are generally aqueous solutions. They incorporate microorganisms that assimilate compounds based on mineral elements, and which accumulate these mineral elements in solidified form. Such microorganisms are, for example, bacteria or viruses. Other living structures, or parts of living structures, are also

  capable of such transformations of compounds based on mineral elements.

  For example, dicotyledonous or monocotyledonous plants, ferns, algae, lichens, fungi, or living cells or tissues of animal or plant origin may be mentioned. These living structures can also be used in the process of the invention, possibly adapting its implementation to the particularities of each living structure. The biological composition may also contain a mixture of microorganisms

  eVou living structures of many types.

  For the implementation of the process of the invention, such a composition must contain microorganisms in sufficient quantity. For this, a particular preparation is necessary which comprises a phase of multiplication of microorganisms. Placed under favorable conditions, especially at a suitable temperature and in the presence of oxygen and appropriate nutrients, such microorganisms can multiply in considerable proportions. During this phase of culture, their population can follow an exponential evolution, so that large quantities of microorganisms can be obtained in relatively short time, and with reduced costs. The substance used as precursor in the process of the invention comprises such a blological composition. In order to facilitate its application on a structure, especially on a vertical surface, the biological composition may be combined with additives to form a liquid-like substance, glue, paste or gel that can be easily handled. Once the precursor is applied to a mineral surface, the microorganisms feed on the mineral elements of this surface, and accumulate them in solidified form constituting a hard mineral binder. This accumulation then corresponds to a mineralization, or petrification, of the biological composition, resulting in the matrix of the reinforcing composite material. A drying of the solution can take place simultaneously. The mineral elements accumulated by the microorganisms are for example based on calclum or silica. In the case of calcium-based elements, the mineralization of the composition

  includes the calcification of microorganisms.

  Depending on the nature of the microorganisms used, additional nutrients, which can be assimilated by at least some of the microorganisms present in the solution, can be added to the biological composition in the precursor, before it is used, so that microorganisms participate more effectively in the accumulation of elements

  minerals, once the precursor is applied to the structure.

  A cement powder may also be introduced as an additive into the precursor prior to its application to the structure, to improve the cohesion of the resulting matrix. This cement powder is preferably finely ground before its addition to the blological composition, for example up to a particle size of less than 10 m. The cement used for this powder can

  be artificial Portland cement (CPA) or overburdened Klinker.

  The reinforcing fibers used may be of various kinds, in particular synthetic or natural, organic, vegetable or mineral fibers. Carbon fibers, in particular, in addition to their particularly high mechanical strength, do not participate in the propagation of a possible fire, as long as the temperature is below 1800 C. In a manner known per se, the reinforcing fibers are woven between they, or held together by weft threads or by glue filaments, for

  be easily handled in the form of tablecloths.

  Apart from the use of a precursor containing microorganisms, the formation on the structure of the composite reinforcing material can take over one of the commonly used methods based on bonded fiber fabrics. Such a method is described, for example, in the patent application

European 0 799 951.

  By way of illustration, Figure 1 shows a horizontal beam of reinforced concrete 10 resting at its two ends on vertical posts 11, 12 and subjected to loads that bend. In a manner known per se, a reinforcement of the beam 10 may be provided by carbon fibers bonded to the lower surface 1 of the beam 10. For this purpose, the surface 1 of the beam 10 is first coated with a layer of carbon fiber. a precursor 2 as previously described. This coating may be carried out in various ways, such as, in particular, an application of the precursor by means of a brush, a spreading roller or an application nozzle. The precursor is spread on the surface 1 so as to form an approximately uniform layer 2 of thickness between about 0.5 and 3 millimeters, and in particular between 1 and 2 millimeters. Partial drying eVou partial mineralization of the precursor 2 thus applied

  on the surface 1 can then be performed before applying the fibers.

  In order to improve the attachment and bonding of this precursor layer on the surface 1 of the beam 10, a preliminary treatment of the surface 1 can be carried out, adapted according to its surface state

  (scraping, sanding, cleaning, chemical treatment, ...).

  In an application such as that illustrated in FIG. 1, there is provided a principal reinforcement direction A corresponding to the longitudinal direction of the beam 10. Each layer of carbon fibers 3 may then consist of unidirectional locks. assembled by a removable support sheet or by a few weft son 3, these locks being oriented parallel to the main direction A. It is also possible to use a carbon fiber fabric having a greater proportion of fibers in the warp direction than in the direction frame, orienting the chain parallel to the main direction A. Isotropic reinforcement in the gluing plane can be obtained by using a fabric having the same proportion of carbon fibers in the

in the warp and in the weft direction.

  After placing the fabric 3, a pressure force is applied to it by means of an applicator roller to make the underlying precursor 2 penetrate into the interstices present between the carbon flanges 4. Optionally, this pressure force can be of sufficient intensity. to cross the fabric 3

by the underlying precursor.

  The fiber fabric 3 can also be applied to the surface 1 after having been

  pre-impregnated with a precursor substance containing microorganisms.

  This substance may be the same as that of precursor 2, the surface 1 of which is coated. Such impregnation of the fibers, prior to their application on the surface 1 of the beam 10, may be obtained by various methods such as coating, dipping or sizing. These processes may optionally be combined with a pumping of the amber gas so as to promote the penetration of the liquid between the fibers 4. Another possible method consists of pressing the fibers 4 and the precursor between rollers.

deposited in lamnor.

  2s A second layer of precursor 2 containing microorganisms may optionally be applied to the fabric 3 of carbon fibers. This second layer, for example of the same thickness as the first, makes it possible to complete the coating of the fibers 4. A complete coating of the fibers 4 has several advantages: increase of the reinforcement obtained, particular aesthetic effect, and protection of the carbon fibers against external aggression. Such aggression is, for example, of a chemical nature, caused by pollutants in contact with the beam 10, or by - 8

  a paint covering the composite reinforcement.

  Several layers of fibers, pre-impregnated or not, can be applied successively, according to the same method as above. The number of layers will depend on the required reinforcement and the characteristics of an individual layer, especially in terms of carbon fiber density. At least a partial drying time of at least partial mineralization of the matrix precursor of each layer can be observed before application.

of the next layer.

  The resulting composite reinforcement has approximately 0% volume, about 40% carbon reinforcing fibers and 60% matrix.

enrobing mineral.

  Depending on the composition of the precursor used, the hardening of the matrix around the fibers 4 may require a duration of between a few hours and a few weeks. This duration is a function of the ambient atmospheric conditions, in particular the temperature and the quantity of oxygen available. This hardening proceeds simultaneously with a

  drying and mineralization caused by the activity of microorganisms.

  This activity of the microorganisms must be continued for a sufficient time to obtain a matrix of the composite material which exhibits good mechanical behavior. Depending on the nature and type of the microorganisms used, the addition of nutrients in the biological solution prolongs

this activity.

  The reinforcement method described above can be adapted according to the configuration of the structure to be reinforced, according to its layout, its geometry, its constitution, etc. It can thus be adapted to

  arrangements of the kind described in European Patent Application 0 837 202.

  In this case, drilling is practiced in the structure to receive carbon fiber locks coated matrix precursor. These holes can be used to cross obstacles present on the surface of the structure, to avoid that the fabric has to circumvent them. They may also extend transversely to the surface to be reinforced: the bits drilled in the borehole are allowed to protrude on the surface, the overlying fibers are spread over the surface and covered by the reinforcement fabric. This arrangement

  improves the breaking strength of the assembly.

  Another type of structural reinforcement that can be performed according to the invention is the installation of tie rods or consolidation in a natural or artificial massif. A tie rod is laid by drilling into the solid mass and inserting wicks or carbon fiber fabrics and matrix precursor material. The precursor then acts to seal the tie

in the structure.

- 10

Claims (16)

R E V E N D I C A T IO N S   A method of reinforcing a structure, characterized in that reinforcing fibers (4) and a substance (2) containing microorganisms are applied to the structure (10) and mineralized. in situ at least a portion of said substance to produce a coating matrix of reinforcing fibers.   The process according to claim 1, wherein at least one layer of reinforcing fibers is applied to a surface (1) of the structure (10), each layer being applied with an amount of the substance containing microorganisms, and in which the substance is mineralized in situ in each layer.   3. Method according to claim 2, wherein one applies successively several layers of reinforcing fibers on said surface (1) of the structure (10), and in which one performs a drying eVou at least partial mineralization in each layer before the application of the next layer.   4. Method according to claim 2 or 3, comprising a prior phase of application of an underlayer of the substance containing   microorganisms on said surface (1) of the structure (10).   5. Method according to any one of claims 2 to 4,   comprising an additional step of applying a surface layer of the microorganism-containing substance, over the last layer of reinforcing fibers.   6. A method according to any one of claims 2 to 5, in   which the reinforcing fibers (4) are oriented substantially parallel to   said surface (1) of the structure (10).   7. The method according to claim 6, wherein a majority of the reinforcing fibers (4) are oriented substantially parallel to a principal reinforcing direction (A) parallel to said surface (1) of the structure (10).   - 11 The method of claim 6 or 7, wherein each layer   reinforcing fibers comprises at least one fiber fabric (3).   9. Process according to any one of the preceding claims,   wherein at least one wick of reinforcing fibers, with substance containing microorganisms, is introduced into a borehole present in   the structure, and the substance is mineralized in situ in the borehole.   10. Process according to any one of the preceding claims,   wherein the reinforcing fibers are, prior to their application on the   structure (10), impregnated with a substance containing microorganisms.   11. Method according to any one of the preceding claims,   wherein at least a part of said substance containing micro-organisms   organisms additionally contains a cement powder.   12. The method of claim 11, wherein the cement powder   has a particle size less than 10 m.   13. Process according to any one of the preceding claims,   wherein at least a part of said substance containing micro-organisms   organisms also contains nutrients for microorganisms.   14. Process according to any one of the preceding claims,   wherein the reinforcing fibers (4) are carbon.   Structural reinforcement comprising a composite material incorporating reinforcing fibers (4) embedded in a matrix adhering to a reinforcing structure (10), characterized in that the matrix comprises at least   a mineral part obtained by in situ mineralization of microorganisms.   16. Reinforcement according to claim 15 having, in volume, approximately