GB2583779A

GB2583779A - Compositions

Info

Publication number: GB2583779A
Application number: GB1908396.3A
Authority: GB
Inventors: Margarida Armada Bras Ana; Bushir Mohammed Hazha; Nakouti Ismini
Original assignee: Liverpool John Moores Univ
Current assignee: Liverpool John Moores Univ
Priority date: 2019-05-10
Filing date: 2019-06-12
Publication date: 2020-11-11
Also published as: WO2020229797A1; EP3966180A1; GB201908396D0

Abstract

A bioproduct is disclosed which comprises at least one strain of Shewanella, also disclosed are biocement compositions comprising the bioproduct, methods of their manufacture, bioconcrete compositions comprising the biocement and methods of their manufacture, where the bioproduct, biocement and bioconcrete compositions and products, are used especially in the control, prevention or repair of corrosion in reinforced concrete structures. The bioproduct may further comprise other bacteria such as Streptomyces, Nocardia, Micromonospora, Arthrobacter, Chromobacterium, Pseudomonas, Escherichia coli, Salmonella typhimurium, Geobacter, Raoultella terrigena, Staphylococcus spp., Escherichia coli and Salmonella.

Description

COMPOSITIONS

The present invention relates to a bioproduct, biocement compositions comprising the bioproduct, methods of their manufacture, bioconcrete compositions comprising the biocement and methods of their manufacture, the invention also includes methods of, and uses for, the bioproduct, biocernent and bioconcrete compositions and products, especially but not exclusively: in the control, prevention or repair of corrosion in reinforced concrete structures.

BACKGROUND

Cement is a binder, a substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together Cement mixed with fine aggregate produces grout and mortar for masonry, or with sand and gravel, produces concrete.

Concrete is one of the most used construction materials worldwide as it is strong and relatively cheap. Current design for durability is through prescriptive guidance and includes factors such as the disposition of reinforcement to control cracking and crack widths, thickness of concrete cover to reinforcement, quality of concrete and management of water.

However, concrete is subjected to a number of degradation processes which hamper the structure to reach its required service life. Problems caused by the corrosion of reinforcement in deteriorating concrete structures are widely encountered and are recognized as a major limitation upon the durability of many existing structures. The primary reason for premature corrosion is crack formation in the concrete cover. Larger cracks as well as a network of finer cracks allow water, oxygen, chloride, and other aggressive corroding substances to penetrate the concrete matrix to reach the reinforcement. Other forms of deterioration due to processes such as frost action and alkali-silica reaction are less widespread in their occurrence, but no less significant in their effects. Accordingly, to anticipate durability problems during the lifetime of a structure, costly measures of maintenance and repair have to be undertaken.

It is known from the prior art to use natural, biological material such as bacteria as an additive to concrete to produce a "bioconcrete". For example, a number of Bacillus, Pseuclornonas and Ureolytic strains have shown promise in sequestration and capture of CO2 and in reducing or eliminating CO2 emissions from buildings in addition to accelerating the precipitation process of calcium carbonate [CaCO2] in concrete pores. Typically, when incorporated into mixtures these bacteria are encapsulated. US 8,460,458 also describes encapsulated bacterial spores of Bacillus pseudotinnus or Sporosarcina pasteurii and/or organic compounds loaded onto porous particles in a process to decrease permeability of cracked concrete. The porous particles are activated by the addition of water. Furthermore, it is known from US 9,676,673 to use bacteria that can form a phosphate or a carbonate precipitate in an alkaline medium such as those from the genera Planococcus, Bacillus and Sporosarcina in a liquid bilayer that can be coated onto concrete thereby forming a gel that acts as a crack filler. However, there are disadvantages associated with the microbial treatment of construction materials with microbially induced calcium-carbonate precipitation [MICP] for example, high cost of bacteria culture media or enzyme preparations; toxicity of compounds from the metabolism of bacteria, namely products resulting from the hydrolysis of urea in MICP processes and life-time of calcite crystals.

Metal chelating agents are produced by a variety of microorganisms, including 15 Streptomyces, Nocardia, Micromonospora, Arthrobacter, Chromobacterium, Pseudomonas. Escherichia coil, Salmonella typhimuriurn, Geobacter, Shewaneila and some nitrogen-fixing bacteria such as Klebsiella pneurnoniae and Klebsiella terrigena.

Shewanella is the sole genus included in the marine bacteria family Shewanellaceae and are found in extreme aquatic habitats where the temperature is very IOW and the pressure is very high. Shewanella are heterotrophic facultative anaerobes. This means that, in the absence of oxygen, members of this genus possess capabilities allowing the use of a variety of other electron acceptors for respiration, for example thiosulfate, sulfite, elemental sulfur, fumarate, nitrate, nitrite and arsenic in addition to a wide range of metal species, including manganese, chromium, uranium and iron. The metal-reducing capabilities of Shewanella can potentially be applied to bioremediation of metal-contaminated groundwater, its ability to decrease toxicity of various substances has hitherto made Shewanella a useful tool in bioremediation. Some other examples of facultatively anaerobic bacteria are Staphylococcus spp., Streptococcus spp., Escherichia coil, Salmonella and Llsteria spp.

Cement and concrete compositions leading to self-healing construction ma ials with higher strength and durability, thus increasing reinforced concrete life would offer mediate benefit to the industry.

There is a need to provide cement and concrete compositions with self-healing behaviour for controlling corrosion reactions in concrete and a product for the repair of existing reinforced concrete.

BRIEF SUMMARY ARY OF THE DISCLOSURE

According to a first aspect of the invention there is provided a bioproduct comprisine Shewanella for use in preventing and/or repairing corrosion in concrete.

Preferably, the Shewanella is selected from the group comprising S. abyssi, S. aestuarii, S. algae, S. algicola, S. algidipiscicoia, S. amazonensis, S. aquimarine, S erotica, S. atiantica, S. baitica, S. basaltis, S. benthica, S. canadensis, S. chiiikensis, S. co/well/ens, S. corailli, S. deco/orationis, S. denitrificans, S. dokdonensis, S. donghaensis, S. fidelis, S. fodinae, S. frigidimarina, S. geetbuli, S. geiidimarina, S. glacialipiscicola, S. gelidii, S. ha fniensis, S. halifaxensis, S. halitois, S. hanedai, S. indica, S. invention's, S. irciniae, S. japonica, S. kaireitica, S. litorisecliminis, S. fiyingstonensis, S. loihica, S. inangroyi, S. marina, S. marinintestine, S. inarisfiayi, S. morhuae, S. oileyana, S. oneidensis, S. oshomensis, S. piezoloierans, S. pacifica, S. pealeana, S. piezotolerans, S. pneumatophor, S. profunda, S. psychrophiia, S. putrefaciene, S. sairae, S. schegeliana, S. sedirninis, S. seohaensis, S. sporeglae, S. surugensis, S. upenel, S. vesiculosa, S. violacea, S. vvaksmanii, S. woody/ and S. xiarnenensis.

Preferably, the bioproduct comprises at least one strain of Shewanella and at least one other bacteria species/strain that is non-pathogenic or substantially non-pathogenic. Preferably, the at least one other bacteria species/strain is selected from the group comprising Streptomyces, Nocardia, Micromonospora, Arthrobacter, Chromobacterium, Pseudomonas, Escherichia coif, Salmonella typhimurium, Geobacter, Raouitelia terrigena, Staphylococcus spp., Escherichia coil and Salmonella or any other substantially non-pathogenic species/strain of bacteria.

Preferably the at least one strain of Shewanella is S. oneidensis.

Preferably, the bioproduct is fluidic and is form of a liquid, solution, powder residue, granule, particulate, pellet, microsphere or the like.

Preferably, the bacteria of the bioproduct are uncapsulated.

According to a further aspect of the invention there is provided a biocement, having mixed or embedded therein, a bioproduct comprising Shewanella, the cement being for use in preventing and/or repairing corrosion in concrete.

According to a yet further aspect of the invention there is provided a method of manufacturing the biocement of the present invention, the method comprising providing a cement base including mixed or embedded therein, a proportion of biproduct the bioproduct comprising at least one strain of a Shewanella bacterium, the bacterium being added when in its dormant state.

According to a yet further aspect of the invention there is provided a self-healing bioconcrete comprising: cement having mixed or embedded therein, a bioproduct comprising at least one strain of Shewanella; CIO water; and (iii) an aggregate of sand and/or aggregate.

Preferably, the bioconcrete comprises iron in the form of rods, bars, rehars, mesh, filings or powder.

In one particular embodiment of the invention the self-healing biococrete comprises the following components: * 0.10 to 0.16 % / m3 of normal Portland cement CEMI 52.5 N; * 0.01 to 0.10 % / m3 of ground granulated blast furnace slag [GGBS]; * 0.35 to 0.40 % / rri3 of course aggregate 20mrn; * 0.24 to 0.35 c)/C) / M3 of course aggregate 10mm; * 0.13 to 0.15 % / m3 of limestone sand; * 0.0001 to 0.0015 %,/ m3 of a bioproduct containing at east one Shewanella strain of bacteria. 30 Optionally, the bioconcrete additionally comprises a superplacticizer in the region of up to 0.002 % / m3 of a superplasticizer.

It will he appreciated that preferred features ascribed to one aspect of the invention applies mutatis mutandis to each and every aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter with reference to the accompanying drawings; in which: Figure 1 shows Pourbaix diagram for Fe-H20 at 25 °C hatch area shows the pH and potential region of steel in concrete [https://doi.orgli 0.1016/B978-1-78242-381-2.00002-X] Figure 2 shows a bar chart of compressive strength (MPa) for concrete type CEMI and CEMIII with and without bioproduct, tested at 28 days.

Figure 3 shows water absorption (Kg/m2) via capillary for concrete types concrete type CEMI and CEMIII with and without bioproduct, tested at 28 days and for 2 weeks.

Figure 4 shows water absorption (Kg/m2) via capillary for concrete types concrete type CEMI and CEMIII with and without bioproduct, tested at 28 days and during the first day.

Figure 5 shows non-steady state migration coefficient (x 10-12 m2/s) for concrete types concrete type CEMI and CEMIII with and without bioproduct during the first 200 days.

Figure 6 shows the ratio of non-steaoy state migration coefficient for concrete types concrete type CEMI and C EMIR with and without bioproduct, in comparison to reference one (CEMI and CEMIll at 28 days).

Figure 7 shows analysis of the microstructure via scanning electron microscope (SEM) at 28 days for CEMIII without bioproduct (Figure TA) and for CEMili with bioproduct (Figure TB).

Figure 8 shows surface electrical resistivity (k0 cm) of hardened concrete samples CEMli I with and without self-healing behaviour (Figure 8A) and CEMI with and without self-healina behaviour (Figure 8B), tested from 28 days until 115 days.

Figure 9 shows superficial electrical resistivity ((0 cm) in a propagation test measured during electrical current injection in the rebars to accelerate corrosion for concrete types concrete type CEMI arid CEMIll with arid without bioproduct.

Figure 10 shows cement after the propagation test, Figure 10A shows CEMI without bioproduct. Figure 10B shows CEMI with bioproduct, Figure 10C shows CEMI II with bioproduct and Figure 10D shows CEMII I with bioproduct

DETAILED DESCRIPTION

Reference herein to a "fluid" or "fluidic" is intended to encompass any substance or material that possess the capability to flow easily and includes liquids, solutions, powders, residues, gels, granules, particulates, pellets, microspheres and the like.

Reference herein to "bioactive" is intended to encompass any substance that is capable of eliciting a biological effect. Reference herein to a "bioproduct" refers to any substance of matter that comprises bioactive agent(s) in particular, bioactive agents(s) that is/are capable of reducing iron (III) oxide [Fe2O3] by iron oxide precipitation (MIIP).

The bioproduct of the present invention comprises "bacterial material" and may also refer to a combination of bacterial materials, such as a combination of two or more of the bacterium, a lyophilized bacterium and the bacterial spore of the bacterium. The term "bacterial material" may alternatively or in addition also refer to a combination of two or more different types of bacteria, such as two or more Shevvanella and other bacteria that are capable of reducing iron (III) oxide [Fe203] by iron oxide precipitation (MIIP), such as and without limitation Streptomyces, Nocardia, Micrornonospora, Arthrobacter, Chromobactedum, P.seudomonas, Escherichia coil, Salmonella typhimurium, Geobacter and Raoultella terrigena.

Reference herein to a "biocement" refers to fluidic cement, mortar or grout that includes the bioproduct of the present invention and is capable of reducing iron (I 1 I) oxide [Fe203] by iron oxide precipitation (MIIP).

Reference herein to a "bioconcrete" refers to a self-healing hardened material suitable for use in the construction industry and comprising aggregates bonded together by biocement and water.

Reference herein to "dormant" or "dormancy" refers to the bacterial material being in a state of having normal physical functions suspended or slowed down for a period of time; in or as if in a deep sleep.

Reference herein to "self-healing" bioconcretes are concretes that are capable of repairing microcracks arid cracks by themselves by virtue of the bioproduct comprising bacterial material embedded therein.

The terms "inhibiting" and "preventing" are used interchangeably and are intended to mean that corrosion of reinforced concrete can be thwarted completely or the rate of corrosion retarded or further corrosion inhibited.

This present invention relates generally to cement compositions including the bioproduct and processes for producing the same, and more particularly cement including bioproduct for controlling corrosion reaction in concrete which includes the cement as a component.

Concrete is a conglomerate of aggregate (such as gravel; sand, and/or crushed stone), water, and hydraulic cement (such as Portland cement), as well as other components and/or additives. Concrete is generally fluidic when it is first made, enabling it to be poured or placed into shapes, and then later hardens; and is never again fluidic.

Steel reinforcement embedded in concrete is inherently protected against corrosion by passivation of the steel surface due to the high alkalinity of the concrete. However, aggressive microenvironment with chlorides increases the risk of corrosion. As concrete may suffer from degradation, such as crack formation, we may consider at least two distinct approaches to prevent and/or repair the concrete: (i) development of self-healing concrete for newly build structures, (ii) and the development of repair systems to increase the durability of existing aged concrete elements (such as concrete structures such as bridges, parking decks, etc.).

The compositions of the present invention offer a more economic and environmentally friendly approach to the production of cement and self-healing concrete and a biofilm that includes non-encapsulated iron reducing bacteria, such as non-encapsulated Shewanella oneklansis cells. The compositions and products of the present invention can provide a resistance mechanism to reinforced steel corrosion. The use of iron containing waste in cement and concrete production can provide a substrate for the growth of the bacteria which precipitate iron oxide (MIIP) and acts to strengthen the concrete.

In the present invention, iron-respiring bacteria and iron oxide materials, are mixed with CEMI to form cement, which enables the cement thus produced to inhibit corrosion reaction in concrete, grout and mortars made with the cement.

According to some references (Abboud et al Applied and Environmental Biology, 2005, 71,811-816; Ghosh et al Indian Journal Experimental Biology, 2006, 44, 336-339; Kouzuma et al Front Microbiology, 16 June 2015 https://doi.oro/10.3389ifmicb.2015.0060;) the optimum pH of the growth medium for S. oneidensis is around 7.5. Concrete that is not exposed to any external influences usually exhibits a pH between 12.5 and 13.5 As shown in the Pourbaix diagram (Figure 1), which defines the range of electrochemical potential and pH for the Fe-H20 system in an alkaline environment, at potentials and pHs normally found within the concrete, a protective passive layer forms on the surface of steel. Results show that our concrete samples present a pH around 10-11 because they are exposed to corrosion. Accordingly, it is surprising that despite the pH of the concretes of the present invention being considered as not within a suitable pH range as a growth medium for bacteria our results contradict this as illustrated in the Examples hereinafter.

There is a limited understanding of self-healing concretes exposed to chlorides from sea water (XS1 areas exposed to airborne salt but not in direct contact with sea water; XS2 --permanently submerged; XS3 -tidal splash and spray zones) regarding their durability. Durability assessment of concrete is crucial to understand the expected service life of Reinforced Concrete (RC) structures. Therefore, microbiology skills for the development of self-healing concretes are combined with corrosion analysis skills in the initiation and propagation stages of corrosion. To test the efficiency of the self-healing tests were developed for the following properties: compressive strength, water absorption, chloride migration tests, resistivity analysis, corrosion velocity tests during the propagation stage (where steel rebars inside the concrete are exposed directly to corrosion), half-cell potential, growing bacteria evolution analysis and SEM.

Preliminary research conducted using iron-respiring bacteria (Shewenella oneidensis), is grown in tryptone soya broth (TSB) to achieve a high concentration of colony forming unit/ml (2.30E+08 cfuiml). The bioproduct is stored in the fridge for at least 5 days to induce dormancy. The bioproduct is then added to the concrete mixture at a concentration of bioproducti binder--2.07%.

Survival of bacteria colonies were analysed for an increase bioproduct/binder ratio in concretes produced with CEM 1 and CEM III/A based materials, the curing process and the concrete composition adopted were the suitable for an environmental exposure classes XS2 (Permanently submerged elements) used in reinforced concrete (RC) bridges. The results show that there is an improvement of mechanical properties associate with service life of concrete. A decrease in the open porosity was observed and a 40% decrease in the water absorption by capillary for CEMIII/A concrete with bioproduct in comparison to Ordinary Portland Concrete made with CEMI, for a bioproduct/ cement ratio tested up to 2.07%. The chloride migration coefficient reduces 30% for CEMIII/A with bioproduct and 25% for CEMI with bioproduct. This highlights the potential of microbially induced iron-oxide precipitation to work as a corrosion inhibitor, by increasing RC service life. The development of this bioproduct is not energy intensive, which is an advantage in comparison with the existing inorganic inhibitors, which have a huge environmental impact because they contain heavy metals. The compositions of the present invention highlight the potential of microbially induced iron-oxide precipitation (MIIP), to work as a corrosion inhibitor, thereby increasing RC service life. The present invention takes advantage of iron oxide and MIIP leading to self-healing bioconcretes with higher strength and durability.

EXAMPLE 1

The concrete compositions of the present invention generally include cement, aggregate, and water. The cement is present in the fluid concrete mixture in an amount between about 5% to about 20% by weight based on the total weight of the concrete mixture. Aggregates can include, but are not limited to, natural and crushed quarried aggregate, sand, recycled concrete aggregate; blended agro-industry ashes, and the like, as well as mixtures thereof Aggregate is present in the fluid concrete mixture in an amount around 50% by weight; based on the total weight of the concrete mixture.

The fluid concrete mixture also includes water, in an amount ranging from about 2% to about 10% by weight based on the total weight of the mixture The fluid concrete mixture also can include other materials as known in the art for imparting various properties to concrete, including, but not limited to, air--entraining admixtures, water reducing admixtures, accelerating admixtures, pozzolans, such as, but not limited to, fly ash; metakaolin, and silica fume, and the like. These agents can be present in conventional amounts.

Although reference has been made to the components of concrete, it will be appreciated that the present invention also includes mortar compositions, which generally are similar in composition to concrete, except that mortar is typically made with sand as the sole aggregate, in contrast to concrete which includes larger aggregates. Sand in this sense is aggregate of 3/8 inch and smaller diameter.

The present vention will be further illustrated by the following non-limiting examples.

The present application describes a concrete comprising, by mass per cubic meter of concrete, the following components: * 180 to 450 kg / m3 of normal Portland cement CEMII 52.5 N; O 0 to 300 kg / rn3 of ground granulated blast furnace slag [GGBS]; ® 700 to 1000 kg / m3 of course aggregate 20mm; * 600 to 700 kg el rn3 of course aggregate 10mm; * 250 to 400 kg / m3 of limestone sand; * 0 to 4.5 kg I M3 of a superplasticizer; ® 0.1 to 4 kg / m3 of a bioproduct containing iron-respiring bacteria These' alues equate to the percentages quoted hereinbefore.

EXAMPLE 2

Preliminary research was conducted with S. oneidensis strain MR-1 (ATCC 700550), from which the bioproduct of the present invention is based. This bacterium is Biosafety Level 1, environmentally innocuous, and rarely pathogenic.

Initially, 0.1rnl of bacterial culture was taken in a sealed vial and diluted by adding 9.9m1 of sterilized growth media named maximum recovery diluent (MRD). From this diluted cell culture, 10 times dilution was made, then from each diluted flask; 100plwas taken by pipette and spread on agar plates by using spreader under the biologically safety cabinet. The plates were then placed in a laboratory static incubator at 30°C for 24 hours. The concentration of viable microbial organism (S. oneidensis MR-1) was assessed from an agar plate, and thus, the concentration was 2.3x106 Colony Forming Unit per ml (cfulml), of bioproduct produced meaning a colony final concentration between 104 and 105 (cfu/ml) in the concrete. Agar plates were prepared according to manufacturer's instructions prior to sterilisation at 121° C for 15 minutes.

Tryptic Soy Broth (TSB) is the nutritious medium used to support the growth of a wide variety of microorganisms, especially common aerobic. The liquid medium recommended for use in qualitative procedures for isolation and cultivation of a wide variety of microorganisms.

Hence, the medium was prepared according to manufactu instructions prior to sterilisation at 121° C for 15 minutes.

Regarding the sub-culturing and growth conditions of S. oneidensis, initially, the colonies were collected from the incubated plates for the serial dilution of original S, oneidensis strain culture (0.1in1) and kept in sealed vials containing sterile 9.9 ml MR D. Through carrying that process, very high concentrated S. oneiciensi inoculurn was achieved and stored in the freezer. The bacteria were defrosted when they were required for cultivation in order to be mixed with concrete.

The cells of S. oneidensis were grown from high concentrated inoculum once again. A 500m1 of TSB sterilized in four conical flasks each one was containing 125m1, then 400p1 of high concentrated S. oneidensis inoculum were added to individual flasks by pipette. Then the flasks were incubated for three days at 300C, at 150rpm. Through the serial dilution, the growth measurement of the new culture was checked and the concentration measured was 1.7 x106 cfulmi. Therefore, the new culture was found to be more concentrated than the original culture.

Additionally, the second 500m1 of S. oneidensis cells were grown again from the same inoculum as described above. More concentrated S. oneidensis cells were obtained (8 x109). Another 500m1 of S. oneidensis cells were grown from different inoculum temperature 30°C and speed 200rpm. At this time, bigger flasks were placed in Benchtop Shaking incubator for almost 19 hours, from that the best concentration of S. oneidensis was achieved 1 k 101°. Therefore, to control the concentration, it is preferred to use the same procedure each time and, while the flasks are placed in the Benchtop Shaking Incubator, it is recommended to check the concentration of the bacteria by measuring the optical density.

EXAMPLE 3

road concrete, concrete takes up most of the compressive forces of the structure, while reinforcing iron bars (rebars) take up most of the tensile forces Compressive strength of concrete is one of its most important and useful properties. As a construction material, concrete is employed to resist compressive stresses, accordingly the compressive strength of various concrete types of the present invention was tested. Figure 2 shows the results obtained for concretes type CEMI (where no ground granulated blast furnace GOBS was used) and type CEMIII (where 60% of GOBS was mixed to cement type CEM I). Self-healing behaviour was provided by addition of the bioproduct and therefore, two new concrete compositions were created: CEMI + BIO and CEMIII + RIO. This nomenclature will be adhered to throughout the description of the "Examples. Figure 2 shows the average compressive strength results for concrete types CEMI and CEMIII both with and without bioproduct at 28 days. Data shows that the self-healing behaviour in concrete type CEM111+810 surprisingly enhances the compressive strength in comparison to CEMIII without the bioproduct, whereas addition of the bioproduct decreases the compressive strength of concrete made with CEMI by about 5%.

EXAMPLE 4

Water absorption via capillary for concretes CEMI, CEMI + BIG, CEMI II and CEMIII + 810 was tested at 28 days and for 2 weeks. Fiaure. 3 shows that water absorption via capillary tends to reduce by at least 25% if self-healing behaviour is introduced in concrete type CEMIII (CEMI11+1310). In contrast, the self-healing behaviour does not change the maximum water absorbed by the concrete CEMI mix. When considering the durability of reinforced concrete and the service life it may provide: the consideration of long-term water absorption and initial absorption velocity is imperative. Figure 4 shows the results of water absorption via capillary during the first 24 hrs. It is then shown that there is a decrease in the water absorption velocity if self-healing is used in CEM I and CEMli I concretes, which is associated with pores sealing.

EXAMPLE 5

The performance of concrete was quantified in terms of durability, as regards corrosion of steel reinforcement, with and without the presence of self-healing behaviour. The chloride migration coefficient for each concrete composition was determined by the NT BUILD 492 method and is a measure of the resistance of the tested material to chloride penetration.

The experimental procedure for the determination of the coefficient of migration followed the rapid non-steady state chloride test (NT Build 492, 1999), which included cylindrical specimens with 100 mm diameter and 50 mm of thickness. The specimens were subjected to 14 days of drying at 20°C and 50% of RH before being in a low pressure hermetic recipient and immersed in a solution of calcium hydroxide for vacuum treatment. Figure 5 shows chloride migration results for concrete type CEMI and CEMIII with and without bio-product during the first 200 days. A decrease in the migration rate is associated with an increase of the Reinforced Concrete (RC) service life. The previous results demonstrate that there is a reduction of the chloride migration coefficient if self-healing behaviour (BIG) is introduced in the concrete. The age effect shows that the chloride migration coefficient can reduce 30% for CEMI with BIO and 50% for CEMIII with BIO, which substantially increase the RC service life. Figure 6 shows the ratio of non-steady-state migration coefficient in comparison to the references (CEMI and CEMIII at 28 days).

EXAMPLE

Analysis of the microstructure via a SEM at 28 days for CEMIII without bioproduct (Figure 6A) and GEM III + BlO (Figure 6B) was undertaken. No precipitation was observed in the control samples. However, a clear precipitation was found on the cracks remediated in the samples containing the bacterial cells. On closer observation, it was found that the crystals were well developed especially near the surface of the crack

EXAMPLE 7

Electrical resistivity is well correlated with certain performance characteristics of concrete such as chloride diffusion coefficient, water absorption, and corrosion rate of embedded steel. The technique also shows promise as a quality assurance tool for fresh and hardened concrete. Therefore, surface electrical resistivity of hardened concrete samples was tested. Table 1 below shows the comparison of chloride penetrability levels established for standards based on electrical resistivity (AASHTOTP 95) and charged passed (ASTM C1202).

Table 1

: .. : ..

poots..0H 113:T 1202 tecttitotralisli 4 000 2,000-4.000 21-37 1,000-2,000 37-254 100-1,000 /[ 2 ¢ 10 Figure 8 shows the surface electrical resistivity of hardened concrete samples CEM Ill with and without self-healing behaviour (Figure 8A) and GEM! with and without self-healing behaviour (Figure 8B), tested from 28 days until 115 days. Results show that self-healing concrete tends to increase the electrical resistivity, contributing to a decrease of the chloride ion penetrability in the concrete, thus decreasing the corrosion risk. 120 days after concrete samples were produced, the samples were exposed to electrical current injection in the rebars to accelerate corrosion (called the "propagation test"), superficial electrical resistivity was measured during this entire test. in order to confirm that corrosion is happening, the pH evolution of the concrete samples was tested from 0 days for the control samples (CEMI and CEMIII) (fresh state) until 116 days. the concrete samples pH was around 12-13, meaning that the concrete was not exposed to any external influences, which avoids corrosion. During aging, the concrete tends to reduce the pH to values between10-11. During the test with injection of electrical current in the concrete samples (termed the propagation test), the pH was monitored, showing values around 10-11 for all the samples until the end of the test, meaning that corrosion is indeed happening If none of the samples are exposed to electrical current injected in the rebars, the surface electrical resistivity of the hardened concrete samples tends to increase with time and with the introduction of self-healing behaviour in the samples. Moreover. CEMIII+810 and CEMIll are significantly better in comparison to either CEMI types as can be seen in Figure 9, Concrete surface electrical resistivity decreased for all the concretes when injected current was used in the samples. In fact, after 24h of electrical current injection, CEMI types decrease from 12 to 6 kOhm.cm and CEMIII types decreased from 70 to 35 kOhm.cm, meaning that all the compositions are more exposed to chloride ion penetrability in the concrete during the 'propagation test'. However, it is observed that the self-healing behaviour does not decrease the resistivity.

EXAMPLE 8

Electrical current was injected in the concrete samples during a 14 day period. The results (Figure 10) show that the number and size of cracks was substantially larger in concrete OEM I than in OEM III +BIO, meaning that corrosion resistance increases if self-healing behaviour is introduced in the concrete composition. Figure 10 shows images of cement types after the propagation test, Figure 10A shows CEMI without bioproduct. Figure 10B shows CEMI with bioproduct, Figure 100 shows CEMIII without bioproduct and Figure 10D shows CEMIII with bioproduct. Substantial cracks, size (0.4mm) after 11 days were observed in the concrete CEMI without the bioproduct The final diameter of the rebars inside each of the concrete samples, exposed to the 'propagation test', decreased due to corrosion. However, the decrease in CEMIII +BIO seems to be 10x lower than the decrease observed for concrete without the bioproduct and when compared with CEMI+BIO.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS1. A bioproduct comprising at least one strain of Shewanella for use in preventing and/or repairing corrosion in concrete.
2. A bioproduct according to claim 1 wherein the Shewane//a is selected from the group comprising S abyss/, S. aestuarii, S algae, S. algicola, S. algidipiscicola, S. amazonensis, S. aquimarina, S. arctica, S atiantica, S. balfica, S basaltis, S benthica, S. canadensis, S. chilikensis, S. co/we/liana, S. corallii, S. decolorationis, S. denitrificans, S. dokdonensis, S. dongbaensis" S. fidells, S. todinae, S. frigid/marina, S. gaetbull, S. gelidimarina, S. glacialipiscicola, S. gelidit, S. hafniensis, S. hahfaxensis, S. halitois, S. hanedai, S. indica, S. inventionis, S. irciniae, S. japonica, S. kaireitica, S. litofisediminis, S. iivingstonensis, S. loihica, S. mangrovi, S. marina, S. marinintestina, S. marisfiavi, S. =Muse, S. olleyana, S. oneidensis, S. oshoroensis, S. piezotoferans, S. pacifica, S. pealeana, S. piezotolerans, S. pneumatophor, S. profunda, S. psychrophila, S. putrefaciens, S. sairae, S. soilage/lanai S. sediminis, S. seohaensis, S. spongiae, S. surugensis, S. upenei, S. vesicuiosa, S. violacea, S. waksmanii, S. woody/ and S. xiamenensis.
3. A bioproduct according to either claim 1 or2 wherein the at least one ain of Shewanella is S. oneidensis.
4. A bioproduct according to any preceding claims further comprising at least one other bacterial species/strain that is non-pathogenic or substantially non-pathogenic.
5. A bioproduct according to claim 4 wherein the at least one other bacteria species/strain is selected from the group comprising Streptomyces, Nocardia, Micromonospora, Arthrobacter, Chromobactedum, Pseudomonas, Escherichia coil, Salmonella typhimurium. Geohacter, F?aoultella terrigena, Staphylococcus spp.; Eschenchia coli and Salmonella.
6. A bioproduct according to any preceding claim wherein the bioproduct is fluidic and is the form of a liquid, solution, powder, residue, gel, granule, particulate, pellet, microsphere or the like.
7. A bioproduct according to any preceding claim wherein the Shewanelia bacteria are uncapsulated.
8. A bioproduct according to any preceding claims wherein the concentration of Shewanella is between 1 x 108 and 1 x 109 colony forming units per ml (cfu/ml).
9. A biocement, having mixed or embedded therein, a bioproduct comprising at least one Shewane/la strain, the cement being for use in preventing and/or repairing corrosion in concrete.
10. The biocement of claim 9 wherein the proportion of bioproduct in the biocement is in the range of 0.01 to 15% of biocement (by weight).
11. The biocement of either claims 9 or 10 further comprising any one or more of the features recited in claims 2 to 8.
12. A method of manufacturing a biocement comprising a bioproduct, the method comprising providing a cement base including mixed or embedded therein, a proportion of biproduct the bioproduct comprising at least one strain of Shevvan&Ia bacterium, the bacterium being added when in its dormant state.
The method according to claim 12 wherein the cement is a self-healing cement.
14. The method according to either of claims 12 or 13 wherein proportion of bioproduct in the biocement is in the range of 0.01 to 15% of bioce,men, (by weight).
15, A self-healing bioconcrete comprising: (I) cement having mixed or embedded therein, a bioproduct core prising at least one strain of Shewaneita; (ii) water; and (iii) an aggregate of sand and/or aggregate.
16. A self-healing bioconcrete according to claim 15 comprising iron in the form of rods, bars, rebars, mesh, filings or powder.
17. A self-healing bioconcrete according o any either claims 15 and 16 further ncludina any one of claims 2 to 8.
18. A sell-healing biococrete according to any of claims 15 to 17 wherein the bioconcrete comprises the following components in the following ranges: * 0,10 to 0.16 % / m3 of normal Portland cement CEMI 52.5 N; * 0.01 to 0.10 % / m3 of ground granulated blast furnace slag [GGIBS]; ^ 0.35 to 0.40 % / rn3 of course aggregate 20mm; * 0.24 to 0.35 / m3 of course aggregate 10mm; * 0.13 to 0.15 % / rri3 of limestone sand; * 0.0001 to 0.0015 %/ m3 of a bioproduct containing at ieast one Shewanella strain of bacteria.
19. A self-healing bioconcrete further comprising a superplasticizer in the region of up to 0.002 %! n-13 of a superplasticizer.