JP7036315B2 - Geopolymer for crack repair or cross-section repair of concrete - Google Patents

Description

The present invention relates to a geopolymer for repairing cracks or repairing cross sections of concrete.

Currently, the commonly used materials for crack repair and cross-section repair of concrete are either polymer cement or epoxy resin. However, repair materials containing organic compounds with low fire resistance have problems with their physical properties during thermal heat. Epoxy resin is often used as an adhesive or a crack injection material, but it has poor weather resistance and is not the same quality as concrete in terms of tensile strength, coefficient of thermal expansion, and elastic modulus. Differences from the existing part will occur. Further, the polymer cement is inferior in acid resistance and fire resistance because Ca (OH) ₂ crystals and CSH gel are present in the polymer cement as hydrated products of the cement.

On the other hand, the geopolymer is an inorganic material in which a mixture of an active filler containing soluble silicon and aluminum and an alkaline solution containing an alkaline activator that activates the active filler is cured by a polycondensation reaction. As the active filler, blast furnace slag powder and fly ash are often used, and as the alkaline solution, a water glass aqueous solution or a mixed aqueous solution of water glass and caustic soda is usually used. As described above, geopolymers are attracting attention as materials having a small environmental load because they do not use cement and use industrial wastes and by-products as main raw materials. Since geopolymer has faster condensation / hardening and strength development than Portland cement, it has a short curing period, good adhesion to existing concrete and reinforcing bars, and crystalline cement hydrated products such as Ca (OH) ₂ . Since it is not contained, it has excellent fire resistance and acid resistance. Therefore, it is expected that geopolymers will be used in environments where acid is generated such as sewerage-related facilities and in high temperature environments such as steelworks.

By the way, in order to produce a geopolymer having a compressive strength of 30 MPa or more in a room temperature environment of 40 ° C. or lower, it is necessary to use the blast furnace slag powder alone as the active filler or to mix and use it with other active fillers. However, when, for example, 30% by mass of blast furnace slag powder of JIS4000 grade or higher is used in the active filler, the geopolyomer condenses quickly and the pot life is 40 minutes or less. Considering that the fluidity of the geopolyomer decreases with time, the pot life (possible injection time) is 20 minutes or less when it is used as an injection material for repairing cracks in concrete or repairing a cross section. As described above, geopolymers using blast furnace slag powder have excellent strength development even in a room temperature environment, but there is a problem that the pot life is short when applied to the injection method and filling method for repairing cracks in concrete and repairing cross sections. be. If the powderiness of the blast furnace slag powder is lowered, the pot life will be slightly longer, but it will be difficult to inject into fine cracks.

Therefore, as a technique for extending the pot life of a geopolymer, a technique for adding a delaying agent for a geopolymer containing sodium tartrate as a main component is known (Non-Patent Document 1). However, this retarder can be applied only to a geopolymer in which fly ash and blast furnace slag powder are used in combination as an active filler, and the strength after normal temperature curing when added is lower than that without addition. If the liquid-solidity ratio is increased in order to ensure the injectability and filling property into cracks and defects, it is difficult to obtain a crack repair geopolymer having a compressive strength of 45 MPa or more after curing in a normal temperature environment. be.

On the other hand, Non-Patent Document 2 proposes a mixed aqueous solution of liquid glass (aqueous solution of a siliceous coating agent) and caustic soda as a novel alkaline solution. When this mixed aqueous solution of liquid glass and caustic soda is used, the pot life is longer than when the conventional mixed aqueous solution of water glass and caustic soda is used, but as mentioned above, the fluidity of the geopolyomer decreases with time. Considering this, when used as an injection material for repairing cracks, the potable time (possible injection time) is 20 minutes or less. Moreover, since the liquid-solidity ratio is as high as 0.7 to ensure injection into cracks, the compressive strength after curing in a room temperature environment can exceed 45 MPa, but 60 MPa or more (high strength for civil engineering). It is difficult to obtain a geopolymer for crack repair, which is equivalent to concrete).

Tomohisa Okada, Akira Suga, Susumu Hashizume, Kuni Lee: Research on Condensation Delaying Agents Applied to Geopolymers, Annual Proceedings of Concrete Engineering, Vol. 37, No. 1,205,pp. 2295-2300 Tatsuya Kitada, Kuni Lee: Research on Geopolymer-based crack repair materials for concrete, Annual Proceedings of Concrete Engineering, Vol. 39, No. 1,2017, pp. 1975-1980

The problem to be solved by the present invention is to provide a new geopolymer capable of ensuring high injectability and filling property, appropriate pot life and excellent strength development at room temperature for crack repair and cross-section repair. To do.

As a result of various tests on active fillers by the present inventors in order to solve this problem, by using pearlite powder mixed with blast furnace slag powder, high injectability, appropriate pot life and appropriate pot life for crack repair are achieved. It was found that both excellent strength development at room temperature can be ensured.

That is, according to one aspect of the present invention, it is a geopolymer for repairing cracks in concrete or repairing a cross section, which is a mixture of an alkaline solution and an active filler containing pearlite powder and blast furnace slag powder. Geopolymers for repairing cracks in concrete or repairing cross sections are provided, which have a mass ratio of pearlite powder to powder: blast furnace slag powder = 80:20 to 50:50 and a liquid-solidity ratio of 0.4 to 0.7 .
Further, according to another aspect of the present invention, there is provided a geopolymer mortar for repairing a cross section of concrete, which is obtained by adding a fine aggregate to the geopolymer for repairing cracks or repairing a cross section of the concrete of the present invention.

According to the present invention, by using pearlite powder mixed with blast furnace slag powder as an active filler, it is excellent at room temperature while ensuring high injectability / filling property and appropriate pot life for crack repair and cross-section repair. The strength development can be ensured, and for example, it is possible to realize a compressive strength of room temperature curing of 60 MPa or more.

The figure which shows the pot life of a geopolymer slurry (GPS). The figure which shows the result of the viscosity test of GPS. The figure which shows the flow time of GPS. A photograph showing the results of a GPS table flow test and changes over time. The figure which shows the water retention coefficient of GPS. The figure which shows the compressive strength of a GPS hardened body. The figure which shows the adhesive strength of the material age 28 days of GPS. The figure which shows the mass change rate after soaking in a sulfuric acid solution of a GPS hardened body. A photograph showing the deterioration state of a GPS cured product after being immersed in a sulfuric acid solution. The figure which shows the length change rate of a GPS hardened body.

The geopolymer for repairing cracks or repairing cross sections of concrete of the present invention is a mixture of an alkaline solution and an active filler containing pearlite powder and blast furnace slag powder. The mechanism is not clear, but by using pearlite powder mixed with blast furnace slag powder as an active filler, high injectability and filling property for crack repair and cross-section repair, appropriate pot life and strength development at room temperature are exhibited. Both sex can be secured. From the viewpoint of fully exerting the effect of the present invention, the mass ratio of pearlite powder to blast furnace slag powder is preferably pearlite powder: blast furnace slag powder = 80:20 to 50:50, and pearlite powder: blast furnace slag. It is more preferable that the powder = 80:20 to 60:40.
Further, in the present invention, other fillers can be used in combination in addition to the pearlite powder and the blast furnace slag powder. For example, a part of the blast furnace slag powder can be replaced (replaced) with one or more of metakaolin, fly ash, coal ash, sewage sludge / municipal waste incineration ash molten slag powder, and crushed stone powder.

The alkaline solution is not particularly limited, and a water glass aqueous solution generally used for geopolymers or a mixed aqueous solution of water glass and caustic soda may be used, but the fluidity (injectability) for repairing cracks is considered. Then, it is preferable to use an aqueous solution (lithium water glass) containing lithium silicate (Li _2O · nSiO ₂ ) and sodium hydroxide (NaOH), which has a lower viscosity than the aqueous glass aqueous solution or the mixed aqueous solution of water glass and caustic soda. ..

The liquid-solidification ratio (alkaline solution / active filler) is preferably 0.4 to 0.7. This is because if the liquid-solidity ratio is less than 0.4, kneading becomes difficult, and if it exceeds 0.7, bleeding tends to occur.

Furthermore, the geopolymer mortar for repairing a cross section of concrete of the present invention is obtained by adding a fine aggregate to the geopolymer for repairing cracks or repairing a cross section of concrete of the present invention. The fine aggregate to be added is not particularly limited, and JIS standard fine aggregate, artificial lightweight fine aggregate, slag fine aggregate and the like can be added.

This geopolymer mortar has lower cost and drying shrinkage than the above-mentioned geopolymer for repairing cracks or repairing cross sections (geopolymer slurry), and its rigidity after curing is close to that of the concrete to be repaired.
The addition rate of the fine aggregate is the mass ratio of the active filler to the fine aggregate, and the active filler: fine aggregate = 1: 1 to 4 can be set, and the active filler: fine aggregate = 1: 2 to 3 Is preferable.

The production of this geopolymer mortar can be carried out by the method of a conventional cement mortar. That is, a method of mixing the active filler and the alkaline solution, then adding the fine aggregate and further kneading, or a method of mixing the active filler and the fine aggregate and then adding the alkaline solution and further kneading. However, the former method is preferable.

Various types of crack repair or cross-section repair geopolymers (geopolymer slurries) were prepared by the following tests, and their performance was evaluated.

1. 1. Outline of the test 1.1 Materials used Table 1 shows the materials used for the geopolymer slurry (GPS) in this test. As an alkaline solution (AS), any one or more of a water glass aqueous solution (WG), a 10 M caustic soda aqueous solution (NH), a liquid glass (S), and lithium silicate (Li) were mixed at a predetermined volume ratio. I used the one. WG was prepared by preparing JISK1408 No. 1 water glass and water in a volume ratio of 1: 1. For Li, a commercially available undiluted solution was used. Further, as a new alkaline solution, NH and S were mixed at a predetermined volume ratio and used for some series. S was a mixture of the undiluted solution of S and water in a volume ratio of 1: 2. The component of this S is unknown because it is a trade secret.
As the active filler, blast furnace slag powder JIS A6206 class I (BFS8) or class 6000 (BFS6) is mainly used, and for some formulations, fly ash JIS A6201 class I (FA) or pearlite powder (P) is used. ) Was mixed. The chemical composition of the active filler is shown in Table 2.
In order to improve the performance of GPS for repairing cracks, a retarder (R) containing L-sodium tartrate as a main component and an ether-based shrinkage reducing agent (see Non-Patent Document 1) in some formulations (see Non-Patent Document 1 above). SR) (see Reference 1 below) was added as an admixture.
Reference 1 Tomohisa Okada, Kuni Lee, Susumu Hashizume, Tomohide Nagai: Study on the effect of shrinkage reducing agent on the performance of geopolymer concrete using fly ash and blast furnace slag fine powder, Annual Proceedings of Concrete Engineering, Vol. 39, No. 1,2017, pp. 2029-2034

1.2 GPS formulation Table 3 shows the GPS formulation prepared in this test. The test was carried out separately for C, W, S, and P types by changing the type of the active filler (AF), the composition of the alkaline solution (AS), and the presence or absence of the admixture.
In the C type formulation, BFS8 was used alone or in combination with FA, and either NH and WG or a mixed aqueous solution thereof was used as an alkaline solution.
In the W type, BFS and FA are used in combination, a mixed aqueous solution of NH and WG is used, and R or R and SR are added.
As a feature of the S type formulation, a mixed solution of S and NH was used as an alkaline solution.
In these C, W, and S types, the liquid-solidification ratio was set to 0.7 or 0.75 in order to ensure the fluidity and injectability of GPS.
In the P-type formulation, BFS8 and P were mixed at a predetermined ratio, and a mixed aqueous solution of Li and NH was used as an alkaline solution. The liquid-solidification ratio was 0.5 or 0.6.

1.3 Test items and methods The materials used were weighed according to the formulation shown in Table 3, and the active filler and alkaline solution were added to a paste mixer and mixed for 2 minutes to obtain GPS. When the active filler and the alkaline solution were composed of two kinds of materials, the alkaline solution and the active filler were mixed in advance and then kneaded. The active filler was mixed with a paste mixer. When the admixture was added, the admixture was dissolved in an alkaline solution and then mixed with the active filler. The fresh properties of GPS obtained immediately after kneading were measured, and a test piece for a performance test after curing was prepared.

(1) Possibility time Since the method for measuring the pot life has not been established yet, in this test, the sample surface was pierced with a laboratory microspartel under the condition of room temperature of 20 ± 3 ° C, and the liquid entered the indentation. The time until the indentation remained clearly was measured, and the elapsed time from the addition of the alkaline solution was taken as the pot life. Other than this pot life, the following performance tests were mainly performed on W, S, and P types.

(2) Viscosity and fluidity test Immediately after kneading, the viscosity was measured with a B-type viscometer under the condition of room temperature of 20 ± 3 ° C. In addition, the flow time was measured using a J-roat having a capacity of 630 mL, a discharge diameter of φ14 mm, an upper end diameter of φ70 mm, and a height of 395 mm according to the consistency test method of PC grout of the Japan Society of Civil Engineers.

(3) Water retention coefficient The water retention coefficient was measured according to the water retention test method (NSKS-003: repair injection polymer cement slurry) of the Japan Building Finishing Materials Industry Association. The smaller the water retention coefficient, the better the water retention.

(4) Strength test A test piece was prepared and cured according to JIS A1171 (test method for polymer cement mortar), and the compressive strength was measured at the age of 28 days. The dimensions of the test piece were 40 × 40 × 160 mm. The test piece was prepared and cured by pouring GPS into a mold, removing the mold at the age of 1 day, sealing with a wrap to prevent cracking due to drying shrinkage, and curing in a room at 20 ± 3 ° C.

(5) Acid resistance test In accordance with JIS draft (chemical resistance test method by immersing concrete in solution), a columnar test piece having a diameter of 5 cm and a height of 10 cm was prepared, and the temperature was 20 ° C. H. 60% curing was performed for 28 days. Then, it was immersed in sulfuric acid having a concentration of 5%, the mass change rate was measured every 7 days, and the deterioration state of the surface was observed and recorded. When measuring the mass change, the test piece was washed with water and then the surface was wiped with a cloth for measurement.

(6) Adhesive strength test A test piece was prepared and cured according to the method A of the epoxy resin for building repair and building reinforcement of JIS A6024: 2015, and the adhesive strength was measured at the age of 28 days. The thickness of the adhesive layer was set to 3 mm.

(7) Length change (shrinkage) test A columnar test piece with a diameter of 5 cm and a height of 10 cm was subjected to R.I. H. It was made in a 60% room and demolded after 2 days. When this test piece was manufactured, an embedded gauge having a length of 50 mm was embedded in the center of the test piece in the long axis direction, and the rate of change in length was measured immediately after the test piece was manufactured.

2 Test results 2.1 Potability time Figure 1 shows the GPS potability time by type.
In the C type, when only BFS was used as the active filler, the pot life was almost the same regardless of the type of alkaline solution, and the pot life was 20 minutes or less. On the other hand, when FA and BFS were used in combination, it was found that the alkaline solution had a longer pot life in the order of NH, WG, and NH + WG. However, even with NH + WG, the pot life was 45 minutes or less. Considering the change in fluidity over time, it is difficult to inject and fill cracks and defects.

In the W type, R was added in order to extend the usable time of GPS using BFS8 or BFS6 and FA to 60 minutes or more. The pot life of GPS (W8) using BFS8 without adding R is about 45 minutes, and the pot life of GPS (W6) using BFS6 is about 50 minutes. The pot life was about 60 minutes for the series and over 80 minutes for the W6 series. That is, the pot life of GPS can be extended by adding R. On the other hand, the addition of SR to reduce drying shrinkage did not show any effect on the GPS pot life.

In the S type using a mixed aqueous solution of S and NH as an alkaline solution, a pot life of more than 60 minutes could be obtained regardless of whether BFS8 or BFS6 was used, and BFS6 was used as in the W type. The pot life when used was longer than when BFS8 was used, and the addition of SR did not affect the pot life.

In the P type in which P and BFS were used in combination as the active filler, a pot life of 40 minutes or more was obtained without adding R and without using S as an alkaline solution as in the S type. As for the pot life of this P type GPS, the larger the ratio of P, the longer the pot life, and the pot life of 50 minutes or more was obtained by the formulation with P set to 70%. That is, it was confirmed that the pot life can be extended without using R or S by using P and BFS together.

2.2 Viscosity Figure 2 shows the results of viscosity tests for W, S, and P type GPS.
As shown in the figure, in the W type and the S type, the use of BFS6 gave a smaller viscosity than the use of BFS8. In addition, the viscosity of the S type tended to be higher than that of the W type. This is because the liquid-solidification ratio of S type is small. The addition of SR slightly reduced the viscosity of the S type, but no effect on the W type was observed.
The viscosity of the W type GPS was about 2000 mPa · s when BFS8 was used and about 1500 mPa · s when BFS6 was used. On the other hand, in the case of the S type, the viscosity of GPS using BFS8 was about 3100 mPa · s, and that using BFS6 was about 2500 mPa · s.
The viscosity of the P-type GPS tended to increase as the proportion of BFS increased, and was about 3000 mPa · s when 70% of P was mixed. The viscosity when 50% of P was mixed was the highest at about 16000 mPa · s, but it is possible to lower the viscosity by increasing the liquid-solidity ratio or the like. From the results of FIG. 2, the mixing amount of P is preferably 60% or more in order to reduce the viscosity of GPS.

2.3 Flow time Figure 3 shows the flow time of W, S, and P type GPS.
As shown in the figure, the W type using FA, which is a spherical particle, has a large liquid-solidification ratio, but shows a flow time equivalent to that of the S type. In addition, no significant change was confirmed in the flow time of W type and S type GPS due to the addition of R and SR. However, the GPS flow time tended to differ depending on the specific surface area of the BFS used. That is, it took about 20 seconds when BFS8 was used, but it was about 8 seconds when BFS6 was used, which was significantly reduced.
As for P-type GPS, the larger the proportion of BFS, the longer the flow time tends to be, as with the viscosity. It took about 15 seconds when 70% of P was mixed. The flow-down time when 50% of P was mixed was the longest at about 125 seconds, but it is possible to shorten the flow-down time by increasing the liquid-solidification ratio or the like. From the results of FIG. 3, the mixing amount of P is preferably 60% or more.

2.4 Changes in fluidity over time FIG. 4 shows the results of GPS table flow tests for S type (S8) and P type (P70) and changes over time.
As shown in the figure, the fluidity of the S-type GPS tended to decrease significantly with the elapsed time. If the fluidity drops significantly without coagulation, it cannot be injected into the crack. That is, it was determined that the injectable time of the S type GPS was only about 20 minutes.
On the other hand, the fluidity of the P-type GPS was maintained up to 45 minutes, and the decrease with time was small. That is, in the case of P type, it was confirmed that the injectable time could be extended to about 45 minutes.

2.5 Water retention coefficient Figure 5 shows the effects of admixtures and BFS types on the GPS water retention coefficient.
The water retention coefficient of the S type and P type GPS was larger than that of the W type, but both were 30% or less, and there was no problem in water retention.

2.6 Strength Figure 6 (a) shows the compressive strength of the W type GPS cured product.
The compressive strength was the highest when no admixture was used, and the compressive strength at 28 days of age was about 40 N / mm ² . However, the addition of the admixture showed a decrease in strength. In particular, when both R and SR were added, the decrease in compressive strength was large, and the compressive strength at 28 days of age was 30 N / mm ² or less. Further, even when only R was added and BFS8 was used, the compressive strength was 40 N / mm ² or less.
FIG. 6B shows the compressive strength of the S-type GPS cured product.
When SR was added, the compressive strength at 28 days of age exceeded 36 N / mm ² , but was 45 N / mm ² or less, regardless of the BFS class.
FIG. 6C shows the compressive strength of the P-type GPS cured product.
The larger the proportion of BFS, the greater the compressive strength. Further, the compressive strength of the P type was larger than that of the W type and the S type, and even if the ratio of BFS was 30%, the compressive strength at the age of 28 days was 70 N / mm ² or more.
As described above, it was confirmed that according to the P type, the strength development at room temperature is improved and a high-strength repair material can be realized.

2.7 Adhesive strength Fig. 7 shows the adhesive strength of W, S, and P type GPS at 28 days of age.
The adhesive strength of the W type GPS was 4.0 N / mm ² or less. For the S type, the adhesive strength exceeded 4.0 N / mm ² due to the addition of SR. On the other hand, in the P type GPS, the adhesive strength exceeded 4.0 N / mm ² without adding SR.
As described above, it was confirmed that the P type can easily realize a high adhesive strength of 4.0 N / mm ² or more.

2.8 Acid resistance Figure 8 shows the mass change rate of W, S, and P type GPS cured products after immersion in sulfuric acid solution.
The mass of the W-type GPS cured product decreased with the increase in the immersion period, and it was confirmed that the mass decreased by about 13% in 4 weeks. Further, as shown in FIG. 9, remarkable damage to the appearance was observed after immersion. On the other hand, the mass of the S-type GPS cured product gradually increased with the increase in the immersion period, and increased by about 7% in 4 weeks. In addition, after 4 weeks, a dimensional increase of about 3 mm in diameter and about 5 mm in height was observed. As shown in FIG. 9, some damage was observed in the appearance after immersion. On the other hand, the mass reduction rate of the P-type GPS cured product after immersion for 4 weeks was as small as 2.8%, and as shown in FIG. 9, there was almost no change in appearance.
As described above, it was confirmed that the P type has excellent acid resistance.

2.9 Change in length (volume) Fig. 10 shows the rate of change in length of W, S, and P type GPS cured products.
There was almost no difference in length change between W type W8RSR and W6RSR, and no influence was observed depending on the type of BFS. On the other hand, in the case of the S type, when the results of S8 and S8SR were compared, it was found that the length change (shrinkage strain) of S8SR was small, and that the addition of SR suppressed the drying shrinkage. Moreover, when comparing S8SR and S6SR, the length change was smaller in S6SR using BFS6. The length change of the P type GPS cured product was larger than that of the W and S types, but the length change rate was 1.5% or less in both cases, and the drying shrinkage rate (3% or less) as a repair material was required. Are satisfied.

3. 3. Summary According to P-type GPS, which uses P and BFS together as an active filler, it can be used as an injection / filling material for crack repair and cross-section repair, while ensuring high injectability, filling property, and appropriate pot life at room temperature. It has excellent strength (compressive strength / adhesive strength) and can secure high acid resistance.

Claims (4)

A geopolymer for repairing cracks in concrete or repairing cross sections, which is made by mixing an alkaline solution with an active filler containing pearlite powder and blast furnace slag powder .
The mass ratio of pearlite powder to blast furnace slag powder is pearlite powder: blast furnace slag powder = 80:20 to 50:50, and the liquid-solidification ratio is 0.4 to 0.7. .. The geopolymer for repairing cracks or repairing cross sections of concrete according to claim 1, wherein the alkaline solution is an aqueous solution containing lithium silicate and sodium hydroxide. The invention according to claim 1 or 2 , wherein a part of the blast furnace slag powder is replaced with one or more of metakaolin, fly ash, coal ash, sewage sludge / municipal waste incineration ash molten slag powder, and crushed stone powder. Geopolymer for repairing cracks in concrete or repairing cross sections. A geopolymer mortar for repairing a cross section of concrete, which is obtained by adding a fine aggregate to the geopolymer for repairing cracks in concrete or repairing a cross section according to any one of claims 1 to 3 .

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