Concrete test piece and method of manufacturing the same

Abstract

To solve the problem that an appropriate evaluation result cannot be obtained when a repair material for repairing deteriorated concrete structures is applied to a new concrete test piece in an attempt to evaluate the repair material.SOLUTION: A concrete test piece to be used to evaluate concrete repair materials is provided, the concrete test piece being made of concrete having an air permeability coefficient of 1×10-16 m2 to 10000×10-16 m2, inclusive, and a water absorption rate of 0.5 ml / m2 / s to 1.5 ml / m2 / s, inclusive.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to concrete specimens and methods for manufacturing concrete specimens. [Background technology]

[0002] Concrete structures are characterized by their relatively low cost, excellent workability, and high strength. Therefore, many concrete structures were constructed in Japan, particularly during the period of rapid economic growth. Concrete structures generally have excellent durability. However, over many years of use, concrete structures can become neutralized due to the penetration of carbon dioxide from the atmosphere along with moisture. Furthermore, in environments where concrete structures are exposed to sea breezes and sprays of antifreeze, chloride ions contained in the sea breezes and sprays of antifreeze can penetrate the concrete structure. This neutralization and chloride ions can cause corrosion and expansion of the internal reinforcing bars in the concrete structure, potentially resulting in cracks in the concrete structure.

[0003] In recent years, methods such as surface coating / impregnation methods, cross-section repair methods, and crack repair methods, as well as repair materials for use in these methods, have been developed for the purpose of repairing deteriorated concrete structures. These methods and repair materials are contributing to the extension of the service life of concrete structures.

[0004] To evaluate and study repair methods and repair materials for concrete structures, a concrete test specimen that is more compact than the in-situ structure is required. Conventional concrete test specimens include the test substrate described in "JSCE-K 511 Weatherability Test Method for Surface Coating Materials" in Non-Patent Document 1, and the "U-shaped gutter with top cover (lid) specified in JIS A 5372" described in "JSCE-K-533 Push-out Test Method for Surface Coating Materials Applied to Prevent Concrete Pieces from Peeling Off." However, neither of these specimens reflects the deterioration state of the in-situ concrete structure.

[0005] Therefore, repair materials developed using conventional concrete test specimens cannot be properly evaluated as repair materials, and there is a risk that their performance will be insufficient. For example, there is a risk of problems such as peeling of the repair material after repairing a concrete structure. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] 2013 Standard Specifications for Concrete (Standards Edition) Standards and Related Standards of the Japan Society of Civil Engineers, edited by the Japan Society of Civil Engineers Concrete Committee Standards Related Subcommittee, published by the Japan Society of Civil Engineers, Maruzen Publishing Co., Ltd. Summary of the Invention [Problem to be solved by the invention]

[0007] Conventional methods for evaluating repair materials for concrete structures have the potential to misjudge the performance of repair materials for concrete structures.

[0008] The present disclosure has been made to solve such problems, and aims to provide a deteriorated concrete test specimen and a manufacturing method thereof for performing an evaluation that reflects the deterioration state of an on-site concrete structure. [Means for solving the problem]

[0009] The concrete test specimen of the first aspect is a concrete test specimen used for evaluating a concrete repair material, It consists of concrete, The air permeability coefficient of the concrete is 1 x 10 -16 m 2 Over 10000 x 10 -16 m 2 is less than or equal to, and The water absorption rate of the concrete is 0.5 ml / m 2 ·s or more 1.5ml / m 2 ·s or less.

[0010] The concrete test specimen of the first aspect reproduces the condition of concrete that has deteriorated over time, and can be suitably used to evaluate repair materials for concrete structures.

[0011] The concrete test specimen of the second aspect is the concrete test specimen of the first aspect, wherein the concrete has a rectangular parallelepiped shape, the thickness of the rectangular parallelepiped is 1 cm or more and 10 cm or less, the vertical length of the rectangular parallelepiped is 4 cm or more and 100 cm or less, and the horizontal length of the rectangular parallelepiped is 4 cm or more and 100 cm or less.

[0012] Unlike concrete structures, the concrete test specimen of the second aspect can be moved and used to evaluate concrete repair materials in an appropriate environment.

[0013] A method for manufacturing a concrete test specimen according to a third aspect is a method for manufacturing a concrete test specimen used in the system according to the first or second aspect to evaluate a concrete repair material, mixing concrete materials to form a concrete slab; The air permeability coefficient of the concrete slab is 1 x 10 -16 m 2 Over 50000 x 10 -16 m 2 The water absorption rate of the concrete slab is 0.5 ml / m or less. 2 ·s or more 1.5ml / m 2 and a step of degrading the material to below s.

[0014] The method for manufacturing a concrete test specimen according to the third aspect makes it possible to manufacture a concrete test specimen that reproduces the condition of concrete that has deteriorated over time, and the concrete test specimen can be suitably used for evaluating repair materials for concrete structures.

[0015] A fourth aspect of the present invention relates to a method for manufacturing a concrete test piece according to the third aspect, wherein the step of deteriorating the concrete slab includes a step of freezing and thawing the concrete slab.

[0016] The method for manufacturing a concrete specimen according to the fourth aspect can bring the concrete slab into a deterioration state similar to that of long-term aged deterioration in a short period of time by freezing and thawing the concrete slab.

[0017] A fifth aspect of the method for manufacturing a concrete test specimen is the fourth aspect of the method for manufacturing a concrete test specimen, in which the step of freezing and thawing the concrete slab is carried out after the step of forming the concrete slab, without first undergoing the step of drying the concrete slab.

[0018] The fifth aspect of the method for manufacturing a concrete test specimen is to freeze-dry the concrete slab after forming it before it dries, thereby making it possible to cause the concrete slab to deteriorate in a short period of time in a state similar to that of long-term aging.

[0019] A method for producing a concrete test piece according to a sixth aspect is the method for producing a concrete test piece according to the fourth or fifth aspect, wherein the step of deteriorating the concrete plate further comprises:

[0020] The method includes a step of drying the concrete slab after the step of freezing and thawing the concrete slab.

[0021] A seventh aspect of the present invention relates to a method for producing a concrete test piece according to the sixth aspect, wherein the step of deteriorating the concrete plate further comprises:

[0022] The method includes a step of performing freezing and thawing the concrete slab again after the step of drying the concrete slab.

[0023] In the method for producing a concrete specimen according to the seventh aspect, the concrete plate is further subjected to freezing and thawing after drying, which can further deteriorate the surface of the concrete plate.

[0024] A method for manufacturing a concrete test piece according to an eighth aspect is the method for manufacturing a concrete test piece according to any one of the third to fifth aspects, wherein the step of deteriorating the concrete plate further comprises: This includes a step of acid washing the concrete slab.

[0025] In the method for producing a concrete test specimen according to the eighth aspect, after the concrete plate is dried, acid washing is further carried out, which can further deteriorate the surface of the concrete plate.

[0026] A ninth aspect of the method for manufacturing a concrete test specimen is a method for manufacturing a concrete test specimen according to any one of the third to fifth aspects, in which the step of forming the concrete plate and the step of deteriorating the concrete are carried out for a period of at least two weeks but not more than five weeks.

[0027] The method for manufacturing a concrete test specimen according to the ninth aspect makes it possible to reproduce in a short period of time the deterioration state of a concrete structure that deteriorates over time, and to appropriately evaluate concrete repair materials. [Effects of the Invention]

[0028] The concrete specimens disclosed herein reproduce the deterioration state of an in-situ concrete structure. Moreover, the deterioration state is controlled within a certain range. Therefore, by using the concrete specimens disclosed herein to evaluate concrete repair methods and repair materials, evaluation results similar to those obtained when applied to in-situ concrete can be obtained.

[0029] Furthermore, the method for manufacturing a concrete specimen according to the present disclosure makes it possible to manufacture such deteriorated concrete specimens in a short period of time. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a diagram showing the appearance of a concrete test specimen according to a first embodiment. [Figure 2] 1 is a flowchart showing a method for manufacturing a concrete test specimen according to the first embodiment. [Figure 3] 1 is a flowchart showing a method for manufacturing a concrete specimen of Example 1. [Figure 4]10 is a flowchart showing a method for manufacturing a concrete specimen of Example 2. [Figure 5] 10 is a flowchart showing a method for manufacturing a concrete specimen of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0031] (1) Concrete test specimen Concrete exposed to the natural environment deteriorates over a long period of time. The concrete specimen of this embodiment can reproduce this deterioration of concrete to some extent and can be used to evaluate repair materials for deteriorated concrete.

[0032] There are various methods for non-destructively inspecting and evaluating the degree of concrete deterioration. Concrete evaluation methods can be divided into methods for evaluating the condition inside the concrete and methods for evaluating the condition on the surface of the concrete. Either method alone is insufficient to reproduce the deterioration condition in the field. It is necessary to match the characteristics of the concrete specimen to the index data obtained by both methods for the field structure.

[0033] The air permeability coefficient is a suitable index for evaluating the internal condition of concrete. One method for determining the air permeability coefficient is the "surface layer air permeability test - double chamber method," which is one of the methods listed in "NDIS 3436-1 Non-destructive testing of concrete" and is relatively less affected by the surface layer.

[0034] The standard air permeability coefficient of a typical sound concrete measured by the double chamber method is 1 x 10 when a concrete structure is newly constructed. -16 m 2 The deterioration of on-site structures over time is estimated to be 1 x 10 -16 m 2 Therefore, the air permeability coefficient required for a concrete specimen that reproduces a deteriorated state is preferably 1 × 10 -16 ~50000×10 -16 m 2 , more preferably 100×10-16 ~10000×10 -16 m 2 is.

[0035] The water absorption coefficient is an index used to evaluate the condition of concrete surfaces. One method for determining the water absorption coefficient is the "Water Penetration Resistance Test - Surface Water Absorption Test Method," which is planned to be established as "NDIS 3440-1 Non-Destructive Testing of Concrete."

[0036] The standard water absorption rate for a typical sound concrete surface water absorption test is 0.5 ml / m when newly constructed. 2 ·s or less. For on-site structures that have deteriorated over time, the 2 Therefore, the air permeability coefficient required for deteriorated concrete specimens is preferably 0.5 to 1.5 ml / m 2 ·s, more preferably 0.75 to 1.2 ml / m 2 ·s.

[0037] The concrete specimen is shaped like a rectangular parallelepiped plate, as shown in Figure 1. The size of the specimen is usually such that the thickness of the plate (height H of the rectangular parallelepiped) is 1 cm to 10 cm, the vertical length of the plate (vertical length L of the rectangular parallelepiped) is 4 cm to 100 cm, and the horizontal length of the plate (horizontal length T of the rectangular parallelepiped) is 4 cm to 100 cm. For example, a relatively small specimen has dimensions of H x L x T of 40 mm x 40 mm x 10 mm, and a relatively large specimen has dimensions of 1 m x 1 m x 10 cm.

[0038] (2) Manufacturing method of concrete test specimens The method for manufacturing a concrete specimen of this embodiment includes a step (S1) of forming a concrete slab and a step (S2) of deteriorating the concrete slab, as shown in Fig. 2. In the step (S2) of deteriorating the concrete slab, the air permeability coefficient of the concrete slab is set to 1 × 10 -16 m 2 Over 50000 x 10 -16 m 2 The water absorption rate of the concrete slab is 0.5 ml / m or less.2 ·s or more 1.5ml / m 2 Degrade to below s.

[0039] (2-1) Step of forming a concrete slab (S1) The materials used in concrete are cement, water, fine aggregate, coarse aggregate, and other admixtures. The mix ratio for each material is shown in Table 1. In concrete mixes, the water-cement ratio is preferably 60% or more, and more preferably 65% ​​or more.

[0040] [Table 1]

[0041] The concrete materials are mixed and kneaded according to the mix ratio. The process up to mixing complies with JIS A1138. The mixed concrete is filled into a formwork and formed into a plate. The concrete filled into the formwork is hardened and cured, and if the hardening and curing process is to be further advanced, it is preferable to prevent it from drying out by, for example, immersing it in water. A long curing period is not desirable, and it is desirable to keep it within 14 days.

[0042] (2-2) Process of deteriorating the concrete slab (S2) The process (S2) of deteriorating the concrete slab includes a process of deteriorating the concrete to the inside (a process of adjusting the air permeability coefficient) and a process of deteriorating the concrete surface layer (a process of adjusting the water absorption rate). If the concrete surface layer has been sufficiently deteriorated by the process of deteriorating the concrete to the inside (a process of adjusting the air permeability coefficient), the process of deteriorating the concrete surface layer (a process of adjusting the water absorption rate) does not need to be performed.

[0043] (2-2-1) Process of deteriorating the concrete to the inside (process of adjusting the air permeability coefficient) The freeze-thaw process is suitable as a process that deteriorates the concrete to its interior.

[0044] It is extremely time-consuming and difficult to recreate concrete that has deteriorated internally over time by deteriorating a completed concrete slab. Therefore, in order to deteriorate the concrete internally (to adjust the air permeability coefficient), the concrete filled into the formwork is damaged by freezing and thawing before it has fully cured and hardened sufficiently.

[0045] The duration of the freeze-thaw step has no particular preferred range and can be adjusted to suit the length of the freeze-thaw cycle.

[0046] The freeze-thaw method is JIS A 1148 "Concrete freeze-thaw test method (underwater freeze-thaw test method: Method A)." Since this will cause deterioration to the interior, it is necessary to prevent drying from the curing period until the freeze-thaw process is complete.

[0047] The number of freeze-thaw cycles is 1 to 100. There is no particularly preferred range, and it can be adjusted according to the length of the curing period. The shorter the curing period, the fewer freeze-thaw cycles required.

[0048] (2-2-2) Deteriorating the concrete surface (adjusting the water absorption rate) In concrete structures, deterioration of the concrete itself progresses from the surface to the interior, excluding the effects of internal factors such as destruction caused by expansion of internal rebar due to neutralization and salt damage. Therefore, the surface layer is often more deteriorated than the interior, and it is important to reproduce the surface condition when creating deteriorated concrete specimens.

[0049] The process of deteriorating the concrete to its interior (process of adjusting the air permeability coefficient) generally also deteriorates the surface layer of the concrete. If the surface layer of the concrete is sufficiently deteriorated by the process of deteriorating the concrete to its interior (process of adjusting the air permeability coefficient) alone, it is sufficient to carry out only the process of deteriorating the concrete to its interior (process of adjusting the air permeability coefficient). If the surface layer of the concrete is not sufficiently deteriorated by the process of deteriorating the concrete to its interior (process of adjusting the air permeability coefficient) alone, the process of deteriorating the surface layer of the concrete (process of adjusting the water absorption rate) is carried out subsequently. Whether or not to carry out the process of deteriorating the surface layer of the concrete (process of adjusting the water absorption rate) is determined by evaluating the water absorption rate of the concrete specimen after the process of deteriorating the concrete to its interior (process of adjusting the air permeability coefficient) is completed. In this embodiment, the water absorption rate is 0.5 ml / m 2 If the value is less than s, it is determined that the degree of deterioration of the surface layer is insufficient, and a process of deteriorating the concrete surface layer (a process of adjusting the water absorption rate) is carried out.

[0050] There are many methods for deteriorating the surface, such as cleaning the surface with acid, or scaling tests such as the ASTM C672 test method or the RILEM CDF test.

[0051] The acid used for the acid washing is not particularly limited, but a general strong acid aqueous solution such as dilute hydrochloric acid or dilute sulfuric acid is suitable.

[0052] The process of deteriorating the concrete surface (process of adjusting the water absorption rate) is performed on test specimens that have undergone the process of deteriorating the concrete to its interior (process of adjusting the air permeability coefficient) and the drying process. If the drying is insufficient, deterioration may progress to the interior at the same time, making it impossible to reproduce the condition in which deterioration progresses from the surface to the interior. The process of deteriorating the concrete surface (process of adjusting the water absorption rate) only degrades the concrete surface, so it does not have much effect on the deterioration of the interior of the concrete. Therefore, by performing the process of deteriorating the concrete surface (process of adjusting the water absorption rate) after the process of deteriorating the concrete to its interior (process of adjusting the air permeability coefficient), it is possible to create deteriorating concrete test specimens in which both the interior and surface of the concrete have been adjusted. [Example]

[0053] The deteriorated concrete specimen and manufacturing method of the present disclosure will be described below using examples.

[0054] Example 1 The method for manufacturing the concrete specimen of Example 1 will be described with reference to the flowchart of FIG.

[0055] Concrete materials with a water-cement ratio of 70% were mixed and kneaded according to the mix ratio in the lower row of Table 1, then poured into a 10 cm x 10 cm x 40 cm formwork and cured for two days to form a concrete slab (Step S11). The formed concrete slab was then demolded, immersed in water, and cured for 14 days (Step S12).

[0056] As a process for deteriorating the concrete to its interior (a process for adjusting the air permeability coefficient), the test specimens after underwater curing were subjected to 90 freeze-thaw cycles while still wet, without any drying period, according to JIS A 1148 "Concrete Freeze-Thaw Test Method (Underwater Freeze-Thaw Test Method: Method A)" ​​(Step S13).The concrete slabs were then dried for 14 days (Step S14).

[0057] The air permeability coefficient of the concrete slab was measured using an air permeability tester manufactured by Materials Advanced Services, which is an air permeability measurement device using the double chamber method. The air permeability coefficient of the concrete slab was 26 × 10 -16 m 2 It was.

[0058] The water absorption rate was measured using the evaluation method planned to be established as "NDIS 3440-2 Non-destructive Testing of Concrete - Moisture Penetration Resistance Test Part 2: Surface Water Absorption Test." The air permeability coefficient of the concrete slab was 0.7 ml / m 2 ·s.

[0059] Example 2 The method for manufacturing the concrete specimen of Example 2 will be described with reference to the flowchart of FIG.

[0060] Concrete materials with a water-cement ratio of 65% were mixed and kneaded according to the mix ratio shown in the top row of Table 1, and then poured into a 10 cm x 10 cm x 40 cm formwork to form a concrete slab (Step S21). Next, as a process for deteriorating the concrete to its interior (a process for adjusting the air permeability coefficient), the concrete slab was frozen in an environment of -20°C for 15 hours without a curing period, and then thawed at room temperature (Step S22). The thawed concrete slab was then removed from the form and dried for 14 days (Step S23).

[0061] The air permeability coefficient of the concrete slab was measured in the same manner as in Example 1. The air permeability coefficient of the concrete slab was 1112 × 10 -16 m 2 It was.

[0062] The water absorption rate of the concrete plate was measured in the same manner as in Example 1. The water absorption rate of the concrete plate was 0.4 ml / m 2 ·s.

[0063] Next, the concrete surface was acid washed as a process to deteriorate the concrete surface (a process to adjust the water absorption rate). 2.5 kg / m of 5% diluted sulfuric acid was applied to the concrete plate with a brush.2 After applying the solution and leaving it for 30 seconds, the surface was washed with water. This process was repeated twice.

[0064] The water absorption rate of the concrete plate after acid washing was measured in the same manner as in Example 1. The water absorption rate of the concrete plate was 1.1 ml / m 2 ·s.

[0065] Example 3 The method for manufacturing the concrete specimen of Example 3 will be described with reference to the flowchart of FIG.

[0066] Steps S31 to S33 in the third embodiment are exactly the same as steps S21 to S23 in the second embodiment.

[0067] The measurement of the air permeability coefficient of the concrete slab and the measurement of the water absorption rate of the concrete slab were also the same as in Example 2.

[0068] The next step of deteriorating the concrete surface layer (the step of adjusting the water absorption rate) is different from that of Example 2.

[0069] The concrete specimens with the adjusted air permeability coefficient of Example 2 were subjected to one cycle of freeze-thawing according to the procedure of the RILEM CDF test, which is one of the scaling tests, as a process for deteriorating the concrete surface layer (a process for adjusting the water absorption rate).

[0070] Thereafter, the water absorption rate of the concrete was measured again in the same manner as in Example 1. The water absorption rate of the concrete was 0.8 ml / m 2 ·s.

[0071] (Comparative Example 1) A test specimen was prepared in the same manner as in Example 1, except that no freeze-thawing was performed. The air permeability coefficient of the concrete test specimen was measured in the same manner as in Example 1, and the value was 0.6 × 10 -16 m 2 The water absorption rate of the concrete specimen was measured in the same manner as in Example 1, and the water absorption rate was 0.1 ml / m 2 ·s.

[0072] (Comparative Example 2) A test specimen was prepared in the same manner as in Comparative Example 1, except that the water-cement ratio was set to 65%. The air permeability coefficient of the concrete test specimen was measured in the same manner as in Example 1, and the value was 0.02 × 10 -16 m 2 The water absorption rate of the concrete specimen was measured in the same manner as in Example 1, and the result was 0.1 ml / m 2 ·s.

[0073] As described above, the concrete specimen disclosed herein reproduces the deterioration state of an in-situ concrete structure by controlling the indexes of the concrete air permeability coefficient and water absorption rate. Therefore, it can be suitably used for evaluating repair materials for deteriorated concrete.

[0074] Furthermore, the method for manufacturing concrete specimens disclosed herein involves freezing and thawing the concrete after mixing and before drying, making it possible to manufacture deteriorated concrete specimens in a short period of time.

[0075] Although multiple embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit and scope of the present disclosure. In particular, multiple embodiments described in this specification can be arbitrarily combined as necessary. [Industrial Applicability]

[0076] The concrete specimen of the present disclosure can be suitably used for evaluating repair materials for deteriorated concrete.

Claims

1. A concrete test specimen used to evaluate concrete repair materials, It consists of concrete, The air permeability coefficient of the concrete is 1 x 10 -16 m 2 Over 10000 x 10 -16 m 2 is less than or equal to: The water absorption rate of the concrete is 0.5 ml / m 2 ・s or more 1.5ml / m 2 ・It is less than or equal to s, Concrete test specimen.

2. The concrete has a rectangular parallelepiped shape, The thickness of the rectangular parallelepiped is 1 cm or more and 10 cm or less, the vertical length of the rectangular parallelepiped is 4 cm or more and 100 cm or less, and the horizontal length of the rectangular parallelepiped is 4 cm or more and 100 cm or less, The concrete specimen according to claim 1.

3. A method for manufacturing a concrete test specimen used to evaluate a concrete repair material, comprising: mixing concrete materials to form a concrete slab; The air permeability coefficient of the concrete slab is 1 x 10 -16 m 2 Over 50000 x 10 -16 m 2 The water absorption rate of the concrete slab is 0.5 ml / m or less. 2 ・s or more 1.5ml / m 2 - Deteriorating the temperature to below s, Method for manufacturing concrete test specimens.

4. The step of deteriorating the concrete slab includes a step of freezing and thawing the concrete slab. The method for manufacturing a concrete test specimen according to claim 3.

5. The step of freezing and thawing the concrete slab is carried out after the step of forming the concrete slab, without a step of drying the concrete slab. The method for manufacturing a concrete test specimen according to claim 4.

6. The step of deteriorating the concrete slab further comprises: After the step of freezing and thawing the concrete slab, a step of drying the concrete slab is included. The method for manufacturing a concrete test specimen according to claim 4 or 5.

7. The step of deteriorating the concrete slab further comprises: The method includes a step of performing freezing and thawing the concrete slab again after the step of drying the concrete slab. The method for manufacturing a concrete test specimen according to claim 6.

8. The process of deteriorating the concrete slab further includes: The process includes acid washing the concrete slab. The method for manufacturing a concrete test specimen according to any one of claims 3 to 5.

9. The step of forming the concrete slab and the step of deteriorating the concrete are carried out for a period of not less than 2 weeks and not more than 5 weeks. The method for manufacturing a concrete test specimen according to any one of claims 3 to 5.

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