JP6585923B2 - Structural members and floor slabs - Google Patents

Description

  The present invention relates to a concrete composition suitable as a material for a structural member on which a repeated load acts, such as a concrete floor slab of a bridge, a molded product formed by molding the same, and a floor slab.

  In coastal areas and areas where anti-freezing agents are sprayed in cold regions, deterioration due to freezing and thawing action is promoted in addition to deterioration due to salt damage, so the deterioration of concrete structures proceeds significantly. In particular, in concrete floor slabs of bridges, there are cases where concrete deteriorates due to sedimentation due to salt and moisture supplied from the bridge surface, loading of repeated loads due to vehicle traffic, and their combined action, Its durability is a problem.

  Remarkably deteriorated floor slabs may cause traffic problems if the deterioration deteriorates, so they can be replaced with highly durable prestressed concrete slabs (hereinafter referred to as PC floor slabs) by repair and replacement work. Since this replacement work requires a large amount of cost, labor, and time, it has been desired to develop a concrete having excellent durability capable of suppressing sedimentation.

  The PC slab is manufactured through steam curing in a precast (hereinafter referred to as PCa) factory or the like in order to introduce prestress and obtain a required expression strength. However, steam curing may cause bubbles introduced into the concrete to escape, resulting in a decrease in freezing resistance. Therefore, there has been concern about deterioration when used in cold regions or salt damage environments.

  On the other hand, in past studies, it is known that concrete containing blast furnace slag fine aggregate and blast furnace slag fine powder is excellent in salt damage resistance and freeze-thaw resistance (see, for example, Patent Documents 1 and 2). .

  Patent Document 1 is a composition for mortar or concrete containing a blast furnace slag fine aggregate and a binder containing a blast furnace slag fine powder and Portland cement, and the content ratio of the blast furnace slag fine aggregate to the total fine aggregate is The mass ratio is 66.7% or more. This mortar or concrete composition uses blast furnace slag fine aggregate as a fine aggregate, so that the mortar or concrete becomes dense and high strength prevents chloride ion penetration. There is the feature that it is excellent.

  Patent document 2 is a composition for mortar or concrete containing fine aggregate, a binder containing cement, and water, and a material made of blast furnace slag is used for at least one of the fine aggregate and the binder. A relative kinematic modulus at 300 freeze-thaw cycles in a freeze-thaw test based on method A described in JIS A 1148 for a mortar or concrete specimen prepared from the mortar or concrete composition is 60% or more, Excellent resistance to frost damage. This composition for mortar or concrete has a feature that it is excellent in resistance to combined deterioration due to frost damage and salt damage by using blast furnace slag as at least one of fine aggregate and binder.

  FIG. 15 shows the results of a freeze-thaw test using 10% salt water for ordinary concrete. Concerning concrete specimens using water cement ratio W / C = 40%, mass ratio GGBF / B = 0% of blast furnace slag fine powder (GGBF) to binder (B), 100% sandstone crushed sand as fine aggregate The curing method and the presence or absence of the addition of the AE agent are changed. This concrete specimen does not contain blast furnace slag. As shown in this figure, ordinary concrete that does not contain blast furnace slag has a relative dynamic elastic modulus of less than 60% at 300 freeze-thaw cycles except for AE concrete (underwater curing), which is inferior in frost damage resistance. Yes.

  On the other hand, FIG. 16 shows the results of a freeze-thaw test using 10% strength salt water for concrete using blast furnace slag fine aggregate. Fine bone using sandstone crushed sand when water cement ratio W / C = 40%, mass ratio GGBF / B = 40% of blast furnace slag fine powder (GGBF) to binder (B), water curing after steam curing The content ratio BFS / S of the blast furnace slag fine aggregate (BFS) to the material (S) is changed. It can be seen that the concrete containing the blast furnace slag fine aggregate has a relative kinematic elasticity coefficient of 60% or more after 300 freeze-thaw cycles and is excellent in frost damage resistance.

  In addition, what is shown by patent document 3, for example is known as another mortar containing the material which consists of blast furnace slag, or a composition for concrete, and a molded article.

Patent Document 3 is a mortar or concrete composition containing an amorphous blast furnace slag fine aggregate, and a binder containing a fine powder of blast furnace slag having a specific surface area of 2500 to 7000 cm ² / g and a Portland cement. The mass ratio of Portland cement to the binder is 0.3 to 0.9. This mortar or concrete composition has a feature of excellent sulfuric acid resistance because a dihydrate gypsum layer is formed on the surface when used in an environment exposed to a sulfuric atmosphere such as a sewerage facility.

JP2013-227185A JP 2014-159354 A Japanese Patent No. 5330895

  By the way, when the present inventor diligently researched the resistance to the combined deterioration of frost damage and fatigue (repeated load loading) of concrete, the composition containing a large amount of blast furnace slag fine aggregate has sufficient resistance. It has been found. That is, it was found that the resistance to frost damage and fatigue deterioration is improved when a large amount of blast furnace slag fine aggregate is contained. Based on the above findings, the present inventor has reached the following present invention excellent in resistance to combined frost damage and fatigue.

  The present invention has been made in view of the above, and an object of the present invention is to provide a concrete composition excellent in resistance to combined deterioration of frost damage and fatigue, a molded product formed from the composition, and a floor slab. To do.

  In order to solve the above-described problems and achieve the object, the concrete composition according to the present invention is a concrete composition containing fine aggregate containing a blast furnace slag fine aggregate, a binder containing cement, and water. 30 cycles of a freeze-thaw test based on method A described in JIS A 1148 and 200,000 cycles of a fatigue test by repeated loading under a predetermined load condition for a concrete specimen prepared from the concrete composition When the test is repeated alternately, the fatigue test has a high durability that does not break even after 1.6 million cycles.

  Further, another concrete composition according to the present invention is a concrete composition containing a fine aggregate containing a blast furnace slag fine aggregate, a binder containing a cement, and water, the concrete composition Fatigue due to 30 cycles of freeze-thaw test based on method A described in JIS A 1148 for reinforced concrete specimens with a design bending strength of 15.6 kN · m produced by an object, and repeated loading with a minimum load of 15 kN, a maximum load of 45 kN, and a frequency of 5 Hz When the test is repeated 200,000 cycles alternately, it has a high durability that does not break even in the fatigue test of 1.6 million cycles.

  Further, another concrete composition according to the present invention is a concrete composition containing a fine aggregate containing a blast furnace slag fine aggregate, a binder containing a cement, and water, the concrete composition 30 cycles of freeze-thaw testing based on method A described in JIS A 1148 for prestressed concrete specimens with a design bending strength of 15.6 kN · m produced by the object, and repeated loading with a minimum load of 15 kN, a maximum load of 45 kN, and a frequency of 5 Hz When the fatigue test is repeated 200,000 cycles alternately, the fatigue test is characterized by having high durability that does not break even in the fatigue test of 2.4 million cycles.

  Another concrete composition according to the present invention is characterized in that, in the above-described invention, the composition has high durability that does not break even in the fatigue test of 4 million cycles.

  Another concrete composition according to the present invention is characterized in that, in the above-described invention, salt water having a concentration of 10% by mass is used as a solution for immersing the concrete specimen in the freeze-thaw test. To do.

  The concrete molded product according to the present invention is formed by molding the above-described concrete composition.

  Another concrete molded article according to the present invention is characterized by molding the above-described concrete composition through steam curing.

  Another concrete molded article according to the present invention is characterized in that the above-described concrete composition is molded as a prestressed concrete member or a reinforced concrete member.

  Moreover, the floor slab according to the present invention is characterized by comprising the above-described concrete molded product.

  In addition, another floor slab according to the present invention is used as a floor slab for a road or a bridge in the above-described invention.

  The concrete composition according to the present invention is a concrete composition containing a fine aggregate containing a blast furnace slag fine aggregate, a binder containing cement, and water, wherein the concrete composition comprises In the case where the freeze-thaw test 30 cycles based on the method A described in JIS A 1148 and the fatigue test 200,000 cycles by repeated loading under a predetermined load condition were alternately repeated for the prepared concrete specimen, Since the fatigue test has a high durability that does not break even after 1.6 million cycles, it is possible to provide a composition for concrete having excellent resistance to frost damage and combined deterioration of fatigue, a molded product formed from the composition, and a floor slab. There is an effect.

FIG. 1 is a schematic diagram of the dimensions of a test body, where (1) is an RC beam test body and (2) is a PC beam test body. Moreover, (a) is a cross-sectional view, and (b) is a vertical cross-sectional view along the AA line of (a). FIG. 2 is a diagram illustrating a loading position in the fatigue test. FIG. 3 is a diagram showing a procedure of a freeze-thaw test and a fatigue test according to the present invention, where (1) is a schematic diagram and (2) is a photograph showing a test situation corresponding to (1). FIG. 4 is a load-strain diagram (RC beam) at the time of reloading, in which (1) relates to the concrete upper edge strain and (2) relates to the reinforcing bar strain. FIG. 5 is a load-strain diagram (PC beam) at the time of reloading. (1) relates to the concrete upper edge strain and (2) relates to the PC steel rod strain. FIG. 6 is a state photograph of the RC beam (crushed sand) when the combined deterioration test is completed. FIG. 7 is a state photograph of the RC beam (blast furnace slag fine aggregate) when the composite deterioration test is completed. FIG. 8 is a state photograph of the PC beam (crushed sand) when the combined deterioration test is completed. FIG. 9 is a state photograph of the PC beam (blast furnace slag fine aggregate) when the combined deterioration test is completed. FIG. 10 is a diagram showing a cracking situation when the composite deterioration test is completed. (1) is an RC beam (crushed sand), (2) is an RC beam (blast furnace slag fine aggregate), and (3) is a PC beam. (Crumbled sand) and (4) relate to PC beams (blast furnace slag fine aggregate). FIG. 11 is a comparison diagram of the concrete stress intensity ratio during repeated loading. FIG. 12 is a comparison diagram of steel material stress intensity ratios during repeated loading. FIG. 13 is a comparison diagram of stress intensity ratios (calculated values). FIG. 14 is a diagram showing the results of a freeze / thaw test using a specimen, where (1) is a relative kinematic modulus, and (2) is a diagram regarding a mass change rate. FIG. 15 is a diagram showing the results of a freeze-thaw test for ordinary concrete. FIG. 16 is a diagram showing the results of a freeze-thaw test for concrete using blast furnace slag fine aggregate.

  DESCRIPTION OF EMBODIMENTS Embodiments of a concrete composition according to the present invention, a molded product formed by molding the concrete composition, and a floor slab will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiments.

  A concrete composition according to the present invention is a concrete composition containing a fine aggregate containing a blast furnace slag fine aggregate, a binder containing cement, and water, and the concrete produced by the concrete composition. 30 cycles of freeze / thaw tests based on method A described in JIS A 1148 (concrete freeze-thaw test method) for specimens and 200,000 cycles of fatigue tests by repeated loading under predetermined load conditions In this case, it has high durability that does not break even in a fatigue test of 1.6 million cycles, and is excellent in resistance to combined deterioration of frost damage and fatigue (repeated load loading).

  Here, in the above-mentioned freeze-thaw test, a 10% salt water (10% sodium chloride aqueous solution in mass percent concentration) may be used in a solution in which the specimen is immersed. In general, a freeze-thaw test using salt water is a test under severer conditions than that using fresh water.

Blast furnace slag is by-produced when pig iron is produced in the blast furnace, and its main components are CaO, SiO ₂ , Al ₂ O ₃ , and MgO. This blast furnace slag can be used in the form of blast furnace slag fine aggregate.

  The blast furnace slag fine aggregate is an amorphous blast furnace slag fine aggregate. As the amorphous blast furnace slag fine aggregate, for example, blast furnace granulated slag obtained by quenching blast furnace slag with water and lightly crushed and added with an anti-caking agent can be used. The temperature of the molten blast furnace slag immediately before being rapidly cooled in the production of granulated blast furnace slag is 1400-1500 degrees, and by rapid cooling, it is consolidated without any atomic arrangement to the crystals, and is glassy (non-crystalline) It becomes. The quality of blast furnace slag fine aggregate is specified in JIS A 5011-1.

  Examples of the cement used in the present invention include ordinary Portland cement, early-strength Portland cement, super-early-strength Portland cement, moderately hot Portland cement, and low heat Portland cement.

  The concrete composition of the present invention contains a fine aggregate containing a blast furnace slag fine aggregate, a binder containing a cement, and water, but the blast furnace slag fine aggregate for the fine aggregate (S). The mass ratio (BFS / S) of (BFS) is preferably 0.6 to 1.0. As the fine aggregate, in addition to the blast furnace slag fine aggregate, for example, a general fine aggregate such as sandstone crushed sand can be used.

  The concrete composition of the present invention usually further comprises coarse aggregate, and the concrete composition is cured to obtain concrete. As the coarse aggregate, for example, a general coarse aggregate such as sandstone crushed stone can be used. Here, the amount (W) of water used in the concrete composition is that the mass ratio (W / B) of water (W) to the binder (B) is 0.25 to 0.40, that is, the binding. It is preferable that water (W) is 25-40 mass parts with respect to 100 mass parts of material (B). Moreover, as a usage-amount of the coarse aggregate in the composition for concrete, it is preferable that a coarse aggregate is 100-500 mass parts with respect to 100 mass parts of binder (B). The concrete composition of the present invention may further contain other components as long as the effects of the present invention are not impaired.

  The concrete composition of the present invention is excellent in resistance to frost damage and fatigue due to repeated loading. Therefore, the concrete composition of the present invention is effective as a material for concrete structures such as concrete floor slabs and beams of road bridges in cold districts and salt damage environments where frost damage resistance and fatigue resistance are required. Moreover, according to this invention, it is possible to suppress the earth-and-sand generation which arises on the surface of the concrete floor slab of a road bridge, etc. reliably.

  Moreover, the composition for concrete of this invention is excellent also in the resistance with respect to salt damage so that it may mention later. Therefore, it is particularly effective for construction where buildings are required to have salt damage resistance, and places where frost damage, salt damage and fatigue can occur in combination, such as highways in mountainous areas where snow melting agents are sprayed in winter. In addition to these applications, for example, in sites where frost resistance, fatigue resistance and salt damage resistance are required for coastal structures, marine structures, waterway structures, road structures, retaining wall structures in cold regions. Preferably used. At this time, the concrete composition of the present invention may be molded in advance and applied as a molded product (precast concrete product).

[Verification of effects of the present invention]
Next, the effect of this invention is demonstrated using the test outline | summary and test result of FIGS. In this test, in order to confirm that the concrete composition of the present invention is excellent in resistance to combined frost damage and fatigue deterioration, the method A described in JIS A 1148 (Concrete freeze-thaw test method) is used. A combined deterioration test is performed in which a test based on the freeze-thaw test and a fatigue test by repeated loading are alternately performed.

(Outline of specimen)
Reinforced concrete (hereinafter referred to as RC) structure and PC structure beam specimens (concrete specimens; specimens; hereinafter also referred to as RC beams and PC beams) by concrete using blast furnace slag fine aggregate and sandstone crushed sand as fine aggregates. It was created. An outline of the test specimen is shown in FIG. The dimensions of each test specimen were 1350 mm long × 125 mm wide × 200 mm high so as to fit in a large freeze-thaw test apparatus. The test specimens were adjusted in steel size and position so that the bending strength was equal for both RC beams and PC beams. This is to confirm the difference in deterioration due to the difference in structure.

  Table 1 shows the concrete composition of the test specimen. The blending was made into two types when only blast furnace slag fine aggregate was used for fine aggregate and when only sandstone crushed sand was used.

Here, early strong Portland cement (C) is used as the binder (B), crushed sandstone is used as the coarse aggregate (G), and sandstone crushed sand (CS) and blast furnace slag fine aggregate are used as the fine aggregate (S). (BFS) was used. AE agent and high performance AE water reducing agent are used for admixture of concrete using sandstone crushed sand, and high performance AE water reducing agent, thickener and defoaming agent are used for concrete using blast furnace slag fine aggregate. Using. The amount of air (Air) was 4.5% and 2.0%. The fine aggregate rate (s / a) is as shown in Table 1. The water-cement ratio (W / B) of the concrete was 35%, the strength was approximately the same, and the unit water amount (W) was 155 kg / m ³ . This assumes a concrete manufactured at a PCa factory, and has a composition having the same level of fresh performance. Table 2 shows the physical property values of the materials used corresponding to the test body numbers. The specimen numbers 2 and 4 correspond to the examples of the present invention. Test body numbers 1 and 3 are comparative examples.

(Compound deterioration test of specimen)
As shown in FIG. 3, the composite deterioration test is assumed to start from the age of 7 days, and 30 cycles of the freeze-thaw test based on the method A described in JIS A 1148: 2010, a minimum load of 15 kN, and a maximum load. The fatigue test by repeated loading at 45 kN and a frequency of 5 Hz is alternately repeated until 200,000 cycles until the specimen is destroyed. Here, in the fatigue test, loading is performed by load control with respect to the loading position as shown in FIG.

  Each specimen is subjected to air curing until the age of 7 days after steam curing. First, a static loading test was performed on the specimen before the combined deterioration loading, and after the damage was given, a combined deterioration test was performed. In this static loading test, each test body is loaded to the ultimate load, then unloaded once, and then loaded to the ultimate load again to experience one cycle of load loading. After experiencing this ultimate load, the composite deterioration test is performed by alternately performing a freeze-thaw test of 30 cycles and a fatigue test of 200,000 cycles.

  In the freeze-thaw test, a 10% NaCl aqueous solution (10% sodium chloride aqueous solution in mass percent concentration) was used with reference to the water freeze-thaw method (Method A) prescribed in JIS A 1148: 2010, and the test specimen absorbed water. The sheet was wound, frozen in a wet state, and thawed in 20 ° C. water. In general, a freeze-thaw test performed using salt water (NaCl aqueous solution) is a test under severer conditions than that performed using fresh water.

  The fatigue test conducted after completion of a predetermined freeze-thaw cycle was performed by applying a sine wave having a frequency of 5 Hz and a minimum load of 15 kN which is a crack generation load, a maximum load of 45 kN which is twice the use load. A combination of 30 cycles of the freeze / thaw test and 200,000 cycles of the fatigue test was taken as one circuit, and this was repeated.

  In addition, since the fatigue test of each test body cannot be performed simultaneously, it left still in 10% NaCl aqueous solution by the start. Before and after the fatigue test was started, the progress of cracks was confirmed, and the crack widths at major locations were measured with a microscope.

(Test results)
FIG. 4 (1) is a load-reinforced strain diagram when the RC beam is reloaded, and (2) is a load-rebar strain diagram. The RC beam using blast furnace slag fine aggregate as the fine aggregate has a slightly larger strain at the upper edge of the concrete at the same load than that using the sandstone crushed sand. FIG. 5 (1) is a load-concrete upper edge strain diagram when the PC beam is reloaded, and (2) is a load-PC steel bar strain diagram. In the PC beam using blast furnace slag fine aggregate as the fine aggregate, the strain on the upper edge of the concrete is slightly larger at the same load than that using the sandstone crushed sand. This is thought to be due to the difference in the position of the neutral axis due to the difference in height from the lower edge of the crack. For RC beams, the difference between sandstone crushed sand and blast furnace slag fine aggregate is large, but for PC beams, this difference is not large.

  Table 3 shows the result of destruction / termination of the composite deterioration test. 6 to 9 show photographs of the situation where the combined deterioration test has been completed. FIG. 10 is a diagram showing the crack distribution. (1) corresponds to FIG. 6, (2) corresponds to FIG. 7, (3) corresponds to FIG. 8, and (4) corresponds to FIG.

  As shown in Fig. 6, RC beam using crushed sand is broken by breaking the steel material (tensile rebar) that receives tension inside RC beam at the 8th circuit (freeze-thaw test 240 cycles, fatigue test 1.6 million cycles). The test was completed.

  As shown in Fig. 7, RC beams using blast furnace slag fine aggregates, as well as the 8th circuit, the tensile reinforcement does not break even at the 20th circuit (freeze-thaw test 600 cycles, fatigue test 4 million cycles). Did not destroy. Thus, it was confirmed that the RC beam using the blast furnace slag fine aggregate is not affected by the composite deterioration effect more than twice that of the RC beam using crushed sand. Therefore, it turns out that the composition for concrete of this invention and its molded article are excellent in the resistance to frost damage and the combined deterioration of fatigue.

  As shown in FIG. 8, in the PC beam using crushed sand, the upper edge of the concrete was crushed (sedimentation) in the middle of the 12th circuit (freeze-thaw test 360 cycles, fatigue test 2.3 million cycles), and the test was completed. .

  As shown in FIG. 9, in the PC beam using the blast furnace slag fine aggregate, the concrete was not crushed and destroyed at the 20th circuit (freezing and thawing test 600 cycles, fatigue test 4 million cycles). As described above, it was confirmed that the PC beam using the blast furnace slag fine aggregate is not affected by the combined deterioration effect of about twice that of the PC beam using crushed sand. Therefore, it turns out that the composition for concrete of this invention and its molded article are excellent in the resistance to frost damage and the combined deterioration of fatigue.

  As shown in Fig. 10, from the crack figure of composite deterioration and the state of RC beam and PC beam at the end of the test, the cracks of specimen number 1 and specimen number 2 (RC beam) are distributed in the longitudinal direction of the beam. It can also be seen that the crack width is small. On the other hand, in specimen No. 3 and specimen No. 4 (PC beam), it can be seen that the cracked portions are concentrated immediately below the loading point, and progressed from the lower edge toward the upper edge. Test No. 1 using sandstone crushed sand finished the test with the main rebar breaking. From the crack figure, the tendency of the crack at the fractured position is not clear, but when the specimen was cut after completion, rusting of the rebar in the cracked part was confirmed, so stress was concentrated on the corrosion and cracked part. Therefore, it is thought that it broke.

  Specimen No. 3 and Specimen No. 4 (PC beam) were subjected to a composite deterioration action of 10 circuits or more. However, in Specimen No. 3, the test was terminated at 12 circuits due to missing upper edge concrete.

  Tables 4 and 5 show the stresses generated in the upper edge concrete, the reinforcing bars and the PC steel bars at the minimum load and the maximum load, and FIGS. 11 and 12 show the distribution diagrams. For reference, the calculated values are shown in FIG. The calculated values in FIG. 13 are the upper and lower limits (stress amplitude) of the compressive stress of concrete and the tensile stress of the steel material that are affected by the upper and lower load loads of 45 kN and 15 kN, and are based on the assumption that the cross section is sound. .

  Regarding the upper edge concrete stress state of the RC beam, the specimen No. 2 using the blast furnace slag fine aggregate as the fine aggregate receives a greater stress strength than the specimen No. 1 using the sandstone crushed sand, and Fatigue loading is performed with a large stress amplitude. The same applies to the stress intensity and stress amplitude of the reinforcing bars.

  Regarding the upper edge concrete stress state of the PC beam, the specimen No. 4 using the blast furnace slag fine aggregate as the fine aggregate receives a larger stress strength than the specimen No. 3 using the sandstone crushed sand, and Fatigue loading is performed with a large stress amplitude. As for the PC steel bar stress strength, specimen No. 3 using sandstone crushed sand is acting with greater stress intensity and stress amplitude than specimen No. 4 using blast furnace slag fine aggregate as fine aggregate. Comparing the stress intensity of the upper edge concrete of the RC beam and the PC beam, the amplitude of the stress intensity ratio of the upper edge concrete of the PC beam is larger than that of the RC beam, and the PC beam is more burdensome than the RC beam in the upper edge concrete. Is big. As for the amplitude of the stress intensity ratio of the reinforcing steel and the PC steel rod which are the steel materials on the tension side, the stress amplitude of the reinforcing steel is larger than the stress intensity amplitude of the PC steel rod.

  From the cracked state and the stress state at the time of fatigue loading, concrete using blast furnace slag fine aggregate is superior to concrete using sandstone crushed sand against composite deterioration. In addition, the PC beam has an advantage over the RC beam over the combined deterioration effect. This is thought to be due to the difference in the load ratio between tensile steel and concrete due to the difference in the structure between RC and PC, and the different failure modes. PC beams using crushed sandstone are those whose damage has progressed due to the deterioration of the composite shaft and the neutral axis of the upper edge of the concrete due to the gradual peeling of the concrete at the upper edge, and the strength of the concrete on the upper edge and the stress strength of the PC steel bar increased. it is conceivable that. The PC beam using the blast furnace slag fine aggregate shows excellent deterioration resistance even in a high concrete stress state.

(Verification of concrete properties using blast furnace slag fine aggregate used for test specimens)
We examined the freeze-thaw resistance of concrete specimens using the above blast furnace slag fine aggregates and compared them with concrete specimens using sandstone crushed sand as fine aggregates. This will be described below.

(Test method)
Specimens for physical properties were collected in the same manner as the concrete used in the above test specimens. The freeze-thaw test was performed on a 100 × 100 × 400 mm prism specimen subjected to steam curing or underwater curing in accordance with the underwater freeze-thaw method (Method A) defined in JIS A 1148: 2010. As water for freezing in the freeze-thaw test, a 10% aqueous sodium chloride solution was used at a mass percent concentration.

(Test results)
FIG. 14 shows the results of the freeze / thaw test. As shown in FIG. 14 (1), in the freeze-thaw test, none of the specimens has a relative kinematic modulus lower than 60% by 300 cycles. Concrete that uses underwater curing after steam curing and sandstone crushed sand as a fine aggregate has deteriorated due to a significant decrease in the relative kinematic modulus after 300 cycles, and the mass change rate in FIG. Mass loss is ahead. From the above, it can be seen that even when the AE agent is not used, sufficient freezing and thawing resistance is exhibited if a blast furnace slag fine aggregate is used as the fine aggregate.

(Summary)
Each test described above confirmed the following.
(1) As a result of investigating the combined deterioration of RC beams and PC beams, which are concrete structural members using blast furnace slag fine aggregate, due to freezing and thawing and repeated loading, blast furnace slag fine aggregate is used as the fine aggregate of concrete structural members As a result, combined degradation due to freezing and thawing and repeated loading can be suppressed. Therefore, the concrete composition of the present invention and the molded product thereof are excellent in resistance to combined frost damage and fatigue deterioration.

(2) Even when steam curing is performed with Non-AE concrete, the concrete using the blast furnace slag fine aggregate has high durability without lowering the freeze-thaw resistance.

(3) The concrete using the blast furnace slag fine aggregate has high durability even in a state where the concrete has a high stress level and a large stress level amplitude.

(4) An RC beam using a blast furnace slag fine aggregate can withstand a higher repeated loading action than an RC beam using crushed sand as a fine aggregate. Moreover, the PC beam using the blast furnace slag fine aggregate can endure a higher repeated loading action than the PC beam using crushed sand as the fine aggregate.

  From the above, in order to improve the composite deterioration resistance performance of concrete, it is preferable to use blast furnace slag fine aggregate as a part of fine aggregate in the concrete composition. In this case, in order to further improve the combined deterioration resistance, the mass ratio of water to the binder (W / B) is preferably 0.25 to 0.40, and 0.35 (W / B = 35%). Is more preferable. Moreover, it is preferable that the mass ratio of the blast furnace slag fine aggregate to the fine aggregate is 1.0.

  Moreover, when the molded article of the present invention is applied to a floor slab for a cold district road or bridge as a prestressed concrete member or a reinforced concrete member, the rusting of the concrete is suppressed due to its excellent frost resistance and fatigue resistance. . Therefore, when the molded article of the present invention is used, the service life of the floor slab can be extended as compared with the case where a general ordinary prestressed concrete member or reinforced concrete member is used. For this reason, it is possible to suppress repair and renewal costs.

  As described above, the concrete composition according to the present invention is a concrete composition containing a fine aggregate containing a blast furnace slag fine aggregate, a binder containing cement, and water, 30 cycles of the freeze-thaw test based on method A described in JIS A 1148 and 200,000 cycles of the fatigue test by repeated loading under a predetermined load condition are alternately repeated for a concrete specimen manufactured using the concrete composition. In the case where it is carried out, the fatigue test has a high durability that does not break even in 1.6 million cycles. Therefore, a concrete composition excellent in resistance to frost damage and combined deterioration of fatigue and a molded product and a floor slab formed from the same are obtained. There is an effect that it can be provided.

  As described above, the concrete composition according to the present invention and the molded product formed by molding it and the floor slab are useful as a material for a structural member on which a repeated load acts like a concrete floor slab of a bridge, In particular, it is suitable for suppressing concrete sedimentation.

Claims (6)

It is a structural member made of reinforced concrete that is subjected to repeated loads,
JIS, comprising a fine aggregate containing a blast furnace slag fine aggregate, a binder containing cement, a concrete made of a concrete composition containing water, and a reinforcing bar provided inside the concrete and receiving a tensile force, The amplitude of the stress intensity ratio that acts on the reinforcing bar by 30 cycles of the freeze-thaw test based on the A method described in A 1148 and the repeated loading by the repeated loading of the minimum load 15 kN, the maximum load 45 kN, and the frequency 5 Hz acts on the concrete. in the stress intensity ratio amplitude intends row alternately repeated and a fatigue test 200,000 cycles to prevailing test conditions of the structural member characterized by having a resistance to the fatigue test 1.6 million cycles or more cyclic loading. A structural member made of prestressed concrete on which repeated loads act,
JIS A 1148, comprising a fine aggregate containing a blast furnace slag fine aggregate, a binder containing cement, a concrete made of a composition for concrete containing water, and a PC steel material provided inside the concrete, The amplitude of the stress intensity ratio acting on the concrete acts on the PC steel by 30 cycles of the freeze-thaw test based on the method A and the repeated load of the minimum load of 15 kN, the maximum load of 45 kN, and the frequency of 5 Hz. in the stress intensity ratio amplitude intends row alternately repeated and a fatigue test 200,000 cycles to prevailing test conditions, structural member characterized by having a resistance to the fatigue test 2.4 million cycles or more cyclic loading. The structural member according to claim 1 , wherein the structural member has durability against a repeated load of 4 million cycles or more . Wherein a solution of dipping the test specimen in the freeze-thaw test, structural member according to any one of claims 1-3, characterized in that the concentration with 10% water at a mass ratio. A floor slab comprising the structural member according to any one of claims 1 to 4 . The floor slab according to claim 5 , which is used as a floor slab for a road or a bridge.