Concrete pouring method

Abstract

To provide a concrete placing method suitable for the manufacturing of an expansive admixture-combined lightweight concrete floor slab or the like.SOLUTION: A concrete placing method of the invention has the steps of: performing a bleeding test and a pressurized bleeding test for concrete prior to force feeding which is lightweight concrete; determining the quality of the force-feeding property of the concrete on the basis of test results of the bleeding test and the pressurized bleeding test; and force-feeding and placing the concrete when the force-feeding property of the concrete is determined to be good.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for pouring concrete. [Background technology]

[0002] In road bridges, where the road structure is supported by piers and other structures, reinforced concrete (RC) decks made of lightweight concrete using lightweight aggregate are often used in order to reduce the weight of the road structure.

[0003] Lightweight concrete usually has lower tensile and shear strengths than ordinary concrete. RC decks are subject to punching shear failure due to repeated wheel loads from vehicles running above them, and diagonal cracks penetrate between the top and bottom surfaces of the deck, leading to ultimate failure. However, the durability of RC decks made of lightweight concrete is largely dependent on the strength of the concrete, and it is believed that the durability of RC decks made of lightweight concrete is inferior to that of ordinary concrete.

[0004] In response to this, there is a technique for improving the strength of lightweight concrete in which prestress is introduced into the concrete using tension members. On the other hand, by mixing expansive materials into the concrete as in Patent Documents 1 and 2, the tensile resistance of the concrete can be improved by chemical prestress caused by the expansion of the expansive materials, and the effort of mechanically introducing prestress can be eliminated. Patent Document 3 discloses a lightweight concrete deck slab in which chemical prestress is introduced using expansive materials and water resistance is also improved. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-44806 A [Patent Document 2] Patent No. 3658568 [Patent Document 3] Patent No. 6082207 Summary of the Invention [Problem to be solved by the invention]

[0006] The practical application of high-strength lightweight concrete decks will contribute to improving the productivity of road structures, including repair and reinforcement, and reducing life cycle costs by realizing durable and lightweight RC decks.

[0007] The present invention has been made in consideration of the above problems, and has an object to provide a concrete pouring method suitable for producing a deck slab made of lightweight concrete with expansive additive, etc. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a method for testing lightweight concrete before pumping, comprising the steps of: performing a bleeding test and a pressure bleeding test; The test results show the bleeding rate and the results of the pressurized bleeding test and the final dehydration rate is , The bleeding rate and the final dewatering rate are substituted into two variables of a judgment formula set as a boundary between good and bad pumpability from the distribution relationship of the graph, and the above judgment formula is used to This is a concrete pouring method characterized by comprising a step of determining whether the pumpability of the concrete is good or bad, and a step of pumping and pouring the concrete when the pumpability of the concrete is determined to be good.

[0009] It is also desirable that the concrete contains an expansive material in addition to the lightweight aggregate and cement, the amount of the expansive material is 0.75 to 1.1 times the standard admixture amount of the expansive material, and the water-binder ratio of the concrete is 30% by weight or more and less than 38% by weight.

[0010] Conventionally, lightweight concrete has often not been pumped well due to blockages, etc., so pumpability has traditionally been confirmed by test pumping before pouring. In contrast, in the present invention, test pumping can be omitted by determining pumpability in advance based on the results of the bleeding test and pressure bleeding test as described above, which contributes to shortening construction time and improving workability.

[0011] The above-mentioned concrete pouring method is suitable for lightweight concrete, which can sometimes be difficult to pump due to blockages, but it can also be applied to other types of concrete, and by determining in advance whether the pumpability is good or bad, it is possible to prevent blockages in the concrete. Effect of the Invention

[0012] The present invention can provide a concrete pouring method suitable for producing a deck slab made of lightweight concrete with expansive additive, etc. [Brief description of the drawings]

[0013] [Figure 1] A diagram showing the cross-sectional structure of road structure 3 in the thickness direction. [Diagram 2] A diagram showing road structure 3. [Diagram 3] 1 is a flowchart showing a concrete pouring method. [Figure 4] FIG. 2 is a diagram showing the mix proportions of concrete in Example 1 and Comparative Example 1. [Diagram 5] FIG. [Figure 6] A diagram showing prestress perpendicular to the bridge axis. [Figure 7] FIG. 1 is a diagram showing a test apparatus 10. [Figure 8] FIG. [Figure 9] FIG. 1 shows the mix proportions of concrete in Example 2-10. [Figure 10] FIG. [Figure 11] FIG. [Figure 12] FIG. [Figure 13] FIG. 1 shows the mix proportions of concrete in Example 11 and Comparative Example 2-5. [Figure 14] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0015] (1. Road structure 3) FIG. 1 is a diagram showing a road structure 3 including a deck (expansive lightweight concrete deck) 31 according to an embodiment of the present invention, and shows the cross-sectional configuration of the road structure 3 in the thickness direction.

[0016] As shown in FIG. 1, a road structure 3 includes a deck 31, a pavement layer 35, and the like.

[0017] The deck 31 is an expansive lightweight concrete deck made of concrete containing expansive material, lightweight aggregate, cement, etc., and has reinforcing bars 311 embedded inside. The reinforcing bars 311 are provided on the upper and lower parts of the deck 31, and are arranged vertically and horizontally so as to intersect at right angles on a plane. The deck 31 is constructed by pouring concrete on-site.

[0018] The expansive material used in concrete is not particularly limited as long as it expands by hydration. As described in Patent Documents 1 and 2, for example, an expansive material that expands by hydration through the production of calcium hydroxide and conforms to JIS A 6202 can be used.

[0019] In this embodiment, the standard mixing amount of this expansive material is 1 m of concrete. 3 The expansive material is 20 kg per m of concrete, and is mixed at a ratio of 0.75 to 1.1 times the standard amount. 3 The mixing amount is set to 15 kg to 22 kg per m of concrete. This allows for an appropriate amount of chemical prestressing by the expansive material, which will improve the strength of the deck 31, as described later. 3 A standard type of expanding agent, which is 30 kg per unit weight, may be used. In this case, too, the amount to be mixed should be 0.75 to 1.1 times the standard mixing amount.

[0020] The lightweight aggregate may be, for example, a conventionally known artificial lightweight aggregate made from expanded shale. For example, the lightweight aggregate may be one that has absorbed water in advance, or a low-water-content lightweight aggregate with a water content of more than 0% by weight but not more than 5% by weight may be used. In particular, in the latter case, by using low-water-content aggregates for both the fine aggregate and the coarse aggregate, the resistance to freezing and thawing (frost resistance) can be significantly improved, as will be described in detail in the examples below.

[0021] The cement is not particularly limited, and various known Portland cements can be used. It is also possible to add various admixtures such as a water reducing agent and an air content adjusting agent.

[0022] Here, the unit amount of water in preparing the concrete is set to 1 m of concrete from the viewpoint of ensuring the strength, i.e., durability, of the floor slab 31. 3 The amount is relatively small for on-site casting, between 165kg and 175kg per concrete, and the water-binder ratio is preferably between 30% and 38% by weight. Note that the binder refers to cement and expansive material, and the weight of the binder is the combined weight of the cement and expansive material.

[0023] By setting the water-binder ratio to less than 38% by weight, it is possible to obtain a deck slab 31 with higher strength. Also, if the water-binder ratio is 30% by weight or more, it is possible to ensure the workability required for the deck slab 31 using cast-in-place concrete.

[0024] The pavement layer 35 constitutes the road surface on which vehicles etc. run. The pavement layer 35 may be a conventionally known material, and may be formed of, for example, asphalt etc. It is also possible to provide a waterproof layer between the deck 31 and the pavement layer 35.

[0025] The road structure 3 of this embodiment can be placed on a bridge pier 1a as shown in FIG. 2(a), and the weight reduction of the road structure 3 allows the weight reduction of the substructure, which reduces the overall weight of the bridge, reduces the manufacturing and construction costs, and improves earthquake resistance. In addition, the road structure 3 can be placed on a box culvert 1b as shown in FIG. 2(b), or may be placed inside a shield tunnel 1c as shown in FIG. 2(c). It can be applied to various other roads. The deck 31 can be used not only for new roads, but also for replacing existing decks.

[0026] (2. Concrete pouring method) FIG. 3 is a flow chart showing a concrete pouring method for constructing the deck slab 31.

[0027] In this embodiment, when concrete is poured, a bleeding test and a pressure bleeding test are performed on the concrete before pumping (S1), and the pumpability is judged based on the test results (S2). The bleeding test and the pressure bleeding test, and the judgment of the pumpability based on the test results will be described later in the examples.

[0028] If the pumpability is judged to be good (S3; Good), the concrete is pumped and poured (S4). On the other hand, if the pumpability is judged to be bad (S3; Bad), steps S1 to S3 are repeated for another concrete with a different mix ratio, mixing method, etc.

[0029] Through the above procedure, the concrete for the deck 31 is poured on-site. Conventionally, lightweight concrete has often not been pumped well due to blockages and the like, so pumpability has traditionally been confirmed by test pumping before pouring. In contrast, in this embodiment, the pumpability is determined in advance based on the results of the bleeding test and pressure bleeding test as described above, making it possible to omit the test pumping, which contributes to shortening the construction period and improving workability.

[0030] As mentioned above, when low-moisture-content fine and coarse aggregates are used, pouring by pressure may be difficult. In that case, however, pouring by a method other than pressure, such as using a bucket, can still be used. EXAMPLES

[0031] The effects of the deck of this embodiment will be described below with reference to examples, although the present invention is not limited thereto.

[0032] [Durability] The deck 31 of this embodiment contains an expansive material in addition to the lightweight aggregate and cement as described above, and the amount is about the standard mixing amount (concrete shrinkage compensation amount). First, a wheel load running test was performed on the deck, and the durability was examined, and the results are described below as Example 1.

[0033] (Example 1 and Comparative Example 1) The concrete of Example 1 and Comparative Example 1 was prepared by mixing the following materials as water, cement, expansive material, aggregates (fine aggregate and coarse aggregate), and admixtures, such as an AE water-reducing agent and an AE agent, according to the ratio shown in Fig. 4. Note that the amounts of the AE water-reducing agent and AE agent shown in Fig. 4 are weight ratios (% by weight) to the weight of the binder, and the standard amount of expansive material is 1 m of concrete. 3 The weight of the concrete is 20 kg per one. Comparative Example 1 is an example in which no expansive material is used, and the expansive material in Example 1 is replaced with cement.

[0034] Water; Tap water Cement: Ordinary Portland cement, manufactured by Taiheiyo Cement Corporation Expansion material: Denka Power CSA manufactured by Denka Co., Ltd. Fine aggregate; artificial lightweight aggregate Mesalite fine aggregate manufactured by Nippon Mesalite Kogyo Co., Ltd. Coarse aggregate; artificial lightweight aggregate Mesalite coarse aggregate manufactured by Nippon Mesalite Kogyo Co., Ltd. AE water reducing agent; AE water reducing agent standard type (Type I) Yamaso 09NL-P manufactured by Yamaso Chemical Co., Ltd. Air Entrainer: Air Entrainer (Type I) Master Air 202, manufactured by BASF Japan Ltd.

[0035] (Wheel load running test) A deck specimen was made using the concrete prepared according to the mix ratio shown in Figure 4, and a wheel load running test was conducted.

[0036] Fig. 5 is a diagram showing the plan of this specimen 30. As shown in Fig. 5, specimen 30 is a flat plate with a rectangular plan, and its dimensions are 2,800 mm long x 4,500 mm wide x 250 mm thick. Inside specimen 30, lattice-shaped reinforcing bars 301 are arranged in two rows, upper and lower, with the arrangement of the upper row of reinforcing bars 301 shown in the upper half of the figure and the arrangement of the lower row of reinforcing bars 301 shown in the lower half of the figure.

[0037] In addition, for Example 1, the load was 0.5 N / mm 2 More than 1.2N / mm 2 The mixture is mixed so that the following appropriate chemical prestress is introduced. Figure 6 shows the value of chemical prestress in the direction perpendicular to the bridge axis for the specimen 30 of Example 1, with the material age on the horizontal axis. It was 0.68 N / mm at 28 days of material age. 2 It can be seen that chemical prestress of at least about 100% has been introduced. Note that the direction perpendicular to the bridge axis corresponds to the vertical direction in Fig. 5, and the horizontal direction in Fig. 5 corresponds to the bridge axis direction.

[0038] Here, the value of chemical prestress σcp in the direction perpendicular to the bridge axis can be obtained from the following formula (1) using the measured value of the strain gauge attached to the reinforcing bar 301 in the direction perpendicular to the bridge axis. In formula (1), ε is the average of the measured strain values ​​of the reinforcing bar 301 in the direction perpendicular to the bridge axis in the upper and lower stages, and Es is the Young's modulus of the reinforcing bar 301. Also, p is the restraining reinforcing bar ratio, and the cross-sectional area A of the vertical surface in the bridge axis direction of the specimen 30 is 1 The sum of the radial cross sections of the reinforcing bars 301 perpendicular to the bridge axis A 2 The ratio (=A 2 / A 1 ). σcp = ε·Es·p…(1)

[0039] The wheel load running test was carried out using a test device 10 shown in Fig. 7(a). This test device 10 has a loading section 13 attached to a rail 12 supported from the upper side of a gate-shaped frame 11, and applies a wheel load to a test piece 30 from this loading section 13.

[0040] One end of a crank rod 14 is attached to the load portion 13, and the other end of the crank rod 14 is attached to a flywheel 15. When the flywheel 15 rotates, the load portion 13 reciprocates along the rail 12 as indicated by the arrow A in the figure.

[0041] The specimen 30 is supported by supports 17, 18 provided on a stand 16. Fig. 7(b) is a diagram showing the arrangement of the supports 17, 18 on the plane of the specimen 30. The specimen 30 is simply supported by supports 17, 17 along each of its long sides, and is elastically supported by supports 18, 18 along each of its short sides.

[0042] Wheels are provided at the lower end of the loading section 13. These wheels move back and forth on the specimen 30 in accordance with the reciprocating movement of the loading section 13. The loading section 13 applies a wheel load to the specimen 30 by means of these wheels.

[0043] The wheel load is applied to the specimen 30 via the loading plate 19. The chain line C in Fig. 7(b) indicates the range of movement of the wheel on the loading plate 19, which was set to an area of ​​500 mm vertical × 3000 mm horizontal at the center of the specimen 30 here.

[0044] FIG. 8 shows the results of wheel load running tests carried out on the specimen 30 of Example 1 and the specimen 30 of Comparative Example 1 using the test device 10. FIG. 8 also shows the results of similar wheel load running tests carried out on a lightweight concrete deck (slab A) containing 1.5 times the standard amount of expansive additive as a reference example, and an ordinary concrete deck (slab B) not using expansive additive. The latter test results were obtained by converting the test results of the ordinary concrete deck RC8n-2 shown in the National Institute for Land and Infrastructure Management "Tests on fatigue durability of road bridge decks," NILIM Document No. 28, March 2002, into equivalent running times, which will be described later.

[0045] In the wheel load running test, the initial load at the start of running was 157 kN (16 tf) in Comparative Example 1, and the load was increased by 19.6 kN (2 tf) for every 40,000 runs. In Example 1, the load was increased in the same manner as in Comparative Example 1 until the number of runs reached 320,000, and after 320,000 runs, a constant load of 314 kN was applied. The number of runs was counted as one when the wheel of the load unit 13 of the test device 10 moved from one end of the moving range to the other end.

[0046] Figure 8 is a graph with the horizontal axis representing the equivalent number of runs (times) and the vertical axis representing the deflection (mm) at the center of specimen 30. The equivalent number of runs is the result of converting the actual number of runs into the number of runs under a constant load condition of a wheel load of 157 kN, and the equivalent number of runs Neq can be calculated using the following calculation formula (2). In formula (2), Pi (kN) is the actually applied load, and Ni (times) is the number of runs at load Pi. m is a coefficient for the equivalent conversion, and 12.76 is used here. Neq = Σ(Pi / 157) m ×Ni…(2)

[0047] As shown in FIG. 8, the equivalent number of runs for the specimen 30 of Example 1 is about 1.00×10 9 At 10,000 runs, the cracks penetrated obliquely from the top to the bottom of the deck, leading to punching shear failure. On the other hand, in the test piece 30 of Comparative Example 1, which did not use expansive material, the equivalent number of runs was about 2.17 × 10 8 After 10,000 runs, punch-out shear fracture occurred.

[0048] Thus, the specimen 30 of Example 1 had four times more durability than the specimen 30 of Comparative Example 1, and it was confirmed that the lightweight concrete slab using the expansive material has sufficient durability. In addition, in a comparison between Example 1 and slab A, the durability of Example 1 and slab A was equivalent or slightly lower than that of Example 1, but in a comparison between Example 1 and slab B, there was no significant difference in durability, and it was also found that in terms of durability, performance equivalent to that of a normal concrete slab can be obtained even if the amount of expansive material is kept to the standard mixing amount.

[0049] [Pumpability] The unit water content (165 to 175 kg / m) of the lightweight concrete used in the floor slab 31 of this embodiment 3 ) is relatively rare for on-site casting, so it is important to establish technology to confirm its pumpability and ensure its construction. Therefore, a pump pumping test was carried out to confirm its pumpability.

[0050] Here, the cause of the decrease in pumpability of lightweight concrete is thought to be the presence of strong aggregates of cement particles whose insides are not in contact with water (Masahiko Kishida et al., Study on the Pumpability of Lightweight Concrete Combined with Expansive Additives, Proceedings of the Cement and Concrete Society, Vol. 69, No. 1, pp. 279-286 (2015)). Therefore, in order to investigate the effects of these factors on the pumpability of lightweight concrete, we conducted both pressurized bleeding tests and bleeding tests.

[0051] (Examples 2 to 10) The concrete of Examples 2 to 10 was prepared by mixing the following materials as water, cement, expansive agent, aggregate (fine aggregate and coarse aggregate), and admixtures: AE water reducing agent, high-performance AE water reducing agent, and AE agent according to the ratio shown in Fig. 9. The amounts of AE water reducing agent, high-performance AE water reducing agent, and AE agent shown in Fig. 9 are weight ratios (weight %) to the weight of the binder. The standard amount of expansive agent is 1 m 3 The water-binder ratio of each of Examples 2 to 10 was about 37%. Each of Examples 2 to 10 was mixed with a target slump value of 18±2.5 cm and a target air content of 4.5±1.5%, which is equivalent to that of normal concrete.

[0052] Water; Tap water Cement: Ordinary Portland cement, manufactured by Taiheiyo Cement Corporation Expansion material HEx; Hyperexpan, manufactured by Pacific Materials Co., Ltd. Expansion material PC; Denka Power CSA Type S manufactured by Denka Co., Ltd. Fine aggregate; artificial lightweight aggregate Mesalite fine aggregate manufactured by Nippon Mesalite Kogyo Co., Ltd. Coarse aggregate; artificial lightweight aggregate Mesalite coarse aggregate manufactured by Nippon Mesalite Kogyo Co., Ltd. AE Water Reducing Agent AD 1 ;Floric SV10 manufactured by Floric Co., Ltd. AE Water Reducing Agent AD 2 ;Yamaso 09NLR-P manufactured by Yamaso Chemical Co., Ltd. High-performance AE water reducing agent SP; FLORIC SF500S manufactured by FLORIC Co., Ltd. Air Entrainer 1 ;Master Air 101 manufactured by BASF Japan Ltd. Air Entrainer 2 ;Master Air 202 manufactured by BASF Japan Ltd.

[0053] (Pumping test) The pumping tests were carried out in summer and winter to realize lightweight concrete that can be pumped throughout the year. For Examples 2, 3 and 7-10, the pumping tests were carried out in winter, and for Examples 4-6, the pumping tests were carried out in summer.

[0054] In this test, as shown in Fig. 10, concrete from a mixer truck 21 was pumped through a pump truck 22, and a pipe 23, a tapered pipe 24, and a flexible hose 25 were attached to the tip of a boom 221 of the pump truck 22 as shown in the figure. The horizontal conversion distance of the boom 221, pipe 23, tapered pipe 24, and flexible hose 25 combined was approximately 150 m.

[0055] (Bleeding test and pressure bleeding test) Before pumping the concrete, a bleeding test and a pressure bleeding test were carried out to examine the pumpability of the lightweight concrete.

[0056] The bleeding test was carried out according to JIS A 1123 (Concrete Bleeding Test Method). In the 1123 method, the water that seeps out to the top of a sample poured into a container is absorbed at a specified time interval, and the percentage of the total mass of absorbed water to the mass of water in the sample is calculated as the bleeding rate. If the bleeding rate is high, it is considered that the dispersion of the strong aggregates of cement particles due to the mixing of the concrete has not progressed, and the water and the strong aggregates of cement particles have separated.

[0057] The pressurized bleeding test was conducted according to the JSCE-F502 method (pressurized bleeding test method) of the Japan Society of Civil Engineers' "Standard Specifications for Concrete [Criteria]." The JSCE-F502 method measures the amount of water removed from the bottom of the container while applying pressure from above to the sample placed in the container. The total amount of water removed is measured as the final amount of water removed (ml), and the percentage of the final amount of water removed (mass) relative to the mass of water in the sample is calculated as the final dehydration rate (%). In the pressurized bleeding test, bleeding is carried out under a pressurized environment, so generally, the final amount of water removed is large when the unit water content in the sample is large. However, if strong and large strong aggregates remain, consolidation does not proceed and the final amount of water removed may be small.

[0058] The results of the above tests are shown in Fig. 11. Looking at the results of the pumping test, only Example 3 was unable to be pumped (indicated by the symbol x), but the other Examples 2 and 4-10 had good pumping results (indicated by the symbol o). This shows that the lightweight concrete for the floor slab 31 of this embodiment can be pumped with a unit water content (165 to 175 kg / m) that is generally considered to be low for on-site casting. 3 ) it was confirmed that sufficient pumping performance could be ensured even in the summer and winter without any problems.

[0059] Here, looking at the results of the pressure bleeding test for Example 3, which had a negative pumping result, it can be seen that the final dehydration amount was smaller than those of the other Examples. Therefore, in order to examine the relationship between the pumping property and the results of the bleeding test and the pressure bleeding test, the results of the pumping test were plotted as shown in Figure 12, with the bleeding rate on the horizontal axis and the final dehydration rate on the vertical axis.

[0060] The data points shown in parentheses in Fig. 12 are test results for pumpability, etc., given as a reference example, and are shown in the above-mentioned document by Kishida et al. In this document, concrete containing 1.5 times the standard amount of expansive additive is used, unlike the lightweight concrete for the deck 31 of this embodiment, but the test method for pumpability, etc. is the same as above.

[0061] From Figure 12, we can see that pumpability is good when the bleeding rate is small and the final dehydration rate is relatively large. This is because such a combination of values ​​represents a situation in which there is enough water in the concrete to ensure pumpability, and the concrete is well mixed. Therefore, it is believed that the pumpability of lightweight concrete can be judged by conducting a bleeding test and a pressure bleeding test before pumping the concrete.

[0062] The dotted line in Figure 12 is an example of the pumpability judgment formula y=ax+b, where y is the final dewatering rate and x is the bleeding rate, and the coefficients a and b are values ​​that can be obtained by conducting tests like those described above in advance and accumulating the test results. For example, if a bleeding test and a pressure bleeding test are conducted before pumping concrete, and the relationship in the following formula (3) holds between the final dewatering rate y and the bleeding rate x, it can be determined that the concrete pumpability is good. y ≧ ax + b … (3)

[0063] [Freeze resistance] When using lightweight aggregate that has absorbed water in advance, concrete is produced with the voids inside the lightweight aggregate filled with water. However, in this case, liquid water remains inside the lightweight aggregate even after the concrete hardens, so there is a risk that deterioration will progress from inside the lightweight aggregate when the concrete is subjected to freezing and thawing. In response to this, the freeze-thaw resistance (frost resistance) can be improved by using low-water-content lightweight aggregate as described above, so the results of a freeze-thaw test to examine frost resistance are explained below as Example 11.

[0064] (Example 11 and Comparative Examples 2 to 5) The concrete of Example 11 and Comparative Examples 2 to 5 was prepared by mixing the following materials as water, cement, expansive agent, aggregate (fine aggregate A, B and coarse aggregate A, B), hollow microspheres, and high-performance air entraining water reducing agent and air entraining agent as admixtures according to the ratio shown in Fig. 13. Note that the amounts of high-performance air entraining water reducing agent and air entraining agent shown in Fig. 13 are weight ratios (weight %) to the weight of the binder, and the standard amount of expansive agent is 1 m of concrete. 3 The weight is 20 kg per unit weight. Comparative Examples 2 to 5 are examples that do not use expansive materials, unlike the deck slab 31 of this embodiment.

[0065] Water; Tap water Cement: Ordinary Portland cement manufactured by Denka Co., Ltd. Expansive material: Ettringite-lime composite expansive material (Type 20) manufactured by Denka Co., Ltd. Fine aggregate A: Artificial lightweight aggregate Mesalite fine aggregate (pre-soaked product) Manufactured by Nippon Mesalite Kogyo Co., Ltd. Fine aggregate B: Artificial lightweight aggregate Mesalite fine aggregate (low moisture content) Manufactured by Nippon Mesalite Kogyo Co., Ltd. Coarse aggregate A: Artificial lightweight aggregate Mesalite coarse aggregate (pre-soaked product) Manufactured by Nippon Mesalite Kogyo Co., Ltd. Coarse aggregate B: Artificial lightweight aggregate Mesalite coarse aggregate (low moisture content) manufactured by Nippon Mesalite Kogyo Co., Ltd. Hollow microspheres; KIND Air, manufactured by Denka Co., Ltd. High-performance AE water reducing agent; Super 100pHX manufactured by GCP Applied Technologies Air entraining agent: Master Air 303A, manufactured by BASF Japan Ltd.

[0066] Here, the concrete of Example 11 is intended to improve the frost resistance by using low-moisture coarse aggregate B, while the concrete of Comparative Example 3 is intended to improve the frost resistance of the concrete itself by mixing hollow microspheres in the concrete with the hollow microspheres in the outermost portion, thereby compensating for the amount of air contained in the lightweight aggregate itself with the hollow microspheres. The average particle size of the hollow microspheres is 80 μm, and the apparent density is 0.13 g / cm 3 It is.

[0067] Specimens for use in freeze-thaw tests were prepared using each of the concretes of Example 11 and Comparative Examples 2 to 5. The specimens were in the shape of rectangular columns measuring 100 mm long x 100 mm wide x 400 mm high.

[0068] (Freeze-thaw test) The freeze-thaw test was carried out according to JIS A 1148 A method (underwater freeze-thaw test method). In JIS A 1148 A method, a test specimen placed in a container so that its entire surface is covered with water is subjected to repeated freeze-thaw cycles, and the primary resonance frequency of the flexural vibration according to JIS A 1127 is measured at a specified cycle point.

[0069] The primary resonance frequency was used to calculate the relative dynamic modulus of elasticity, and in this test, the freeze-thaw resistance was evaluated based on the change in the relative dynamic modulus of elasticity. The test was terminated at the end of 300 cycles or when the relative dynamic modulus of elasticity fell to 60% or less, in accordance with JIS A 1148.

[0070] Figure 14 shows the test results. In Comparative Example 2, in which both fine and coarse aggregates were pre-absorbed, the relative dynamic modulus of elasticity fell below 60% after 60 cycles, but in Example 11, in which low-moisture coarse aggregate (coarse aggregate B) was used in addition to the expansive agent, a slight improvement in freeze-thaw resistance was observed, which was about the same as that in Comparative Example 3, in which hollow microspheres were used.

[0071] On the other hand, in Comparative Example 5, in which both the fine and coarse aggregates were in a low moisture state (fine aggregate B, coarse aggregate B), the relative dynamic modulus of elasticity was maintained at 60% or more even at the end of 300 cycles, and the freeze-thaw resistance was higher than in Comparative Example 4, in which only the coarse aggregate was in a low moisture state (coarse aggregate B). This is thought to be because by making the moisture content of not only the coarse aggregate but also the fine aggregate low, no moisture remains in the lightweight aggregate, and the freeze-thaw resistance is greatly improved.

[0072] This relationship is also considered to hold for Example 11, in which expansive material was added, and it is estimated that the freeze-thaw resistance is greatly improved by using low-moisture fine and coarse aggregates. However, as mentioned above, using low-moisture fine and coarse aggregates may make pouring by pressure difficult, and in that case it is preferable to pour by a method other than pressure, such as with a bucket.

[0073] As explained above, in this embodiment, by setting the concrete mix as described above, it is possible to provide a lightweight concrete floor slab that has sufficient strength, i.e., durability. In particular, the lightweight concrete related to the floor slab 31 of this embodiment has sufficient durability even if the amount of expansive agent is about the standard mixing amount, so the amount of expansive agent itself is small, and it is not particularly necessary to use a high-performance admixture such as a high-performance AE water reducing agent, or only a small amount is required, resulting in low costs.

[0074] Furthermore, the lightweight concrete for the deck 31 of this embodiment can ensure sufficient workability even with a relatively small unit water volume as described above, and can improve the durability and achieve high workability of the deck 31. It is highly versatile on-site and can be constructed by anyone. Furthermore, since sufficient workability can be ensured, it can be used without problems when constructing the deck 31 by casting concrete on-site.

[0075] In this embodiment, by determining the pumpability based on the results of the bleeding test and the pressure bleeding test beforehand when pouring concrete, it is possible to omit the test pumping, which contributes to shortening the construction period and improving workability. This concrete pouring method is suitable for lightweight concrete, which may not be pumped well due to blockages, but it can also be applied to other types of concrete, and by determining the pumpability beforehand, it is possible to prevent blockages in concrete.

[0076] Furthermore, by using low-moisture content fine aggregate and coarse aggregate as the lightweight aggregate, the frost resistance of the deck slab 31 can be significantly improved, making it possible to use the deck slab in cold regions.

[0077] Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to the above examples. It is clear that a person skilled in the art can come up with various modified or altered examples within the scope of the technical ideas disclosed in this application, and it is understood that these also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0078] 3: Road structure 31: Floor slab 35: Pavement layer 311: Reinforced concrete

Claims

1. A process of performing a bleeding test and a pressure bleeding test on the lightweight concrete before pumping; A step of substituting the bleeding rate, which is the test result of the bleeding test, and the final dewatering rate, which is the test result of the pressure bleeding test, as two variables of a judgment formula set as a boundary of pumpability from the distribution relationship of the graph of the bleeding rate and the final dewatering rate, and judging the pumpability of the concrete using the judgment formula; If the pumpability of the concrete is judged to be good, pumping and pouring the concrete; A method for pouring concrete comprising the steps of:

2. The concrete contains an expansive material in addition to the lightweight aggregate and cement, The amount of the expanding agent is 0.75 to 1.1 times the standard mixing amount of the expanding agent, 2. The method for pouring concrete according to claim 1, wherein the water-binder ratio of the concrete is 30% by weight or more and less than 38% by weight.

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