Compositions for mortar or concrete, methods for manufacturing mortar or concrete

Abstract

The present invention provides a low-carbon mortar or concrete composition and a method for producing mortar or concrete that exhibits excellent initial strength development, durability, and productivity. [Solution] The composition contains a binder made of blast furnace slag fine powder and rapid-strength Portland cement, water, fine aggregate including blast furnace slag fine aggregate, and a nanoparticle-based rapid-strengthening agent made of calcium silicate hydrate nanoparticles. The mortar or concrete composition is mixed while it is still wet, then wrapped in an insulating material and cured without applying heat to produce mortar or concrete.

Description

[Technical Field]

[0001] This invention relates to a mortar or concrete composition with improved durability using blast furnace slag fine powder and blast furnace slag fine aggregate, and to a method for producing mortar or concrete. [Background technology]

[0002] Conventionally, concrete using blast furnace slag fine powder and blast furnace slag fine aggregate is known to have excellent resistance to freeze-thaw cycles and salt damage (see, for example, Patent Documents 1 to 4).

[0003] On the other hand, precast prestressed concrete products that introduce prestress by the pretensioning method are known (see, for example, JIS A 5373 or Patent Document 5). In this concrete product, the pressure is 35 N / mm² 18 hours after mixing. 2 A material that exhibits a compressive strength no less than [a certain value] is required. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6130767 [Patent Document 2] Patent No. 6262897 [Patent Document 3] Patent No. 6977983 [Patent Document 4] Patent No. 6726941 [Patent Document 5] Japanese Patent Publication No. 2005-248517 [Overview of the project] [Problems that the invention aims to solve]

[0005] The inventor considered enhancing the resistance to freeze-thaw and the resistance to salt damage of the above concrete products by using fine blast furnace slag powder as part of the binder and fine blast furnace slag aggregate as part of the fine aggregate.

[0006] However, as the amount of fine blast furnace slag powder used increased, the compressive strength of the concrete at the initial age tended to decrease.

[0007] Also, generally, anti-setting agents such as sodium gluconate that delay hydration are sprayed on fine blast furnace slag aggregate to prevent consolidation. Due to this effect, when using fine blast furnace slag aggregate, the compressive strength 18 hours after mixing tended to be lower than that using ordinary crushed sand.

[0008] Moreover, in concrete using fine blast furnace slag aggregate, those using early-strength Portland cement as the binder to obtain high compressive strength at a young age tended to be inferior in resistance to freeze-thaw compared to those using ordinary Portland cement.

[0009] Also, in order to increase the compressive strength of concrete at the initial age using fine blast furnace slag powder or fine blast furnace slag aggregate, accelerated curing (e.g., steam curing) with heat application was carried out. However, accelerated curing with heat application often uses fossil fuels such as heavy oil, and there was a problem of a large amount of carbon dioxide being emitted.

[0010] Also, in concrete using fine blast furnace slag aggregate, a long wet curing period was required to provide a predetermined resistance to freeze-thaw without using an AE agent. To shorten the wet curing period, it is effective to use a thickening agent, but even when using a thickening agent, the wet curing period cannot be set to 0 days, and there was a problem that the productivity of the concrete decreased when using a thickening agent.

[0011] Therefore, in a concrete product with enhanced durability using fine blast furnace slag powder and fine blast furnace slag aggregate, without performing accelerated curing with heat application, 35 N / mm after 18 hours from mixing2 It was not easy to achieve a compressive strength not less than this value.

[0012] In order to solve such problems, the inventor of the present invention intensively studied the strength development of concrete using blast furnace slag fine powder and blast furnace slag fine aggregate. As a result, it was found that by using a nano-particle-based early strength agent of calcium silicate hydrate and sealing the heat of hydration of the binder without dissipating it, a predetermined compressive strength can be obtained at a young age.

[0013] Also, it was found that when using blast furnace slag fine aggregate and a nano-particle-based early strength agent of calcium silicate hydrate, even when using early strength Portland cement, a predetermined durability can be obtained with a wet curing period of 0 days.

[0014] The present invention has been made in view of the above, and an object thereof is to provide a low-carbon type composition for mortar or concrete, a method for producing mortar or concrete, which are excellent in initial strength development, durability and productivity.

Means for Solving the Problems

[0015] In order to solve the above-described problems and achieve the object, the composition for mortar or concrete according to the present invention contains a binder composed of blast furnace slag fine powder and early strength Portland cement, water, a fine aggregate containing blast furnace slag fine aggregate, and a nano-particle-based early strength agent composed of nano-particles of calcium silicate hydrate. Although it is effective to use an AE agent to improve productivity, it is not necessary to increase the air content to 3.0% or more for the purpose of improving the resistance to freeze-thaw.

[0016] [[ID=​​​​Furthermore, another method for producing mortar or concrete according to the present invention is characterized by producing mortar or concrete by wet curing or air-dry curing without steam curing. [Effects of the Invention]

[0018] The mortar or concrete composition according to the present invention contains a binder consisting of blast furnace slag fine powder and rapid-strengthening Portland cement, water, fine aggregate including blast furnace slag fine aggregate, and a nanoparticle-based rapid-strengthening agent consisting of calcium silicate hydrate nanoparticles. Therefore, it exhibits excellent initial strength development, resistance to freeze-thaw cycles, and resistance to salt damage. Furthermore, it allows for a shortened wet curing period without the use of thickeners. Thus, it provides the effect of offering a low-carbon mortar or concrete composition with excellent initial strength development, durability, and productivity.

[0019] Furthermore, according to the method for producing mortar or concrete of the present invention, the above-mentioned mortar or concrete composition is mixed while it is still wet, then wrapped in an insulating material, and cured without applying heat to produce mortar or concrete. This method does not rely on accelerated curing by applying heat, and has the effect of producing mortar or concrete with excellent initial strength development and durability. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 shows the relationship between the blast furnace slag fine powder binder ratio (GGBS / B) and the compressive strength 18 hours after mixing. [Figure 2] Figure 2 shows the relationship between ambient temperature and compressive strength 18 hours after mixing. [Figure 3] Figure 3 shows the relationship between the amount of rapid strengthening agent added and the compressive strength 18 hours after mixing. [Figure 4] Figure 4 shows the relationship between the number of insulation sheets and the compressive strength 18 hours after mixing. [Figure 5]Figure 5 shows the relationship between ambient temperature and compressive strength 18 hours after mixing. [Figure 6] Figure 6 shows the relationship between the accumulated temperature and the compressive strength 18 hours after mixing. [Figure 7] Figure 7 shows the resistance to freeze-thaw cycles (relative dynamic modulus) when calcium silicate hydrate nanoparticles are not used as a rapid strengthening agent. [Figure 8] Figure 8 shows the resistance to freeze-thaw cycles (relative dynamic modulus) when using blast furnace slag fine aggregate (BFS) and calcium silicate hydrate nanoparticle-based rapid strengthening agent. [Figure 9] Figure 9 shows the resistance to freeze-thaw cycles (relative dynamic modulus) when using crushed sand and a nanoparticle-based rapid strengthening agent of calcium silicate hydrate. [Figure 10] Figure 10 shows the resistance (relative dynamic modulus) of concrete specimens to freeze-thaw cycles when using blast furnace slag fine powder and rapid-hardening Portland cement, blast furnace slag fine aggregate, and calcium silicate hydrate nanoparticle-based rapid-hardening agent. [Figure 11] Figure 11 shows the results of the apparent diffusion coefficient test. [Figure 12] Figure 12 shows the test results for the water permeability coefficient. [Figure 13] Figure 13 shows the results of the drying shrinkage strain test. [Figure 14] Figure 14 is a photograph showing the steel formwork used for mortar molding. [Figure 15] Figure 15 is a photograph showing the situation where concrete test specimens are placed around the prototype formwork and the entire top surface is covered with a curing sheet. [Modes for carrying out the invention]

[0021] The embodiments of the mortar or concrete composition and the method for producing mortar or concrete according to the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments.

[0022] <Mortar or concrete composition> First, embodiments of the mortar or concrete composition according to the present invention will be described. The mortar or concrete composition according to the embodiment of the present invention contains a binder composed of blast furnace slag fine powder and early-strength Portland cement, water, fine aggregate containing blast furnace slag fine aggregate, and an early-strengthening agent.

[0023] Blast furnace slag is a by-product produced when pig iron is manufactured in a blast furnace, and its main components are CaO, SiO2, Al2O3, and MgO. This blast furnace slag can be used in the form of blast furnace slag fine powder or blast furnace slag fine aggregate. In this embodiment, blast furnace slag fine powder is used as a binder, and blast furnace slag fine aggregate is used as a fine aggregate.

[0024] Blast furnace slag fine powder is obtained by drying and pulverizing blast furnace water-quenched slag obtained by rapidly quenching blast furnace slag with water, and has a specific surface area of 2500 to 10000 cm 2 / g in Blaine value. By using such blast furnace slag fine powder, a mortar or concrete composition excellent in durability can be obtained. When the specific surface area of the blast furnace slag fine powder used is less than 2500 cm 2 / g in Blaine value, the development of initial strength may deteriorate, and the specific surface area is preferably 3,000 cm 2 / g or more in Blaine value, and more preferably 3500 cm 2 / g or more. On the other hand, when the specific surface area exceeds 10,000 cm 2 / g in Blaine value, the cost increases, the heat of hydration increases, and the drying shrinkage strain increases, etc., which may cause initial defects in the concrete. The specific surface area is preferably 10,000 cm 2 / g or less in Blaine value, and more preferably 7000 cm 2 / g or less.

[0025] Blast furnace slag fine aggregate is amorphous blast furnace slag fine aggregate. As amorphous blast furnace slag fine aggregate, for example, granulated blast furnace slag, which is obtained by rapidly cooling blast furnace slag with water, is lightly crushed and an anti-caking agent is added. In the production of granulated blast furnace slag, the temperature of the molten blast furnace slag just before rapid cooling is 1400°C to 1500°C, and rapid cooling causes it to solidify into a glassy (amorphous) state without the atomic arrangement into crystals occurring. The quality of blast furnace slag fine aggregate is specified in JIS A 5011-1.

[0026] Furthermore, blast furnace slag fine aggregate has a density of, for example, 2.5 to 3.0 g / cm³. 3 It is such that the density is 2.5~3.0 g / cm³. 3 By using blast furnace slag fine aggregate within this range, the durability of the resulting mortar or concrete can be improved. The density of the blast furnace slag fine aggregate is 2.5 g / cm³. 3 If the amount is less than 2.55 g / cm³, the porosity of blast furnace slag aggregate may reduce the strength of the mortar or concrete using it. 3 More than 2.90g / cm 3 Preferably, it is 2.80 g / cm³. 3 The following is more preferable: The reason why resistance to freeze-thaw cycles and salt damage is improved by using blast furnace slag fine aggregate is because the blast furnace slag fine aggregate reacts with the cement paste. The blast furnace slag fine aggregate should be tested in accordance with JSCE-C 507, and a higher mass retention rate R7 is preferable, with a rate of 40% or more being more preferable.

[0027] The mass ratio of blast furnace slag fine aggregate (BFS) to fine aggregate (S) (BFS / S) is preferably 0.6 to 1.0. In other words, it is preferable that there are 60 to 100 parts by mass of blast furnace slag fine aggregate (BFS) for every 100 parts by mass of fine aggregate (S). The fine aggregate may contain materials other than blast furnace slag fine aggregate, as long as they do not hinder the effects of the present invention. For example, in addition to blast furnace slag fine aggregate, general fine aggregates such as crushed sand may be used.

[0028] High-early-strength Portland cement has a relatively high C3S content and a large specific surface area (Blaine value) compared to ordinary Portland cement, resulting in superior initial strength development. The quality of high-early-strength Portland cement is specified in JIS R 5210.

[0029] The mass ratio of blast furnace slag powder (GGBS) to binder (B) (GGBS / B) is preferably 0 to 0.6. In other words, it is preferable that there are 0 to 60 parts by mass of blast furnace slag powder (GGBS) per 100 parts by mass of binder (B). In particular, if the blast furnace slag powder-to-binder ratio (GGBS / B) is in the range of 0.2 to 0.5, a mortar or concrete that simultaneously satisfies both strength development and high durability can be obtained. Note that the binder may contain materials other than rapid-hardening Portland cement and blast furnace slag powder, as long as they do not hinder the effects of the present invention.

[0030] The rapid strengthening agent shall be a nanoparticle-based rapid strengthening agent consisting of nanoparticles of calcium silicate hydrate, and rapid strengthening agents mainly composed of calcium aluminate minerals, calcium chloride, nitrites, rhodates, sulfates, etc., which affect the corrosion of steel materials, shall not be used. Here, the nanoparticle-based rapid strengthening agent of calcium silicate hydrate refers to a rapid strengthening agent mainly composed of nanoparticles of calcium silicate hydrate. For example, nanoparticles with an average particle size of several nanometers to several hundred nanometers can be used. The rapid strengthening agent may also be used in liquid form in which these nanoparticles are stably dispersed in a liquid.

[0031] Among mortar or concrete compositions, concrete compositions usually further contain coarse aggregate. For the coarse aggregate, common materials such as crushed sandstone can be used. Preferably, the mass ratio of coarse aggregate (G) to binder (B) (G / B) is 1.0 to 5.0. That is, it is preferable that there are 100 to 500 parts by mass of coarse aggregate (G) for every 100 parts by mass of binder (B).

[0032] Preferably, the amount of water used is such that the mass ratio of water (W) to binder (B) (W / B) is 0.25 to 0.50, that is, 25 to 50 parts by mass of water (W) for every 100 parts by mass of binder (B).

[0033] Furthermore, the mortar or concrete composition of the present invention may contain other components as long as they do not impair the effects of the present invention. For example, it may contain high-performance water-reducing agents, air-entraining agents such as AE agents, defoaming agents, thickening agents, and the like.

[0034] The mortar or concrete composition of the present invention exhibits excellent initial strength development. Specifically, the compressive strength of the mortar or concrete composition of the present invention 18 hours after mixing is 35 N / mm². 2 It is larger and exhibits superior initial strength development.

[0035] Furthermore, the mortar or concrete composition of the present invention exhibits excellent resistance to freeze-thaw cycles. Specifically, in a freeze-thaw test based on the freeze-thaw test method described in JIS A 1148, in which the solution used to immerse the specimen is 10% by mass of saline, the relative dynamic modulus of elasticity or durability index in a specimen prepared with the mortar or concrete composition of the present invention over a predetermined freeze-thaw cycle is greater than that in a specimen prepared with a mortar or concrete composition of the present invention that differs only in that it does not contain blast furnace slag fine powder and blast furnace slag fine aggregate, demonstrating excellent resistance to freeze-thaw cycles.

[0036] Furthermore, the mortar or concrete composition of the present invention exhibits excellent resistance to salt damage. Specifically, the apparent diffusion coefficient of chloride ions after a predetermined soaking period in a specimen prepared with the mortar or concrete composition of the present invention, as obtained by the method for testing the apparent diffusion coefficient of chloride ions in concrete by soaking as described in JSCE-G 572, is smaller than the apparent diffusion coefficient of chloride ions after a predetermined soaking period in a specimen prepared with a mortar or concrete composition of the present invention that differs only in that it does not contain blast furnace slag fine powder and blast furnace slag fine aggregate, demonstrating excellent resistance to salt damage.

[0037] Thus, according to this embodiment, the composition exhibits excellent initial strength development, resistance to freeze-thaw cycles, resistance to salt damage, resistance to moisture penetration, and resistance to drying shrinkage. Furthermore, since the wet curing period can be shortened without the use of thickeners, it offers excellent productivity and contributes to low carbon emissions. Therefore, it is possible to provide a low-carbon mortar or concrete composition with excellent initial strength development, durability, and productivity.

[0038] <Method of manufacturing mortar or concrete> Next, embodiments of the method for producing mortar or concrete according to the present invention will be described.

[0039] The method for producing mortar or concrete according to an embodiment of the present invention involves mixing the above-mentioned mortar or concrete composition while it is still wet, wrapping it in an insulating material, and curing it without supplying heat to produce mortar or concrete. The curing method shall be air curing (air-dry curing) or wet curing, and steam curing shall not be used.

[0040] According to this embodiment, a curing method that does not involve accelerated curing with heat can be used to produce mortar or concrete with excellent initial strength development, resistance to freeze-thaw cycles, resistance to salt damage, resistance to moisture penetration, and resistance to drying shrinkage. Furthermore, since the wet curing period can be shortened without using thickeners, productivity is improved and it contributes to a low-carbon product. Therefore, it is possible to provide a low-carbon type of mortar or concrete with excellent initial strength development, durability, and productivity.

[0041] The mortar or concrete produced in this manner according to the present invention has a compressive strength of 35 N / mm² 18 hours after mixing. 2 Because it does not fall below a certain level and exhibits excellent resistance to freeze-thaw cycles and salt damage, it is effective in reducing carbon emissions and increasing the durability of precast prestressed concrete products. In addition to these applications, it can also be suitably used in sites where resistance to freeze-thaw cycles and salt damage is required, such as coastal structures, marine structures, waterway structures, road structures, retaining wall structures, river structures, and erosion control structures, as well as in the repair or reinforcement of these structures.

[0042] <Verification experiment of the effects of the present invention> Next, we will describe the tests and results that verified the effects of the present invention. Mortar or concrete produced using the mortar or concrete composition according to the present invention exhibits excellent initial strength development, resistance to freeze-thaw cycles, and resistance to salt damage, as described above. The following description shows the tests and results related to these. Figures 1 to 6 show the test results regarding strength development, Figures 7 to 10 show the test results regarding resistance to freeze-thaw cycles, and Figures 11 to 13 show the test results regarding resistance to salt damage.

[0043] Furthermore, the test results using the concrete specimens described below are expected to be similar for mortar specimens made by removing coarse aggregate from concrete, and the test results using the mortar specimens described below are expected to be similar for concrete specimens made by adding coarse aggregate to mortar.

[0044] (Materials used and formulation) Table 1 shows the materials and mix designs used for the mortar or concrete specimens in this test.

[0045] [Table 1]

[0046] In Table 1, Gmax is the maximum aggregate size, W is water, B is binder, and GGBS is blast furnace slag fine powder 4000 (density: 2.89 g / cm³). 3 Brain value: 4150cm 2 / g) or blast furnace slag fine powder 6000 (density: 2.91g / cm³) 3 Brain value: 5840cm 2 HPC is high-early-strength Portland cement (density: 3.13 g / cm³). 3 Brain value: 4600cm 2 ( / g), S is fine aggregate, CS is crushed sand (crushed hard sandstone, surface dry density: 2.59 g / cm³). 3 (Water absorption rate: 1.98%, Coarseness ratio: 2.95), BFS is blast furnace slag fine aggregate (Surface dry density: 2.77 g / cm³) 3 , water absorption rate: 0.23%, coarse grain rate: 1.93, mass residual rate R7: 42.6% based on JSCE-C 507), G is coarse aggregate (hard sandstone crushed stone, maximum dimension: 20 mm, surface dry density: 2.74 g / cm 3 The water absorption rate was 0.65%. The admixtures used were a high-performance water-reducing agent, an air-enhancing agent, and a rapid-starting agent (a nanoparticle-based rapid-starting agent of calcium silicate hydrate). The water-to-binder ratio (W / B) was 33% and 36%, and the unit water content (W) was 160, 162, and 263 kg / m³. 3 For GGBS specimens numbered 2-5, 14-16, 18-20, and 22-24, blast furnace slag fine powder 4000 was used, while for GGBS specimens numbered 8-12 and 26, blast furnace slag fine powder 6000 was used.

[0047] Specimen numbers 1-5 represent the concrete mix used to obtain the test results shown in Figure 1. Specimen numbers 6-7 represent the mortar mix used to obtain the test results shown in Figure 2. Specimen numbers 8-11 represent the mortar mix used to obtain the test results shown in Figures 3-5. Specimen number 12 represents the concrete mix used to obtain the test results shown in Figures 6, 10-12. Specimen numbers 13-16 represent the concrete mix used to obtain the test results shown in Figure 7. Specimen numbers 17-20 represent the concrete mix used to obtain the test results shown in Figure 8. Specimen numbers 21-24 represent the concrete mix used to obtain the test results shown in Figure 9. Specimen numbers 25-26 represent the concrete mix used to obtain the test results shown in Figure 13.

[0048] (Intensity of expression) First, we will explain the tests and results regarding strength development. This test was conducted in accordance with JIS A 1108 (Test method for compressive strength of concrete), and the compressive strength of cylindrical specimens measuring 100 mm in diameter and 200 mm in height was measured 18 hours after the placement (mixing) of mortar or concrete. The specimens were cured in steel formwork from placement until measurement.

[0049] Figure 1 shows the effect of the amount of blast furnace slag powder used on the compressive strength 18 hours after mixing, using concrete specimens (specimen numbers 1-5). Figures 2-5 show the effects of ambient temperature, calcium silicate hydrate nanoparticle rapid strengthening agent, and heat insulating material on the compressive strength 18 hours after mixing, using mortar specimens (specimen numbers 6-11). Figure 6 shows the effect of the cumulative temperature from immediately after mixing to 18 hours later on the compressive strength of a concrete specimen (specimen number 12) 18 hours after mixing.

[0050] As shown in Figure 1, the compressive strength of concrete specimens 18 hours after mixing decreases as the proportion of blast furnace slag powder (GGBS) in the binder (B) increases. Also, as shown in Figure 2, the compressive strength of concrete specimens using blast furnace slag fine aggregate (BFS) 18 hours after mixing is lower than that of specimens using crushed sand. In other words, using blast furnace slag powder and blast furnace slag fine aggregate results in lower compressive strength of concrete 18 hours after mixing compared to concrete that does not use blast furnace slag powder and blast furnace slag fine aggregate.

[0051] As shown in Figure 3, when a calcium silicate hydrate nanoparticle-based rapid strengthening agent is added to a mortar specimen using blast furnace slag fine powder and blast furnace slag fine aggregate, the compressive strength 18 hours after mixing increases in proportion to the amount of calcium silicate hydrate nanoparticle-based rapid strengthening agent used. However, even when 6% of the calcium silicate hydrate nanoparticle-based rapid strengthening agent is added to the binder, the compressive strength remains at 35 N / mm². 2 It can be seen that the required compressive strength has not been reached. In other words, it can be seen that the compressive strength required for precast prestressed concrete products cannot be achieved 18 hours after mixing using conventional manufacturing methods.

[0052] Figure 4 shows the relationship between the number of insulating sheets wrapped around the steel formwork used to form the mortar specimens and the compressive strength 18 hours after mixing, for each percentage of rapid strengthening agent. Figure 14 shows the steel formwork used. In Figure 14, symbol S1 indicates a bottomed cylindrical steel formwork 1 used to form the mortar specimens with a single layer of 7 mm thick sheet-like insulating material 2 wrapped around its outer surface, symbol S2 indicates a double layer, symbol S3 indicates a triple layer, and symbol S4 indicates no insulating material 2 is wrapped. As shown in Figure 4, it can be seen that the compressive strength 18 hours after mixing increases as the number of insulating sheets increases. When the calcium silicate hydrate nanoparticle-based rapid strengthening agent is 3% and 6%, the compressive strength 18 hours after mixing is 35 N / mm when one or more insulating sheets are wrapped around the steel formwork and cured. 2 It can be seen that it surpasses that.

[0053] As shown in Figure 5, if calcium silicate hydrate nanoparticles are used as the binder at 8%, and the insulating material is wrapped in three layers to maintain temperature, the strength reaches 35 N / mm² 18 hours after mixing, even at an ambient temperature of 5°C. 2 It can be seen that the above compressive strength can be obtained.

[0054] Figure 15 shows a setup in which multiple steel formworks 1, each containing concrete (specimen number 12) with a diameter of 100 mm and a height of 200 mm, are placed around a formwork 3 containing a roughly rectangular prototype concrete (specimen number 12) measuring 700 × 1400 × 900 mm. The formworks 3 are then covered with a curing sheet 4 for curing. Figure 6 shows the results of a compressive strength test 18 hours after mixing, when the steel formworks 1 are wrapped with 0, 1, or 2 sheets of insulation material and cured for 18 hours using the method shown in Figure 15. As shown in Figure 6, the cumulative temperature of the concrete poured into the steel formworks 1 increases from the start of mixing to 18 hours, and consequently, the compressive strength of the concrete 18 hours after mixing also increases.

[0055] As in this specimen No. 12, even when blast furnace slag fine powder is used as the binder for 50% and blast furnace slag fine aggregate is used for 100% of the fine aggregate, by using a calcium silicate hydrate nanoparticle-based rapid strengthening agent and simultaneously utilizing the heat of the binder's hydration reaction, a strength of 35 N / mm² was achieved 18 hours after mixing without the need for accelerated curing using heat (such as steam curing). 2 This makes it possible to achieve a compressive strength that does not fall below a certain level.

[0056] Table 2-1 compares the compressive strength test results 18 hours after mixing, categorized by curing method and the presence or absence of rapid-strengthening agent. Case 1 is when concrete specimen number 12 was poured into steel formwork 1, wrapped with one sheet of insulation material, and cured using the method shown in Figure 15. Case 2 is when concrete (specimen number 12) was cured under ambient temperature conditions of 20°C. Case 3 is when concrete without calcium silicate hydrate nanoparticle-based rapid-strengthening agent (specimen number 12 with 0% rapid-strengthening agent) was cured under ambient temperature conditions of 20°C. As shown in this table, in Case 1, the compressive strength 18 hours after mixing was 35 N / mm². 2 In conclusion, in Case 2 and Case 3, the compressive strength 18 hours after mixing was 35 N / mm². 2 It has not reached that point.

[0057] [Table 2-1]

[0058] (Resistance to freeze-thaw cycles) Next, we will describe the tests and results regarding resistance to freeze-thaw cycles. These tests were conducted using 100 × 100 × 400 mm rectangular specimens, in accordance with Method A (Underwater Freeze-Thaw Test Method) described in JIS A 1148 (Test Method for Freeze-Thaw Cycles of Concrete). Saltwater (10% sodium chloride aqueous solution by mass percentage) was used as the freeze-thaw test solution in which the specimens were immersed. Generally, conducting freeze-thaw tests with saltwater provides a more severe test environment than using freshwater.

[0059] Figures 7 to 10 show the test results for resistance to freeze-thaw cycles. Note that the test results in Figures 7 to 9 were obtained using concrete specimens that were cured in air without wet curing, while the test results in Figure 10 were obtained using concrete specimens that were cured for 18 hours using the method shown in Figure 15, followed by water curing for one week.

[0060] Tables 2-2 to 2-5 show the relative dynamic modulus measured for each freeze-thaw cycle. Table 2-2 corresponds to Figure 7, Table 2-3 to Figure 8, Table 2-4 to Figure 9, and Table 2-5 to Figure 10.

[0061] [Table 2-2]

[0062] [Table 2-3]

[0063] [Table 2-4]

[0064] [Table 2-5]

[0065] As shown in Figure 7, when concrete specimens (specimen numbers 13-16) using blast furnace slag fine powder and blast furnace slag fine aggregate, and without using calcium silicate hydrate nanoparticle-based rapid strengthening agents, were subjected to freeze-thaw tests after air curing without wet curing, it can be seen that the relative dynamic modulus of elasticity fell below 60% within 150 cycles, regardless of the amount of blast furnace slag fine powder used (GGBS / B = 0-60%).

[0066] As shown in Figure 8, when concrete specimens (specimen numbers 17-20) using blast furnace slag fine powder and blast furnace slag fine aggregate, along with a nanoparticle-based rapid strengthening agent of calcium silicate hydrate, were subjected to freeze-thaw tests after air curing without wet curing, it was found that the relative dynamic elastic modulus remained at 100% even after 300 freeze-thaw cycles. In other words, the concrete specimens (specimen numbers 17-20) exhibit high resistance to freeze-thaw cycles using saltwater, even with a water curing period of 0 days.

[0067] As shown in Figure 9, even when calcium silicate hydrate nanoparticles are used as a rapid strengthening agent on concrete specimens without blast furnace slag aggregate (specimen numbers 21-24), the relative dynamic modulus falls below 60% within 150 cycles if wet curing is not performed. In other words, the effect of calcium silicate hydrate nanoparticles on the freeze-thaw resistance of concrete without wet curing is only observed when blast furnace slag aggregate is used, and the same effect cannot be obtained when crushed sand is used as the aggregate.

[0068] As shown in Figure 10, when a concrete specimen (specimen number 12) using blast furnace slag fine powder and rapid-hardening Portland cement, blast furnace slag fine aggregate, and calcium silicate hydrate nanoparticle rapid-hardening agent was cured to 18 hours of age using the method shown in Figure 15, and then subjected to a freeze-thaw test after water curing to 7 days of age, it was found that the relative dynamic modulus remained at approximately 100% up to 930 cycles. In this freeze-thaw test, concrete specimens with 0 to 2 layers of insulating material wrapped around the outer surface of the steel formwork of the concrete specimen were tested.

[0069] (Apparent diffusion coefficient) Next, we will describe the tests and results regarding the apparent diffusion coefficient. This test is a test to determine the apparent diffusion coefficient of chloride ions after a 3-month immersion period, as described in JSCE-G 572 (Draft Test Method for Apparent Diffusion Coefficient of Chloride Ions in Concrete by Immersion).

[0070] Figure 11 and Table 3 show the measurement results of the total chloride ion concentration at each immersion depth. The concrete specimens used were those from specimen number 12, in which concrete was poured using blast furnace slag fine powder and rapid-hardening Portland cement, blast furnace slag fine aggregate, and calcium silicate hydrate nanoparticle-based rapid-hardening agent. The steel formwork in which the concrete was poured was wrapped with 0 to 2 layers of insulating material, and the specimens were cured for 18 hours using the method shown in Figure 15, followed by water curing until 7 days of age.

[0071] [Table 3]

[0072] As shown in Figure 11, the apparent diffusion coefficient D ap The largest one is 0.26 cm. 2 / year (with two layers of insulation wrapped around it), the smallest being 0.17cm 2 It can be seen that the amount is very small / year (with one layer of insulation wrapped around it). When the apparent diffusion coefficient of concrete with a water-cement ratio of 33% and using high-early-strength Portland cement is calculated using the prediction formula shown in Reference 1 below, it is 1.36 cm. 2 This is calculated as / year, and in comparison, it can be seen that the apparent diffusion coefficient of the concrete in specimen number 12 is very small.

[0073] [Reference 1] Standard Specifications for Concrete [Design Edition: Standard] (Established in 2022), Japan Society of Civil Engineers Concrete Committee, Subcommittee for Revision of Standard Specifications for Concrete, 2023.

[0074] (Moisture permeability coefficient) Next, we will explain the tests and results regarding the water permeation rate coefficient. This test is for determining the water permeation rate coefficient as described in JSCE-G 582 (Draft Test Method for Water Permeation Rate Coefficient in Concrete Subjected to Short-Term Water Exposure).

[0075] Figure 12 shows the water penetration rate coefficient for a concrete specimen (specimen number 12) made with blast furnace slag fine powder and rapid-hardening Portland cement, blast furnace slag fine aggregate, and calcium silicate hydrate nanoparticle rapid-hardening agent. The specimen was cured for 18 hours using the method shown in Figure 15, and then water-cured until 7 days of age. As shown in this figure, the water penetration rate coefficient is very small, approximately 0.1 mm / √hour. When the water penetration rate coefficient of concrete with a water-cement ratio of 33% and rapid-hardening Portland cement is calculated using the prediction formula shown in Reference 1 above, it is 3.48 mm / √hour. In comparison, the water penetration rate coefficient of the concrete in specimen number 12 is extremely small.

[0076] (Drying shrinkage strain) Next, we will describe the tests and results regarding drying shrinkage strain. This test determined the drying shrinkage strain according to JIS A 1129-3 (Method for measuring length change of mortar and concrete - Part 3: Dial gauge method).

[0077] Figure 13 and Table 4 show the results of measuring drying shrinkage strain in concrete specimens after underwater curing up to 7 days. Specimen No. 26 is a concrete specimen using blast furnace slag fine powder and rapid-hardening Portland cement, blast furnace slag fine aggregate, and calcium silicate hydrate nanoparticle rapid-hardening agent. Specimen No. 25 is a concrete specimen using rapid-hardening Portland cement and crushed sand. In Figure 13, the HPC+GGBS·BFS plot represents specimen No. 26, and the HPC·crushed sand plot represents specimen No. 25.

[0078] [Table 4]

[0079] As shown in Figure 13, when concrete specimens using blast furnace slag fine powder and rapid-hardening Portland cement, blast furnace slag fine aggregate, and a nanoparticle-based rapid-hardening agent of calcium silicate hydrate were cured in water for 7 days and then subjected to a length change test, the magnitude of the drying shrinkage strain at 182 days of drying was 220 × 10⁻⁶. -6 This indicates that the drying shrinkage strain is about half the size of that of a sample using rapid-hardening Portland cement and crushed sand.

[0080] As described above, the mortar or concrete composition according to the present invention contains a binder consisting of blast furnace slag fine powder and rapid-strengthening Portland cement, water, fine aggregate including blast furnace slag fine aggregate, and a nanoparticle-based rapid-strengthening agent consisting of calcium silicate hydrate nanoparticles. Therefore, it exhibits excellent initial strength development, resistance to freeze-thaw cycles, and resistance to salt damage. Furthermore, it allows for a shortened wet curing period without the use of thickeners. Thus, it is possible to provide a low-carbon mortar or concrete composition with excellent initial strength development, durability, and productivity.

[0081] Furthermore, according to the method for producing mortar or concrete of the present invention, the above-mentioned mortar or concrete composition is mixed while it is still wet, then wrapped in an insulating material, and cured without applying heat to produce mortar or concrete. Therefore, mortar or concrete with excellent initial strength development and durability can be produced using a curing method that does not rely on accelerated curing by applying heat. [Industrial applicability]

[0082] As described above, the mortar or concrete composition and the method for producing mortar or concrete according to the present invention are useful for precast prestressed concrete products, and in particular, they are suitable for contributing to the construction of an SDG society because they can improve production efficiency and reduce carbon emissions in the manufacturing process while ensuring high durability. [Explanation of Symbols]

[0083] 1 Steel formwork 2 Heat insulation material 3 Formwork 4. Protective sheet

Claims

1. A composition for mortar or concrete characterized by containing a binder consisting of blast furnace slag fine powder and rapid-strengthening Portland cement, water, fine aggregate containing blast furnace slag fine aggregate, and a nanoparticle-based rapid-strengthening agent consisting of calcium silicate hydrate nanoparticles.

2. A method for producing mortar or concrete, characterized by mixing the mortar or concrete composition described in claim 1 while it is still wet, wrapping it in an insulating material, and curing it without supplying heat to produce mortar or concrete.

3. The method for producing mortar or concrete according to claim 2, characterized in that mortar or concrete is produced by wet curing or air-dry curing without steam curing.

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