Acid resistant concrete, precast concrete, and method for producing acid resistant concrete

Abstract

Provided is highly durable acid resistant concrete. For this reason, acid resistant concrete is produced by mixing with water, an industrial by-product, an alkali stimulant, an expansive additive, a fine aggregate, a coarse aggregate, and a high-range water-reducing admixture; and compacting by centrifugal molding. The industrial by-products include fly ash, ground granulated blast-furnace slag, and silica fume, and alkali stimulants include slaked lime. The industrial by-products may include sewer sludge incineration ash. Further, it may be steam-cured after molding and the preliminary curing time may be 1.5 hours or more.

Description

Acid-resistant concrete, precast concrete, and method for manufacturing acid-resistant concrete

[0001] The present invention relates to acid-resistant concrete, precast concrete, and a method for producing acid-resistant concrete.

[0002] In recent years, repairs, maintenance, and renewals have been carried out on sewer pipes whose service life exceeds 50 years. Even sewer pipes with service lives of less than 50 years are suffering from serious "sulfuric acid deterioration," in which the inside of the pipe corrodes due to hydrogen sulfide. In severe cases, this deterioration has even been reported to cause road collapses. For this reason, highly durable sewer pipes with service lives of 100 years are in demand, and are gaining attention as a new era's need.

[0003] Patent Document 1 describes a corrosion-resistant mortar composition that is a coating mortar capable of protecting concrete and mortar, and that is excellent in plastering workability, pumpability, sagging resistance, adhesion, dimensional stability, and crack resistance, as well as in acid resistance. This corrosion-resistant mortar composition is substantially free of cement polymers and contains (A) cement, (B) ground granulated blast furnace slag, (C) fly ash, (D) an expansive agent, (E) a specific aggregate containing calcium and aluminum as chemical components, and (F) a thickener in specific proportions, and further contains (G) a water-reducing agent, (H) an antifoaming agent, (I) one or more components selected from alkali metal carbonates or formates, (J) an alkali metal sulfate, and (K) one or more organic fibers.

[0004] Japanese Patent Application Laid-Open No. 2017-132667

[0005] Toshiaki Idenoshita, Masami Uzawa, Susumu Yamaguchi, Masahiro Maeda, Hideki Ikawa, and Seiji Hosaka, "Strength Properties and Microstructural Changes of Mortar Mixed with Sewage Sludge Incineration Ash under Various Curing Conditions," Journal of Society of Materials Science, Japan, 2017, Vol. 66, No. 10, pp. 752-757

[0006] However, the corrosion-resistant mortar composition of Patent Document 1 had to be applied separately to the formed concrete product.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide an acid-resistant concrete that does not require coating or the like by solving the above problems.

[0008] The acid-resistant concrete of the present invention is characterized in that it is produced by blending water, industrial by-products, an alkali activator, an expansive additive, fine aggregate, coarse aggregate, and a high-performance water-reducing agent, and compacting the blended mixture by centrifugal molding. The acid-resistant concrete of the present invention is characterized in that the industrial by-products include fly ash, ground granulated blast furnace slag, and silica fume, and the alkali activator includes slaked lime. The acid-resistant concrete of the present invention is produced by blending water at a rate of 170 kg / m3. 3 , the fly ash is 207 kg / m 3 , the ground granulated blast furnace slag was 207 kg / m 3 , the silica fume is 30 kg / m 3 , the slaked lime is 20 kg / m 3 , the expanding material is 30 kg / m 3 , the fine aggregate is 639 kg / m 3 , the coarse aggregate is 959 kg / m 3 and the high-performance water-reducing agent is 5.434 kg / m 3 The acid-resistant concrete of the present invention is characterized by mixing the water at a rate of 90 to 105% by weight, the fly ash at a rate of 10 to 110% by weight, the ground granulated blast furnace slag at a rate of 90 to 190% by weight, the silica fume at a rate of 50 to 130% by weight, the slaked lime at a rate of 50 to 200% by weight, the expansive material at a rate of 60 to 130% by weight, the fine aggregate at a rate of 80 to 125% by weight, the coarse aggregate at a rate of 80 to 125% by weight, and the high-performance water-reducing agent at a rate of 50 to 150% by weight. 3 , the fly ash is 207 kg / m 3 , the ground granulated blast furnace slag was 207 kg / m 3 , the silica fume is 30 kg / m 3 , the slaked lime is 20 kg / m 3 , the expanding material is 30 kg / m 3 , the fine aggregate is 639 kg / m 3 , the coarse aggregate is 959 kg / m 3 and the high-performance water-reducing agent is 5.434 kg / m3 The acid-resistant concrete of the present invention is characterized by mixing, by weight percentage, 90 to 105% of the water, 10 to 110% of the fly ash, 90 to 190% of the ground granulated blast furnace slag, 50 to 130% of the silica fume, 50 to 500% of the slaked lime, 60 to 130% of the expansive material, 80 to 125% of the fine aggregate, 80 to 125% of the coarse aggregate, and 50 to 150% of the high-performance water-reducing agent, with the standard mix ratio being 90 to 105% of the water, 10 to 110% of the fly ash, 90 to 190% of the ground granulated blast furnace slag, 50 to 130% of the silica fume, 50 to 500% of the slaked lime, 60 to 130% of the expansive material, 80 to 125% of the fine aggregate, 80 to 125% of the coarse aggregate, and 50 to 150% of the high-performance water-reducing agent, and is produced by vibratory molding by mixing water, industrial by-products, an alkali stimulant, an expansive material, fine aggregate, coarse aggregate, and a high-performance water-reducing agent, the industrial by-products including fly ash, ground granulated blast furnace slag, and silica fume, the alkali stimulant including slaked lime, and the water at a rate of 170 kg / m 3 , the fly ash is 207 kg / m 3 , the ground granulated blast furnace slag was 207 kg / m 3 , the silica fume is 30 kg / m 3 , the slaked lime is 20 kg / m 3 , the expanding material is 30 kg / m 3 , the fine aggregate is 639 kg / m 3 , the coarse aggregate is 959 kg / m 3 and the high-performance water-reducing agent is 5.434 kg / m 3 The acid-resistant concrete of the present invention is characterized by mixing, by weight percentage, 90 to 105% of the water, 10 to 110% of the fly ash, 90 to 190% of the ground granulated blast furnace slag, 50 to 130% of the silica fume, 50 to 500% of the slaked lime, 60 to 130% of the expansive agent, 80 to 125% of the fine aggregate, 80 to 125% of the coarse aggregate, and 50 to 150% of the high-performance water-reducing agent, with 26 kg / m of sewage sludge incineration ash as the industrial by-product. 3The acid-resistant concrete of the present invention is characterized in that the sewage sludge incineration ash is blended in a ratio of up to 200% by weight, based on a standard blending ratio of 100% to 100% by weight. The acid-resistant concrete of the present invention is characterized in that it is steam-cured after molding, and the pre-steam curing time is 1.5 hours or more. The acid-resistant concrete of the present invention is blended with water, industrial by-products, an alkali activator, an expansive additive, fine aggregate, coarse aggregate, and a high-performance water-reducing agent, and is cast on-site, the industrial by-products including fly ash, ground granulated blast furnace slag, and silica fume, the alkali activator including slaked lime, and the water is poured at a rate of 170 kg / m 3 , the fly ash is 207 kg / m 3 , the ground granulated blast furnace slag was 207 kg / m 3 , the silica fume is 30 kg / m 3 , the slaked lime is 20 kg / m 3 , the expanding material is 30 kg / m 3 , the fine aggregate is 639 kg / m 3 , the coarse aggregate is 959 kg / m 3 and the high-performance water-reducing agent is 5.434 kg / m 3 The standard blending ratio is 90 to 105% by weight of the water, 10 to 110% by weight of the fly ash, 90 to 190% by weight of the ground granulated blast furnace slag, 50 to 130% by weight of the silica fume, 50 to 500% by weight of the slaked lime, 60 to 130% by weight of the expanding agent, 80 to 125% by weight of the fine aggregate, 80 to 125% by weight of the coarse aggregate, and 50 to 150% by weight of the high-performance water-reducing agent. 3 The present invention is characterized in that the sewage sludge incineration ash is mixed in an amount of up to 200% by weight, with the standard mix being 100%. The precast concrete of the present invention is produced using the acid-resistant concrete. The precast concrete of the present invention is a sewer pipe. The method for producing acid-resistant concrete of the present invention is characterized in that water, industrial by-products, an alkali activator, an expansive additive, fine aggregate, coarse aggregate, and a high-performance water-reducing agent are mixed, and the mixture is compacted by centrifugal molding, vibration molding, or poured on site.

[0009] According to the present invention, by blending water, industrial by-products, an alkali stimulant, an expansive agent, fine aggregate, coarse aggregate, and a high-performance water-reducing agent and compacting them using centrifugal molding, it is possible to provide acid-resistant concrete that does not require coating or the like and has a long service life.

[0010] 1 is a photograph showing the slump flow of the mixture according to Example 1 of the present invention. 2 is a photograph of the appearance of a centrifugal hardened body and centrifugal molding according to Example 1 of the present invention. 3 is a graph showing the setting time of the mixture according to Example 1 of the present invention. 4 is a graph showing the change in compressive strength of a vibration-molded hardened body according to Example 1 of the present invention. 5 is a graph showing the change in compressive strength of a centrifugal-molded hardened body according to Example 1 of the present invention. 6 is a graph showing the strength ratio of vibration molding to centrifugal molding according to Example 1 of the present invention. 7 is a photograph of a vibration-molded hardened body according to Example 1 of the present invention after a sulfuric acid resistance test. 8 is a graph showing the results of a sulfuric acid resistance test according to Example 1 of the present invention. 9 is a photograph of a centrifugal-molded hardened body according to Example 1 of the present invention after a sulfuric acid resistance test. 10 is a graph showing the results of a sulfuric acid resistance test according to Example 1 of the present invention. 11 is a graph showing the relationship between the addition rate and compressive strength for a standard blend of the mixture according to Example 1 of the present invention. 12 is a photograph of a sulfuric acid resistance test according to Example 2 of the present invention. 13 is a graph showing the results of a sulfuric acid resistance test according to Example 2 of the present invention. 14 is a graph showing the results of a strength development test according to Example 2 of the present invention. 2 is a graph showing the results of a strength development test for Example 2 of the present invention. FIG. 3 is a graph showing the results of a compressive strength test for the cylindrical hardened body and the centrifugal hardened body for Example 2 of the present invention. FIG. 4 is a graph showing the results of a compressive strength test for the cylindrical hardened body and the centrifugal hardened body for Example 2 of the present invention. FIG. 5 is a graph showing the results of a compressive strength test depending on the amount of calcium hydroxide added for Example 2 of the present invention. A conceptual diagram of a simple accelerated carbonation test device for Example 2 of the present invention. FIG. 6 is a graph showing the results of a carbonation inhibition effect test for Example 2 of the present invention. A photograph of a carbonation inhibition effect test for Example 2 of the present invention. FIG. 7 is a graph showing the results of a compressive strength test for an actual product of a vibration-molded cylindrical hardened body for Example 2 of the present invention. A flow chart showing the manufacturing process of a hume pipe for Example 2 of the present invention. A photograph of an external pressure test for an actual product of a centrifugal hardened body for Example 2 of the present invention. FIG. 8 is a graph showing the results of an external pressure test for Example 2 of the present invention.

[0011] First Embodiment The inventors of the present invention have completed the present invention as a result of extensive experimentation and development aimed at creating a highly durable sewer pipe that has excellent acid resistance, including sulfuric acid resistance, and is expected to have a service life of 100 years. The acid-resistant cement of this embodiment does not use any Portland cement, but is made from industrial by-products that are centrifugal molded into a hardened body, making it applicable to concrete products that require high durability.

[0012] The acid-resistant concrete of the present invention is characterized in that it is produced by blending water, industrial by-products, an alkali stimulant, an expansive additive, fine aggregate, coarse aggregate, and a high-range water-reducing agent, and then compacting the mixture using centrifugal molding.

[0013] Of these, the water used in the acid-resistant concrete of this embodiment is not particularly limited and may be tap water. The pH and other parameters of the water according to this embodiment are also arbitrary.

[0014] The acid-resistant concrete of this embodiment is characterized in that the industrial by-products contain fly ash, ground granulated blast furnace slag, and silica fume.

[0015] The fly ash according to the present embodiment is polazon coal ash (fly ash) for concrete, which is collected by a dust collector from pulverized coal combustion in a thermal power plant. Examples of the fly ash according to the present embodiment include fly ash type II specified in JIS A 6201 or a similar product, with a density of 2.20 g / cm. 3 Since fly ash is primarily composed of silica and alumina, it hardens through the pozzolanic reaction that produces calcium silicate hydrate and the like when treated with an alkaline activator.

[0016] The ground granulated blast furnace slag according to this embodiment is a by-product of the pig iron manufacturing process. This ground granulated blast furnace slag is preferably, for example, ground granulated blast furnace slag having a specific surface area of ​​4000 and a fineness specified in JIS A 6206. In addition, the density is 2.91 g / cmg / cm. 3Ground granulated blast furnace slag also hardens due to its "latent hydraulic property," which is that it hardens by generating calcium silicate hydrate and calcium aluminate hydrate in the presence of an alkaline stimulant.

[0017] The silica fume according to this embodiment is mostly amorphous and spherical silica (SiO2) collected as dust in the exhaust gas from an electric arc furnace. This silica fume has a density of 2.30 g / cm3 as specified in JIS A 6207. 3 Silica fume is preferably used to increase the density and strength of the hardened body after centrifugation.

[0018] In addition, the industrial by-product of this embodiment may further contain sewage sludge incineration ash. As this sewage sludge incineration ash, it is preferable to use "super ash" obtained by adjusting the particle size of sewage sludge incineration ash, as described in Non-Patent Document 1.

[0019] The acid-resistant concrete of this embodiment preferably contains slaked lime as an alkali stimulant. For example, calcium hydroxide (Ca(OH)2) conforming to JIS R9001 Special No. is preferably used as the slaked lime. The density of the slaked lime is 2.30 g / cm3. 3 This alkali activator makes it possible to harden fly ash and ground granulated blast furnace slag without using any conventional Portland cement.

[0020] The expansive material according to this embodiment is a powdery material that expands when moisture is supplied, reducing cracks caused by drying shrinkage. Examples of the expansive material according to this embodiment include lime-based expansive materials, ettringite-based (calcium sulfoaluminate-based) expansive materials, and ettringite-quicklime composite expansive materials. Of these, it is preferable to use a lime-based expansive material as the expansive material according to this embodiment. It is also preferable that the expansive material conforms to the quality specified in, for example, Japanese Industrial Standards JIS A 6202.

[0021] In addition, as the fine aggregate according to this embodiment, a general fine aggregate such as crushed sand can be used. This fine aggregate corresponds to JIS A 5005 crushed sand (hard sandstone) and has a density of 2.62 g / cm 3 As the fine aggregate, slag-based aggregate, for example, fine aggregate produced from granulated blast furnace slag, electric furnace oxidized slag aggregate, etc. can also be used.

[0022] Furthermore, the coarse aggregate according to this embodiment can be a general coarse aggregate such as sandstone. This coarse aggregate corresponds to JIS A 5005 crushed stone 2005 (hard sandstone), for example, and has a density of 2.67 g / cm 3 It is preferable that the thickness is about 1 / 2 mm.

[0023] The high-performance water-reducing agent of the present embodiment is a chemical admixture that significantly reduces the unit water content without affecting the consistency, or significantly increases the slump without affecting the unit water content. The high-performance water-reducing agent of the present embodiment is, for example, a chemical admixture that corresponds to JIS A 6204, and is, for example, a polycarboxylic acid-based admixture having a density of 1.00 g / cm 3 It is preferable to use a material of this order.

[0024] In addition, the acid-resistant concrete of this embodiment has a water content of 170 kg / m 3 , fly ash 207 kg / m 3 , ground granulated blast furnace slag 207 kg / m 3 , silica fume 30 kg / m 3 , slaked lime 20 kg / m 3 , expanding material 30 kg / m 3 , fine aggregate 639kg / m 3 , coarse aggregate 959 kg / m 3 , and high-performance water-reducing agent 5.434 kg / m 3 The standard formulation is as follows.

[0025] Of these, it is preferable to mix 90 to 105% of water, with the standard mix being 100% by weight. 3 ~175 kg / m 3It is preferable to mix water of this ratio. This ratio allows for good sludge water discharge. If it is less than 90%, the concrete becomes non-sludge, the centrifugal compaction property decreases, and the final strength of the concrete product decreases. If it is more than 105%, the sludge water increases and the strength decreases.

[0026] Similarly, fly ash is preferably blended in a ratio of 10 to 110%. While strength gradually improves with decreasing blending ratio, the amount of ground granulated blast furnace slag used increases, so a lower limit of approximately 10% is preferred. Blending above 110% is undesirable due to decreased strength. Ground granulated blast furnace slag is preferably blended in a ratio of 90 to 190%. Reducing the blending ratio increases the amount of fly ash and decreases strength, so a lower limit of approximately 90% is preferred. Conversely, while strength gradually improves with increasing blending ratio, the amount of fly ash decreases, so a blending upper limit of approximately 190% is preferred. Super ash is preferably blended in a ratio of 0 to 200%. While 0% super ash is acceptable, reducing the blending ratio improves the strength of the hardened body. Conversely, blending above 200% is undesirable due to a significant decrease in the strength of the hardened body. Furthermore, it is preferable to mix silica fume at a ratio of 50 to 130%. This ratio makes it possible to achieve densification and improved strength of the hardened body after centrifugation. If it is less than 50%, the brittle layer on the inner surface will disappear, but densification and improved strength will not be achieved. If it is mixed in excess of 130%, the brittle layer on the inner surface of the hardened body will increase, reducing its performance as a sewer pipe and preventing improved strength. In other words, the mixing ratio of industrial by-products in this embodiment is such that fly ash and ground granulated blast furnace slag are the main components, with silica fume mixed in. Furthermore, super ash may or may not be mixed in.

[0027] Furthermore, it is preferable to mix slaked lime in a ratio of 50 to 200%. Mixing less than 50% is not preferable because strength decreases. Mixing more than 200% does not improve strength. However, as described in the second embodiment below, mixing more than 200% slaked lime provides a carbonation suppression effect. It is preferable to mix expansive additive in a ratio of 60 to 130%. If it is less than 60%, the shrinkage crack prevention effect becomes insufficient. Even if it is more than 130%, the shrinkage crack prevention effect does not improve. It is preferable to mix fine aggregate in a ratio of 80 to 125%. If it is less than 80%, the surface of the hardened body becomes rough due to the small amount of fine aggregate and the excess of coarse aggregate, which is not preferable, and therefore, strength decreases. If it is more than 125%, the fine aggregate and water increase, which is not preferable, and strength decreases. It is also preferable to mix coarse aggregate in a ratio of 80 to 125%. If it is less than 80%, the fine aggregate and water will increase, which is not preferable, as this will reduce strength. If it is more than 125%, the coarse aggregate will be too much and the fine aggregate will be too little, resulting in a rough surface of the hardened body and reduced strength, which is not preferable. In addition, it is preferable to mix the high-performance water-reducing agent in a ratio of 50 to 150%. If it is less than 50%, the water will increase and the strength of the product will decrease, which is not preferable. If it is more than 150%, it will be over-added, which will result in excessive fluidity, further delay in setting, reduced strength, and increased costs, which is not preferable. In this embodiment, the high-performance water-reducing agent is preferably used as an internal replacement for water.

[0028] Furthermore, the acid-resistant concrete according to this embodiment is preferably compacted by centrifugal compaction. In this centrifugal compaction, a mixture of water, industrial by-products, alkali stimulants, expansive additives, fine aggregates, coarse aggregates, and a high-performance water-reducing agent (hereinafter simply referred to as the "mixture"), blended in the above-described proportions, is filled into a centrifugal compaction formwork, which is then rotated at high speed on a molding machine. Finally, the formwork is compacted at an acceleration of approximately 30 to 50 G using centrifugal force, and excess water is discharged as sludge. To ensure proper drainage of excess water and dense compaction, the acceleration may be increased in several stages. For example, compaction in these stages may be performed at 5 G, 15 G, and 35 G for 1 minute, 1 minute, and 7 minutes, respectively. By producing the acid-resistant concrete according to this embodiment using centrifugal compaction, not only the strength but also the acid resistance of the concrete is improved, and the steam curing time is shortened, enabling the production of high-performance sewer pipes.

[0029] The acid-resistant concrete of this embodiment is also characterized by being steam-cured after molding, with a pre-curing time of 1.5 hours or more. Precast concrete is sometimes steam-cured to shorten the time until demolding and increase production efficiency. In this case, it is preferable to adjust the steam-curing conditions, such as pre-curing time, temperature rise (heating), maximum temperature, holding time, and cooling method, depending on the target product and formulation conditions. The pre-curing time is the time from water injection to the start of temperature rise. In this embodiment, for example, the pre-curing time is 1.5 to 4 hours, the temperature rise rate is 15 to 25°C / hour, and the concrete is held at 60 to 75°C for 3 to 5 hours or more, followed by gradual cooling to laboratory temperature and air curing. Steam curing under these conditions accelerates the setting and hardening (strength development) of the mixture, thereby increasing production efficiency. Here, the pre-curing time has a particularly large impact on the steam curing of the mixture of this embodiment. As explained below, centrifugal molding makes it possible to produce concrete with sufficient strength and excellent acid resistance even if the pre-setting time is less than 6 hours, as long as it is 1.5 hours or more.

[0030] Furthermore, the slump flow of the acid-resistant concrete according to this embodiment is preferably about 650±50 mm. In other words, the fresh properties of the mixture of this embodiment are high-fluidity. This improves the filling ability into the formwork during molding, allows excess water to be smoothly drained as sludge water, and enables good compaction. Furthermore, the weight ratio of water to the mixture (hereinafter simply referred to as the "water-powder ratio") is about 20-60%.

[0031] The air content of the acid-resistant concrete according to this embodiment is preferably 2.0±1.5%, i.e., 0.5 to 3.5%. This allows for improved workability while achieving the desired strength. In this embodiment, the air content can be adjusted using an air entraining (AE) agent or other air content regulator. Examples of AE agents include anionic, cationic, nonionic, and amphoteric surfactants. Examples of anionic surfactants include resin-based, alkylbenzene sulfonate-based, and higher alcohol ester-based surfactants. In this embodiment, it is particularly preferable to use a modified rosin acid compound-based anionic surfactant. It is also possible to use an AE water-reducing agent that has the properties of both an AE agent and a water-reducing agent.

[0032] The acid-resistant concrete according to this embodiment may also contain fibers, such as vinylon fibers, acrylic fibers, and carbon fibers. Zeolite, siliceous fine powder, calcium carbonate, clay minerals such as bentonite, gypsum, and calcium silicate may also be added.

[0033] In addition, the acid-resistant concrete according to this embodiment may contain other additives such as fluidizing agents, retarders, waterproofing admixtures, moisture-proofing admixtures, foaming agents, thickeners, antifreeze agents, colorants, workability enhancers, antislip agents, antifoaming agents, setting regulators, shrinkage reducers, cement accelerators, polymer emulsions, etc.

[0034] Furthermore, the acid-resistant concrete according to this embodiment is suitable for use in the production of precast concrete. This precast concrete is preferably a Hume pipe. Furthermore, this Hume pipe can be used as a highly durable sewer pipe. By configuring it as described above, the acid-resistant concrete according to this embodiment can exhibit sufficient acid resistance. Furthermore, it can improve the production efficiency when producing concrete products in a dedicated factory. Therefore, the acid-resistant concrete according to this embodiment can be particularly suitable for producing sewer pipes. Furthermore, conventional sewer pipes include Hume pipes, ceramic pipes, polyvinyl chloride pipes, etc., and each sewer pipe has a specific use. In contrast, the precast concrete according to this embodiment is highly durable and can be used in places where ceramic pipes, etc., are required.

[0035] The above-described configuration can achieve the following benefits. Conventional sewer pipes have primarily been reinforced concrete pipes known as Hume pipes. These reinforced concrete and mortar materials consist of water, cement, and aggregate, and harden through a hydration reaction. Therefore, their use in sewer pipes has led to serious problems, including "sulfuric acid deterioration," in which hydrogen sulfide corrodes the pipe interior, making repairs time-consuming. Hume pipes have a service life of approximately 50 years, and in recent years, maintenance and renewal of sewer pipes, which rapidly spread during the high-growth period of the Showa era, has been underway. Even when the service life of Hume pipes is less than 50 years, hydrogen sulfide generated within the pipe can cause corrosion and deterioration (sulfuric acid deterioration), and in severe cases, this can lead to road subsidence. However, applying mortar such as that described in Patent Document 1 or sulfate-resistant ordinary Portland cement for this maintenance is costly. For this reason, there has been a demand for acid-resistant concrete, a hardened product with high acid resistance. In contrast, the acid-resistant concrete of this embodiment uses a mixture containing industrial by-products, primarily fly ash and ground granulated blast furnace slag, and an alkali irritant, resulting in improved chemical resistance and acid resistance compared to conventional sulfuric acid-resistant ordinary Portland cement. Specifically, as shown in Example 1 below, in a sulfuric acid resistance test in which the concrete was immersed in a 5% sulfuric acid aqueous solution for 28 days, the sulfuric acid resistance (mass change) of specimens made by vibration molding the sulfuric acid-resistant ordinary Portland cement was -32%, indicating severe sulfuric acid deterioration. In contrast, specimens made by vibration molding the acid-resistant concrete of this embodiment showed a slight expansion of +1.2% in the hardened body, but were generally in good condition.

[0036] Furthermore, the acid-resistant concrete of this embodiment undergoes centrifugal molding to densify and restrain the concrete, thereby preventing expansion as occurs with vibration molding and further enhancing durability. As a result of this centrifugal molding, as shown in Example 1 described below, a hardened body obtained by centrifugally molding sulfate-resistant ordinary Portland cement exhibited severe sulfuric acid degradation and aggregate exposure at -16%. In contrast, the sulfuric acid resistance (mass change rate) of a hardened body obtained by centrifugally molding the acid-resistant concrete of this embodiment was -0.8%, indicating a generally healthy condition. In other words, compaction and manufacturing by centrifugal molding enables the production of sewer pipes with sulfuric acid resistance and high durability, reducing the effort required for repairs. Furthermore, centrifugal molding of the acid-resistant concrete of this embodiment shortens the steam curing time (pre-setting time) compared to vibration molding, enabling the production of precast concrete products within a practical timeframe. Specifically, the compressive strength was 40 N / mm at 28 days. 2 As described above, it is possible to manufacture a Hume pipe having excellent sulfuric acid resistance.

[0037] Furthermore, in recent years, global warming countermeasures have come to be recognized as a common global issue, and the severity of the issue is increasing by the minute. For this reason, countries around the world have already begun full-scale efforts to reduce greenhouse gases such as CO2. Because cement is used in Hume pipes, a large amount of CO2 is emitted during cement production. In contrast, the acid-resistant concrete of this embodiment does not use any Portland cement, making it possible to provide an ecological product that effectively utilizes industrial by-products. This contributes to consideration for the global environment and contributes to the reduction of CO2 emissions.

[0038] The acid-resistant concrete according to this embodiment can be used for precast concrete manufactured by centrifugal molding, in addition to Hume pipes. For example, the acid-resistant concrete according to this embodiment is not only resistant to sulfuric acid but also has durability against other acids such as hydrochloric acid, and therefore can be used in power plants, factories, various production and manufacturing facilities, etc.

[0039] In addition, industrial by-products other than fly ash, ground granulated blast furnace slag, sewage sludge incineration ash, and silica fume can also be used in this embodiment. For example, incineration ash from biomass power plants, soot dust, and mineral refining residues containing Ca, Si, and various inorganic metals can also be used. Furthermore, alkali stimulants other than slaked lime can also be used, such as alkali metal hydroxides such as sodium hydroxide, alkali metal hydrates, and gypsum.

[0040] Second Embodiment In the first embodiment described above, Ca(OH)2 (calcium hydroxide, slaked lime) is used in a standard blend of 20 kg / m 3 The content range is 50 to 200% by weight (10 to 40 kg / m 3 In contrast to this, the acid-resistant concrete according to the second embodiment of the present invention is prepared by blending a larger amount of slaked lime in the blending ratio of the first embodiment described above. In this embodiment, the amount of slaked lime is 50 to 500% (10 to 100 kg / m 3 ) is preferably mixed in the ratio. As the amount of calcium hydroxide mixed in increases, the carbonation depth of the hardened body decreases significantly. In other words, increasing the amount of calcium hydroxide added will have a carbonation suppression effect. This effect will be shown in the results of a carbonation suppression effect test using a simple accelerated carbonation test device in Example 2 described below.

[0041] Furthermore, the acid-resistant concrete of this embodiment can be used as a precast concrete product by vibration molding in addition to the centrifugal molding described above. Examples of vibratory molded products include box culverts and manholes. Both products can be manufactured using the same manufacturing process as precast concrete products such as Hume pipes. In other words, they can be manufactured simply by replacing centrifugal molding with vibration molding. Therefore, the mixture of this embodiment can also be applied to the manufacture of vibratory molded precast concrete products.

[0042] In this case, the acid-resistant concrete of this embodiment may have different mix softness requirements depending on the product to which it is applied. In this case, simply fine-tuning the ratio of water (W) to total powder (P) in the mixture (W / P) to correspond to the ratio of water (W) to cement (C) in concrete (W / C) is sufficient. Furthermore, by appropriately adjusting the fine aggregate ratio (S / a) and the amount of admixture (Ad) added, the fresh properties of the mixture (slump: SL and air content: Air) can be tailored to the required performance of the product to be applied. When applying the mixture of this embodiment to an actual product, it is preferable to use the mix shown in Table 8 of Example 2, which will be described later. Table 8 shows mix examples for when the mixture of this embodiment is applied to a centrifugally molded product (Hume pipe) and when it is applied to a vibratory molded product (box culvert). As shown in Table 8, the mixture of this embodiment can also be poured on-site if appropriate curing methods and temperature control are implemented.

[0043] The present invention will now be further described by way of examples with reference to the drawings, but the following specific examples are not intended to limit the present invention.

[0044] [Acid Resistance in Standard Mix] (Summary) The mixture for producing the acid-resistant concrete of this example (hereinafter simply referred to as "this mixture") was the subject of this experiment. Using this mixture, hardened bodies (hereinafter simply referred to as "hardened bodies") were produced by centrifugal molding and vibration molding. Test specimens were manufactured under five steam curing conditions to confirm their strength development. Mortar setting times for this mixture were also evaluated using the Proctor penetration resistance test to confirm the initial and final setting times. For chemical resistance, sliced ​​test specimens (specimens) taken from hardened mortar bodies made by vibration molding and centrifugally molding the mixture were immersed in a 5% aqueous sulfuric acid solution, and their sulfuric acid resistance was compared with that of test specimens made from ordinary Portland cement (hereinafter referred to as "OPC").

[0045] (Materials Used) The types and qualities of the materials used in this example are as shown in Table 1 below. The materials used were six types in total: four types of industrial by-products consisting of fly ash, ground granulated blast furnace slag, super ash, and silica fume; calcium hydroxide (slaked lime) as an alkaline stimulant that corresponds to JIS R9001 Special; and an expansive material for preventing shrinkage cracks that corresponds to JIS A6202. These were then mixed with aggregates (coarse aggregate, fine aggregate), water, and a high-performance water-reducing agent to form the mixture.

[0046]

[0047] (Mixture of this mixture) The fresh properties of this mixture were a high-fluidity type with a slump flow of 650±50 mm, as shown in Figure 1. This was expected to significantly affect the results compared to vibration molding. Furthermore, the air content of this mixture was set at a target value of 2.0±1.5%, based on the actual air content measured when fresh after repeated test mixing. The mix composition was set at a water-powder ratio (W / P) of 34.0% and a fine aggregate ratio of 41.0%, as shown in Table 2 below. Super ash was used to replace fine aggregate in an amount equivalent to 5% of the total powder amount.

[0048]

[0049] (Method of Forming Hardened Body) After kneading the mixture, a hardened body was produced by vibration molding and centrifugal molding. For vibration molding, the fresh mixture was filled into a tinplate cylindrical mold (φ100 × 200 mm) in two layers and compacted in two layers while vibrating with a table vibrator to produce a cylindrical hardened body. For centrifugal molding, the fresh mixture was filled into a centrifugal molding mold (φ200 × 300 mm), and the mold was rotated at high speed on a molding machine to compact the mixture at an acceleration of nearly 40 G using centrifugal force. Excess water in the mixture was discharged as sludge water. The acceleration and molding time shown in Table 3 below were used to compact the mixture by increasing the acceleration in several stages, producing a centrifugal hardened body.

[0050]

[0051] Figures 2(a) and (b) show the external appearance of the produced centrifugal hardened body. Figure 2(c) shows the centrifugal compaction process. During centrifugal compaction, the excess water in the mixture was smoothly drained as sludge due to the acceleration G. As a result, the thickness of the brittle layer inside the centrifugal hardened body was 0 mm, and good compaction properties were obtained. In addition, the outer surface of the hardened body became a very dense hardened body due to the centrifugal force.

[0052] (Setting time) It was assumed that the hardening reaction of this mixture would take a long time to set under natural conditions. For this reason, the initial and final setting times were confirmed using a Proctor penetration resistance test as a setting test. The mortar mixture used in this setting test was the same as the mixture shown in Table 2, but with the coarse aggregate removed. As shown in Figure 3, the initial setting time of this mixture was approximately 14 hours and the final setting time was approximately 19 hours. This is thought to be due to the pozzolanic reaction and latent hydraulic properties.

[0053] (Steam Curing Conditions) Based on the setting test results, the effect of the pre-curing time in steam curing on the strength development of this mixture was confirmed to determine the steam curing conditions (pre-curing time) that are effective for the strength development of the hardened body. In this example, the pre-curing time, which is the time from water injection to the start of temperature rise, was 4 hours, the temperature rise rate was 20°C / h, the maximum temperature was 65°C, the holding time was 4 hours, and the gradual cooling was by natural temperature decrease. In this case, the pre-curing time was divided into five levels as shown in Table 4 below. That is, the pre-curing time was 0.5 hours (30 minutes), 1.5 hours, 3.0 hours, 6.0 hours, and 24.0 hours, and the other steam curing conditions were the same.

[0054]

[0055] (Compressive Strength) Table 5 below shows the test results of compressive strength of the hardened bodies, divided into vibration molding and centrifugal molding, and shown by pre-setting time and material age.

[0056]

[0057] The results are shown in graphs in Figure 4 for vibration molding and in Figure 5 for centrifugal molding. In each graph, the horizontal axis represents pre-setting time, and the vertical axis represents compressive strength (N / mm 2) and δ in each bar indicates the material age (days). This clarifies the difference between vibration molding and centrifugal molding. Looking at the effect of pre-setting time, compressive strength at the initial material age up to 14 days is low with pre-setting time of 0.5 hours, and this is particularly noticeable with vibration molding at an age of 1 day. A similar trend is observed with pre-setting time of 1.5 hours and pre-setting time of 3.0 hours, with only a small difference, and compressive strength fluctuates with vibration molding at an age of 1 day. In contrast, with pre-setting time of 6.0 hours, compressive strength generally remains stable compared to those with shorter pre-setting times, and with centrifugal molding, it reaches 40 N / mm at an age of 28 days. 2 Furthermore, the compressive strength was at its highest level when the pre-setting time was 24.0 hours. Based on the results of the setting test mentioned above, this is presumed to be the effect of ensuring a sufficient pre-setting time longer than the initial setting time of 14 hours for this mixture. In this way, centrifugal molding is not as affected by the pre-setting time as vibration molding, and the compressive strength is generally 5 N / mm 2 It reached a fairly high level.

[0058] Next, Figure 6 shows the strength ratios of vibration molding compared to centrifugal molding (100%) under various conditions, based on the results described above. The strength ratios indicate that the compressive strength of the hardened body reacts sensitively to the pre-setting time in vibration molding. For short pre-setting times such as 0.5, 1.5, and 3.0 hours, the strength ratios were generally around 85%. In contrast, for pre-setting times of 6.0 hours or longer, the strength ratios exceeded 90% up to 14 days, and the difference with centrifugal molding was small up to this stage. These results demonstrate that centrifugal molding allows for a shorter pre-setting time for this mixture than vibration molding. Furthermore, the compressive strength of the hardened body was higher than that of vibration molding.

[0059] (Sulfuric acid resistance) (Sulfuric acid resistance of hardened body by vibration molding) For comparison in the sulfuric acid resistance test, a mortar specimen (φ50 × 100 mm) was prepared by vibration molding using OPC. This mortar was prepared by simply removing the coarse aggregate from the concrete mix shown in Table 6 below.

[0060]

[0061] In addition, similar to the setting test described above, a hardened body (φ50 × 100 mm) was prepared by vibration molding using a mortar formulation obtained by simply removing the coarse aggregate from the formulation of this mixture shown in Table 2.

[0062] These hardened products made from OPC and hardened products of this mixture were immersed in a 5% aqueous sulfuric acid solution for 28 days in accordance with the "Japan Sewage Works Agency's Quality Test Method for Mortar for Repairing Cross Sections," and their sulfuric acid resistance was evaluated based on the change in mass and appearance. The amount (volume) of the 5% aqueous sulfuric acid solution was 1.96 L per test piece, and the surface area of ​​the test piece and the volume ratio of the liquid (solid-liquid ratio) were kept constant, and the entire amount was replaced with new aqueous sulfuric acid solution every 7 days.

[0063] Figure 7 shows the appearance of each specimen after 28 days of immersion. Figure 7(a) shows the OPC specimen, and Figure 7(b) shows the hardened specimen of this mixture. Figure 8 shows the test results. The OPC specimen lost mass over the immersion period, reaching a mass loss of -32% over 28 days. In contrast, the hardened specimen of this mixture, although slightly cracked, remained generally sound and exhibited excellent acid resistance. However, after 28 days of immersion, the mass loss shifted to a positive value of approximately 1%, indicating slight expansion of the hardened specimen. Based on these results, X-ray diffraction analysis was performed on the hardened specimen of this mixture to identify the minerals affecting the expansion and mass increase of the hardened specimen. As a result, it was determined that gypsum dihydrate (CaSO4·2H2O) generated from the ground granulated blast furnace slag was the primary cause.

[0064] (Sulfuric acid resistance of hardened bodies obtained by centrifugation molding) As mentioned above, the compressive strength test results of hardened bodies made from this mixture showed that centrifugal molding is effective. Based on this, cross-sectioned test pieces were taken from centrifugal test pieces made from OPC with the composition shown in Table 6 above and from hardened bodies obtained by centrifugally molding this mixture, and the sulfuric acid resistance was evaluated. In this sulfuric acid immersion test, the test pieces were immersed in a 5% sulfuric acid aqueous solution for 28 days, regardless of the surface area of ​​the test piece and the volume ratio of the solution (solid-liquid ratio).

[0065] Figure 9 shows the appearance of each specimen after 28 days of immersion. Figure 9(a) shows the centrifugal specimen made from OPC, and Figure 9(b) shows the centrifugal specimen made from this mixture. Figure 10 shows the test results. The OPC centrifugal specimen (centrifugal OPC) showed a mass loss of -16% and aggregate exposure after 28 days of immersion, indicating severe sulfuric acid degradation. On the other hand, the centrifugal specimen made from this mixture (centrifugal hardened specimen) showed a mass loss of -0.8% after 28 days of immersion, but the specimen's external appearance remained almost unchanged and it remained in good condition. Furthermore, no fine cracks or slight expansion were observed in the hardened mortar produced by vibration molding, demonstrating the effectiveness of compacting the hardened body using centrifugal molding.

[0066] (Summary) In this example, to create a highly durable concrete product, a mixture containing industrial by-products, mainly fly ash and ground granulated blast furnace slag, was used without using any Portland cement, and the hardened body was formed by centrifugal molding. In this example, the following results were obtained: (1) The hardening reaction of this mixture was due to the pozzolanic reaction and latent hydraulic properties, and the initial setting time was 14 hours and the final setting time was 19 hours. (2) In the case of vibration molding, the strength development and strength elongation were poor. For example, the compressive strength after 6 hours of pre-setting and 28 days was 35.1 N / mm 2 In contrast, centrifugal molding has good strength development and strength elongation. For example, the compressive strength after 6 hours of pre-setting and 28 days of age was 40.7 N / mm 2(3) Due to the delayed setting time, when using vibration molding, compressive strength is lower when the pre-steam curing time is 3.0 hours or less than when it is 6.0 hours or more. However, when comparing centrifugal molding with a pre-steam curing time of 3.0 hours or less and 6.0 hours or more, the difference in compressive strength is smaller than with vibration molding. Therefore, by using centrifugal molding, the delayed setting time of this mixture can be offset, making it suitable for the manufacture of practical Hume pipes. Specifically, it can be used for 1.5 hours or less. (4) A 5% sulfuric acid immersion test was conducted on hardened mortar obtained by vibration molding and an OPC mortar specimen. The OPC mortar specimen showed a mass change rate of -32%, while the hardened mortar was in a generally sound condition, although slight expansion was observed. (5) As a result of a 5% sulfuric acid immersion test on the centrifugal hardened body produced by centrifugal molding and the centrifugal specimen made by OPC, the mass loss of the centrifugal hardened body was -16%, while the mass loss of the OPC centrifugal specimen was only -0.8%, and the external appearance was generally sound.

[0067] [Strength when Mixing Ratios are Changed] For the standard mix described above, the relationship between the addition rate of each material and the compressive strength was investigated. In other words, a test was conducted to see how the compressive strength changed when the mixing ratio of each material was changed. The results are shown in Table 7 below.

[0068]

[0069] FIG. 11 shows a graph of the relationship between the additive rate and strength. In each graph, the horizontal axis shows the additive rate (%) expressed as a weight percent relative to the standard rate. The vertical axis shows the compressive strength (N / mm 2 ) is shown. As a result, it was found that the following weight percentages were suitable for the standard mix: W (water) 90-105%, FA (fly ash) 10-110%, BFS (ground granulated blast furnace slag) 90-190%, SF (silica fume) 50-130%, Ca(OH)2 (calcium hydroxide, slaked lime) 50-200%, EX (expansive agent) 60-130%, S (fine aggregate) 80-125%, G (coarse aggregate) 80-125%, and Ad (high-performance water-reducing agent) 50-150%. The effects of these are as shown in the above-mentioned embodiment.

[0070] (Sulfuric Acid Immersion Test: Comparison of Centrifugal Hardened Body, OPC, BB, and FC) In Example 1, centrifugal hardened body and centrifugal specimens made of ordinary cement (OPC) were described. In addition, sulfuric acid immersion tests were conducted in the same manner as in Example 1 using centrifugal specimens made of standard blast-furnace cement type B (BB) and standard fly ash cement type C (FC). Figure 12 shows the appearance of the deterioration state of various centrifugal specimens. Figure 12(a) is a photograph of a centrifugal specimen made of blast-furnace cement type B (BB) after 28 days of immersion, and Figure 12(b) is a photograph of a centrifugal specimen made of fly ash cement type C (FC) after 28 days of immersion. In both cases, the appearance showed severe deterioration. Figure 13 shows a graph showing the degree of deterioration in terms of mass change rate when various centrifugal specimens were immersed in a 5% sulfuric acid aqueous solution for 28 days. As a result of immersing various centrifugal specimens in a 5% sulfuric acid aqueous solution for 28 days, the mass change rate was approximately -16% for centrifugal OPC and centrifugal FC, and approximately -10% for centrifugal BB. In contrast, the mass change rate of the centrifugal hardened bodies of Examples 1 and 2 was only -0.8%, confirming the excellent sulfuric acid resistance of the hardened bodies of these Examples.

[0071] (Strength Development Depending on W / P and Mixing Ratio of FA and BFS) Next, the strength development (mortar strength) of hardened bodies (φ50 × 100 mm) (hardened mortar bodies) manufactured using mortars containing fly ash (FA) and ground granulated blast furnace slag (BFS), the main components of the hardened body, at a mixing ratio of 50%:50% and 40%:60%, was compared by changing the water-to-powder ratio (W / P). Figure 14 shows a graph of strength when the FA:BFS mixing ratio was 50%:50%. Figure 15 shows a graph of the relationship between W / P and strength for the results shown in Figure 14. σ in this figure indicates the age (days). Figure 16 shows a graph of strength when the FA:BFS mixing ratio was 40%:60%. Figure 17 shows a graph of the relationship between W / P and mortar strength for the results shown in Figure 16. In this figure, σ indicates the age of the material (days).

[0072] As a result, when the mixture ratio of fly ash (FA) and ground granulated blast furnace slag (BFS) in the hardened body was changed from 50%:50% to 40%:60%, the compressive strength (especially the initial strength up to 14 days of age) improved. Also, when the W / P ratio was 28% or less, the compressive strength at 28 days of age was approximately 50 N / mm 2 It turns out that more can be achieved.

[0073] (Compressive strength of cylindrical hardened body and centrifugal hardened body) The mixing ratio of fly ash (FA) and ground granulated blast furnace slag (BFS), the main materials of the hardened body, was changed to 50%:50% and 40%:60%, and the compressive strength was compared by changing the water-to-powder ratio (W / P) for cylindrical hardened bodies (φ100 × 200 mm) and centrifugal hardened bodies (φ200 × 300 mm) molded in the same manner as in Example 1. The fresh properties of these hardened bodies were an air content of 1.8% and a slump of 10.0 cm.

[0074] Fig. 18 shows a graph of compressive strength when the mixing ratio of FA and BFS is 50%:50%. Fig. 19 shows a graph of compressive strength when the mixing ratio of FA and BFS is 40%:60%. As a result, as in Example 1, the compressive strength tended to increase as the water-powder ratio (W / P) of the hardened body decreased. In addition, the compressive strength of the centrifugal specimens produced by centrifugal molding was greater than that of the cylindrical specimens produced by vibration molding, which showed a similar tendency to the results of Example 1.

[0075] (Effect of calcium hydroxide) The amount of calcium hydroxide (Ca(OH)2), an alkaline activator (hardening accelerator) added to the hardened mortar, was changed to compare the compressive strength of the hardened mortar (excluding coarse aggregate). Figure 20 shows a graph of the relationship between the amount of calcium hydroxide (Ca(OH)2) added and the compressive strength. Here, an experiment was carried out in which the calcium hydroxide addition rate was changed under the conditions of a W / P of 30%, fly ash of 40%, and ground granulated blast furnace slag of 60%. From these results, it was found that the optimum amount of calcium hydroxide to be mixed in terms of the expression of compressive strength was 20 kg / m 3 It was found that the strength level was low below this level, and that no increase in strength was obtained by mixing more than this level.

[0076] In addition, the inventors investigated the carbonation inhibition effect from a perspective other than the strength of the calcium hydroxide addition amount. Figure 21 shows an overview of the simple accelerated carbonation test apparatus used in the carbonation inhibition effect test. This apparatus involves placing a hardened body (specimen) in a desiccator, closing the lid, and then introducing carbon dioxide gas (concentration 40% or higher) to accelerate the carbonation of the hardened body. In the carbonation inhibition effect test of this example, a vibration-molded hardened mortar (hardened body) containing 40% fly ash and 60% blast furnace slag was prepared. After steam curing and air curing (temperature 20°C, humidity 60%) for 28 days, the carbonation was evaluated. Carbonation was assessed by spraying phenolphthalein (1% ethanol solution) on the split surface of the hardened body. The colorless area where no reddish-purple color reaction occurred was measured at 10 mm intervals to determine the carbonation depth.

[0077] Fig. 22 shows a graph of the experimental results of the relationship between the amount of calcium hydroxide and the depth of carbonation in the carbonation inhibition effect test. Fig. 23 shows photographs of the color reaction of the hardened body that was cured in air for 28 days after steam curing, as a result of the carbonation inhibition effect test. Fig. 23(a) shows the color reaction of the hardened body that was cured in air for 28 days after steam curing. 3 The carbonation depth was 7 mm. 3 The carbonation depth was 2 mm. 3 The carbonation depth was 0 mm.

[0078] As a result of the carbonation suppression effect test using this simple accelerated carbonation test device, it was found that the carbonation depth of the hardened body significantly decreased as the amount of calcium hydroxide mixed in increased. In other words, it was found that the carbonation suppression effect could be obtained by increasing the amount of calcium hydroxide (Ca(OH)2) added. In other words, the standard mix of Ca(OH)2 (calcium hydroxide, slaked lime) was 20 kg / m 3 The content range is 50 to 500% (10 to 100 kg / m 3 ) is preferable.

[0079] (Strength of cylindrical hardened body sampled during production of actual product) Next, the compressive strength of a cylindrical hardened body obtained by vibration molding of a mixture sampled during production of an actual product was measured. Specifically, when an actual centrifugal hardened body (φ250 x 2000 mm) was produced at a secondary concrete product factory, the mixture was sampled from an inlet, and the compressive strength of a cylindrical hardened body (φ100 x 200 mm) produced by vibration molding was measured. The fresh properties of this hardened body were an air content of 1.9% and a slump of 13.0 cm. Figure 24 shows the compressive strength of this vibration-molded cylindrical hardened body. As a result, the compressive strength was 41.5 N / mm at an age of 28 days. 2 It is believed that a higher value can be obtained by increasing the slump of the cylindrical hardened body produced by vibration molding.

[0080] (Method for Manufacturing Hume Pipe) Next, we will explain the manufacturing method for manufacturing Hume pipes by centrifugal molding as an example of precast concrete using the mixture of this embodiment. Figure 25 shows the manufacturing process for Hume pipes. In manufacturing Hume pipes, a rebar cage made by combining and weaving rebar is placed in a formwork. Next, while the formwork is rotating on the molding machine, concrete mixed with a mixer is poured into the formwork and compacted using centrifugal force (low, medium, and high speeds). At this time, the inner surface of the Hume pipe is also finished. The formwork is then steam-cured, slowly cooled, and removed from the formwork. After the curing period, the appearance, dimensions, etc. of the Hume pipe are inspected and then shipped. In this embodiment, when manufacturing a hardened body, the above-mentioned powder material is used instead of cement. In this way, when manufacturing an actual hardened body product by centrifugal molding, it can be performed in the same manner as the manufacturing process for Hume pipes. In addition, in the case of vibration molding, precast concrete can be similarly manufactured by performing vibration molding during the "centrifugal molding / inner surface finishing" process shown in Figure 25.

[0081] (External pressure test of actual centrifugal hardened body products) Actual centrifugal hardened body products were manufactured with dimensions of φ250 x 2000 mm and φ300 x 2000 mm. Figure 26 shows the actual centrifugal hardened body products and the test conditions. Figure 26(a) shows the appearance of the actual centrifugal hardened body products manufactured with dimensions of φ300 x 2000 mm. Figure 26(b) is a photograph showing the external pressure test conditions of the actual centrifugal hardened body products.

[0082] The external pressure test was conducted on a φ250 x 2000 mm actual product of the centrifugal hardened body of this example and a conventional Hume pipe in parallel. Figure 27 shows the results of the external pressure test on the actual centrifugal hardened body of this example (φ250 x 2000 mm). Figure 28 shows the results of the external pressure test on a conventional Hume pipe (φ250 x 2000 mm) (comparison example). The results of the external pressure test showed that the actual centrifugal hardened body of this example fully satisfied the cracking load and fracture load specifications compared to the conventional Hume pipe. In other words, it was confirmed that it has good load-bearing properties. Furthermore, its slightly larger deflection is thought to make it less susceptible to brittle fracture.

[0083] (Application to Vibration-Molded Products) Next, the inventors manufactured actual precast concrete products using the vibration molding method described above and investigated the optimal mix ratio for vibration-molded products. Examples of products that could be used for this purpose include box culverts and manholes. Table 8 below shows mix ratios for when the mixture of this example is applied to centrifugal molded products (such as Hume pipes) and when it is applied to vibration-molded products (such as box culverts). Furthermore, as shown in the mix ratio examples in Table 8 for on-site construction, the mixture can also be poured on-site if appropriate curing methods and temperature control are used.

[0084]

[0085] In Table 8, Gmax is the maximum size of the coarse aggregate, SL is the slump flow, Air is the air volume, W / P is the ratio of water (W) to the total powder amount (P), S / a is the fine aggregate ratio, S is the fine aggregate, G is the coarse aggregate, and Ad is the admixture. All of these products can improve acid resistance while meeting the same or higher quality standards such as load capacity as products using conventional cement.

[0086] It goes without saying that the configurations and operations of the above-described embodiments are merely examples, and can be modified as appropriate within the scope of the present invention.

Claims

1. Acid-resistant concrete characterized by being produced by mixing water, industrial by-products, alkaline stimulants, expansive additives, fine aggregates, coarse aggregates, and high-performance water-reducing agents, and compacting the mixture using centrifugal molding.

2. The acid-resistant concrete according to claim 1, wherein the industrial by-products include fly ash, ground granulated blast furnace slag, and silica fume, and the alkali activator includes hydrated lime.

3. The water is 170 kg / m 3 , the fly ash is 207 kg / m 3 , the ground granulated blast furnace slag was 207 kg / m 3 , the silica fume is 30 kg / m 3 , the slaked lime is 20 kg / m 3 , the expanding material is 30 kg / m 3 , the fine aggregate is 639 kg / m 3 , the coarse aggregate is 959 kg / m 3 and the high-performance water-reducing agent is 5.434 kg / m 3 3. The acid-resistant concrete according to claim 2, characterized in that the standard mix is: 90 to 105% water, 10 to 110% fly ash, 90 to 190% ground granulated blast furnace slag, 50 to 130% silica fume, 50 to 200% slaked lime, 60 to 130% expansive agent, 80 to 125% fine aggregate, 80 to 125% coarse aggregate, and 50 to 150% high-performance water-reducing agent, by weight percent.

4. The water is 170 kg / m 3 , the fly ash is 207 kg / m 3 , the ground granulated blast furnace slag was 207 kg / m 3 , the silica fume is 30 kg / m 3 , the slaked lime is 20 kg / m 3 , the expanding material is 30 kg / m 3 , the fine aggregate is 639 kg / m 3 , the coarse aggregate is 959 kg / m 3 and the high-performance water-reducing agent is 5.434 kg / m 3 3. The acid-resistant concrete according to claim 2, characterized in that the standard mix is: 90 to 105% water, 10 to 110% fly ash, 90 to 190% ground granulated blast furnace slag, 50 to 130% silica fume, 50 to 500% slaked lime, 60 to 130% expansive agent, 80 to 125% fine aggregate, 80 to 125% coarse aggregate, and 50 to 150% high-range water-reducing agent, by weight percent.

5. A concrete mixture is produced by mixing water, industrial by-products, an alkaline stimulant, an expanding agent, fine aggregate, coarse aggregate, and a high-performance water-reducing agent, and is vibrated and molded. The industrial by-products include fly ash, ground granulated blast furnace slag, and silica fume. The alkaline stimulant includes slaked lime. The water is mixed at a rate of 170 kg / m3. 3 , the fly ash is 207 kg / m 3 , the ground granulated blast furnace slag was 207 kg / m 3 , the silica fume is 30 kg / m 3 , the slaked lime is 20 kg / m 3 , the expanding material is 30 kg / m 3 , the fine aggregate is 639 kg / m 3 , the coarse aggregate is 959 kg / m 3 and the high-performance water-reducing agent is 5.434 kg / m 3 The acid-resistant concrete is characterized by being mixed in the following proportions by weight, based on a standard mix ratio: 90 to 105% of the water, 10 to 110% of the fly ash, 90 to 190% of the ground granulated blast furnace slag, 50 to 130% of the silica fume, 50 to 500% of the slaked lime, 60 to 130% of the expansive agent, 80 to 125% of the fine aggregate, 80 to 125% of the coarse aggregate, and 50 to 150% of the high-performance water-reducing agent.

6. As a by-product of the above industry, sewage sludge incineration ash 26 kg / m 3 6. The acid-resistant concrete according to claim 3, wherein the sewage sludge incineration ash is mixed in an amount of up to 200% by weight based on a standard mix ratio of 100% to 100% by weight.

7. Acid-resistant concrete according to any one of claims 1 to 6, characterized in that it is steam-cured after molding, and the pre-curing time for said steam-curing is 1.5 hours or more.

8. A concrete mixture comprising water, an industrial by-product, an alkaline stimulant, an expansive material, fine aggregate, coarse aggregate, and a high-performance water-reducing agent, and cast on site, wherein the industrial by-products include fly ash, ground granulated blast furnace slag, and silica fume, the alkaline stimulant includes slaked lime, and the water is poured at a rate of 170 kg / m 3 , the fly ash is 207 kg / m 3 , the ground granulated blast furnace slag was 207 kg / m 3 , the silica fume is 30 kg / m 3 , the slaked lime is 20 kg / m 3 , the expanding material is 30 kg / m 3 , the fine aggregate is 639 kg / m 3 , the coarse aggregate is 959 kg / m 3 and the high-performance water-reducing agent is 5.434 kg / m 3 is a standard blending ratio, by weight, of the water being 90 to 105%, the fly ash being 10 to 110%, the ground granulated blast furnace slag being 90 to 190%, the silica fume being 50 to 130%, the slaked lime being 50 to 500%, the expanding agent being 60 to 130%, the fine aggregate being 80 to 125%, the coarse aggregate being 80 to 125%, and the high-performance water reducing agent being 50 to 150%, and the industrial by-product being 26 kg / m of sewage sludge incineration ash. 3 The acid-resistant concrete is characterized in that the above-mentioned sewage sludge incineration ash is mixed in an amount of up to 200% by weight based on the standard mix ratio of 100% to 100%.

9. Precast concrete characterized by being produced from the acid-resistant concrete according to any one of claims 1 to 7.

10. The precast concrete according to claim 9, which is a sewer pipe.

11. A method for producing acid-resistant concrete, comprising mixing water, industrial by-products, an alkaline stimulant, an expansive additive, fine aggregate, coarse aggregate, and a high-performance water-reducing agent, and compacting the mixture by centrifugal molding, vibrating molding, or pouring the mixture on-site.

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