Low-cement carbon-reduction-type precast concrete structure

Abstract

The present invention relates to a concrete structure manufactured by assembling a precast concrete panel comprising a composition capable of ensuring durability such as workability and crack resistance and ensuring stable strength while reducing the amount of cement, and, more specifically, comprises 10-50 parts by weight of cement and 1-15 parts by weight of a calcium-based alkaline activator on the basis of 100 parts by weight of blast furnace slag.

Description

Low-cement, low-carbon precast concrete structures

[0001] The present invention relates to a concrete structure manufactured by assembling precast concrete panels containing a composition capable of securing durability such as workability and crack resistance while reducing the cement content and having the advantage of securing stable strength.

[0002] While various efforts are being made worldwide to prevent global warming (the Kyoto Protocol, adopted in 1997 and entered into force in 2005, expires in 2012), negotiations for a new climate change agreement are underway until 2009 following the adoption of the 'Bali Roadmap' in Bali, Indonesia in December 2007.

[0003] Accordingly, there is a need to drastically reduce emissions of greenhouse gases such as carbon dioxide worldwide.

[0004] Meanwhile, the cement industry, along with the steel industry, is a major carbon dioxide emitter, emitting approximately 0.9 tons of carbon dioxide per ton of cement, which is the basis for concrete manufacturing. Therefore, there is an urgent need to suggest methods and alternative materials for this.

[0005] Domestic cement production amounts to approximately 60 million tons per year, emitting approximately 54 million tons of carbon dioxide. As part of a solution, research is continuously being conducted to utilize industrial byproducts to replace cement.

[0006] Domestically and internationally, blast furnace slag, fly ash, etc. are widely used in concrete by mixing them with cement, but this method has limitations in drastically reducing carbon dioxide emissions.

[0007] In addition, as mentioned above, concrete that uses more than 50% of industrial by-products such as blast furnace slag, fly ash, and bottom ash has problems such as low initial strength and low durability, and is being used in some special structures.

[0008] In general, low-cement concrete is commonly known to use concrete cured at room temperature using blast furnace slag and concrete cured at high temperature using fly ash. The alkaline activator used in these methods is adjusted by mixing NaOH and sodium silicate according to the type of binder. The use of such alkaline activators creates a strong alkaline environment for the concrete, and in some cases, there is a problem that high-performance water reducing agents cannot properly demonstrate their work performance in a strong alkaline environment.

[0009] In addition, when manufacturing low-cement concrete based on blast furnace slag, initial rapid setting occurs, making it difficult to control rapid setting. In addition, the rapid setting phenomenon reduces workability and causes problems with strength reduction.

[0010] Regarding this problem, Korean Patent Registration No. 10-1513897 discloses a binder composition comprising 30 to 60 parts by weight of Portland cement, 20 to 50 parts by weight of blast furnace slag powder, and 10 to 30 parts by weight of fly ash, wherein 0.5 to 1.5 parts by weight of an early-strength reducing agent is further mixed based on 100 parts by weight of the binder composition, and the binder composition further includes a durability improving agent, wherein the durability improving agent is ferrosilicon mixed in by substituting 3 to 5 parts by weight of the same weight based on 100 parts by weight of the blast furnace slag powder, and 3 to 10 parts by weight of the blast furnace slag powder is premixed by substituting 3 to 10 parts by weight of a calcium salt compound based on 100 parts by weight of the blast furnace slag powder, and the calcium salt compound is mixed in by substituting 3 to 6 parts by weight of the same weight based on 100 parts by weight of the blast furnace slag powder. As a basic ash, an eco-friendly low-cement concrete binding material composition is proposed, characterized in that the CaO content of the calcium salt compound is 50 to 70% of the total weight of the calcium salt compound components.

[0011] In the case of the above technology, it is said that rapid hardening due to the use of an activator is prevented and strength and stability are secured, but it is not expected to sufficiently resolve these issues, and there are problems such as crack resistance and reduced workability due to the rapid hardening problem cannot be expected to be resolved.

[0012] Accordingly, the inventors of the present invention intend to provide a concrete structure manufactured by assembling precast concrete panels containing a composition that has the advantage of ensuring stable strength while reducing the cement content, as well as ensuring durability such as workability and crack resistance.

[0013] A low-cement, carbon-reducing precast concrete structure using a calcium-based alkaline activator of the present invention (hereinafter referred to as “the structure of the present invention”) is characterized by containing 10 to 50 parts by weight of cement and 1 to 15 parts by weight of a calcium-based alkaline activator per 100 parts by weight of blast furnace slag.

[0014] As an example, the calcium-based alkaline activator is characterized by being at least one of anhydrite, calcium hydroxide, and a calcium-based alkaline byproduct.

[0015] As an example, the calcium-based alkaline by-product is characterized by having a CaO content of 35 to 45 wt%, an SO3 content of 15 to 25 wt%, an SiO2 content of 10 to 20 wt%, and an Al2O3 content of 3 to 8 wt%.

[0016] As an example, it is characterized in that 1 to 5 parts by weight of polyanionic polymer is additionally included for 100 parts by weight of blast furnace slag.

[0017] One example is characterized by the inclusion of polyaspartate.

[0018] One example is characterized by the inclusion of abietic acid.

[0019] As an example, 0.01 to 1 part by weight of a mixture of polyaspartate and abietic acid is mixed with 100 parts by weight of blast furnace slag, and the polyaspartate and abietic acid are mixed in a weight ratio of (7:3) to (9:1).

[0020] As described above, the structure of the present invention has the advantage of ensuring stable strength while reducing the cement content, and also has the advantage of ensuring durability such as workability and crack resistance.

[0021] Figure 1 is a photograph showing a calcium-based alkaline byproduct as an example of a calcium-based alkaline activator according to one embodiment of the present invention.

[0022] Hereinafter, the present invention will be described in more detail through examples.

[0023] Since embodiments according to the present invention can be modified into various other forms, the scope of the present invention is not limited to the embodiments described below.

[0024] The structure of the present invention is constructed by assembling concrete panels manufactured by precasting, and is characterized in that the concrete panels are manufactured by a composition including blast furnace slag, cement, and a calcium-based alkaline activator.

[0025] The structure of the present invention relates to a structure constructed by assembling precast concrete panels. Various known technologies exist for structures formed by assembling precast concrete panels, such as double-wall or single-wall construction methods.

[0026] In particular, the structure of the present invention is characterized in that the concrete panel is manufactured by precasting using a composition containing cement, blast furnace slag, and a calcium-based alkaline activator.

[0027] The composition applied to the present invention naturally includes water in addition to the above components. The type of water is not limited, but it is preferable to use water that is purified and free of impurities. In addition, the ratio of water to binder (W / B) is a value that determines the strength and durability of concrete, such as the design standard strength and the mixing strength, and it is preferable that the W / B be 30 to 60 wt% so that drying shrinkage of the concrete, material separation, etc. do not occur.

[0028] In addition, the composition applied to the present invention further includes aggregates in addition to the above compositions, and the aggregates include coarse aggregates and fine aggregates.

[0029] The above coarse aggregate is generally referred to as gravel, and is not limited to any type as long as it is commonly used in the industry. It is recommended to use crushed aggregate or natural aggregate as the above coarse aggregate, and it is preferably recommended to use one that satisfies KS F 2502 or KS F 2527.

[0030] The above fine aggregate is generally referred to as sand, and both fine and coarse aggregates can be used. The fine aggregate should preferably pass almost completely through a No. 4 sieve (ASTM C125, 4.75 mm), and silica sand, etc. are recommended.

[0031] The above coarse aggregate is preferably a material that mainly remains on a No. 4 sieve (ASTM C125, 4.75 mm), such as silica sand, quartz, marble, granite, limestone, calcite, feldspar, alluvial sand, other sand, or other durable aggregates or mixtures thereof.

[0032] In addition, in the present invention, in order to determine the fluidity of concrete, it is good for the fine aggregate ratio (S / a) to be 30 to 60 volume%, which can be calculated as the volume ratio of sand (S) to the total aggregate volume (sand + gravel, a).

[0033] The composition of the present invention is characterized by being formed by mixing cement, blast furnace slag, and the activator. In the present invention, the alkaline activator must be capable of activating industrial by-products such as blast furnace slag as a binder composition, and the binder of the industrial by-products must contain SiO2, CaO, Al2O3. It is characterized in that it can only be applied to a bonding composition having components capable of polymerization reaction, such as the back.

[0034] Here, the polymerization reaction is a reaction that forms a geopolymer and is one of the largest reactions that can be induced in the present invention, and in addition, a reaction that promotes a hydration reaction can also be attempted.

[0035] The above calcium-based alkaline by-product is an industrial by-product and is characterized by containing 35 to 45 wt% of CaO, 15 to 25 wt% of SO3, 10 to 20 wt% of SiO2, and 3 to 8 wt% of Al2O3. Table 1 below shows the component analysis ratio of the calcium-based alkaline by-product.

[0036] FormulaConcentrationFe2O312.67CaO39.07SO320.91SiO215.89Al2O36.95MgO2.05etc2.46

[0037] It is preferable to mix 10 to 50 parts by weight of cement and 1 to 15 parts by weight of calcium-based alkaline activator for 100 parts by weight of blast furnace slag.

[0038] In this way, in the present invention, a calcium-based alkaline by-product is applied as an alkaline activator, and as can be seen in the experiments below, it exhibits almost the same effect in terms of early strength as compared to the application of existing activators (sodium sulfate, etc. for securing early strength), while in the case of existing activators, there may be a problem of reduced workability due to rapid hardening. However, as can be seen in the experiments below, it can be seen that by adding a calcium-based alkaline by-product as an activator, early strength is secured without reducing workability.

[0039] In the case of low-cement concrete manufactured in this way, when cured in steam at 60℃ for 8 hours, it develops a strength of 24 MPa or more in 13 hours and 40 MPa or more in 24 hours, which can reduce the amount of CO2 generated during the manufacture of precast concrete by 60 to 80%.

[0040] Meanwhile, in the present invention, an alkaline activator is used, but shrinkage of the paste due to the alkaline activator cannot be completely controlled, and cracks are induced by such shrinkage of the paste. Accordingly, the present invention presents an example in which a polyanionic polymer is further included to improve resistance to such shrinkage cracks.

[0041] The above polyanionic polymer functions as a swelling agent to compensate for shrinkage of the paste caused by an alkaline activator.

[0042] Polyanionic polymers can be applied to alginate.

[0043] However, when a general expanding agent is added, not only cations but also anions are absorbed during the moisture absorption process. In this case, OH- for generating calcium hydroxide in the cement hydration reaction may be absorbed and inhibit the hydration reaction. Therefore, in the present invention, a polyanionic polymer is added so that only cations such as calcium ions are selectively absorbed during moisture absorption as well as expansion, thereby controlling problems such as strength reduction.

[0044] It is preferable to mix 1 to 5 parts by weight of polyanionic polymer per 100 parts by weight of blast furnace slag.

[0045] Meanwhile, in the present invention, there may be a problem of reduced workability due to the addition of an activator, and there may be a problem of dry cracking due to early hardening by an alkaline activator.

[0046] Accordingly, the present invention further presents an example in which polyaspartate is further included in addition to the above compositions in order to improve workability by adding an activator while simultaneously improving resistance to drying cracking caused by an alkaline activator.

[0047] That is, the workability is improved by improving dispersibility through the addition of polyaspartate, and the resistance to drying cracks is improved by moisturizing.

[0048] However, when only polyaspartate is added, there is a problem that strength is reduced due to material separation, etc.

[0049] Accordingly, the present invention presents an example in which abietic acid is further included in addition to polyaspartate.

[0050] The addition of abietic acid controls the strength loss while also improving corrosion resistance.

[0051] Preferably, it is appropriate to mix 0.01 to 1 part by weight of a mixture of polyaspartate and abietic acid with respect to 100 parts by weight of blast furnace slag, and it is appropriate to mix the polyaspartate and abietic acid in a weight ratio of (7:3) to (9:1).

[0052] The following describes embodiments of the present invention through experimental examples. Table 2 below shows the low-cement concrete mix proportions.

[0053] Slump (mm) Air content (%) Water-binder ratio (%) Fine aggregate ratio (S / a) Unit quantity Binder amount Fine aggregate Coarse aggregate AE agent High-performance water reducing agent Cement Blast furnace slag Fine powder Anhydrite High-temperature steel 1804.033.247.4161.092368205767.2868.50.152.83

[0054] * Calcium-based alkaline by-products were used as the preservative.

[0055] The results of the slump and compressive strength tests using the above mixture are shown in Table 3 below.

[0056] Classification Slump (mm) Age (days) 13h714 Low cement 18036.646.246.9

[0057] Below, samples were prepared using the same mixing ratio as the above low-temperature cement, but with different additives.

[0058] [Comparative Example 1]

[0059] The mixing ratio was the same as in Table 2 above, but 2.5 parts anhydrite and 0.5 parts early-strengthening agent were added as activators (unit: kg / ㎥).

[0060] [Comparative Example 2]

[0061] The mixture was mixed in the same manner as in Table 2 above, but 50 gypsum anhydrite and 12 early-strengthening agent were added as activators (unit: kg / ㎥).

[0062] [Comparative Example 3]

[0063] The mixing ratio was the same as in Table 2 above, but sodium sulfate was added in the same ratio as the activator instead of the calcium-based alkaline by-product.

[0064] [Example 1]

[0065] It was mixed in the same way as in Table 2 above.

[0066] [Example 2]

[0067] The mixture was mixed in the same manner as in Table 2 above, but 1 part by weight of bentonite was added to 100 parts by weight of blast furnace slag.

[0068] [Example 3]

[0069] The mixing ratio was the same as in Table 2 above, but 1 part by weight of alginate was added to 100 parts by weight of blast furnace slag.

[0070] [Example 4]

[0071] The mixing ratio was the same as in Table 2 above, but 0.5 parts by weight of polyaspartate was added to 100 parts by weight of blast furnace slag.

[0072] [Example 5]

[0073] The mixture was mixed in the same manner as in Table 2 above, but 0.5 parts by weight of polyaspartate and abietic acid (weight ratio 9:1) were additionally included for every 100 parts by weight of blast furnace slag.

[0074] Test Item UnitComparative Example 1Comparative Example 2Comparative Example 3Example 1Example 2Example 3Example 4Example 5Test SpecificationCompressive strength (14 days)Mpa39.145.846.246.940.346.141.747.1KS F2405Flowmm180165160180170165200195Length change rate(%)0.140.310.170.190.0350.0330.00910.00080KS F2424Mass reduction rate after sulfuric acid immersion (56 days)(%)0.990.810.980.940.780.820.610.097ASTM C267

[0075] In terms of compressive strength, it can be seen that Comparative Example 1 produces lower results than Example 1. This means that when the amount of activator added is less than 1 part by weight per 100 parts by weight of blast furnace slag, the activation of the blast furnace slag is minimal, resulting in a detrimental effect on the compressive strength.

[0076] In the case of Comparative Example 2, it can be seen that almost the same effect is expressed in terms of compressive strength as in Example 1, but it can be seen that workability is reduced and it can be seen that an unfavorable effect is expressed in terms of crack resistance. It is believed that this is due to the expression of excessive early strength. In addition, it can be seen that it is also unfavorable in terms of corrosion resistance, so it is appropriate to mix the activator in an amount of 1 to 15 parts by weight per 100 parts by weight of blast furnace slag.

[0077] In addition, in terms of compressive strength (early strength), it can be seen that Comparative Example 3 and Example 1 exhibit almost the same effect. On the other hand, in terms of workability, it can be seen that in the case of Comparative Example 3, the workability is lower than that of Example 1. Therefore, it can be seen that by applying a calcium-based alkali byproduct as an activator as in Example 1, the early strength is secured while solving the problem of lower workability due to rapid hardening.

[0078] In addition, in terms of compressive strength, it can be seen that Example 2 is smaller than Example 1. This is believed to be due to the addition of bentonite as a swelling agent, which causes OH- to be adsorbed during the moisture absorption process, thereby inhibiting the hydration reaction.

[0079] In contrast, Example 3 is found to be more advantageous in terms of compressive strength than Example 2. This is believed to be due to the addition of alginate as a swelling agent, which allows only cations to be absorbed during the moisture absorption process.

[0080] In addition, it can be seen that the compressive strength of Example 4 is lower than that of Example 3. This is believed to be due to material separation, etc., due to the addition of polyaspartate to improve workability and resistance to drying cracks. To compensate for this, it is believed that the problem of strength reduction is solved by adding abietic acid in addition to polyaspartate in Example 5.

[0081] In terms of workability, it can be seen that examples 4 and 5 are the best, which is believed to be due to the addition of more polyaspartate to improve dispersibility.

[0082] In terms of crack resistance, it can be seen that the crack resistance of Examples 2 and 3 is improved compared to Example 1 due to the addition of a swelling agent. It can be seen that Examples 4 and 5 are the best, which is believed to be due to the addition of more polyaspartate, which also improves resistance to drying cracking.

[0083] In terms of corrosion resistance, it can be seen that the cases of Examples 2 and 3 have more advantageous effects than the case of Example 1, which is believed to be due to the improvement in crack resistance as mentioned above, and the case of Example 4 is known to be superior to the cases of Examples 2 and 3, which is believed to be due to the addition of polyaspartate in the case of Example 4, which improves the resistance to dry cracking, and in particular, it can be seen that the case of Example 5 has the most excellent effect, which is believed to be due to the addition of abietic acid in addition to the polyaspartate, which improves the durability of the paste.

Claims

1. A low-cement, carbon-reduced precast concrete structure characterized by comprising 10 to 50 parts by weight of cement and 1 to 15 parts by weight of calcium-based alkaline activator per 100 parts by weight of blast furnace slag.

2. In paragraph 1, A low-cement, carbon-reducing precast concrete structure characterized in that the calcium-based alkaline activator is at least one of anhydrite, calcium hydroxide, and a calcium-based alkaline byproduct.

3. In paragraph 2, A low-cement, carbon-reduced precast concrete structure characterized in that the calcium-based alkali by-product contains 35 to 45 wt% of CaO, 15 to 25 wt% of SO3, 10 to 20 wt% of SiO2, and 3 to 8 wt% of Al2O3.

4. In paragraph 1, A low-cement, carbon-reduced precast concrete structure characterized in that it further contains 1 to 5 parts by weight of a polyanionic polymer per 100 parts by weight of blast furnace slag.

5. In paragraph 1, A low-cement, carbon-reduced precast concrete structure characterized by further inclusion of polyaspartate.

6. In paragraph 5, A low-cement, carbon-reduced precast concrete structure characterized by further inclusion of abietic acid.

7. In paragraph 6, A low-cement, carbon-reduced precast concrete structure characterized in that 0.01 to 1 part by weight of a mixture of polyaspartate and abietic acid is mixed with 100 parts by weight of blast furnace slag, and the polyaspartate and abietic acid are mixed in a weight ratio of (7:3) to (9:1).

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