KR20180034811A - Binder of concrete of Recycled Aggregate using desulfurization gypsum - Google Patents

Abstract

A secondary product binder for concrete of recycled aggregate of the present invention which contains cement (OPC), comprises the following: 90-95 wt% of ordinary Portland cement (OPC); and 5-10 wt% of mixed ingredients including desulfurized gypsum, slag, and a thickener. The secondary product binder for concrete of recycled aggregate according to the present invention can be used as a binder of a secondary product of the recycled aggregate concrete to increase the usage amount of recycled aggregate, thereby reducing the cost by 20-25%.

Description

Technical Field [0001] The present invention relates to a recycled aggregate using desulfurization gypsum,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder for recycled aggregate concrete secondary products, and more particularly, to a recycled aggregate concrete box cullet formed by vapor curing using a binder using a desulfurization gypsum and a recycled aggregate concrete secondary product binder .

Research and development of existing architectural and civil engineering materials has been done mainly on high performance and multifunctionality. At present, however, research and development of architecture and civil engineering materials, which consider not only high performance and multifunctionality but also environmental load, and utilize various circulation resources positively and effectively, are required. In particular, since the cement industry is pointed out as the industry with the largest amount of resource consumption and CO2 emissions from the scale of its size, it can reduce the consumption of natural resources by utilizing various industrial byproducts or wastes in cement production, And the development of technologies that can reduce CO2 emissions through the development of new technologies.

In order to solve the problems caused by the depletion and depletion of natural resources, the Ministry of Environment (Ministry of Environment) recently announced the "Use of Recycled Aggregate for Recycled Aggregate Compulsory Use Construction and Compulsory Usage Amount in accordance with Article 38 (3) of the Act on the Promotion of Recycling of Construction Waste" The Ministry of Land, Transport and Maritime Affairs Notice No. 2009-713, Aug. 25, 2009).

The main technical content of the development of precast culvert using this recycled aggregate is not much different from the design method of precast culvert using ordinary concrete except the property value of concrete. However, according to the Ministry of Land, Transport and Maritime Affairs, "Recycled Aggregate Quality Standards", the maximum design strength of recycled aggregate concrete using recycled aggregate conforming to the quality standard for concrete is specified to be 27 MPa. Proper concrete mix design is the core of this technology.

According to the "criteria for recycled aggregate quality" by the Ministry of Land, Transport and Maritime Affairs, it has been suggested that if the amount of recycled coarse aggregate is less than 30% of the total coarse aggregate, the durability and safety of the coarse aggregate will be sufficient. In the case of coarse aggregate concrete, it has been reported that even when 50% of the total coarse aggregate is replaced with the coarse aggregate, there is no significant problem.

Considering structural stability and long-term stability, the development has set the replacement ratio of recycled coarse aggregate to 30% or more (up to 60%), which is the limit value proposed in "Recycled aggregate quality standard". Especially, the design criteria strength of general precast culvert is more than 34MPa, and the mixing condition is selected so that it can exceed the maximum design reference strength of 27MPa proposed in "Recycled aggregate quality standard".

On the other hand, other mixing conditions such as strength, slump and air volume were applied in a similar manner to that of commercially available precast culvert, and the mixing conditions were determined by taking into consideration the production characteristics of the factory, concrete pouring and steam curing conditions. Respectively.

In fact, recycled aggregate concrete can exhibit a strength of 30 MPa or more. Instead of replacing aggregate with 100% recycled aggregate, only 30% of the coarse aggregate is replaced with 1 kind of recycled aggregate when used in applications such as precast concrete culvert. The strength of precast concrete culvert is not a problem. In addition, since the quality of recycled aggregate is different for concrete products, the quality standard of recycled aggregate used when manufacturing concrete products using recycled aggregate is based on the Korean Industrial Standard (KS) Standards.

Concrete box culver is gradually used as important structures such as joints, electric power, and communication areas in past applications such as stormwater, underground storage, etc. It not only secures excellent strength, durability and watertightness of concrete structure, but also has advantages in joint treatment and construction. It is due to one thing. Generally, it is used as a collective, electric power, and so on. It is a structure used in almost all road construction sites and is often used as a passage or a waterway that crosses a road.

* Technology trends of the same industry

                 domestic                  Overseas
As a result of recycling aggregate use of recycled aggregate producers, recycled aggregate is mainly used for applications with low added value such as roadside assistance layer, embankment, and backfill.

In Korea, the application of recycled aggregate to precast concrete culvert has not been successful.



In the United States, studies on the conditions and test methods for using recycled aggregate for road pavement in the DOT of each state have been completed (limited to road pavement)

As in the case of the United States, research and standardization of road recycled aggregate has been completed in the UK.

In France, Spain and Belgium, practical guidelines for recycled aggregates are presented, which is very meaningful in that they have prepared research and technical guidelines for the recycling of recycled aggregate.

Currently, many advanced countries have started to research and develop technology of recycled aggregate materials and the utilization of recycled aggregate materials for road pavement. However, there have been some studies on the application of recycled aggregate to structures and precast concrete culvert The development of specific technologies is insufficient.

In the construction industry in the 21st century, the recycling of construction waste has become a challenge for the society, and the social demand for the increase in the use of recycled aggregate is becoming increasingly evident in Korea. In order to increase the utilization of recycled aggregate in accordance with the social environment, the quality of recycled aggregate and the basic properties and mechanical properties of recycled aggregate concrete have been steadily studied. However, to expand utilization of recycled aggregate concrete, There is insufficient verification. In order to more aggressively apply the recycled aggregate to the concrete structure field, it is urgently necessary to quantitatively examine the applicability of the recycled aggregate as a structural material, to clarify its use, and to establish and maintain a related existing structure.

Recently, the use of structural recycled aggregate concrete as a precast concrete product has been carefully searched. In particular, a method of using it for precast concrete culvert which is widely used for landfill, land development, river cover, etc., can be considered. Currently, precast concrete culvert has been used in a variety of fields as its excellence has been objectively proven through many research results in the past, and it is seeking diversification due to market expansion.

The present invention provides a recycled aggregate concrete box cullet formed by vapor curing using a binder using desulfurization gypsum and a recycled aggregate concrete secondary product binder for the same.

The recycled aggregate concrete secondary product binder according to the present invention is a binder including cement (OPC), wherein the binder comprises 90 to 95% by weight of OPC (Ordinary Portland Cement); 5 to 10% by weight of a mixed material comprising desulfurized gypsum, slag and thickener; .

The thickener is such that it contains 0.3% by weight of the total amount of binder in the concrete specification or concrete for that purpose.

The mixed material is prepared by mixing 100 wt% of the mixed material with desulfurized gypsum

40% by weight of blast furnace slag, 40% by weight of blast furnace slag, 20% by weight of natural gypsum (natural anhydrite) and 0.3% by weight of a thickener.

Also, the curing of the steam cured concrete according to the present invention was performed at 2.5-3.5 hours

The temperature rise time of 0.5-1.5 hours, the constant temperature time of 3-4 hours, and the temperature fall time to room temperature, and the temperature rising speed is 50-70 ° C for 1 hour, 80-90 ° C for the maximum temperature .

The recycled aggregate concrete according to the present invention can be used as a binder of a secondary product to increase the amount of recycled aggregate, which can reduce the cost by 20-25%.

Also, it is possible to secure the basic physical properties and durability of the concrete by preventing the material separation and enhancing the strength of the mixed material according to the present invention.

The production of concrete secondary products using natural aggregate, Portland cement, and lime slag is an economical burden, and problems are arising due to depletion of natural resources and carbon dioxide emissions. However, in the production of concrete secondary products by utilizing recycled aggregate through the certification of this technology, it is possible to drastically reduce natural degradation and depletion of natural resources by mining of aggregate.

In this development, we developed a mixed material using desulfurized gypsum to utilize the recycled aggregate used as the main material from 40% to 60% of the original amount. This is a necessary product for the conventional production, and it can be produced and sold only with the meter, blender, It is possible to reduce the production cost by increasing the utilization rate of the recycled aggregate.

1 is a view showing a curing process of concrete according to the present invention
2 is XRF (X-ray fluorescence analysis) of a desulfurization gypsum which is a composition of a mixed material, FIG. 3 is blast furnace slag, and FIG. 4 is XRF (X-ray fluorescence analysis) of anhydrous gypsum.
Other Figures 5-12 are diagrams related to the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, substantially the same contents will not be described in detail.

Also, when a component is described as being "connected", "coupled", or "touched" to another component, the component may be directly connected or connected to the other component, Even if the element is "connected", "coupled" or "touched", it should be understood as the same technical idea.

Also, when it is stated that an element is formed, formed or constituted, it should be interpreted as substantially the same unless otherwise defined.

In addition, in the present invention, the meaning of inclusion may be inclusive of other ingredients in addition to the general meaning of open type that additionally may include other ingredients, so it should be judged based on the contents.

The mixed material in the present invention is a material other than admixture cement, aggregate, and water, and is a material to be added as necessary before being placed to give special properties to concrete and the like.

Hereinafter, embodiments of the present invention will be described with reference to the drawings and related contents.

FIG. 1 is a view showing the curing process of concrete according to the present invention, FIG. 2 is XRF (X-ray fluorescence analysis) of a desulfurization gypsum which is a composition of a mixed material, FIG. 3 is a blast furnace slag, X-ray fluorescence analysis).

As shown in FIG. 2, the desulfurization gypsum is composed of Na2O, MgO, Al2O3, SiO2, P2O5, SO3, Cl, K2O, CaO, TiO2, V2O5, Cr2O3, MnO, Fe2O3, NiO, ZnO, SrO, ZrO2, MoO3 The content of Al2O3, the content of Al2O3, the content of Al2O3, the content of Al2O3, the content of Al2O3, the content of Al2O3, the content of Al2O3, the content of Al2O3, 0.0862 wt% of TiO2, 0.455 wt% of V2O5, 0.0503 wt% of MnO, 0.579 wt% of Fe2O3, 0.0728 wt% of NiO, and 0.0617 wt% of SrO.

As shown in Fig. 3, the blast furnace slag is composed of Na2O, MgO, Al2O3,

Wherein the content of the blast furnace slag is 0.0368 wt% of Na2O, 4.45 wt% of MgO, 0.1 wt% of Al2O3, 0.02 wt% of Al2O3, 13.9% by weight of SiO2, 32.5% by weight of SiO2, 2.19% by weight of SO3, 0.466% by weight of K2O, 44.7% by weight of CaO, 0.511% by weight of TiO2, 0.204% by weight of MnO, 0.446% by weight of Fe2O3 and 0.11% by weight of BaO.

As shown in Fig. 4, the anhydrous gypsum is composed of Na2O, MgO, Al2O3,

Wherein the content of the SiO2, P2O5, SO3, K2O, CaO, Fe2O3, ZnO, SrO and ZrO2 is 0.0673 wt% of Na2O, 0.0464 wt% of MgO, 0.339 wt% of Al2O3, 55.8% by weight of SO3, 0.0790% by weight of K2O, 42.5% by weight of CaO, 0.107% by weight of Fe2O3 and 0.0744% by weight of SrO.

* Characteristics of desulfurized gypsum

The desulfurization process of all coal-fired power plants in Korea is composed of limestone powder

As a by-product of the process, FGD (flue gas desulfurization) gypsum is generated

When 1kg of limestone powder is injected, about 1.5kg to 1.7kg of flue gas desulfurization gypsum

(Calcium Sulfate Dihydrate, CaSO4 ㆍ 2H2O).

Desulfurization gypsum (GSH) has high concentration of calcium sulfate and few impurities. Although it is not much behind quality natural gypsum in terms of quality, most of the crystal structure forms a round needle structure and partially shows plate-like crystals. Since it does not have a self-setting property due to hydration reaction, it is mostly used as a raw material of cement, and some of them are limitedly used in gypsum board.

Therefore, only the flue gas desulfurization gypsum itself is presently difficult to be utilized as a raw material having a high added value, and if it is estimated that the total amount of recycled gypsum will be more than 2 million tons in the present time, It is required to use it as a construction material.

* Characteristics of blast furnace slag

In addition to cement, which is widely known as a material that reacts with water at present and reacts with water, minerals having a composition of aluminosilicate are known to exhibit hydraulic properties due to alkali or sulfate stimulation. As a result of continuous research, it has been found that alkaline earth metal compounds of Group 2 In addition, it has been found that alkaline metals can generate hydric compounds with Group 3 and Group 4 (aluminosilicate), Groups 2 and 4 (alkaline earth silicate), Groups 2 and 3 (alkaline earth aluminate) It has been confirmed that a hydraulic cured product can be obtained even if it is not cement.

In particular, blast furnace slag is a typical by-product that is generated in large quantities during the production of pig iron. If it is recycled as a raw material for cement substitute mixed materials mainly in construction materials, mineral resources such as limestone and clay necessary for clinker production are depleted It is possible to reduce environmental load such as prevention of destruction of forest resources due to limestone mining and transportation, insufficient dust, vibration, noise, and shortage of landfill due to landfill of industrial waste.

* Anhydrous gypsum [anhydrous gypsum, anhydrous gypsum, Anhydridgips]

Calcium sulfate anhydrous CaSO4.

There are natural products and artifacts, and the former is called pumice. There are two types of artificial products.

1) Crystalline gypsum (or half gypsum) is dewatered by calcining.

2) It is obtained as a plaster (chemical gypsum) from Pusan (ie, when producing hydrogen fluoride from fluorite or by precipitation of gypsum by increasing the temperature and concentration of phosphoric acid in the wet phosphoric acid production process).

There are three types of artificial anhydrite gypsum, type Ⅲ, Ⅱ and Ⅰ, and they are transitioned to gypsum type Ⅲ, Ⅱ and Ⅰ with temperature. Type Ⅲ has the same structure as semi-gypsum and is water-resisting in the form of missing water molecules. Type Ⅱ is the same as a pumice, and it is almost not hydratable. The non - hydratable gypsum is called a gypsum.

On the other hand, the theory of strengthening by the gypsum additive in the cement system is as follows.

In the cement system, gypsum has been known to act to regulate condensation by ettringite, which is produced mainly by reaction with tricalcium aluminate (C3A, 3CaO · Al2O3).

The regulating mechanism of the gypsum is that the layer of ettringite is formed on the particle surface of C3A, so that this layer delays the next hydration of C3A so that the condensation of the cement is mainly caused by the hydration of calcium silicates (C3S, C2S) It can be seen that the production of Etringite promotes the production of CSH gel, which is the main hydraulic compound of cement.

In the cement matrix, Etringing has an important relation with the temporal harmonization of the hydration reaction rate of the cement and the formation timing of the ettringite-based hydrate. Further, in the cement composition, the content of each component in the CaO-Al2O3- It is also known to play an important role in the change of properties due to rain. The cement admixed with anhydrous gypsum is used as a rapid cement, expansion cement, anhydrous cement, and high strength cement due to the control of the composition and the timing of the generation of ettringite, depending on the reaction characteristics of the ettringite.

Therefore, when the ettringite is formed before the structure of the cemented product is formed, the product exhibits a tingling property. If the etchringite planet intensively occurs at the time of formation of the structure of the cementite product, it contributes to the strengthening of the cured product, , It is said that when the etching ring is formed after the formation of the hardened body, the etching ring is expanded or broken due to the growth of the etching ring crystal.

In addition, the reaction for producing ettringite from aluminate can effectively solidify the water as compared with the hydration reaction of silicates, as shown in the following three chemical reaction equations, so that the free water in the matrix is fixed as a crystal number, It is possible to manufacture high strength concrete due to the reduction effect of the ratio.

The mechanism of high strength expression in the cement system containing the gypsum admixture can be summarized as the following two reaction mechanisms.

From the beginning of hydration, the hydrolysis of C3S is promoted by steam curing or Auto-Clave curing, and the elution amount of Ca2 + ions is increased. C3S increases hydrate with the initiation of vapor curing and exhibits high strength, As shown in the following three chemical reaction formulas, the etching ring is generated from the beginning of hydration as compared with the hydration reaction of silicates, and a large amount of free water in the cement hardened body is fixed to the crystal water, thereby substantially lowering the water cement ratio. Lt; / RTI >

a) C3A + 3CaSO4 + 32H2O? C3A? 3CaSO4.32H2O

b) 2C3S + 6H2O? 3CaO.2SiO2.3H2O + 3Ca (OH) 2

c) 2C2S + 4H2O? 3CaO.2SiO2.3H2O + Ca (OH) 2

Etringing gas generated by the above reaction is filled with large pores of 1400 ANGSTROM or more with a large needle-like crystal of several ㎛, and concretes the concrete structure, so that high strength is expressed in a short period of time and the freezing and thawing resistance is increased. It is much better than cement.

In addition, from the initial stage of hydration, a large amount of ettringite is formed to make the internal structure of the cement paste finer. In general, Portland cement and cement sulfate cement are cured with standard curing and steam curing, It can be seen from the experimental results confirmed through this. It has been reported that the use of high sulfate cement can reduce voids of 23% in water curing and 30% or more in steam curing. It does not contain chlorides or other organic substances and does not cause corrosion problems such as corrosion of steel bars due to salt corrosion.

* Thickener

Material that increases the viscosity of concrete.

The thickener used in this experiment was an acrylic water-soluble polymer (main component methyl cellulose)

By incorporating this thickener, it is possible to increase the viscosity of the concrete and to improve the separation resistance of the material, thereby improving the filling property and stabilizing the quality.

However, when the thickener is used, the viscosity of the mixer is larger than that of ordinary concrete. Therefore, the mixing load of the mixer is larger than that of the concrete, and the time required for the load current value to be constant is long. Therefore, a non-beam time of about 1 to 3 minutes is required in addition to the ordinary mixing time.

In one embodiment of the present invention, the methylcellulose may be selected from the group consisting of hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxyethylcellulose, ethylhydroxyethylcellulose, and methylethylhydroxyethylcellulose.

* Characteristics of recycled aggregate

The quality of recycled aggregate concrete is deteriorated. The mortar attached to the surface of recycled aggregate is a major cause of performance deterioration of recycled aggregate concrete. In addition, cracks in recycled aggregate, fine powder of waste concrete, It is estimated.

Particularly, since the recycled aggregate has a very high water absorption rate, it requires a large amount of water to obtain a predetermined slump when used as a concrete aggregate, which causes additional phenomena such as material separation, drying shrinkage and compression strength.

Generally, when recycled aggregate is used, it is reported to be lower than the compressive strength of ordinary concrete by about 20% ~ 40%. Economically, it is about 30 ~ 50% cheaper than ordinary aggregate. very big.

FIG. 5 is a view showing the quality standard of the recycled aggregate, and FIG. 6 is a view showing the particle size of the recycled aggregate.

The recycled aggregate used in this development was recycled coarse aggregate of type 1 according to KS F 2573 (recycled aggregate for concrete), and recycled aggregate corresponding to the quality standard of the recycled aggregate was used.

The following are experimental results showing the effects and the like of the present invention

7 is a view showing existing data.

As shown in FIGS. 8 and 9, it was difficult to express a strength of 27 MPa or more in a sample (G40) of 40% or more at the time of simple substitution, and a severe material separation phenomenon occurred as a result of the slump test.

10 is a view showing 10% incorporation of the inventive blend (blast furnace 40, desulfurization 40, natural gypsum 20).

Figs. 11 and 12 are views showing effects and the like of the present invention. Fig.

When the developed mixed material was mixed with 5 ~ 10%, the strength development was over 30 MPa even when the recycled aggregate was replaced with 60 as shown in the above table, and the material separation phenomenon did not occur. This can be attributed to securing the physical properties of concrete by the mechanism of strength development of gypsum and reducing the separation of materials by thickener.

As described above, the present invention relates to a binder for recycled aggregate concrete secondary products, and more particularly to a recycled aggregate concrete box cullet formed by vapor curing using a binder using a desulfurized gypsum and a recycled aggregate concrete secondary product binder .

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (1)

The recycled aggregate concrete secondary product binder is a binder containing cement (OPC), wherein the binder comprises 90 to 95% by weight of OPC (Ordinary Portland Cement); 5 to 10% by weight of a mixed material comprising desulfurized gypsum, slag and thickener; Wherein the second aggregate material is a recycled aggregate concrete using a desulfurization gypsum.

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