KR20200113452A - Manufacturing method of precast geopolymer concrete member - Google Patents

Abstract

Disclosed is a method for preparing a precast geopolymer concrete member. An embodiment of the present disclosure provides a method for preparing a precast geopolymer concrete member includes: mixing a geopolymer binder including fly ash with non-hardened geopolymer concrete composition including an alkali stimulant, water, and an aggregate; pouring the non-hardened geopolymer concrete composition into a mold according to the precast geopolymer concrete member to be prepared; performing a high and constant temperature curing process for the geopolymer concrete composition at a high temperature and constant temperature for 3 to 5 hours at a maximum curing temperature of 60 to 70°C; curing the geopolymer concrete composition while reducing a curing temperature with a specific gradient from the maximum curing temperature to a minimum curing temperature which is preset; and performing a low-and-constant temperature curing process for the geopolymer concrete composition at the minimum curing temperature for a specific time.

Description

Manufacturing method of precast geopolymer concrete member {Manufacturing method of precast geopolymer concrete member}

The present invention relates to a method of manufacturing a precast geopolymer concrete member. More specifically, in the case of manufacturing a precast concrete member using a geopolymer binder of fly ash and blast furnace slag, a precast geopolymer concrete member manufacturing method that can effectively exert strength in a short curing time and reduce energy consumption. It is about.

As climate warming and regulation of carbon emissions become issues, interest in geopolymers, which are cement-free binders, is increasing. Geopolymer binder is a binder that uses fly ash and blast furnace slag, which are industrial by-products instead of cement, and has the advantage of being eco-friendly and less carbon dioxide emissions than conventional cement binders.

In the case of a conventional Portland cement binder, a hydration reaction occurs while being in contact with water to cause hardening, but in the case of a geopolymer binder, a condensation polymerization reaction occurs by an alkali stimulant and hardening occurs.

Precast concrete members using Portland cement-based general concrete are usually produced at the factory through a 24-hour steam curing process, and the concrete members are made using a geopolymer binder composed of fly ash or fly ash and blast furnace slag. In the case of formation, it is subjected to constant temperature and high temperature curing in an alkaline environment for 24 hours to exert crude rigidity, so geopolymer concrete can be seen as a suitable material for precast members that undergo a 24-hour curing process in a factory.

However, it is based on empirical experiments by a number of researchers to perform 24 hours of constant temperature and high temperature curing on geopolymer concrete in a situation where research on geopolymer concrete is currently not completely done.

Therefore, there is a need to propose an efficient curing method so that crude stiffness is exhibited in manufacturing a precast concrete member using a geopolymer binder.

On the other hand, when geopolymer concrete is mixed so as to exhibit an appropriate strength by using a geopolymer binder of fly ash and blast furnace slag, there is a problem in forming a concrete member because fluidity is not secured due to very rapid hardening of the geopolymer concrete.

Korean Registered Patent Publication No. 10-1748119 (announced on June 16, 2017)

The present invention provides a method for manufacturing a precast geopolymer concrete member that can efficiently exhibit strength in a short curing time and reduce energy consumption when manufacturing a precast concrete member using a geopolymer binder of fly ash and blast furnace slag. do.

In addition, when geopolymer concrete is mixed using a geopolymer binder, a precast geopolymer concrete member manufacturing method with enhanced fluidity that can easily form a precast geopolymer concrete member by securing the fluidity of the non-hardened geopolymer concrete Provides.

According to an aspect of the present invention, mixing a geopolymer binder comprising fly ash and blast furnace slag, an alkali stimulating agent, water, and a non-hardened geopolymer concrete composition comprising an aggregate; Pouring the non-hardened geopolymer concrete composition into a mold according to the precast geopolymer concrete member to be manufactured; Curing the geopolymer concrete composition at a high temperature and constant temperature for 3 to 5 hours at a maximum curing temperature of 60 to 70°C; Thermally curing the geopolymer concrete composition while reducing the temperature from the maximum curing temperature to a predetermined minimum curing temperature at a constant slope; There is provided a method for manufacturing a precast geopolymer concrete member comprising the step of curing the geopolymer concrete composition at a low temperature and constant temperature for a predetermined time at the lowest curing temperature.

The thermal curing step may include thermal curing for 3 to 13 hours from the maximum curing temperature to a predetermined minimum curing temperature.

The minimum curing temperature is 20 ~ 30 ℃, the step of curing with reduced temperature may be cured by reducing the temperature from the maximum curing temperature to the minimum curing temperature.

The minimum curing temperature is 20 ~ 30 ℃, the step of the low-temperature constant-temperature curing may include the step of low-temperature constant-temperature curing at the lowest curing temperature for 6 to 18 hours.

The sum of the high temperature constant temperature curing time, the reduced temperature curing time, and the low temperature constant temperature curing time may be 24 hours or less.

The mixing of the geopolymer concrete composition may include forming a dry mixing mixture by mixing the geopolymer binder and aggregate including fly ash and blast furnace slag; Adding and mixing an aqueous alkali stimulant solution to the dry bibim mixture to form a blended mixture; It may include the step of forming a pouring mixture by additionally adding and mixing mixed water to the blended mixture.

In the step of forming the blended mixture, the mixing time of the dry bibim mixture and the aqueous alkaline stimulant solution may be 120 to 180 seconds.

The geopolymer binder may include 55 to 80 wt% of fly ash and 20 to 45 wt% of blast furnace slag.

The aggregate includes 227 to 230 parts by weight of coarse aggregate based on 100 parts by weight of the binder; It may include 120 to 123 parts by weight of fine aggregate based on 100 parts by weight of the binder.

The alkali stimulating agent aqueous solution includes 15 to 20 parts by weight of an aqueous sodium hydroxide (NaOH) solution having a molar concentration (M) of 10 to 12 based on 100 parts by weight of the binder; Silicate produced by mixing 14 to 15 wt% of sodium oxide (Na ₂ O), 34 to 35 wt% of silicon dioxide (SiO ₂ ) and 50 to 52 wt% of distilled water (H ₂ 0) based on 100 parts by weight of the binder Sodium (Na ₂ SiO ₃ ) may contain 40 to 45 parts by weight of an aqueous solution.

The weight ratio of the sodium silicate (Na ₂ SiO ₃ ) to the sodium hydroxide (NaOH) may be 2 to 3.

The mixed water may be added in an amount of 5 to 10 parts by weight based on 100 parts by weight of the binder.

According to an embodiment of the present invention, when a precast concrete member is manufactured using a geopolymer binder of fly ash and blast furnace slag, it is possible to efficiently exhibit strength in a short curing time and reduce energy consumption.

In addition, when the geopolymer concrete is mixed using a geopolymer binder, it is possible to easily form a concrete member by securing the fluidity of the non-hardened geopolymer concrete.

1 is a flow chart of a method for manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.
Figure 2 is a view showing the curing history of the method for manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.
3 is a graph of variables for calculating weight maturity of a method for manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.
4 is a graph comparing compressive strength of a method for manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.
5 is a weight maturity graph of a method for manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.
6 is a change temperature curing history of a compressive strength of 40 MPa according to a method of manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.
7 is a change temperature curing history of 50 MPa compressive strength according to the method of manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.
8 is a change temperature curing history of a compressive strength of 60 MPa according to a method of manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.
9 is a graph showing the change in slump and compressive strength according to the amount of mixed water added additionally.

Since the present invention can apply various transformations and have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all conversions, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, when it is determined that a detailed description of a related known technology may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

Hereinafter, an embodiment of a method for manufacturing a precast geopolymer concrete member according to the present invention will be described in detail with reference to the accompanying drawings, and in the description with reference to the accompanying drawings, the same or corresponding components are given the same reference numbers. And redundant descriptions thereof will be omitted.

1 is a flow chart of a method for manufacturing a precast geopolymer concrete member according to an embodiment of the present invention. And, Figure 2 is a view showing the curing history of the precast geopolymer concrete member manufacturing method according to an embodiment of the present invention, Figure 3 is the weight of the precast geopolymer concrete member manufacturing method according to an embodiment of the present invention It is a graph of variables for calculating maturity, and FIG. 4 is a graph of comparison of compressive strength of a method for manufacturing a precast geopolymer concrete member according to an embodiment of the present invention. And, Figure 5 is a graph of the weight maturity of the precast geopolymer concrete member manufacturing method according to an embodiment of the present invention. And, Figure 6 is a change in temperature curing history of a compressive strength of 40 MPa according to the method of manufacturing a precast geopolymer concrete member according to an embodiment of the present invention, Figure 7 is a precast geopolymer concrete member manufacturing according to an embodiment of the present invention It is a change temperature curing history of 50 MPa of compressive strength according to the method, and FIG. 8 is a change of temperature curing history of 60 MPa of compressive strength according to the method of manufacturing a precast geopolymer concrete member according to an embodiment of the present invention.

The method for manufacturing a precast geopolymer concrete member according to the present embodiment includes the steps of mixing a geopolymer binder including fly ash and blast furnace slag, an alkali stimulating agent, water, and a non-hardened geopolymer concrete composition including aggregate; Pouring a non-hardened geopolymer concrete composition into a mold according to the precast geopolymer concrete member to be manufactured; Curing the geopolymer concrete composition at a maximum curing temperature of 60 to 70° C. for 3 to 5 hours at a high temperature and constant temperature; Subjecting the geopolymer concrete composition to a predetermined minimum curing temperature from a maximum curing temperature to a predetermined minimum curing temperature while reducing temperature at a constant gradient; It includes the step of curing the geopolymer concrete composition at a low temperature and constant temperature for a predetermined time at the lowest curing temperature.

Geopolymer concrete can be manufactured using fly ash of a low calcium system with a low calcium component as the main material, or blast furnace slag fine powder of a high calcium system with a large amount of calcium as the main material. The geopolymer concrete according to the embodiment uses fly ash as a main material and attaches blast furnace slag to secure fluidity, and fly ash and blast furnace slag are used as a geopolymer binder.

In the case of manufacturing a non-hardened geopolymer concrete composition by mixing geopolymer concrete to exert adequate strength using a geopolymer binder of fly ash and blast furnace slag, due to the characteristics of the geopolymer concrete, curing occurs at the same time as the mixture, ensuring fluidity. There is a problem that the workability for forming a concrete member is very weak.

On the other hand, this rapid setting of geopolymer concrete has an aspect suitable for precast concrete members, so it has the advantage of being able to easily form precast concrete members using geopolymer concrete if the fluidity of geopolymer concrete is secured during initial pouring. .

This embodiment relates to a method of manufacturing a precast geopolymer concrete member by utilizing the rapid setting of such geopolymer concrete.

Hereinafter, a method of manufacturing a precast geopolymer concrete member according to the present embodiment will be described in detail.

First, a geopolymer binder containing fly ash and blast furnace slag, an alkali stimulant, and a non-hardened geopolymer concrete composition containing water and aggregate are mixed (S100). This step is a step of forming a non-hardened geopolymer concrete composition by using a geopolymer binder containing fly ash and blast furnace slag.As described above, due to the characteristics of the geopolymer concrete, hardening may occur simultaneously with the blending. It is necessary to secure liquidity for city workability.

The method of mixing a non-hardened geopolymer concrete composition according to the present embodiment includes the steps of forming a dry mixing mixture by mixing a geopolymer binder including fly ash and blast furnace slag and an aggregate; Adding and mixing an aqueous alkali stimulant solution to the dry bibim mixture to form a blended mixture; And adding and mixing mixed water to the blended mixture to form a pouring mixture.

The bonding between the aggregates is formed as curing occurs according to the reaction of the geopolymer binder and the aqueous alkali stimulating agent solution to be described later. Since the curing speed is high, it is difficult to uniformly mix the materials when they are added and mixed. Therefore, in this embodiment, before the alkaline stimulant aqueous solution is added, the geopolymer binder including fly ash and blast furnace slag and the aggregate are mixed only with the aggregate so that the binder is evenly coated on the surface of the aggregate.

In the case of geopolymers such as blast furnace slag and fly ash, hydration reaction does not occur due to contact with water, and hardening occurs while reacting with an alkali stimulant.In this embodiment, an alkali stimulant and water are not separately added, and the alkali stimulant and water are mixed. Therefore, the method of mixing in the form of an aqueous alkaline stimulant solution was adopted.

As the alkali stimulant, sodium hydroxide (NaOH) and sodium silicate (Na ₂ SiO ₃ ) can be applied in consideration of the strength and economic feasibility of geopolymer concrete, and mixed in an aqueous solution form considering wet mixing with the dry bibim mixture. Form a mixture.

The blended mixture is a blend before the mixed water is additionally added to secure fluidity, and the curing reaction is rapidly occurring as the geopolymer binder and the aqueous alkali stimulating agent are mixed.

The concrete is hardened even in the state of the mixed mixture, but in order to form a concrete member like a precast concrete member, it is necessary to pour unhardened geopolymer concrete.In the case of the mixed mixture state, the fluidity is not secured due to rapid curing Can't secure workability. In this embodiment, fluidity is secured by additionally adding mixed water while forming a blended mixture as described later.

The mixing time of the dry bibim mixture and the aqueous alkaline stimulant solution proceeds in the range of 120 to 180 seconds. If the mixing time is less than 120 seconds, complete mixing is difficult, and if the mixing time is longer than 180 seconds, curing proceeds too much, and it is difficult to secure fluidity even if additional mixed water is added as described later.

Even in the state of a blended mixture, pourability cannot be secured because fluidity is not secured due to rapid curing. Therefore, in the present embodiment, additionally mixed water was added in the mixed mixture state and mixed again to secure the fluidity of the geopolymer concrete. Depending on the mixing ratio, a binder, an aqueous alkali stimulant solution, an aggregate, etc. are mixed in a mixed state, and when a mixed mixture is formed, the mixed water is immediately added and mixed again with a mixer to form a poured mixture. The pouring mixture is in a state in which fluidity is secured, and workability can be secured when pouring into a formwork.

Next, a non-hardened geopolymer concrete composition is poured into a mold according to the precast geopolymer concrete member to be manufactured (S200). Precast concrete members are preformed at a factory such as concrete blocks, beams, columns, slabs, etc., and a mold is manufactured according to the shape of the precast geopolymer concrete member to be manufactured, and a pouring mixture that has secured fluidity according to the method described above. The unhardened geopolymer concrete composition is poured into the mold.

Next, curing is performed on the poured unhardened geopolymer concrete composition. In this embodiment, as shown in FIG. 2, the step of curing the geopolymer concrete composition at a maximum curing temperature of 60 to 70° C. for 3 to 5 hours at a high temperature and constant temperature (S200); Thermally curing the geopolymer concrete composition while reducing the temperature from the maximum curing temperature to the predetermined minimum curing temperature at a constant slope (S400); The geopolymer concrete composition is cured at a low temperature and constant temperature for a certain time at a minimum curing temperature (S500).

Unlike the hydration reaction of conventional cement concrete, the condensation polymerization reaction takes place by an alkali stimulant and rapid hardening occurs at the same time as mixing. In the past, it is cured for 24 hours by maintaining a constant high temperature of 50 ~ 70℃. How to proceed was known.

However, according to the hardening experiment on geopolymer concrete, the hardening completion time may vary slightly depending on the amount of blast furnace slag, but it was found that the hardening was rapidly completed during the initial few hours after mixing, and the hardening was completed quickly afterwards. It was found that the maturity, which determines the compressive strength of, is influenced by the initial curing temperature and the duration. In this case, the initial curing temperature is cured at a high temperature of about 50 to 70° C. at the beginning of curing, and is similar to the maximum curing temperature T _{max in the} present invention.

In accordance with these experimental results, the present invention proposes a curing technique capable of expressing the maturity as a weight function as a function of the maximum curing temperature during curing.

According to the existing simple maturity concept, the energy index represented by the graph area of the curing temperature and curing time within 28 days of curing period and the strength of general concrete are assumed to be proportional. According to the experiment, geopolymer concrete In the case of, the existing concept of simple maturity is not applied.

Therefore, in the present invention, the concept of weighted maturity (W) is introduced with the maximum curing temperature (T _max ), which has the greatest effect on the strength development of geopolymer concrete, as a variable.

3 is a weight maturity graph of a method for manufacturing a precast geopolymer concrete member according to the present embodiment. According to the concept of weight maturity, as shown in the graph of FIG. 3, different weighted function values are applied to the maximum curing temperature applied during curing, and there is no strength expression for all curing temperatures after 28 days of age. do.

4 is a comparison graph of compressive strength of a method for manufacturing a precast geopolymer concrete member according to the present embodiment, as shown in the graph of FIG. 4 when comparing the predicted value of compressive strength of geopolymer according to the concept of weight maturity and the result of experimental measurement. , It was found that the compressive strength value by weight maturity predicted the experimental value well.

By introducing the concept of weighted maturity (W) according to the present invention, the following strength expression equation [Equation 1] is derived.

[Equation 1]

In the above [Equation 1], W(T _max ,t _k ) is the weight maturity, which is derived by the following [Equation 2] through regression analysis according to the experiment.

[Equation 2]

here,

In the above [Equation 2], F ₁ , F ₂ , F ₃ are calculated by applying a regression analysis as shown in FIG. 5 for the maximum curing temperature by applying 11 curing histories to the mixing ratio applied in the experiment. .

The typical compression strength of geo polymer concrete based on equal weight of maturity concept 40MPa, 40MPa, look derive optimum curing history about 50MPa, also, the maximum curing temperature, as shown in 2 (T _max) by a predetermined time (t ₁ ) During the'high temperature constant temperature curing' section, and after curing at the maximum curing temperature, a constant slope ((T _min -T _max )/(t ₂ -t ₁ ) for a certain period of time (t ₂ -t ₁ ) )) to the minimum curing temperature (T _min ) and curing with the'low temperature curing' section, and the'low temperature constant temperature curing' section where curing is performed at the minimum curing temperature (T _min ) for a certain period of time after reduced temperature curing The optimal curing history of curing is derived.

However, among the above curing sections, as described above, in the case of geopolymer concrete, considering that rapid hardening occurs during the initial few hours after mixing, curing is performed for a certain period of time (t ₁ ) at the maximum curing temperature (T _max ). The'high temperature, constant temperature curing' section is very important. Therefore, in this example, it is proposed to cure at a high temperature and constant temperature for 3 to 5 hours (t ₁ ) at a maximum curing temperature (T _max ) of 50 to 70° C. after geopolymer concrete is placed.

6 to 8 are the optimal curing history derived based on the concept of weight maturity for each of the compressive strengths 40 MPa, 40 MPa, and 50 MPa.In FIG. 6, for the compressive strength 40 MPa, the maximum curing temperature (T _max ) 60°C (( a)), 50 ℃ (Fig. 6 (b)) high temperature constant temperature curing for 3 to 5 hours, respectively, in Fig. 7 for the compressive strength of 50 MPa, the maximum curing temperature (T _max ) 70 ℃ (Fig. 7 (a)), 60 ℃ (Fig. 7 (b)), high-temperature constant temperature curing is performed for 3 to 5 hours, respectively, and for the compressive strength of 60 MPa in Fig. 8, the maximum curing temperature (T _max ) 70°C (Fig. For (a) and (b) of 6, it is shown that high-temperature constant-temperature curing is performed for 3 to 4 hours.

On the other hand, the temperature-sensitive curing section, after curing at the maximum curing temperature of 60 ~ 70 ℃, while reducing the temperature at a constant slope from the maximum curing temperature (T _max ) to the predetermined minimum curing temperature (T _min ) for 3 to 13 hours. Proceed with thermal curing.

Looking at the temperature-sensitive curing section of FIG. 6, for a compressive strength of 40 MPa, heat-sensitive curing (FIG. 6(a)) was performed for 4 hours from the maximum curing temperature of 70° C. to the lowest curing temperature of 20° C., and at a maximum curing temperature of 60° C. Thermal curing (FIG. 6(b)) is performed for 13 hours to the minimum curing temperature of 40°C.

Looking at the temperature-sensitive curing section of FIG. 7, for a compressive strength of 50 MPa, thermal curing (FIG. 7 (a)) was performed for 3 hours from the maximum curing temperature of 80°C to the lowest curing temperature of 20°C, and at the maximum curing temperature of 70°C. Thermal curing (FIG. 6(b)) is performed for 13 hours to the minimum curing temperature of 20°C.

Looking at the temperature-sensitive curing section of FIG. 8, for a compressive strength of 60 MPa, thermal curing (FIG. 8 (a)) is performed for 10 hours from the maximum curing temperature of 80° C. to the lowest curing temperature of 20° C., and at the maximum curing temperature of 80° C. Heat-sensitive curing (FIG. 8(b)) is performed for 8 hours to a minimum curing temperature of 20°C.

And, in the low temperature constant temperature section, after the thermal curing is performed, the low temperature constant temperature curing is performed at a minimum curing temperature of 20 to 30°C for 6 to 18 hours. The minimum curing temperature can be determined at room temperature, but it may be determined higher than room temperature depending on the change-temperature curing history in precast factory manufacturing.

Looking at the low-temperature constant-temperature curing section of FIG. 6, for a compressive strength of 40 MPa, when high-temperature constant-temperature curing is performed at a maximum curing temperature of 70° C., a low-temperature constant-temperature curing for 17 hours at a minimum curing temperature of 20° C. )), and if high-temperature constant-temperature curing is performed at a maximum curing temperature of 70°C, low-temperature constant-temperature curing (FIG. 6(b)) is performed for 6 hours at a minimum curing temperature of 40°C after thermal curing.

Looking at the low-temperature constant-temperature curing section of FIG. 7, for a compressive strength of 50 MPa, when high-temperature constant-temperature curing is performed at a maximum curing temperature of 80° C., low-temperature constant-temperature curing for 18 hours at a minimum curing temperature of 20° C. )), and if high-temperature constant-temperature curing is performed at a maximum curing temperature of 70°C, low-temperature constant-temperature curing (FIG. 7(b)) is performed for 8 hours at a minimum curing temperature of 20°C after thermal curing.

Looking at the low-temperature constant-temperature curing section of FIG. 8, for a compressive strength of 60 MPa, when high-temperature constant-temperature curing is performed at a maximum curing temperature of 80° C., a low-temperature constant-temperature curing for 11 hours at a minimum curing temperature of 20° C. )), and if the high-temperature constant-temperature curing is performed at the maximum curing temperature of 80°C, the low-temperature constant-temperature curing (FIG. 7(b)) is performed for 12 hours at the minimum curing temperature of 20°C after the reduced-temperature curing.

On the other hand, by setting the sum of the above-described, high temperature constant temperature curing time, low temperature constant temperature curing time, and low temperature constant temperature curing time to 24 hours or less, the change temperature curing history can be determined. In the case of geopolymer concrete, there is an aspect that is suitable for forming precast concrete members due to the rapid setting of rapid hardening at the initial stage.In consideration of factory manufacturing, the productivity of precast geopolymer concrete members is improved by performing rapid curing within 24 hours. I can make it. Referring to FIGS. 6 to 7, it can be seen that the change-temperature curing history is derived based on the 24-hour curing time.

As described above, in the present embodiment, the heat energy consumption consumed in the curing process is efficiently reduced by gradually lowering the temperature and curing according to the above experiment instead of performing high-temperature constant-temperature curing that requires a large amount of energy as in the prior art. Can be reduced by

Hereinafter, a non-hardened geopolymer concrete composition used in the method for manufacturing a precast geopolymer concrete member according to the present embodiment will be described in detail.

The non-hardened geopolymer concrete composition according to this embodiment is, based on 100 parts by weight of the geopolymer binder containing 55 to 80 wt% of fly ash and 20 to 45 wt% of blast furnace slag, and hydroxylation of 10 to 12 molar concentration (M) 15 to 20 parts by weight of sodium (NaOH) aqueous solution; Sodium silicate (Na ₂ SiO ₃ ) aqueous solution produced by mixing 14 ~ 15 wt% of sodium oxide (Na ₂ O), 34 ~ 35 wt% of silicon dioxide (SiO ₂ ) and 50 ~ 52 wt% of distilled water (H ₂ 0) A blended mixture containing 40 to 45 parts by weight, further comprising 5 to 10 parts by weight of a mixed water added after mixing the blended mixture.

Fly ash is the main material of the binder and is involved in the development of the strength of the geopolymer concrete. When the design compressive strength is 40 MPa or more, 55 to 80 wt% of the total binder is appropriate. If it is less than 55 wt%, the amount of hardening reaction of fly ash is small, so it is difficult to develop proper compressive strength. If it is more than 80 wt%, it is difficult to secure workability due to fast hardening.

Blast furnace slag is a part of the bonding material added like fly ash, and affects the strength and fluidity of geopolymer concrete. If the blast furnace slag is less than 20 wt% of the total binder, it is difficult to develop the target compressive strength and the mobility for the formation of the concrete member decreases.If the blast furnace slag is more than 45 wt% of the total binder, the target is It is difficult to express the compressive strength.

In the case of geopolymers such as blast furnace slag and fly ash, hydration does not occur due to contact with water, and hardening occurs when the alkaline stimulating agent contained in the alkaline stimulating agent aqueous solution reacts with the geopolymer.

As the alkali stimulator, sodium hydroxide (NaOH) and sodium silicate (Na ₂ SiO ₃ ) are applied in consideration of the strength development and economical efficiency of geopolymer concrete. Mix in form to form a blended mixture

The alkali stimulating agent aqueous solution according to this embodiment is 15 to 20 parts by weight of an aqueous sodium hydroxide (NaOH) solution having a molar concentration (M) of 10 to 12 based on 100 parts by weight of the binder, and sodium oxide (Na ₂ O) based on 100 parts by weight of the binder. ) 14 ~ 15 wt%, silicon dioxide (SiO ₂ ) 34 ~ 35 wt% and distilled water (H ₂ 0) 50 ~ 52 wt% sodium silicate (Na ₂ SiO ₃ ) aqueous solution 40 ~ 45 parts by weight included do.

Since sodium hydroxide is not well soluble in water due to its physical properties, an aqueous solution is prepared and blended in a 10 to 12 molar concentration (M). Sodium silicate (Na ₂ SiO ₃ ) is an aqueous solution by mixing 14 to 15 wt% of sodium oxide (Na ₂ O), 34 to 35 wt% of silicon dioxide (SiO ₂ ) and 50 to 52 wt% of distilled water (H ₂ 0) Prepared and blended.

On the other hand, the weight ratio of sodium silicate (Na ₂ SiO ₃ ) to the added sodium hydroxide (NaOH) is maintained between 2 and 3. That is, 2 to 3 times more sodium silicate is added to the sodium hydroxide by weight. According to the experiment, if the weight ratio was maintained, the design strength could be expressed without decreasing the strength.

The blended mixture is a blend before the additionally added mixed water is added in order to secure fluidity, and the geopolymer binder and the alkaline stimulating agent aqueous solution are mixed and the curing reaction is rapidly performed.

The concrete is hardened even in the state of the mixed mixture, but in order to form a concrete member like a precast concrete member, it is necessary to pour unhardened geopolymer concrete.In the case of the mixed mixture state, the fluidity is not secured due to rapid curing Can't secure workability. In this embodiment, the fluidity is secured by additionally adding mixed water while the blended mixture is formed.

The additionally added mixed water is added to the blending mixture in an amount of 5 to 10 parts by weight based on 100 parts by weight of the binder. If less than 5 parts by weight of mixed water is added to 100 parts by weight of the binder, fluidity cannot be secured, and if more than 10 parts by weight of mixed water is added, fluidity is secured, but design strength is difficult to be expressed.

Aggregate is 227 to 230 parts by weight of coarse aggregate based on 100 parts by weight of the binder; It is mixed in 120 to 123 parts by weight of fine aggregate based on 100 parts by weight of the binder. The amount of aggregate may be determined by a conventional cement concrete mixing design method, and in this embodiment, 227 to 230 parts by weight of a coarse aggregate based on 100 parts by weight of a geopolymer binder including fly ash and blast furnace slag; A form mixed with 120 to 123 parts by weight of fine aggregate is suggested based on 100 parts by weight of the binder.

The geopolymer concrete composition according to this embodiment will be described through the following examples. However, since the following examples are for illustrating the present invention, the present invention is not limited thereto.

(Example)

In the examples, as shown in Table 1, for each of the blending strengths 40 MPa, 40 MPa, and 50 MPa, the blends other than the geopolymer binder were made constant as shown in Table 1 below, and the relative amounts of fly ash and blast furnace slag as geopolymer binders A specimen was prepared by changing the values to measure the compressive strength and slump.

According to the above-described method for producing geopolymer concrete with enhanced fluidity, the geopolymer concrete composition is first mixed with the geopolymer binder and aggregate evenly, and then a 12 molar concentration (M) sodium hydroxide (NaOH) aqueous solution and silicic acid Sodium (Na ₂ SiO ₃ ) aqueous solution was added and mixed to make a blended mixture, and additionally mixed water was added to finally prepare a poured mixture.

In Table 1 below, the blending values listed in the table are expressed in parts by weight of the composition based on 100 parts by weight of the binder.

division Mixing ratio (parts by weight per 100 parts by weight of binder) combination
burglar
(MPa) Binder (B) aggregate Aqueous alkali stimulant solution Mixed water Fly ash Blast Furnace Slag Fine aggregate
(sand) Coarse aggregate
(Pebble) Sodium hydroxide
(12M) Sodium silicate Example 1 30 80 20 123 227 20 40 5 Example 2 40 70 30 Example 3 50 60 40

* The values in Table 1 are expressed in parts by weight of the composition based on 100 parts by weight of the binder

Performance evaluation result according to the embodiment division Compressive strength (MPa) Slump (mm) Example 1 31.2 220 Example 2 43.2 232 Example 3 54.8 217

As a result of testing the compressive strength according to KS L ISO 679 for the specimen prepared according to the formulation of the examples in Table 1, Example 1 (mixing strength 40 MPa), Example 2 (mixing strength 50 MPa), Example 3 ( For each of the blending strengths of 60 MPa), the results were 31.2 MPa, 43.2 MPa, and 54.8 MPa, showing a compressive strength greater than the target blending strength.

In addition, the slump test was carried out according to KL F 2402, and Example 1 (mixing strength of 40 MPa), Example 2 (mixing strength of 50 MPa), and Example 3 (mixing strength of 60 MPa) were respectively 220 mm, 232 mm, and 217 mm. It turns out that it has secured the liquidity that can be poured.

On the other hand, with respect to the mixing ratio of Example 1, the amount of mixed water was 0 parts by weight (Example 4), 5 parts by weight (Example 5), 10 parts by weight (Example 6) without mixing water based on 100 parts by weight of the binder. ) To measure the compressive strength and perform a slump test.

9 is a graph showing the change in the slump and compressive strength according to the amount of additionally added mixed water.Example 4, Example 5, Example 6, respectively, showing the compressive strength of 32.1 MPa, 31.2 MPa, 30.1 MPa In the case of Example 4, in which the mixing strength was reached, but the mixed water was not added, the slump value was almost 0 mm, and Example 5 and Example 6 were 220 mm and 260 mm, respectively, indicating that the flowability for concrete pouring was secured.

Although the embodiments of the present invention have been described above, the spirit of the present invention is not limited to the embodiments presented in the present specification, and those skilled in the art who understand the spirit of the present invention will add components within the scope of the same spirit. It will be possible to easily propose other embodiments by changing, deleting, adding, etc., but it will be said that this is also within the scope of the present invention.

Claims (12)

Mixing a geopolymer binder comprising fly ash and blast furnace slag, an alkali stimulating agent, water, and a non-hardened geopolymer concrete composition comprising an aggregate;
Pouring the non-hardened geopolymer concrete composition into a mold according to the precast geopolymer concrete member to be manufactured;
Curing the geopolymer concrete composition at a high temperature and constant temperature for 3 to 5 hours at a maximum curing temperature of 60 to 70°C;
Thermally curing the geopolymer concrete composition while reducing the temperature from the maximum curing temperature to a predetermined minimum curing temperature at a constant slope;
Precast geopolymer concrete member manufacturing method comprising the step of curing the geopolymer concrete composition at a low temperature and constant temperature for a predetermined time at the lowest curing temperature.
The method of claim 1,
The thermal curing step,
A method for manufacturing a precast geopolymer concrete member comprising the step of thermally curing for 3 to 13 hours from the maximum curing temperature to a predetermined minimum curing temperature.
The method of claim 2,
The minimum curing temperature is 20 ~ 30 ℃,
The thermal curing step,
A method of manufacturing a precast geopolymer concrete member, characterized in that curing by reducing the temperature from the highest curing temperature to the lowest curing temperature.
The method of claim 2,
The minimum curing temperature is 20 ~ 30 ℃,
The step of curing the low temperature constant temperature,
Precast geopolymer concrete member manufacturing method comprising the step of curing at a low temperature for 6 to 18 hours at the lowest curing temperature.
The method of claim 4,
The high-temperature constant temperature curing time, the reduced temperature curing time, and the sum of the low-temperature constant temperature curing time is 24 hours or less, characterized in that the precast geopolymer concrete member manufacturing method.
The method of claim 1,
The step of mixing the geopolymer concrete composition,
Forming a dry mixing mixture by mixing the geopolymer binder and aggregate including fly ash and blast furnace slag;
Adding and mixing an aqueous alkali stimulant solution to the dry bibim mixture to form a blended mixture;
A method for manufacturing a precast geopolymer concrete member comprising the step of forming a pouring mixture by additionally adding and mixing mixed water to the blended mixture.
According to claim 6
In the step of forming the blending mixture,
The mixing time of the dry bibim mixture and the alkali stimulating agent aqueous solution is 120 to 180 seconds, characterized in that the precast geopolymer concrete member manufacturing method.
The method of claim 6,
The geopolymer binder,
Fly ash 55 to 80 wt% and blast furnace slag 20 to 45 wt%, characterized in that it comprises a precast geopolymer concrete member manufacturing method.
The method of claim 6,
The aggregate,
227 to 230 parts by weight of coarse aggregate based on 100 parts by weight of the binder;
A method for manufacturing a precast geopolymer concrete member, comprising 120 to 123 parts by weight of fine aggregate based on 100 parts by weight of the binder.
The method of claim 8,
The alkaline stimulant aqueous solution,
15 to 20 parts by weight of sodium hydroxide (NaOH) aqueous solution of 10 to 12 molar concentration (M) based on 100 parts by weight of the binder;
Silicate produced by mixing 14 to 15 wt% of sodium oxide (Na ₂ O), 34 to 35 wt% of silicon dioxide (SiO ₂ ) and 50 to 52 wt% of distilled water (H ₂ 0) based on 100 parts by weight of the binder Sodium (Na ₂ SiO ₃ ), characterized in that containing 40 to 45 parts by weight of an aqueous solution, precast geopolymer concrete member manufacturing method.
The method of claim 10,
The weight ratio of the sodium silicate (Na ₂ SiO ₃ ) to the sodium hydroxide (NaOH) is 2 to 3, the method of manufacturing a precast geopolymer concrete member.
The method of claim 8,
The mixed water,
A method for manufacturing a precast geopolymer concrete member, characterized in that 5 to 10 parts by weight is added based on 100 parts by weight of the binder.

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