KR101065179B1 - Nature-friendly precast concrete with low carbon and method of the same - Google Patents

Abstract

The present invention relates to an eco-friendly low-carbon precast concrete having an effect of reducing CO _{2 by} reducing unit cement amount and steam curing energy through an optimal mixing design using eco-friendly low-carbon cement, one cement or three cements, the cement 100 parts by weight of water 40-55 parts by weight, sand 230-250 parts by weight, aggregate 280-300 parts by weight and concrete admixtures, the admixture for concrete mixing is characterized in that 1% by weight based on the total weight of the cement In addition, the environmentally friendly low carbon precast concrete according to the present invention has a high initial heat of hydration, thereby making it possible to secure early demolding strength, and reduce CO ₂ due to a reduction in unit cement amount and high temperature steam curing energy.

Description

Nature-friendly precast concrete with low carbon and Method of the same}

The present invention relates to precast concrete, and to an eco-friendly low carbon precast concrete having a reduction effect of CO ₂ through reduction of unit cement amount and steam curing energy through optimal mixing design using eco-friendly low carbon cement, and a manufacturing method thereof. .

In recent years, intensive land use caused by urbanization has resulted in large-scale and ultra-high-rise buildings. As a result, the production and consumption of cement are increasing in proportion to the economic development rate, and the amount of CO ₂ is increasing.

Moreover, recent economic growth and industrial development in the manufacture of concrete blocks increased to improved the quality of human life to the composition pleasant environment of residential living areas, such as parks, sidewalks, trails and is a CO ₂ major cause of global warming, It is generated in large quantities, and the use of portland cement usually generates considerable heat during the hydration of cement, which causes the abnormal weather of the earth frequently and the speed of rising seawater temperature is increasing.

To solve this problem, we actively use two- or three-component mixed cements using large amounts of blast furnace slag powder, fly ash, and silica fume, which can reduce the amount of ordinary Portland cement that generates a large amount of CO ₂ and hydration heat. There is an urgent need in the construction industry for the development of highly durable eco-friendly concrete compositions incorporating construction materials and permeable pavement using the same.

In addition, recently, concrete pavement used in parks, lakes, sidewalks and raceways, trails, etc. has been using only ordinary Portland cement as a binder by emphasizing the strength, durability, and publicity of the pavement plate. Is giving you an offensive image. Currently, in the construction industry, it is required to use two-component or three-component mixed cements incorporating eco-friendly admixtures rather than portland cement in order to give an environmentally friendly image of housing construction and downtown.

In particular, precast concrete products are increasing in order to improve air shortening and workability, and the amount of CO ₂ generated is further increased due to an increase in the amount of fossils used when producing these products.

Therefore, there is an urgent need for the development of an optimal concrete mix design for reducing the amount of CO ₂ generated during the production of precast concrete members and the development of technology for reducing steam curing energy.

Therefore, the first problem to be solved by the present invention is easy to secure early demolding strength due to the high initial heat of hydration, and provides an environmentally friendly low carbon precast concrete with CO ₂ reduction effect due to the reduction of unit cement amount and high temperature steam curing energy It is.

The second problem to be solved by the present invention is to provide a method for producing the environmentally friendly low carbon precast concrete.

The present invention to achieve the first object,

1 type cement or 3 types cement, 40-55 weight part of water, 230-250 weight part of sand, 280-300 weight part of aggregates, and the admixture for concrete mixing, The admixture for concrete mixing is the said It provides a precast concrete, characterized in that 1% by weight based on the total weight of cement.

According to one embodiment of the present invention, the first cement may be a unit cement amount of 340-360 /, the three cements may be a unit cement amount of 320-330 /.

According to one embodiment of the present invention, the aggregate size is 5-25, and the admixture for mixing concrete may be a polycarboxylic acid-based compound.

According to one embodiment of the present invention, the precast concrete may be prepared by a steam curing method for curing concrete by injecting steam of 50-80.

According to another aspect of the present invention,

5-25 size aggregate and sand are mixed, cement is added to the mixture and mixed, water and admixture is mixed to obtain a precast concrete compound, and 50-80 steam is injected into the concrete compound to provide hot steam. It provides a precast concrete manufacturing method comprising the step of curing.

According to an embodiment of the present invention, the cement may be one kind of cement or three kinds of cement, the one kind of cement may have a unit cement amount of 340-360 /, and the three kinds of cement may have a unit cement amount of 320-330 /. .

According to one embodiment of the present invention, the water, sand and aggregate are 40-55 parts by weight, 230-250 parts by weight, 280-300 parts by weight based on 100 parts by weight of the cement, respectively, and the admixture is 1 based on the total weight of the cement. Weight percent.

According to one embodiment of the present invention, the admixture may be a polycarboxylic acid-based compound as admixture for concrete mixing.

Eco-friendly low carbon precast concrete according to the present invention has a high initial heat of hydration it is easy to ensure early demolding strength, there is a CO ₂ reduction effect due to the reduction of unit cement amount and high temperature steam curing energy.

1 is a graph showing the mortar compressive strength of one, three kinds of cement according to an embodiment of the present invention.
Figure 2 is a graph showing the compressive strength of concrete using one, three kinds of cement according to an embodiment of the present invention.
3 is a graph showing physical and chemical phenomena according to the temperature history during concrete curing by steam curing.
Figure 4 is a graph showing the maximum temperature holding time during steam curing using a kind of cement according to an embodiment of the present invention.
5 is a graph showing the maximum temperature holding time during steam curing using three kinds of cement according to an embodiment of the present invention.
6 is a graph showing the results of compressive strength for precast concrete according to an embodiment of the present invention.
7 is a graph showing the amount of CO ₂ generated for precast concrete according to an embodiment of the present invention.
8 is a graph showing the results of freeze-thawing experiments of precast concrete according to an embodiment of the present invention.
Figure 9 is a graph showing the result of measuring the change in length for precast concrete according to an embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention is characterized in that the design of the raw material used in the production of precast concrete products and the formulation that can reduce the amount of CO ₂ generated during curing and its manufacturing method. In other words, it uses one or three types of cements that can produce eco-friendly low-carbon concrete in components, and reduces the amount of CO ₂ generated by the optimal blending design, thereby reducing the steam curing energy used in the manufacture of concrete blocks. It is characterized by reducing the amount of CO ₂ generated.

Concrete according to the present invention includes one or three cements, 40-55 parts by weight of water, 230-250 parts by weight of sand, 280-300 parts by weight of aggregates and admixtures for mixing concrete, based on 100 parts by weight of the cement. Concrete admixture is characterized in that 1% by weight based on the total weight of the cement.

The three cements are characterized in that the C ₃ S content is high, the initial strength is enhanced, the powder is high, the initial and long-term strength is high.

The present invention is characterized by the effect of reducing the amount of CO ₂ generated by the reduction of the amount of unit cement by the optimum blending design. Accordingly, the first cement may have a unit cement amount of 340-360 /, and the three cements may have a unit cement amount of 320-330 /.

In addition, the present invention is mixed with the aggregate and sand, and after mixing the cement into the mixture, and then mixed with water and admixture to obtain a precast concrete blend, by injecting 50-80 steam to the concrete blend to hot steam curing It characterized in that to produce precast concrete.

In general, the most commonly used accelerated curing method for secondary concrete products is steam curing. As shown in Figure 3, the steam curing is composed of five stages of preheating (Heating) maintenance curing (heating) curing postpose (Prepose period).

This is a curing method that improves the initial compressive strength by promoting the curing of concrete by injecting hot steam, the curing product is a steam curing temperature history that is physically or chemically changed by the hot steam in the curing system. Shown in

The present invention is a pre-cure for 1.5-2.5 hours, preferably 2 hours, the temperature is raised to 50-80 to maintain the temperature for 2-6 hours, then the temperature is lowered and post-cure for 1-5 hours Can be.

According to a preferred embodiment of the present invention, the maximum temperature during steam curing is 65, the holding time during the maintenance curing may be one kind of cement holding 4 hours, three kinds of cement holding 1 hour.

Hereinafter, the present invention will be described in more detail with reference to preferred examples. However, these examples are intended to illustrate the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited thereto.

<Examples>

In the present invention, one or three kinds of cements having chemical components and physical properties as shown in the following [Table 1] and [Table 2] were used. Table 1 shows the chemical components of the first and third types of cement, and Table 2 shows the physical performance of the cement.

cement
Chemical composition (%) SiO ₂ Al ₂ o ₃ Fe ₂ O ₃ CaO MgO Na ₂ O K ₂ O SO ₃ Lg-loss Type 1 20.7 5.9 3.2 63.1 3.2 0.09 0.84 1.6 1.2 3 types 19.7 5.9 3.0 62.1 3.0 0.10 0.75 4.2 1.1

cement
Laine
(Cm 2 / g) congelation Compressive strength (MPa) First (m0 Termination (h) 1 day 3 days 7 days 14 days Type 1 3,200 300 7:10 - 20 28.5 37.5 3 types 4,000 190 5:00 17.5 29.5 37.0 47.0

1 and 2 are shown for the compressive strength of one, three kinds of cement according to an embodiment of the present invention.

Experimental Example

(1) Using three kinds of cement used to secure early strength, slump: 150mm, compressive strength: demolding (10hr) -10MPa, 14 days-27MPa for concrete production The concrete for each variable was fabricated and examined the physical properties such as compressive strength (Φ10 × 20cm), freeze-thaw resistance (10 × 10 × 40cm), and dry shrinkage (10 × 10 × 40cm).

Low carbon concrete was prepared according to the mixing design shown in [Table 3] below, and the compressive strength was measured using a specimen of Φ10 × 20cm, and a dry shrinkage and freeze-thawing mold was produced using a 10 × 10 × 40cm length varying mold. It was.

division
W / C
(%) S / a
(%) Gmax
(Mm) Unit material weight (㎏ / ㎥) Water Cement Sand Gravel AD 1 (1 type) 47.0
46.0

52


165

351 813
1002


One%
2 (3 types) 3 (three kinds) 40.0 44.6 330 831 1001 4 (3 types) 43.0 45.2 311 849 998

After curing the specimen, divided into the following [Table 4], using the steam of high temperature to perform steam curing at the maximum temperature of 65, and then carried out various tests.

division Pre-Nursing Elevated temperature Isothermal Temperature Aftercare 4 hours maintenance 2 2 4 One 2 2 hours maintenance 2 2 2 3 2

(2) Eco-friendly concrete compressive strength test

end. Manufacture of compressive strength specimens (KS F 2403)

The specimen was prepared using a 10 × 20 cm cylindrical mold with a height twice the diameter, and the concrete pour was divided into two layers and filled with the same thickness. The specimens were subjected to steam curing (1, 2) and then polished in the concrete pouring surface after curing for a period of time (immediately after steam curing, 1,7,14 days) in a 20 ± 3 ℃ water bath.

I. Compressive Strength Measurement (KSF2405)

The upper and lower end faces of the specimens and the compression surface of the upper and lower pressure plates were cleaned, and the center of the specimens was set to coincide with the center of the pressure plate within an error within 1% of the specimen diameter, and the load was applied at the same speed so as not to impact the specimens. The rate of loading was such that the rate of compressive stress increase was 0.6 ± 0.4 MPa per second.

After the specimen started to deform rapidly, the adjustment of the speed of loading was stopped and the loading was continued. The maximum load shown in the tester was confirmed until the specimen was destroyed, and the results are shown in the following [Table 5] and FIG. 6.

Cement type
Unit cement amount
Curing method
Compressive strength MPa Demold One 14 Type 1
351
Steam 1 10.1 19.6 28 Steam 2 8.5 17.5 27.4 3 types




351
Steam 1 15.4 27.3 40.8 Steam 2 15.1 23.8 38 330
Steam 1 14.3 24.6 36.8 Steam 2 13.9 23.3 35.5
311 Steam 1 10.3 22.6 27.9 Steam 2 13.2 19.9 23.4

In Table 5, steam 1 indicates 4 hours of isothermal holding, and steam 2 indicates 2 hours of isothermal holding. Since steam 1 must last 6 hours as a boiler, 60 ml of diesel oil is used, whereas steam 2 must last 3 hours as a boiler, resulting in a 50% reduction in CO ₂ .

Referring to FIG. 6, it can be seen that the result of compressive strength analysis showed that in the case of one kind of cement, satisfactory unit cement amount was 350kg / s or less, steam curing maintenance time 4 hours, and storage 2 hours were not satisfied.

In case of 3 types of cement, the application standard was satisfied in all variables except unit cement amount 311kg / holding 2 hours. In the case of the three types of cement, the content of C ₃ S is higher than that of the type 1 cement and the powder is high, and thus the strength improvement rate is about 30% when the same type 3 cement is used.

(2) CO ₂ generation analysis

Analysis of the amount of CO ₂ generation of environmentally friendly precast concrete according to an embodiment of the present invention, the results are shown in Table 6 and FIG.

Cement type
Unit cement amount
Curing method
CO ₂ Occurrence cement Curing Sum Type 1
351
Steam 1 0.282 0.168 0.45 Steam 2 0.282 0.084 0.366 3 types




351
Steam 1 0.294 0.168 0.462 Steam 2 0.294 0.084 0.378 330
Steam 1 0.277 0.168 0.445 Steam 2 0.277 0.084 0.361 311
Steam 1 0.261 0.168 0.429 Steam 2 0.261 0.084 0.345

As shown in the graph of Table 6 and Figure 7, 14 days compressive strength 27MPa When comparing the formulations that can be secured when using the cement amount 350kg or more to maintain the maximum temperature of steam curing 4 hours specifications (14 days 27MPa or more) can be secured, and in case of three types of cement, 320kg or more of strength can be expressed. As a result, roughly 23 ~ 28% reduction is possible.

(3) Freeze-thawing experiment of eco-friendly concrete

Freeze-thawing test of environmentally friendly low carbon concrete according to an embodiment of the present invention was carried out in accordance with KS F 2456 (resistance test method of concrete for rapid freeze-thawing) using an eco-friendly concrete specimen, the freeze-thaw resistance evaluation is 30 Relative dynamic modulus was measured in cycle cycles, the calculation of the relative dynamic modulus is as shown in the following equation and the results are shown in Figure 8 below.

P _C = (n ₁ ² / n ₂ ² ) × 100

Where P _C is the relative dynamic modulus (%) after freeze-thawing C cycles, n ₁ is the transverse primary vibration frequency in the freeze-thawing C cycle, and n ₂ is the transverse primary vibration frequency after the freeze-thawing C cycle.

Here, the freeze-thaw cycle means that the temperature at the center of the specimen is raised from 4 to -18 and then from -18 to 4 in principle, and the temperature of the specimen should not be below -20 or above 6 at any time. The freeze-thawing cycle time is 2 hours or more and 4 hours or less.

In the case of freeze-thawing specimens, the experiment was conducted after 14 days of underwater curing if there is no special specification. Tests were started with the specimens in the melted water at the beginning of the freezing cycle. The freeze thaw cycle withdrew specimens from the device in the thawed state at intervals not exceeding 36 cycles. Immediately afterwards a transverse first frequency test was carried out under a temperature condition of 6 ± 3 ° C., weighed, and then transferred back to the test apparatus. 300 cycles of such cycles were carried out and the experiment was terminated when the durability index became less than 60% during the experiment.

(4) Dry shrinkage test of eco-friendly concrete

The measuring instrument, standard and specimen were maintained at a predetermined temperature for each test 3 hours before the measurement time, and when no specific temperature was specified, the experiment was conducted by maintaining 20 ± 1 ° C.

The dry shrinkage test was conducted in accordance with KS F 2424 (Mortar and Concrete Length Change Test Method) using eco-friendly concrete specimen (10X10X40cm), and the change of length was measured for 8 weeks every 7 days. 9 and [Table 7].

division Underwater 1 Machine 1 Machine 2 Machine 3 Machine 4 Machine 5 Machine 8 Case 13 Type 1 88 -198 -287 -308 -390 -440 -550 -595 3 types 76 -144 -196 -202 -260 -314 -422 -457

Referring to the above [Table 7], it can be seen that in the case of three types of cement, an average shrinkage of about 25% is reduced compared to the first type of cement.

As such, when the precast member is manufactured using the three types of cement according to the present invention, 32.5% of CO ₂ generation is reduced by reducing steam curing energy and unit cement during isothermal step during heating, isothermal, and post curing of steam curing. It can be confirmed.

In addition, considering the stability rate of the concrete mix design, the unit cement amount is most preferably one kind of cement 360kg /, three kinds of cement 320kg /, and the experimental results according to the steam curing time to maintain one type of cement for 4 hours and three kinds of cement 1 hour is preferred. Therefore, concrete revetment block during manufacture three kinds of cement applied when the unit cement content of 10% reduction _{(0.021tonCO 2), (0.084tonCO 2} ) about 25% of (0.105tonCO ₂₎ CO ₂ emissions by 50% steam curing energy savings Reduced, it is possible to manufacture eco-friendly concrete relief block.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the technical idea of the present invention, which also belong to the appended claims. It is natural.

Claims (9)

One kind cement having unit cement amount of 340-360 kg / m 3 or three kinds cement having unit cement amount of 320-330 kg / m 3, 40-55 parts by weight of water, 230-250 parts by weight of sand, aggregate 280 Precast concrete comprising -300 parts by weight and admixture for concrete mixing, wherein the admixture for concrete mixing is 1% by weight based on the total weight of cement.
delete The method of claim 1,
The aggregate is 5-25 mm in size, and the admixture for mixing concrete is a precast concrete, characterized in that the polycarboxylic acid-based compound.
The method of claim 1,
The precast concrete is precast concrete, characterized in that produced by the steam curing method of curing the concrete by injecting steam at 50-80 ℃.
(a) 5-25 mm aggregate and sand are mixed and mixed with one kind cement having unit cement amount of 340-360 kg / m3 or three kinds cement having unit cement amount of 320-330 kg / m3. After mixing with water and admixture to obtain a precast concrete blend; And
(b) injecting steam at 50-80 ° C. into the concrete blend to cure hot steam.
delete The method of claim 5, wherein
The water, sand and aggregate are each 40-55 parts by weight, 230-250 parts by weight, 280-300 parts by weight based on 100 parts by weight of the cement, the admixture is 1% by weight based on the total weight of the cement precast Concrete manufacturing method.
The method of claim 5, wherein
The admixture is a pre-cast concrete, characterized in that the polycarboxylic acid compound as admixture for mixing concrete.
The method of claim 5, wherein
The step (b) is a precast concrete manufacturing method characterized in that the curing by maintaining the high temperature steam of 50-80 ℃ for 1-5 hours.

Images