KR100667631B1 - Concrete additive and concrete composition for reinforcing early strength - Google Patents

Abstract

A concrete additive for improving early strength of concrete composition is provided to be used as a binder for the concrete composition and to give improved initial strength to the concrete composition while not reducing flexibility thereof by comprising inorganic material containing SO3, K, Na and Si ions in specific molar ratios as well as gypsum source. The additive includes: 25-85wt.% of gypsum source; and 15-75wt.% of inorganic material containing SO3, K, Na and Si ions in molar ratios of 5 to 20 : 1 to 10 : 5 to 20 : 2 to 10. The gypsum source comprises 30-98% of gypsum anhydrite, 1-35% of gypsum hemihydrate and 1-35% of gypsum dihydrate. The additive is used to form the early strength concrete composition in a ratio of 0.2 to 5% relative to a binder. The binder further contains 5-70% of industrial byproduct selected from fly ash and furnace slag fine powder relative to total weight of the binder, as well as cement.

Description

Concrete Additive and Concrete Composition for Reinforcing early Strength}

The present invention relates to a concrete admixture for increasing the initial strength and a concrete composition comprising the same, and more particularly, an initial strength capable of compensating for the initial strength deterioration accompanying the use of industrial by-products fly ash and blast furnace slag fine powder in concrete. It relates to a concrete composition for improving the initial strength by admixing concrete admixtures and their mixture.

Currently, the ready-mixed concrete industry uses a variety of industrial by-products fly ash and blast furnace slag. Fly ash is an artificial pozzolanic material, which itself does not cure with water, but has a property of curing by reacting with calcium hydroxide, which is a kind of cement hydrate, in an alkaline atmosphere generated during cement hydration. In addition, the blast furnace slag powder is a latent hydraulic material, which itself has no property of curing with water, but has a property of curing by reacting in an alkaline atmosphere generated during cement hydration.

Both fly ash and blast furnace slag powder have been reported to improve the long-term strength of concrete and to improve some durability, and are used as cement substitutes for most concrete in terms of cost reduction of concrete and effective utilization of industrial by-products. .

However, such fly ash or blast furnace slag powder material has a slow reaction time compared with cement, and thus is limited to active use due to the problem of lowering the initial strength of concrete, which is already accepted as a general phenomenon in the industry. In addition, concrete, which is one of the main materials of construction work, is closely related to the construction period because it limits the formwork removal and subsequent process in relation to the curing time and securing a certain initial strength.

In general, the formwork is removed and subsequent processes are carried out about three days after the concrete is laid. Due to the nature of concrete, the form removal time tends to be delayed further in winter low-temperature environments, which leads to construction delays, resulting in cost of construction companies. It will have a huge impact on management. In addition, the construction period of the construction will lead to the competitiveness of the construction company, so that the formwork of concrete is removed at an early time for the purpose of shortening the construction period, thus adversely affecting the safety of the construction work and the safety of the construction structure itself in the future. There are also examples of giving.

For this reason, Remicon hopes to increase the use of fly ash or blast furnace slag powder for cost reduction, and the construction company wants to increase the early strength of concrete for shortening the construction period and safe construction. It can be a source of dispute. In order to solve these problems, various measures have been proposed so far, but there are some effects or it is difficult to confirm the effects, and in some cases, economic logic is not worth hiring.

On the other hand, in the field of concrete secondary products, which are different from general construction and curing conditions, curing of concrete products is used to improve concrete quality through autoclave or high temperature steam curing. In the case of such curing conditions, There is a situation in which a method for reducing the initial strength of ash or blast furnace slag fine powder can be improved relatively easily. However, this method is possible only in the secondary concrete manufacturing plant and cannot be adopted in the concrete casting for concrete casting, so it is difficult to be accepted as a general solution to the aforementioned problem of early strength degradation throughout the concrete industry.

Therefore, there is a technical request for the development of concrete that does not fall in initial strength while using fly ash and blast furnace slag powder, which are industrial by-products, especially for concrete compositions such as in situ concrete.

Therefore, the present invention has been made to solve the above problems, an object of the present invention is to recycle the industrial by-products such as fly ash and blast furnace slag in concrete and to compensate for the initial strength degradation caused by the resulting fly ash and blast furnace The present invention provides a method for producing a concrete admixture that can improve the initial strength performance of concrete as well as reduce the cost of concrete by increasing the amount of concrete mixed in the slag powder.

The present invention relates to a concrete admixture for initial strength enhancement. Concrete admixture for initial strength enhancement according to the present invention is composed of 25 ~ 85% by weight of gypsum source and SO ₃ , K, Na, and Si ions in a molar ratio of 5 ~ 20: 1 ~ 10: 5 ~ 20: 2 ~ 10 Contains 15 to 75% by weight of minerals.

Here, the gypsum source is preferably composed of anhydrous gypsum 30 to 98%, hemihydrate gypsum 1 to 35%, and dihydrate gypsum 1 to 35%.

The present invention also relates to a concrete composition for initial strength enhancement, including the concrete admixture as described above. The concrete composition of the present invention comprises 0.2 to 5% of the concrete admixture based on the weight of the binder, preferably, 0.2 to 2%. Here, the binder of the concrete may include 5 to 70% of the industrial by-product selected from at least one selected from the group consisting of fly ash and blast furnace slag fine powder in addition to cement based on the total binder weight.

In general, accelerators for promoting the initial strength of concrete, in most cases have the property of reducing the flowability of concrete, and has been used together with other materials to compensate for these properties. However, the gypsum source used in the concrete admixture for increasing the initial strength of the present invention promotes the initial hydration of the cement according to the type and the proper mixing ratio, as well as the ability to secure the fluidity of the concrete up to a certain time (slump loss prevention function). Have Due to these properties, the gypsum source can not only serve to compensate for the disadvantages of the general cement promoter mentioned above, but also allows the concrete composition to be evenly mixed in the mixer when the admixture of the present invention is prepared in concrete. ) Can play a role at the same time. In addition, the gypsum source stimulates the reaction of fly ash and blast furnace slag fine powder by Ca and SO ₃ ions, and also reacts with C ₃ A of cement to hydrate ettringite (3CaOAl ₂ O ₃ · 3CaSO ₄ · 32H ₂ O) It promotes the formation of concrete, thereby promoting the early strength of concrete.

As a material that can be used as a source of such a gypsum source, not only natural anhydrous / half-water / gypsum gypsum used for industrial use but also hydrofluoric acid / phosphate / desulfuric gypsum generated as an industrial by-product can be used. However, the former seems to be preferable. It is preferable to use the gypsum source at 25 to 85% based on the total weight of the admixture. If the amount is too small, it is difficult to achieve the actual performance of the gypsum source, and in too many cases, it is mixed with other components of the admixture of the present invention. It is difficult to achieve. That is, in the present invention, the various components of the admixture promote the reaction of the fly ash and blast furnace slag powder in each aspect, and such promotion can be harmonized to achieve further improved performance. For this reason, in the present invention, the optimum composition ratio of the necessary ions of the gypsum component and other components are presented as above.

In addition, SO ₃ , K, Na, and Si ions, as known to the present, provide an alkaline atmosphere during the cement hydration process to promote early hydration of the cement, and to some extent increase the initial reactivity of the fly ash and blast furnace slag fine powder. Appeared to be. Therefore, in the present invention, the optimum combination ratio of SO ₃ , K, Na, and Si ions was optimized, and prepared by examining solubility and reactivity in concrete. In order to obtain a composition ratio of these ions, each raw material was dissolved in a solvent, mixed, and synthesized. In addition, the mixing ratio of inorganic materials composed of gypsum source and SO ₃ , K, Na, and Si ions in a molar ratio of 5 to 20: 1 to 10: 5 to 20: 2 to 10 is determined in consideration of initial strength enhancement and other performances. Can be.

Example

In order to confirm the effect of the invention was carried out concrete experiments as follows. The concrete experiment was based on the concrete mix used by the general ready-mixed concrete company, and its composition is as follows.

In the experiment, Portland cement, blast furnace slag powder, and fly ash, which are used in the domestic ready-mixed concrete, were used as binders. The properties of the binder used in the experiment are as follows.

Using the composition of the concrete composition and the binder, the composition ratio of the binder and the admixture composition ratio of the present invention to the binder was configured as shown in the following table to make a concrete composition, then cast it to form a concrete and tested its compressive strength.

[Experimental Blend] division Binder (kg / m3) Initial Strength Enhancement Concrete Admixture (kg / m3) Coarse aggregate (kg / m3) Fine Aggregate (kg / m3) Naphthalene Water-Resistant (kg / m3) Mixed water (kg / m3) Portland cement Blast furnace slag powder Fly ash system Comparative example A-1 322 322 0          853          874          1.61          170 Example A-2 322 322 1.61 Example A-3 322 322 3.22 Comparative example B-1 257.6 64.4 322 0 Example B-2 257.6 64.4 322 1.61 Example B-3 257.6 64.4 322 3.22 Comparative example C-1 257.6 64.4 322 0 Example C-2 257.6 64.4 322 1.61 Example C-3 257.6 64.4 322 3.22 Comparative example D-1 225.4 96.6 322 0 Example D-2 225.4 96.6 322 1.61 Example D-3 225.4 96.6 322 3.22 Comparative example E-1 225.4 96.6 322 0 Example E-2 225.4 96.6 322 1.61 Example E-3 225.4 96.6 322 3.22 Comparative example F-1 193.2 96.6 32.2 322 0 Example F-2 193.2 96.6 32.2 322 1.61 Example F-3 193.2 96.6 32.2 322 3.22
[Experiment result]
division Slump (cm) Air volume (%) Compressive strength 3 days of age 7 days of age 28 days of age Mpa Strength increase rate compared to the comparative example (%) Mpa Strength increase rate compared to the comparative example (%) Mpa Strength increase rate compared to the comparative example (%) Comparative example A-1 18.0 4.5 16.5 100 24.2 100 35.6 100 Example A-2 17.5 4.6 19.3 117 27.1 112 36.2 102 Example A-3 18.0 4.3 19.8 120 27.9 115 37.1 104 Comparative example B-1 18.5 5.1 13.4 100 20.3 100 30.2 100 Example B-2 18.5 4.9 16.2 121 22.8 112 31.2 103 Example B-3 18.5 4.4 16.8 125 23.8 117 33.0 109 Comparative example C-1 19.0 3.8 11.5 100 16.8 100 28.2 100 Example C-2 18.5 4.0 13.7 119 19.3 115 29.4 104 Example C-3 18.7 3.2 13.8 120 18.8 112 29.7 105 Comparative example D-1 18.5 4.6 12.8 100 18.9 100 27.9 100 Example D-2 18.5 4.4 15.3 120 21.1 111 28.2 101 Example D-3 18.0 4.8 15.5 121 20.8 110 29.8 107 Comparative example E-1 20.0 3.3 9.8 100 15.4 100 25.4 100 Example E-2 19.5 3.1 12.3 126 17.2 112 26.1 103 Example E-3 19.0 3.4 11.9 121 17.4 113 26.4 104 Comparative example F-1 19.0 4.4 10.0 100 15.6 100 28.3 100 Example F-2 19.0 4.8 12.6 126 17.3 111 29.9 106 Example F-3 18.5 4.6 12.8 128 19.0 122 28.7 101

Here, the composition of the binder is divided into A to F and displayed, and the results of using the concrete admixture for increasing the initial strength of 0.5% type and 1.0% type for each binder composition are shown as examples. In addition, the composition of 0.5% and 1.0% type of concrete admixture for initial strength enhancement was constructed as follows.

In the present embodiments, as a result of the experiment by the Korean Industrial Standard (KS F 4009 ready mixed concrete) divided by the composition ratio of the binder from A to F series, using 0.5% type and 1.0% type of concrete admixture for initial strength enhancement The examples are 17-28% for compressive strength of 3 days, 11-22% for compressive strength of 7 days, and 28 days of compressive strength, compared to the comparative example without the use of the initial strength-enhanced concrete admixture. There was a 1–9% increase in strength. On the other hand, despite the increase in the compressive strength, as shown in the results of Table 3, almost no change in the slump and the amount of air.

In addition, the results of Table 3 shows that the concrete admixture according to the present embodiment sufficiently improves the initial strength of the concrete produced therefrom even though 40% by weight of the industrial by-products such as fly ash and blast furnace slag powder are used in the binder. From the results, even if the ratio of the fly ash and blast furnace slag binder in the concrete composition of the present invention is at least 50% by weight, it can be appreciated that the object of the present invention can be sufficiently achieved, even in some cases even higher ratio The object of the present invention may be achieved.

Therefore, the concrete admixture of the present invention can improve the initial strength without reducing the fluidity of the concrete composition, and as a result, it is possible to utilize the industrial by-product fly ash and blast furnace slag powder as a binder for concrete. Therefore, in addition to improving the initial strength of concrete, the present invention also provides the advantages of resource recycling, as well as the shortening of construction period and cost reduction.

Claims (5)

Gypsum source 25 ~ 85% by weight and SO ₃ , K, Na, and Si ions in a molar ratio of 5 to 20: 1 to 10: 5 to 20: characterized in that it comprises 15 to 75% by weight of inorganic material consisting of 2 to 10 Strength-enhanced concrete admixture The method of claim 1, The gypsum source is an initial strength-enhanced concrete admixture, characterized in that composed of anhydrous gypsum 30 ~ 98%, hemihydrate gypsum 1 ~ 35%, and dihydrate gypsum 1 ~ 35%. Concrete admixture containing 25-85% by weight of gypsum source and 15-75% by weight of inorganic material composed of SO ₃ , K, Na, and Si ions in a molar ratio of 5-20: 1-10: 5-20: 2-10 Concrete composition for initial strength enhancement, characterized in that it comprises 0.2 to 5% compared to the binder based on the weight. The method of claim 3, The binder of concrete further comprises at least one of fly ash and blast furnace slag fine powder in addition to cement. The method of claim 3, The binder of the concrete is an initial strength-enhancing concrete composition, characterized in that it comprises at least one industrial by-product selected from the group consisting of fly ash and blast furnace slag fine powder in addition to cement based on the total binder weight.