KR20040078466A - concrete producing to use cement kiln dust - Google Patents

Abstract

PURPOSE: Provided is a concrete having improved fluidity, separation resistance, solidification and initial strength by using cement kiln dust(CKD) generated from sintering of cement clinker. CONSTITUTION: The concrete is produced by mixing cement, aggregate and 5-40wt.% of cement kiln dust for cement or fine aggregate for 10-180sec, wherein the cement kiln dust is mainly fine lime stone powder, byproduct generated in clinker sintering of the cement production and the limestone powder has a size of 4-10micrometer.

Description

Concrete producing to use cement kiln dust

The present invention relates to concrete produced using cement kiln dust (CKD) generated during cement manufacturing process, and in particular, a certain ratio of CKD generated during clinker firing during cement manufacturing process with respect to fine aggregates or cement. By replacing concrete with concrete, it improves the fluidity, filling and material separation resistance of concrete, shortens the time of form removal by promoting condensation and initial strength, and reduces the cost of formwork by lowering the side pressure, and prevents initial freezing during cold construction. And it relates to concrete produced by using a cement kiln dust that can obtain additional effects such as temperature cracking suppression of mass concrete according to the reduction of hydration heat.

Recently, as global environmental pollution measures and resource shortages become more serious, various ways to efficiently recycle industrial wastes and by-products are being considered. In the construction industry, as the construction efficiency is reduced due to the reduction of construction laborers and the development of construction industry technology, the necessity of high-flow concrete that does not require compaction in concrete construction is increasing. The use of copper and mass concrete is increasing.

However, high flow concrete has high fluidity and easy separation of materials. Therefore, conventionally, high flow concrete, such as fly ash and blast furnace slag powder, is manufactured in the form of a high flow concrete such as methyl cellulose (MC) and polysaccharide polymer. The high-flow concrete is used to solve the problem of material separation, but the condensation time is low, the initial strength is low, and it is expensive.

In addition, in the case of mass concrete, fly ash, blast furnace slag fine powder, etc. are used together with unit cement amount reduction and low heating cement in order to reduce the heat of hydration in the concrete. There is a problem of increased cost and high manufacturing cost, and in case of concrete construction in Korea and China, it has been raised as a problem to prepare more careful measures for the early East Sea due to late strength.

The present invention is to solve the above problems, by replacing a certain ratio of CKD, which is a by-product of the cement manufacturing process for fine aggregates or cement, to produce economical and high-quality concrete, fluidity, filling and material separation resistance Additional effects such as shortening the form removal time by promoting condensation and initial strength, reducing form cost by lowering the side pressure, preventing early freezing during construction in Korea, and reducing the temperature cracking of the mass concrete by reducing the heat of hydration The purpose of the present invention is to provide concrete manufactured using CKD, which can achieve economic stability by improving process stability, cement productivity and recycling of industrial by-products by partially releasing CKD in the cement manufacturing process. have.

1 is a graph showing the particle size characteristics of CKD by each cement manufacturer in Korea.

Figure 2 is a graph analyzing the mineral phase of CKD by cement manufacturers using X-ray diffraction (XRD) analyzer.

3 is a graph showing the slump flow of high flow concrete according to the change of the mixing rate of CKD.

4 is a graph showing the filling properties of high flow concrete according to the change of the mixing rate of CKD.

5 is a graph showing the material separation resistivity according to the change in the mixing rate of CKD.

6 is a graph showing the setting time according to the change of the mixing rate of CKD.

7 is a graph showing the compressive strength according to the aging of the CKD by the mixing rate.

8 is a graph showing the temperature history according to the change of the mixing rate of CKD.

In order to achieve the above object, the present invention,

CKD, which is an industrial by-product, is substituted for a predetermined ratio with respect to fine aggregates or cement, and then mixed for a predetermined time to provide concrete. Preferably, the substitution rate of CKD in the production of concrete is 5 to 40% based on the fine aggregate or cement.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

CKD is a by-product generated during cement manufacturing process. Particle dust collected during the clinker firing process is collected by an electrostatic precipitator or filter bag, and its main component is limestone fine powder. The collected CKD is re-introduced into raw materials and consists of a system that continuously circulates a certain amount, but it acts as a factor of uneven mixing due to particle size and component separation and fluctuation of raw materials according to process conditions, which may cause process instability and lower production efficiency. It was.

Figure 1 of the accompanying drawings is a graph showing the particle size characteristics of each cement manufacturer CKD. Referring to FIG. 1, the particle size of CKD ranges from about 4 to 10 μm, indicating a relatively fine particle size, and the particle size distribution is slightly different according to cement manufacturers, but the particle size of CKD is smaller than that of cement particles. . These results are shown in detail in Table 1 below.

division SPAN ¹⁾ Particle diameter when the volume is 10% (㎛) Particle Size (μm) at Volume 90% Medium particle size (㎛) K company 2.341 1.08 13.24 5.15 Company D 3.591 1.46 37.24 9.96 L company 3.163 1.26 23.52 7.04 S company 2.721 1.08 14.35 4.88 SS company 3.127 0.97 13.41 3.98 A company 2.242 1.14 13.91 5.69 H company 3.325 1.29 23.38 6.59

<Table 1> Particle Size of CKD by Cement Manufacturer

Note 1) (Particle size at Volume 90%-Particle size at Volume 10%) x Medium particle size

Table 2 below shows the chemical composition of CKD per cement manufacturer. Overall cement chemical composition of the manufacturer-specific CKD was shown to be similar, the induction was gyeothap plasma (ICP) a content of CaO of the constituent elements of the CKD born lot represented by at least about 40% by spectroscopy, Si0 ₂ is cement production There is a big difference in the range of 0.99 ~ ll.46% by plant. In addition, SO ₃ , K ₂ O and Na ₂ O appeared slightly different for each cement manufacturer, which may be due to differences in raw material conditions and process characteristics of cement manufacturers.

<Table 2> Chemical Composition of CKD by Cement Manufacturer

division Ig-loss Si0 ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO SO ₃ K ₂ O Na ₂ O K company 36.11 1.25 1.45 2.07 43.59 2.63 0.95 2.22 0.41 Company D 37.20 1.52 1.06 1.72 44.71 2.23 0.31 0.40 0.42 L company 35.71 7.06 0.89 1.71 45.39 1.71 0.27 0.24 0.28 S company 38.04 3.05 1.36 2.04 39.25 1.62 0.17 0.51 0.38 SS company 37.20 1.63 0.93 1.40 48.26 1.34 0.24 0.33 0.37 A company 36.13 11.46 4.34 1.62 43.02 1.58 0.77 1.14 0.09 H company 38.24 1.28 1.17 2.96 44.92 1.57 0.24 0.43 0.27

Of the accompanying drawings, Figure 2 is X-ray diffraction (XRD) was as one using the analyzer analyzes the gwangmulsang of cement by manufacturer CKD generally are born too appear to be the CaCO ₃ main component in the similar tendency, additives with the SiO ₂ ingredient It was found to contain.

Figure 3 of the accompanying drawings shows the slump flow of the high-flow concrete according to the change in the mixing rate of CKD. Overall, W / C 35% tended to decrease in slump flow due to the increase in viscosity.In 45%, the material separation decreased with viscosity and the mixing rate increased by 10%. The flow rate tends to increase. In addition, the W / C 55% tended to be similar to the 45% case, and the larger the W / C, the lower the material separation at a constant mixing ratio of the limestone fine powder, and the better viscosity and fluidity were exhibited.

Figure 4 shows the filling properties of high flow concrete according to the change of the mixing rate of CKD. In general, the filling height was lower when the limestone fine powder was not mixed and the lower the mixing ratio was, but the filling performance was improved as the occlusion phenomenon was reduced due to the improvement of dispersion retention of the coarse aggregate until the mixing ratio of CKD.

Figure 5 shows the material separation resistivity according to the change of the CKD mixing rate, the material separation resistivity was within 85 ~ 105% in each W / C, and shows a good material separation resistivity as the mixing rate of CKD increases.

Figure 6 is a graph showing the setting time according to the change of the mixing rate of CKD. In general, the more the compounding ratio was added, the faster the setting time. In particular, as the mixing rate of CKD increased, the setting time was significantly shortened. The reduction is expected to have a significant effect on air shortening.

Attached figure 7 shows the compressive strength according to the aging of CKD by the mixing rate. Overall, as the mixing rate of CKD increases, the compressive strength increases with the initial age, such as 1 day. In addition, 7-day compressive strength was expressed as 73 ~ 93% for W / C 35% and W / C 45% for H / C based on 28-day compressive strength. About 79 ~ 93% of cases, about 70 ~ 79% of company A and about 55 ~ 91% of W / C 55% showed overall increase in CKD incorporation rate at early age than in non-incorporation. It was found to be particularly high.

Figure 8 shows the temperature history according to the change of the mixing rate of CKD. In general, the temperature tends to decrease after the concrete is poured, and then gradually decreases around 1 day after the concrete is placed. As the mixing rate of CKD increases, the maximum temperature decreases. In about 10 ℃ was confirmed to be lowered.

As described above, the production method of concrete using CKD according to the present invention is excellent in fluidity, filling properties and resistance to material separation, shorten the form removal time due to condensation acceleration and initial strength increase, side pressure drop, initial stage during the construction of Korea-China. It is effective in preventing temperature cracks by preventing frost and reducing heat of hydration of mass concrete. In addition, by removing CKD partially in the cement manufacturing process, economic stability is expected due to process stability, improved cement productivity, and recycling of industrial by-products.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims You will understand.

Claims (2)

A method for producing concrete using cement kiln dust, characterized in that CKD is substituted by a predetermined ratio with respect to fine aggregates or cement and mixed for 10 seconds to 3 minutes. The method of claim 1, wherein the substitution rate of the CKD is substituted in the range of 5 to 40% of the weight of the fine aggregate or cement.