KR102210337B1 - High strength lightweight mortar composition comprising pre-wetted artificial lightweight fine aggregate with recycled water of ready mixed concrete - Google Patents

Abstract

The present invention relates to a high-strength lightweight mortar composition comprising an artificial lightweight fine aggregate subjected to pre-wetting treatment with ready-mixed concrete recovered water.
The present invention is blended with “mixed water 140-180kg/㎥, cement 320-450kg/㎥, artificial lightweight fine aggregate 500-700kg/㎥, and water cement ratio 35-45wt%, but the artificial lightweight fine aggregate is mixed and calcined with coal ash and dredged soil. It has a particle diameter of less than 5 mm, a combined content of SiO ₂ and Al ₂ O ₃ exceeds 80 wt%, a density of less than 1.8 g/cm 3, and pre-wetting in ready-mixed concrete recovery water for 22 to 26 hours. It provides a high-strength lightweight mortar composition", characterized in that it is mixed and adjusted to a standard dry state.

Description

High strength lightweight mortar composition comprising pre-wetted artificial lightweight fine aggregate with recycled water of ready mixed concrete}

The present invention relates to a high-strength lightweight mortar composition comprising an artificial lightweight fine aggregate subjected to pre-wetting treatment with ready-mixed concrete recovered water.

Recently, problems related to the reduction of concrete self-weight have emerged at home and abroad due to the demand for large, long, and seismic design of buildings. Accordingly, the need for lightweight concrete for reducing its own weight is increasing, and artificial lightweight aggregates can be used instead of ordinary aggregates to reduce the unit volume mass of concrete.

Artificial lightweight aggregate is a material that stands out in terms of eco-friendliness because it is made by processing clay and industrial by-products. Artificial lightweight aggregates include aggregates that are artificially fired using expansible shale, expansive clay, and fly ash as main raw materials, and lightweight aggregates and processed products thereof, which are industrial by-products such as expanded slag and coal waste. The interior of the artificial lightweight aggregate is porous and the surface is covered with a glassy film. Since the interior is a porous structure, it is difficult to apply it due to problems such as blockage of pumping concrete and lack of time-lapse security during concrete construction due to the high absorption rate of the aggregate itself.

The inventors of the present invention confirmed the applicability to lightweight concrete that exhibits high strength by controlling the high absorption rate of artificial lightweight aggregates through pre-wetting and adjusting the blending ratio of artificial lightweight aggregates. By developing the patented patent 10-1948627, "a high-strength lightweight concrete composition containing an artificial lightweight aggregate" has been derived.

Meanwhile, the importance of environmental issues has recently emerged in society, and regulations to prevent environmental pollution have been strengthened both domestically and internationally. For this reason, research and development is underway to increase the use of by-products in the construction industry.

Ready-mixed concrete recovered water is an alkaline liquid by-product generated in the process of cleaning various equipment after concrete production. If such ready-mixed concrete recovered water is discharged as it is, it causes water quality and soil pollution, so a neutralization process is essential before discharging, and research and development are being conducted to induce the proper treatment of such ready-mixed concrete recovered water.

1. Registered Patent 10-0568932 "Lightweight concrete and its manufacturing method" 2. Registered Patent 10-1948627 "High-strength lightweight concrete composition containing artificial lightweight aggregate"

An object of the present invention is to improve the compressive strength of a lightweight mortar composition without fluidity problems,

Another purpose is to recycle the ready-mixed concrete recovered water, which is a by-product of the construction industry that requires management for disposal, to be recycled as immersion water for prewetting of artificial lightweight aggregates and mixed water of high-strength lightweight mortar composition.

In order to solve the above-described problems, the present invention is blended with ``mixing water 140-180kg/㎥, cement 320-450kg/㎥, artificial lightweight fine aggregate 500-700kg/㎥, water cement ratio 35-45wt%, but the artificial lightweight fine aggregate is coal ash It is manufactured by mixing and firing dredged soil with a particle diameter of less than 5 mm, a combined content of SiO ₂ and Al ₂ O ₃ exceeding 80wt%, a density of less than 1.8g/cm3, and prewetting for 22 to 26 hours in ready-mixed concrete recovery water ( After pre-wetting), it provides a high-strength lightweight mortar composition, characterized in that it is mixed and adjusted to a standard dry state.

The number of ready-mixed concrete used in the prewetting may be obtained by applying a solid content of 7.5 to 10.0 wt% so that a compressive strength of 45 MPa or more can be expressed at 28 days of age.

In addition, the ready-mixed concrete recovered water can also be applied as a blending water, and by applying the ready-mixed ready-mixed water of 7.5 to 10.0 wt% solid content applied as the immersion water for the prewetting as the blended water, compressive strength of 50 MPa or more is expressed for 28 days. You can do it.

According to the present invention, the following effects can be expected.

1. By using the ready-mixed concrete recovered water as immersion water for prewetting of artificial lightweight fine aggregates, the compressive strength of the lightweight mortar composition for 28 days can be expressed over 45 MPa.

2. By applying the recovered ready-mixed water as the mixing water, the compressive strength of the lightweight mortar composition for 28 days can be expressed over 50 MPa.

3. The recovered ready-mixed concrete can be used as a resource for obtaining a high-strength lightweight mortar composition, which has been discarded after neutralization without special use.

The present invention is blended with “mixed water 140-180kg/㎥, cement 320-450kg/㎥, artificial lightweight fine aggregate 500-700kg/㎥, and water cement ratio 35-45wt%, but the artificial lightweight fine aggregate is mixed and calcined with coal ash and dredged soil. It has a particle diameter of 5 mm or less, a combined content of SiO ₂ and Al ₂ O ₃ exceeding 80wt%, a density of less than 1.8g/cm3, and pre-wetting in ready-mixed concrete recovery water for 22 to 26 hours. It provides a high-strength lightweight mortar composition", characterized in that it is mixed and adjusted to a standard dry state.

1. Raw materials

The present invention is to derive a high-strength lightweight mortar composition using artificial lightweight fine aggregate and ready-mixed concrete recovered water. Details of the artificial lightweight fine aggregate and ready-mixed concrete recovered water are as follows. Class 1 common Portland cement was applied as the binder.

(1) Artificial lightweight fine aggregate

According to the standard specification for concrete, lightweight aggregates should be made and fired at a factory using expandable shale, expandable clay, fly ash, etc. as main raw materials, and must be clean, strong, durable, and have an appropriate particle size and unit mass, and are bad for concrete and steel. It should not contain harmful substances that affect it, and should have small variations in quality.” These lightweight aggregates are mainly classified into natural lightweight aggregates such as volcanic rock, pumice and tuff, and artificial lightweight aggregates fired and expanded using blast furnace slag, clay, diatomaceous earth, slate, and coal ash as raw materials. In addition, artificial lightweight aggregates are not only lighter in weight than general aggregates due to their porous properties, but also have excellent moisture-proof, sound-absorbing, sound-absorbing, and heat-insulating effects. Accordingly, domestic and foreign studies on the performance improvement and optimal mixing design for artificial lightweight aggregates are in progress. [Reference Figure 1] below shows the pore structure of an artificial lightweight aggregate.

[Reference Figure 1]

The artificial lightweight fine aggregate applied to the present invention is selected from an artificial lightweight aggregate with a particle diameter of 5 mm or less among artificial lightweight aggregates produced by mixing and firing coal ash and dredged soil, and the sum of SiO ₂ and Al ₂ O ₃ exceeds 80 wt%. , The density is less than 1.8 g/cm 3.

In general, when the aggregate contains a large amount of SiO ₂ and Al ₂ O ₃ components, an alkali aggregate reaction is a problem. Alkali aggregate reaction is a phenomenon in which alkali components (Na ₂ O, K ₂ O) in cement and reactive silica contained in aggregate react in the presence of water to produce alkali silicate gel, causing swelling. It is a reaction that must be suppressed by common sense of phosphorus technology.

However, in the present invention, coal ash and dredged soil are mixed and calcined to produce an artificial lightweight fine aggregate having a lower density than ordinary sand, and the alkali silicate gel produced even if the above-described alkali aggregate reaction occurs is mainly used in the pores of the artificial lightweight aggregate ( Since the alkali aggregate reaction occurs in the pores of the artificial lightweight aggregate itself or the pores of the adjacent artificial lightweight aggregate), volume expansion of the aggregate does not occur, but rather internalization is achieved.

[Table 1] below is a result of analyzing the components by collecting some of the artificial lightweight fine aggregate applied to the present invention, and [Table 2] shows the physical properties of the artificial lightweight fine aggregate compared with ordinary sand.

ingredient Content (wt%) SiO ₂ 65.70 Al ₂ O ₃ 16.90 Fe ₂ O ₃ 6.64 CaO 2.62 MgO 1.44 K ₂ O 2.14

division Assembly rate (FM) Density (g/cm ³ ) Water absorption (%) Plain sand 2.89 2.6 1.00 Artificial lightweight fine aggregate
(Particle diameter less than 5mm) 4.61 1.77 8.71

(2) Ready-mixed concrete recovery water

Ready-mixed concrete recovery water refers to the water remaining on the top after sedimenting aggregate from the washing water of ready-mixed concrete transport vehicles and mixers.

In the present invention, a ready-mixed concrete recovery water of the following [Reference Photo 1] is used. However, since the concentration (concentration of the solids contained) and components of the ready-mixed concrete discharged depending on the factory vary, in the present invention, the solid content (based on the washing water discharged from a ready-mixed concrete transport vehicle, mixer, etc., in which Class 1 common Portland cement is applied as a binder) Examples were mainly classified according to the content of cement powder).

In the present invention, the collected ready-mixed concrete recovered water was dried and pulverized and then mixed with water according to the required concentration, and the related experiment was conducted by adjusting the solid content for each example, and the specific gravity of water and cement and weight per unit volume data The solid content may be adjusted by calculating the solid content based on and adding water according to the required concentration.

2. Experiment method

In the present invention, a high-strength lightweight mortar composition is derived using the artificial lightweight fine aggregate and the ready-mixed concrete recovered water, and the ready-mixed concrete recovered water is used only for prewetting of the artificial lightweight fine aggregate (Series I) and the ready-mixed concrete recovered. Examples of using the artificial lightweight fine aggregate for prewetting and mixing water (Series II) were classified to test mortar flow and compressive strength by age.

(1) Mortar formulation

[Table 3] below is a blending table of lightweight mortar applied to the above experiment.

Series Sludge concentration(wt%) W/C
(%) Unit weight(kg/cm3) pre-wetting water compound water W C LS Sludge

Ⅰ 1-1 0.0 -

42

144

320

519 - 1-2 2.5 - - 1-3 5.0 - - 1-4 7.5 - - 1-5 10.0 - -

Ⅱ 2-1 0.0

42

144

320

519 0.0 2-2 2.5 3.6 2-3 5.0 7.2 2-4 7.5 10.8 2-5 10.0 14.4

(2) Prewetting

Since the artificial lightweight fine aggregate (LS) absorbs water more easily than ordinary sand, if it is used in a dry state, the quality of the artificial lightweight fine aggregate (LS) tends to fluctuate during rubbing, transportation, and pouring of concrete, so it must be used in a state that sufficiently absorbs water.

However, if the immersion time (prewetting time) is excessively long, the mortar flow and compressive strength tend to decrease, so the prewetting period is preferably limited to 22 to 26 hours. All of the test examples of the present invention were subjected to the experiment by prewetting the artificial lightweight fine aggregate for 24 hours, and then adjusting it to a standard condition in accordance with KS F 2529 "Density and Absorption Test Method of Structural Lightweight Fine Aggregate".

In Series I, the solid content (sludge) content of the ready-mixed concrete recovered water was applied as pre-wetting water according to the concentration of 0.0, 2.5, 5.0, 7.5, 10.0wt%, and in Series II, each of the above immersion water was mixed Was applied.

(3) Test body production and curing

The mortar test specimen was prepared in a 50×50×50 mm cubic mold, poured the mortar composition for each experimental example, demolded after 24 hours, and cured at a high temperature of 40° C. until the required age.

3. Experiment result

As for the measurement items of the experiment conducted by the above method, the mortar flow and the compressive strength on the 7th, 14th and 28th days of age were measured according to KS L 5105 "Test Method for Compressive Strength of Hydraulic Cement Mortar". The experimental results are as follows.

(1) Mortar flow

[Graph 1] below shows the mortar flow of each experimental example of Experiment Series I, and shows a flow value of 180 to 215 mm in all experimental examples. There was not a certain tendency to change the mortar flow according to the solid content of the ready-mixed concrete recovered water. Since the mixed water of Series Ⅰ is general water, the effect of applying ready-mixed concrete recovered water as immersion water seems to be insignificant. The highest flow value was shown in Experimental Examples 1-4 in which the solid content of the ready-mixed concrete recovered water was 7.5 wt%.

[Graph 1]

[Graph 2] below shows the mortar flow of each experimental example in Experiment Series II, and shows a flow value of 155 to 205 mm in all experimental examples. The mortar flow tended to decrease as the solid content of the ready-mixed concrete recovered water increased. It is believed that the solid content contained in the blended water affects the mortar flow. However, even if the solid content of the ready-mixed concrete recovered water increased from 7.5wt% to 10.0wt%, the mortar flow did not decrease, and it can be seen that the fluidity within an appropriate range was expressed up to the solid content of 10.0wt% of the recovered ready-mixed water. have.

[Graph 2]

(2) compressive strength

[Graph 3] below shows the compressive strength by age of each experimental example of Experiment Series Ⅰ. The compressive strength of 7 days of age was similar to that of 36 to 38 MPa in all experimental examples, and similar compressive strength of 37 to 39 MPa was expressed in all experimental examples of 14 days of age. The compressive strength of 28 days of age showed a compressive strength of 46 MPa in Experimental Examples 1-4 and 1-5, which was about 5% higher than that of Experimental Example 1-1, which did not use ready-mixed concrete recovery water as immersion water. Was

As a result, when the ready-mixed concrete recovered water with a solid content (cement sludge) content of 7.5 to 10.0 wt% is applied as immersion water, the initial strength is expressed at the same level as when the ready-mixed concrete recovered water is not used, and the long-term strength is somewhat higher. It can be seen as being done.

[Graph 3]

[Graph 4] below shows the compressive strength for each age of Experiment Series Ⅱ. In the case of 7 days of age, similar compressive strength of about 33 MPa was expressed in Experimental Examples 2-1, 2-2 and 2-3, and about 20% higher than that of Experimental Example 2-1 in Experimental Examples 2-4 and 2-5. The compressive strength was expressed. In the case of 14 days of age, similar compressive strengths of 39 to 41 MPa were expressed in Experimental Examples 2-1, 2-2 and 2-3, and the highest compressive strength was expressed at about 45 MPa in Experimental Example 2-4. Experimental Example 2-5 was also expressed higher than Experimental Example 2-1 with a compressive strength of 45MPa. In the case of 28 days of age, high compressive strength of about 51 MPa was expressed in Experimental Examples 2-4 and 2-5, which was approximately 14% higher than that of Experimental Example 2-1.

[Graph 4]

As a result, when the ready-mixed concrete recovered water with a solid content (cement sludge) content of 7.5 to 10.0 wt% used as the immersion water is applied as the blended water, the compressive strength for each age is improved as the solid content is filled in the fine pores in the mortar matrix. Although it is confirmed that there is a possibility that the solid content itself, which is a cement sludge, can exhibit the hardening performance, further research on this is required.

In addition, if the solid content of the ready-mixed concrete recovered water exceeds 10.0 wt%, there is a possibility that the compressive strength for each age may be slightly improved, but the loss of fluidity increases, and the solid content of the ready-mixed concrete recovered water is used as less than 3wt% of the cement applied as a binder. It is preferable that the solid content of the ready-mixed concrete recovered water is limited to 10.0 wt% or less.

The present invention has been described in connection with the embodiments as mentioned above, but various modifications and variations can be made without departing from the gist of the present invention, and can be used in various fields. Accordingly, the claims of the present invention include modifications and variations that fall within the true scope of the previous invention.

Claims (4)

Mixing water is 140~180kg/㎥, cement 320~450kg/㎥, artificial lightweight fine aggregate 500~700kg/㎥, water cement ratio 35~45wt%.
The artificial lightweight fine aggregate is manufactured by mixing and sintering coal ash and dredged soil, and has a particle diameter of 5 mm or less, a combined content of SiO ₂ and Al ₂ O ₃ exceeds 80 wt%, a density of less than 1.8 g/cm 3, and is 22 to After pre-wetting for 26 hours, the mixture was adjusted to a standard dry condition and mixed.
The ready-mixed concrete recovered water used as immersion water for the prewetting is 7.5 to 10.0 wt% of solid content,
By applying the ready-mixed concrete recovered water used as the immersion water as the mixing water,
A mortar composition, characterized in that the compressive strength of 50 MPa or more is expressed on 28 days of age. delete delete delete