KR102550407B1 - Eco-friendly mortar composition with blast furnace slag fine aggregate and ready-mixed concrete recovered water - Google Patents

Abstract

The present invention relates to an eco-friendly mortar composition that increases the recycling rate of recovered water, which is a by-product of the ready-mixed concrete industry, removes metal from ore in the steelmaking process, and applies blast furnace slag fine aggregate generated as an industrial by-product and recovered ready-mixed concrete generated during the manufacturing process of ready-mixed concrete. .
More specifically, it is a method for promoting its fluidity, strength and durability by increasing the mixing ratio of blast furnace slag fine aggregate in mortar using general Portland cement and natural mountain sand fine aggregate.
The present invention is "330 to 360 parts by weight of cement; 80 to 320 parts by weight of fine aggregate; and 160 to 180 parts by weight of mixing water; The fine aggregate is composed of 60 to 90 vol% of natural fine aggregate and 10 to 40 vol% of blast furnace slag fine aggregate, and the mixing water contains 5.0 to 10.0 wt% of solids obtained from the recovery of ready-mixed concrete, so that the solids are sent to the blast furnace Provided is an eco-friendly mortar composition to which blast furnace slag fine aggregate and ready-mixed concrete recovery water are applied, characterized in that the reactivity of the slag fine aggregate is promoted.

Description

Eco-friendly mortar composition with blast furnace slag fine aggregate and ready-mixed concrete recovered water}

The present invention relates to a mortar composition in which fluidity, compressive strength, tensile strength, drying shrinkage, and neutralization inhibition performance are improved by using blast furnace slag fine aggregate and recovered ready-mixed concrete as raw materials for the mortar composition,

More specifically, it relates to a technique in which the solids obtained from the recovery of ready-mixed concrete activate the reactivity of the blast furnace slag fine aggregate to improve the hardening performance and durability of the mortar.

Recently, the importance of environmental problems has been greatly emphasized, and regulations for preventing environmental pollution are being strengthened. In the construction industry, efforts to prevent environmental pollution and research for recycling by-products of the construction industry are being actively conducted.

On the other hand, in the production of ready-mixed concrete, the recovery of ready-mixed concrete generated in the form of equipment washing, concrete mixing, and surplus water remaining is a process by-product that inevitably occurs when manufacturing ready-mixed concrete for large-scale equipment. Despite being applied in the form of an additive to the product, the amount generated is not decreasing because the amount used is very small.

In addition, in order to avoid the burden of treatment costs, some business sites are discharging ready-mixed concrete recovery water into rivers or landfilling it without permission, so eco-friendly recycling management techniques for recovered water, sludge, symbol water, and sludge are required in the field.

On the other hand, natural fine aggregate used in construction sites is a basic material for the construction industry, and stable supply is essential, but difficulties in supply and demand on site are increasing.

The amount of natural fine aggregate is continuously decreasing, and difficulties in collecting aggregate are increasing due to indiscriminate development of stone mines, environmental regulations due to sea sand collection, and opposition from residents.

The shortage of natural fine aggregate leads to a price increase in the construction materials market, which is the reason for the high price of 40,000 won per cubic meter.

In addition, within the next three years, the price of aggregate is expected to rise to 45,000 won per cubic meter, and it is urgent to secure alternative fine aggregate as a countermeasure.

Blast furnace slag fine aggregate is being researched and developed as a substitute for natural fine aggregate, which is difficult to supply as described above. Blast furnace slag fine aggregate is the main raw material of industrial by-products generated from steel mills, and more than 70% of slag is a water material rapidly cooled by rapidly spraying molten slag generated in a blast furnace with water. It is mainly used as a raw material in the manufacture of blast furnace slag fine powder.

[Reference Figure 1]

1. Patent Publication No. 10-2020-0125141, "High-strength lightweight mortar composition containing artificial lightweight fine aggregate pre-wetted with ready-mixed concrete recovery water" 2. Registered Patent No. 10-1948627 "High-strength lightweight concrete composition containing artificial lightweight aggregate" 3. Registered Patent No. 10-1723204 "Remicon Recovery Sludge Powder, Manufacturing Method and Ascon Composition for Surface Layer" 4. Registered Patent No. 10-1470307 "Method of manufacturing non-toxic concrete using chemical admixture for concrete and ready-mixed concrete recovery" 5. Registered Patent No. 10-1554864 "Concrete manufacturing method using sludge settlement accelerator of ready-mixed concrete recovery and concrete manufactured by this method"

1. Tae-gyu Oh, Dong-ju Lee, Seong-ho Bae, Se-jin Choi, "Fluidity and Compressive Strength Characteristics of Lightweight Mortar with Recovered Water Based on Blast Furnace Slag Fine Powder Mixing Ratio", Proceedings of the 2019 Fall Conference of the Korean Concrete Institute, Vol. 31, No. 2 (Volume 61) ), p.529-530, 2019.10. 2. Kyungsoo Lee, Taegyu Oh, Soobin Jeong, Jeonghyeon Kim, Younguk Kim, Sejin Choi, "Pre-wetting of artificial lightweight aggregate using recovered water and strength characteristics of lightweight mortar", Proceedings of the 2019 Spring Conference of the Korean Cret Society, Vol. 31, No. 1 (vol. 1) 60), p.407-408, 2019.05.

The present invention is to increase the recycling rate of the ready-mixed concrete recovery and to increase the use of the aggregate supply and demand problems and industrial by-products. Its purpose is to provide a mortar composition exhibiting excellent suppression performance and the like.

In order to solve the above problems, the present invention is "cement 330 ~ 360 parts by weight; 80 to 320 parts by weight of fine aggregate; and 160 to 180 parts by weight of blending water; The fine aggregate is composed of 60 to 90 vol% of natural fine aggregate and 10 to 40 vol% of blast furnace slag fine aggregate, and the mixing water contains 5.0 to 10.0 wt% of solids obtained from the recovery of ready-mixed concrete, so that the solids are sent to the blast furnace Provided is an eco-friendly mortar composition to which blast furnace slag fine aggregate and ready-mixed concrete recovery water are applied, characterized in that the reactivity of the slag fine aggregate is promoted.

The blast furnace slag fine aggregate has a particle diameter of 5 mm or less, It can be applied with a granularity of 2.3 to 3.1 and a specific gravity of 2.5 to 2.8 g/cm3, and by forming the fine aggregate with 70 to 90 vol% of natural fine aggregate and 10 to 30 vol% of blast furnace slag fine aggregate, the drying shrinkage rate compared to the blend using only natural fine aggregate is 6 ~10% reduction can be achieved.

In addition, by forming the fine aggregate with 60 vol% of natural fine aggregate and 40 vol% of blast furnace slag fine aggregate, the accelerated neutralization depth can be reduced by 10% or more compared to the mixture using only natural fine aggregate.

As the solid material, one containing 35 wt% or more of CaO may be applied.

Effects that can be obtained through the present invention are as follows.

1. By replacing some of the natural fine aggregate (stone mountain aggregate, sea sand, etc.) applied to the mortar composition with the blast furnace slag fine aggregate and using the mixing water mixed with the recovered ready-mixed concrete solids, physical properties equivalent or better than that of mortar using only natural fine aggregate ( fluidity, compressive strength, tensile strength, drying shrinkage, etc.) are expressed.

2. The compressive strength and tensile strength of the mortar composition are improved by the amorphous crystal structure and latent hydraulic properties of the blast furnace slag fine aggregate.

3. When 5.0 to 10.0 wt% of the recovered ready-mixed concrete is included in the mixing water applied to the mortar composition and 10 to 40 vol% of the blast furnace slag fine aggregate is included in the fine aggregate, physical properties such as fluidity, initial strength and long-term strength are generally It improves.

4. When 10 to 30 vol% of blast furnace slag fine aggregate is included in the fine aggregate applied to the mortar composition, the drying shrinkage rate is reduced by 6 to 10% compared to the blend using only natural fine aggregate.

5. When 40 vol% of blast furnace slag fine aggregate is included among the fine aggregates applied to the mortar composition, the accelerated neutralization depth is reduced by more than 10% compared to the mixture using only natural fine aggregate.

[Figure 1] shows the results of XRD component analysis of the recovered ready-mixed concrete solids.
[Figure 2] is a schematic diagram of the densification of the blast furnace slag fine aggregate by the solids recovered from ready-mixed concrete and the reaction mechanism of the surface.
[Figure 3] shows the change in the flow of mortar using the solids content in the mixing water and the blast furnace slag fine aggregate.
[Figure 4] shows the change in compressive strength of mortar at 7 days, 28 days and 56 days according to fixing the same amount of mixing water containing 5 wt% of solids and increasing the replacement rate of blast furnace slag fine aggregate.
[Figure 5] shows the change in tensile strength of mortar at 28 days of age according to fixing the same amount of mixing water containing 5 wt% of solids and increasing the replacement rate of blast furnace slag fine aggregate.
[Figure 6] shows the amount of change in the drying shrinkage length of the mortar after 56 days of age according to fixing the same amount of mixing water containing 5 wt% of solids and increasing the replacement rate of blast furnace slag fine aggregate.
[Figure 7] shows the result of measuring the penetration depth of accelerated neutralization at the age of 28 days of mortar according to fixing the same amount of mixing water containing 5 wt% of solids and increasing the replacement rate of blast furnace slag fine aggregate.

The present invention is "330 to 360 parts by weight of cement; 80 to 320 parts by weight of fine aggregate; and 160 to 180 parts by weight of mixing water; The fine aggregate is composed of 60 to 90 vol% of natural fine aggregate and 10 to 40 vol% of blast furnace slag fine aggregate, and the mixing water contains 5.0 to 10.0 wt% of solids (hereinafter referred to as 'solids') obtained from the recovery of ready-mixed concrete. , It provides an eco-friendly mortar composition to which blast furnace slag fine aggregate and ready-mixed concrete recovery water are applied, characterized in that the solids promote the reactivity of the blast furnace slag fine aggregate.

The ready-mixed concrete recovery water is water generated by washing in the recovery process, and is a general term for the sludge number ^** obtained by purifying the washing waste water ^* and the symbolic number ^*** (KS F 4009).

^* Washing drainage: Water used to wash away concrete and spilled concrete attached to trucks, plant mixers, hoppers, etc.
^** Sludge index: Suspended water remaining after separating and recovering coarse aggregate and fine aggregate in concrete washing drainage
^*** Symbol water: Water obtained by removing sludge solids from sludge water by sedimentation or other methods

Sludge ^* exists among the ready-mixed concrete recovery water, excluding symbol water, Solid content ^** can be extracted from the sludge.

^* Sludge: A state in which fluidity is lost due to concentration of sludge water
^** Sludge solid content: obtained by drying sludge at 105 ~ 110 ℃

In the present invention, when the sludge of the ready-mixed concrete recovery water is diluted in the blending water, the solid component contained in the blending water is referred to as "solids". The components of the "solids" and "solids" are the same, but the "solids" includes the concept of "powder collected through a drying process", whereas the "solids" defined in the present invention is related to the collection process and properties. It is a concept centered on ingredients that do not exist.

That is, in the present invention, when the sludge is extracted from the remicon recovery water and the sludge is diluted in the mixing water as it is, the solid components contained in the mixing water can be collectively referred to as "solids", and as above, In the case of preparing the blending water in this way, a separate energy requirement such as the solid content drying process is not required.

The solid material contains components such as CaO, Al ₂ O ₃ , and MgO, and accordingly, Ca(OH) ₂ may be formed as a hydrate.

Specifically, by adding the sludge obtained from the recovery of ready-mixed concrete to the mixing water of the mortar composition, as a result, the solids are 5.0 to 10.0 wt% of the mixing water, and the solids are applied with 35 wt% or more of CaO, It activates the latent hydraulic properties of the blast furnace slag fine powder while the pH of the water shows strong alkalinity of 12 or more.

[Table 3] below shows the chemical composition ratio (unit: wt%) of the remicon recovered solids meeting the above conditions, and [Figure 1] shows the XRD component analysis results of the remicon recovered solids. It can be confirmed from [Figure 1] that the main hydration product of the recovered ready-mixed concrete is Ca(OH) ₂ .

SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO SO ₃ Insol. _S2O Na ₂ O Ig. loss 21.53 4.04 2.78 36.7 2.03 5.03 10.67 0.23 0.05 2.5

On the other hand, the ready-mixed concrete recovery may use a polymer coagulant containing 0.2 to 0.9 kg per 1000 liters. The solid material obtained from the recovery of ready-mixed concrete contains the polymeric coagulant component, so that the polymeric coagulant can act as a thickener in the lightweight mortar composition.

Aluminum sulfate (Al ₂ (SO ₄ ) ₃₎ is used to shorten the settling time by coagulating the dispersed cement suspended matter into sludge particles (floc) in the process of purifying the washing wastewater to produce ready-mixed concrete recovery water. A polymer coagulant made of raw materials such as ferric sulfate (Fe ₂ (SO ₄ ) ₃ ), ferric chloride (Fecl ₃ ), or polyaluminium chloride (PAC) may be used. Accordingly, when the solid obtained from the ready-mixed concrete recovery is added to the mixing water according to the present invention, the polymer coagulant is diluted and components such as methylcellulose, HPMC (Hydroxypropyl methylcellulose, Hydromellose) act as a thickener in the lightweight mortar composition . Conventionally, an expensive starch-based thickener was added to increase the viscosity of lightweight mortar, but through the present invention, the polymer coagulant contained in the ready-mixed concrete serves as a thickener without adding a separate thickener, thereby reducing the cost of mortar manufacturing. there is

The blast furnace slag fine aggregate has a particle diameter of 5 mm or less, It can be applied with a granularity of 2.3 to 3.1 and a specific gravity of 2.5 to 2.8 g/cm3, and by forming the fine aggregate with 70 to 90 vol% of natural fine aggregate and 10 to 30 vol% of blast furnace slag fine aggregate, the drying shrinkage rate compared to the blend using only natural fine aggregate is 6 ~10% reduction can be achieved.

In addition, by forming the fine aggregate with 60 vol% of natural fine aggregate and 40 vol% of blast furnace slag fine aggregate, the accelerated neutralization depth can be reduced by 10% or more compared to the mixture using only natural fine aggregate.

The above effect is due to the densification of the blast furnace slag fine aggregate and the reaction of the surface (see [Fig. 2]).

However, if the solids content is less than 5.0wt%, the reaction effect with cement is insignificant because the amount of hydrates produced is small, and conversely, if the solids content exceeds 10.0wt%, mixing design control for the expression of target physical properties is difficult due to excessive reaction components. It can cause difficult problems.

1. Test body (mixture table)

[Table 4] below is a composition table of mortar composition test specimens used to evaluate the performance of the present invention.

For each specimen, natural fine aggregate was replaced with blast furnace slag fine aggregate (replacement rate increased by 10 vol%), and mixing water containing the above solids was used. The solid material contains components such as CaO, Al ₂ O ₃ , and MgO, and accordingly, hydrate Ca(OH) ₂ is generated.

The fixed and variable values of each specimen mixture are as follows.

(1) fixed value

1) 5wt% of the solid content in the mixing water (Fixed at 5wt%, which is the content that minimizes the effect of generating hydrate within the range of the appropriate solid content, but Plain does not include the solid)

2) Water-cement ratio 50% (cement amount 340kg/㎥, mixing quantity 170kg/㎥)

(2) Fluctuation value

1) Blast furnace slag fine aggregate content (vol%) among fine aggregates

-RW5BS0: blast furnace slag fine aggregate 0vol%

-RW5BS10: blast furnace slag fine aggregate 10vol%

-RW5BS20: blast furnace slag fine aggregate 20vol%

-RW5BS30: blast furnace slag fine aggregate 30vol%

-RW5BS40: blast furnace slag fine aggregate 40vol%

2. Materials used

The materials used in the test are as follows.

(1) binder

As a binder, a type 1 ordinary Portland cement containing 64 wt% or more of CaO and 17 wt% or more of SiO ₂ , specific gravity of 3.1 to 3.2 g/cm 3 and fineness of 3500 to 3600 cm 2 /g was applied.

(2) Mixing water

In the test example, blending water having a solid content of 5.0 wt% was used. It is preferable to use 150 to 180 kg/m ³ per unit volume (m ³ ) of the mixing amount, and in this test example, the water-cement ratio was specified as 50%.

(3) fine aggregate

[Table 5] below shows the physical properties of the natural fine aggregate and the blast furnace slag fine aggregate used to evaluate the performance of the present invention.

The natural fine aggregate used in the present invention was used with a specific gravity of less than 2.6g/cm3 and a granularity of 2.45 or less, and the blast furnace slag fine aggregate with a specific gravity of less than 2.8g/cm3 and a coarseness of 2.3 or less was mixed at 10 to 40 vol% compared to the fine aggregate. The weight per unit volume (m ³ ) is 80 to 320 kg.

The blast furnace slag fine aggregate is a blast furnace slag impurity generated during the smelting of high-temperature molten pig iron in a steelmaking process, and is limited to a particle size of 5 mm or less generated by rapid cooling by cold water or cold air.

3. Test methods and results

To examine the flow characteristics and hardening characteristics of the mortar according to the change in the blast furnace slag fine aggregate replacement rate, the flow, compressive strength, and tensile strength of the mortar were measured according to the KS L 5105 and KS F 2423 test methods, respectively.

In addition, drying shrinkage and accelerated neutralization depth were evaluated to examine the durability performance characteristics of the mortar.

Drying shrinkage was measured using a contact gauge according to KS F 2424 “Length change test method of mortar and concrete”.

In the neutralization test, according to KS F 2584 “Test method for accelerated carbonation of concrete”, neutralization was accelerated until the required age using an accelerated neutralization test chamber under a CO ₂ concentration of 5%, and then the neutralization depth was measured using a phenolphthalein solution.

(1) Examination of mortar flow characteristics

[Figure 3] shows the results of the mortar flow test, and regardless of whether or not solids are included in the mixing water, the mortar flow value appears to be at the level of 180 ~ 200 mm according to the increase in the blast furnace slag fine aggregate mixing ratio, which increases as the blast furnace slag fine aggregate mixing increases. Flow values are shown.

Specifically, in the case of plain containing no solids in the mixing water, the flow value was less than 182 mm.

On the other hand, the flow value of the RW5BS0 specimen was about 184.5 mm, which was similar to that of Plain.

On the other hand, in the case of the RW5BS40 test specimen, the flow value was about 203mm, which was about 12% higher than that of Plain, and showed a higher flow value as the blast furnace slag fine aggregate mixing ratio increased.

(2) Review of mortar curing characteristics

The compressive strength and splitting tensile strength were measured to examine the hardening performance of the mortar with a solids content of 5.0 wt% in the mixing water and the mixing ratio of blast furnace slag fine aggregate.

[Figure 4] shows the amount of change in compressive strength, and in the case of 7 days of age, the RW5BS0 test specimen shows a value lower than Plain by 4%.

Overall, the compressive strength of the RW5BS20, RW5BS30, and RW5BS40 test specimens is about 38.3 to 39.5 MPa, which is similar to that of Plain (38.5 MPa).

In the case of 28 days of age, Plain and RW5BS0 specimens show similar values of about 43MPa, but in the case of RW5BS40 specimens, about 52.7MPa, about 18% higher strength value than RW5BS0 specimens can be obtained.

In the case of 56 days of age, Plain and RW5BS0 test specimens were 60.5MPa and 63.0MPa, respectively, and 4% higher compressive strength values could be obtained through the inclusion of solids in the mixing water.

In addition, in the case of RW5BS10, RW5BS20, RW5BS30 and RW5BS40 test specimens, approximately 3-8% higher level of compressive strength can be obtained compared to RW5BS0 specimen.

[Fig. 5] shows the amount of change in tensile strength of mortar with a change in the solids content of 5.0 wt% in the silver mixing water and the mixing ratio of the blast furnace slag fine aggregate.

Plain is 3.7MPa, RW5BS0, RW5B10, and RW5B20 test specimens are about 3.8MPa, and RW5BS30 and RW5BS40 specimens are 3.93MPa and 4.24MPa, respectively. Compared to Plain, about 5 to 14% higher tensile strength can be obtained.

(3) Mortar durability review

[Fig. 6] shows the change in drying shrinkage of the mortar in which the solids content of 5.0 wt% in the mixing water and the mixing ratio of the blast furnace slag fine aggregate were changed.

Plain shows similar shrinkage at 0.142% and RW5BS50 specimen at 0.144%. Shrinkage for RW5BS10, RW5BS20 and RW5BS30 specimens is about 0.128 to 0.133%, which is generally about 6 to 10% lower than Plain, and RW5BS30 specimen is about With a shrinkage rate of 0.128%, the highest drying shrinkage reduction effect can be obtained.

[Fig. 7] shows the accelerated neutralization depth of the mortar in which the solids content of 5.0 wt% in the mixing water and the mixing ratio of the blast furnace slag fine aggregate were changed.

Plain is 0.97mm, RW5BS0 specimen is 0.86mm, which is about 11% lower than Plain.

Although the physical properties and effects of the present invention have been reviewed through the test results above, the present invention will not be limited to the above test examples, and some modifications and changes are possible within the scope of the technical spirit of the present invention. will say that

Not applicable

Claims (5)

330 to 360 parts by weight of cement;
80 to 320 parts by weight of fine aggregate; and
160 to 180 parts by weight of blending water; Including,
The fine aggregate is composed of 60 to 90 vol% of natural fine aggregate and 10 to 40 vol% of blast furnace slag fine aggregate,
The blast furnace slag fine aggregate has a particle diameter of 5 mm or less, It has a granulation ratio of 2.3 to 3.1 and a specific gravity of 2.5 to 2.8 g/cm 3 ,
The blending water contains 5.0 to 10.0 wt% of the solids obtained from the recovery of ready-mixed concrete,
The solids contain 35 wt% or more of CaO,
The solids promote the reactivity of the blast furnace slag fine aggregate, and the blast furnace slag fine aggregate is densified while promoting crystal formation on the surface.
In paragraph 1,
The fine aggregate is composed of 70 to 90 vol% of natural fine aggregate and 10 to 30 vol% of blast furnace slag fine aggregate,
An eco-friendly mortar composition to which blast furnace slag fine aggregate and ready-mixed concrete recovery water are applied, characterized in that the drying shrinkage rate is reduced by 6 to 10% compared to the blend using natural fine aggregate alone.
In paragraph 1,
The fine aggregate is composed of 60 vol% of natural fine aggregate and 40 vol% of blast furnace slag fine aggregate,
An eco-friendly mortar composition applied with blast furnace slag fine aggregate and ready-mixed concrete recovery, characterized in that the depth of accelerated neutralization is reduced by 10% or more compared to the mixture using natural fine aggregate alone.
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