KR20220095345A - Light Weight Mortar Composite Using Ready-mixed Concrete Recovery Water - Google Patents

Abstract

The present invention relates to a lightweight mortar composition prepared by using ready-mixed concrete recovery water as an alkali stimulant for blast furnace slag fine powder and, more specifically, to technology, in which ready-mixed concrete recovery water is used to lightweight mortar prepared by using a blast furnace slag fine powder binder and artificial lightweight fine aggregates to allow the ready-mixed concrete recovery water to activate the blast furnace slag fine powder and is used for prewetting of the artificial lightweight fine aggregates and as mixing water for the lightweight mortar to enhance curing performance and durability of the lightweight mortar. The lightweight mortar composition of the present invention comprises: 320-450 kg/m^3 of a binder including 80-90 wt% of first-grade ordinary Portland cement and 10-20 wt% of blast furnace slag fine powder; 500-700 kg/m^3 of lightweight fine aggregates; and 150-160 kg/m^3 of mixing water, wherein the mixing water includes 5.0-10.0 wt% of ready-mixed concrete recovery water which has a solid content of 7.5-10.0 wt%, and the ready-mixed concrete recovery water promotes reactivity of the blast furnace slag fine powder. According to the present invention, the ready-mixed concrete recovery water is used as mixing water for a lightweight mortar composition to enhance economic efficiency in terms of costs for raw materials and ready-mixed concrete recovery water is treated as waste water to reduce a load to an environment.

Description

Light Weight Mortar Composite Using Ready-mixed Concrete Recovery Water

The present invention relates to a lightweight mortar composition using the ready-mixed concrete recovery as an alkali stimulant of the fine powder of blast furnace slag, and more particularly, by using the recovery of the ready-mixed concrete in the lightweight mortar using the fine powder of the blast furnace slag and fine artificial light aggregate, the ready-mixed concrete It is a technology to increase the hardening performance and durability of lightweight mortar by activating the fine powder of blast furnace slag with recovered water and using it as pre-wetting of artificial lightweight fine aggregate and as a mixing water for lightweight mortar.

Cement and cement secondary products, which are most widely used in the civil engineering and construction industries, are energy-consuming materials and emit about 1.3 tons of carbon dioxide to produce 1 ton of cement, which is important along with the steel industry.

In recent years, in order to reduce CO ₂ in the cement-related industry and to meet various performance requirements, research to use industrial by-products such as blast furnace slag fine powder as a substitute for cement is being actively conducted.

The blast furnace slag fine powder has a glassy film on the surface, so calcium and aluminum inside do not show hydraulic properties even when in direct contact with water. As it is cut, the calcium ions in the powder are gradually consumed, and it has latent hydraulic properties in which the hydration reaction proceeds.

Therefore, the concrete or mortar composition to which blast furnace slag fine powder is applied as a binder improves long-term strength, but has a problem of lowering initial strength. is known However, the calcium-based, aluminum-based, sulfate-based alkali stimulants that have been used in the past are all expensive chemicals, and thus cause an increase in the unit price of ready-mixed concrete.

On the other hand, the recovery of ready-mixed concrete is strongly alkaline, so if it is discharged or discarded without permission, it may cause environmental pollution, so a recycling method is required in the concrete-related industry.

The present invention has been researched and developed so that the components contained in the ready-mixed concrete recovery act as an alkali stimulant to activate the latent hydraulic properties of the blast furnace slag fine powder by adding the above ready-mixed concrete recovery to the mixing water.

1. Patent Publication No. 10-2020-0125141, "High-strength lightweight mortar composition comprising artificial lightweight fine aggregate pre-wetted with recovered ready-mixed concrete" 2. Registered Patent No. 10-1948627 "High-strength lightweight concrete composition containing artificial lightweight aggregate" 3. Registered Patent 10-1723204 "Remicon recovery water sludge powder, its manufacturing method and surface asphalt composition for surface layer" 4. Registered Patent 10-1470307 "Method for manufacturing non-toxic concrete using chemical admixture for concrete and recovered ready-mixed concrete"

1. Tae-Gyu Oh, Dong-Ju Lee, Seong-Ho Bae, Se-Jin Choi, "Fluidity and compressive strength characteristics of lightweight mortar applied with recovered water according to the mixing ratio of fine powder in blast furnace slag", Proceedings of the Fall 2019 Conference of the Korea Concrete Society Vol. 31 No. 2 (Volume 61) ), p.529-530, 2019.10. 2. Kyung-soo Lee, Tae-gyu Oh, Soo-bin Jeong, Jeong-hyeon Kim, Young-wook Kim, Se-jin Choi, "Pre-wetting of artificial lightweight aggregates using recovered water and strength characteristics of lightweight mortar", Proceedings of the 2019 Spring Conference of the Korean Concrete Society, Vol. 31, No. 1 (Vol. Vol. 60), p.407-408, 2019.05.

An object of the present invention is to provide an eco-friendly lightweight mortar composition in which ready-mixed concrete recovery activates the potential hydraulic properties of blast furnace slag fine powder by adding ready-mixed concrete recovery to a lightweight mortar formulation in which industrial by-products are used as binders and fine aggregates.

In order to solve the above problems, the present invention is "a binder composition comprising 80 to 90 wt% of cement and 10 to 20 wt% of blast furnace slag fine powder 320 to 450 kg/m ³ ; Lightweight fine aggregate 500~700kg/m ³ ; and mixing water 150~160kg/m ³ ; Light mortar composition, characterized in that the compounding water contains 5.0 to 10.0 wt% of the ready-mixed concrete recovery having a solid content of 7.5 to 10.0 wt%, and the recovery of the ready-mixed concrete promotes the reactivity of the blast furnace slag fine powder ' is provided.

It is preferable to apply that the solid content of the ready-mixed concrete recovery contains more than 35 wt% of CaO, and the mixed water to which the ready-mixed concrete recovery is added has a pH of 11 to 12.

In addition, the recovery of the ready-mixed concrete can be applied to contain 0.2 to 0.9 kg of the polymer coagulant per 1000 ℓ, so that the polymer coagulant acts as an alkali stimulus and a thickener in the lightweight mortar composition.

In addition, the lightweight fine aggregate is an artificial lightweight aggregate manufactured by mixing and calcining coal ash and dredged soil, having a particle diameter of 5 mm or less, a combined content of SiO ₂ and Al ₂ O ₃ of 80wt% or more, and a density of less than 1.8g/cm3. And, by pre-wetting for 24 to 26 hours in the ready-mixed concrete recovery, it is possible to reduce the drying shrinkage of the lightweight mortar composition and improve the neutralization penetration resistance.

According to the present invention, when the ready-mixed concrete recovery is applied as a compounding water of the lightweight mortar composition, the economic feasibility in terms of raw material cost is improved, and the environmental load caused by treating the ready-mixed concrete recovery with wastewater is reduced.

According to the present invention, the ready-mixed concrete recovery is used as an alkali stimulant of the blast furnace slag fine powder and as an immersion water for lightweight fine aggregates to promote the initial hydration reaction of the lightweight mortar to increase the initial strength, and when only the existing cement is used as a binder Hardening performance and durability performance equal to or higher than the comparison are expressed.

Specifically, when 5.0 to 10.0 wt% of the ready-mixed concrete recovery is included in the mixing water and 20 wt% or less of fine blast furnace slag powder is included in the binder, the initial strength and long-term strength are improved, and the drying shrinkage reduction performance and neutralization penetration resistance performance are improved. is improved

[Figure 1] shows the XRD component analysis result of the ready-mixed concrete recovery
[Figure 2] shows the flow change of the recovered water applied lightweight mortar according to the replacement rate of fine powder in blast furnace slag.
[Fig. 3] shows the change in compressive strength of the lightweight mortar composition by fixing the amount of ready-mixed concrete recovery to 5 wt% compared to the mixing water, and adjusting the blast furnace slag fine powder content.
[Figure 4] shows the change in tensile strength of the lightweight mortar at the age of 28 days by fixing the amount of ready-mixed concrete recovery to 5wt% compared to the mixing water, and adjusting the content of fine blast furnace slag powder.
[Figure 5] is a graph showing the drying shrinkage of the lightweight mortar composition by fixing the amount of ready-mixed concrete recovery to 5 wt% compared to the mixing water, and adjusting the content of fine blast furnace slag powder in the binder.
[Fig. 6] is a graph showing the neutralization penetration depth of the lightweight mortar composition at the age of 28 days by fixing the amount of ready-mixed concrete recovery to 5 wt% compared to the mixing water, and adjusting the content of fine blast furnace slag powder in the binder.

The present invention relates to a lightweight mortar composition used as an industrial by-product binder and fine aggregate, "a binder composition comprising 80 to 90 wt% of cement and 10 to 20 wt% of blast furnace slag fine powder 320 to 450 kg/m ³ ; Lightweight fine aggregate 500~700kg/m ³ ; and mixing water 150~160kg/m ³ ; Light mortar composition, characterized in that the compounding water contains 5.0 to 10.0 wt% of the ready-mixed concrete recovery having a solid content of 7.5 to 10.0 wt%, and the recovery of the ready-mixed concrete promotes the reactivity of the blast furnace slag fine powder ' is provided.

The raw materials applied to the present invention are as follows.

1. binder

In the present invention, the binder is 1,320 to 450 kg per unit volume (m ³ ), and the binder is composed of 80 to 90 wt% of cement and 10 to 20 wt% of fine blast furnace slag powder.

The cement is a type 1 ordinary Portland cement, and contains CaO 64wt% or more and SiO ₂ 17wt% or more, specific gravity 3.1~3.2g/cm3, and powderiness 3500~3600cm2/g.

The fine powder of blast furnace slag is an admixture material manufactured by cooling and finely pulverizing slag in a high temperature and molten state collected from a blast furnace for steel production. The blast furnace slag fine powder applied to the present invention contains 40 wt% or more of CaO and 30 wt% or more of SiO ₂ , and has a specific gravity of 2.8 to 3.0 g/cm 3 and a powderiness of 4,000 to 6,000 cm 2 /g.

2. Lightweight fine aggregate

In the present invention, the lightweight fine aggregate is used per unit volume (m ³ ) 500 to 700 kg.

The lightweight fine aggregate is an artificial lightweight aggregate manufactured by mixing and calcining coal ash and dredged soil, with a particle diameter of 5 mm or less, a combined content of SiO ₂ and Al ₂ O ₃ greater than 80wt%, and a density less than 1.8g/cm3, and ready-mixed concrete to be described later. Pre-wetting for 24-26 hours can be applied to the recovered water.

In general, when the aggregate contains a large amount of SiO ₂ and Al ₂ O ₃ components, the 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 generate alkali silicate gel and cause expansion. It can be said that it is a reaction that must be suppressed in the common sense of human technology.

However, in the present invention, by mixing and calcining coal ash and dredged soil, porous artificial lightweight fine aggregate having a lower density than general sand is prepared. Since the voids of the artificial lightweight aggregate itself or the voids of the adjacent artificial lightweight aggregate where the alkali aggregate reaction takes place are filled, volume expansion of the aggregate does not occur, but rather densification occurs (see Patent Publication No. 10-2020-0125141).

3. Mixed water

In the present invention, the binder is used per unit volume (m ³ ) of 150 to 160 kg/m ³ , and 5.0 to 10.0 wt% of the ready-mixed concrete having a solid content of 7.5 to 10.0 wt% is included in the blending water.

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

^* Washing Drainage: Water that washes concrete and spilled concrete attached to trucks, plant mixers, hoppers, etc.
^** Sludge water: Suspension water remaining after separating and collecting coarse and fine aggregates in the washing drainage of concrete
^*** Symbol water: Water from which sludge solids have been removed from sludge water by sedimentation or other methods

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

^* Sludge: The sludge is concentrated and the fluidity is lost.
^** Sludge solid content: obtained by drying sludge at 105~110℃

The solid content contains components such as CaO, Al ₂ O ₃ , MgO, and thus a hydrate is generated _. By limiting it, a technical concept was derived that the recovery of ready-mixed concrete could be used as an alkali irritant for blast furnace slag fine powder.

Specifically, by adding the ready-mixed concrete recovery to the blending water of the mortar composition, the ready-mixed concrete recovery is 5.0 to 10.0wt% of the blending water, and the blending water has a solid content of 7.5 to 10.0wt%. The solid content is to activate the latent hydraulic properties of the blast furnace slag fine powder while exhibiting strong alkalinity of 12 or more of the blended water to which the ready-mixed concrete recovery water is added by applying the one containing more than 35 wt% of CaO.

[Table 3] below shows the chemical composition ratio (unit: wt%) of the recovered ready-mixed concrete solids satisfying the above-mentioned conditions, and [Figure 1] shows the XRD component analysis results of the ready-mixed concrete recovery. From [Fig. 1], it can be seen that the main hydration product of the ready-mixed concrete recovery is Ca(OH) ₂ .

SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO SO ₃ Insol. S ₂ O 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

Hereinafter, the present invention will be described in detail with specific test examples.

1. Test 1 "Review of lightweight mortar properties according to ready-mixed concrete recovery concentration

The fixed and variable values for examining the properties of lightweight mortar according to the concentration of recovery of ready-mixed concrete are as follows.

(1) fixed value

1) Water-binder ratio 45% (binding material amount 340kg/㎥, mixing water amount 153kg/㎥)

2) Blast furnace slag fine powder content of binder 20wt%

2) 7.5wt% of solid content in recovery of ready-mixed concrete (35wt% of CaO content in solid content)

3) Light-weight fine aggregate 516kg/㎥ (100wt% of artificial lightweight aggregate described above, 24 hours pre-wetting in the aforementioned ready-mixed concrete recovery water)

(2) Variable value

1) Change the content of recovered ready-mixed concrete in the mixing water by 2.5wt% in the range of 0~15wt% (RW0, RW2.5, RW5, RW7.5, RW10, RW12.5, RW15)

As a result of testing the mortar flow and compressive strength for each of the above test examples according to the KS L 5105 test method, the content of the recovered ready-mixed concrete in the mixing water was in the range of 5.0 to 10.0 wt%, and the mortar flow was 180 to 190 mm. There was no decrease in fluidity, and it was found to have a significant effect in terms of strength development.

Specifically, when the ready-mixed concrete recovery content in the blending water exceeds 10 wt%, the mortar flow was lowered to less than 170 mm, and the 28-day compressive strength was 10% compared to the example (RW0) in which the ready-mixed concrete recovery was not applied. has been lowered more than

If the content of recovered ready-mixed concrete in the mixing water is less than 5 wt%, there is no problem with mortar flow and long-term strength, but it has little effect on early strength development within 7 days, and it has been shown that it does not have a significant effect on strength over 28 days of age.

2. Test 2: Rheological properties and hardening properties of lightweight mortar according to the use of blast furnace slag fine powder and ready-mixed concrete recovery

The fixed and variable values for examining the rheological properties and hardening properties of lightweight mortar according to the use of blast furnace slag fine powder and ready-mixed concrete recovery are as follows. Mortar flow and compressive strength were measured in accordance with KS L 5105, and tensile strength was measured according to KS F 2423 “Test method for splitting tensile strength of concrete”.

(1) fixed value

1) Water-binder ratio 45% (binding material amount 340kg/㎥, mixing water amount 153kg/㎥)

2) 7.5wt% of solid content in recovery of ready-mixed concrete (35wt% of CaO content in solid content)

3) 5wt% of ready-mixed concrete recovered content in mixing water (RW5)

4) Light-weight fine aggregate 516kg/㎥ (100wt% of artificial lightweight aggregate described above, 24 hours pre-wetting in the aforementioned ready-mixed concrete recovery water)

(2) Variable value

1) Change the content of fine blast furnace slag powder in the binder by 10wt% in the range of 0~50wt% (B0, B10, B20, B30, B40, B50)

[Figure 2] shows the flow change of the light mortar applied with the recovery water according to the replacement rate of the blast furnace slag fine powder. When the fine blast furnace slag powder is mixed in 20 wt% or less of the binder, it is about 185 to 189 mm, similar to the non-mixed example (B0). Flow values are shown.

However, when 30 wt% or more of the fine blast furnace slag powder was mixed in the binder, the flow value was about 172 to 174 mm, which was about 5.9 to 8.9% lower than that of the mixture containing 20 wt% or less of the fine blast furnace slag powder. This is considered to be because the filling effect between the particles is enhanced and the viscosity between the binders is remarkably improved as the content of the fine blast furnace slag powder having a large fineness is increased.

As can be seen from [Fig. 3], which shows the change in the compressive strength of the lightweight mortar composition according to the mixing ratio of the fine blast furnace slag powder, the compressive strength of the RW5B10 and RW5B20 formulations with 10 wt% and 20 wt% of the blast furnace slag fine powder applied at 7 days of age was about 35.6 At ~35.8 MPa, strength equivalent to or higher than that of RW5B0 formulation (34.9 MPa) was expressed.

This is considered to be the result of effectively contributing to the potential hydraulic reaction of the blast furnace slag fine powder through the alkali activation reaction when the blast furnace slag fine powder is replaced by 20 wt% or less.

On the other hand, even at the age of 28 days and the age of 56 days, the highest level of strength was expressed at about 49.3 MPa and 56.9 MPa, respectively, in the RW5B20 blend in which 20 wt% of the blast furnace slag fine powder was applied in the binder, and the hydration product of the ready-mixed concrete recovery was a mortar composition It is also found to be contributing to the development of long-term strength of However, in the RW5B30, RWB40, RW5B0 blend to which 30wt% or more of blast furnace slag fine powder is applied, the compressive strength is about 11.6~23.4% lower than that of RW5B0 blend without blast furnace slag fine powder. It can be seen that can be lowered.

[Figure 4] shows the change in tensile strength of the lightweight mortar at 28 days of age according to the mixing ratio of fine blast furnace slag powder. In the RW5B20 mixture containing 20 wt% of fine blast furnace slag powder, it was about 3.6 MPa, which showed a relatively high level of strength compared to other formulations. became

On the other hand, the RW5B0 blend without blast furnace slag powder was about 3.1 MPa, and the tensile strength was about 3.1 to 15% lower than that of the RW5B10, RW5B20, RW5B30, RW5B40, RW5B50 blends using fine blast furnace slag powder.

Like the compressive strength, the recovery of ready-mixed concrete acts as an alkali irritant and contributes to the latent hydraulic reaction of the blast furnace slag fine powder, resulting in relatively high tensile strength.

3. Test 3: Durability of lightweight hardened body by using blast furnace slag fine powder and ready-mixed concrete recovery

The test example formulation for the durability evaluation of the lightweight hardening body according to the use of blast furnace slag fine powder and ready-mixed concrete recovery is the same as in "Test 2" above. Drying shrinkage and neutralization depth were measured, and in the case of drying shrinkage, it was measured using a contact gauge in accordance with KS F 2424 “Test method for length change of mortar and concrete”.

In the neutralization test, in accordance with KS F 2584 “Test Method for Accelerated Carbonation of Concrete”, the neutralization depth was measured using a phenolphthalein solution after accelerated neutralization using a neutralization chamber under a CO ₂ concentration of 5% environment to the required age.

[Fig. 5] shows the change in drying shrinkage of the lightweight mortar composition according to the mixing ratio of the blast furnace slag fine powder, and 5 wt% of the ready-mixed concrete recovery is applied and the blast furnace slag fine powder is about 0.146 to 0.158% in all formulations using the fine blast furnace slag powder. The shrinkage rate was about 5.9~13.1% lower than that of the RW5B0 blend (0.168%) without using RW5B0.

[Figure 6] shows the neutralization depth of the lightweight mortar composition according to the mixing ratio of the blast furnace slag fine powder at the age of 28 days. A low level of neutralization depth was observed. In addition, even when the mixing ratio of fine blast furnace slag powder was 30wt% or more, the neutralization depth was about 3.5~13.3% lower than that of RW5B0 blend (2.26mm) without using fine blast furnace slag powder. It is also considered that the recovery of ready-mixed concrete contributes to the latent hydraulic reaction of the blast furnace slag fine powder, so that the inside of the specimen is sealed and the neutralization depth is low.

On the other hand, the recovery of the ready-mixed concrete uses 0.2 to 0.9 kg of the polymer coagulant per 1000 ℓ, so that the polymer coagulant can serve as a thickener in the lightweight mortar composition.

Aluminum sulfate (Al ₂ (SO ₄ ) ₃₎ to shorten the settling time by aggregating the cement suspension material dispersed in the process of generating ready-mixed concrete recovery by purifying the washing waste into sludge particles (floc), A polymer coagulant prepared from raw materials such as ferric sulfate (Fe ₂ (SO ₄ ) ₃ ), ferric chloride (Fecl ₃ ), and polyaluminum chloride (PAC: Polyaluminium Chloride) may be used. In this case, as the ready-mixed concrete recovery water is added as a part of the blending water according to the present invention, the polymer coagulant is diluted so that components such as methylcellulose and HPMC (Hydroxypropyl methylcellulose, Hydromellose) act as a thickener in the lightweight mortar composition. Conventionally, expensive starch-based thickeners have been added to increase the viscosity of lightweight mortar, but through the present invention, without adding a separate thickener, the polymer coagulant contained in the ready-mixed concrete recovery serves as a thickener, thereby reducing the mortar manufacturing cost. have.

Although the present invention has been described in relation to the embodiments as mentioned above, various modifications and variations are possible 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 preceding invention.

Not applicable

Claims (5)

320~450kg/m ³ of binder composed of 80~90wt% of cement and 10~20wt% of fine blast furnace slag powder;
Lightweight fine aggregate 500~700kg/m ³ ; and
Mixing water 150~160kg/m ³ ; It is composed including
The mixing water contains 5.0 to 10.0 wt% of the ready-mixed concrete recovery having a solid content of 7.5 to 10.0 wt%, and the light-weight mortar composition, characterized in that the ready-mixed concrete recovery promotes the reactivity of the blast furnace slag fine powder.
In claim 1,
The solid content of the ready-mixed concrete recovery is a lightweight mortar composition, characterized in that CaO is contained in 35wt% or more.
In claim 2,
Light mortar composition, characterized in that the mixing water mixed with the ready-mixed concrete recovery water is at least pH 12.
In claim 3,
The ready-mixed concrete recovery contains 0.2 to 0.9 kg of polymer coagulant per 1000 ℓ,
Light mortar composition, characterized in that the polymer coagulant serves as a thickener in the lightweight mortar composition.
5. In any one of claims 1 to 4,
The lightweight fine aggregate is an artificial lightweight aggregate manufactured by mixing and calcining coal ash and dredged soil, a particle diameter of 5 mm or less, a combined content of SiO ₂ and Al ₂ O ₃ greater than 80wt%, a density less than 1.8g/cm3, and the ready-mixed concrete recovery A lightweight mortar composition, characterized in that it was pre-wetted for 24 to 26 hours.

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