KR101223161B1 - High-Flowability and Low- Strength Concrete for Backfill - Google Patents

Abstract

The present invention relates to a concrete composition for use for ground replacement, such as ground improvement or backfill, more specifically, the unit replacement is filled with concrete with a small amount of high unit quantity, low binder but good fluidity Is about concrete.
Concrete for ground replacement use according to the present invention is concrete mixed with water, binder, fine aggregate, coarse aggregate and water reducing agent, the unit quantity of 185 ~ 205kg / ㎥, water-binder ratio of 90 ~ 105%, coarse aggregate The maximum size is 25mm, the aggregate aggregate is 52.5 ~ 57.5%, the binder is composed of one kind of cement and admixture, and the admixture is selected at least one of fly ash and blast furnace slag powder, the slump is 150mm or more and the air volume is 5 ~ 12% It is characterized by being formulated as.

Description

High-Flow Flowability and Low-Strength Concrete for Backfill

The present invention relates to a concrete composition for use for ground replacement, such as ground improvement and backfilling, and more specifically, a high unit quantity and a low amount of binder, but good fluidity, so that the concrete is filled with only a slight compaction. It's about concrete.

In order to secure the foundation strength of the ground where the strength is not secured in the house or construction work, the soil of the weak part is removed and the concrete is applied, or the concrete is placed in the empty space between the wall and the ground or the side of the concrete foundation and the ground. have. Most of the concrete used in these places is 15MPa concrete prescribed in KS standards.

However, since most of the strength of the ground replacement material is only 0.3 ~ 0.5MPa, the strength of 15MPa concrete is uneconomical. Therefore, it is easy to pour in the field, while securing the strength, the situation is required to develop economical concrete.

The present invention has been developed to provide concrete that can be economically used for ground replacement such as ground improvement or backfill, and there is a technical problem to provide concrete that can be conveniently and preferably used for ground replacement.

In order to solve the above technical problem, the present invention is a concrete compounded with water, binders, fine aggregates, coarse aggregates and water reducing agents, wherein the unit quantity is 185 to 205 kg / m 3, and the water-bonding agent ratio is 90 to 105%, The maximum size is 25mm, fine aggregate ratio is 52.5 ~ 57.5%, binder is 15 ~ 42% by weight of one kind cement, 28 ~ 40% by weight of blast furnace slag powder, 20 ~ 55% by weight of fly ash. It provides a high flow low-strength concrete composition for ground replacement, characterized in that the slump is 150mm or more and the amount of air is 5 to 12%. Here, the reducing agent may have a range of 0.5 to 0.7% by weight based on the amount of the binder.

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

First, because the slump provides more than 150mm of concrete for ground replacement purposes such as ground improvement or backfilling, the related work can be easily performed with only a few compactions.

Second, since the blast furnace slag powder and fly ash, which are cheaper than the first type cement, can be formed with a minimum amount of binding material, concrete material costs can be reduced in the ground replacement work, and thus related work can be economically performed. .

The biggest characteristic of concrete for ground replacement is to have low strength and high fluidity. Because the ground replacement work such as backfill, unlike the general concrete work hardly cares about compaction, the concrete should be filled well with a slight impact. Therefore, it is important to determine the appropriate unit quantity and minimum binder for concrete for ground replacement. The present invention proposes suitable unit quantities and binders in concrete for ground replacement applications. In other words, although the unit quantity is high and the binder content is low, the low strength is expressed, but the fluidity is good, and the concrete for the ground replacement use that can fill the concrete with only a little compaction is proposed.

Specifically, the concrete according to the present invention is concrete mixed with water, binders, fine aggregates, coarse aggregates, and water reducing agents, wherein the unit amount is 185 to 205 kg / m 3, and the water-bonding agent ratio is 90 to 105%, and the maximum size of the coarse aggregates. Is 25mm, fine aggregate is 52.5 ~ 57.5%, binder is composed of one kind cement and admixture. It is characterized by. Such a compounding ratio is the result according to the following [Examples 1-4], and according to this compounding, this invention shows the low intensity | strength characteristic of high fluidity, and can be used suitably for the ground substitution use.

In general concrete, when the maximum aggregate size is 25mm, the air volume is suggested to be 3 to 6%. However, the general concrete does not have a big problem in forming a high slump because the appropriate powder is secured by the amount of the binder to be at least 250 kg / m 3 or more. However, the present invention has a difficulty in forming a high slump because the amount of binder for the low strength is much less than that of ordinary concrete. In other words, since there are many aggregates (sand and gravel), even if the unit quantity is increased, it is difficult to obtain proper fluidity due to the small amount of powder. In order to solve this problem, the present invention sets a higher air mass standard than general concrete so as to secure fluidity without increasing the unit quantity.

On the other hand, the concrete according to the present invention has a very small amount of binder material, so to use the blast furnace slag fine powder and fly ash in order to ensure the maximum volume of the powder. The specific gravity of the first cement is 3.15, but the specific gravity of the blast furnace slag powder is about 2.9, and the fly ash is about 2.1 ~ 2.2. Therefore, when the blast furnace slag fine powder or fly ash is used, the powder volume can be increased for the same weight. Can be secured. Accordingly, the present invention proposes a three-component binder composed of 15 to 42% by weight of one kind of cement, 28 to 40% by weight of blast furnace slag powder, and 20 to 55% by weight of fly ash in consideration of the results of the following [Example 3]. In particular, fly ash is cheaper, so the more the amount used, the more economical it is advantageous. However, the amount of air decreases as the amount is increased due to the adsorption action of the AE agent by unburned carbon powder. Adjust it properly to mix. In addition, concrete for ground replacement may further include a water reducing agent in the range of 0.5 to 0.7% by weight based on the amount of binder.

Hereinafter, look at the present invention based on the embodiment. However, the examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1 Flowability of Concrete According to Unit Quantity

(1) Test method

In order to derive an appropriate mix of concrete suitable for ground replacement applications, the concrete mix was performed under the conditions shown in the following [Table 1].

Concrete mix division W / B S / a Unit material amount (㎏ / ㎥) Water reducing agent
(B x%) additional quantity W C FA One 75.3 52.8 113 120 30 0.5 2.00kg 2 78.8 52.5 165 178 30 0.5 - 3 78.8 52.5 165 178 30 0.5 0.50kg 4 75.0 57.5 150 100 100 0.5 1.22 kg C: Class 1 cement
-FA (fly ash): specific gravity 2.2
-S (grain aggregate): 1: 1 mixing with washing agent with specific gravity 2.6 and water absorption 1.0% and crushed sand with specific gravity 2.6 and water absorption 1.5%
-G (aS; coarse aggregate): maximum aggregate size 25mm, specific gravity 2.65, water absorption 0.8%
-Water reducer: Standard water reducer

In the above [Table 1], the additional quantity is an amount of additional administration of water due to the inappropriate physical properties after concrete mixing. For example, 40 liters of concrete was added, which means that 40 liters added 2 kg of water to the mix.

(2) Test result

As a result of testing the physical properties of the concrete for the compound of [Table 1], it is shown as [Table 2].

Properties of Concrete division slump
(mm) Air volume
(%) Compressive strength (MPa) 2 days 14 days 28 days One 40 4.4 - 2.6  3.3 2 15 4.8 4.0 12.4 15.2 3 120 8.2 3.0 8.3 10.9 4 160 6.4 - 2.3 3.6

As shown in Table 2, in the case of the formulation 1, when the quantity was added 2 kg, the slump exhibited poor workability such that 40 mm was obtained. The increase in yield of 2 kg means that 163 kg / m 3 increased by 50 kg / m 3, and thus, Formulation 2 was set similarly. However, the slump of 15mm was also derived, indicating poor workability. Therefore, the compounding 3 added the quantity to the compounding 2 to confirm workability, and the slump was greatly improved to 120 mm. The additional quantity at this time was 0.5kg for 40 liters, 12.5kg for 1㎥, and eventually 177.7kg / ㎥. In the case of formulation 4, the fly ash replacement amount was greatly increased, but the compounding was performed. However, due to poor workability, an additional amount of 1.22 kg was administered. As a result, the slump was good at 160 mm. The unit quantity at this time is about 180.5kg / m <3>.

The result of this experiment is that low slump value (more than 150mm) can not be obtained at low unit quantity, that is, about 180kg / ㎥ or less. According to this result, the present invention proposes a unit quantity of 185 to 205 kg / m 3.

Example 2 Flowability of Concrete According to Unit Bonding Capacity

(1) Test method

In order to derive the unit water quantity and water-bonding material ratio to ensure the fluidity of the concrete, the experiment was performed for the mixing ratio as shown in Table 3.

Concrete mix division W / B S / a Unit material amount (㎏ / ㎥) Water reducing agent
(B x%) W C FA 5 99 55 173 150 27 0.5 6 107.2 55 190 150 27 0.5 7 105 55 190 150 31 0.5 8 95.4 55 190 150 49 0.5 9 91.2 55 190 180 28 0.5 -C: 1 type cement
-FA (fly ash): specific gravity 2.2
-S (grain aggregate): cleaner with specific gravity 2.62, absorption 1.0%
-G (aS; coarse aggregate): crushed stone with maximum aggregate size 25mm, specific gravity 2.64, absorption 1.0%
-Water reducer: Standard water reducer

(2) Test result

As a result of testing the physical properties of the concrete for the compound of [Table 3], it is shown as [Table 4].

Concrete properties division slump
(mm) Air volume
(%) Compressive strength (MPa) 7 days 14 days 28 days 5 50 6.0 4.9 6.2 7.0 6 120 6.2 4.4 5.6 6.2 7 150 6.8 5.2 - 7.0 8 170 6.4 4.6 6.2 7.5 9 150 6.6 6.6 8.6 9.9

As shown in Table 4, when comparing the compound 5 and the compound 6, it can be seen that the slump increases from 50 mm to 120 mm when the unit quantity increases from 173 kg / m 3 to 190 kg / m 3 in the same state. In addition, when comparing the formulation 6 and 7, the amount of fly ash increased, indicating that the slump value also increased from 120 mm to 150 mm. In addition, high slump values were also observed in the formulations 8 and 9.

In summary with the results described in the above [Example 2], it can be said that the flow of concrete exhibiting a slump of 150mm or more only when the amount of the unit and the amount of unit bonding material is more than 180kg / ㎥.

[Example 3] The fluidity of concrete according to the amount of fine aggregate and the type of binder

(1) Test method

In order to understand the characteristics of the low strength concrete according to the change of the aggregate aggregate ratio (S / a) of the concrete and the composition ratio of the binder, the test was performed for the concrete mix of Table 5 below.

Concrete mix division W / B
(%) S / a
(%) Unit weight (kg / m3) SP
(B x%) W C SG FA S G FA20W190 95 60 190 160 - 40 1061 721 0.6 FA20W200 95.2 55 200 168 - 42 953 795 0.7 FA20W197 96.1 55 197 164 - 41 960 801 0.6 FA30 96.1 55 197 143 - 62 955 797 0.6 SG60 96.1 55 197 82 123 - 965 804 0.6 CSF442 96.1 55 197 82 82 41 957 798 0.6 CSF343 96.1 55 197 62 62 81 952 794 0.6 -C: 1 type cement
-FA (fly ash): specific gravity 2.1 Boryeong
-SG (blast furnace slag fine powder): 3 kinds, specific gravity 2.9
-S (grain aggregate): Crushed sand with specific gravity 2.60, absorption 1.2%
-G (aS; coarse aggregate): crushed stone with maximum aggregate size 25mm, specific gravity 2.65, water absorption 0.84%
-SP: standard water reducing agent

(2) Test result

As a result of testing the physical properties of the concrete for the compound of [Table 5], it is shown as [Table 6].

Concrete properties division Slump
(mm) Air
(%) Compressive strength (MPa) 3 days 7 days 28 days FA20W190 40 5.1 5.7 9.1 14.7 FA20W200 200 6.8 4.7 7.9 13.0 FA20W197 165 7.5 4.2 7.2 12.0 FA30 170 5.0 3.9 7.1 11.5 SG60 190 7.6 3.1 8.6 18.4 CSF442 200 5.6 2.5 6.7 14.2 CSF343 190 5.0 2.1 6.0 13.7

As can be seen in Table 6, the FA20W190 formulation had a 60% aggregate aggregate ratio, but the slump was about 40 mm, and the workability was very bad. Accordingly, excessively high aggregate aggregate ratio is considered to deteriorate workability.

On the other hand, in the case of FA20W200, the slump increased to 200mm as a result of lowering the aggregate aggregate rate to 55% and increasing the unit quantity and binder mass while maintaining the water binder ratio. Based on these results, the appropriate aggregate aggregate rate is estimated to be 55%.

Based on the above formulation, the unit quantity was fixed at 197kg / ㎥, the binder amount was 205kg / ㎥, and the composition ratio of the binder was changed. As a result, the amount of cement having one kind of cement (SG60, CSF442, CSF343) formed high fluidity. Appeared. This is because the specific gravity of cement is higher than that of slag powder or fly ash, so that the powder volume of the cement-rich binder is reduced. According to the results, the present invention proposes a three-component binder composed of 15 to 42% by weight of one kind of cement, 28 to 40% by weight of blast furnace slag powder, and 20 to 55% by weight of fly ash.

Example 4 Flowability of Concrete According to Composition Ratio of Binder

(1) Test method

The most important point in low strength concrete is that concrete strength is not an important issue, so produce concrete as economically as possible. At this time, the most important thing is to reduce the amount of cement used. In general, blast furnace slag fine powder or fly ash is cheaper than one kind of cement, so the more it is used, the more economical the formulation is. In this embodiment, the fluidity and strength characteristics of the case where the slag and fly ash are composed of various weight ratios were identified.

Concrete mix division
(Binder weight ratio) W / B
(%) S / a
(%) Unit weight (kg / m3) Water reducing agent
(B x%) W C SG FA S G 3: 4: 3 95 55 190 60 80 60 989 818 0.6 2.5: 4: 3.5 190 50 80 70 987 817 2: 4: 4 190 40 80 80 985 815 1.5: 4: 4.5 190 30 80 90 983 813 3: 3: 4 95 55 190 60 60 80 958 786 0.6 2.5: 3: 4.5 190 50 60 90 955 785 2: 3: 5 190 40 60 100 953 783 1.5: 3: 5.5 190 30 60 110 951 781 -C: 1 type cement
-FA (fly ash): specific gravity 2.2
-SG (blast furnace slag fine powder): 3 kinds, specific gravity 2.9
-S (grain aggregate): Washing agent with specific gravity 2.59, water absorption 0.91%
-G (aS; coarse aggregate): crushed stone with maximum aggregate size 25mm, specific gravity 2.65, water absorption 0.84%
-Water reducer: Standard water reducer

(2) Test result

As a result of testing the physical properties of the concrete for the compound of [Table 7], it is shown as [Table 8].

division Slump
(mm) Air
(%) Compressive strength (MPa) 28 days 3: 4: 3 180 6.0 11.9 2.5: 4: 3.5 200 5.4 10.4 2: 4: 4 200 6.8 9.3 1.5: 4: 4.5 200 6.0 8.4 3: 3: 4 190 8.0 9.6 2.5: 3: 4.5 200 7.0 9.5 2: 3: 5 190 7.8 8.5 1.5: 3: 5.5 200 6.6 7.6

As shown in Table 8, the concrete slump was 180 mm or more in all the formulations, indicating that the workability was very good. In addition, the concrete strength was 5 MPa or more in 28 days even when the amount of cement was reduced to 15% of the binder.

Claims (3)

Concrete blended with water, binders, fine aggregates, coarse aggregates and water reducing agents,
The unit quantity is 185-205kg / ㎥,
Water-binding ratio is 90-105%,
The maximum size of the coarse aggregate is 25mm,
Fine aggregate rate is 52.5 ~ 57.5%,
The binder is a three-component binder composed of 15 to 42% by weight of one kind cement, 28 to 40% by weight of blast furnace slag powder, and 20 to 55% by weight of fly ash,
High-flowing low-strength concrete composition for ground replacement, characterized in that the slump is 150mm or more and the amount of air is 5 to 12%. In claim 1,
The water reducing agent is a high flow low strength concrete composition for ground replacement, characterized in that it has a range to 0.5 to 0.7% by weight relative to the amount of the binder. delete