JPH06144902A - Production of self-filling concrete - Google Patents

Abstract

PURPOSE:To provide a self-filling concrete from which the aggregate is hardly segregated. CONSTITUTION:An aggregate is coated with an aq. soln. contg. a quick setting agent, the concn. of the soln. is controlled to 0.1-3.0wt.%, and 2-15 pts.wt. of the soln. is deposited on 100 pts.wt. of the aggregate. A compd. selected from a group consisting of calcium chloride, sodium carbonate, sodium hydroxide, alum and water glass is used as the agent. Cement is added to such an aggregate, and the mixture is kneaded with water by the well-known method to obtain a self-filling concrete. Otherwise, a cement admixture is added to the aggregate together with cement, the mixture is kneaded with water to obtain the slef-filling concrete. The slump flow value of the self-filling concrete is controlled to >=40cm when the value is measured by the method stipulated in JIS-A1101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing self-compacting concrete which does not require compaction due to vibration when obtaining a hardened concrete. More specifically, it is used to obtain a concrete hardened material such as a construction material and a secondary product material, which increases the viscosity and fluidity of concrete, and enhances the separation resistance of aggregate, cement and water,
The present invention relates to a method for producing self-compacting concrete that does not require compaction due to vibration of a vibrator or the like.

[0002]

2. Description of the Related Art Conventionally, as a concrete construction method, concrete is put into a formwork in which reinforcing bars are reinforced.
Compaction is generally performed by vibrating a vibrator. However, in recent years, noise pollution by a vibrator during concrete construction has become a serious problem. Further, in the field of secondary product materials, building materials boards and the like are becoming thinner and bar arrangements are becoming higher in density, and compaction due to vibrator vibration is becoming difficult.

For this reason, it has been attempted to improve the fluidity of concrete so that it has self-filling property and can be compacted without using vibration by a vibrator. However, if the fluidity of concrete is increased, blockage due to aggregates will occur between the rebars and between the rebars / forms, and as a result, the filling properties will decrease and the concrete composition will become uneven, and the strength of hardened concrete will be increased. There were times when it caused a drop. The causes of the drawbacks due to the increase in the fluidity of such concrete are considered to be as follows. In other words, concrete is a mixture of substances with different specific gravity differences (specific gravity of each substance example: aggregate such as gravel or sand = 2.6, cement = 3.2, water = 1.0). It is considered that each substance is separated by this, and that the cement paste layer separates from the aggregate surface and the aggregates come into direct contact with each other, resulting in entanglement and blockage due to the aggregates between the reinforcements. is there.

In recent years, as a concrete that does not need to be compacted by a vibrator, a high performance concrete has been reported (Journal of Japan Society of Civil Engineers, October 1989 issue). This high performance concrete is one in which an admixture such as blast furnace slag or fly ash and a thickener are added to the concrete. But,
Also in this high performance concrete, the cement paste layer formed on the surface of the aggregate easily separates, and similarly to the above, the blockage due to the aggregate easily occurs between the reinforcing bars.

[0005]

Therefore, in the present invention, the state of the surface of the aggregate is changed so that the cement paste layer formed on the surface of the aggregate becomes difficult to separate, and the aggregate is directly contacted with each other. It is an object of the present invention to provide a self-filling concrete that avoids entanglement and that is unlikely to be blocked by aggregates between reinforcing bars.

[0006]

That is, the present invention provides an aqueous solution containing 0.1 to 3.0% by weight of a quick-setting material on the surface of an aggregate main body,
A method for producing self-compacting concrete with a slump flow value (JIS-A 1101) of 40 cm or more, characterized by adding cement to 2 to 15 parts by weight of aggregate to 100 parts by weight of the aggregate body. It is about.

The aggregate used in the present invention is one in which an aqueous solution containing a quick-setting material (hereinafter referred to as "quick-setting-material aqueous solution") is attached to the surface of the main body of the aggregate. Here, the aggregate main body means the conventionally used fine aggregate such as sand or gravel or coarse aggregate, but when the fine aggregate contains surface water, It means that the surface water is removed.

The quick-setting material used in the present invention means a material which is dissolved in water to form an aqueous solution and which, when cement is added to the aqueous solution, accelerates the hydration reaction of the cement. There is. Specifically, calcium chloride, sodium carbonate, sodium hydroxide, sodium aluminate, alum, and water glass are used alone or as a mixture and used as a quick-setting material.

The quick setting material is dissolved in water and adheres to the surface of the aggregate main body in the form of an aqueous solution. The concentration of the quick-setting admixture aqueous solution adhering to the aggregate body needs to be 0.1 to 3.0% by weight. When the concentration of the quick-setting admixture solution is less than 0.1% by weight, the amount of the quick-setting admixture present on the aggregate surface is too small,
Even if cement is added to the aggregate, the hydration reaction with water existing on the surface of the aggregate is not sufficiently promoted, and the cement paste layer formed on the surface of the aggregate remains fragile. Is easily peeled off from the aggregate, which is not preferable. On the other hand, if the concentration of the quick-setting admixture solution exceeds 3.0% by weight, excess quick-setting admixture will be present on the aggregate surface, and when the concrete is mixed, the quick-setting admixture will elute out of the cement paste layer or It is not preferable because it disperses and the fluidity of concrete decreases.

The amount of the quick-setting admixture solution adhering to the surface of the aggregate main body is 2 to 15 parts by weight with respect to 100 parts by weight of the aggregate main body. If the amount of the quick-setting admixture aqueous solution is less than 2 parts by weight, the amount of water and the quick-setting admixture present on the aggregate surface is too small, and even if cement is added to the aggregate, a sufficient layer is formed on the aggregate surface. It is not preferable because a thick cement paste layer is not formed. On the other hand, if the amount of the quick-setting adhesive aqueous solution exceeds 15 parts by weight, the amount of water present on the aggregate surface is too large, and the cement paste layer formed on the aggregate surface is too soft and dispersed. Since the cement paste layer easily peels off from the aggregate surface,
Not preferable.

Any method may be adopted to obtain the aggregate by adhering the quick-setting binder aqueous solution having a constant concentration on the surface of the aggregate main body at a constant quantitative ratio. In particular, the powder of quick-setting material is added to the surface of the main body of aggregate to which the quick-setting material is added, and then mixed to dissolve the quick-setting material in the surface water, resulting in the surface of the main body of aggregate. A method of adhering an aqueous solution of the quick-setting material having a constant concentration in a constant quantitative ratio is preferable. The reason for this is that a certain amount of surface water is attached to natural sand or gravel that is generally used as the aggregate body. Moreover, the quick-setting aqueous solution is mixed or sprayed on the main body of the aggregate or the main body of the aggregate to which surface water is attached, and the quick-setting aqueous solution of a constant concentration is attached to the surface of the main body of the aggregate at a constant quantitative ratio. You can also let it.

As described above, after obtaining an aggregate in which a fixed concentration and a fixed amount of the rapid binding agent aqueous solution are adhered to the surface of the aggregate main body,
Cement is added to and mixed with the aggregate. Then, the cement paste layer is formed on the surface of the aggregate, and then the cement admixture and the kneading water are added and mixed to obtain the self-compacting concrete. Also, the cement admixture may be added and mixed at the same time as the cement is added to the aggregate. After this, kneading water is added and mixed to obtain self-compacting concrete. It is also possible to add cement to the aggregate and at the same time add both the cement admixture and the kneading water and mix them to obtain a self-compacting concrete. The cement admixture referred to here is a substance added to concrete and means a substance other than aggregate, cement and water. Specifically, air entrainment agent, anhydrous gypsum-based strength enhancer, activated silica powder, waterproof material,
Water reducing agents, high-performance water reducing agents, water-soluble polymers, drying shrinkage reducing agents, fluidizing agents, waterproofing agents, expanding agents (materials), glass fibers, steel fibers, stone powder, fly ash, blast furnace slag and the like.

The self-compacting concrete obtained as described above has a slump flow value of 40 cm or more in the slump test specified in JIS-A 1101. Those having a slump flow value of less than 40 cm have insufficient self-filling property and cannot be used in the present invention. When the self-compacting concrete is put into the mold or the like, the self-compacting concrete will be self-compacted in the mold without being vibrated by a vibrator. After that, the concrete is cured by a conventionally known method to obtain a concrete hardened body. As a curing method, a general method may be used, or a steam curing method or an autoclave curing method may be adopted.

[0014]

【Example】

Examples 1 to 4 and Comparative Examples 1 and 2 First, fine aggregate with surface water attached [sand from Kinokawa (specific gravity
2.57, FM2.91)] and coarse aggregate with surface water [Takarazuka crushed stone (specific gravity 2.61, FM6.34)] were prepared. The quantitative ratio of the surface water was 7.0 parts by weight based on 100 parts by weight of the aggregate main body. In the examples, the expression “aggregate” is used to collectively express both fine aggregate and coarse aggregate. A predetermined amount of powder of water glass (quick setting material) was added to 767 kg of the fine aggregate and 952 kg of the coarse aggregate to obtain the aggregate shown in Table 1.

[0015]

[Table 1] In addition, A in Table 1 indicates the amount of the quick-setting admixture aqueous solution in the aggregate, and represents how much (part by weight) the quick-setting admixture aqueous solution exists with respect to 100 parts by weight of the aggregate main body. It is a thing.
Further, B in Table 1 represents the concentration (% by weight) of the quick-setting admixture aqueous solution in the aggregate.

Then, 400 kg of cement and blast furnace slag (specific surface area of 8000 cm) as a concrete admixture are added to this aggregate.
46 kg of ² / g, specific gravity 2.90) were added and mixed, and then 175 kg of kneading water was added. At this time, 1 in the kneading water
It contains 3.2 kg of naphthalene sulfonic acid metal salt formaldehyde condensate (Kao Co., Ltd. high-performance water reducing agent) and 0.4 kg of β-glucan, so the concentration of mighty 100 in the kneading water is about 1.8% by weight. The concentration of β-glucan was about 0.2% by weight. Fifty liters of the concrete compounded as described above was kneaded for 2 minutes under a condition of 20 ° C. using a tilting mixer having a capacity of 100 liters to obtain a self-compacting concrete. The slump flow value of this self-compacting concrete and the separation resistance of the aggregate were evaluated. The results are also shown in Table 1. The separation resistance of the aggregate is evaluated by visually observing whether or not the aggregate is separated from the concrete. × indicates that the aggregate separates, and ○ indicates that the aggregate does not separate. It was evaluated.

Examples 5 to 7 and Comparative Examples 3 and 4 Fine aggregates having different surface water quantitative ratios [Kinokawa sand (specific gravity: 2.
57, FM2.91)] and coarse aggregate [crushed stone from Takarazuka (specific gravity 2.61,
FM6.34)] was used in the same manner as in Example 1 to obtain the aggregates shown in Table 1. Then, in the same manner as in Example 1, a self-filling concrete was obtained. The slump flow value of this self-compacting concrete and the separation resistance of the aggregate were evaluated. The results are also shown in Table 1.

Examples 8 to 10 Instead of the water glass (quick setting material) used in Example 1, Table 2
Aggregates as shown in Table 2 were obtained in the same manner as in Example 1 except that the various quick-setting materials shown in Table 1 were used. Then, in the same manner as in Example 1, a self-filling concrete was obtained. The slump flow value of this self-compacting concrete and the separation resistance of the aggregate were evaluated. The results are shown in Table 2.

[0019]

[Table 2]

As is clear from the results shown in Tables 1 and 2,
When 2 to 15 parts by weight of the quick-setting admixture solution is adhered to 100 parts by weight of the main body of the aggregate and the concentration of the quick-setting admixture is 0.1 to 3.0% by weight is used. In the case (according to the example), it is found that the aggregate becomes difficult to separate and the slump flow value becomes high. Therefore, when the self-compacting concrete according to the example is used, the cement paste layer is difficult to separate from the aggregate surface, and it is possible to prevent the blockage by the aggregate between the reinforcing bars due to the contact between the aggregates and the entanglement. It is possible and has excellent self-filling property. On the other hand, the concentration of the quick-setting material adhering to the aggregate body surface is 0.1
When the content is less than wt% (Comparative Example 1), it is found that the aggregate easily separates in the self-compacting concrete, and when the concentration exceeds 3.0 wt% (Comparative Example 2)
Shows that the slump flow value is less than 40 cm. In addition, it was found that when the quick setting aqueous solution was not adhered to the surface of the aggregate body (Comparative Example 3), the aggregate was easily separated in the self-compacting concrete, and the surface of the aggregate body exceeded 15 parts by weight. It can be seen that the slump flow value becomes less than 40 cm when the quick setting material aqueous solution is applied (Comparative Example 4). Therefore, when the self-compacting concrete according to the comparative example is used, the cement paste layer is easily separated from the aggregate surface, and due to the contact and entanglement between the aggregates, the blockage due to the aggregates between the bar arrangements is likely to occur. Or, the slump flow value becomes less than 40 cm, which results in poor self-filling property.

[0021]

In the self-compacting concrete obtained by the method according to the present invention, the action mechanism for making it difficult for the aggregate to separate can be inferred as follows. That is, if only water adheres to the surface of the aggregate body, when the cement powder is added, the cement powder mixes with the water on the aggregate surface to form a cement paste layer. However, in a cement paste layer formed only with water and cement powder, the strength of the layer itself is not sufficient, and the adhesive force with the surface of the aggregate body is not sufficient, so that when the concrete is filled, the cement is removed from the aggregate surface. It is considered that the paste layer peels off and the aggregate separates. On the other hand, when the quick-setting adhesive aqueous solution adheres to the surface of the aggregate body, when cement powder is added, the cement paste layer is formed in a state where the hydration reaction of the cement particles has sufficiently progressed, and this layer It is considered that the strength of itself improves and the adhesive force with the surface of the aggregate main body also improves. Therefore, it is considered that the cement paste layer formed on the surface of the aggregate is less likely to be peeled off, and the aggregate is less likely to be separated at the time of filling the concrete.

[0022]

EFFECT OF THE INVENTION The self-compacting concrete obtained by the method according to the present invention, due to the above-mentioned actions, has a greater degree of separation of aggregate in the concrete than the conventional self-compacting concrete whose fluidity is only increased. It is difficult to do so, direct contact between the aggregates and entanglement can be prevented, and blockage due to the aggregates that occurs between bar arrangements can be prevented. Therefore, if the self-compacting concrete obtained by the method according to the present invention is used, the filling property is good, it is possible to prevent the non-uniformity of the concrete composition, and prevent the strength reduction of the obtained concrete hardened body. The effect of being able to do is produced.

Claims (2)

[Claims] 1. An aqueous solution containing 0.1 to 3.0% by weight of a quick-setting material on the surface of an aggregate main body in an amount of 2 to 15 per 100 parts by weight of the aggregate main body.
A method for producing a self-compacting concrete having a slump flow value (JIS-A 1101) of 40 cm or more, which comprises mixing an adhering material adhering by weight with cement and a cement admixture, and then adding kneading water. 2. A compound selected from the group consisting of calcium chloride, sodium carbonate, sodium hydroxide, sodium aluminate, alum, and water glass is used as the quick-setting material.
A method for producing self-compacting concrete with a stated slump flow value (JIS-A 1101) of 40 cm or more.