JP4286619B2 - Method for producing porous concrete - Google Patents

Description

  The present invention relates to a method for producing porous concrete having a large number of continuous voids and excellent drainage properties.

Porous concrete has many continuous voids and a large volume ratio of voids, so it has good drainage, sound absorption, etc., roadway, sidewalk, parking lot, river bank, rooftop garden, roadway noise barrier It is used as a material for cured bodies such as.
Conventionally, various methods are known as methods for preparing a kneaded material before hardening of porous concrete.
For example, a method is known in which blast furnace cement and coarse aggregate are sequentially put into a forced kneader and kneaded and then kneaded, and then a cement dispersant is added with kneading water and kneaded to obtain porous concrete (Patent Document 1). reference).
Also, cement, blast furnace slag fine powder, water and dispersant (high-performance water reducing agent) are kneaded using a Hobart mixer for mortar kneading to obtain a paste. It is known that a porous concrete is obtained by putting it into a kneaded mixture (see Patent Document 2).
JP-A-11-217277 JP 11-268969 A

As described in Patent Documents 1 and 2 described above, a forced kneading mixer such as a biaxial mixer and a pan mixer has been conventionally used as a mixer for kneading porous concrete materials. Here, the forced kneading mixer refers to a mixer forcibly kneaded with a rotating stirring blade.
When the material of porous concrete is kneaded using a non-forced kneading mixer such as a tilted barrel type mixer, separation of dumpling-like mortar lumps and materials occurs, and a good porous concrete having a uniform structure can be obtained. Can not.
Therefore, there is a problem that porous concrete cannot be manufactured in a concrete manufacturing factory in which only a non-forced kneading mixer such as a tilted barrel mixer is installed.
The present invention is intended to solve such a problem, and even when a non-forced kneading mixer such as a tilted barrel mixer is used as a mixer for kneading porous concrete materials, It is an object of the present invention to provide a method capable of producing a good porous concrete having a uniform structure without causing material separation.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor, even when a non-forced kneading mixer such as a tilted barrel mixer is used as a mixer for kneading the porous concrete material, Among the materials, first, coarse aggregate, water and water reducing agent are mixed in a mixer for a predetermined time to obtain a mixture in which the water reducing agent is uniformly dispersed, and then cement is added to the mixture and further kneaded for a predetermined time. Thus, the inventors have found that a good porous concrete having a uniform structure can be obtained without causing mortar mass and material separation, and the present invention has been completed.

That is, the method for producing porous concrete according to the present invention (Claim 1) is a method for producing porous concrete using at least cement, coarse aggregate, water and a water reducing agent as materials. A first step of mixing 70 to 100% by weight of each total amount and 0 to 20% by weight of the total amount of cement in a non-forced kneading mixer for mixing concrete; And a second step of adding the remainder of the material to the mixture and kneading to obtain porous concrete.
Here, as the non-forced kneading mixer, for example, a tilted barrel type mixer is mentioned (claim 2 ).
The method of the present invention, in at least one of the first step and the second step may be added fine aggregate (claim 3).

  According to the method for producing porous concrete of the present invention, even when a non-forced kneading mixer such as a tilted barrel mixer is used as a mixer for kneading, a uniform structure is obtained without causing mortar mass and material separation. A good porous concrete can be produced.

In the present invention, cement, coarse aggregate, fine aggregate, water, a water reducing agent, and an admixture blended as necessary are used as the material for the porous concrete.
Examples of the cement include Portland cement such as ordinary Portland cement, early-strength Portland cement, and ultra-early strong Portland cement, and eco-cement.
As the coarse aggregate, gravel, crushed stone or a mixture thereof, a lightweight aggregate or the like is used.
The particle size of the coarse aggregate is usually 1.2 to 20 mm. The particle size of the coarse aggregate is appropriately determined according to the application of the porous concrete.

As the fine aggregate, river sand, sea sand, mountain sand, crushed sand, or a mixture thereof is used. By mix | blending a fine aggregate, the shrinkage | contraction by drying after hardening of a kneaded material can be suppressed.
The particle size of the fine aggregate is less than 5 mm, preferably 2.5 mm or less when the particle size of the coarse aggregate is 5 mm or more, and 5 mm when the particle size of the coarse aggregate is 1.2 mm or more and less than 5 mm. Less than, preferably 1.2 mm or less.
If the particle size of the fine aggregate is too close to the particle size of the coarse aggregate, the above-described effect (suppression of shrinkage after hardening) cannot be sufficiently exhibited by blending the fine aggregate.
The compounding amount of the fine aggregate is usually 0 to 150 parts by mass, preferably 20 to 120 parts by mass with respect to 100 parts by mass of cement. When the blending amount of the fine aggregate exceeds 150 parts by mass, the strength expression of the kneaded product is lowered.
The amount of water is preferably 15 to 30 parts by mass with respect to 100 parts by mass of cement. When the blending amount is less than 15 parts by mass, it is not possible to ensure a sufficient time for operations such as placing after kneading, and formability, workability and the like are deteriorated. When the blending amount exceeds 30 parts by mass, the granules after granulation are bonded to each other and do not become independent from each other. Also, since the paste or mortar flows down, after being cast and cured The continuous voids are insufficiently and unevenly distributed, and the water permeability is lowered.

As the water reducing agent, for example, a lignin type, naphthalene sulfonic acid type, melamine type, polycarboxylic acid type water reducing agent, AE water reducing agent, high performance water reducing agent or high performance AE water reducing agent is used.
The blending amount of the water reducing agent is preferably 0.1 to 2.0 parts by mass, more preferably 0.4 to 1.6 parts by mass in terms of solid content with respect to 100 parts by mass of cement. When the blending amount is less than 0.1 parts by mass, it is not possible to ensure a sufficient time for operations such as placing after kneading, and formability, workability, and the like are deteriorated. When the blending amount exceeds 2.0 parts by mass, the granules after granulation are bonded to each other and do not become independent from each other, and the paste or mortar flows down. After the formation of the continuous voids, the water permeability is lowered due to insufficient and uneven distribution.
The water reducing agent can be used in either liquid or powder form.

As an admixture mix | blended as needed, inorganic powders, such as a blast furnace slag powder, a fly ash, a silica fume, a limestone powder, a silica stone powder, are mentioned, for example.
The proportion of the admixture in the total amount of cement and admixture is preferably 50% by mass or less, more preferably 30% by mass or less, from the viewpoint of strength development of the kneaded product.
The blending amount of the paste or mortar with respect to 100 parts by volume of the coarse aggregate is preferably 30 to 80 parts by volume. When the blending amount is less than 30 parts by volume, the strength development property of the kneaded product is lowered. When the blending amount exceeds 80 parts by volume, the granules after granulation are bonded to each other, so that the granules do not become independent from each other, and the paste or mortar flows out. The continuous voids are insufficiently and unevenly distributed, and the water permeability is lowered.

Next, the 1st process and the 2nd process which comprise the manufacturing method of the porous concrete of this invention are demonstrated.
[First step]
The first step is the first half of the method of the present invention, in which the coarse aggregate, water and water reducing agent are mixed in a non-forced kneading mixer for mixing concrete.
The amount of the coarse aggregate used in this step is 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, particularly preferably 100% by mass, based on the total amount of the coarse aggregate. If the amount used is less than 70% by mass, mortar lumps and material separation may occur in the second step.
The amount of water and water reducing agent used in this step is the same as that of the coarse aggregate, and is 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% of the total amount of each. % By mass. If the amount used is less than 70% by mass, mortar lumps and material separation may occur in the second step.
The amount of cement used in this step is 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 0% by mass with respect to the total amount of cement. If the amount used exceeds 20% by mass, mortar lumps and material separation may occur in the second step.

The amount of fine aggregate used in this step is 0 to 100% by mass of the total amount of fine aggregate. Fine aggregates may affect the quality of porous concrete and the mixing time necessary to obtain a uniform mixture even if the ratio of the amount used in the first and second steps is changed. Absent.
The amount of the admixture such as inorganic powder used in this step is 0 to 100% by mass of the total amount of the admixture. The admixture does not affect the quality of the porous concrete or the mixing time necessary to obtain a uniform mixture even if the ratio of the amount used in the first step and the second step is changed. .

In the present invention, the type of mixer for mixing concrete is a forced mixing mixer such as a biaxial mixer, a bread mixer, etc. for the purpose of the present invention that enables the production of porous concrete using a non-forced mixing mixer. other mixer (i.e., non-forced kneading mixer) is.
As a typical example of the non-forced kneading mixer, there is a tilt barrel type mixer.
The tilt-type mixer is a rotary drum having an opening that is attached to the tilt-drum mechanism so that it can be tilted, and when the concrete material is kneaded, the drum rotates with the opening facing obliquely upward, The kneading blades attached to the inner peripheral surface of the drum repeatedly knead the concrete material in the drum when it is lifted upward and drop by its own weight, and when the kneading is completed, the drum tilts. The mixer is configured such that the opening is directed obliquely downward and the kneaded concrete is discharged.

  The mixing time in the first step varies depending on the amount of materials in the mixer and the type of mixer, but is preferably 30 seconds or more, more preferably 1 to 5 minutes, and particularly preferably 1 to 3 minutes. When the mixing time is less than 30 seconds, it becomes difficult to uniformly disperse the water reducing agent in the mixture, and even if the process proceeds to the second step described later, good porous concrete having a uniform structure may not be obtained. . When the mixing time exceeds 5 minutes, the production efficiency is lowered, which is not preferable.

As a mixing procedure, first, coarse aggregate and water are put into a mixer and mixed for 5 to 15 seconds, then a water reducing agent is added and further mixed for 30 seconds or more (preferably 1 minute or more). Is desirable.
The mixture obtained in the first step is usually in a state where bubbles are generated. In the case of producing ordinary concrete having no water permeability, if foaming occurs when the concrete is kneaded, voids are present in the concrete after being placed and hardened, leading to a decrease in strength. However, in the present invention, foaming is not a problem because it is intended for porous concrete having a large volume ratio of voids.
In addition, you may mix | blend an antifoamer in order to reduce foaming.

[Second step]
The second step is the latter half of the method of the present invention, and the mixture in the mixer obtained in the first step is kneaded with the remainder of the material of the porous concrete, and formed by casting or the like. This is a step of obtaining a kneaded mixture of porous concrete before performing.
In this step, the amount of cement used is the remaining amount of the amount used in the first step, specifically, 80% by mass or more, preferably 90% by mass or more, more preferably 95% of the total amount of cement. It is at least 100% by mass, particularly preferably 100% by mass.
In this step, the amount of coarse aggregate, water and water reducing agent used is the remaining amount of the amount used in the first step, specifically, 30% by mass or less of the total blending amount for each of these materials, Preferably it is 20 mass% or less, More preferably, it is 10 mass% or less, Most preferably, it is 0 mass%.

The amount of fine aggregate and admixture used in this step is the remaining amount of the amount used in the first step, and is 0 to 100% by mass of the total blending amount for each material.
The kneading time in the second step varies depending on the amount of materials in the mixer and the type of mixer, but is preferably 30 seconds or more, more preferably 1 to 10 minutes, and particularly preferably 2 to 5 minutes. When the kneading time is less than 30 seconds, it is difficult to uniformly knead the material, and good porous concrete having a uniform structure may not be obtained. If the kneading time exceeds 10 minutes, it is not preferable because the time during which operations such as placing can be performed is reduced and the production efficiency is lowered.
After completion of the kneading, the kneaded material discharged from the mixer is used as porous concrete capable of forming a good cured body having continuous voids.

Hereinafter, the present invention will be described by experimental examples.
[Example 1]
(1) Materials used The following materials were used as materials for porous concrete.
1) Cement: Ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.)
2) Admixture: Blast Furnace Slag Powder (Daiichi Cement Co., Ltd .; trade name “Fine Serament 10A”)
3) Fine aggregate: mountain sand (particle size 2.5mm or less; fine from Ichihara)
4) Coarse aggregate: Crushed stone No. 7 (particle size 2.5-5.0mm; from Ome)
5) Water reducing agent: Naphthalenesulfonic acid-based high-performance water reducing agent (manufactured by Kao Corporation; trade name “Mighty 150”)
(2) Mixing of materials Each material was put into an inclined barrel mixer (drum capacity 0.1 m ³ ) by the blending amount shown in Table 1 and the mixing method shown in Table 2, and kneaded.

(3) Evaluation of kneaded product (a) Visual evaluation After kneading, the state of the obtained kneaded product is visually evaluated. If it is in a good state, “◯”, and occurrence of mortar mass and material separation are recognized. × ”.
(B) Measurement of bending strength The obtained kneaded material was put into a 10 cm × 10 cm × 40 cm mold and subjected to vibration molding using a vibration tamper. After molding, it was cured in water at 20 ° C. for 28 days to obtain a molded article of porous concrete. Using this molded body (three pieces), the bending strength was measured according to “JIS A 1106 (concrete bending test method)”.
(C) Measurement of continuous porosity According to the “Concrete porosity measurement method for porous concrete (draft)” by the Japan Concrete Institute, using the three molded bodies (b) above. The continuous porosity (volume%) was measured.

[Example 2, Comparative Examples 1 to 4]
Experiments were performed in the same manner as in Example 1 except that the mixing method was changed as shown in Table 2.
The results are shown in Table 3. In addition, the numerical value of Table 3 is an average value of the measured value of three molded objects.

Claims (3)

A method for producing porous concrete using at least cement, coarse aggregate, water and a water reducing agent as materials,
70 to 100% by mass of the total amount of each of coarse aggregate, water and water reducing agent, and 0 to 20% by mass of the total amount of cement are mixed in a non-forced kneading mixer for mixing concrete. One process,
A second step of adding porous material to the mixture in the mixer and kneading to obtain porous concrete;
A method for producing porous concrete, comprising: The method for producing porous concrete according to claim 1 , wherein the non-forced kneading mixer is a tilted barrel type mixer. The method for producing porous concrete according to claim 1 or 2 , wherein a fine aggregate is added in at least one of the first step and the second step.