JP2011140422A - Fine aggregate for mortar or concrete, and method for producing mortar or concrete using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To consider the problem in the well-known method by which fine aggregate is produced, in such a manner that, to the total content of fine particles included in limestone fine aggregate, the content of the prescribed fine particles in the above limestone reaches a prescribed value, additional fine particles including the limestone fine particles with a prescribed particle size or below are added, that a fixed effect can be obtained against bleeding, but, a new problem that drying shrinkage increases is generated, and to prevent the above problem jointly with the dissolution of the problem of the bleeding. <P>SOLUTION: In the fine aggregate for mortar or concrete, among all the fine particles passing through a particle size 0.075 mm sieve, the amount of the fine particles with limestone as the component is <1.0 mass%, also, the amount of one or more mineral fine particles not reacting with portland cement and comprising SiO<SB>2</SB>components, which are selected from andesite, basalt and sandstone is 3 to 12 mass%, and, except for the above fine particles, limestone is used as the main component. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fine aggregate for mortar or concrete, and a method for producing mortar and concrete using the same.

  Conventionally, as one of the aggregates used when manufacturing mortar and concrete, aggregates manufactured from limestone, that is, limestone aggregates for concrete, have been widely used for a long time.

  Limestone aggregate for concrete is crushed stone and crushed sand and has physical performance that meets the requirements of JIS A 5005. In addition, it is generally considered to be an aggregate that does not cause alkali aggregate reaction, and can be used to produce high-strength concrete. It is possible.

  Among such limestone aggregates for concrete, concrete limestone fine aggregates are generally manufactured by wet manufacturing at a manufacturing plant. Wet production of concrete limestone fine aggregate generally means adding flocculating agent and water to crushed material obtained by crushing limestone to a maximum particle size of 5 mm or less, and further grinding and granulating with a tube mill or the like. The limestone fine aggregate for concrete is manufactured by separating into separated turbid water containing fine particles of 0.15 mm or less and limestone sand having a particle diameter of more than 0.15 mm, that is, limestone fine aggregate.

  In order to obtain good quality mortar and concrete, various techniques are proposed for the production method of fine aggregates, not limited to the above-described wet production method. In the production process, techniques for obtaining a required particle size distribution and efficiency are proposed. Techniques for removing impurities well, techniques for obtaining fine aggregates that have been more reliably cleaned, and the like have been proposed (see, for example, Patent Documents 1 to 3).

  On the other hand, in concrete manufactured under certain conditions, it is known that the concrete after placing sinks, causes material separation, and bleeding occurs where water floats on the surface.

  For such bleeding, it is known to adopt a technique such as replacing a part of fine aggregate with metallurgical slag fine particles (see, for example, Patent Document 4).

JP 2000-290049 A JP 2001-48612 A JP 2002-128551 A JP 2000-247712 A JP 2009-234841 A

Furthermore, in the case of using a limestone fine aggregate produced in a wet manner, the limestone fine aggregate generates bleeding as compared with the crushed sand mainly composed of SiO ₂ as disclosed in Patent Document 4. It was known that the possibility was high.

  Further, the step of measuring the amount of fine particles having a predetermined particle size or less contained in the limestone fine aggregate, and the predetermined fine particles of the limestone with respect to the total amount of fine particles contained in the limestone fine aggregate and the limestone fine aggregate There is known a method for producing a fine aggregate by adding an added fine particle containing a limestone fine particle having a predetermined particle size or less so that becomes a predetermined value (Patent Document 5). However, in this method, it was found that the problem that drying shrinkage increases although a certain effect can be obtained with respect to bleeding newly emerges.

  Therefore, it was possible to prevent drying shrinkage and to solve the bleeding problem as a new issue.

In order to solve such a problem, the present invention has a particle size that passes through a sieve having a particle size of 0.075 mm (hereinafter referred to as a fine particle content), and the amount of the fine particle component of limestone is 1.0% by mass. The amount of fine particles of at least one mineral selected from andesite, basalt and sandstone containing SiO ₂ component, which is less than and does not react with Portland cement, is 3 to 12% by mass, and the particle size The particle | grains (henceforth a coarse particle part) which do not pass a 0.075mm sieve provide the fine aggregate for mortar or concrete characterized by being limestone. Furthermore, the said fine aggregate whose quantity of a fine particle is 3-9 mass% is provided.

Furthermore, it is a method for producing mortar or concrete using fine aggregates, and after coarsely pulverizing and further pulverizing limestone, the amount of fine limestone particles having a particle size of 0.075 mm or less is washed with water, sieved Mineral powder of one or more rock types selected from andesite, basalt and sandstone containing SiO ₂ component, prepared as limestone grains less than 1.0 mass% by treatment or water tank Is adjusted to a particle size of 0.075 mm or less, mixed with the limestone particles, and mortar or concrete using fine aggregate with a fine particle amount of 3-12% by mass or concrete A method for producing concrete is provided.

The production of limestone crushed sand is as follows. The rough ore is mined and transported to a shaft or plant through drilling, blasting and loading. The raw stones brought into the plant are primarily crushed with a jaw crusher and crushed to about 150 mm. After that, secondary and tertiary crushing and classification are performed with a finely divided jaw crusher or cone crusher, and the particle size (20-5 mm) as a crushed stone (coarse aggregate) for concrete is adjusted. The particle size adjusting sieve is used only for the purpose of classification in a dry plant, but is used in a wet plant that also serves as a water washing as well as classification.

A crushed stone is used as a raw material to produce concrete crushed sand (fine aggregate) having a particle size of 5 mm or less, and the sand making machine used at that time can use a general rod mill or the like. There are dry and wet methods for operating the rod mill, but the dry method is preferable because the productivity is low and the amount of fine powder generated is large.

Next, fine particle removal from the limestone crushed sand is performed as follows. For adjustment of fine particles of crushed sand (fine aggregate), the fine particles can be washed with water using a screen washer, a log washer, etc., which are the same mechanism as the classifier. It is also preferable to remove fine particles not only by such a wet cleaning method but also by dry sieving using a sieve net or the like.

Furthermore, the addition of fine particles of other rock species to the limestone crushed sand from which fine particles have been removed is performed as follows. For the purposes of the present invention, the fine particles of other rock types other than limestone can be produced by finely pulverizing the raw stones, etc. The finely pulverized product discharged in the classification process can be used.

It is obtained by adding a predetermined amount of fine particles of these other rock types to the limestone crushed sand from which fine particles of limestone have been removed, and uniformly dispersing the mixture with a mixer or the like. In addition, it is also preferable to prepare separately the limestone crushed sand from which limestone fine particles have been removed and the fine particles of other rock types, and put them in a predetermined amount into a mixer for producing mortar or concrete.

The inventors have found through many experiments that the drying shrinkage of hardened bodies using limestone fine aggregates until the age of 7 days is due to the progress of hydration such as alite. This is because the rapid hydration of alite or the like causes the pore structure to become dense and the overall volume decreases. Delaying the progress of hydration of alite or the like can be a measure for suppressing drying shrinkage.

However, this required a detailed and accurate understanding of the mechanism of the initial hydration of the cement. The surface of fine limestone less than 0.075 mm provides calcium silicate hydrate precipitation sites up to about 7 days of age, and the reaction of the limestone fine powder itself causes the surface of alite to become calcium silicate hydrate. It has been found that this delay effect is diminished with less coating. Therefore, it is effective to form a calcium silicate hydrate layer on the surface of alite, etc., to moderately ease early hydration of alite without reducing the properties of other hardened bodies. I found.

Calcium silicate hydrate concentrates on the surface of fine limestone powder that provides precipitation sites, and as a result, precipitation on the surface of alite or the like is reduced. This is because in the case of alite that is not surface-coated, the hydration reaction proceeds greatly from the surface and the tissue becomes dense.

However, when the limestone fine particles of less than 0.075 mm are removed, drying shrinkage can be prevented, but as a result of losing the fine particles and being unable to maintain the water retaining effect, the bleeding rate increased.

As a result of further diligent investigations, the increase in the bleeding rate was suppressed by substituting fine particles of rock species that are difficult to provide calcium silicate precipitation sites and have poor reactivity with cement.

Andesite, basalt, and sandstone are preferred as rock types with low reactivity with cement. These surfaces are unlikely to precipitate calcium silicate hydrate, but rather serve as calcium hydroxide precipitation sites, forming a porous transition region.

The fine particle content is preferably 3 to 12% by mass. If the fine particle content is less than 3% by mass, bleeding increases and the water transfer path becomes an internal defect. If the fine particle content is more than 12% by mass, the viscosity increases and the fluidity (flow value) starts to decrease. become. In the example of andesite, good results were obtained for both bleeding and drying shrinkage. Moreover, when it is 3-9 mass%, it is more preferable for the following reason. This is because if the fine particle content is more than 9% by mass, the amount of bleeding is extremely reduced, and even the bleeding when the surface finish of the mortar or the concrete placing surface is required is suppressed. In addition, fine particles of more than 9% by mass tend to cause decrease in fluidity and increase in drying shrinkage, tend to form a porous transition region containing a large amount of calcium hydroxide, and the initial compressive strength gradually decreases. It is because there is a possibility of doing.

On the other hand, in the experimental example in which the coarse fraction was andesite, the fine fraction was either andesite or limestone, and in bleeding, the dry shrinkage was large and satisfactory results were obtained even in the experimental example with good results. There wasn't. This is because, in the case of coarse particles, the specific surface area is large, unlike the fine particles, so that the reactivity with cement is low, and most of them function as physical restraints against shrinkage deformation. At that time, andesite has a lower elastic modulus than limestone, so the effect of restraining and reducing shrinkage is reduced. On the other hand, when limestone is used as the coarse particles, the effect of restraining shrinkage deformation and reducing shrinkage can be sufficiently exhibited due to its high elastic modulus.

When the fine aggregate is employed, drying shrinkage can be prevented, dimensional accuracy can be improved, bleeding problems can be solved at the same time, and mortar and concrete that avoids settling cracks can be produced.

  In particular, the method for producing mortar and concrete according to the present invention solves the problem of dimensional accuracy of limestone aggregate, which has been particularly dry shrinkage, and mainly uses limestone produced by wet production, which was supposed to cause bleeding. By using the fine aggregate, mortar and concrete having reduced bleeding can be produced.

  By applying the fine aggregates of the present invention to mortar or concrete materials that use limestone fine aggregates, durability that effectively avoids settling cracks due to bleeding with small drying shrinkage and high dimensional accuracy It becomes possible to easily produce mortar and concrete having high properties.

It is a figure which shows the drying period (days) change of the drying shrinkage strain which concerns on an experiment example.

Hereinafter, embodiments of the present invention will be described.

  Examples of the present invention are shown below, but the present invention is not limited to such examples.

The raw limestone was mined from the limestone mine, drilled, crushed and loaded, and transported to the shaft or plant. The raw stones brought into the plant were roughly crushed to about 150 mm with a jaw crusher. Then, it was further pulverized and classified with a finely divided jaw crusher, and adjusted to a particle size (20 to 5 mm) as crushed stone for concrete (coarse aggregate).

The sieve for particle size adjustment was used in a wet plant that was classified and used for water washing as well. Concrete crushed sand (fine aggregate) having a particle size of 5 mm or less was produced using crushed stone as a raw material, and a sand mill used at that time used a rod mill. The rod mill operation method is wet, which is highly productive and generates a small amount of fine powder.

For the adjustment of the fine particles of the crushed sand (fine aggregate), the fine particles were removed from the limestone crushed sand by washing with water using a screen washer which is the same mechanism as the classifier.

Next, the fine particles of other rocks other than limestone are crushed stones (coarse aggregates) and crushed sand (fine aggregates) of other rocks. A predetermined amount of fine particles of these other rock types was added to the limestone crushed sand from which fine particles of limestone had been removed, and the mixture was uniformly dispersed with a mixer (mixer).

The crushed sand according to the present invention thus produced can be used as a fine aggregate for mortar or concrete. In the experimental example used as a fine aggregate of mortar, water, cement, fine aggregate and an admixture were put into a mixer for mortar and kneaded for 3 minutes and subjected to various evaluation tests.

Here, the material used is
Water (W): Tap water cement (C): Ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd., density 3.16 g / cm3)
Admixture (SP): High performance water reducing agent Leopold SP8SV (manufactured by BASF Pozzolith) was used.
The fine aggregate (S) was based on the above production method.

  The composition was W / C = 50.0%, air amount: 5.0% by volume, W = 262 Kg / m3, C = 524 Kg / m3, S = 522 l / m3, SP = C × 1.1%.

Table 1 shows the fine aggregate with fine particles of 0.075 mm or more as limestone or andesite and 0.075 mm of fine particles (fine particles) as andesite or limestone. The fine particle amount (mass%) and density (g / cm ³ ) of the obtained fine aggregate were shown. The abbreviation LA09 indicates that the composition is composed of limestone coarse powder (L) and andesite fine particles (A) and about 9% fine particles (all 0.075 mm).

Table 2 shows the results of measuring the flow value, bleeding rate, drying shrinkage, and compressive strength of the experimental sample.

The flow value conformed to JISR5201. The amount of air was in accordance with JISA1128, the bleeding rate was in accordance with JSCE-F522-1999, Japan Society of Civil Engineers, the compressive strength was in accordance with JISA1108 using a test piece of 5φ × 10 cm, and the drying shrinkage was in accordance with JISA1129-2.

Evaluation criteria
Flow value ○: 180 mm or more, Δ: 160 to 180 mm, x: less than 160 mm bleeding rate ○: less than 3%, x: 3% or more dry shrinkage ○: less than 800 × 10 ⁻⁶ , Δ: 800 × 10 ⁻⁶ or more and 1000 When less than × 10 ⁻⁶ and ×: 1000 × 10 ⁻⁶ or more, the result of the characteristic values in Table 2 can be expressed as shown in Table 3.

In Experimental Example 6 excluding the limestone fine particles less than 0.075 mm, the drying shrinkage is the smallest among the experimental examples in the table. However, the bleeding rate reached its maximum.

FIG. 1 shows the drying period (days) change of the drying shrinkage strain of the test pieces corresponding to the experiment numbers 2, 5, 8, and 11. Only experiment number 2 gave satisfactory results.

By combining the results, in Experimental Examples 1 to 3 in which the fine fraction was 3 to 12% by mass of andesite, good results were obtained for both bleeding and drying shrinkage. On the other hand, in the experimental example in which the coarse fraction was andesite, the fine fraction was either andesite or limestone, and in bleeding, the dry shrinkage was large and satisfactory results were obtained even in the experimental example with good results. There wasn't.

In particular, the method for producing mortar and concrete according to the present invention solves the problem of dimensional accuracy of limestone aggregate, which has been particularly dry shrinkage, and mainly uses limestone produced by wet production, which was supposed to cause bleeding. By using the fine aggregate, mortar and concrete having reduced bleeding can be produced. It becomes possible to easily manufacture mortar and concrete having high durability that effectively avoids settling cracks due to bleeding.

Claims (3)

Particle size of 0.075 mm particle size (hereinafter referred to as fine particle content), the amount of fine particle component containing limestone is less than 1.0% by mass and does not react with Portland cement, SiO ₂ component The amount of fine particles of one or more minerals selected from andesite, basalt and sandstone is 3 to 12% by mass and does not pass through a sieve having a particle size of 0.075 mm (hereinafter referred to as coarse particles). Min) is a fine aggregate for mortar or concrete characterized by being limestone. The fine aggregate according to claim 1, wherein the amount of fine particles is 3 to 9% by mass. A method for producing mortar or concrete using fine aggregate,
After roughly crushing the limestone ore and further crushing it, the amount of fine limestone particles with a particle size of 0.075 mm or less is made into limestone particles less than 1.0% by mass with water washing, sieving, or chickenpox. ,
Separately prepared mineral powder of one or more rock types selected from andesite, basalt and sandstone containing SiO ₂ component is prepared to a particle size of 0.075 mm or less and mixed with the limestone particles. A method for producing mortar or concrete, characterized in that a fine aggregate having a fine particle content of 3 to 12% by mass is used as mortar or concrete.