JPS60239350A - Manufacture of high resistance concrete products - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing concrete products having high resistance, particularly to salt damage and freeze-thaw resistance.

[Conventional technology]

In order to make concrete products, such as concrete bridge girders, resistant to damage caused by freezing and thawing that occurs in winter,
Recently, it has become common practice to add air entraining agents to concrete materials.

However, while salt damage has become a major problem, countermeasures have been limited to temporary measures such as coating concrete or steel materials.

[Problem that the invention seeks to solve]

The method of adding the air entraining agent mentioned above is to create countless insulating air layers in the concrete to prevent freezing inside the concrete product.The use of the air entraining agent is to maintain the strength of the concrete. In addition, the coating material (e.g. vinyl) on the concrete surface or the steel used is easily scratched when handling the product (and once scratched, it is less effective against salt damage). Salt water penetrated and was retained between the coating material and the concrete surface, which actually exacerbated salt damage.

[Means for solving problems]

The present invention aims to solve the above-mentioned problems and provide a manufacturing method for producing concrete products that have high freeze-thaw resistance as well as countermeasures against salt damage. When mixing concrete with a cement ratio of 45% or less, add silica fume of 3% or more of the cement and a dispersant of 6% or less of the cement, mix with a mixer for 3 to 5 minutes, and pour this into the specified formwork. The gist is to mold, and after demolding, steam or autoclave curing is performed.

An example of the above concrete formulation is shown in Table 1.

First, the type of cement is not particularly limited, but ordinary cement, early strength cement, and sulfate-resistant cement are mainly used, and the water-cement ratio is 6% or less, preferably 35% or less.

Silica fume is an ultrafine particle with a particle size of about 0.1 micron that is produced as a byproduct in the main process of ferrosilicon, metal silicon, etc. "Silica fume", "silica dust"
An example of the chemical composition of a commercially available product (MICROPO2) is shown in Table 2.

Table 2 In the present invention, the above-mentioned silica hume is added to the concrete mixture in an amount of 3% or more (externally divided) of the cement, preferably about 5 to 10%, but according to research, if it is less than 3%, the concrete strength increases and the density of the structure increases. The centrality is not enough (, again 1
Although it may be added in an amount exceeding 0%, it is not economical.

The dispersant is preferably a high-performance water reducing agent that is an excellent dispersant based on alkylaryl sulfonic acid, and commercially available products are available under the trade name "Mighty 150". The amount of this addition is ultimately determined depending on workability, but it should be less than 6% (external) of the cement.
Specifically, α2 to 6% (same as above) is dissolved in water and used by adding it to the concrete mixture.

Mixing (for example, coarse aggregate, sand, etc.)
Silica hume and cement are fed into a mixer in this order, and the above "Mighty 150" dissolved in water is finally added and kneaded for 3 to 5 minutes.

Concrete can be placed and shaped using the usual vibration compaction method, and demolding can be done in the same way as usual.

Although steam curing is not necessarily required for curing, it is economical to carry out steam curing at a temperature of 35°C to 80°C at the factory's discretion.

However, steam curing at 8-100℃ or 120℃, 2k
Autoclave curing on the order of "g/cm" is also possible.

[Action of the invention]

In the concrete product according to the method of the present invention as described above, the silica hume is coated with highly active pozzolan,
In addition, the ultrafine particles combine with cement and dispersant to fill the pores between cement or aggregate, creating a dense concrete structure that could not be obtained conventionally.
700-900kg/c exceeding the concrete strength of S
It has a strength of +s and also exhibits strong resistance to water penetration and punching.

In addition, it is possible to introduce prestress into uninvented concrete products in the same way as before, or with the aforementioned improvement in the performance of concrete itself, it has become possible to introduce prestress that is dramatically higher, for example, 200 kg/c- or more, It is possible to manufacture concrete products with excellent bending performance, and since it has a rigid structure, the elastic modulus is increased by 30 to 60%, and stress loss due to elastic deformation is reduced, so it is even easier to introduce high prestress. It will be advantageous.

〔Example〕

In order to obtain a prismatic concrete test piece of 7.5 units x 7,5 units x 40 CIII, the unit cement amount was 400 kg/
mj water cement ratio 33%, slump 411CWI (sand 5
56 kg/m' 1 coarse aggregate 835 kg/m') Addition amount of silica hume (external division of cement) 0, 3,
6. A mixture of 10% tetrapoles (however, for 0%, an air entraining agent (product name "Mighty 300AJ") was used and the air raid amount was 5%) was mixed in a mixer and molded into the specified formwork. After concrete casting, vibration compaction, and demolding as usual,
Steam curing was carried out at a temperature increase of 20°C/hour at a maximum of 80°C for a holding time of 4 hours, and then allowed to cool naturally.

The test method is ASTM C666 in-air freeze-thaw test method (
Method B), 7 Antho 7 (Vary
'tHoff ) (N for D artificial seawater, i.e. water 1!
acA 27g, Kc 40.7g, Cac also 1
8% MgC42' 3.4g, NaHCO35
g, Mg 50.12g frM A, served as a side dish for resistance to salt damage at the same time as freezing and thawing.

The results are shown in Table 3. As is clear from Table 3 above, specimens 2 to 4 with silica hume addition rates of 3 to 10% according to the present invention had a higher freeze-thaw frequency than specimens without additives. The number of cycles shown is 300
The relative dynamic elastic modulus remained at 80% or more compared to before the test (100%), which is a guideline for resistance. It also shows that it has sufficient resistance.

〔Effect of the invention〕

(1) High f due to the addition of silica hume! Since the material has a high temperature, it prevents water from entering the product, thereby preventing damage to concrete bridge girders and the like due to freezing or salt damage.

(2) A product with a concrete strength of 500 kg/c- or more can be easily obtained by adding silica hume and performing simple curing. Conversely, reducing the strength of concrete allows the use of lower-quality aggregates, which helps conserve resources and reduce costs.

(9) If only steam curing is performed as curing, expensive and large-scale equipment is not particularly necessary.

(4) By increasing the strength of concrete, it is possible to introduce high stress and bending strength can be dramatically increased.

Patent Applicant Maeda Seikan Co., Ltd. Agent Patent Attorney Takeshi Yoneya 1 Procedural Amendment 1, Indication of Case Patent Application No. 93029 filed in 1982 2, Title of Invention Method for Manufacturing Highly Resistant Concrete Streptomyces 3, Amendment Relationship with the case of the person who filed the patent application Patent Applicant Address Name Maeda Seikan Co., Ltd. 4, Agent (1) Page 1 of the specification, “2. Scope of Patent and fF Claims □” is amended as follows.

Note 1: While distributing concrete with a water-cement ratio of 45% or less by mixing appropriate amounts of cement, sand, and coarse aggregate, add silica hume of 3% or more and a dispersant of 6% or less of the cement and mix it with a mixer. A method for manufacturing a highly resistant concrete product, which comprises mixing the concrete for 3 to 5 minutes, pouring it into a predetermined formwork, shaping it, and curing it.

2. A method for manufacturing a highly resistant concrete product as set forth in claim 1, which is characterized by performing steam curing after demolding. 3. Shaft circumference of claim 1, which is characterized by performing autoclave curing after demolding゛A method for producing a highly resistant concrete product according to item 1.

(21, No. 2, Letter 1, line 13, “Concrete…” to line 1, line 15, “Can you make it with…?” are deleted and the following is added.

This method is intended to prevent damage caused by freezing and thawing inside concrete products by forming countless closed cells in concrete to absorb expansion pressure during freezing. ``I am strong enough to forgive...'' and amend it to ``I am strong enough to not forgive...''.

(4) Page 7, line 6 “Slump 411CIIIJ”
Correct the slump to 4±icmJ.

(Ts., page 7, line 15, ``Frozen in the air...'' is corrected to ``Freeze in the water...'')

(6) "According to Law F (Law B)," in Line 16 of the 7th City, is corrected to "According to Law (Law A)."

that's all

Claims (1)

[Claims] 1. During the placement of concrete with a water-cement ratio of 45% or less, which is a mixture of cement, sand, and coarse aggregate, 3% or more of silica hume and 6% or less of a dispersant are added to the cement. A method for producing a commercial concrete product, which comprises adding and kneading the mixture for 3 to 5 minutes in a mixer, casting and shaping it in a predetermined form, and curing after demolding. 2. A method for molding a highly resistant concrete product according to claim 1, which comprises performing evaporation percentage curing after demolding. 3. The method for producing a highly resistant concrete product according to claim 1, which comprises performing autoclave curing after demolding.