JPH069258A - Superhigh-fluidity concrete - Google Patents

Abstract

PURPOSE:To prevent separation of the materials, retardation of setting time and reduction of initial strength by using a water-treated cement holding a prescribed amount of water, water-reducing admixture and thickening admixture as the materials for the cement. CONSTITUTION:The objective superhigh fluidity concrete is comprised of a water-treated cement, a water-reducing admixture, for example, AE water- reducing admixture, a thickening admixture such as hydroxyethyl cellulose, polyacrylamide polymer. The water-treated cement is adjusted in its moisture content to 0.1 to 2-wt.%, by spraying the cement with water or steaming it, as it is stirred at a high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compaction-free ultra-high fluidity concrete used in the field of civil engineering, construction, etc. and in the production of various concrete secondary products. Self-leveling material,
It can also be used for prepact concrete mortar.

[0002]

2. Description of the Related Art Conventionally, concrete has played an important role as a basic material for the construction industry. However,
Recently, efforts have been made to reduce the labor of concrete work due to measures such as the reflection of some concrete quality deterioration and the shortage of workers in related industries such as the construction industry expected in the near future. It was

As a result, the slump flow value (JIS A
After carrying out a slump test according to 1108 “Slump Test Method”, the concrete sample shows ultra-high fluidity with an average value of the maximum diameter of the spread of the concrete sample and the diameter orthogonal thereto, which is about 500 to 800 mm, and compaction-free concrete. (Less than,
Ultra-high fluidity concrete) has been developed and gradually put into practical use.

[0004] That is, it is a super-high-fluidity concrete which uses a cement, blast furnace slag, and fly ash in an appropriate ratio to set a hydraulic binder, a water-reducing agent, and a thickening admixture as a raw material for concrete. .

On the other hand, in order to improve the fluidity of concrete, 0.1 to 10% by weight of water is preliminarily held in the cement to reduce the water content of the hydraulic binder obtained by partially hydrating C ₃ A in the cement. A method of using as a raw material for concrete together with an agent (Japanese Patent Laid-Open No. 62-162506) has already been disclosed.

[0006]

However, in the former ultra-high fluidity concrete, the blast furnace slag and fly ash, which have a relatively slow initial reaction, are combined with cement in order to enhance the fluidity, so that the setting time is significantly delayed. At the same time, the expression of initial strength is small. For this reason, in the case of general on-site curing such as covering with a sheet after placing it using this concrete, it is necessary to extend the period of time for which the formwork is to be used. In the case of steam curing, sufficient strength cannot be obtained unless the pre-treatment period is long.

On the other hand, with the latter method, it is not possible to obtain good super-high fluidity concrete. That is, when the fluidity is increased to a slump flow value of about 500 to 800 mm, the material separation of concrete becomes remarkable.

[0008]

The present inventors have developed an ultra-high fluidity concrete which does not cause delay in setting time and reduction in initial strength even when the slump flow value is about 500 to 800 mm, and does not cause material separation of concrete. As a result of seeking and researching, the present invention has been completed.

[0009] That is, the gist of the present invention is that an ultra-high-quality cement prepared by using a hydrolyzed cement, which has previously held 0.1 to 2.0% by weight of water, a water reducing agent, and a thickening admixture as a raw material for concrete. Located in fluid concrete.

Water addition to the cement is carried out by spraying water or spraying water vapor on the cement while stirring the cement at a high speed so that the surface of the cement particles is watered as uniformly as possible.

The water content is 0.1 to 2.0% by weight, preferably 0.5 to 1.0% by weight. 0.1% by weight
If the amount is less than the above, the effect of water treatment is small, and the fluidity of concrete is not improved so much. Also, 2.0% by weight
If it exceeds, the thickening admixture material is trapped in the cement paste and the suppression of material separation of the thickening admixture material is reduced.

Examples of the water reducing agent include a water reducing agent, an AE water reducing agent, a high performance water reducing agent, a high performance AE water reducing agent and a fluidizing agent which are generally used in concrete production.

Examples of the thickening admixture materials include cellulose-based materials such as hydroxyethyl cellulose, hydroxymethyl cellulose and hydroxypropylmethyl cellulose, and acrylic materials such as polyacrylamide polymer. Generally, thickeners and non-separable admixtures in water. , Water retention agents, separation reducing agents, etc.

The admixture amount of the water reducing agent and the viscosity increasing admixture material differs depending on the water addition ratio of the water-treated cement and the mixing ratio of the raw material for concrete, so that the desired fluidity of the concrete and the material separation inhibiting property can be obtained. Set in advance.

The super-high-fluidity concrete may be kneaded by an ordinary concrete kneading method, but in order to further disperse a small amount of the thickening admixture material and to effectively exert the effect of the water-reducing agent, the water-treated cement is used. It is preferable to knead the thickening admixture and the aggregate in advance, and then add the water reducing agent and water and knead.

[0016]

[Example] Ordinary cement (manufactured by Nippon Cement Co., Ltd.), hydrolyzed cement (prototype) in which water is held in ordinary cement at various ratios, ratio of three-component cement <ordinary cement ment 30, blast furnace slag 50, and fly ash 20 Sample product>, Rheobuild NL-4000 (Nisso Master Builders) as the water reducing agent, and Asano HF (manufactured by Nippon Cement Co., Ltd.) as the thickening admixture material, to prepare concrete with the composition shown in Table 1.

[0017]

[Table 1]

With respect to these concretes, slump and slump flow were conducted as a fluidity test, and a difference in unit coarse aggregate amount between the central portion and the peripheral portion and a breathing amount, a coagulation test and a strength test were conducted as a material separation property test. These test methods are as follows.

The slump test is based on the JIS A 1101 slump test method.

For the slump flow value, after the slump test, the maximum diameter of the spread of the concrete and the diameter orthogonal thereto are measured, and the average value is obtained.

After the slump flow test, immediately after the slump flow test, a radius of 10 cm from the center of the flow concrete was used as the boundary, and 2 l of each of the concrete in the center and the peripheral portion were sampled, and the difference was 5 mm. The coarse aggregate is collected by washing with water on a sieve, and the weight of the surface dry saturated state is weighed to obtain the difference between the two.

The Breath sig test is based on JIS A 112.
3 Follow the breathing test method.

The setting test is based on ASTM C 403-65.
According to the T-Proctor penetration resistance method.

In the strength test, a specimen for a compression strength test having a diameter of 10 cm and a height of 20 cm is molded in accordance with JIS A 1132, and is aged at 20 ° C. in water to a predetermined material age.
Perform according to A1108.

The results of these tests are shown in Table 2.

[0026]

[Table 2]

[0027]

The super-high-fluidity concrete of the present invention does not cause material separation even when the slump flow is about 500 to 800 mm, does not extend the setting time, and has high initial strength.

Claims (1)

[Claims] 1. A raw material for concrete, which is preliminarily set to 0.
Hydrolyzed cement holding 1 to 2.0% by weight of water,
Super high fluidity concrete made with water reducing agent and thickening admixture.