JP2772550B2 - Admixture for RCC - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mixture agent suitable for roller compacted concrete (hereinafter referred to as RCC) used in the construction field of concrete structures such as dams and roads. It is.

[Conventional technology]

RCC is a so-called hardened concrete with a small amount of water, but in this construction, a method of forcibly compacting using a vibrating roller is adopted. After kneading the concrete,
A method of compacting after carrying and unwinding is adopted, and during this time, a time of 1-2 hours elapses depending on the setup of construction. For this reason, the following physical properties are desired for concrete used for this purpose.

 For one thing, compaction is easy.

Second, it is stable over time, and the physical properties of concrete do not change until compaction.

Third, the unit water volume should be as small as possible to lower the W / C and increase the strength.

Although the physical properties of these concretes can be imparted by the use of admixtures, it is only recently that RCC has been put to practical use in Japan. At present, sufficient investigation has not been made on agents.

Therefore, most of the conventional AE water reducing agents are used only for the purpose of reducing W / C, and the admixture for RCC is desired.

[Problems to be solved by the invention]

Since the physical properties of structures depend on their compaction properties, the difficulty of compaction is an important measure for judging the properties of concrete as physical properties.

Generally, the VC value (time (seconds) required for the paste to float on the concrete surface when a constant vibration is applied under a constant load) is used as this scale. However, compaction by a vibration roller is used. Aims to make cement and aggregate adhere tightly and without gaps, and that excess moisture comes up as a paste.Therefore, it is clear that there is a correlation between VC value and on-site compaction. is there. That is, it is desired that concrete having a VC value which is considered to be most easily mechanically worked can be obtained with a minimum amount of water, and that this VC value is stable over time.

From the concept of the VC value, which is the time until the ultimate compaction state in which the concrete is compacted and the gap is no longer at all and excess paste has emerged, the difficulty of compaction work is that the VC value is large or small. It can also be expressed. VC
The magnitude of the value is naturally brought about by the adjustment of the unit water amount. In short, if the unit water amount is increased, concrete with good compaction work can be obtained. However, it is inevitable that the resulting concrete structure has a high W / C, a small unit volume and a low strength.
Therefore, the meaning of concrete with good compaction property is not simply concrete with excellent compaction workability, but also concrete with as large a unit mass as possible and excellent in compaction workability. .

[Means for solving the problem]

The VC value gradually increases with time due to the progress of the hydration reaction of the cement. Since an increase in VC value over time immediately increases the energy of compaction work, for example, prolongs the compaction work time and reduces the compaction layer thickness, it is preferable that the increase over time is as small as possible.

The RCC using a conventional AE water reducing agent has a remarkable increase in the VC value over time, which requires strict compaction work conditions.

The present invention not only provides an admixture having excellent water reducing properties and good compaction properties, but also provides an admixture capable of maintaining the same compaction properties as immediately after kneading over time.

The present inventors have conducted various studies in order to solve these problems, and as a result, as described in JP-B-56-40106, phenyl obtained by oxidizing lignin sulfonate under alkaline conditions. When using as a concrete admixture a modified lignin sulfonate containing 0.20 mol or more of carboxyl groups and 0.10 mol or more of sulfone groups per propane unit as a main component, it has better water-reducing properties than a normal AE water-reducing agent. It has also been found that the aging stability is good and that the same compaction property as immediately after kneading can be maintained for a long time.

[Action]

In the present invention, an admixture comprising a modified lignin sulfonate as a main component containing 0.20 mol or more of carboxyl groups and 0.10 mol or more of sulfone groups in the phenylpropane unit obtained by oxidizing the lignin sulfonate is used. The superior water-reducing properties and the better stability of the VC value over time are higher than those of ordinary AE water-reducing agents, because the modified lignin derivatives have stronger interaction with cement particles and higher dispersibility. It seems to do.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to examples. The materials used for the concrete test are as follows.

Cement: Normal Portland cement (made by Chichibu Cement Co., Ltd.) Specific gravity 3.16 Fly ash: Specific gravity 2.20 Fine aggregate: Crushed sand from Kodama Specific gravity 2.63, FM2.79, MS5mm Coarse aggregate: Crushed stone from Chichibu Specific gravity 2.70, FM7.86, MS80mm Water: Tap water Admixture: Lignin: Delayed type I AE water reducing agent (lignin sulfonate) Modified lignin: Sunflow VH (Sanyo Kokusaku Pulp Co., Ltd.) containing modified lignin sulfonate as a main component Was used at 1% by volume with respect to cement.

The results of the concrete mix and concrete test are shown in the following table.

[Effects of the Invention] As shown in the examples, the admixture of the present invention has better dispersibility than ordinary AE water reducing agents, can reduce the unit water volume, and can provide concrete with excellent strength. In addition, it showed appropriate wettability, gave concrete with compact compaction properties, and showed excellent temporal stability of concrete compaction properties, indicating that it is extremely excellent as an admixture for RCC. I have.

Continued on the front page (72) Inventor Noriharu Moribe 1551 Higashidaira, Higashimatsuyama City, Saitama Prefecture Sanyo Kokusaku Pulp Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 24/18 C04B 24:18 C04B 103: 30 C04B 103: 32

Claims (1)

(57) [Claims] 1. An admixture for RCC comprising as a main component a modified lignin sulfonate having at least 0.20 mol of carboxyl groups and at least 0.10 mol of sulfone groups per phenylpropane unit.