JPS61151074A - Improvement of operating lightweight concrete - 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 (Industrial Field of Application) The present invention relates to a method for improving the workability of lightweight concrete, particularly the pumpability. For more details,
In order to improve the pumping performance of lightweight concrete and the separation of lightweight aggregates, high-substituted hydroxyethyl cellulose with a molar substitution degree of 3.0 to 10.0 is added when mixing lightweight concrete. It is characterized by this.

(Prior art) Recently, light-duty concrete, which is made lighter by using coarse lightweight aggregate instead of the coarse aggregate used in concrete IJ-to, has rapidly become popular for use in the floors of high-rise buildings, especially condominium floors. ing. This is because lightweight concrete is about 40% lighter than concrete, which reduces the load on the building frame, and also has a thermal conductivity of about 25%, so it has excellent insulation properties. Therefore, in general, the pumpability of lightweight concrete is better when the slump is a dog and the separability of the lightweight aggregate is small, but if the slump is a dog, the separability of the lightweight aggregate increases, and conversely, the lightweight concrete becomes easier to pump. If the separability of the material is reduced, the slump will be reduced. A method that attempts to satisfy both requires a mixture with a large amount of cement, but this not only causes an economic disadvantage, but also increases the tendency for cracks to occur due to the shrinkage of the hardened lightweight concrete. This is an unsophisticated method.

(Problems to be Solved by the Invention) Lightweight concrete IJ-type construction is generally carried out by pump construction. In pump construction, in addition to the problems associated with concrete component construction, there are also problems that occur when constructing lightweight concrete. The main ones include (a) blockage in the pumping pipe during pumping, (b) pumping capacity, and separation of lightweight aggregates during or after pumping.

Regarding (a) above, blockage accidents are serious accidents that often occur during pump construction. Once this occurs, a large amount of labor and time is required for cleaning the gate and other tasks, and the original purpose of the pump replacement, which is to save labor for the painter, is lost. In addition, if the accident treatment takes too long, the remaining light concrete will begin to harden and will eventually have to be discarded, resulting in an economic disadvantage.

This blockage is caused by lightweight concrete IJ with high separability of lightweight aggregate.
- This is easy to occur. In order to reduce the separability of lightweight aggregates, it is necessary to mix the amount of cement to a certain level, but as mentioned above, this is not preferable. There is also a method of adding cellulose ether, but there are problems as described below.

Regarding (b) above, buildings are getting taller these days,
Pumps are usually fixed on the ground and transported to upper floors for construction, so it is important for construction that the pump has a large pumping capacity. For this purpose, it is preferable to use a lightweight concrete with a composition that reduces the pumping resistance of the lightweight concrete.For this reason, a large kina lightweight concrete with a high slump is used as much as possible, but there is a problem that the separation of the lightweight aggregate becomes large, so a satisfactory composition is required. The current situation is that we are not getting anything.

Regarding 0→ above, this is a problem that occurs because the specific gravity of lightweight aggregate is lighter than other concrete components.

In particular, this phenomenon tends to occur when the amount of water in lightweight concrete is increased to reduce slump in order to improve the pumping capacity, or when the amount of cement is decreased for economic reasons to reduce the viscosity of lightweight coscrete. be. If the lightweight aggregates separate, not only is the problem (a) likely to occur, but the lightweight concrete placed on the floor needs to be mixed again, resulting in operational disadvantages.

To solve the above problems, attempts have been made to add cellulose ether, which is generally well known as a cement mortar admixture. Adding cellulose ether has the effect of reducing the viscosity of lightweight concrete and preventing separation of lightweight aggregates. However, the increase in viscosity, on the other hand, causes a problem of lowering the pumping capacity, and at present, neither the addition of cellulose ether nor the necessary VL has a sufficient effect.

(Means for Solving the Problems) As a result of examining tax considerations in order to solve the above-mentioned problems in the construction of light pump concrete, especially in the construction of pumps, the present inventors found that The present inventors have discovered that the above-mentioned problems can be greatly improved by adding Droxyethyl cellulose at the time of mixing lightweight concrete, and have completed the present invention.

That is, the present invention provides lightweight concrete with a molar substitution degree of 3.
Add hydroxyethylcellulose with a diurnal substitution degree of 0 to 10.0 to the cement in proportions of 002 to 03-volume and knead it! This is a method for improving the workability of lightweight concrete, which is characterized by mixing 7.

As mentioned above, highly substituted hydroxyethylcellulose having a molar substitution degree (MS) of 3.0 to 10.0 is suitable as the hydroxyethylcellulose used in the present invention.

When the molar value of hydroxyethyl cellulose is less than 3.0, the effect of imparting viscosity to lightweight concrete is large, and the effect of improving pump workability, particularly pumping capacity, is poor. Furthermore, it is difficult to synthesize hydroxyethylcellulose with a molar substitution degree of 10.0 or more.

The viscosity of the shredded hydroxyethyl cellulose used in the present invention is 100 to 10.0 when reconstituted as a 1% aqueous solution at 25°C.
00 cps0 is appropriate. 1% aqueous solution return 2
If it is less than 100 cps at 5°C, it will not be effective in preventing the separation of lightweight aggregates. Also, 10.000 C9
Those with a number of 8 or more are difficult to synthesize.

The production of such hydroxyethylcellulose is not particularly limited, but known methods can be employed as they are. In general, cellulose and ethylene oxide are reacted in the lower left corner of 1,1-g alkali, and hydroxyethylcellulose having a desired molar W temperature can be obtained by changing the t'c of the alkali and ethylene oxide. Specifically, Special Public Interest Publication No. 37-2
The manufacturing method shown in Japanese Patent No. 199 can be adopted.

The method for preparing lightweight concrete using the hydroxyethyl cellulose of the present invention is to add the hydroxyethyl cellulose of the present invention in a dry state to a mixture consisting of cement, fine aggregate, and lightweight aggregate, and then homogeneously tri-blend the mixture using a mixer. Later, water can be added and mixed to obtain lightweight concrete. It is also possible to adopt a method in which the hydroxyethyl cellulose of the present invention is dispersed in water and added to lightweight concrete prepared in advance.

The cement used here is Portland cement.
white cement, alumina cement, slanogcemen)
RX and various conventionally known hydraulic cements can be used, and as the fine aggregate, sand of 2.5 mm or less can be used. Furthermore, as the lightweight aggregate, pearlite-based artificial lightweight aggregate with a particle size of 2.5 to 15 mm is suitable.

Suitable results can be obtained when the uninvented hydroxyethyl cellulose is added in an amount of 0.05 to 0.2 molar mass to cement. 0.05
% or less, the effect of imparting viscosity to lightweight concrete is small and the effect of preventing separation of lightweight aggregate cannot be obtained. Moreover, if it is 0.24 or more, the effect of imparting viscosity to lightweight concrete is too thick, and pump workability is undesirable, as this results in a decrease in pump pumping capacity.

In addition to the above-mentioned components, in the present invention, admixtures such as dispersants, water reducing agents, air entraining agents, setting regulators, waterproofing agents, etc. commonly used in mortar and concrete may be used without impairing the purpose of the present invention. It is also true that the limit v can be divided by addition.

(@Ming's Effect)' The above invention solves problems in lightweight concrete construction, especially pump construction, by adding a small amount of highly substituted hydroxyethyl cellulose with a molar substitution degree of 3.0 to 10.0. Even in slumps where separation of lightweight aggregates does not occur, the pumping pressure is not limited, and the pumping amount increases, improving the pumping capacity, and the workability of the pump can be greatly improved without causing blockage accidents. . Furthermore, in order to obtain these effects, there is no need to carry out the conventional cement process, and the workability of lightweight concrete IJ-t is economically improved significantly without deteriorating the physical properties of hardened lightweight concrete. It is possible.

(Example) Next, examples will be shown to explain the invention in further detail.

Example 1 700 kg of cement, 2.100 kg of river sand (C'Pi particle diameter of 2.5 mm or less), and 420 kg of water were placed in a raw mixer truck (6-), and cement mortar was prepared first. Hydroxyethylcellulose (1% viscosity Bt400 Cf) with a molar substitution of 1ffi4.0 was added to this cement mortar.
325℃) 700g and lightweight aggregate (manufactured by Toho Perlite Co., Ltd.)
t2007! A pre-triblended mixture was added, and water was further added to prepare lightweight concrete of slump 20. The on-site construction of this concrete was carried out on the 11th floor of a high-rise building in Osaka City (40 m above ground) using a squeeze pump (pipe diameter: 4 inches). As shown in Table 1, good results were obtained in terms of pump workability, with low pumping pressure, large pumping capacity, and no clogging in the pumping pipe or separation of lightweight aggregates.

Actual flow? lI 2-5 Hydroxyethylcellulose (with the molar substitution degree shown in Table 1)
As a result of carrying out the same on-site construction as in Example 1 using a pump with a 1% viscosity of 400 cps at 25°C, it was found that the pumping performance was low, the pumping capacity was large, and there was no blockage in the pumping pipe and separation of lightweight aggregates. Good results were obtained without any problems.

Comparative Example 1 Hydroxyethyl cellulose with the degree of molar substitution shown in Table 1 (
As a result of performing the same on-site construction as in Example 1 using 1% viscosity (400 cps, 25°C), no blockage in the pumping pipe or separation of lightweight aggregate occurred, but the pumping pressure was high and the pumping capacity was low. was small, and good pump workability could not be obtained.

Soft ratio example 2 Hydroxypropyl methylcellulose (1%
Viscosity 200 cps at 25℃)
As a result of carrying out construction work on a similar site, either blockage in the pumping pipe and separation of lightweight aggregates did not occur, or the pumping pressure was high and the pumping capacity was small, making it impossible to obtain good pump workability.

Claims (1)

[Claims] Highly substituted hydroxyethyl cellulose with a molar substitution degree of 3.0 to 10.0 is added to lightweight concrete at a rate of 0.
A method for improving the workability of lightweight concrete, which comprises adding and mixing the mixture at a ratio of 0.02 to 0.3% by weight.