JPS593429B2 - Production method of ready-mixed concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ready-mixed concrete, and more particularly to an improvement in the method for producing ready-mixed concrete by a delayed addition method of a cement dispersant.

In recent years, the quality of concrete aggregates such as gravel and river sand has deteriorated due to a shortage of concrete aggregates, and the unit water volume has increased due to the workability of concrete, as well as cracks in concrete due to drying shrinkage, water heat generation, etc., and an increase in the amount of breathing. physical properties tend to decrease.

In order to improve these drawbacks, cement dispersants called high performance water reducing agents, such as formalin condensates of β-naphthalene sulfonate and formalin condensates of melamine having a sulfone group, are used.

This has no concrete hardening delay effect or false setting.
Although it is possible to reduce the unit amount of water depending on the amount used and provide good workability, the workability is only for a short period of time and has the disadvantage that it rapidly decreases thereafter.

Therefore, in the case of ready-mixed concrete that needs to be transported by truck agitator, a high-performance water reducing agent is not used at the time of cross-tracking, but the ready-mixed concrete is transported to the pouring site and added to the truck agitator at the pouring site. ing.

However, with this method, since the truck agitator is a concrete transport vehicle and different from a mixer truck, even if the cement dispersant is added to the truck agitator and mixed, the mixing is insufficient, resulting in uneven workability of the concrete. This has the drawback of unstable quality.

Furthermore, in order to achieve sufficient mixing, the drum of the track agitator must be rotated at high speed for several minutes, which poses problems such as noise and durability of the track agitator.

On the other hand, there is a delayed addition method of cement dispersant.

The cement dispersant, which should normally be added at the start of mixing, is added several tens of seconds to several minutes after water is added to improve workability, increase set retardation, and reduce worker buildup over time. This is a method to prevent the decline in

Although this method is superior to the method of adding cement at the beginning of mixing, it does not provide a sufficiently satisfactory effect, and recently it has been proposed to solve the problem by improving cement dispersants. (Tokuko Showa 56-4o1o6
Publication No.).

But even that is not enough. The present invention provides high-quality ready-mixed concrete that has high workability even though the unit amount of water or cement is reduced, and there is no problem with slow curing and decrease in workability even when it is transported to the pouring site. The purpose is to provide the following.

That is, the present invention includes the use of a cement dispersant containing the following components (a), (b), and (C) when producing ready-mixed concrete by the delayed addition method of a cement dispersant. This is a unique method for producing ready-mixed concrete.

A substance whose main component is a lignin sulfonate having a low molecular weight of 2000 or less and a sugar content of 0.8 to 1.3 by weight in terms of pentose Φ) β-naphtha/sulfonate Formalin condensate (c) water-soluble nitrofumate The present invention will be described in more detail below.

First, in the present invention, the reason why the delayed addition method of the cement dispersant was adopted is that even with the cement dispersant according to the present invention as described later, if it is added at the same time as the water used at the beginning of kneading, the workability will be reduced. This is because sufficient improvement cannot be expected or a large amount of addition is required.

Next, the cement dispersant according to the present invention will be explained.

The lead component can be obtained from the lignin sulfonic acid-containing liquid contained in the sulfite pulp waste liquid by various methods.

For example, slaked lime is added to make ligninsulfonic acid an insoluble basic salt, polycations are added to make a complex salt, sugars and low molecular weight substances are extracted and separated using a solvent, and ultrafiltration is used. It can be obtained by

Particularly when ultrafiltration is used, it is advantageous because not only the polymeric lignin sulfonic acid can be recovered individually without using any additives, but also the sugar can be recovered at the same time.

Among the lignin sulfonates obtained by these methods, those used as component (a) according to the present invention have a proportion of low molecular weight substances with a molecular weight of 2000 or less of 10 to 18% by weight, and a sugar content in terms of pentose. The content is 0.8 to 1.3% by weight.

The reason for this limitation is that hydrophilically treated silica gel is used with Yolkel permeation chromatography (GPC).
As a result of conducting various polymerization treatments using geninsulfonate and measuring the molecular weight distribution of geninsulfonate, we also separated the samples, added them to concrete, and conducted tests. As a result, low molecular weight substances with a molecular weight of 2000 or less had low dispersion. In addition, products with a high sugar content may delay curing, resulting in insufficient short-term strength development or causing false setting. This is based on the fact that it is practically impossible to keep the value below the above value, and good results can be obtained in a fresh concrete test if it is within this range.

Component (b) is necessary to recover from the delay in developing concrete strength due to the use of component (a).

The formalin condensate of β-naphthalene sulfonate as the component (b) is not limited to a single condensate, but may include polycyclic aromatic compounds such as naphthalene, alkylnaphthalene, anthracene, benzene, toluene, phenol, benzoate, etc. Formalin cocondensates with benzene derivatives such as acids and their sulfonic acid compounds may also be used.

Component (c) is essential for preventing a decrease in workability that occurs when component (b) is added and over time.

Component (c) is acid decomposed with nitric acid to a low degree to reduce the molecular weight, increase the number of functional groups such as nitro groups, and convert it into a salt such as sodium to make it water-soluble.

In the above, the ratio of components (b) and (c) is a weight ratio of component (a) to component (b) of 90:10 to 10:90, (
It is preferable that the amount of component c) be 2 or less, particularly 0.1 or less, per 1 of the total weight of components (a) and (b).

The reason for this is that if component (a) is less than the above ratio, the workability of concrete with reduced unit water volume or unit cement cannot be improved, and if component (F) is less than the above ratio, the strength This is because the effect of reversing the delay in onset is small, and furthermore, if the content of component (c) exceeds the above-mentioned ratio, dispersibility and fluidity of cement cannot be obtained during concrete mixing.

The amount of the cement dispersant according to the present invention to be used is 0.01 to 1.5 weight percent based on solid content, preferably,
It has a weight ratio of 0.05 to 1.0.

In addition, in the present invention, admixtures normally used in fresh concrete, such as lignin sulfonates, oxycarboxylate salts, natural resinates, fly ash, silica, cement expansion agents, cement rapid hardening agents, etc. There is no problem in adding.

As described above, the present invention produces ready-mixed concrete by a delayed addition method of a special cement dispersant containing three components, and the present invention exhibits the following effects.

In other words, for concrete that has workability comparable to that of ordinary ready-mixed concrete, the unit water content or unit cement content can be reduced to provide superior strength properties, while also reducing workability or curing retardation over time. We can manufacture high-quality products that do not cause any problems.

Hereinafter, the present invention will be explained in more detail with reference to Reference Examples, Examples, and Comparative Examples.

In the following examples, both parts and ratios are expressed on a weight basis.

Reference Example 1 This example is an experiment conducted to confirm the properties of component a.

Fresh concrete batcher - No. 1 in the water measuring tank of the plant.
According to the formulation shown in the table, the following component (a) was added to a mixer together with water and kneaded with other materials to produce ready-mixed concrete.

4.3 m3 of this was transferred to a truck agitator and the physical properties of the concrete were measured (Experiments A, 1, 2) (a) Component: Low molecular weight material with a molecular weight of 2000 or less was 15% by weight, and the sugar content was 1.1 in terms of pentose. A substance whose main component is lignin sulfonate, which has a weight ratio, was used.

In order to examine the properties of the concrete components, a similar test was conducted using a standard amount of an AE water reducer whose main component is lignin sulfonate, which is normally used in fresh concrete (Experiments A3 and 4).
.

In addition, in the experiment, the slump was JISAAllol, the air amount was JISA1128, and the compressive strength was JISA1132.
, according to JISA1108.

(Note) (1) Ordinary Portland cement was used as the cement.

(2) The coarse aggregate used was a mixture of 50 parts of crushed stone and a maximum size of 25 pieces.

(3) Component (a) was added as an aqueous solution and expressed in terms of solid matter.

(4) The AE water reducing agent used was Hozoris & 5 L J, a trade name of Hozoris Bussan.

(Note) The concrete temperature over time was 29-31°C.

From Tables 1 and 2, the GIL) component according to the present invention is a commercially available AE.
Compared to water reducing agents, at the same slump and the same strength composition,
The effect of reducing unit water volume and unit cement volume is obvious;
In addition, slump, changes in air volume over time, and compressive strength were measured using commercially available A
It can be seen that high-quality ready-mixed concrete similar to hard-mixed concrete using only the AE water reducing agent can be obtained, which is the same as when using the E water reducing agent.

Reference Example 2 This example is an experiment to evaluate the performance of a cement dispersant consisting of components (a), (b), and (c) according to the present invention, and the cement dispersant was added together with the water used. It is something.

The composition of the cement dispersant used is as follows.

Composition of cement dispersant [Co., Ltd.] Ingredients; those shown in Reference Example 1...
・50 parts h) Ingredient: Formalin condensate of sodium β-naphthanesulfonate 50 parts (C) Component: Sodium nitrofumate 7.5 parts water ············
250 parts (solid content concentration: 30 parts) That is, in the formulation shown in Table 3, the cement dispersant according to the present invention was put into a fresh concrete batcher plant water measuring tank to produce fresh concrete.

The obtained fresh concrete was transferred to a truck agitator, and the aging change and compressive strength of the concrete were measured (
Experiments A5-7).

In addition, when mixing concrete, natural resinate-based A
The amount of air was adjusted using agent E.

Next, in order to compare the performance of the cement dispersant according to the present invention with a commercially available product, a similar test was conducted using a standard type AE water reducer containing lignin sulfonate as a main component, which is normally used in ready-mixed concrete. (Real axes 8 and 9).

The results are shown in Table 4.

From Tables 3 and 4, concrete using the cement dispersant according to the present invention has a large reduction effect in unit water volume and unit cement volume at the same strength and workability, and in concrete in which only the unit water volume is reduced, ,
It can be seen that concrete with high strength can be obtained.

Reference Example 3 This example uses a cement dispersant according to the present invention as well as a general A
E This was done to confirm that there was no problem with using a water reducing agent or a cement expansion agent, and the cement dispersant shown in Reference Example 2 was used and added at the same time as water was added. be.

That is, concrete was produced and tested in the same manner as in Reference Example 1, except that the concrete mixture was as shown in Table 5 (Experiment 10).

In addition, a test was also conducted in which the cement dispersant according to the present invention was not used (Experiment & 11).

Note that a natural resinate-based AE agent was added to the formulation of Experiment &10 in order to adjust the amount of air.

The results are shown in Table 6.

As is clear from Tables 5 and 6, even in ready-mixed concrete containing a cement expanding agent or a commercially available AE water reducer, the unit water amount and unit cement amount decrease, and the workability and compressive strength are lower than the commercially available AE water reducer. It can be seen that high-quality ready-mixed concrete that is no different from that obtained when using this method is obtained.

EXAMPLE This example illustrates the delayed addition method of cement dispersant according to the present invention.

That is, in the formulation shown in Table 7, except for the cement dispersant used in Reference Example 2, the other ingredients were put into a forced mixing mixer and mixing of ready-mixed concrete was started.

The fresh concrete was continued to be kneaded, and about 20 seconds after water was added, a cement dispersant was added, and the mixture was kneaded for a total of 45 seconds to produce ready-mixed concrete (Experiment A12).

Note that during kneading, a natural resin acid salt-based AE agent was used to adjust the amount of air.

For reference, concrete was produced in the same manner using an AE water-reducing agent whose main component is a commonly used lidanine sulfonate (experiment A13).

Regarding these concretes, the physical properties of the concrete were measured in the same manner as in Reference Example 1.

The results are shown in Table 8.

From Tables 7 and 8, it is clear that the delayed addition of the cement dispersant according to the present invention has the effect of reducing the amount of water per unit and the amount of cement per unit compared to the delayed addition method of commercially available AE water reducers. It can be seen that good ready-mixed concrete can be obtained, with changes in compressive strength and workability over time that are no different from those obtained when a general AE water reducing agent is used.

Furthermore, the method of the present invention has the advantage that the amount used is smaller than the method of adding a cement dispersant when water is added, and fluidity can be improved.

Here's an example.

Comparative Example 1 In this example, when using the cement dispersant according to the present invention, it was added at the same time as water was added.

That is, concrete was produced and tested in the same manner as in Reference Example 1, except that the concrete mixture was as shown in Table 9 (Experiments A14 and 15).

In addition, tests were also conducted in the case where the cement dispersant according to the present invention was not used (Jikken-ya 16 and 17).

Note that a natural resinate-based AE agent was added to the formulations of Experiments A14 and A15 in order to adjust the amount of air.

The results are shown in Table 10.

As is clear from a comparison of Experimental Haruka 12 (Example) and Experimental Ni 15 (Comparative Example), the Example of the present invention can improve workability and strength with a smaller amount of cement dispersant than the Comparative Example. I understand something.

Comparative Example 2 This example uses the cement dispersant according to the comparative example obtained by removing component (c) from the cement dispersant according to the present invention shown in Reference Example 2, and adds it by the delayed addition method to prepare ready-mixed concrete. (Jikken-ya 18).

That is, concrete was manufactured and tested in the same manner as in Example except that the cement dispersant according to the present invention shown in Reference Example 2 except that component (e) was removed was used.

The three concrete mixes and their results are shown in Tables 9 and 1, respectively.
Shown in Table 0.

As is clear from a comparison of Jikken-ya 12 (Example) and Jikken-ni 18 (Comparative Example), the change in sludge over time is significantly smaller in the Example of the present invention than in the Comparative Example.

Table 11 shows experiments A2s 12, 15, 17 and 18.
The results of measuring the setting time of concrete in a 20°G constant temperature room according to ASTM C403-70 are shown below.

Looking at it, when using the cement dispersant to which component [F]) was added, as in the case of concrete in Experiments A12, 15, and 18, the hardening rate was lower than in Experiment A2, in which it was not added. It can be seen that there was no delay and the setting time was approximately the same as when a general AE water reducing agent was used (Experiment A17).

Claims (1)

[Scope of Claims] 1. In producing ready-mixed concrete by the delayed addition method of cement dispersant, a cement dispersant containing the following components (a), (b) and hc) is used. A method for producing ready-mixed concrete characterized by: (a) 10 to 1 low molecular weight substances with a molecular weight of 2000 or less
(b) Formalin condensate of β-naphthalene sulfonate (c) Water-soluble nitrofumin acid salt.