JPH0226856A - Cement admixture - Google Patents

Abstract

PURPOSE:To enhance the initial flowability of a cement blend and to reduce the lowering of the flowability with the lapse of time by incorporating a salt of the condensation product of a specified arom. hydrocarbon with formaldehyde. CONSTITUTION:An arom. hydrocarbon having carboxyl and hydroxyl groups such as salicylic acid is allowed to react with formaldehyde in an aq. sulfuric acid soln. and the resulting condensation product of the arom. hydrocarbon with formaldehyde is neutralized with an alkali (earth) metal, amine or ammonia to obtain a cement admixture which is the alkali (earth) metal, amine or ammonium salt of the condensation product. This admixture is added to cement by 0.01-1.0wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a cement admixture that hardens under the influence of water, in particular for fluidizing cement mixtures such as cement paste, mortar or concrete; Small decrease in fluidity over time (Conventional technology) In order to improve the workability of cement mixtures such as cement paste, mortar, or concrete, it is necessary to have high initial fluidity of the cement mixture and to reduce the decrease in fluidity over time. is required to be small.

It is known that fluidity decreases over time mainly due to hydration reaction between cement and water and physical aggregation between the mixture.

Cement paste, mortar, or concrete, which are cement compounds, suffers from a hydration reaction between cement and water, which causes physical and chemical aggregation of cement particles over time after mixing, resulting in decreased fluidity and poor workability. Efficiency decreases over time. This phenomenon is generally called mortar flow reduction or concrete slump loss, and limits the pot life of the concrete.

In the case of ready-mixed concrete, concrete slump loss causes problems such as limited transportation time, waiting time at the pouring site, quality deterioration due to temporary interruption of pump pressure, and poor workability.

Furthermore, in the case of secondary concrete products, slump loss of concrete causes limitations in molding time and poor centrifugal compaction.

Therefore, cement paste, which is a cement formulation,
Slump loss, the decline in fluidity of mortar or concrete over time, is an important problem to be solved.

<Problems to be Solved by the Invention> For this reason, several methods have been conventionally considered as measures to prevent slump loss in concrete.

(1) Japanese Patent Publication No. 51-15856 describes a concrete admixture selected from conventionally known water-soluble salts of sulfonated aromatic compounds or water-soluble salts of formalin condensates of sulfonated aromatic compounds. A method is disclosed in which fluidity is maintained for a long time by repeatedly adding . Although this method is effective to some extent, it is time-consuming to add, has poor workability, and is also economically disadvantageous.

(2) The method of adding a setting retarder such as oxycarboxylic acid causes a decrease in strength and poor curing. Also, although this method can delay the hydration reaction of cement, it is difficult to prevent physical agglomeration.

(3) JP-A No. 54-139929 discloses that a concrete admixture such as naphthalene sulfonic acid formalin condensate is granulated and added to concrete, etc., and the granular admixture gradually dissolves, resulting in slump loss. A method to prevent this is shown.

Although this method can prevent slump loss to some extent, it is difficult to control the dissolution rate, and if parts remain in the concrete, the strength and durability of the concrete will decrease.

(4) JP-A-57-77061 discloses a method of maintaining fluidity for a long time by using a formalin cocondensate salt consisting of naphthalene sulfonic acid, phenolic sulfonic acid, and aromatic carboxylic acid. However, this method is insufficient in preventing fluidity from decreasing over time.

(5) JP-A No. 60-33240 discloses a method for maintaining fluidity for a long time by using a co-condensate salt of naphthalene sulfonic acid and/or alkylnaphthalene sulfonic acid and a naphthalene conductor containing no carboxyl group. has been disclosed, but this method is insufficient in preventing the fluidity from decreasing over time.

As described above, conventional methods for preventing slump loss cannot be said to be practically sufficient.

The purpose of the present invention is to have high initial fluidity of cement mixtures,
The object of the present invention is to provide a new cement admixture whose fluidity decreases little over time.

Means for Solving the Problems> That is, the present invention provides an alkali metal salt, an alkaline earth metal salt, an ammonium salt, and an amine salt of a formalin condensate of an aromatic hydrocarbon having a carboxyl group and a hydroxyl group. The present invention provides a cement admixture characterized by containing at least one selected type.

The present invention will be explained in detail below.

Examples of aromatic hydrocarbons having a carboxyl group and a hydroxyl group used in the admixture of the present invention include salicylic acid, m-
Examples include hydroxybenzoic acid, p-hydroxybenzoic acid, 2-hydroxy-1-naphthoic acid, and 2-hydroxy-3-naphthoic acid.

Any method may be used to produce the salt of the condensate of the aromatic hydrocarbon and formalin contained in the admixture of the present invention, but for example, salicylic acid and formalin are reacted in an aqueous sulfuric acid solution. It is preferable to obtain a sodium salt of the salicylic acid-formalin condensate by separating the salicylic acid-formalin condensate from an aqueous sulfuric acid solution by filtration or the like, and then neutralizing it with sodium hydroxide.

In the production of the conventionally known naphthalene sulfonic acid formalin condensate, since the naphthalene sulfonic acid formalin condensate dissolves in an aqueous sulfuric acid solution, the liming sodation method is adopted as a method for separating the two, and the sulfuric acid is removed by replacing it with gypsum. has been done. However, with this method, sulfuric acid cannot be reused, and disposal of gypsum is a major problem.

On the other hand, since the salicylic acid-formalin condensate of the present invention does not dissolve in the sulfuric acid aqueous solution, it can be separated from the sulfuric acid aqueous solution by simple operations such as filtration. Therefore, there is no need to dispose of gypsum, which has been a problem in the past, and furthermore, the aqueous sulfuric acid solution after separation of the salicylic acid-formalin condensate can be reused.

The admixture of the present invention can be used alone in cement formulations, or can be used in combination with conventionally known naphthalene sulfonic acid formalin condensate salts, sulfonated melamine formalin condensate salts, lignin sulfonate salts, etc. It may be used in combination with a water reducing agent. The admixture of the present invention is preferably used in an amount of 10 parts or more per 100 parts of the water reducing agent. If it is less than 10 parts, there is no effect of preventing the fluidity from decreasing over time.

The admixture of the present invention is used in an amount of 0.01 to 1.0% by weight based on the cement, but 0.1 to 0.5% by weight is particularly preferred. If the amount added is less than 0.1%, the initial fluidity will be low, and if it exceeds 0.5% by weight, there will be almost no change in performance and only the economical efficiency will deteriorate.

The admixture of the present invention may be added to the mixing water of the cement mixture, or may be added to the cement mixture after it has been kneaded.

The admixture of the present invention includes various cement additives, such as AE agents,
It may be used in combination with an AE water reducing agent, hardening regulator, etc.

<Examples> The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

[Production Example 1] 20.0 g of salicylic acid in 200 g of 30% by weight sulfuric acid aqueous solution
After reacting g and 11.7 g of formalin at 100°C for 3 hours, the resulting salicylic acid formalin condensate was separated from the sulfuric acid aqueous solution by filtration, and further neutralized with sodium hydroxide to obtain the salicylic acid formalin condensate. Sodium salt (A-1) was obtained.

[Production Examples 2 to 4] The admixture (A
-2 to A-4) were adjusted.

[Example 1] A mortar test was conducted using the admixture (A-1) synthesized in Production Example 1 to evaluate fluidity and a decrease in fluidity over time. Table 2 shows the composition of the mortar.

Add water, cement, and an admixture (0.4% by weight to cement in terms of solids) to a cement mixing bowl.
After 0 seconds of mixing, sand was added with mixing for 30 seconds, followed by 60 seconds of mixing. The mixture was allowed to stand for 20 seconds, the mortar adhering to the mixing bee and paddle was scraped off, and then mixed again for 120 seconds.

After filling a mini-slump cone with a height of 15 cm with mortar, the mini-slump cone was removed and the slump was measured to be 10.7 cm.

Furthermore, after allowing the mortar to stand still for 60 minutes, the mortar was mixed for 1 minute and the slump was measured in the same manner and found to be 9.7 cm.

The slump residual rate (%) is calculated from the formula below: 90.7
%Met.

× 100 [Examples 2 to 4] A mortar test was conducted in the same manner as in Example 1 using the admixtures (A-2 to A-4) synthesized in Production Examples 2 to 4. The results are shown in Table 3.

[Example 5] The admixture (A-1) synthesized in Production Example 1 and the naphthalene sulfonic acid-formalin condensate salt were mixed in equal amounts (weight ratio), and a mortar test was conducted in the same manner as in Example 1. The results are shown in Table 3.

[Example 6] The admixture (A-4) synthesized in Production Example 4 and naphthalene sulfonic acid-formalin condensate salt were mixed in equal amounts (weight ratio), and a mortar test was conducted in the same manner as in Example 1. . The results are shown in Table 3.

(Comparative Example 1) A mortar test was conducted in the same manner as in Example 1 using a naphthalene sulfonic acid-formalin condensate salt known as a commercially available cement admixture. The results are shown in Table 3.

[Comparative Example 2] Equal amounts (weight ratio) of sodium salicylate and naphthalene sulfonic acid-formalin condensate salt were mixed, and a mortar test was conducted in the same manner as in Example 1.

The results are shown in Table 3.

<Effects of the Invention> The novel admixture of the present invention has high initial fluidity and shows little change in fluidity over time when used in cement mixtures, so it is useful as an additive to cement mixtures such as ready-mixed concrete.

In addition, compared to the conventionally known naphthalene sulfonic acid-formalin condensate salt, it is economically advantageous because it does not require treatment of waste sulfuric acid during the manufacturing process.

Claims (1)

[Claims] (1) Contains at least one selected from the group consisting of alkali metal salts, alkaline earth metal salts, ammonium salts, and amine salts of formalin condensates of aromatic hydrocarbons having carboxyl groups and hydroxyl groups. Cement admixture.