JPS6144828B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to non-air entraining cement admixtures. In more detail, it is suitable for cement mortar or concrete pouring construction and molding of secondary concrete products, improves workability, significantly reduces cement mixing water, and further improves cement mortar or cement strength after hardening. This invention relates to a non-air-entraining cement admixture that can significantly improve the water-reducing effect. As is well known, hydraulic cement compositions, which are typified by various cement or concrete products including buildings, are obtained by kneading cement, sand, gravel, etc. with water and molding the mixture. The properties of the hydraulic cement mixture obtained at this time naturally depend on the quality of the raw materials, but also on the mixing conditions. It is well known that one of the most important mixing conditions for obtaining a satisfactory hydraulic cement mixture is to knead the raw materials with as little unit water as possible. It is possible to obtain a product with excellent economic efficiency due to the reduction in quantity. This water reduction mechanism uses a cement dispersant that uniformly disperses the cement particles themselves as primary particles, improves the fluidity of the cement paste, and, as a result, reduces the amount of water required to obtain the same fluidity. It also uses an AE agent (air entrainment agent) that entrains fine closed cells into mortar, concrete, etc., gives fluidity through the bearing effect of the cells, improves workability, and reduces water volume. There is. However, the water reduction effect of AE agents depends on the amount of air entrained, and in order to increase the water reduction effect, the amount of air entrained must increase, resulting in a significant decrease in strength, so there is a limit to the reduction effect of AE agents. Therefore, in order to obtain high-strength cement mortar and concrete products, it is necessary to have a high water reduction effect.
Moreover, there is a strong demand for non-air entraining admixtures (water reducing agents). Secondary concrete products include centrifugal molding of concrete poles, piles or humid pipes, and U.
Cast molded products such as grooves, blocks, greenstone or box culverts (vibrator molded products)
There is. Several water reducing agents have been put into practical use in the molding of these secondary products. These include lignin sulfonates, melamine-formalin resin sulfonates, hydroxycarboxylate salts, alkylated neutral oil sulfonates, β-naphthalenesulfonic acid formalin condensate salts, and the like. However, all of these have advantages and disadvantages, and are not yet satisfactory in all respects. For example, lignin sulfonates and alkyl sulfonates of neutral oils have a weak water-reducing effect, and when added in large quantities to compensate for this, not only are they less economical, but they also exhibit a setting retardation effect, and moreover, the amount of entrained air increases. It causes a decrease in the strength of cement mortar and concrete. Although hydroxycarboxylic acid salts have low air entrainment properties, they have a weak water-reducing effect, and increasing the amount added causes significant retardation of setting, resulting in poor curing in some cases. Similarly, melamine formalin resin sulfonate has a weak water-reducing effect, requires addition of a large amount, and is economically disadvantageous. β-Naphthalenesulfonic acid formalin high condensate salt has excellent performance as a cement dispersant, is effective as a water reducing agent, has low setting retardation, and has low air entrainment properties, making it particularly suitable for secondary concrete products. It is reported that it is a concrete admixture (Tokukosho
41-11737 and Special Publication No. 48-9564). However, β-naphthalenesulfonic acid formalin condensate salt actually entrains a large amount of air and has a large air bubble diameter, so the above-mentioned secondary concrete products, especially vibrator molded products, are difficult to beat after demolding. This results in pinholes or pockmarks that require repair after molding, which is disadvantageous in terms of workability and economy. In view of these circumstances, it is an object of the present invention to provide a cement admixture that does not have the above-mentioned drawbacks, is non-air entraining, and has high water-reducing performance. According to the present invention, the sulfonation rate is between 105 and 135.
Non-air entraining cement containing alkali metal salts, alkaline earth metal salts, ammonium salts or organic amine salts of formaldehyde condensates of sulfonates of naphthalene and mixtures containing not more than 30 mol % of alkylnaphthalenes in the range of % An admixture is provided. The salt of the formaldehyde condensate of sulfonic acid is obtained by sulfonating a mixture of naphthalene and alkylnaphthalene with an alkylnaphthalene content of 30 mol% or less to a sulfonation rate of 105 to 135%, condensing the sulfonated product with formaldehyde, and then neutralizing it. It can be manufactured by Examples of the alkylnaphthalene to be mixed with naphthalene include methylnaphthalene, ethylnaphthalene, butylnaphthalene, dimethylnaphthalene, and mixtures thereof. These alkylnaphthalenes can be mixed with naphthalene in a molar ratio of 0.3 to 0.7 or less. If the mixing ratio of alkylnaphthalene increases more than this, the water reduction performance will decrease. Sulfonation is carried out by a conventional method using concentrated sulfuric acid, fuming sulfuric acid, chlorosulmonic acid, etc. as a sulfonating agent. At that time, the sulfonation rate is 105 to 135.
%, preferably in the range of 110 to 130%, is an essential requirement for the cement admixture of the present invention. When the sulfonation rate is less than 105%, the amount of air entrained is large, which not only deteriorates the hardness of cement mortar and concrete products and impairs their appearance, but also causes a decrease in strength and poor water reduction performance. Sulfonation rate 135%
If this is the case, the amount of air entrained will be reduced, but the fluidity of cement mortar and concrete will be extremely poor, making them unsuitable as water reducing agents. Here, the sulfonation rate is based on the amount of sulfuric acid that is sufficient to convert the mixture of naphthalene and alkylnaphthalene used into monosulfonic acid, and is the actual consumption amount determined by neutralization titration against this amount. It refers to the proportion of the amount of sulfuric acid added. Therefore, by-products such as disulfonic acid, disulfonated naphthylsulfone, and trisulfonic acid are naturally generated. Sulfonation can be achieved under the conditions for producing β-naphthylsulfonic acid, but it becomes necessary to increase the amount of sulfonating agent such as sulfuric acid in order to increase the sulfonation rate to the above range. Next, in the formaldehyde condensation reaction, the highly sulfonated product obtained above is diluted with water, formaldehyde is added under sulfuric acid acidity, and condensation is carried out in a conventional manner. The resulting condensate is neutralized with alkali hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, ammonia, and amines such as alkanolamines to form the respective salts. I'm struggling. The cement admixture of the present invention significantly improves and improves the fluidity of cement mortar and concrete, and as a result, when obtaining the same fluidity, the amount of water per unit is significantly reduced, the amount of air entrained is extremely small, and the strength is significantly increased. increase Furthermore, the cement admixture of the present invention entrains much less air than the formalin high condensate salt of β-naphthalenesulfonic acid, which is conventionally known as a non-air-entraining water-reducing agent. There is no increase in air entrainment and no decrease in strength is observed. Furthermore, the cement admixture of the present invention does not retard the setting of cement mortar and concrete.
It was confirmed that this admixture does not cause accidents such as poor curing even when added in an excessive amount, has a small amount of bleeding, and has little slump loss, which is a drawback of conventional admixtures. Salts of sulfonated formalin condensates of mixtures of naphthalene and methylnaphthalene in a weight ratio of 80:20 to 20:80 are known as air-entraining water reducers (see Japanese Patent Publication No. 14255/1983). However, as a result of advanced sulfonation, the admixture of the present invention has a more hydrophilic balance between hydrophobicity and hydrophilicity, has less surface activity, has less foaming properties, and is a non-air-entraining water-reducing agent. It was found that Since the cement admixture of the present invention has an extremely large water-reducing effect, it usually has a water-reducing effect of 0.1 to 3
Sufficient fluidity can be imparted by a blending amount of 0.3 to 1.2% by weight, preferably 0.3 to 1.2% by weight. Further, if desired, it may be used in combination with a curing accelerator, retarder, anti-shrinkage agent, swelling agent, rust preventive, etc. The admixture of the present invention is usually mixed with cement and aggregates such as sand and gravel, and added when mixing and adding water, but it may also be added by other methods, for example, after mixing mortar or conquerite. ,
Furthermore, it is also possible to use a method in which the admixture of the present invention is made into a dry powder and mixed into cement in advance. Furthermore, the method of applying mortar or concrete containing the admixture of the present invention and the method of molding the secondary product may be the same as conventional methods, and may include painting by troweling, spraying, filling into formwork, etc. can. The curing method may be the same as the conventional method, and air dry curing, water curing, autoclave curing, and combinations thereof can be used. Next, the present invention will be explained in detail with reference to Examples. In the examples, "parts" and "%" are by weight. Example 1 98% sulfuric acid was added to a mixture of 0.8 mol of naphthalene and 0.2 mol of methylnaphthalene at 1.45 mol (composition of the present invention), 1.53 mol (composition XI), 1.6 mol (composition XII), and 1.7 mol (composition ), 1.85 mol (composition), and 1.9 mol (composition), and as comparative examples, 1.15 mol (comparative example F), 1.3 mol (comparative example G), and 2 mol (comparative example H) of 98% sulfuric acid were used. , was sulfonated by a conventional method. After adding water to the resulting sulfonated product, 37% formalin was added under sulfuric acid acidity.
After dropping 0.86 mol, a condensation reaction was carried out, neutralized with calcium hydroxide, cooled, and by-product limestone was filtered off to obtain compositions each having a solid content of 40%. However, since Comparative Example Composition H had a high viscosity, the solid content was set at 34%. Table 1 shows the sulfonation rate, mortar air layer, and mortar consistency (J-Roth value) of the resulting composition.

【table】

[Table] As is clear from Table 1, Comparative Examples F and G correspond to the admixture of the present invention or the salt of ordinary β-naphthalenesulfonic acid formalin condensate.
In comparison, the amount of air is extremely small, providing sufficient fluidity, and there is little decline in fluidity over time. The compressive strength is approximately 20-30% higher after 7 days and 15-25% higher after 28 days. Comparative Example H had a low air content and no problem with compressive strength, but had no fluidity at all.
It was confirmed that it is unsuitable as an admixture for mortar (water reducing agent). Example 2 1.55 mol of 98% sulfuric acid (composition of the present invention) was added to a mixture of 0.7 mol of naphthalene, 0.24 mol of methylnaphthalene, and 0.06 mol of dimethylnaphthalene.
Sulfonation was carried out according to Example 1 using 1.65 mol (composition) and 1.85 mol (composition). As a comparative example, sulfonation was performed in the same manner using 1.28 mol (Comparative Example 1) and 2.2 mol (Comparative Example J) of 98% sulfuric acid, and 0.96 mol of 37% formalin was added dropwise to the obtained sulfonated product under acidic sulfuric acid. , a condensation reaction was carried out. Neutralize the condensation product with 48% caustic soda,
After cooling, by-product sodium sulfate was removed by filtration to obtain compositions each having a solid content of 43%. However, Comparative Example J had a high viscosity and poor workability, so the solid content was 30.
%. The sulfonation rate of the obtained composition is shown in Table 2, and the concrete formulation and test results are shown in Table 3, as well as the results of comparison with conventional commercially available admixtures (water reducers). Table 2 Admixture sulfonation rate (%) Invention 112.6 〃 116.8 〃 127.9 Comparative example I 100.3 〃 J 143.1

[Table] As is clear from Table 3, the amount of air is smaller than that of the admixture of the present invention or Comparative Example Composition I, and the compressive strength is also improved.
Comparative Example J has the same amount of air as the admixture of the present invention, but has extremely small slump and is greatly inferior in water reducing properties. Both commercially available products (1) and (2) are inferior to the admixture of the present invention in terms of water-reducing properties and strength. Example 3 The admixture of the present invention obtained in Example 2 and Comparative Example I were tested for the amount of addition, amount of air, and change in slump over time. The results are shown in Table 4.

【table】

[Table] As is clear from Table 4, it is clear that the admixture of the present invention has less variation in air amount depending on the amount added and less slump loss than Comparative Example I.

Claims (1)

[Claims] 1. Alkali metal salt, alkaline earth metal salt, ammonium salt or organic amine salt of a formaldehyde condensate of a sulfonated mixture containing naphthalene and 30 mol% or less of alkylnaphthalene, with a sulfonation rate in the range of 105 to 135%. A non-air entraining cement admixture characterized by containing.