JPH0134943B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for improving the workability of concrete, and particularly to a method for preventing slump loss in concrete to which a high performance water reducing agent is added. Note that in the present invention, concrete is a general term for mortar, concrete, and the like. Various cement dispersants have been known for a long time, but among cement dispersants, we have developed a highly effective dispersant that does not adversely affect the deterioration of concrete, such as delayed setting or air entrainment, even when added in large amounts to cement. Dispersants that can be added, so-called high-performance water reducers, are used in concrete products that require high strength, especially piles, poles,
It is added to and used in the manufacture of concrete factory products such as blocks. However, such concrete has significantly lower flow and slump than that without additives,
There is a drawback that there is not enough working time, especially at low temperatures. The present invention solves these drawbacks and provides a method for preventing a decrease in the flow and slump of concrete, especially by using a small amount of tartaric acid or its salts, or these and sugars in concrete mixed with a high-performance water reducing agent. The purpose is to provide a method for improving workability at low temperatures. That is, the present invention provides 0.005 to 0.3% by weight of tartaric acid or its salts, or these and sugars, based on the cement content of concrete to which a high performance water reducing agent has been added.
It is characterized by adding 0.005 to 0.1% by weight. The present invention will be explained in more detail below. first,
In the present invention, the high performance water reducing agent has the properties described above, and specific examples thereof include naphthalene sulfonic acid formaldehyde co-condensate, naphthalene sulfonic acid and lignin sulfonic acid formaldehyde co-condensate, and melamine formaldehyde condensate. Examples include sulfonated products, and commercially available products include Kao Soap Co., Ltd.'s product names "Mighty 100,""Mighty150," and "Mighty HS," and Takemoto Yusashi Co., Ltd.'s product name "Pole Huain 510N." , Sanyo Kokusaku Pulp Co., Ltd. Product name: "Sunflow PS", Pozolis Bussan Co., Ltd.
Product name "NL-1450""NL-4000", Showa Denko K.K.
There are product names such as ``Melment''. Normally, these high-performance water reducers are added in an amount of about 0.2 to 3% by weight based on the cement content of concrete, but since concrete with high-performance water reducers added has a significant drop in flow and slump, in the present invention By adding 0.005 to 0.3% by weight of tartaric acid or its salts to the cement content of concrete to which such a high-performance water reducer has been added, or by adding 0.005 to 0.1% by weight of sugars in addition to these, , which solves the problems of concrete with added high-performance water reducing agents. Salts of tartaric acid used in the present invention include:
sodium, potassium, lithium, calcium,
Examples include zinc, strontium, copper, and iron. These tartaric acids or their salts, if not used together with a high performance water reducing agent, will actually promote a reduction in flow and slump. Furthermore, in the present invention,
Examples of the saccharide used include polysaccharides such as monosaccharides, disaccharides, and trisaccharides, and one or more of these can be used, but sucrose is most preferred from the viewpoint of performance and economical efficiency. In addition, in concrete with high-performance water reducer added, only sugars are added, and the temperature is low, especially 15℃.
When used at the following temperatures, there is no effect of preventing a decrease in flow or slump; however, if these are used in combination with tartaric acid or its salts, an effect of helping to prevent a decrease in flow or slump appears. In the present invention, the reason why the amount of tartaric acid or its salts added is limited as described above is that if it is less than 0.005% by weight based on the cement content in concrete, the effect of preventing a decrease in flow and slump is small.
This is because if it exceeds 0.3% by weight, the strength development is significantly delayed, and the reason why we limited the amount of sugars used in combination with tartaric acid or its salts is that if it is less than 0.005% based on the cement content in concrete,
It has no effect on reducing flow or slump, and
This is because if it exceeds 0.1% by weight, curing will be significantly delayed, which is not preferable. As explained above, the present invention uses a small amount of tartaric acid or its salts, or a combination of these and sugars for the cement content of concrete using a high performance water reducer. This is an excellent method that prevents deterioration of flow and slump without impairing the properties of the concrete to which it has been added. The present invention will be further explained below with reference to Examples. Example 1 Kao Soap Co., Ltd.'s product name ``Mighty 150'' was used as a high-performance water reducing agent, and the amount added to the cement was
The decrease in mortar flow was measured by fixing the amount at 1.5% by weight and varying the type of tartaric acid or its salts and the amount added to the cement. In addition, mortar is
Ordinary Portland cement and natural river sand with an F.M of 2.95 were mixed at a cement:sand ratio of 1:1.5 and W/C of 30%, and the flow values were measured immediately after mixing and after 2 hours.
Measured at a temperature of 10°C. The results are shown in Table 1 as relative values when the flow value immediately after kneading is set as 100. Table 1 also shows the results of measuring the compressive strength after 7 days using the same mortar. Experiment No. 1 is a comparative example.

【table】

[Table] Table 1 shows that as the amount of tartaric acid or its salts added increases, the flow reduction prevention effect increases, and 7
This shows that the development of strength is delayed during the day, but
At 28 days, the strength was 740 to 750 Kg/cm ² , and it was confirmed that this value was almost the same as that without adding tartaric acid or its salts. Example 2 Tartaric acid was 0.03% by weight based on the cement (however, no additive was used in Experiment Nos. 23, 24, 31, and 36), and the product name "Sunflow PS" was added to the cement as a high performance water reducer. The test was conducted in the same manner as in Example 1, except that the sugar content was fixed at 1.5% by weight and the type of saccharide and the amount added to the cement were varied. The results are shown in Table 2. Experiment Nos. 23 to 25, 31 and 36 are comparative examples.

【table】

[Table] Table 2 shows that as the amount of sugar added increases, the flow reduction prevention effect increases, and the compressive strength at 7 days is delayed, but at 28 days old, the
It was confirmed that it developed a strength of 750Kg/cm ² and that this value was almost the same as that of a product without added sugars. Example 3 The same procedure as in Example 2 was carried out, except that 1.0% by weight of "Melment F10" (trade name, manufactured by Showa Denko KK) was used as a high-performance water reducing agent based on the cement. The result is the third
Shown in the table. Note that Experiment Nos. 41, 42, and 47 are comparative examples in which tartaric acid was not added.

[Table] Table 3 shows that as the amount of sugar added increases, the flow reduction prevention effect increases, and the development of strength at 7 days is delayed;
Kg/cm ² , and it was confirmed that this value was almost the same as that without adding sugars. Example 4 As a high-performance water reducing agent, Takemoto Yusashi Co., Ltd.'s product name "Pole Fine 510N" was used, the concrete formulation shown in Table 4 was used, and tartaric acid and sucrose were varied in various ways.
After mixing 50 pieces of concrete at a temperature of 8°C, the change in slump over time was measured. The result is the fifth
Shown in the table. Note that Experiment Nos. 52 and 53 are comparative examples.

【table】

[Table] Next, in Table 5, the changes in slump over time when sodium gluconate, sodium lactic acid, and succinic acid were used in place of tartaric acid in the concrete of Example 4, along with the amounts of each added. As you can see from this table, sodium gluconate,
When using sodium lactate and succinic acid, the slump value decreases rapidly, especially when using sodium gluconate.
Those containing 0.15 and 0.20% by weight set rapidly after 5 to 20 minutes and are significantly inferior to the present invention. Furthermore, by removing only the high-performance water reducing agent from the concrete mix of Experiment No. 56, the target slump was 10 ± 2 cm.
When concrete (w/c 38%) was mixed, the result was as in Experiment No. 68, and slump loss was promoted.

Claims (1)

[Claims] 1. A method for preventing slump loss in concrete, which comprises adding 0.005 to 0.3% by weight of tartaric acid or its salts, or 0.005 to 0.1% by weight of these and sugars, to the cement content of concrete to which a high performance water reducer has been added.