JPS6215500B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cement composition, and more particularly to a cement composition containing an enzymatic dextrin. Cement compositions, such as cement paste, mortar, grout, concrete, etc., have various properties such as softness (slump), setting properties, hardening properties, etc. Various cement admixtures are used to match the initial design values. Slump during kneading of cement composition is
In general, the amount of water for kneading increases as the amount of water increases, but by adding a cement admixture known as a water reducer to the cement composition, the amount of water for kneading to obtain a kneaded product with the same slump can be reduced. If the amount of mixing water for cement is the same,
A kneaded material with large slump can be obtained. In general, the use of water reducing agents in cement compositions is
A decrease in the amount of mixing water results in a decrease in breathing, a decrease in drying shrinkage, and a decrease in the water-cement ratio, resulting in an increase in strength.If the water-cement ratio remains the same, there is an increase in fluidity and workability due to an increase in slump. , it has many excellent derivative effects. As high-performance water reducing agents used for these purposes, naphthalene sulfonic acid formaldehyde high condensates and their salts, melamine sulfonic acid formaldehyde condensates and their salts, etc. are commercially available. Depending on the target, use may be undesirable. After kneading, the cement composition undergoes a setting process in which its slump gradually decreases over time.
Furthermore, as the number of days passes, the material undergoes a curing process in which strength gradually develops, resulting in a cured product. Regarding the condensation process, ASTMC-403-77 established by the American Society for Testing and Materials
The beginning of setting and the end of setting are defined in ``Method for Measuring Concrete Setting Time Using Penetration Resistance.'' Cement compositions, especially concrete, may accelerate or retard this setting process depending on the object to which it is applied; in the former case, a cement admixture known as an accelerator or fast-strengthening agent, and in the latter case a cement admixture known as a retarder. are mixed into cement compositions. For example, in cases where the distance between the plant and the construction site is large, such as for ready-mixed concrete, it takes a considerable amount of time to construct after mixing, and the slump of the ready-mixed concrete at the time of pouring is considerably lower than the slump immediately after mixing. The above disadvantages are likely to occur. As a measure to reduce the decrease in slump, a retarder is mixed into the cement composition. Additionally, on top of the concrete layer that has already been placed,
In order to integrate the old and new concrete layers by pouring a new concrete layer, it is generally extremely difficult to pour the new concrete layer in one piece if the existing concrete layer has already begun to harden. It is said that this must be in a state before the setting process of the already poured concrete layer reaches the above-mentioned initial setting state. The time it takes to reach the initial setting state after mixing is called the initial setting time, which is approximately 5 to 6 hours for ordinary concrete, but it is often used in the construction of concrete buildings using the sliding form method or in the construction of large-scale watertight concrete structures. As in the case of construction, there are cases where the concrete placement schedule has to extend over several days, and in such cases, if the initial setting time is not delayed by about 10 to 20 hours, it will be difficult to integrate the old and new concrete. becomes difficult. In this way, retarders are mixed into cement compositions when it is desired to delay the first setting time, but there is a difference in the first setting time between plain concrete without the retarder and concrete with the retarder added. That is, the delay time is adjusted by adjusting the amount of the retarder mixed. However, in general, when a retarder is mixed into a cement composition, it delays setting and at the same time delays the onset of the subsequent hardening process.In particular, the development of initial strength is delayed, so the retarder is used unnecessarily. Mixing is not preferred.
In particular, known retarders, such as lignin sulfonates and oxycarboxylate salts, when mixed in a cement composition in an amount exceeding a certain value, rapidly retard setting, and as a result, the development of strength is significantly delayed or inhibited. As mentioned above, it was not possible to use the amount added to achieve a delay time of more than 10 hours or more. An object of the present invention is to provide a cement composition having a well-balanced water-reducing property, strength-enhancing property, and setting retarding property, and another object of the present invention is to provide a cement admixture for use in mixing with the cement composition. do. As a result of intensive research to achieve the above object, the present inventors have developed a cement composition containing a specific quality of enzymatic dextrin, which has been abandoned due to its weak setting retardation properties. The present invention was completed based on the discovery that this material exhibits extremely excellent water-reducing properties, strength-enhancing properties, and setting retardation properties. The present invention has a cold water soluble content: 92% by weight or more, a reducing sugar content calculated as glucose: 5 to 30% by weight, and
50wt% aqueous solution viscosity at 50℃: 20~500cps
This is a cement composition characterized by containing an enzymatically produced dextrin. In the present invention, enzymatic dextrin refers to dextrins produced by moderate decomposition of starch, which are widely used in thickeners, binders, food additives, etc. It is a dextrin obtained by hydrolysis using a high-temperature liquefaction method. Enzyme-produced dextrin has milder manufacturing conditions than dextrins produced by other manufacturing methods, such as acid-free roasting and acid roasting, so it contains low-molecular-weight components that are undesirable as cement admixtures. The content of high molecular weight components is extremely low, and the molecules are homogeneous and have uniform lengths. In the present invention, the cold water soluble content is defined as 10 g of sample dextrin dispersed in 150 ml of distilled water at 21°C.
℃ temperature for 1 hour with stirring, the insoluble matter was separated, and the liquid was evaporated to dryness. The dry solid content obtained was expressed as a weight % based on the sample dextrin. In addition, when the liquid is evaporated to dryness, a hard film is formed on the surface of the dried product, which hinders the further drying process.
In order to prevent errors from occurring in the measured values, a so-called paper method is used in which a cylindrical pleated paper is immersed in the sample solution and evaporated to dryness. In addition, the reducing sugar content is
-Eynon) method is the value expressed as the reducing sugar content in terms of glucose. In the present invention, cold water soluble content: 92% by weight or more,
Reducing sugar content calculated as glucose: 5 to 30% by weight, and the viscosity of a 50% by weight aqueous solution measured at a temperature of 50°C is 20 to 500 cps, preferably 50 to
100 cps of enzymatically produced dextrin is mixed into a cement composition and will be explained using a drawing (Figure 1) showing the relationship between the quality of enzymatically produced dextrin and the cement composition. In FIG. 1, the central region A is the region that defines the above-mentioned quality, and the cement composition has both a large water-reducing property and a strong strength-enhancing property, and also shows an appropriate setting retardation property depending on the amount added. This is a region exhibiting favorable setting retardation characteristics, in which the initial setting time can be extended for a long time without adversely affecting the cured physical properties of the composition. In region B on the left, that is, in the region where the cold water soluble content is less than 92% by weight, the reducing sugar content is less than 5% by weight, and the viscosity exceeds 500 cps, water reduction properties, strength enhancement properties, and setting retardation properties are all improved. In the C region on the right, the reducing sugar content exceeds 30% by weight and the viscosity is small.
In the region of less than 20 cps, both the water-reducing effect and the strength-enhancing effect are small, and the setting retardation is so excessive that it adversely affects the hardening properties of the cement composition, and in some cases, it may even exhibit abnormal setting. . The cement composition of the present invention is a cement composition containing enzymatic dextrin of the quality described above,
Its content is usually from 0.1 to cement weight
1.0% by weight, preferably 0.2-0.6% by weight. The cement composition of the present invention uses a typical water reducing agent, naphthalene sulfonic acid formaldehyde high condensate.
It has a water-reducing property comparable to that of a cement composition containing Na salt, and the delay time can be arbitrarily adjusted depending on the content of enzymatic dextrin. Even if the delay time is 10 hours to 20 hours or more, the basic strength of concrete28
The day intensity does not decrease, but rather improves. In addition, even when the delay time is extended, the initial strength decreases slightly, but the strength at 28 days does not decrease or even improves. In cement compositions in which the content of enzymatic dextrin is smaller than the above range, the water-reducing effect, strength-enhancing effect, and setting retardation effect are not significant; reaches a plateau and retardation of setting is significantly prolonged. 0.1 to 1.0% by weight of enzymatic dextrin to cement;
In particular, cement compositions containing 0.2 to 0.6% by weight,
It has a good balance of water-reducing properties, strength-enhancing properties, and setting retardation properties, and is extremely preferred as a cement composition. In the present invention, there is no particular restriction on the method of adding the enzymatically produced dextrin of the quality mentioned above to the cement composition, and conventionally known methods such as addition during kneading, addition after kneading, addition in premix before kneading, addition as a powder, etc. Any method such as addition, addition as an aqueous solution, divisional addition, continuous addition, etc. can be adopted. Further, other cement admixtures such as AE agents, water reducing agents, AE water reducing agents, swelling agents, early strengthening agents, sizing agents, etc. can also be used in combination with the cement composition of the present invention. The present invention provides a cement composition containing an enzyme-produced dextrin, which is available at a relatively low cost, as a main ingredient and has a well-balanced water-reducing property, strength-enhancing property, and set retardation property, and in particular, the set retardation time is adjusted by its content. The industrial significance of this is extremely large. Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples using concrete. However, the scope of the present invention is not limited in any way by the following examples. Examples and Comparative Examples (1) Materials used Cement: Ordinary Portland cement Fine aggregate: River sand from Oigawa, mountain sand from Chiba (mixing ratio 8:2) Coarse aggregate: Crushed stone from Ome (MS = 20 mm) (2) Mixture used Agents As per the table below

【table】

[Table] (3) Concrete tests The concrete compositions made up of items (1) and (2) above were kneaded, and various tests were conducted on the kneaded product. The kneading conditions and various test results are shown in Table 1. As is clear from Table 1, the cement composition of the present invention showed the same slump at the same amount of water as the cement composition to which high performance water reducer F was added (Comparative Example 6); It has a water-reducing property equivalent to that of cement compositions, and although its strength is inferior to 7-day strength due to delayed setting, it is 28
It has strength-enhancing properties that increase day strength by more than 10%, and its air entrainment properties are also small. In the cement compositions (Comparative Examples 2 and C) containing enzymatic dextrins (B and C) of quality outside the range specified in the present invention,
Either abnormal condensation occurs and the 28-day strength is hardly developed (Comparative Example 2), or the water-reducing property is extremely low (Comparative Example 3). In addition, none of the dextrins (D and F) manufactured using different manufacturing methods satisfies the quality within the range defined by the present invention, and the cement compositions containing them (Comparative Examples 4 and 5) have water-reducing properties. and delay are both small.

【table】 [Brief explanation of the drawing]

Figure 1: A diagram showing the relationship between the quality of enzymatic dextrin and the properties of cement compositions. Upper axis: viscosity of 50% by weight aqueous solution at 50℃ (cps), middle axis: cold water soluble content (wt%), lower axis...
...Reducing sugar content (weight%) converted to glucose,
A: Indicates the scope of the present invention, where the water reducing property is large and setting retardation is obtained depending on the amount used, B: Area where both water reducing property and setting retarding property are small, C: Water reducing property is small and setting retarding property is obtained. excessive area.

Claims (1)

[Scope of Claims] 1. An enzymatic dextrin having a cold water soluble content: 92% by weight or more, a reducing sugar content calculated as glucose: 5 to 30% by weight, and a 50% by weight aqueous solution viscosity at 50°C: 20 to 500 cps. A cement composition characterized by containing. 2. The cement composition according to claim 1, wherein the content of enzymatic dextrin is 0.1 to 1.0% by weight based on the cement.