JPH0571531B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a cement composition used in the production of concrete products by steam curing, and more specifically to a cement composition that has better workability than Portland cement alone. The present invention also relates to a method of producing high-strength concrete products using the cement composition. [Conventional technology] Conventionally, in manufacturing concrete products, cement compositions in which high-strength admixtures such as anhydrite are added to Portland cement have been used from the viewpoint of shortening the manufacturing process and increasing the strength of the product. Concrete molded bodies are manufactured by steam curing (Japanese Patent Publication No. 1983-40104). [Problem to be solved by the invention] However, Portland cement containing high-strength admixtures has a problem of low fluidity when mixed with water, resulting in poor workability when poured into a mold during molding. . This tendency increases as the unit amount of cement increases when producing concrete, but as the unit amount of cement decreases,
It is not preferable to reduce the unit amount of cement because the strength of the resulting concrete product will decrease. Also, even if you use a water reducing agent to reduce the water/cement ratio and increase strength, the water reducing effect is small, and in order to obtain high fluidity with a small water/cement ratio, a large amount of water reducing agent is required. There is a need,
As a result, there was a problem that manufacturing costs increased. [Means for Solving the Problems] In order to solve the above problems, the present inventor conducted research and replaced a portion of Portland cement with granulated slag and added a substance containing sulfur trioxide. When a cement composition made of
The present invention was completed by discovering that the strength of concrete products obtained by steam curing is equal to or higher than that of conventional steam-cured concrete products. That is, the present invention is a cement composition used when manufacturing concrete products by steam curing, in which 8 to 60% by weight of Portland cement is replaced with granulated slag powder having a Blaine specific surface area of 3000 cm ² /g or more. It is a compound containing sulfur trioxide or a substance containing sulfur trioxide, and the sulfur trioxide content is 5 to 8% by weight in terms of SO ₃ and the sulfur trioxide content is Of this, the content of hydrates is 4.5 in terms of SO ₃ .
This is a cement composition for producing steam-cured concrete products, characterized in that the content is less than % by weight. In addition, sulfur trioxide or a substance containing sulfur trioxide is blended with 8 to 60% by weight of Portland cement replaced with granulated slag powder having a Blaine specific surface area of 3000 cm ² /g or more. The content of sulfur trioxide is 5 to 8% by weight in terms of _SO3 , and the content of hydrated sulfur trioxide is 4.5% by weight in terms of _SO3 . This is a method for producing a steam-cured concrete product, which comprises producing concrete using the following cement composition, molding the concrete, and then steam-curing it. The present invention will be explained in detail below. The granulated slag powder used in the present invention is obtained by pulverizing granulated blast furnace slag to a Blaine specific surface area of 3000 cm ² /g or more. Granulated slag powder with a Blaine specific surface area of less than 3000 cm ² /g has low hydraulic properties and is used as a cement component (binder) when mixed with concrete.
The effect is small. The replacement ratio of granulated slag powder to Portland cement is such that the amount of granulated slag powder is 8 to 60% by weight relative to the total amount of Portland cement and granulated slag powder. If the replacement ratio of granulated slag powder to Portland cement is less than 8% by weight,
Because the cost reduction and the fluidity of the cement composition do not improve much, the effect of improving workability cannot be obtained.
If it exceeds 60% by weight, the strength of the resulting steam-cured concrete product tends to decrease. Examples of substances containing sulfur trioxide include gypsum such as anhydrite, and commercially available high-strength admixtures. Normally, Portland cement contains 0.5 to 4.5% by weight of sulfur trioxide, but the sulfur trioxide derived from Portland cement is also contained in sulfur trioxide or substances containing sulfur trioxide that are separately blended. It has the same effect as sulfur trioxide. The amount of sulfur trioxide or the substance containing sulfur trioxide is such that the sulfur trioxide content in the cement composition is 5 to 8% by weight in terms of _SO3 , preferably 5 to 6% by weight. %. If the sulfur trioxide content in the cement composition is less than 5% by weight, the strength of the resulting concrete product will be low;
If it exceeds 8% by weight, strength development will be inhibited and solidification time will become longer, requiring a longer time to manufacture concrete products. The sulfur trioxide component to be blended as sulfur trioxide and a substance containing sulfur trioxide is preferably blended as an anhydride. When mixed with compounds containing water of crystallization, such as gypsum dihydrate or gypsum hemihydrate, they tend to coagulate abnormally when mixed with water, resulting in poor workability and reduced strength of the resulting concrete product. Tend. Therefore, in the cement composition of the present invention, the content of sulfur trioxide blended as a compound containing water of crystallization, including that derived from Portland cement, is 4.5 in terms of _SO3 .
% by weight or less. The steam curing temperature in the method for producing a concrete product of the present invention is preferably 30 to 100°C, and the higher the steam curing temperature, the higher the strength of the cement product can be produced in a shorter curing time. However, if it is set too high, cracks are likely to occur on the surface of the concrete product. Furthermore, the longer the steam curing time, the greater the strength of the resulting concrete product, but the steam curing is usually about 2 to 20 hours, preferably about 6 to 18 hours. The types and amounts of fine aggregate and coarse aggregate used in producing the concrete products of the present invention are not particularly limited, and may be those used in producing ordinary concrete products. In addition, various cement admixtures such as water reducing agents may be used as appropriate within a range that does not affect the effects of the present invention. In addition,
The cement composition of the present invention has a large effect when a water reducing agent is added, and when a water reducing agent is added, it tends to exhibit sufficient fluidity even at a small water/cement ratio. The present invention will be explained below with reference to Examples. Example 1 Concrete with the composition shown in Table 1 was made into φ10×20cm
Formed into a cylindrical shape, pre-cured at 20℃ for 4 hours, steam-cured for 17 hours, and then heated to the specified material age.
A concrete product was obtained by air-drying at 20°C. The Blaine specific surface area of the granulated slag powder used was 4500 cm ² /g. The temperature during steam curing was raised from 20°C to 90°C over 3.5 hours, maintained at 90°C for 4 hours, and then allowed to cool naturally for 9.5 hours to cool to 20°C. Table 2 shows the slump of the concrete measured as an evaluation of workability, the J funnel flow time of the mortar obtained by removing coarse aggregate from each concrete, and the compressive strength of the concrete product at each material age. Example 2 Concrete with the composition shown in Table 1 was made into φ10×20cm
It was formed into a cylindrical shape, pre-cured at 20°C for 1 hour, steam-cured for 6.5 hours, and then air-dryed at 20°C until the specified material age to obtain a concrete product. The Blaine specific surface area of the granulated slag powder used was 4500 cm ² /g. In addition, the temperature during steam curing is adjusted from 20℃ to 90℃ over 2.5 hours.
The temperature was raised to 90°C, maintained at 90°C for 2 hours, and then lowered to 20°C over 2 hours. Table 2 shows the slump and VB values of concrete and the compressive strength of concrete products, which were measured as evaluations of workability. Example 3 Concrete with the composition shown in Table 1 was made into φ10×20cm
It was formed into a cylindrical shape, pre-cured at 20°C for 4 hours, steam-cured for 15.5 hours, and then air-dryed at 20°C until the specified material age to obtain a concrete product. The Blaine specific surface area of the granulated slag powder used was 4500 cm ² /g. In addition, the temperature during steam curing is adjusted from 20℃ to 90℃ over 3.5 hours.
The temperature was raised to 90°C, maintained at 90°C for 3 hours, and then allowed to cool naturally for 9 hours to 20°C. Table 2 shows the slump of concrete measured as an evaluation of workability and the compressive strength of concrete products at each material age.

[Table] However, the 〓 mark in the table indicates a comparative example.

[Table] However, the 〓 mark in the table indicates a comparative example.
[Effects of the Invention] According to the present invention, compared to concrete for steam-cured concrete products using only Portland cement as a cement component, a concrete product having the same or higher strength can be produced by improving the fluidity of the cement composition. By maintaining superior workability, it can be manufactured at low cost.

Claims (1)

[Scope of Claims] 1. A cement composition used when producing concrete products by steam curing, which comprises 8 to 60% by weight of Portland cement having a Blaine specific surface area of 3000
cm ² /g or more of granulated slag powder mixed with sulfur trioxide or a substance containing sulfur trioxide, and the sulfur trioxide content is 5 to 8 weight in terms of SO ₃ %, and the content of hydrated sulfur trioxide content is 4.5% by weight or less calculated as SO ₃ , for the production of steam-cured concrete products. Cement composition. 2. 8 to 60% by weight of Portland cement is replaced with granulated slag powder with a Blaine specific surface area of 3000 cm ² /g or more, and sulfur trioxide or a substance containing sulfur trioxide is blended with it, and the sulfur trioxide content is The content is 5 to 8% by weight in terms of SO ₃ and the content of sulfur trioxide contained as hydrate is 4.5% by weight or less in terms of SO ₃ A method for producing a steam-cured concrete product, which comprises producing concrete using a cement composition, forming the concrete, and then steam-curing the concrete.