JPH0335252B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing concrete products of superior strength by steam curing concrete compacts made of a combination of materials. Conventionally, in order to produce high-strength concrete products in a relatively short time, it was necessary to further autoclave the product after steam curing. Also, by adding calcium sulfite hemihydrate to Portland cement and steam curing it, the strength of the concrete product obtained is increased compared to when using only Portland cement and steam curing, but the strength is only 25%. It is only about %. Alternatively, there is a known technique in which insoluble anhydrous gypsum is added as a strength-enhancing material and steam-cured, but in this case, the fineness or dissolution rate of the added insoluble anhydrous gypsum greatly affects the strength properties of the concrete product. , the usable anhydrous plaster is limited. However, if calcium sulfite hemihydrate and insoluble anhydrous gypsum are used in combination, the strength of the resulting concrete product will be greater than that of the calcium sulfite hemihydrate as a result of the interaction between calcium sulfite hemihydrate and insoluble anhydrous gypsum. It has been discovered that the concrete product is larger than when hydrates and insoluble anhydrous gypsum are added alone, and that concrete products with excellent strength can be stably produced in a short period of time by omitting autoclave treatment and only by steam curing, and the present invention is based on the present invention. reached.
In other words, the gist of the present invention is to use Portland cement.
To 100 parts by weight, 1 to 4 parts by weight of calcium sulfite hemihydrate and 1 to 5 parts by weight of insoluble anhydrous plaster, and a total of 3 to 8 parts by weight of both, are added, and concrete is kneaded and shaped, followed by atmospheric pressure steaming. This is a method for producing a high-strength hardened concrete body characterized by curing. The present invention will be explained in detail below. The calcium sulfite hemihydrate used in the present invention is a synthetic product, a by-product of flue gas desulfurization, etc., and its fineness is not particularly limited, but it is preferably one with a Blaine specific surface area of 2500 cm ² /g or more. Insoluble anhydrous gypsum is natural anhydrous gypsum,
Insoluble anhydrous gypsum such as hydrofluoric acid by-product anhydrous gypsum and insoluble anhydrous gypsum obtained by heat treating dihydrate or hemihydrate gypsum are used. The powder degree is not particularly limited, but preferably has a Blaine specific surface area of 2500 cm ² /g or more. The amount of calcium sulfite hemihydrate to be used is preferably 1 to 4 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of Portland cement. If the amount is less than 1 part by weight, the effect of calcium sulfite hemihydrate will not be exhibited. If more than 4 parts by weight is added, the strength of the resulting concrete product will decrease, and the setting time of the concrete will become longer, requiring a longer pretreatment time before steam curing. The amount of insoluble anhydrous gypsum used is preferably 1 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight of Portland cement. 1
If the amount is less than 5 parts by weight, there will be no effect of adding insoluble anhydrous gypsum, and if it exceeds 5 parts by weight, the strength-enhancing effect will not increase accordingly, but rather the setting time will become longer. In the method of the present invention, it is necessary that the amounts of calcium sulfite hemihydrate and insoluble anhydrous gypsum are used individually within certain ranges as described above, and the total amount of calcium sulfite hemihydrate and insoluble anhydrous gypsum is required to be within a certain range. is 3 parts per 100 parts by weight of Portland cement.
~8 parts by weight is also required. If the total amount is less than 3 parts by weight, the effect of addition is not significantly limited. On the other hand, if the amount exceeds 8 parts by weight, the strength of the concrete product obtained will decrease, and furthermore, the setting time of the concrete will become longer, requiring a longer pre-preparation time before steam curing. The Portland cements used in the present invention are normally early strength, very early strength, medium heat Portland cements and mixed cements, especially ordinary, early strength,
High strength can be obtained when using ultra-early strength Portland cement. The present invention was achieved by kneading and forming concrete using the aforementioned Portland cement, calcium sulfite hemihydrate, and insoluble anhydrous plaster, pre-curing it at around room temperature for several hours, and then curing it with atmospheric pressure steam. Ru. The mix of concrete is not particularly limited, but if high strength is desired, conditions are selected in which the mix is rich in cement and the water-cement ratio is low. Furthermore, the use of water reducing agents or high-performance water reducing agents is effective in producing high-strength concrete products because it reduces the water-cement ratio. The atmospheric pressure steam curing conditions are carried out according to conventional methods. For example, it is held at a temperature of 55 to 80°C for 3 to 6 hours. According to the present invention, by adding a specific amount of calcium sulfite hemihydrate and insoluble anhydrous plaster to Portland cement, forming concrete, and producing a concrete product by atmospheric pressure steam curing, The strength of the product is greatly improved compared to the case of , and especially when ordinary, early-strength, and ultra-early-strength Portland cements are used, high-strength concrete products equivalent to concrete products manufactured by autoclave curing can be produced using only atmospheric pressure steam curing. Not only has it become possible to do this, but it has also made it possible to manufacture concrete products with stable hardening characteristics, and its industrial value is great. Moreover, in the present invention, the fineness of the insoluble anhydrous gypsum used is different from the conventional one, and the influence on product strength is significantly alleviated. Next, the present invention will be specifically explained using experimental examples and examples. Experimental Example 1 Ordinary Portland cement (trade name: Asano Cement, manufactured by Nippon Cement Co., Ltd.), industrial calcium sulfite hemihydrate (manufactured by Tomita Pharmaceutical Co., Ltd.), and insoluble hydrofluoric acid by-product anhydrous plaster (Morita Chemical Co., Ltd.) The mortar was kneaded using a mortar (manufactured by Mimaki Co., Ltd.), molded into a 4 x 4 x 16 cm mold, and then cured with atmospheric pressure steam and the compressive strength was measured. The mortar composition was cement:sand = 1:2, water-cement ratio = 0.35, and the sand used was a mixture of Toyoura standard sand, Soma coarse sand, and Soma coarse sand at a ratio of 1:1:1. The preheating time at 20°C before steam curing was 6 hours and 2 hours, and the temperature was increased to 70°C at a rate of 20°C/hour.
After holding for a period of time and curing with normal pressure steam, let it cool and pour water for 24 hours.
The compressive strength over time was measured. Calcium sulfite hemihydrate and insoluble anhydrous gypsum have a Blaine value of 7300, respectively.
It was set to 5500cm ² /g.

【table】

【table】

[Table] The strength values are shown in Tables 1 and 2 above. 1st
The table shows the case where the pretreatment time was 6 hours, and the second table shows the case where the pretreatment time was 2 hours. From these results, it is clear that by adding calcium sulfite hemihydrate and insoluble anhydrous gypsum in combination and steam curing, the hardening strength is greatly increased, and the strength enhancement effect is greater than when each is used alone. be. Furthermore, if the amount of calcium sulfite hemihydrate and insoluble anhydrous gypsum used is increased, the strength-enhancing effect decreases, so there is an upper limit to the amount used. This tendency becomes remarkable when the preposition time is short. Experimental Example 2 The hardening strength of mortar was measured using insoluble anhydrous gypsum (natural anhydrous gypsum) with different finenesses and calcium sulfite hemihydrate obtained in the process of flue gas desulfurization. The results are shown in Table 3. In this case, the pretreatment time was 6 hours, and the other conditions were the same as in Example 1.

[Table] As is clear from Table 3, if calcium sulfite hemihydrate and insoluble anhydrous gypsum are added together, a hardened product with stable high strength can be obtained even if the powderiness of the anhydrous gypsum changes. is possible. Example Ordinary Portland cement used in Experimental Example 1,
Knead and form concrete using calcium sulfite hemihydrate and insoluble anhydrous plaster to form a 10φ
A test specimen measuring cm x 20 cm was obtained. The obtained test specimens were steam-cured and then the hardening strength was measured. The formulation is shown in Table 4. The fine aggregate used was river sand (from Fujikawa), and the coarse aggregate used crushed stone with a maximum dimension of 20 mm. Atmospheric pressure steam curing was carried out by leaving the specimen at 20°C for 4 hours after molding, then increasing the temperature to 70°C at a rate of 20°C/hour, and maintaining that temperature for 6 hours. then
It was slowly cooled to 20°C, and from 24 hours after molding, it was cured in water at 20°C for 3 days, and then it was cured in air until it reached the age of each material. Compressive strength is shown in Table 5.

【table】

【table】

[Table] As is clear from Table 5, according to the method of the present invention, a hardened concrete body having a compressive strength of 800 Kgf/cm ² or more can be produced in a short time. On the other hand, a comparative example in which calcium sulfite hemihydrate and inert anhydrous plaster were not added as in the present invention obtained only a much lower compressive strength.

Claims (1)

[Claims] 1 100 parts by weight of Portland cement, 1 to 4 parts by weight of calcium sulfite hemihydrate and 1 to 5 parts by weight of insoluble anhydrous plaster, and the total amount of both is 3 parts by weight.
A method for producing a concrete product, which comprises adding 8 parts by weight of concrete, kneading and shaping the concrete, and curing with normal pressure steam.