JPS5846478B2 - Method for manufacturing hardened bodies using steel slag - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a hardened body mainly made of steel slag that can be used for general structures.

As is generally known, large amounts of steel slag such as blast furnace slag and converter slag are generated in the steel manufacturing process, and in recent years,
In order to make effective use of this material, granulation, ballastization, etc. are being promoted, and various methods for manufacturing structures using these materials have been proposed.

For example, gypsum, slaked lime, and water are added to steel slag such as slow-cooled blast furnace slag, granulated blast furnace slag, and converter slag, mixed, poured into a mold, and after a few days, the mold is removed to obtain the specified strength. There is a method of producing a cured product by curing in air or in water.

This hardened product utilizes the latent hydraulic properties of steel slag, and uses slaked lime to remove Cab in steel slag, A/203,
Accelerates the elution of 5i02, and produces calcium and sulfoaluminate (hereinafter referred to as ettringite) through a hydration reaction with gypsum.
At the same time, CaO,5i02゜A, which became a residue
An ultra-fine gel whose main component is l2O3 was formed, and this gel filled the voids in the ettringite, making it ultra-dense and strong. However, when the above atmospheric curing was performed, CO2 in the air reacts with the slaked lime in the surface layer of the hardened body to become stable CaCO3, and the slaked lime in the surface layer of the hardened body becomes insufficient, leading to insufficient elution of CaO, Al2O3, and 5i02 in the blast furnace slag, and the moisture in the surface layer of the hardened body increases. Due to evaporation, there is a lack of moisture, which reduces the production of ettringite, and further (in the early stage of hardening of this hardened material, ettringite reacts with CO2 in the air and decomposes, etc.), as shown in atmospheric curing in Table 1. No ettringite was observed in the surface layer of the hardened material after curing for 7 and 28 days, and when this was subjected to a wear resistance test, the wear rate of the surface layer was large, as shown by the solid line A in Figure 1. Therefore, the wear rate is about 8.5 times that of the surface layer of Portland cement (hereinafter referred to as cement) shown in the solid line, and it has the disadvantage of being extremely "soft and brittle" and causing rapid peeling. had.

In addition, when curing in water, problems such as contact between the surface layer of the hardened body and CO2 in the air and lack of moisture in the surface layer do not occur as in the case of atmospheric curing, but the slaked lime on the surface layer of the hardened body remains intact or ionized. As a result, it becomes Ca+ and flows out into the water, resulting in a lack of slaked lime on the surface layer of the hardened body, and as shown in Table 1 for underwater curing, the presence of ettringite is found in the surface layer of the hardened body after 7 and 28 days of curing. When this was subjected to an abrasion resistance test, the wear rate of the surface layer of the hardened material was about 4.5 times that of the surface layer of cement, as shown by the solid line IB in Figure 1. Although the "soft and brittle" properties were somewhat improved and the amount of peeling was somewhat reduced, it was still insufficient for practical use.

Such peeling of the surface layer of the cured product greatly impairs the appearance of the cured product, and there are problems such as restrictions on where it can be used.

In order to solve this problem, the present inventors conducted various experiments and studies, and applied lime milk to the surface of the hardened material to cut off air.
An attempt was made to prevent CO2 in the atmosphere from coming into contact with the surface of the cured product.

However, with this method, when the moisture in the milk of lime evaporates, the lime applied to the surface of the hardened product peels off, so measures to prevent this lime from peeling off are required. As the process progresses, the lime removes moisture from the surface layer of the hardened body, resulting in a lack of moisture in the surface layer of the hardened body, which, as in the case of atmospheric curing, prevents the formation of ettringite in the surface layer of the hardened body, preventing peeling of the surface layer of the hardened body. It was not a sufficient countermeasure.

In addition, by adding a large amount of slaked lime to water to make lime milk, and curing the hardened material by immersing it in this slaked lime milk, it is possible to prevent the peeling of the lime milk and the water evaporation of the lime milk as described above. In Table 1, as shown in the lime milk curing, ettringite was present in the surface layer of the hardened product, and in addition, the presence of gel was observed, but the wear rate was as bad as that of the water curing.

This is due to Ca+ in the milk of lime penetrating the surface layer of the hardened body,
Due to the contact between the surface of the hardened body and milk of lime, ettringite and gel are generated on the surface layer of the hardened body as described above, but it is thought that the generated ettringite becomes acicular and increases the wear rate of the surface layer of the hardened body. As a result of further investigation, it was found that by curing in slaked lime water (hereinafter referred to as lime water) having a pH higher than the pH in the hardened body, the surface layer of the hardened body was cured in lime water curing a and b in Table 1. As shown, in addition to the presence of ettringite, the presence of gel was observed, and the wear rate of the hardened surface layer approximated that of cement after 7 days of curing, as shown by the solid line C in Figure 1, and was approximately the same after 28 days of curing. It turned out to be.

On the other hand, when the cured product is cured in lime water with a pH lower than that of the cured product, as shown in lime curing C in Table 1, the presence of ettringite is not observed in the surface layer of the cured product, and the wear rate of the surface layer of the cured product is lower than that of the above-mentioned underwater curing. As for these reasons, according to the studies of the present inventors, when the hardened material is cured in rice field lime water whose temperature is lower than that of the hardened material, slaked lime and Ca+ on the surface layer of the hardened material are absorbed during curing. As a result, CaO, 5i02. Al2
It is thought that the elution of O3 becomes insufficient, the amount of ettringite and gel produced decreases, and the wear rate increases.

In addition, when the cured body is cured in one or more - lime water that the cured body has, the slaked lime and Ca+ on the surface layer of the hardened body do not elute into the slaked lime water, or the Ca+ in the lime water does not enter the surface layer of the hardened body. , the surface layer of the hardened body can be cured while maintaining an appropriate amount of slaked lime in the same way as the center of the hardened body.
It is thought that the formation of gel on the surface layer of the hardened body is promoted and strip-shaped ettringite grows, and the wear rate of the surface layer of the hardened body is at a good level similar to that of cement.

The wear resistance tests described above were conducted using the apparatus shown in FIG. A thrust bearing 12 is fixedly supported via the sample box 6, and a thrust bearing 12
A support shaft 11 provided on the lower surface of the tray 3 is rotatably connected to the motor 2 via a rotational drive mechanism 10.

In each abrasion resistance test, sand 9 with a grain size of 0.3 to 0.151 m and a weight of 50 g is first placed in the saucer 3 as an abrasion accelerator for the sample 7, and the sand 9 shown in Fig. 2 C++ is placed in the sample box 5. A sample 7 with a side length a of 40 mm and a thickness T1 is inserted, and a 5-mm weight 8 is placed on it.

Next, the motor 2 is driven to rotate the saucer 3 via the rotary drive mechanism 10 at a rotational speed of 60 times/minute for 10 minutes.

The wear rate was determined by taking out the sample 7 from the sample box 5 after 10 minutes of operation and measuring the remaining sample thickness T2.

The present invention was made based on the above knowledge, and its characteristics are that water is added to and mixed with raw materials mainly consisting of melting furnace slag, gypsum, and slaked lime, and this is poured into the mold. The molded cured body has at least the surface layer of the cured body.
The present invention provides a method for producing a hardened product using steel slag, which is cured with lime water having a pH of H or higher.

Examples of the present invention are shown in Table 2 below. p
In the case of curing by immersing in lime water with a pH higher than H, in example ①, lime water with a pH higher than the pH of the hardened body is poured into a hole placed on the upper surface of the hardened body formed by flattening it on an earthen floor. hand,
When the mouth of the insect is kept moist with lime water from the beginning of curing to the curing stage, in the comparative example ■, the hardened body is cured by immersing it in lime water with a pH lower than that of the hardened body from the beginning of curing to the curing stage. In this case, Example 3 shows the case where the cement was cured in the air for 28 days.

The pH of this lime water was adjusted as follows.Example 1, Example 2: 2 weights of slaked lime φ were added to the water in advance, and the lime water p
H was maintained at 12.3.

Example u1 Example ■: The measured value of the pH meter installed in lime water is 11.
The slaked lime in the hopper was cut out and put into the lime water so that the pH was maintained at 0 or 9.0.The pH of the lime water was adjusted in this way. Although the wear rate is inferior to that of Cement H in Example (2), the wear rate of the surface layer of the hardened material after 28 days of curing is approximately the same, and even during curing and after 100 days of being left in the atmosphere, the wear rate of the surface layer of the hardened material remains the same. Similar to cement, no peeling was observed.

Further, in Comparative Example (3), the wear rate was inferior to that of cement after 7-day and 28-day curing, and some peeling of the surface layer of the hardened material was observed after 100 days of being left in the atmosphere.

In addition, the pH of the surface layer of the cured product in the present invention is
For example, use an existing method for measuring the pH of solids, such as the soil test method established by the Japan Society for the Study of Soil Quality, or use the JIS
According to the pH measurement method specified by Z8802-1978,
The pH of the surface layer of the cured body shown in the above examples is a value determined in advance, and is determined according to the soil test method described above, and specifically as follows.

■ The sample hardened body has a particle size of 2 obtained by grinding the surface layer of the hardened body.
■ Prepare the sample based on the soil test method described above, and then measure the pH value using a pH meter adjusted according to the same method in the [test order] based on the same method. 〇Also, the pH of the curing lime water in the Kinoe oven was determined by adding 0.2 weight φ or more of slaked lime and adjusting the pH of the lime water to 12.05 or more, that is, saturating the lime water, as in Example I and Example ■. It is preferable to cure the cured product in a state that improves workability and simplifies management.

As explained above, by simple and inexpensive processing, not only the surface layer of the cured product but also the entire surface becomes dense and strong, and the appearance of the surface of the cured product is very good without peeling during curing or in the second half of leaving it in the atmosphere. This will make it possible to expand the uses of hardened products and expand the use of steel slag, and the effects it will bring to this field will be significant.

[Brief explanation of the drawing]

In Figure 1, the vertical axis is the distance from the surface of the cured product toward the center.
The horizontal axis is the abrasion rate ratio when the abrasion rate of the surface layer of the cement cured for 7 days in Example ■ in Table 2 is set to 1. 3 is a diagram showing the wear rate of hardened steel slag cured for 7 days in lime water C of No. 3. FIG. FIG. 2A is a simplified diagram of the abrasion resistance testing apparatus, and the opening of FIG. 2 is an enlarged view of sample 7. 1...Frame, 2...Motor 3...
...Saucer, 4...Support frame, 5...
Sample box, 6... Holding arm, 7...
Sample, 8...Weight, 9...Sand, 10.
... Rotation drive mechanism, 11 ... Support shaft, 1
2... Thrust bearing.

Claims (1)

[Claims] 1 A hardened body made by adding water to and mixing raw materials mainly consisting of steel slag, gypsum, and slaked lime, and then injecting this into a formwork to form a hardened body with at least a medium or higher lime content in the surface layer of the hardened body. A method for producing a hardened product using steel slag, which is characterized by curing with water.