Cement hardening accelerator and method for manufacturing the same

Abstract

To provide a cement hardening accelerator and a method for producing the same, which uses calcium silicate-based materials such as waste as raw materials, is low-cost, and has a high hardening acceleration effect. [Solution] Made of calcium silicate material, with a specific surface area S determined by a Brain air permeation device of 17,000 cm² 2 A cement hardening accelerator and a method for producing the same, having a concentration of 1 / g or more.

Description

[Technical Field]

[0001] The present invention relates to a cement hardening accelerator and a method for producing the same. [Background technology]

[0002] In recent years, from an environmental protection perspective, there has been a strong desire to reduce industrial waste. The disposal of waste materials generated in large quantities from construction sites and demolition sites, particularly calcium silicate-based materials such as ALC (autoclaved lightweight concrete) and calcium silicate boards, which are widely used as building materials, has become a major issue.

[0003] Calcium silicate-based materials have few effective reuse methods, and although a small portion is crushed and recycled for use as roadbed material in landfills, the majority is disposed of as industrial waste. Given the increasing strain on industrial waste disposal facilities in recent years, there is a strong desire to reduce the amount of calcium silicate-based waste from demolished buildings and other structures.

[0004] As a method for reusing calcium silicate waste, Patent Document 1 discloses a method of finely pulverizing calcium silicate waste by wet mechanochemical treatment, thereby amorphousizing some or all of the calcium silicate minerals and using them as a cement hardening accelerator. However, when high-energy treatment such as mechanochemical treatment is required, it is difficult to scale up the equipment, leading to increased costs during setup and operation. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2004-82061 [Overview of the project] [Problems that the invention aims to solve]

[0006] Therefore, the present invention aims to provide a cement hardening accelerator and a method for producing the same, which uses calcium silicate-based materials such as waste as raw materials, is low-cost, and has a high hardening acceleration effect. [Means for solving the problem]

[0007] The above objective is achieved by the present invention as described below. That is, the embodiments of the present invention are as follows.

[0008] <1> It is made of calcium silicate-based material, and its specific surface area S, determined by a Brain air permeability device, is 17,000 cm². 2 A cement hardening accelerator that is 1 / g or more.

[0009] <2> The shape factor F, which can be calculated from the specific surface area S and the area-average particle diameter r using the following formula (1), is 9 or greater. <1> A cement hardening accelerator as described in [the document]. F = S / 4πr 2 …Formula (1)

[0010] <3> Furthermore, it is a slurry containing water. <1> A cement hardening accelerator as described in [the document].

[0011] <4> <1> A method for producing a cement hardening accelerator described in [the relevant text], A method for producing a cement hardening accelerator, comprising a grinding step of grinding a calcium silicate-based material.

[0012] <5> The aforementioned calcium silicate material is calcium silicate waste material. <4> A method for producing a cement hardening accelerator as described above.

[0013] <6> The calcium silicate material is at least one waste material selected from the group consisting of ALC panels, calcium silicate boards, and siding boards. <4> A method for producing a cement hardening accelerator as described above.

[0014] <7> The method for producing a cement hardening accelerator according to <4>, wherein the pulverization step includes a wet pulverization operation.

[0015] <8> The method for producing a cement hardening accelerator according to <7>, wherein the water ratio (water / calcium silicate-based material) (mass basis) in the pulverization step is in the range of 1.2 or more and 9.0 or less.

Advantages of the Invention

[0016] According to the present invention, it is possible to provide a cement hardening accelerator made from a calcium silicate-based material such as waste, etc., and having a high hardening acceleration effect while being low-cost, and a method for producing the same.​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0020] Furthermore, in the curing accelerator according to this embodiment, it is preferable that the shape factor F (hereinafter sometimes simply referred to as "shape factor F"), which is obtained from the specific surface area S and the area-average particle diameter r using the following formula (1), is 9 or more. F = S / 4πr 2 …Formula (1)

[0021] (Calcium silicate-based materials) In the hardening accelerator according to this embodiment, the calcium silicate material used as a raw material may be calcium silicate waste material as waste, or calcium silicate minerals used as a resource or contained in calcium silicate waste material. In view of the intent to effectively utilize waste, it is preferable that the calcium silicate material used as a raw material is calcium silicate waste material.

[0022] Calcium silicate waste materials include, for example, ALC panels, calcium silicate boards (also called "calcium silicate boards"), or siding boards, which are generated from construction or demolition sites of buildings. In other words, it is preferable that the calcium silicate material used as a raw material be at least one of the waste materials selected from the group consisting of ALC panels, calcium silicate boards, and siding boards.

[0023] The calcium silicate minerals contained in these calcium silicate waste materials include crystalline minerals such as tobermorite and xonotlite, as well as low-crystalline or amorphous minerals of the CaO-SiO2-H2O system (generally referred to as CSH).

[0024] Calcium silicate-based materials may contain calcium carbonate, calcium sulfate, calcium hydroxide, aluminum hydroxide, etc., in addition to calcium silicate. They may also contain other impurities, such as organic fibers like pulp and plant roots, inorganic fibers like wollastonite, rebar scraps, and iron powder.

[0025] In this embodiment, materials with a calcium silicate content of 50% or more by mass are referred to as "calcium silicate-based materials" and are used in the manufacturing method described later. The calcium silicate content in the calcium silicate-based materials is preferably 60% or more by mass, more preferably 70% or more, and even more preferably 80% or more.

[0026] Accordingly, the curing accelerator according to this embodiment has a calcium silicate content of 50% or more by mass, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more.

[0027] In this embodiment, the curing accelerator is in the form of a powder made of calcium silicate-based material, or a slurry containing water. As will be described later, the curing accelerator according to this embodiment is preferably obtained by wet grinding, in which case the slurry after grinding can be used as the curing accelerator according to this embodiment.

[0028] The hardening accelerator according to this embodiment can accelerate the hardening reaction of cement by being added to various cement compositions (compositions containing at least cement and water). There are no particular limitations on the cement to which it can be applied, and examples include Portland cement such as ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, and moderate-heat Portland cement, as well as white cement, jet cement, blast furnace cement, fly ash cement, alumina cement, etc.

[0029] (Specific surface area S) The specific surface area S defined in this embodiment is determined by a Blaine air permeation device and is also referred to as the "Blaine value." The Blaine air permeation device used is the one specified in JIS R5201, section 8.1.1, and the specifications and conditions for the device, measurement method, etc., conform to JIS R5201.

[0030] In this embodiment, the specific surface area S is 17,000 cm². 2 / g or more, preferably 17500 cm 2 / g or more, more preferably 18000 cm 2 / g or more. By appropriately increasing the specific surface area S, a curing accelerator with a high curing acceleration effect can be obtained. Although its mechanism of action is not clear, it is presumed that the unevenness on the particle surface is related to the curing acceleration effect of cement.

[0031] Fig. 1 shows a graph representing the degree of curing when the curing accelerators of this embodiment with different specific surface areas S and those for comparison are actually added to cement. The graph in Fig. 1 has the specific surface area S on the horizontal axis and the measurement result of the load (N) 2.5 hours after the addition of the curing accelerator (curing time 2.5 hours) on the vertical axis. The measurement of the load (N) conforms to the conditions and methods of the examples described later.

[0032] As a specific test method, after kneading 100 g of ordinary Portland cement with 60 ml of water, 5 g of the curing accelerator to be verified was added and thoroughly mixed, and then it was cured in an environment of 40°C for 2.5 hours, and then the load (N) was measured. As can be seen from the graph in Fig. 1, a strong correlation was observed between the specific surface area S and the load (N). When the specific surface area S was 17000 cm 2 / g or more, the load greatly exceeded 200 N, and a high curing acceleration effect was confirmed. There is no particular limitation on the upper limit of the specific surface area S. The higher the value, the higher the expected curing acceleration effect. In practice, however, about 25000 cm 2 / g is the upper limit.

[0033] (Shape factor F) The shape factor F defined in this embodiment is obtained from the following formula (1), and it is a numerical value of the ratio of the actual specific surface area S (the numerator in formula (1)) to the surface area of a sphere (the denominator in formula (1)) obtained from the area average particle size of the particles. F = S / 4πr 2 …Formula (1)

[0034] A larger shape factor F indicates that the surface irregularities of the particle are more pronounced, and that it deviates from a perfect sphere. The shape factor F is preferably 9 or greater, more preferably 10 or greater, and even more preferably 11 or greater.

[0035] Figure 2 shows graphs illustrating the degree of hardening when hardening accelerators with different shape coefficients F in this embodiment and for comparison were actually added to cement. In the graph in Figure 2, the horizontal axis represents the shape coefficient F, and the vertical axis represents the measured load (N) 2.5 hours after the addition of the hardening accelerator (curing time 2.5 hours). The measurement of the load (N) was carried out according to the conditions and methods of the embodiment described later.

[0036] The specific test method is the same as for the specific surface area S. As can be seen from the graph in Figure 2, a strong correlation was observed between the shape factor F and the load (N). When the shape factor F was 9 or higher, the load significantly exceeded 200N, confirming a high hardening acceleration effect. There is no particular upper limit to the shape factor F; the larger the value, the greater the hardening acceleration effect that can be expected, but in practice, the upper limit is around 30.

[0037] [Method for manufacturing cement hardening accelerator] The method for producing a cement hardening accelerator according to this embodiment (hereinafter sometimes simply referred to as the "manufacturing method") is a method for producing the hardening accelerator described above, and includes a grinding step of grinding a calcium silicate-based material.

[0038] The calcium silicate-based material used is as described in the section on [Cement Hardening Accelerators] (hereinafter referred to as the "Hardening Accelerators section"), and considering recyclability, it is preferable to use calcium silicate-based waste material. Specifically, it is preferable to use at least one waste material selected from the group consisting of ALC panels, calcium silicate boards, and siding boards.

[0039] In the manufacturing method according to this embodiment, the grinding process is not particularly limited as long as it can achieve the specific surface area S required for the hardening accelerator according to the embodiment, and can be either a wet grinding operation or a dry grinding operation. However, a wet grinding operation is suitable in this embodiment because it is possible to increase the specific surface area S while performing relatively gentle grinding. Wet grinding is advantageous in that it does not involve powerful grinding like the mechanochemical treatment described in Patent Document 1, so it is possible to use larger equipment, and running costs (power consumption and consumption of grinding media) can be reduced, thus achieving low costs. Furthermore, wet grinding is also advantageous in that it can suppress noise compared to dry grinding.

[0040] In the manufacturing method according to this embodiment, a suitable wet grinding step involves placing the calcium silicate material to be ground and the grinding media into water, and grinding under relatively gentle rotational conditions using, for example, a rolling mill as the grinder. Specific rotational conditions include, for example, grinding at a range of approximately 30 to 100 rpm (revolutions / minute). In addition to rolling mills, other grinders such as pot mills, tube mills, conical mills, vibratory mills, centrifugal mills, planetary mills, tower mills, agitated tank mills, and colloidal mills can be used.

[0041] For the grinding media, any common material can be used, such as iron balls, alumina balls, zirconia balls, silicon carbide balls, or stainless steel balls. The diameter of the grinding media can be appropriately selected from a range of approximately 0.5 mmφ to 100 mmφ. The amount of grinding media to be added should be about 10 to 30% of the container capacity.

[0042] In the grinding process, the water ratio (water / calcium silicate material) (by mass) is preferably within the range of 1.2 to 9.0, more preferably within the range of 1.3 to 8.5, and even more preferably within the range of 1.4 to 8.0. If the water ratio is too low, the calcium silicate material will not disperse well in the grinder container, and it is presumed that efficient grinding will not occur. On the other hand, if the water ratio is too high, the grinding efficiency will decrease.

[0043] The calcium silicate-based material pulverized in the pulverization process can be used as a slurry or dried to obtain the hardening accelerator according to this embodiment.

[0044] Furthermore, if the calcium silicate material used is large in area or in large chunks, it is preferable to perform a strong coarse grinding operation, such as dry grinding (using a roller mill, etc.), prior to the final grinding operation to obtain the hardening accelerator, such as wet grinding (hereinafter referred to as the "final grinding operation"). The conditions for the coarse grinding operation are preferably stronger than those for the final grinding operation, and there are no particular restrictions on the grinding method, grinding equipment, or grinding conditions. Of course, in the grinding process, it is also possible to obtain the final hardening accelerator by performing only the final grinding operation without performing the coarse grinding operation. [Examples]

[0045] Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

[0046] (Example 1) In a 300ml plastic bottle, 10g of waste ALC panels (dry-ground to 0.35mm or less using a vertical roller mill) and 15g of water (water ratio 1.5) were added as calcium silicate material, along with 5mmφ zirconia spheres as grinding media. Wet grinding was then performed in a rolling mill at 85rpm for 1 hour. The grinding operation was carried out at room temperature (20°C).

[0047] The slurry after grinding was sieved to separate it from the zirconia spheres. Approximately 10 ml of the obtained slurry was filtered by suction, and then dried at 105°C for 2 hours to obtain the powdered curing accelerator of Example 1. The specific surface area S of the obtained curing accelerator powder of Example 1 was determined using a Blaine air permeation analyzer in accordance with JIS R5201. The area-average particle diameter r of the curing accelerator powder of Example 1 was determined using a particle size distribution and particle shape analyzer (SYNC, manufactured by Microtrac-Bell Co., Ltd.), and the shape coefficient F was calculated from these values ​​using the previously described formula (1). These results are summarized in Table 1 below.

[0048] (Example 2) In Example 1, the curing accelerator for Example 2 was obtained in the same manner as in Example 1, except that the amount of water used in the wet grinding process was changed to 40 g (water ratio 4). The specific surface area S and shape coefficient F of the obtained curing accelerator powder for Example 2 were determined in the same manner as in Example 1. These results are summarized in Table 1 below.

[0049] (Example 3) In Example 1, the curing accelerator for Example 3 was obtained in the same manner as in Example 1, except that the amount of water used in wet grinding was changed to 60 g (water ratio 6). The specific surface area S and shape coefficient F of the obtained curing accelerator powder of Example 3 were determined in the same manner as in Example 1. These results are summarized in Table 1 below.

[0050] (Example 4) In Example 1, the curing accelerator for Example 4 was obtained in the same manner as in Example 1, except that the amount of water used in wet grinding was changed to 13 g (water ratio 1.3). The specific surface area S and shape coefficient F of the obtained curing accelerator powder of Example 4 were determined in the same manner as in Example 1. These results are summarized in Table 1 below.

[0051] (Comparative Example 1) Using the same calcium silicate-based material as in Example 1, the reinforcing bars were recovered from an ALC panel using a vertical roller mill. The remaining base material was then dry-ground until it passed through a 0.35 mm sieve to obtain the hardening accelerator of Comparative Example 1. The specific surface area S and shape coefficient F of the obtained hardening accelerator powder of Comparative Example 1 were determined in the same manner as in Example 1. These results are summarized in Table 1 below.

[0052] (Comparative Example 2) Comparative Example 2's hardening accelerator was obtained in the same manner as in Example 1, except that the amount of water used in wet grinding was changed to 10 g (water ratio 1). The specific surface area S and shape coefficient F of the obtained Comparative Example 2 hardening accelerator powder were determined in the same manner as in Example 1. These results are summarized in Table 1 below.

[0053] (Comparative Example 3) Comparative Example 3's curing accelerator was obtained in the same manner as in Example 1, except that the amount of water used in wet grinding was changed to 100 g (water ratio 10). The specific surface area S and shape coefficient F of the obtained Comparative Example 3's curing accelerator powder were determined in the same manner as in Example 1. These results are summarized in Table 1 below.

[0054] (Cement hardening test) A cement hardening test was conducted to evaluate the hardening acceleration properties of the hardening accelerators obtained in Examples 1-3 and Comparative Examples 1-3 by actually adding them to cement compositions. Specifically, 100g of ordinary Portland cement and 60ml of 20°C water were mixed in a 300ml poly cup, and then 5g of each hardening accelerator under evaluation was added and mixed thoroughly to obtain the hardening compositions of Examples 1-3 and Comparative Examples 1-3.

[0055] Furthermore, as a reference example, a hardening composition was obtained in the same manner as in Examples 1-3 and Comparative Examples 1-3, except that 2g of silica and 1g of gypsum were added instead of 5g of hardening accelerator, and the amount of ordinary Portland cement was increased by 2g to 102g.

[0056] The curing compositions obtained from Examples 1-3, Comparative Examples 1-3, and the standard example were cured at 40°C for 2.5 hours to obtain test samples (80 mm in diameter x 20 mm in thickness). For each cured sample, the load was measured by using a push-pull gauge and a 15 mm diameter jig, pressing the jig 5 mm perpendicularly to the center of the sample's surface, and confirming the maximum load. The results are summarized in Table 1 below.

[0057] (Evaluation of cement hardening test) The load B of the standard sample (without curing accelerator added) was used as the baseline (100%), and the ratio of the load x of each sample in Examples 1-3 and Comparative Examples 1-3 to this baseline (x / B) was evaluated as the curing acceleration ratio. This curing acceleration ratio is an indicator showing the degree of curing achieved in a shorter time (2.5 hours) by adding the curing accelerator compared to the case without curing accelerator. The results are summarized in Table 1 below.

[0058] [Table 1]

[0059] As can be seen from the results in Table 1 above, the specific surface area S is 17,000 cm². 2 The curing accelerators of Examples 1-3, which are 17,000 cm² or more, 2 Compared to Comparative Examples 1-3, which had a curing acceleration effect of less than 300%, the curing acceleration ratio was significantly higher, and curing occurred much earlier, well exceeding 300%. Furthermore, the curing accelerators of Examples 1-3, which exhibited this high curing acceleration effect, had a shape factor F in the range of 9-29.

Claims

1. It is made of calcium silicate-based material, and its specific surface area S, determined by a Brain air permeability device, is 17,000 cm². ２ / g or more, A cement hardening accelerator wherein the calcium silicate-based material is calcium silicate-based waste material.

2. The cement hardening accelerator according to claim 1, wherein the shape coefficient F, which can be obtained from the specific surface area S and the area-average particle diameter r using the following formula (1), is 9 or more. F = S / 4πr ２ …Formula (1)

3. Furthermore, the cement hardening accelerator according to claim 1 is in the form of a slurry containing water.

4. A method for producing a cement hardening accelerator according to claim 1, The process includes a grinding step for grinding calcium silicate-based materials. A method for producing a cement hardening accelerator, wherein the calcium silicate-based material is calcium silicate-based waste material.

5. The method for producing a cement hardening accelerator according to claim 4, wherein the calcium silicate material is at least one waste material selected from the group consisting of ALC panels, calcium silicate boards, and siding boards.

6. The method for producing a cement hardening accelerator according to claim 4, wherein the grinding step includes a wet grinding operation.

7. A method for producing a cement hardening accelerator according to claim 6, wherein the water ratio (water / calcium silicate-based material) (by mass) in the grinding step is within the range of 1.2 to 9.0.

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