Method for manufacturing water-repellent lightweight aerated concrete

Abstract

To provide a method for manufacturing highly water-repellent lightweight aerated concrete. [Solution] In the method for manufacturing water-repellent lightweight aerated concrete, the lightweight aerated concrete is made moist using water so that the moisture content near the surface of the lightweight aerated concrete is 20% or more. Then, water glass is applied to the lightweight aerated concrete. After that, the lightweight aerated concrete is dried. For example, when drying the lightweight aerated concrete, the temperature in the environment where the lightweight aerated concrete is placed is 20 to 80°C, and the relative humidity is 10 to 80%.

Description

[Technical Field]

[0001] This disclosure relates to a method for producing water-repellent lightweight cellular concrete. [Background technology]

[0002] Typical cellular lightweight concrete is a porous building material. Therefore, water easily penetrates its interior. When water penetrates cellular lightweight concrete, cracks and other damage occur, weakening the concrete.

[0003] To suppress weakening due to water intrusion, water-repellent substances are sometimes incorporated into the manufacturing of lightweight aerated concrete (see Patent Document 1). Examples of water-repellent substances include fatty acid salts, siloxane compounds, and silicone resins. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-056069 [Overview of the project] [Problems that the invention aims to solve]

[0005] Conventionally, water repellency is generally imparted using organic water-repellent materials, but there are concerns about the durability of these materials. In one aspect of this disclosure, it is preferable to provide a method for manufacturing water-repellent lightweight aerated concrete in which water repellency is imparted using inorganic materials. [Means for solving the problem]

[0006] One aspect of this disclosure is a method for producing water-repellent cellular concrete, comprising: wetting cellular concrete with water to a moisture content of 20% or more near the surface of the cellular concrete; applying water glass to the cellular concrete; and drying the cellular concrete.

[0007] According to one aspect of this disclosure, the method for producing water-repellent lightweight aerated concrete, it is possible to produce water-repellent lightweight aerated concrete with high water repellency. [Brief explanation of the drawing]

[0008] [Figure 1] This photograph shows the process of measuring the contact angle of a product manufactured using manufacturing example S4. [Modes for carrying out the invention]

[0009] Exemplary embodiments of this disclosure will be described with reference to the drawings. 1. Method for manufacturing water-repellent lightweight aerated concrete (1-1) Process in the method for manufacturing water-repellent lightweight aerated concrete In the method for producing water-repellent cellular concrete described herein, cellular concrete is moistened with water. Then, water glass is applied to the cellular concrete. After that, the cellular concrete is dried. As a result, water-repellent cellular concrete is obtained. Water-repellent cellular concrete is, for example, cellular concrete whose contact angle, as measured by the measurement method described later, is 50° or more. Preferably, the contact angle of the water-repellent cellular concrete is 90° or more.

[0010] (1-2) Lightweight cellular concrete Autoclaved lightweight concrete (ALC), the raw material, can be manufactured, for example, as follows: A slurry containing siliceous raw materials, cement, and lime raw materials is mixed with metallic aluminum powder as a foaming agent and poured into a formwork. After pre-hardening, it is steam-cured in an autoclave.

[0011] Autoclaved lightweight concrete is lightweight and high-strength. Furthermore, it boasts excellent workability, fire resistance, and durability. However, in its raw state, autoclaved lightweight concrete has relatively low water resistance and a brittle surface.

[0012] (1-3) Wet conditions The wet state is preferably one in which the moisture content near the surface of the lightweight aerated concrete is 20% or more. The moisture content is a value measured near the surface of the lightweight aerated concrete. The method for measuring the moisture content will be described later. When the wet state is one in which the moisture content near the surface of the lightweight aerated concrete is 20% or more, the water repellency of the water-repellent lightweight aerated concrete is even higher.

[0013] (1-4) Coating of water glass Water glass can be applied using, for example, a brush or roller. Alternatively, water glass may be sprayed. Water glass is generally a compound represented by the following chemical formula (1). Chemical(1) R2O·nSiO2·xH2O In chemical equation (1), R is an alkali metal. Examples of R include sodium, potassium, and lithium. In chemical equation (1), n ​​is the molar ratio. In water glass, n is generally a real number between 0.5 and 7.5. In chemical equation (1), x is an arbitrary value.

[0014] The water glass contains at least one selected from the group consisting of, for example, sodium silicate solution, potassium silicate solution, and lithium silicate solution. The water glass may contain one of sodium silicate, potassium silicate, and lithium silicate, or a mixture of two or more of them. Examples of mixtures include a mixture of sodium silicate and lithium silicate.

[0015] In water glass, it is preferable that the molar ratio n, represented by the following formula (1), is within the range of 2.0 to 3.8. Formula (1) n=M S / M R In equation (1), M S This is the number of moles of SiO2 contained in water glass. R R is the number of moles of R2O contained in the water glass. R is one or more selected from the group consisting of sodium, potassium, and lithium.

[0016] When the molar ratio n is 2.0 or more, the alkalinity of the water glass is not excessively strong, so the lightweight cellular concrete is difficult to break.

[0017] The specific gravity of the water glass is preferably in the range of 1.1 to 1.3. When the specific gravity of the water glass is in the range of 1.1 to 1.3, the water repellency of the water repellent lightweight cellular concrete is higher.

[0018] By applying the water glass, a water repellent layer containing the water glass is formed. The presence of the water repellent layer can be confirmed by comparing the abundance ratio of alkali metal species in the applied water glass, the abundance ratio of alkali metal species in the silane-based water repellent, or the abundance ratio of alkali metal species in the untreated lightweight cellular concrete. Examples of methods for analyzing the abundance ratio of alkali metal species include using an electron probe microanalyzer (EPMA), energy dispersive X-ray analysis (EDX), or chemical analysis.

[0019] (1 - 5) Step of drying After applying the water glass, when drying the lightweight cellular concrete, the temperature in the environment where the lightweight cellular concrete is placed (hereinafter referred to as the drying environment) is preferably 20 to 80 °C, and the relative humidity in the drying environment is preferably 10 to 80%. When the temperature and relative humidity in the drying environment are within the above ranges, the water repellency of the water repellent lightweight cellular concrete is higher. More preferably, the relative humidity in the drying environment is 10 to 60%. When the relative humidity in the drying environment is 10 to 60%, the water repellency of the water repellent lightweight cellular concrete is particularly high. The drying process can be continued, for example, until the water content rate of the lightweight cellular concrete becomes below a reference value. Examples of the reference value include 40% etc.

[0020] 2. Effects of the manufacturing method of the water repellent lightweight cellular concrete (1A) According to the method for producing water-repellent lightweight aerated concrete of this disclosure, it is possible to produce water-repellent lightweight aerated concrete with high water repellency. When water-repellent lightweight aerated concrete is used as a building material, it is possible to realize a structure with excellent quality over a long period of time. (1B) According to the method for producing water-repellent lightweight cellular concrete of the present disclosure, water-repellent lightweight cellular concrete with high flexural strength can be produced.

[0021] 3. Examples (3-1) Pretreatment of lightweight aerated concrete Commercially available cellular lightweight concrete that does not contain water-repellent agents or cellulose-based materials was prepared. This cellular lightweight concrete was pre-treated. The pre-treatment was as follows: The cellular lightweight concrete was placed in a dryer set to 50°C for 7 days. Next, the cellular lightweight concrete was removed from the dryer and placed in a desiccator to allow the temperature of the cellular lightweight concrete to rise to room temperature. The pre-treated cellular lightweight concrete was used in the manufacturing examples S1 to S16 described later.

[0022] (3-2) Example of manufacturing water-repellent lightweight aerated concrete (i) Manufacturing examples S1~S11, S14~S15 The lightweight aerated concrete was made wet by spraying water onto its surface after pretreatment. In each manufacturing example, the moisture content of the lightweight aerated concrete in the wet state was as shown in Table 1.

[0023] [Table 1]

[0024] The method for measuring moisture content was as follows: First, two electrodes were driven into the surface of the lightweight aerated concrete, and the resistance between the electrodes was measured using a Kaise digital multimeter (model number: KU-1188). The electrodes were driven to a depth of 10 mm. Next, the moisture content was calculated from the measured resistance value.

[0025] Next, water glass was applied to the surface of the lightweight aerated concrete using a brush. The amount of water glass applied was 1.0 kg / m². 2 The type of water glass, molar ratio n, and specific gravity of the water glass in each manufacturing example are shown in Table 1.

[0026] The sodium silicate and potassium silicate contained in the water glass were products manufactured by Fuji Chemical Co., Ltd. (Sodium Silicate No. 1-50, Sodium Silicate No. 2, Sodium Silicate No. 3, Sodium Silicate No. 5, Potassium Silicate No. 1, Potassium Silicate No. 2). The lithium silicate contained in the water glass was a product manufactured by Nissan Chemical Corporation (Lithium Silicate 35). The water glass used in manufacturing example S9 contained sodium silicate and potassium silicate in a weight ratio of 1:1.

[0027] Next, the lightweight aerated concrete was placed in a constant temperature and humidity chamber to dry it. The inside of the constant temperature and humidity chamber is designed to provide a dry environment. In each manufacturing example, the temperature and relative humidity inside the high temperature and humidity chamber were as shown in Table 1.

[0028] Next, the lightweight aerated concrete was removed from the constant temperature and humidity chamber when its moisture content fell below 40%. (ii) Production example S12 The lightweight aerated concrete was made moist by spraying water onto its surface after pretreatment. The moisture content of the lightweight aerated concrete in the moist state was 20% or more.

[0029] Next, apply "Silica Doll 30" (manufactured by Nippon Chemical Industrial Co., Ltd.) to the surface of the lightweight aerated concrete at a rate of 1.0 kg / m². 2 The coating amount was applied as shown. "Silica Doll 30" was colloidal silica with a silica concentration of 15% by weight.

[0030] Next, the lightweight aerated concrete was placed in a constant temperature and humidity chamber to dry it. The temperature inside the chamber was 50°C and the relative humidity was 60%. Two hours after the lightweight aerated concrete was placed in the chamber, it was removed.

[0031] (iii) Production example S16 No further treatment was performed on the lightweight aerated concrete after pretreatment. (3-3) Measurement of Contact Angle The contact angle was measured for each of the products manufactured in manufacturing examples S1 to S16. The method for measuring the contact angle was as follows: 6 μL of pure water was dropped onto the surface of the product. Next, the water droplet was photographed with a digital camera to acquire a digital image.

[0032] Next, the contact radius and contact height of the water droplets are measured in the digital image. The contact angle is calculated from the measured contact radius and contact height. The contact angle is measured at three or more locations on the surface of the product using the method described above, and the average value of these measurements is taken as the contact angle of the product. The results of the contact angle measurement are shown in Table 1.

[0033] In manufacturing examples S1 to S11, water-repellent lightweight aerated concrete with a contact angle of 90° or more was obtained. Figure 1 shows the contact angle being measured for the product manufactured in manufacturing example S4. In the products manufactured in manufacturing examples S12, S15, and S16, the contact angle was 0°, and water droplets penetrated into the product.

[0034] In manufacturing examples S13-S14, we were able to obtain water-repellent lightweight cellular concrete with a contact angle of 69-75°.

[0035] 4. Other Embodiments Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and can be implemented in various modified forms.

[0036] (1) The function of one component in each of the above embodiments may be divided among multiple components, or the function of multiple components may be performed by one component. Also, some of the configurations of each of the above embodiments may be omitted. Also, at least some of the configurations of each of the above embodiments may be added to, substituted for, or otherwise replaced with the configurations of other embodiments.

[0037] (2) In addition to the above-described method for manufacturing water-repellent lightweight cellular concrete, this disclosure can also be implemented in various forms, such as a method for water-repellent treatment of lightweight cellular concrete, and water-repellent lightweight cellular concrete.

[0038] [Technical Concept Disclosed in This Specified Specification] [Item 1] Lightweight aerated concrete is moistened with water so that the moisture content near the surface of the lightweight aerated concrete is 20% or more. Water glass is applied to the aforementioned lightweight aerated concrete. The lightweight aerated concrete is dried. A method for manufacturing water-repellent lightweight aerated concrete. [Item 2] A method for producing water-repellent lightweight aerated concrete as described in item 1, When drying the lightweight aerated concrete, the temperature in the environment where the lightweight aerated concrete is placed is 20-80°C, and the relative humidity in the environment is 10-80%. A method for manufacturing water-repellent lightweight aerated concrete. [Item 3] A method for producing water-repellent lightweight aerated concrete as described in item 1 or 2, The water glass contains at least one selected from the group consisting of sodium silicate solution, potassium silicate solution, and lithium silicate solution. A method for manufacturing water-repellent lightweight aerated concrete. [Item 4] A method for manufacturing water-repellent lightweight aerated concrete described in any one of items 1 to 3, In the aforementioned water glass, the molar ratio n represented by the following formula (1) is in the range of 2.0 to 3.8. The specific gravity of the water glass is within the range of 1.1 to 1.3, Method for producing water-repellent lightweight cellular concrete. Formula (1) n = M S / M R (In the formula (1), M S is the number of moles of SiO2 contained in the water glass, and M R is the number of moles of R2O contained in the water glass. R is one or more selected from the group consisting of sodium, potassium, and lithium.)

Claims

1. Lightweight aerated concrete is moistened with water so that the moisture content near the surface of the lightweight aerated concrete is 20% or more. Water glass is applied to the aforementioned lightweight aerated concrete. The lightweight aerated concrete is dried. A method for manufacturing water-repellent lightweight aerated concrete.

2. A method for producing water-repellent lightweight aerated concrete according to claim 1, When drying the lightweight aerated concrete, the temperature in the environment in which the lightweight aerated concrete is placed is 20 to 80°C, and the relative humidity in the environment is 10 to 80%. A method for manufacturing water-repellent lightweight aerated concrete.

3. A method for producing water-repellent lightweight aerated concrete according to claim 1 or 2, The water glass contains at least one selected from the group consisting of sodium silicate solution, potassium silicate solution, and lithium silicate solution. A method for manufacturing water-repellent lightweight aerated concrete.

4. A method for producing water-repellent lightweight aerated concrete according to claim 1 or 2, In the aforementioned water glass, the molar ratio n represented by the following formula (1) is in the range of 2.0 to 3.

8. The specific gravity of the water glass is in the range of 1.1 to 1.

3. A method for manufacturing water-repellent lightweight aerated concrete. Equation (1) n = M Ｓ / M Ｒ (In the above formula (1), M Ｓ The SiO contained in the water glass is ２ This is the number of moles, M Ｒ R is contained in the water glass. ２ This is the number of moles of O. R is one or more selected from the group consisting of sodium, potassium, and lithium.

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