JPH0566348B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a cured fiber-reinforced cement product, and particularly to a cured fiber-reinforced cement product that has excellent strength, durability, and dimensional stability, and is suitable for use as exterior wall materials, partition materials, etc. . [Conventional technology] Hardened cement is mainly used for concrete structures and concrete products, but in recent years there has been an increasing demand for lightweight, high-strength materials for construction and civil engineering. It has been proposed to increase the strength by mixing alkali-resistant glass fibers (hereinafter referred to as ARG), etc., to reduce weight. For example, in the Japanese Patent Publication No. 60-20351, cement,
A method using a protein-based blowing agent to which water, AGR, and a cationic surfactant are added is disclosed. [Problems to be solved by the invention] However, the conventional method typified by Japanese Patent Publication No. 60-20351 does not provide any advantage. The resulting cured product has problems such as poor strength and durability, high shrinkage rate, and poor dimensional stability. That is, in the conventional cured cement containing bubbles, the diameter of the bubbles contained therein is considerably large, and the strength thereof inevitably becomes low. In addition, conventionally, Portland cement such as ordinary Portland cement (hereinafter referred to as ordinary cement) has been used as a cement raw material for the hardened product, but tricalcium silicate (3CaO,
Calcium silicate hydrate, which is the main product, is produced in the process in which Portland cement, which is mainly composed of calcium silicates such as SiO 2 ) and dicalcium silicate (2CaO・SiO ₂ ) _, is mixed with water and then solidified and hardened. and produces calcium hydroxide. For example, in a cement containing 50% by weight of tricalcium silicate (3CAO・SiO ₂ ) and 25% by weight of dicalcium silicate (2CaO・SiO ₂ ), the stoichiometric amount of calcium hydroxide is calculated based on 100 parts by weight of the original cement. The top 30 parts by weight will be produced. For this reason, hardened cement
PHH is about 12.8 to 13.2, and the hardened cement becomes strongly alkaline. For this reason, AGR mixed into hardened cement is kept in a highly alkaline atmosphere of calcium hydroxide generated from cement for a long time, and even though it is alkali resistant, it erodes over time and the hardened cement Tensile strength, bending strength, impact resistance, etc. will decrease. Furthermore, since ordinary cement generally has a large curing shrinkage rate, conventional hardened cement products have poor dimensional stability due to shrinkage. [Means and effects for solving the problems] The present invention solves the above-mentioned conventional problems and provides a fiber-reinforced cement hardened body having excellent strength, durability, and dimensional stability. The fiber-reinforced cement hardened body of the present invention has an average diameter of
It contains microbubbles of 1.0 mm or less and contains ettringite crystals in an amount of 25% by weight or more. In the fiber-reinforced cement hardened body of the present invention, since there are very few air bubbles, the strength is high. In addition, since it contains a large amount of ettringite crystals and the expansion action during crystal growth makes the shrinkage rate of the hardened cement product very small, it has high dimensional stability.
Furthermore, since a considerable portion of the calcium hydroxide produced during the cement hardening reaction is consumed in the production of ettringite, the alkalinity of the hardened cement is kept low, avoiding deterioration of reinforcing fibers such as glass fibers, and increasing durability. It will be done. The present invention will be explained in more detail below. The air bubbles contained in the hardened cement body of the present invention are minute with an average diameter of 1 mm or less. Figure 1 is a graph showing the relationship between the bubble diameter and strength measurement results of glass fiber reinforced cement hardened bodies manufactured under the same conditions except that the bubble diameter was changed. , it is recognized that the strength decreases quite rapidly. Also, the average diameter is 0.2mm
It is also recognized that the strength becomes even higher when the strength is lower than that. For these reasons, in the present invention, the average diameter of the bubbles is 1 mm or less, preferably 0.2 mm.
It is considered to be less than mm. Note that the smaller the average diameter of the bubbles, the higher the strength of the hardened cement body, but if it becomes too small, the toughness of the hardened cement body against bending or shearing may decrease. This is because the grip of the reinforcing fibers by the matrix part becomes stronger, and the deformation of the hardened cement when bending or shearing loads are applied is directly propagated to the reinforcing fibers, and a large load is locally applied to the reinforcing fibers. It is surmised that this is so that it becomes like this. For these reasons, in the present invention, it is particularly preferable that the average diameter of the bubbles contained in the hardened cement body is 0.05 to 0.2 mm. Such a hardened cement product is produced by mixing air milk obtained by mixing a polymeric surfactant-based foaming agent and water with a calcium silicate-auin-slag-based low alkaline cement, water, and a water reducing agent. It can be easily manufactured by mixing the obtained cement paste, adding reinforcing fibers to the obtained mixture, kneading it, shaping it, and then curing it. In this production, it is preferable to use a polymeric surfactant-based foaming agent as the foaming agent and to mix this foaming agent and water to prepare air milk. As the polymeric surfactant-based foaming agent, alkenyl succinic acid is preferable, and when using it, it is preferable to add lime when preparing air milk and saponify the alkenyl succinic acid with an alkali. When preparing air milk, the mixing ratio of foaming agent and water is 0.01 to 2 parts by weight of foaming agent to 20 parts by weight of water.
~30 parts by weight, preferably 22 to 26 parts by weight of water to 1 part by weight of foaming agent. When lime is mixed and used, the proportion thereof is preferably 0.1 to 2 parts by weight, particularly 0.3 to 1.0 parts by weight, based on the amounts of the above-mentioned foaming agent and water. Note that lime is added to supply Ca ²⁺ ions for alkali saponification, so any material that supplies Ca ²⁺ ions may be used instead, such as cement. In order to obtain air milk by mixing and foaming a foaming agent, water, and if necessary, lime, it is possible to mix and foam the mixture well by a batch method using a high-speed mixer. In addition, more stable bubbles can be obtained by using a continuous foaming machine using high-pressure air. Note that the diameter of the bubbles is determined by the type of foaming agent and the diameter of the particles packed in the foaming machine. For example, the above-mentioned alkenyl succinic acids generate small-diameter bubbles. Furthermore, protein-based foaming agents, which are known, generate relatively large-diameter bubbles. In addition, if the particle size packed into the foaming machine is 1 to 2 mm, 0.1 to 0.2
Bubbles with a diameter of about mm are generated, and the packed particle size is 5~
If it is 10 mm, bubbles of about 0.2 to 0.5 mm will be generated. The air milk preferably has a specific gravity ρ of 0.02 to 0.10, particularly ρ of 0.04 to 0.06. Separately, a cement paste is prepared by mixing calcium silicate-auin-slag-based low-alkali cement, water, and a water reducing agent. The cement raw materials used in the present invention include:
Calcium silicate-auin-slag type low alkaline cement is suitable, for example, Portland cement clinker 20-20 whose main component is calcium silicate such as tricalcium silicate (3CaO・SiA ₂ ) and dicalcium silicate (2CaO・SiO ₂ ). 70% by weight, calcium sulfoaluminate 3CaO・3Al ₂ O ₃・CaSO ₄
The composition is 10 to 40% by weight of clinker mainly composed of 10 to 40% by weight of anhydrite or dihydrite, 20 to 60% by weight of granulated blast furnace slag or fly ash, and (3Al ₂ O ₃ + 1.5SiO ₂ )/(CaO- _SO3 ) in a molar ratio of 1.0 to 1.5. As such cement, Chichibu Cement Co., Ltd.
Chichibu GRC Cement manufactured by Chichibu is commercially available.
Chichibu GRC cement contains 3CaO・SiO ₂ , 2CaO・
It is a high-alumina, low-lime type cement whose main components are SiO ₂ , 3CaO・3Al ₂ O ₃・CaSO ₄ and granulated blast furnace slag, and its chemical composition is compared with that of ordinary cement as shown in Table 1. It is.

[Table] Furthermore, as the water reducing agent, a polyalkylarylsulfonic acid type water reducing agent is preferable, and a naphthalene sulfonic acid formalin condensate type water reducing agent is particularly optimal. When preparing cement paste, the mixing ratio of low alkaline cement, water and water reducing agent should be
For 100 parts by weight, it is suitable to use 25 to 40 parts by weight, preferably 30 to 33 parts by weight, and 0.2 to 5 parts by weight, preferably 0.5 to 2 parts by weight, of the water reducing agent. The cement paste preferably has a specific gravity ρ of about 2. Next, the air milk and cement paste are mixed to prepare a lightweight cement paste.
At this time, it is preferable to adjust the mixing ratio of air milk and cement paste so that the resulting lightweight cement paste has a specific gravity ρ of 1.0 to 1.5. Next, reinforcing fibers are added to this lightweight cement paste and thoroughly kneaded using a mixer or the like. As reinforcing fibers, glass fibers such as ARG, asbestos,
Carbon fibers and other organic fibers can be used. When using glass fiber as the reinforcing fiber, the fiber length is 3 to 50 mm, preferably 12 to 24 mm.
mm, and the amount added is preferably 2 to 10% by weight, preferably 3 to 5% by weight, based on the lightweight cement paste. If the fiber length of the glass fiber used is less than 3 mm, the reinforcing effect will be low;
If it exceeds 50 mm, poor mixing is likely to occur. Further, if the proportion of glass fiber added is less than 2% by weight, the reinforcing effect is low, and if it exceeds 10% by weight, poor mixing tends to occur. In the present invention, when glass fiber is used as the reinforcing fiber, the effect of improving the durability of the obtained cured product is remarkable. After adding reinforcing fibers to lightweight cement paste and thoroughly kneading it, it is molded according to conventional methods.
Take care of yourself. Molding is performed by pouring uncured lightweight cement paste containing glass fiber into the desired formwork, and curing at a temperature of 10 to 60℃, preferably 30 to 50℃.
It is preferable to carry out the treatment at ℃ and humidity of 60% or more for 5 hours or more. The cement molded body hardened by curing is further cured after being demolded. In this case, the curing temperature is 15℃.
It is preferable to carry out the above process for 7 days or more at a humidity of 60% or more. This makes it possible to obtain fiber-reinforced cement products that are lightweight, have excellent strength, durability, and dimensional stability, have good productivity, and are free from unpleasant odors during manufacturing. In addition, in the present invention, in order to further reduce the alkalinity of the cement raw material,
The cement raw material can be replaced with silica fume within a range of % by weight or less. If the amount of silica fume substituted exceeds 20% by weight, the strength of the resulting hardened cement product decreases, which is not preferable. In the present invention, calcium silicate is used as a cement raw material.
When Auin-slag-based low alkaline cement is used, calcium hydroxide and Auin (3CaO・3Al ₂ O ₃・
Because it reacts with CaSO ₄ ) to produce ettringite, it has low alkalinity and low shrinkage due to drying.
Moreover, the curing speed is fast. Therefore, when glass fibers are used as reinforcing fibers for cement, the cement hardly erodes the glass fibers, the reinforcing effect of the glass fibers lasts, and the mechanical properties such as the strength of the hardened cement material hardly change over time. Become something. The effect is particularly great when alkali-resistant glass fibers are used. It also has excellent dimensional stability and extremely high productivity. Furthermore, when a polymeric surfactant-based foaming agent is used to produce the hardened cement product of the present invention, the defoaming effect will not occur even when mixed with a water-reducing agent. The amount of water in the cement paste is significantly lower than usual, making it possible to obtain a hardened cement product with stable specific gravity and high strength. Although the details of the reason why polymeric surfactant-based foaming agents do not show antifoaming effects and are stable even when mixed with water-reducing agents are not clear, the constituent molecules of polymeric surfactant-based foaming agents Certain alkenyl succinic acids have a large number of hydrophilic groups in their molecules and exhibit strong surface activity, and at the same time, this produces insoluble calcium salts through interaction with Ca ²⁺ ions in cement paste or added lime. This is thought to be because the bubbles become stable. [Examples] The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. Example 1 Alkenyl succinic acid foaming agent (Fineform N, manufactured by Misawa Ceramic Chemical Co., Ltd.),
Mix and foam water and lime in a mixer, specific gravity 0.05
18.4 g (36.8 cc) of air milk adjusted to A lightweight cement paste was obtained by mixing 1 kg (500 c.c.) of cement paste adjusted to a specific gravity of 2.0. This lightweight cement paste has a fiber length of 12 mm.
3% by weight of ARG was added and thoroughly kneaded. This was poured into a mold, cured at 40℃ and 100% humidity for 15 hours, then removed from the mold, and further cured at 20℃ and 80% humidity for 28 days, resulting in a specific gravity of 1.3, an average cell diameter of 0.1mm, and an ettringite crystal content. A 30wt% glass fiber reinforced cement hardened body was obtained. The bending strength of this cured product was measured at 120
It was Kg/ ^cm2 . Moreover, the shrinkage rate was 0.06%. Example 2 and Comparative Example 1 In addition to the alkenyl succinic acid foaming agent used in Example 1, a protein-based foaming agent (Formics, manufactured by Misawa Ceramic Chemical Co., Ltd.) was used, and foaming conditions were adjusted. We prepared hardened cement bodies with different average cell diameters. Other conditions are the same as in Example 1. The specific gravity of the obtained hardened cement body is 1.3.
Moreover, the measurement results of bending strength are as shown in FIG. From FIG. 1, it is clear that when the average diameter of the bubbles becomes 1 mm or less, especially 0.2 mm or less, the bending strength increases significantly. [Effects of the Invention] As detailed above, the fiber-reinforced cement hardened body of the present invention has a small cell diameter and high strength. In addition, it contains a large amount of ettringite, has excellent dimensional stability, is low in alkali, and exhibits extremely little deterioration even when glass fiber is used as a reinforcing fiber, and has excellent durability.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between average cell diameter and bending strength.

Claims (1)

[Scope of Claims] 1. A hardened fiber-reinforced cement body containing microbubbles with an average diameter of 1.0 mm or less and containing 25% by weight or more of ettringite crystals. 2. The fiber-reinforced cement hardened body according to claim 1, which is a hardened body of calcium silicate-auin-slag based low alkaline cement. 3. The fiber-reinforced cement hardened body according to claim 1 or 2, which has a specific gravity of 1.0 to 1.5. 4. The fiber-reinforced cement hardened body according to any one of claims 1 to 3, wherein the reinforcing fibers are glass fibers.