High-strength mortar composition and high-strength mortar

Abstract

To provide a high-strength mortar composition and a high-strength mortar which exhibit superior water compatibility even with a low water-to-binder ratio, have superior fluidity, and demonstrate high compressive strength.SOLUTION: A high-strength mortar composition comprises a binder composed of cement and siliceous fine powder, and a fine aggregate. The siliceous fine powder has a SiO2 content of 96 mass% or more, a BET specific surface area of 5 to 16 m2 / g, and an ignition loss of 1.0 mass% or less. The content of the siliceous fine powder is 1 to 35 pts.mass relative to 100 pts.mass of the binder.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a high-strength mortar composition and a high-strength mortar.

Background Art

[0002] In recent years, the quality of concrete used in civil engineering and building structures has been improved to be high-performance and high-strength, and high fluidity and high strength development are required for the mortar used in each member. Generally, a method of using silica fume to increase the strength of concrete and mortar is known. When silica fume is added to concrete or mortar, the filling property can be improved and the water-cement ratio for obtaining a predetermined fluidity can be reduced by the ball bearing effect. In addition, silica fume exhibits high pozzolanic activity, and the high strength of the added mortar and concrete can be achieved by the micro filler effect.

[0003] As a method for manufacturing high-strength mortar and concrete, there is known a method using silica fume containing 90% or more of SiO2 as an admixture and having a water-binder ratio of 25% or less (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since silica fume is composed of ultrafine particles, it tends to aggregate, and there is a problem that its dispersibility is poor in mortar and concrete. Depending on the silica fume used, a predetermined fluidity may not be obtained, and if admixtures such as water reducers are excessively added to ensure fluidity, material separation and hardening inhibition may occur. Furthermore, when the water-binder ratio is small, although high strength can be obtained, the water affinity is poor (it takes time for the water and the material to mix when kneading with water), and the kneading time until a predetermined fluidity is obtained may be long or the fluidity may not be obtained.

[0006] Therefore, an object of the present invention is to provide a high-strength mortar composition and a high-strength mortar that have good water affinity, excellent fluidity, and exhibit high compressive strength even when the water-binder ratio is small.

Means for Solving the Problems

[0007] As a result of intensive studies by the present inventors on the above problems, by using a siliceous fine powder having a high SiO2 content, a small loss on ignition, and a specific BET specific surface area, a high-strength mortar composition and a high-strength mortar that have good water affinity, excellent fluidity, and exhibit high compressive strength can be obtained even when the water-binder ratio is small.

[0008] That is, the present invention is as follows. [1] A mortar composition containing a binder composed of cement and siliceous fine powder and fine aggregate, wherein the siliceous fine powder has a SiO2 content of 96% by mass or more, a BET method specific surface area of 5 to 16 m 2 / g, and a loss on ignition of 1.0% by mass or less, and the content of the siliceous fine powder is 1 to 35 parts by mass with respect to 100 parts by mass of the binder, a high-strength mortar composition. [2] The high-strength mortar composition according to [1], further containing a water reducer. [3] A high-strength mortar containing the high-strength mortar composition according to [1] or [2] and water, wherein the water content is 20 to 40 parts by mass with respect to 100 parts by mass of the binder. [4] When hardened, in accordance with the Japan Society of Civil Engineers Standard JSCE-G 505-2018 "Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens (Draft)", the compressive strength at 28 days of age measured under an environment of 20°C is 100 N / mm 2 or more, the high-strength mortar according to [3].

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a high-strength mortar composition and a high-strength mortar that have good water affinity, excellent fluidity, and high compressive strength even when the water binder ratio is small.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, a preferred embodiment of the present invention will be described. Regarding the description of the content in this specification, it is in terms of solid content conversion and anhydride conversion, and for those containing liquids, the moisture contained therein is included in the water content.

[0011] The high-strength mortar composition of this embodiment includes a binder composed of cement and silica fine powder and fine aggregate.

[0012] The binder according to this embodiment consists of two components, cement and silica fine powder.

[0013] Various cements can be used. For example, various Portland cements such as ordinary, early-strength, ultra-early-strength, low-heat, and medium-heat Portland cements; blended cements containing blast furnace slag, fly ash, or silica fume; eco-cements; rapid-hardening cements, etc. can be mentioned. As the cement, ordinary Portland cement or early-strength Portland cement is preferred from the viewpoint of being easily compatible with both strength development and improvement of fluidity. The cement may be used alone or in combination of two or more.

[0014] Siliceous fine powder is a material mainly composed of SiO2, including those obtained as by-products when producing ferrosilicon or metallic silicon, those of zirconia origin obtained as by-products when producing fused zirconia, those synthesized from silicon or silicon dioxide, and the like.

[0015] The siliceous fine powder according to this embodiment has an SiO2 content of 96% by mass or more, a BET specific surface area of 5 to 16 m 2 / g, and a loss on ignition of 1.0% by mass or less.

[0016] The SiO2 content of the siliceous fine powder is 96% by mass or more. If the SiO2 content of the siliceous fine powder is outside the above range, the amount of impurities increases and the fluidity decreases. The SiO2 content of the siliceous fine powder is preferably 97% by mass or more, more preferably 98% by mass or more, and still more preferably 99% by mass or more. The SiO2 content of the siliceous fine powder may be less than 100% by mass. If the SiO2 content of the siliceous fine powder is within the above range, the material and water are more compatible, and the fluidity tends to be excellent. The SiO2 content of the siliceous fine powder can be measured by a fluorescent X-ray analyzer.

[0017] The BET specific surface area of the siliceous fine powder is 5 to 16 m 2 / g. If the BET specific surface area of the siliceous fine powder is less than 5 m 2 / g, material separation is likely to occur. If it exceeds 16 m 2 / g, the water compatibility when adding water and kneading is poor, and a material with good fluidity cannot be obtained. From the viewpoint of better water compatibility and easier obtaining of good fluidity, the BET specific surface area of the siliceous fine powder is preferably 7 to 15.5 m 2 / g, more preferably 8 to 15 m 2 / g, and still more preferably 10 to 14.8 m 2 / g. The BET specific surface area can be measured by the nitrogen adsorption method or the like.

[0018] The loss on ignition of the silica fine powder is 1.0% by mass or less. When the loss on ignition exceeds 1.0% by mass, the amount of water reducing agent adsorbed by unburned carbon increases, resulting in a decrease in fluidity. From the viewpoint of easily obtaining good fluidity and further improving the finish during curing, the loss on ignition of the silica fine powder is preferably 0.8% by mass or less, more preferably 0.6% by mass or less, and still more preferably 0.4% by mass or less. The loss on ignition can be measured by subjecting the sample to strong heating in an electric furnace adjusted to 1000 °C for 15 minutes in accordance with JIS A 6207:2016 "Silica Fume for Concrete" and determining the weight change before and after the strong heating.

[0019] The pH of the silica fine powder is preferably 2 to 6, more preferably 2 to 5.5, and still more preferably 2 to 5. If the pH of the silica fine powder is within the above range, the dispersibility of the silica fine powder is good, and the water affinity when water is added and kneaded is likely to be improved. The pH of the silica fine powder can be measured using a 50% by mass slurry obtained by stirring water and the silica fine powder in an environment of 20 °C.

[0020] The content of the silica fine powder is 1 to 35 parts by mass with respect to 100 parts by mass of the binder. If the content of the silica fine powder is outside the above range, the affinity between the mortar composition and water is poor, it takes time to fluidize, and the compressive strength is also low. From the viewpoint of good water affinity when water is added and kneaded and easy exhibition of high strength development property, the content of the silica fine powder is preferably 1.2 to 25 parts by mass, more preferably 1.5 to 15 parts by mass with respect to 100 parts by mass of the binder.

[0021] Examples of the fine aggregate include river sand, silica sand, crushed sand, gypsum stone, limestone sand, slag aggregate, etc. As the fine aggregate, it is preferable to use silica sand, limestone sand, etc. adjusted to a particle size that does not contain fine powder or coarse aggregate from among these. The fine aggregate may be used alone or in combination of two or more. It is preferable to use a commonly used fine aggregate with a particle size of 5 mm or less (the fraction passing through a 5 mm sieve).

[0022] The particle size of the fine aggregate is not particularly limited and can be adjusted within the range of the required particle size of the fine aggregate. The particle size of the fine aggregate can be considered from the coarse grain ratio defined by JIS A 1102:2014 "Sieving Test Method for Aggregates". From the viewpoint that better fluidity is easily obtained and bleeding is easily suppressed when made into mortar, the coarse grain ratio of the fine aggregate is preferably 1 to 4, more preferably 1.5 to 3.8, and still more preferably 2 to 3.8.

[0023] The content of the fine aggregate is preferably 50 to 300 parts by mass, more preferably 60 to 200 parts by mass, and still more preferably 70 to 150 parts by mass with respect to 100 parts by mass of the binder. If the content of the fine aggregate is within the above range, the fluidity will be further improved.

[0024] The high-strength mortar composition of this embodiment may contain a water reducing agent. The water reducing agent includes a high-performance water reducing agent, a high-performance AE water reducing agent, an AE water reducing agent, and a fluidizing agent. Examples of such water reducing agents include water reducing agents defined in JIS A 6204:2011 "Chemical Admixtures for Concrete". Examples of the water reducing agent include, for example, polycarboxylic acid-based water reducing agents, naphthalene sulfonic acid-based water reducing agents, lignin sulfonic acid-based water reducing agents, and melamine-based water reducing agents. Among these, polycarboxylic acid-based water reducing agents and naphthalene sulfonic acid-based water reducing agents are preferred. The water reducing agent may be used alone or in combination of two or more.

[0025] The content of the water reducing agent is preferably 0.05 to 2 parts by mass in terms of solid content, more preferably 0.08 to 1 part by mass, and still more preferably 0.1 to 0.5 part by mass with respect to 100 parts by mass of the binder. If the content of the water reducing agent is within the above range, it is likely to be excellent in material separation resistance and fluidity.

[0026] In the high-strength mortar composition of this embodiment, various admixtures (materials) may be blended as long as the effects of the present invention are not impaired. Examples of the admixtures (materials) include expansion materials, foaming agents, defoaming agents, gypsum, mirabilite, cement polymers, waterproof agents, rust preventives, shrinkage reducing agents, water retention agents, pigments, water repellents, efflorescence preventives, fibers, fine powders of blast furnace slag, stone powder, clay mineral powder, slag powder, fly ash, inorganic fillers, pozzolan, and the like.

[0027] The method for producing the high-strength mortar composition of this embodiment is not particularly limited. For example, it can be produced by mixing with a gravity mixer such as a V-type mixer or a tilting concrete mixer, a Henschel mixer, an injection mixer, a ribbon mixer, a paddle mixer, or the like.

[0028] The high-strength mortar composition of this embodiment can be prepared as a high-strength mortar by mixing with water, and the water content can be appropriately adjusted according to the application. The water content is preferably 20 to 40 parts by mass, more preferably 22 to 38 parts by mass, and still more preferably 25 to 35 parts by mass with respect to 100 parts by mass of the binder. If the water content is within the above range, it is easier to ensure fluidity and suppress the occurrence of material separation and the decrease in strength development.

[0029] For the preparation of the high-strength mortar of this embodiment, the same kneading equipment as that for ordinary mortar compositions can be used, and it is not particularly limited. Examples of the kneading equipment include mortar mixers, hand mixers, tilting drum mixers, twin-shaft mixers, and the like.

[0030] The high-strength mortar of this embodiment, when cured, in accordance with the Japan Society of Civil Engineers Standard JSCE-G 505-2018 "Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens (Draft)", the compressive strength at 7 days of age measured in an environment of 20 °C is 80 N / mm 2 or more, preferably 90 N / mm 2 or more, more preferably 95 N / mm 2 or more.

[0031] The high-strength mortar of this embodiment, when hardened, in accordance with the Japan Society of Civil Engineers Standard JSCE-G 505-2018 "Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens (Draft)", the compressive strength at 28 days of age measured in a 20°C environment is 100 N / mm 2 or more, preferably 110 N / mm 2 or more, more preferably 120 N / mm 2 or more is even more preferable.

[0032] It is preferable that either the compressive strength at 7 days of age or the compressive strength at 28 days of age during the hardening of the high-strength mortar is within the above range, and it is more preferable that both are satisfied. If the compressive strength during the hardening of the high-strength mortar is within the above range, it exhibits high strength development from an early stage to a long term, so that the durability of civil engineering and building structures and the like becomes even more excellent.

[0033] The high-strength mortar composition and high-strength mortar of this embodiment have good water affinity, excellent fluidity, and high compressive strength even with a small water-binder ratio. Therefore, the high-strength mortar composition and high-strength mortar of this embodiment can be suitably used for the construction or repair of civil engineering and building structures.

Examples

[0034] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. All examples were carried out in a 20°C environment.

[0035] [Materials] Cement: Ordinary Portland cement Siliceous fine powders A to G: Commercially available products. Each property is shown in Table 1. Fine aggregate: Silica sand, coarse grain ratio 2.76 Water reducing agent: Polycarboxylic acid-based water reducing agent

[0036]

Table 1

[0037] Silica fine powders A to G were prepared using commercially available silica fine powders. The SiO2 content of the silica fine powders was measured by a fluorescent X-ray analyzer, the BET specific surface area was measured by the nitrogen adsorption method, the loss on ignition was measured by heating in an electric furnace adjusted to 1000 °C for 15 minutes and measuring the weight change before and after heating, and the pH was measured by mixing each silica fine powder shown in Table 1 with water using a hand mixer to prepare a slurry with a silica fine powder concentration of 50% by mass and measuring the pH of the slurry with a pH meter.

[0038] [Mix design of high-strength mortar composition] Cement, silica fine powder, fine aggregate, water reducer and foaming agent were mix-designed at the ratios shown in Tables 2 and 3.

[0039] [Preparation of high-strength mortar] The high-strength mortar composition designed for mixing and water were added to a 10 L cylindrical container and kneaded with a hand mixer for 90 seconds to prepare high-strength mortar. Water was added at the ratios shown in Tables 2 and 3.

[0040] [Evaluation method] Various high-strength mortars were evaluated by the following evaluation methods. The results are shown in Tables 2 and 3. Each test was conducted at 20 °C. ·Flowability test: The flowability test was carried out in accordance with the flow test of JIS R 5201:2015 "Physical test methods for cement". The flow value was measured as the withdrawal flow value (0 blows). ·Fluidization time (water compatibility): After adding the high-strength mortar composition while stirring with a hand mixer to a predetermined amount of water, the time (seconds) until the high-strength mortar composition and water were integrated (the high-strength mortar was fluidized) was visually measured. If the fluidization time was within 30 seconds, the water compatibility was good. ·Compressive strength: In accordance with the Japan Society of Civil Engineers Standard JSCE - G 505 - 2018 "Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens (Draft)", the compressive strength of the high - strength mortar hardened body at 28 days of age was measured. The dimensions of the specimens were a diameter of 50 mm and a height of 100 mm. Curing was carried out as wet curing in the mold until 24 hours of age. After 24 hours, the mold was removed, and thereafter, curing was carried out in water until the specified age.

[0041]

Table 2

[0042]

Table 3

[0043] The high - strength mortar in the examples had good water affinity (fluidization time), and since the table flow value without vibration was 250 mm or more and the fluidity was also good, it had excellent workability. It showed a compressive strength of 80 N / mm 2 or more at 7 days of age and 100 N / mm 2 or more at 28 days of age. On the other hand, the high - strength mortar in the comparative examples was not excellent in terms of water affinity, fluidity, and compressive strength.

Claims

1. A mortar composition comprising a binder composed of cement and silica fine powder and fine aggregate, wherein the silica fine powder has a SiO ２ content of 96% by mass or more, a BET specific surface area of 5 to 16 m ２ / g, and a loss on ignition of 1.0% by mass or less, and the content of the silica fine powder is 1 to 35 parts by mass with respect to 100 parts by mass of the binder, a high-strength mortar composition.

2. The high-strength mortar composition according to claim 1, further comprising a water reducing agent.

3. A high-strength mortar comprising the high-strength mortar composition according to claim 1 or 2 and water, wherein the content of the water is 20 to 40 parts by mass with respect to 100 parts by mass of the binder.

4. When hardened, according to the Japan Society of Civil Engineers Standard JSCE-G 505-2018 "Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens (Draft)", the compressive strength at 28 days of age measured in a 20°C environment is 100 N / mm ２ or more, the high-strength mortar according to claim 3.

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