Polymer cement mortar composition and polymer cement mortar

Abstract

To provide a polymer cement mortar composition that exhibits excellent spraying performance with a low rebound amount and low dust generation during spraying, and also excellent troweling finish performance.SOLUTION: A polymer cement mortar composition is provided, comprising cement, a pozzolanic material, a polymer for cement, and fine aggregate, where the particle size of the fine aggregate is such that the mass ratio of aggregate particles with a particle size of less than 0.6 mm is 2 to 45 mass%, the mass ratio of aggregate particles with a particle size of 0.6 mm or more and less than 1.2 mm is 35 to 90 mass%, and the mass ratio of aggregate particles with a particle size of 1.2 mm or more and less than 2.5 mm is 2 to 55 mass%, all with respect to the total mass of the fine aggregate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polymer cement mortar composition and a polymer cement mortar. [Background technology]

[0002] Cement mortar is often used to repair concrete structures, and the application methods vary depending on the purpose and scale, with the main methods known being plastering and spraying.

[0003] As a spraying method, a dry mortar spraying method has been disclosed (Patent Document 1), which is characterized by separately preparing a powder mixture consisting of cement, aggregate, expansive material, and non-aqueous shrinkage-reducing agent, and a liquid containing a polymer dispersion for cement admixture, mixing them just before the spraying nozzle, and spraying them.

[0004] The dry spraying method has the advantages of being excellent for long-distance pumping, allowing for a large amount of construction per day, and allowing mortar to be poured in locations far from the mixing plant, so it is used in special work environments such as culverts, waterways, tunnels, and roads with traffic restrictions.

[0005] A known example of a material used in the dry spraying method is a mortar material for dry spraying, which contains a powder mixture containing cement, fine aggregate, expansive agent, and a non-aqueous liquid shrinkage-reducing agent, and a polymer dispersion liquid, in which at least the cement in the powder mixture is coated with the non-aqueous liquid shrinkage-reducing agent, the powder mixture contains 1 to 10 mass% of fine aggregate with an average particle size of 1.2 to 3.6 mm and a maximum particle size of 5 mm or more, and the polymer solids / cement mass ratio is 1 to 15 mass% (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-283335 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-207643 Summary of the Invention [Problem to be solved by the invention]

[0007] In the dry spraying method, a large amount of spraying material is sprayed using high-pressure air in order to pump the material long distances or for large-scale construction work, which has led to issues such as the material being lost due to rebound (rebound) and the generation of a lot of dust, which affects the working environment.

[0008] Furthermore, in the dry spraying method, the surface to be sprayed may be finished with a trowel after spraying, so the spraying material used is required to be trowel-finishable, with the ability to finish the surface with fewer sprays and with minimal adhesion to the trowel.

[0009] Therefore, an object of the present invention is to provide a polymer cement mortar composition and a polymer cement mortar that have excellent spraying performance, such as a reduced rebound rate and less dust during spraying, and also have excellent trowel finishing performance. [Means for solving the problem]

[0010] As a result of extensive research into the above-mentioned problems, the present inventors have found that by blending fine aggregate with an adjusted particle size distribution, it is possible to obtain a polymer cement mortar composition and a polymer cement mortar that combine good spraying performance and good trowel finishing performance.

[0011] That is, the present invention is represented by the following [1] to [7]. [1] Includes cement, pozzolanic materials, cementitious polymers, and fine aggregates; A polymer cement mortar composition, wherein the particle size of the fine aggregate is such that, relative to the total mass of the fine aggregate, the mass proportion of aggregate particles having a particle size of less than 0.6 mm is 2 to 45 mass%, the mass proportion of aggregate particles having a particle size of 0.6 mm or more but less than 1.2 mm is 35 to 90 mass%, and the mass proportion of aggregate particles having a particle size of 1.2 mm or more but less than 2.5 mm is 2 to 55 mass%. [2] The polymer cement mortar composition according to [1], wherein the mass proportion of the aggregate particles having a particle size of 0.6 mm or more and less than 1.2 mm is greater than the combined mass proportion of the aggregate particles having a particle size of less than 0.6 mm and the aggregate particles having a particle size of 1.2 mm or more and less than 2.5 mm. [3] The polymer cement mortar composition according to [1] or [2], wherein the content of the fine aggregate is 100 to 300 parts by mass per 100 parts by mass of cement. [4] The polymer cement mortar composition according to [1] or [2], further comprising fibers. [5] The polymer cement mortar composition according to [1] or [2], which is for use as a dry spraying material. [6] A polymer cement mortar composition according to [1] or [2], and water, The polymer cement mortar has a water content of 10 to 25 parts by mass per 100 parts by mass of the polymer cement mortar composition. [7] When hardened, the compressive strength at 28 days is 45 N / mm, measured at 20°C in accordance with JIS A 1108:2018 "Test method for compressive strength of concrete." 2 The polymer cement mortar according to [6]. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a polymer cement mortar composition and a polymer cement mortar that have excellent spraying performance, such as a reduced rebound rate and little dust during spraying, and also have excellent trowel finishing performance. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described in detail below. In this specification, the contents of materials other than water are expressed in terms of solid content or anhydrous content, and if a material contains moisture, the moisture is included in the water content of the polymer cement mortar.

[0014] The polymer cement mortar composition of the present embodiment includes cement, a pozzolanic material, a cement polymer, and fine aggregate.

[0015] Various types of cement can be used, including various types of Portland cement such as ordinary, early-strength, ultra-early-strength, low-heat, and medium-heat; filler cements containing ground granulated cooled blast furnace slag such as limestone powder; and environmentally friendly cements (ecocements) produced primarily from various industrial waste materials. One type of cement may be used alone, or two or more types may be used in combination. Ordinary Portland cement or early-strength Portland cement is preferred, as this improves the consistency of the polymer cement mortar during spraying and further improves the early strength development.

[0016] The cement content is preferably 20 to 50 parts by mass, more preferably 25 to 45 parts by mass, and even more preferably 30 to 40 parts by mass, per 100 parts by mass of the polymer cement mortar composition. If the cement content is within the above range, the strength development is even more excellent.

[0017] Examples of pozzolanic substances include various fly ashes described in JIS A 6201:2015, silica fume, ground granulated blast furnace slag, and amorphous aluminosilicate described in JIS A 6207:2016. From the viewpoint of achieving even better long-term strength development, pozzolanic substances are used in applications with a strength of 2000 to 5000 cm 2 Fly ash and blast furnace slag powder with a Blaine specific surface area of ​​5-30 m 2 Silica fume having a BET specific surface area of ​​1 / g is preferred.

[0018] The content of the pozzolan substance is preferably 1 to 40 parts by mass, more preferably 5 to 30 parts by mass, even more preferably 7 to 20 parts by mass, and particularly preferably 8 to 18 parts by mass, relative to 100 parts by mass of cement. If the content of the pozzolan substance is within the above range, the stability and dust reduction during spraying will be even better, the finish with a trowel after spraying will tend to be good, and the strength development after hardening will be even better.

[0019] The polymer for cement is preferably a polymer defined in JIS A 6203:2015 "Polymer dispersions and re-emulsifiable powder resins for cement admixture." Examples of such polymer for cement include polymer dispersions and re-emulsifiable powder resins. Examples of polymer dispersions include synthetic rubbers such as styrene butadiene rubber (SBR), natural rubbers, rubber asphalts, ethylene vinyl acetates, acrylic esters, resin asphalts, etc. Among these, synthetic rubbers, ethylene vinyl acetates, and acrylic esters are preferred, and more specifically, synthetic rubber latex, polyacrylic esters, and ethylene vinyl acetates are more preferred. Examples of re-emulsifiable powder resins include synthetic rubbers such as styrene butadiene rubber; acrylic esters; ethylene vinyl acetates; vinyl acetate / vinyl versatate esters; and vinyl acetate / vinyl versatate / acrylic esters. Among the polymers for cement, acrylic ester-based re-emulsifiable powder resins are preferred from the viewpoint of superior water resistance. As the cement polymer, a polymer dispersion may be used, a re-emulsified powder resin may be used, or a combination of a polymer dispersion and a re-emulsified powder resin may be used. When a polymer dispersion is used, it can be added by a method such as adding a mixture with water. One type of cement polymer may be used alone, or two or more types may be used in combination.

[0020] The content of the polymer for cement is preferably 1 to 18 parts by mass, more preferably 2 to 16 parts by mass, even more preferably 4 to 14 parts by mass, and particularly preferably 5.5 to 12 parts by mass, based on 100 parts by mass of cement in terms of solid content. If the content of the polymer for cement is within the above range, the adhesiveness and thick sprayability will be even better.

[0021] The fine aggregate is not particularly limited, and examples thereof include river sand, silica sand, crushed sand, kansui stone, limestone sand, slag aggregate, etc. Among these, silica sand is preferably used as the fine aggregate from the viewpoint of being more excellent in strength development during spraying. One type of fine aggregate may be used alone, or two or more types may be used in combination.

[0022] The particle size of the fine aggregate is such that, relative to the total mass of the fine aggregate, the mass percentage of aggregate particles with a particle size of less than 0.6 mm is 2 to 45 mass%, the mass percentage of aggregate particles with a particle size of 0.6 mm or more but less than 1.2 mm is 35 to 90 mass%, and the mass percentage of aggregate particles with a particle size of 1.2 mm or more but less than 2.5 mm is 2 to 55 mass%. If the particle size of the fine aggregate is outside the above ranges, it becomes difficult to achieve both the properties required during spraying, such as reduced rebound rate and reduced dust, and the required trowel finishability after spraying. Furthermore, if the particle size of the fine aggregate is within the above ranges, excellent spraying stability and thick spraying during spraying and good surface finishability after spraying are achieved.

[0023] The mass proportion of aggregate particles having a particle size of less than 0.6 mm is preferably 5 to 40 mass %, more preferably 8 to 30 mass %, and even more preferably 10 to 20 mass %, based on the total mass of the fine aggregate. The mass proportion of aggregate particles having a particle size of 0.6 mm or more and less than 1.2 mm is preferably 40 to 80 mass%, more preferably 45 to 70 mass%, and even more preferably 50 to 65 mass%, relative to the total mass of the fine aggregate. The mass proportion of aggregate particles having a particle size of 0.6 mm or more and less than 1.2 mm is preferably greater than the mass proportions of aggregate particles having a particle size of less than 0.6 mm and aggregate particles having a particle size of 1.2 mm or more and less than 2.5 mm, respectively, and more preferably greater than the combined mass proportion of aggregate particles having a particle size of less than 0.6 mm and aggregate particles having a particle size of 1.2 mm or more and less than 2.5 mm. The mass proportion of aggregate particles having a particle size of 1.2 mm or more and less than 2.5 mm is preferably 10 to 45 mass%, more preferably 15 to 35 mass%, and even more preferably 20 to 30 mass%, relative to the total mass of the fine aggregate. The mass proportion of aggregate particles having a particle size of 1.2 mm or more and less than 2.5 mm is preferably greater than the mass proportion of aggregate particles having a particle size less than 0.6 mm. From the viewpoint of further reducing the rebound rate, the content of aggregate particles having a particle size of 2.5 mm or more is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, of the total mass of the fine aggregate. The fine aggregate does not have to contain aggregate particles having a particle size of 2.5 mm or more. If the particle size of the fine aggregate is within the above range, it is easy to achieve both the above-mentioned properties required during spraying and the above-mentioned properties required after spraying, and the spraying stability and thickness can be improved during spraying, resulting in better surface finishability after spraying.

[0024] In this specification, "particle size" refers to a particle size measured by a sieving test according to the method described in JIS A 1102:2014, "Sieving Test Method for Aggregates." That is, aggregate particles with a particle size of less than 0.6 mm refer to particles that pass through a sieve with 0.6 mm openings, aggregate particles with a particle size of 0.6 mm or more but less than 1.2 mm refer to particles that pass through a sieve with 1.2 mm openings and remain on a 0.6 mm sieve, aggregate particles with a particle size of 1.2 mm or more but less than 2.5 mm refer to particles that pass through a sieve with 2.5 mm openings and remain on a 1.2 mm sieve, and aggregate particles with a particle size of 2.5 mm or more refer to particles that remain on a 2.5 mm sieve.

[0025] The content of fine aggregate is preferably 100 to 300 parts by mass, more preferably 110 to 250 parts by mass, even more preferably 120 to 220 parts by mass, particularly preferably 130 to 195 parts by mass, and most preferably 145 to 185 parts by mass, relative to 100 parts by mass of cement. If the content of fine aggregate is within the above range, the rebound rate can be further reduced, and the trowel finish after spraying will also be further improved.

[0026] The polymer cement mortar composition of the present invention preferably further contains fibers from the viewpoint of improving thickness sprayability. Examples of fibers include organic fibers such as vinylon fibers, polypropylene fibers, and nylon fibers; steel fibers; and inorganic fibers such as glass fibers. From the viewpoint of better dispersibility, the fibers are preferably organic fibers, and vinylon fibers and polypropylene fibers are more preferred. One type of fiber may be used alone, or two or more types may be used in combination.

[0027] The length of the fibers is preferably 2 to 15 mm, more preferably 3 to 14 mm, and most preferably 4 to 13 mm. If the length of the fibers is within the above range, sufficient thick blowing properties can be easily obtained while ensuring flowability.

[0028] The content of the fibers is preferably 0.01 to 2 parts by mass, more preferably 0.1 to 1 part by mass, even more preferably 0.3 to 0.8 parts by mass, and particularly preferably 0.35 to 0.6 parts by mass, relative to 100 parts by mass of cement. If the content of the fibers is within the above range, sufficient thickness blowing property and strength development are likely to be obtained while ensuring fluidity.

[0029] In addition to the materials described above, the polymer cement mortar composition of the present invention can contain various admixtures (chemical additives) used in mortar and concrete, provided that the effects of the present invention are not impaired. Examples of such admixtures include sodium sulfate, gypsum, stone powder, inorganic fillers, water-reducing agents, thickeners, antifoaming agents, foaming agents, shrinkage-reducing agents, accelerators, and expansion agents. One type of admixture may be used alone, or two or more types may be used in combination. When a water-reducing agent is added, from the viewpoint of reducing the unit water content and ensuring early hardening, the amount is preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, even more preferably 0.1 parts by mass or less, and even more preferably 0.01 parts by mass or less, per 100 parts by mass of cement. The polymer-cement mortar composition of the present invention may be substantially free of a water-reducing agent.

[0030] The method for premixing the polymer cement mortar composition of the present invention is not particularly limited. For example, the premixing can be carried out using a ribbon mixer, paddle mixer, or the like, which has a relatively small shearing action and mainly uses a dispersing or diffusing action due to scraping with paddles or blades.

[0031] The polymer cement mortar composition of the present invention has excellent sprayability, including a low rebound rate, stability during spraying, and minimal dust during spraying, and also has excellent trowel finishing properties, making it suitable for use as a dry spraying material for dry spraying. A dry spraying system, for example, includes a sprayer that pneumatically delivers the polymer cement mortar composition via an air compressor and a liquid pump that delivers water under pressure. The water delivered by the liquid pump is mixed by pressure into a shower ring installed midway along the pneumatic delivery hose for the polymer cement mortar composition (approximately 1 to 2 m before the spray nozzle), and the polymer cement mortar is discharged from the spray nozzle and applied to the target surface, such as a wall, ceiling, slope, or repair area. The amount of water injected and mixed by the shower ring is preferably 10 to 25 parts by mass, more preferably 12 to 20 parts by mass, and even more preferably 13 to 18 parts by mass, per 100 parts by mass of the polymer cement mortar composition.

[0032] The polymer cement mortar composition of the present invention can be prepared as a polymer cement mortar by mixing with water, and the water content can be adjusted appropriately depending on the application. The water content is preferably 10 to 25 parts by mass, more preferably 12 to 20 parts by mass, and even more preferably 13 to 18 parts by mass, per 100 parts by mass of the polymer cement mortar composition. If the water content is within the above range, the rebound amount is easily suppressed and sufficient compressive strength is easily obtained.

[0033] The polymer cement mortar of the present invention, when hardened, has a compressive strength of 45 N / mm2 at 28 days, measured at 20°C in accordance with JIS A 1108:2018 "Test method for compressive strength of concrete." 2 It is preferable that the resistance is 50N / mm or more. 2 More preferably, it is 55N / mm 2 More preferably, it is 60 N / mm 2 It is particularly preferable that the compressive strength at 28 days is 80N / mm 2If the compressive strength at 28 days is within the above range, the long-term strength development can be further enhanced.

[0034] The polymer cement mortar of the present invention has excellent sprayability, including a low rebound rate, stability during spraying, and little dust during spraying, and also has excellent trowel finishing properties. Therefore, the polymer cement mortar of the present invention can be used not only for the dry spraying described above, but also as a wet spraying material for wet spraying methods, and can also be used as a repair and reinforcing material for concrete structures, steel-concrete composite structures, etc. The method of using the polymer cement mortar of the present invention can be selected as appropriate, for example, by filling recesses with a trowel, by leveling the surface with a vibrator or the like after filling and then finishing with a trowel, or by wet spraying onto the area to be repaired. [Example]

[0035] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. All examples were carried out in an environment of 20°C.

[0036] [material] Cement (abbreviation C): High-early-strength Portland cement Fine aggregate (abbreviation S): Silica sand (adjusted to the particle size shown in Table 1) Pozzolanic material 1 (abbreviated as P1): Ground granulated blast furnace slag (blaine specific surface area 4000 cm 2 / g) Pozzolanic material 2 (abbreviated as P2): Fly ash (blaine specific surface area 2500 cm 2 / g) Pozzolanic material 3 (abbreviated as P3): Silica fume (BET specific surface area 10.2 m) 2 / g) Fibers (abbreviation F): Vinylon fiber (fiber length 5 mm) Cement polymer (abbreviated as CP): Re-emulsifiable powder resin (acrylic ester copolymer)

[0037] [Preparation of polymer cement mortar composition] Various materials were blended according to the formulation shown in Table 1, charged into a ribbon mixer, and mixed to obtain a polymer cement mortar composition.

[0038] [Table 1]

[0039] [Dry spraying] Dry spraying was carried out using the following system: The polymer cement mortar composition was pneumatically pumped through a pressure-resistant hose using an Arriva 237 dry mortar sprayer via an air compressor. Water was pumped using a single-axis eccentric screw pump, and 14 to 16 parts by mass of water was injected and mixed with 100 parts by mass of the polymer cement mortar composition through a shower ring installed midway along the pneumatic hose for the polymer cement mortar composition (1.5 m before the spray nozzle) to produce the spray material (polymer cement mortar). This was sprayed onto the experimental side wall and core box from the nozzle tip of the spray nozzle. A pressure-resistant hose with an inner diameter of 1.5 inches and a length of 45 m was used to pump the spray material.

[0040] [Evaluation test] The polymer cement mortar compositions of Examples 1 to 15 and Comparative Examples 1 to 4 shown in Table 1 were each dry sprayed and subjected to various evaluation tests. The evaluation test methods are described below. The results are shown in Table 2.

[0041] Rebound rate In accordance with JSCE-F563-2005, a core box (formwork) was placed vertically on the ground, and the spraying material (polymer cement mortar) was dry-sprayed vertically onto the core box for one minute, and the amount of rebound (polymer cement mortar that fell without being sprayed onto the formwork) was measured. The rebound rate was calculated using the following formula from the theoretically produced mass (theoretical amount) of polymer cement mortar and the amount of rebound. Rebound rate (mass%) = (rebound amount / theoretical amount) x 100

[0042] Spray stability Dry spraying was carried out on the experimental side wall for 10 minutes, and the spraying material (polymer cement mortar) was checked using a pressure gauge and visually to ensure that it was being pumped stably. Those that were stable with little pulsation at the nozzle tip were given a ◎, those that were stable with some pulsation at the nozzle tip were given a ○, those that were stable with a lot of pulsation at the nozzle tip were given a △, and those that lacked stability due to material separation or pulsation from the spraying machine were given an ×.

[0043] Dust level The spraying material (polymer cement mortar) was dry sprayed onto the experimental sidewall in a U-shaped spraying yard, and the level of dust was confirmed visually. As an index of the level of dust, ◎ indicates that almost no dust was visible, ○ indicates that there was a little dust floating around, △ indicates that there was some dust floating around but the spraying worker and the spraying situation could be seen, and × indicates that the spraying worker was difficult to see and there was a lot of dust.

[0044] ·Thickness The spraying material (polymer cement mortar) was dry sprayed onto the experimental sidewall in one go, and the spraying thickness was measured. The thickness was evaluated as follows: 20cm or more: ◎; 15cm or more but less than 20cm: ○; 10cm or more but less than 15cm: △; and less than 10cm: ×.

[0045] -Easy to finish with trowel The spraying material (polymer cement mortar) was dry sprayed onto a formwork (30 cm x 30 cm x 2 cm), and the finishability was evaluated by trowel leveling. A finish that was completed after a few trowel levelings and had little mortar adhering to the trowel was rated as ◎, a finish that was completed after more trowel levelings than ◎ and had some mortar adhering to the trowel was rated as ○, a finish that was completed after more trowel levelings than ○ and had some mortar adhering to the trowel was rated as △, and a finish that was not completed even after trowel leveling and had a lot of mortar adhering to the trowel was rated as ×.

[0046] Compression strength The sprayed material (polymer cement mortar) sprayed onto the core box was cured in air at 20°C until it was 7 days old, and then a φ10cm x 20cm specimen was cut out using a core drill. The cored specimens were then cured in air in a test room at 20°C and 60% RH until it was 28 days old. On the 28th day, the compressive strength of the specimens was measured in accordance with JIS A 1108:2018.

[0047] [Table 2]

[0048] The polymer cement mortar compositions of the Examples had a low rebound rate when dry sprayed, could be stably pumped during spraying, generated little dust, and were good at thick spraying. Furthermore, the polymer cement mortar compositions of the Examples also allowed for good trowel finishing after spraying, and the compressive strength of the hardened product was excellent. On the other hand, the polymer cement mortar compositions of the Comparative Examples had problems with either a high rebound rate when dry sprayed, a large amount of dust generation, or insufficient trowel finishing after spraying.

Claims

1. including cement, pozzolanic materials, cementitious polymers, and fine aggregates; The particle size of the fine aggregate is such that, relative to the total mass of the fine aggregate, the mass ratio of aggregate particles having a particle size of less than 0.6 mm is 2 to 45 mass%, the mass ratio of aggregate particles having a particle size of 0.6 mm or more and less than 1.2 mm is 35 to 90 mass%, and the mass ratio of aggregate particles having a particle size of 1.2 mm or more and less than 2.5 mm is 2 to 55 mass%, A polymer cement mortar composition, wherein when a water reducing agent is added, the amount of the water reducing agent added is 0.1 parts by mass or less per 100 parts by mass of the cement.

2. 2. The polymer cement mortar composition according to claim 1, wherein the mass fraction of the aggregate particles having a particle size of 0.6 mm or more and less than 1.2 mm is greater than the combined mass fraction of the aggregate particles having a particle size of less than 0.6 mm and the aggregate particles having a particle size of 1.2 mm or more and less than 2.5 mm.

3. 3. The polymer cement mortar composition according to claim 1, wherein the content of the polymer for cement is 1 to 18 parts by mass in terms of solid content per 100 parts by mass of the cement.

4. 3. The polymer cement mortar composition according to claim 1, further comprising 0.01 to 2 parts by mass of fibers per 100 parts by mass of the cement.

5. The polymer cement mortar composition according to claim 1 or 2, which is for use as a dry spraying material.

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