JP2020083698A - Rapid-hardening type light weight filling mortar composition for u-rib, and mortar thereof - Google Patents

Abstract

To provide a rapid-hardening type light weight filling mortar composition for U-rib that is rapid-hardening and that has excellent fluidity and working life, and to provide a mortar thereof.SOLUTION: Provided is a rapid-hardening type light weight filling mortar composition for U-rib, containing a binding material made of cement, calcium aluminate and gypsum, and a lightweight aggregate having a unit volume mass of 0.3 kg/L or less, and in which the binding material has a mass ratio of calcium aluminate of 5 to 14 mass% based on the total mass of the binding material, the mass ratio of gypsum is 5 to 12 mass%, and the content of the lightweight aggregate is 4 to 9.5 pts.mass per 100 pts.mass of the binding material.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a fast-curing lightweight filling mortar composition for U-ribs and a mortar thereof.

Cement-based grout materials with high fluidity are used for reinforcement and repair of civil engineering structures and building structures, installation of machines, and the like. There is a method of filling the hollow member with mortar to reinforce the hollow member such as the U rib installed on the lower surface of the existing steel deck, and the mortar should be lightweight from the viewpoint of reducing the load on the existing member. It is rare. As a solution to such a problem, a lightweight filled mortar having excellent filling properties has been proposed (for example, Patent Document 1). On the other hand, in the case of reinforcement or repair work of existing structures, there are cases where the work time is limited. For such applications, a fast-curing lightweight grout composition that rapidly develops strength after mortar filling has been proposed (for example, Patent Document 2). Moreover, mortar for filling a hollow member on the lower surface of an existing steel deck has been proposed (for example, Patent Document 3).

JP, 2014-221702, A JP, 2016-113327, A JP, 2007-197239, A

By the way, it is desirable that the mortar for filling the U-ribs should be hardened in a short time in consideration of the workable time, but at the same time, it is necessary to secure the fluidity and the pot life for performing sufficient work. It is said that. However, it is difficult to achieve these characteristics at the same time. In addition, depending on the season or environment, the temperature may rise, and in such a case, there is a problem that it becomes more difficult to secure liquidity and pot life.

Therefore, an object of the present invention is to provide a fast-curing lightweight filling mortar composition for U-ribs which is fast-curing and is excellent in fluidity and pot life, and a mortar thereof.

The present inventor has conducted extensive studies on the above problems, and by adjusting the proportions of gypsum, calcium aluminate, and lightweight aggregate, fast-setting, mortar composition having excellent fluidity and pot life and the same. It was found that a mortar can be obtained.

The present invention relates to the following [1] to [4].
[1] Includes a binder made of cement, calcium aluminate, and gypsum, and a lightweight aggregate having a unit volume mass of 0.3 kg/L or less, and the binder is calcium aluminum based on the total mass of the binder. The mass proportion of the nates is 5 to 14 mass %, the mass proportion of the gypsum is 5 to 12 mass %, and the content of the lightweight aggregate is 4 to 9.5 mass with respect to 100 mass parts of the binder. Part, quick-setting, lightweight filling mortar composition for U-ribs.
[2] The mortar composition according to [1], further including a water reducing agent and/or a thickening agent.
[3] The mortar composition according to [1] or [2], further containing an alkali metal carbonate and/or a setting retarder.
[4] For U-ribs, containing the mortar composition according to any one of [1] to [3] and water, wherein the content of water is 45 to 55 parts by mass relative to 100 parts by mass of the binder. Fast-curing lightweight filling mortar.

According to the present invention, it is possible to provide a fast-curing lightweight filling mortar composition for U-ribs, which is fast-curing and is excellent in fluidity and pot life, and a mortar thereof.

Hereinafter, one embodiment of the present invention will be described in detail. In addition, in this specification, a "U rib" refers to a rib having a U-shaped closed cross section.

The quick-hardening lightweight filling mortar composition for U-ribs of the present embodiment includes a binder made of cement, calcium aluminate and gypsum, and a lightweight aggregate having a unit volume mass of 0.3 kg/L.

The binder according to the present embodiment is composed of three components of cement, calcium aluminates and gypsum.

Various kinds of cement can be used, and examples thereof include various portland cements such as normal, early strength, ultra-early strength, low heat and moderate heat, ecocement, and fast hardening cement. Among these, ordinary portland cement is preferable from the viewpoint of ensuring sufficient pot life and achieving strength development. One type of cement may be used alone, or two or more types may be used in combination.

As calcium aluminates, when CaO is represented by C, Al ₂ O _{3 is represented} by A, Na ₂ O is represented by N, and Fe ₂ O ₃ is represented by F, C ₃ A, C ₂ A, C ₁₂ A ₇ , CA , Or calcium aluminate having a mineral composition represented by CA ₂ or the like, calcium aluminoferrite represented by C ₄ AF or the like, C ₃ A ₃ .CaF ₂ or C _{11 in} which a halogen is solid-dissolved or substituted in calcium aluminate. Calcium haloaluminate containing calcium fluoroaluminate represented as A ₇ ·CaF _2, etc., calcium sodium aluminate represented by C ₈ NA ₃ or C ₃ N ₂ A _5, etc., calcium lithium aluminate, alumina cement, Also, it is a generic term for calcium sulfaluminate represented as C ₃ A ₃ .CaSO ₄ . The calcium aluminate may be crystalline, non-crystalline, mixed amorphous or crystalline. The calcium aluminates may be used alone or in combination of two or more. Fineness of calcium aluminates, from the viewpoint of further improving the initial strength development, it is preferably 3000 cm ² / g or more in Blaine specific surface area, and more preferably 5000 cm ² / g or more. Further, the powderyness of the calcium aluminates is preferably 8000 cm ² /g or less in terms of Blaine specific surface area.

The mass ratio of the calcium aluminates is 5 to 14 mass% based on the total mass of the binder. When the content ratio of the calcium aluminates is out of the above range, it may be difficult to obtain strength development in a short time or the pot life may not be secured. From the viewpoint of further improving the pot life and strength development, the mass ratio of the calcium aluminates is preferably 6 to 14 mass% and 6.5 to 13 mass% based on the total mass of the binder. Is more preferable.

Examples of gypsum include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. As gypsum, anhydrous gypsum is preferable from the viewpoint of further improving strength development. One type of plaster may be used alone, or two or more types may be used in combination.

The mass ratio of gypsum is 5 to 12 mass% based on the total mass of the binder. When the gypsum is out of the above range, strength development is poor. From the viewpoint of further improving strength development, the gypsum content is preferably 5 to 11% by mass, and more preferably 5 to 9% by mass, based on the total mass of the binder.

The total mass ratio of calcium aluminates and gypsum is preferably 12 to 25% by mass, more preferably 12 to 22% by mass, based on the total mass of the binder, from the viewpoint of improving pot life and strength development. 12 to 17 mass% is more preferable.

The lightweight aggregate is not particularly limited, and for example, pearlite, which is an inorganic foamable aggregate obtained by crushing igneous rock such as obsidian, shirasu or pearlite, and firing and foaming, fly ash generated at a thermal power plant. Examples thereof include balloons and foam glass particles (glass balloons). As the lightweight aggregate, it is preferable to use a commonly used one having a particle size of 5 mm or less (passing through a 5 mm sieve). One kind of the lightweight aggregate may be used alone, or two or more kinds thereof may be used in combination.

The lightweight aggregate has a unit volume mass (kg/L) of 0.3 kg/L or less. When the unit volume mass of the lightweight aggregate is more than 0.3 kg/L, the unit volume mass of the mortar becomes large, and the load on the existing member increases after the filling. From the viewpoint of further reducing the load on the existing member, the unit volume mass of the lightweight aggregate is preferably 0.28 kg/L or less, and more preferably 0.25 kg/L or less. The unit volume mass of the lightweight aggregate is preferably 0.01 kg/L or more.

The content of the lightweight aggregate is 4 to 9.5 parts by mass with respect to 100 parts by mass of the binder. When the unit volume mass of the lightweight aggregate is out of the above range, the unit volume mass of the mortar becomes large, which may increase the load on the existing member after filling and may make workability difficult. From the viewpoint of further reducing the load on the existing members, the content of the lightweight aggregate is preferably 4.3 to 9 parts by mass, and 4.5 to 8 parts by mass with respect to 100 parts by mass of the binder. More preferably.

The mortar composition of this embodiment may include a water reducing agent. Water reducing agents include high performance water reducing agents, high performance AE water reducing agents, AE water reducing agents and superplasticizers. Examples of such a water reducing agent include water reducing agents specified in JIS A 6204:2011 "Chemical admixture for concrete". Examples of the water reducing agent include polycarboxylic acid water reducing agents, naphthalene sulfonic acid water reducing agents, lignin sulfonic acid water reducing agents, melamine water reducing agents, and acrylic water reducing agents. Among these, melamine water reducing agents are preferable. As the water reducing agent, one kind may be used alone, or two or more kinds may be used in combination.

The content of the water reducing agent is preferably 0.01 to 0.8 parts by mass, more preferably 0.02 to 0.5 parts by mass, and 0.03 to 100 parts by mass of the binder. It is more preferably 0.2 part by mass. When the content of the water reducing agent is within the above range, when mortar is used, material separation is unlikely to occur, better fluidity is easily obtained, and compressive strength at the time of curing is further improved.

The mortar composition of this embodiment may contain a thickener. The type of thickener is not particularly limited, and examples thereof include a cellulose thickener, an acrylic thickener, and a guar gum thickener. The thickener is preferably a cellulosic thickener. Examples of the cellulosic thickener include carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose. The thickeners may be used alone or in combination of two or more.

The content of the thickening agent is preferably 0.05 to 1 part by mass, more preferably 0.1 to 0.5 part by mass, and 0.1 to 0 part by mass with respect to 100 parts by mass of the binder. It is more preferably 0.3 part by mass. When the content of the thickening agent is within the above range, it is easy to prevent material separation and bleeding when mortar is used, and it is easy to maintain good fluidity.

The mortar composition of this embodiment may contain an alkali metal carbonate. The alkali metal carbonate is not particularly limited as long as it is a carbonate of an alkali metal (element of Group 1 of the periodic table excluding hydrogen atom). As the alkali metal carbonate, lithium carbonate, sodium carbonate and potassium carbonate are preferable from the viewpoint of further promoting strength development. The alkali metal carbonates may be used alone or in combination of two or more.

The content of the alkali metal carbonate is preferably 0.1 to 1.5 parts by mass, more preferably 0.2 to 1.0 parts by mass, and 0.1. It is more preferably 3 to 0.8 parts by mass. When the content of the alkali metal carbonate is within the above range, the strength development is further excellent.

The mortar composition of this embodiment may include a setting retarder. Examples of the setting retarder include organic acids such as citric acid, gluconic acid, malic acid, tartaric acid or salts thereof; boric acid, borates such as sodium borate, phosphates, inorganic salts such as alkali metal bicarbonates. Salt; saccharides are included. Among these, citric acid, citrate, tartaric acid, and tartrate are preferable. The setting retarder may be a powder or a liquid (for example, an aqueous solution, emulsion or suspension form). As the setting retarder, one kind may be used alone, or two or more kinds may be used in combination.

The content of the setting retarder is preferably 0.1 to 1 part by mass, more preferably 0.15 to 0.8 part by mass, and 0.2 to 0 part by mass with respect to 100 parts by mass of the binder. More preferably, it is 0.5 parts by mass. When the content of the setting retarder is within the above range, the pot life is more easily secured and the initial strength development is less likely to decrease.

The mortar composition of this embodiment may include a foaming agent. The foaming agent is not particularly limited as long as it is a substance that generates gas after kneading with water. Examples of the foaming agent include powders of amphoteric metals such as aluminum and zinc, and peroxide substances such as sodium percarbonate. As the foaming agent, sodium percarbonate is preferable from the viewpoint that it can effectively foam and can further exhibit the expansion effect. As the foaming agent, one type may be used alone, or two or more types may be used in combination.

The content of the foaming agent is preferably 0.01 to 0.2 parts by mass, more preferably 0.03 to 0.1 parts by mass, and 0.05 to 100 parts by mass of the binder. It is more preferably 0.1 part by mass. When the content of the foaming agent is within the above range, it is easy to prevent a decrease in settlement after filling the mortar, and it is difficult for the strength to decrease due to excessive expansion.

Various admixtures (materials) may be added to the mortar composition of the present embodiment within a range that does not impair the effects of the present invention. Examples of the admixture (material) include expansive material, cement polymer, defoaming agent, waterproofing agent, rust preventive agent, shrinkage reducing agent, water retention agent, pigment, water repellent, anti-whitening agent, fiber, blast furnace slag. Fine powder, stone powder, soil mineral powder, slag powder, fly ash, silica fume, inorganic filler, volcanic ash and the like can be mentioned.

The method for producing the mortar composition of the present embodiment is not particularly limited, and examples thereof include a gravity mixer such as a V-type mixer and a tilting concrete mixer, a Henschel mixer, a jet mixer, a ribbon mixer, a paddle mixer, and the like. It can be manufactured by mixing with a mixer. As a method for producing the mortar composition, a method using a ribbon mixer or a paddle mixer is preferable from the viewpoint of maintaining the shape of the lightweight aggregate and maintaining the quality. Further, the mortar composition of the present embodiment can also be manufactured by a method in which each material is weighed and put into a container such as a bag or a polyethylene container.

The mortar composition of the present embodiment can be prepared as a mortar by mixing with water, and the content of the water may be appropriately adjusted according to the application. The content of water is preferably 45 to 55 parts by mass, more preferably 46 to 54 parts by mass, and further preferably 47 to 53 parts by mass with respect to 100 parts by mass of the binder. When the water content is within the above range, it is easier to secure the fluidity, and it is easy to suppress the occurrence of material separation, the increase in shrinkage of the cured product, and the decrease in the initial strength development.

The mortar of this embodiment has a flow value of preferably 160 to 240 mm, more preferably 180 to 235 mm, and further preferably 190 to 230 mm. When the flow value of the mortar is within the above range, it is easy to fill the U-rib when filling the U-rib, and air accumulation due to the pre-flow hardly occurs.

The mortar of this embodiment preferably has a unit volume mass of 1.35 kg/L or less, more preferably 1.30 kg/L or less, and further preferably 1.28 kg/L or less. Moreover, the unit volume mass of the mortar is preferably 1.00 kg/L or more. If the unit volume mass of the mortar is within the above range, the load on the existing member can be further reduced.

The mortar of the present embodiment can be prepared by using the same kneading equipment as that for a normal mortar composition, and is not particularly limited. Examples of the kneading equipment include a mortar mixer, a grout mixer, a hand mixer, a tilting mixer, and a twin-screw mixer.

The mortar composition of the present embodiment and the mortar thereof are light in weight, have fast hardening properties, and can sufficiently secure fluidity and pot life. Therefore, such a mortar composition and its mortar can be suitably used for filling the U-ribs which are hollow members. Further, the mortar composition of the present embodiment and the mortar thereof can be used even under a relatively warm environment of 15° C. or higher and under high temperature conditions of around 30° C.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

The materials used in the examples are as follows.
Cement: Normal Portland cement Calcium aluminate: Alumina cement Gypsum: Anhydrous gypsum Light weight aggregate A: Pearlite light weight aggregate (unit volume mass 0.1 kg/L)
Lightweight Aggregate B: Pearlite Lightweight Aggregate (Unit Volume Mass 0.25kg/L)
Alkali metal carbonate: Sodium carbonate, lithium carbonate Thickener: Methylcellulose-based thickener Water-reducing agent: Melamine-based water-reducing agent Setting retarder: Citric acid Foaming agent: Sodium percarbonate

[Composition design of mortar composition]
Various materials were blended and designed in the amounts shown in Table 1 with respect to 100 parts by mass of a binder composed of cement, calcium aluminate and gypsum.

[Mortar production]
In a 20° C. or 30° C. environment, 3000 g of a mortar composition, which was designed to be mixed in a 10 L cylindrical container, and water were added and kneaded with a hand mixer for 90 seconds to prepare a mortar. 51 parts by mass of water was added to 100 parts by mass of the binder.

[Evaluation methods]
Various mortars were evaluated by the following evaluation methods. The results evaluated at 20°C are shown in Table 2, and the results evaluated at 30°C are shown in Table 3.
・Flow value JIS R 5201:2015 “Physical test method for cement” 12. According to the flow test, the flow value (0 stroke) of the mortar was measured under each temperature environment.
-Measurement of Unit Volume Mass The unit volume mass was measured according to JIS A 1171:2016 "Test method for polymer cement mortar" 6.4 Unit volume mass test.
-Working time In a 20°C or 30°C environment, the mortar after kneading was transferred to a 5 L container, and the flow test value was measured every 15 minutes immediately after kneading. However, before measurement, a sample was prepared by stirring mortar 5 times with a spoon. As an index of the pot life, the time until the flow value fell below 160 mm was measured. For example, when the flow value after 75 minutes was 160 mm or more and the flow value after 90 minutes was 160 mm or less or measurement was impossible, the working time was set to 75 minutes.
-Compressive strength According to the Japan Society of Civil Engineers standard JSCE-G505-2010 "Compressive strength test method of mortar or cement paste using a cylindrical specimen (draft)", the compressive strength of the cured mortar at each age was measured. The dimensions of the test piece were 50 mm in diameter and 100 mm in height. As for the curing, when the material was aged within 24 hours, it was wet-cured with the mold kept at each temperature until just before the age. At the material age of 28 days, the frame was deframed after 24 hours, and thereafter the material was cured in water until the material age of 28 days.

From Table 2 and Table 3, it was shown that the mortars of Examples 1 to 6 were excellent in fluidity (flow value) and compressive strength at 4 hours and 28 days. Moreover, according to the mortars of Examples 1 to 6, it is possible to secure a working time of 90 minutes or longer at 20° C., and a working time of 30 minutes or longer even under a high temperature condition of 30° C. did it.

Claims (4)

Includes a binder made of cement, calcium aluminate and gypsum, and a lightweight aggregate having a unit volume mass of 0.3 kg/L or less,
The binder has a mass ratio of the calcium aluminate of 5 to 14 mass% and a mass ratio of the gypsum of 5 to 12 mass% based on the total mass of the binder.
The content of the lightweight aggregate is 4 to 9.5 parts by mass with respect to 100 parts by mass of the binder, and a rapid-setting, lightweight filling mortar composition for U-ribs. The mortar composition according to claim 1, further comprising a water reducing agent and/or a thickening agent. The mortar composition according to claim 1 or 2, further comprising an alkali metal carbonate and/or a setting retarder. Comprising the mortar composition according to any one of claims 1 to 3 and water,
A quick-hardening lightweight filling mortar for U-ribs having a water content of 45 to 55 parts by mass with respect to 100 parts by mass of the binder.