JP2001226160A - Ultrahigh strength cement hardened body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement hardened body having sufficient cracking resistance and also ultrahigh strength. SOLUTION: This cement hardened body is formed form a mix containing at least cement, a pozzolanic fine powder, aggregate having <=2 mm grain size, whiskers, water and a water reducing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high-strength hardened cement body having high crack resistance, especially high resistance to cracks caused by bending stress.

[0002]

2. Description of the Related Art In general, what is called an ultra-high-strength hardened cement or an ultra-high-strength concrete has a compressive strength generally exceeding 100 MPa. Compared with concrete, the aggregate diameter is limited to a few mm or less, the water-cement ratio is kept fairly low, and the decrease in water-cement ratio is compensated for by using a water reducing agent. Often done.

[0003] Even an ultra-high-strength cement hardened body having particularly high values of compressive strength and bending strength does not necessarily have high resistance to cracks, especially resistance to the occurrence of fine cracks. This is due to the fact that the brittle material is cracked mainly due to continuous loading of a constant bending load.If such a load is repeated positively and negatively, the microcracks rapidly progress to larger cracks, and the material breaks. Connect. On the other hand, when a large amount of fibers is contained, the growth and prevention of cracks can be prevented, but the compression strength is particularly liable to decrease, and the properties of ultra-high strength are lost.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a cement hardened material having a sufficient resistance to cracks and an ultra-high strength. And

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by increasing the toughness of the hydrated component hardening phase (matrix phase) itself constituting the hardened cement, the initial cracks were formed. That the entire cured body can be provided with extremely high resistance to In order to greatly improve this toughness, it was found that the composition of whiskers made of a nonmetallic inorganic material showed an excellent effect with almost no reduction in strength, and that a specific composition containing the whiskers was obtained. The present invention has been completed because the cured product made of the product has sufficient crack resistance and strength characteristics comparable to those of the conventional ultra-high-strength cement cured product.

That is, the present invention is an ultra-high-strength cement hardened product represented by the following (1) to (8). (1) An ultra-high-strength hardened cement material comprising at least a compound containing cement, pozzolanic fine powder, aggregate having a particle size of 2 mm or less, whiskers, water, and a water reducing agent. (2) The ultra-high-strength hardened cement according to (1), wherein the blend contains one or more of metal fibers, organic fibers, and carbon fibers. (3) The metal fiber has a diameter of 0.01 to
The ultra-high-strength cement hardened product of (2), which is a steel fiber having a length of 1.0 mm and a length of 2 to 30 mm. (4) The organic fiber is
(2) which is one or more fibers selected from vinylon fiber, polypropylene fiber, polyethylene fiber, and aramid fiber having a diameter of 0.005 to 1.0 mm and a length of 2 to 30 mm.
Ultra high strength cement hardened body. (5) The carbon fiber has a diameter of 0.
The ultra-high-strength cement hardened product of (2), which has a length of 005 to 1.0 mm and a length of 2 to 30 mm. (6) The composition according to the above (1) to (3), wherein the composition contains an inorganic powder having an average particle size of 3 to 20 μm.
(5) The ultra-high-strength cement hardened body according to any of (5). (7) The ultra-high-strength cement hardened product according to any one of (1) to (6), wherein the composition contains needle-like particles and / or plate-like particles having an average particle diameter of 1 mm or less. (8) The ultrahigh-strength cement hardened product according to any one of (1) to (7), wherein the whiskers are ceramic whiskers or carbon whiskers having a diameter of 1 to 20 μm and an aspect ratio of 3 to 50.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the cement which is essentially contained in the composition is not particularly limited, and any cement may be used. Various Portsend cements such as Portland cement,
Blended cement such as blast furnace cement and fly ash cement can be used.

[0008] In the present invention, the pozzolanic fine powder essentially contained in the compound is silica fume, silica dust,
Examples include fly ash, slag, volcanic ash, silica sol, precipitated silica, and the like. Generally, in silica fume and silica dust, the average particle size is 1.0 μm or less,
This is preferable because there is no need to pulverize the powder by pulverization. A pozzolanic substance having a relatively large particle diameter is pulverized to adjust the average particle diameter to 1.0 μm or less.

[0009] By blending the pozzolanic fine powder, the cured product is densified by the microfiller effect and the cement dispersing effect, and the compressive strength is improved. On the other hand, when the amount of the pozzolanic fine powder increases, the unit water amount increases. Therefore, the amount of the pozzolanic fine powder to be added is preferably 5 to 50 parts by weight based on 100 parts by weight of the cement.

[0010] In addition, an aggregate having a particle size of 2 mm or less,
Preferably, an aggregate having a particle size of 1.5 mm or less is essential. In this case, the particle size of the aggregate is a cumulative particle size of 85% (weight), and therefore, aggregates having a particle size of more than 2 mm may be included. When the amount of aggregate having a particle size of 2 mm or less with respect to the total aggregate amount decreases, the strength decreases. Therefore, the amount of aggregate having a particle size of 2 mm or less is preferably 50% by weight or more of the total aggregate amount.

[0011] In the present invention, a mixed sand composed of one or more of river sand, land sand, sea sand, crushed sand and silica sand has a particle diameter of 2 m.
m can be used as aggregate. The amount of this aggregate is
In order to enhance the strength and durability, the amount is preferably 50 to 250 parts by weight, more preferably 80 to 180 parts by weight, based on 100 parts by weight of cement.

[0012] The composition of the present invention contains whiskers as an essential component. The whisker preferably has a higher elastic modulus than the cement hydrate, and is preferably a whisker made of a nonmetallic inorganic material from the viewpoint of affinity with the matrix. Examples of such whiskers include carbon whiskers and ceramic whiskers such as silicon carbide, silicon nitride, alumina, and zirconia.
Also, from the viewpoint of reinforcing the cement hydration structure with toughness,
Since the structure after curing is approximately several tens of μm, it is desirable to use a whisker having a size within the range of the structure, preferably a whisker having a diameter of 1 to 20 μm, more preferably a whisker having a diameter of 1 to 10 μm. Whisker. Whisker with higher aspect ratio can exert stronger toughening effect, but it is recommended to use one with aspect ratio of about 3 to 50, because if the aspect ratio is significantly increased, it will break easily during work such as blending and kneading. . The amount of the whisker is preferably 2 to 40 parts by volume, more preferably 5 to 20 parts by volume, based on 100 parts by volume of the cement, in view of the fluidity and the crack resistance after mixing. If it exceeds 40 parts by volume, the dispersibility of the whiskers and the fluidity of the composition are remarkably reduced, and if it is less than 2 parts by volume, the compounding effect is hardly exhibited, and the crack resistance is not improved.

[0013] The composition of the present invention contains a water reducing agent. As the water reducing agent, a high performance water reducing agent or a high performance AE water reducing agent having a large water reducing effect is preferable, and lignin, naphthalenesulfonic acid, melamine, polycarboxylic acid,
Any of the polyether-based components can be used. The amount of the water reducing agent to be added is preferably 0.5 to 4.0% by weight in terms of solid content with respect to cement in view of the fluidity and separation resistance of the composition, the strength after curing, and the cost.
The water reducing agent may be in a powder form or a liquid form.

In the present invention, the amount of water to be indispensable is 1 to 100 parts by weight of cement based on the fluidity and separation resistance of the water-containing composition, and the strength and property stability after curing.
The amount is preferably 0 to 35 parts by weight, more preferably 15 to 25 parts by weight. If the amount of water is less than 10 parts by weight, the fluidity is reduced and it becomes difficult to knead the composition. If the amount is more than 35 parts by weight, the curability and strength are undesirably reduced.

In the present invention, it is preferable to use a compound containing at least one of a metal fiber, an organic fiber, and a carbon fiber from the viewpoint of increasing the bending strength of the cured product, and particularly improving the toughness. Examples of the metal fiber include steel fiber and amorphous fiber. Particularly, steel fiber is recommended because it has high strength and is easily available, and the cost is relatively low. The metal fiber has a diameter of 0.01 to 1.0 mm and a length of 2
Those having a thickness of up to 30 mm are preferred. If the diameter is less than 0.01 mm, it is easily cut by tension, and the diameter is 1.0 mm
When the amount exceeds the above range, the number of fibers contained in the cured product is drastically reduced at the same blending amount, and the strength and toughness are remarkably reduced. The fiber length is 30mm
Exceeding the ratio is not preferred because fiber balls tend to be produced during kneading. When the fiber length is less than 2 mm, the adhesive strength to the matrix is reduced, and the bending strength is reduced, which is not preferable. The compounding amount of the metal fiber is preferably an amount corresponding to less than 4% of the volume of the cured product after setting, and more preferably an amount corresponding to less than 3.5%. If the compounding amount is 4% or more, the fluidity is reduced, and the workability is reduced, which is not preferable.

The organic fibers include vinylon fibers, polypropylene fibers, polyethylene fibers, and aramid fibers. The organic fibers and carbon fibers preferably have a diameter of 0.005 to 1.0 mm and a length of 2 to 30 mm. The amount of the organic fibers and / or carbon fibers is preferably less than 10%, more preferably less than 7%, of the volume of the cured product after coagulation.
If the blending amount is 10% or more, the fiber dispersibility is reduced, and the fluidity of the blend is also poor.

The compound preferably contains an inorganic powder having an average particle size of 3 to 20 μm, more preferably 4 to 10 μm, from the viewpoint of enhancing the packing density and durability of the cured product. As the inorganic powder, quartz powder is particularly recommended because it is inexpensive and can sufficiently exhibit desired effects. The quartz powder is not limited as long as it is an inorganic powder containing silica as a main component in addition to crystalline or amorphous quartz as a natural mineral source. The compounding amount of the powder is preferably 50 parts by weight or less, more preferably 20 to 35 parts by weight, based on 100 parts by weight of cement. If the amount is more than 50 parts by weight, the fluidity of the compound decreases and the strength after curing decreases, which is not preferable.

The present composition may contain needle-like and / or plate-like particles having an average major axis diameter of 1 mm or less in order to increase the toughness after curing. Examples of the acicular particles include those composed of natural or synthetic ores such as wollastonite, bauxite, and mullite, and examples of the plate-like particles include mica flake, talc flake, vermiculite flake, and alumina flake. be able to. The amount of the acicular and / or plate-like particles is preferably at most 35 parts by weight, more preferably 10 to 25 parts by weight, based on 100 parts by weight of cement. 35
Exceeding the weight part is not preferred because the fluidity of the composition may be lowered or the curability may be lowered. The shape and dimensions of the acicular particles are desirably those having an acicularity, that is, a value of (major axis diameter / minor axis diameter) of 3 or more.

The composition according to the present invention may optionally contain other components other than the above-mentioned components, for example, other admixtures.

In producing the ultra-high strength cured product of the present invention,
The order of blending each component constituting the blend is not particularly limited. One example is a method in which each component is put into a kneading machine at a time and kneaded. A method in which components other than water and water reducing agent are dry-mixed (premix) in advance, and then the premix, water and water reducing agent are charged into a kneading machine and kneaded. However, when a powdery water reducing agent is used, there is a method of premixing the water reducing agent. For kneading, any kneading machine generally used in the production of concrete can be used, and for example, an oscillating mixer, a pan mixer, a biaxial kneading mixer, a tilting mixer, or the like can be used.

The kneaded material is cured for approximately 3 to 4 weeks at room temperature and pressure to become an ultra-high strength hardened cement material.
The method of using the kneaded material is not particularly limited. For example, in the case of producing a molded product, it can be obtained by pouring into a mold having a desired shape, or may be directly constructed for various structures and civil engineering. Further, it can be used as a filler.

[0022]

Example: Low heat or ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.), silica fume having an average particle size of 0.7 μm, mixed sand consisting of silica sand No. 4 and 5 in a weight ratio of 2: 1,
Steel fiber with a diameter of 0.2 mm and a length of 15 mm, a commercially available polycarboxylic acid-based high-performance AE water reducing agent, natural quartz powder having an average particle diameter of 7 μm, and a major axis diameter of 0.3 mm and a major axis / minor axis diameter of about 4 Needle wollastonite, SiC whisker (about 4μ in diameter)
m, aspect ratio about 5) and a material selected from water,
The mixture was put into a twin-screw kneading mixer at a time so as to have the compounding amount shown in Table 1, and kneaded.

[0023]

[Table 1]

JIS A11 from each kneaded compound
A specimen for compressive strength test and a specimen for bending test were prepared according to the method according to JIS 32, respectively, and the compressive strength according to the method of JIS A1108, the bending strength according to the method of JIS A1106, and the stress generated by bending cracking. Was measured. Each measurement result is shown in Table 1.

[0025]

The hardened ultra-high strength cement of the present invention has remarkably high toughness and strength, and in particular, has extremely high resistance to bending cracks, which has been difficult with conventional concrete materials. It can be sufficiently used for applications, for example, member applications where an excessive bending stress load is applied.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C04B 16:06 C04B 16:06 G 14:38 14:38 A 14:48 14:48 C 22:06 22:06 A 16:06 16:06 A 24:26) 24:26) E 103: 30 103: 30 111: 20 111: 20

Claims (8)

[Claims] 1. A hardened ultra-high strength cement comprising at least a compound comprising cement, fine pozzolanic powder, aggregate having a particle size of 2 mm or less, whiskers, water and a water reducing agent. 2. An ultra-high-strength hardened cementitious product, characterized in that the composition contains one or more of metal fibers, organic fibers and carbon fibers. 3. The metal fiber has a diameter of 0.01 to 1.0 mm,
The ultra-high strength hardened cement according to claim 2, which is a steel fiber having a length of 2 to 30 mm. 4. The organic fiber has a diameter of 0.005 to 1.0 m.
The ultra-high-strength hardened cement body according to claim 2, which is at least one fiber selected from vinylon fibers, polypropylene fibers, polyethylene fibers, and aramid fibers having a length of 2 to 30 mm. 5. The carbon fiber has a diameter of 0.005 to 1.0 m.
3. The ultra-high-strength hardened cement body according to claim 2, wherein the length is 2 to 30 mm. 6. The ultra-high strength hardened cement according to claim 1, wherein the composition contains an inorganic powder having an average particle size of 3 to 20 μm. 7. The ultra-high-strength cement hardened product according to claim 1, wherein the composition contains needle-like particles and / or plate-like particles having an average particle size of 1 mm or less. 8. The ultra-high-strength cement hardened product according to claim 1, wherein the whisker is a ceramic whisker or a carbon whisker having a diameter of 1 to 20 μm and an aspect ratio of 3 to 50.