JP2901709B2 - Hardened cement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hardened cement body having excellent durability.

[Problems to be solved by conventional technology and invention]

In the production of conventional cement hardened materials, only emphasis is placed on compressive strength in their manufacture, and it does not take into account durability such as neutralization, water permeability, and penetration of chloride ions, leading to early deterioration of concrete structures. ing.

High-strength concrete used for piles and poles has been known as a highly durable concrete hardened body, but centrifugal molding and high-temperature and high-pressure curing (autoclave) have been used to manufacture these concrete structures. Thus, it was difficult to produce these cured products.

[Means for solving the problem]

The present inventors have results of various studies to improve the durability of the hardened cement body, superplasticizer or high performance AE water reducing agent of cement weight of the cement composition of the 320~800kg / m ³ using A cement hardened body produced by reducing the unit water volume to 80 to 160 kg / m ³ or less, and the pore volume in the hardened body is
The present inventors have found that a cured cement having a weight of 40 mm ³ / g is excellent in various durability, and have completed the present invention.

That is, the present invention provides unit water using superplasticizer or high performance AE water reducing agent is water-reducing the 80~160kg / m ^3, was cured compositions weight cement is in the range of 320~800kg / m ³ A hardened cement body obtained by the above method, wherein the hardened body has a pore volume of 5 to 40 mm ³ / g and has excellent durability.

 Hereinafter, the present invention will be described in more detail.

The hardened cement of the present invention is a material showing hardened cement paste, mortar and concrete, and has a basic composition of cement and water, and contains fine aggregate, coarse aggregate and admixture (agent) as necessary.

The durability of the hardened cement is determined by the pore volume and the amount of cement in the hardened body, and in order to obtain the desired hardened cement having the desired durability of the present invention, the cement amount is 320 to 800.
In kg / m ^3, superplasticizer or using high AE water-reducing agent and the unit water content of the cement composition and 80~160kg / m ^3, the pores of the hardened cement paste during obtained by and cured Capacity 5-40
It must be mm ³ / g. The unit water here means the water content per kneaded product 1 m ³ during the concrete kneading.
In addition, the amount of cement is involved in the improvement of external durability such as surface aesthetics of a cured cement body in addition to structural durability, for example, neutralization and water permeability.
Range 320~800kg / m ³ is necessary, preferably from 400 to 70
It is a 0kg / m ^3. In the amount of cement 320 kg / m ³ or less, weak strength of the cured surface prone to surface release when subjected to freeze-thaw effects, whereas in the 800 kg / m ³ or more caused by the hydration reaction of cement and water heating For this reason, thermal stress is generated inside the cured body, which causes cracks.

Further, in the present invention, the pore volume in the hardened cement needs to be in the range of 5 to 40 mm ³ / g, preferably 35 mm ³
/ g or less.

Thus, the pore volume in the hardened cement body is 5 to 40 mm ³ /
To g is dispersed into primary particles as possible cement particles, the unit water and high water-reducing and 80~160kg / m ^3, it is necessary to further increase the adhesion between the filling rate and the aggregate, this Therefore, it is necessary to add a high-performance water reducing agent or a high-performance AE water reducing agent during production. If the unit water amount exceeds 160 kg / m ³ , the amount of water used for the hydration reaction of the cement is too large, and a portion of excess water after drying remains as a defect, and sufficient durability cannot be obtained. On the other hand, uniform kneading becomes difficult is less than 80 kg / m ^3,
It is virtually impossible.

The curing temperature for hardening the cement is preferably maintained in the range of 3 to 20C. More preferably, it is 5 to 15 ° C. If the curing temperature is too high, the hydration reaction of the cement is accelerated, the crystal form of the initial hydrate is coarsened, and a dense crystal state cannot be obtained. On the other hand, when the curing temperature is lower than 3 ° C., there is a risk that the concrete freezes, and if frozen before hardening, the crystal structure is destroyed and a dense crystal state cannot be obtained. When the outside temperature exceeds 15 ° C, the concrete temperature often exceeds 20 ° C due to the heat of hydration, and the higher the water reduction rate, the lower the heat radiation effect and the higher the temperature rise. In this case, it is necessary to sufficiently cool the material such as the kneading water at the beginning, or to cool it by water spraying or the like.

As the high-performance water reducing agent or high-performance AE water reducing agent used in the present invention, naphthalenesulfonic acid formalin polycondensate salt,
Melamine sulfonate formalin polycondensate, polycarboxylates and their esters / ethers, purified lignin sulfonate, polystyrene sulfonate, dispersant having a phenol skeleton as a main component (for example, phenol sulfonate formalin condensate salt) , Formalin condensate salts with other monomers that can be co-condensed with phenol sulfonic acid, polystyrene phenol, co-condensation / polymer salts with other monomers that can be co-condensed with phenol), aniline sulfonic acid Dispersants as main components (for example, formalin condensate salts of aniline sulfonic acid and phenol, formalin condensate salts of aniline sulfonic acid with other monomers that can be co-condensed), and the like.

The addition ratio of the high-performance water reducing agent or the high-performance AE water reducing agent to the cement is preferably 0.3 to 3.0% by weight, more preferably 0.4 to 2.0% by weight, as an effective component. In addition, the method of adding the high-performance water reducing agent or the high-performance AE water reducing agent to the cement composition may be any of suspension, powder, and granules, and may be added at the time of dry blending with cement or kneading water. It may be added to the dissolved and once kneaded cement composition.

As the cement, ordinary portland cement, early-strength portland cement, mixed cement such as blast furnace cement and fly ash cement, alumina cement, and rapidly hardening cement can be used. However, in the case of mixed cement, the cement content excluding the mixture such as slag is used as the cement amount.

In the production of the hardened cement according to the present invention, the hardening method can be hardened by a method of hardening a normal hardened cement, and a method such as steam hardening or autoclave hardening may be used.

When producing the hardened cement according to the present invention, other cement admixtures (agents) such as an anhydrous gypsum-based strength enhancer, activated silica fine powder, slag, fly ash, waterproofing material, expanding material, air entraining agent, It can be used in combination with a fluidizing agent, a water reducing agent, a drying shrinkage reducing agent, and the like.

〔Example〕

Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

Using the following materials and the cement compositions prepared in Table 1, various physical properties of each cured cement body were measured.

 Table 2 shows the measurement results.

(Materials used) Cement (C); Normal Portland cement Specific gravity = 3.16 Fine aggregate (S); Kinokawa river sand Specific gravity = 2.57 Coarse aggregate (G); Takarazuka crushed stone Specific gravity = 2.57 Admixture; High performance water reducing agent or high Performance AE water reducing agent Water (W); Tap water (Preparation) Mixing of the cement composition was performed using a 100 l forced mixer.
A 50-liter cement composition was prepared, and a test cement hardened body was prepared in a predetermined mold. The curing temperature of each of the cement compositions is 20 ° C.

(Test method) The following physical properties were measured using the cement hardened body prepared above.

-Pore volume: measured by a mercury intrusion method. 20 ℃, 60% RH
The cured cement dried for 3 months was used.

-Freeze-thaw resistance: Measured according to JIS A 6204 Appendix 2. It is an index of durability. The values in Table 2 are after 1000 cycles and are 80
% Can be said to be a good value.

-Surface peeling resistance: The amount of weight loss due to freezing and thawing was shown. It is an index of surface peelability. The smaller the value, the better the surface peeling resistance.

Neutralization depth: Measured using chlorine ions under the conditions of 30 ° C., 60% RH, and 5% CO ₂ gas. It is preferably 15 mm or less. The values in Table 2 indicate the values after 6 months.

・ Chloride ion penetration depth: 3.5% salt water, 3cm from the surface of the cured product after 1 month
The concentration (%) of NaOH was measured. 0.05% or less is preferable.

Diffusion coefficient: Performed according to the method used at the Building Materials Testing Center. Water is immersed in the hardened cement and a pressure of 5 kgf / cm ² is applied. Since water permeates according to the pressure, it was expressed in permeation area per unit time. It is an indicator of water permeability,
100 or less is preferred. A cement hardened body dried at 20 ° C. and 60% RH for 3 months was used.

[Effects of the Invention] From the above examples, the cement hardened body of the present invention has resistance to freezing and thawing as an index of durability, surface peeling resistance (weight loss due to freezing and thawing), neutralization depth, It is clear that the chlorine ion has remarkably excellent penetration resistance and water permeability resistance.

Claims (2)

(57) [Claims] 1. The unit water volume is reduced to 80 to 160 kg / m ³ by using a high performance water reducing agent or a high performance AE water reducing agent, and the amount of cement is reduced to 32 kg / m ^3.
A hardened cement paste obtained by curing the composition in the range of 0~800kg / m ^3, the pore volume in the cured embodying 5-40
A hardened cement body with excellent durability, characterized in that it is mm ³ / g. 2. The hardened cement according to claim 1, wherein the curing temperature is 3 to 20 ° C.