JP3936776B2 - Admixture and concrete composition - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel admixture capable of reducing the amount of cement such as concrete and mortar and imparting high strength to the obtained concrete and the like and a concrete composition containing the admixture.
[0002]
[Prior art]
Conventionally, blast furnace granulated slag, fly ash, expansion material, natural pozzolana, silica fume, and the like are known as admixtures. Among them, fly ash is mainly obtained as a by-product of thermal power plants that use coal as fuel, and is often used for the purpose of reducing unit water volume and improving workability by mixing with concrete. According to JIS standards, this fly ash is specified to have a specific gravity of 1.95 or more, a specific surface area of 2500 cm ² / g or more, a 45 μm sieve residue of 40% or less, and a SiO _{2 of} 45% or more.
[0003]
By the way, not all by-products of thermal power plants that use coal as fuel can be used as fly ash, and especially by-products from pressurized fluidized bed power plants have a lower SiO ₂ content compared to fly ash, CaO and for the content of SO ₃ is high, hardly satisfy the standard of the fly ash. This is presumably because the combustion temperature in the boiler is lower than that in the prior art and limestone powder is used for desulfurization. Naturally, it is not considered that such a by-product that does not satisfy the standard of fly ash can be used as an admixture, and the effective utilization method has not been established.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a novel admixture that can reduce the amount of cement by being contained in concrete, mortar, and the like, and that imparts high strength to concrete or the like.
Another object of the present invention is to provide a novel admixture using coal ash that cannot be used as fly ash in a by-product from a pressurized fluidized bed in a conventional thermal power plant or the like.
Another object of the present invention is to provide an inexpensive concrete composition containing the novel admixture and excellent in strength.
[0005]
[Means for Solving the Problems]
According to the present invention, SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO and SO ₃ , SiO ₂ content is 30 to 40% by weight, Al ₂ O ₃ content is 15 to 35% by weight, Fe ₂ O ₃ content is 1 to 10% by weight, CaO content is 10 to 30% by weight, SO ₃ content is 3.0 to 10% by weight, and the specific surface area is 10000 cm ² / g. An admixture comprising the above coal ash is provided. As the coal ash, coal ash collected from a dust collection facility after the coal is subjected to a combustion reaction in a pressurized fluidized bed together with limestone powder for desulfurization can be used. Moreover, according to this invention, the concrete composition containing a cement, an aggregate, water, and the said admixture is provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The admixture of the present invention contains SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO and SO ₃ , SiO ₂ content is 30 to 40 wt%, CaO content is 10 to 30 wt% SO ₃ It has a chemical composition with a proportion of 3.0 to 10% by weight and a specific surface area of 10,000.
Specific coal ash (hereinafter referred to as “coal ash A”) of cm ² / g or more is used as an active ingredient.
[0007]
The content ratio of components other than SiO ₂ , CaO and SO ₃ is not particularly limited, and a content ratio comparable to that of a normal fly ash composition is sufficient. For example, the Al ₂ O ₃ content is preferably 15 to 35% by weight, and the Fe ₂ O ₃ content is preferably 1 to 10% by weight. In the coal ash A, the total content of SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO and SO ₃ is usually about 90 to 98% by weight, and the balance is not particularly limited. The particle size of the coal ash A is not particularly limited, but a particle size that passes through all 45 μm sieves is preferable.
[0008]
The coal ash A can be obtained by collecting coal from a dust collection facility after the coal is subjected to a combustion reaction in a pressurized fluidized bed. Preferably, it is desirable to obtain coal from a dust collection facility after combustion reaction in a pressurized fluidized bed with limestone powder for desulfurization, particularly in a pressurized fluidized bed combined power plant. What is obtained by making it extract | collect from a 2nd dust collection equipment (secondary cyclone) after making it burn-react in a fluidized bed is preferable. By reusing the by-product from the pressurized fluidized bed in this way, the cost of the admixture of the present invention can be reduced and environmentally preferable.
[0009]
In general, the admixture of the present invention can improve the concrete strength by about 10 to 30% by using 15 to 30% by weight of the cement component of the concrete.
[0010]
The concrete composition of the present invention contains cement, aggregate, water and the admixture A.
As the cement, various Portland cements and special cements such as ordinary Portland cement, early-strength Portland cement, and moderately hot Portland cement can be used.
As the aggregate, it is possible to use aggregates and fine aggregates used for normal concrete such as natural aggregates and artificial aggregates.
The water may be any of tap water, ground water, river water, recovered water, and seawater as long as it does not contain a substance that adversely affects the reaction of cement.
[0011]
In the concrete composition of the present invention, the ratio of water / (cement + admixture A) is preferably 55 to 30% by weight, particularly preferably 40 to 30% by weight. Further, the content ratio of the admixture A with respect to the total amount of the cement and the admixture A is preferably 15 to 30% by weight. The content ratio of the aggregate may be about the same as the content ratio of ordinary concrete.
[0012]
In addition to the essential components, the concrete composition of the present invention may contain various additives that are usually added to concrete. Specifically, an admixture other than the admixture A, an AE agent, a water reducing agent, a high performance water reducing agent, a high performance AE water reducing agent, and the like can be contained. In particular, the required slump and air amount can be ensured by adjusting the content of the high-performance AE agent and the AE agent.
[0013]
The concrete composition of the present invention can be constructed in the same manner as ordinary concrete, and can be used particularly as high-strength concrete.
[0014]
【The invention's effect】
The admixture of the present invention has a chemical composition different from that of conventional fly ash and can use a specific by-product of a pressurized fluidized bed. Can be reduced to improve strength. Moreover, since the concrete composition of the present invention contains the admixture of the present invention, high-strength concrete can be obtained at low cost.
[0015]
【Example】
Hereinafter, although an Example demonstrates further in detail, this invention is not limited to these.
Example 1
Coal ash produced from the secondary cyclone of a pressurized fluidized bed power plant that causes coal to undergo a combustion reaction with limestone powder was recovered. As a result of analyzing the recovered coal ash by converting the chemical component into the amount of oxide with a fluorescent X-ray analyzer, SiO ₂ 37.0 wt%, Al ₂ O ₃ 31.1 wt%, Fe ₂ O ₃ 6.6 wt% %, CaO 13.8 wt%, MgO 0.4 wt%, SO ₃ 6.9 wt% and K ₂ O 0.2 wt%. The specific gravity of the coal ash was 2.72, the specific surface area was 15780 cm ² / g, and the particle size passed through all the 45 μm sieves.
Using the recovered coal ash as an admixture, concrete compositions having the compositions shown in Table 1 were prepared and cured. The kneading of the concrete composition was performed by first kneading cement, admixture, fine aggregate, and aggregate for 10 seconds, then adding water and a high-performance AE water reducing agent, and kneading for 120 seconds. Cement is ordinary Portland cement (specific gravity 3.16, specific surface area 3280 cm ² / g), fine aggregate is river sand (specific gravity 2.62, water absorption 1.49%), coarse aggregate is crushed stone with a maximum diameter of 20 mm ( Specific gravity 2.72, water absorption 0.60%) was used. Moreover, the slump and the amount of air were adjusted by appropriately adding a high-performance AE water reducing agent comprising a polycarboxylic acid ether and a crosslinked polymer and an AE agent comprising a modified alkylcarboxylic acid surfactant. As a control, concrete with no admixture was also prepared. The compressive strength at age 7, 28 and 56 days of each concrete obtained was measured according to JIS A 1108. The results are shown in Table 1.
From the results in Table 1, when the coal ash is blended, the strength is almost the same as that not blended at the age of 7 days, and the strength is enhanced compared to that not blended after the age of 28 days. Therefore, it can be seen that this coal ash functions as an admixture. Moreover, the strength of concrete mixed with this admixture increases.
[0016]
[Table 1]

Claims (4)

SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO and SO ₃ , SiO ₂ content 30 to 40 wt%, Al ₂ O ₃ content 15 to 35 wt%, Fe ₂ O ₃ content 1 to 10% by weight, CaO content is 10 to 30% by weight, SO ₃ content is 3.0 to 10% by weight, and the specific surface area is made of coal ash with a specific surface area of 10,000 cm ² / g or more. An admixture characterized by that.   2. The admixture according to claim 1, wherein the coal ash is coal ash collected from a dust collection facility after the coal for desulfurization is subjected to a combustion reaction in a pressurized fluidized bed together with limestone powder.   A concrete composition comprising cement, aggregate, water and the admixture according to claim 1 or 2.   The ratio of water / (cement + admixture according to claim 1 or 2) is 55 to 30% by weight, and the admixture according to claim 1 or 2 (cement + claim 1 or 2). The concrete composition according to claim 3, wherein the content ratio is 15 to 30% by weight.