KR20120117108A - A non-sintering binder having bottom ash - Google Patents

Abstract

PURPOSE: A binder including bottom ash is provided to manufacture non-cement mortar or non-cement concrete with excellent compressive strength and constructability. CONSTITUTION: A binder including bottom ash comprises alkali active agent which is composed of bottom ash, alkali aqueous oxide and silicate. The alkali active agent for the bottom ash is 55-65 % in weight ratio. The weight ratio of the silicate to the alkalinity aqueous oxide is 1:1. The fineness of the bottom ash is 3,800-4,100cm^2/g. The alkali aqueous oxide is 6-16M of NaOH. The silicate is sodium silicate. The molar ratio of SiO2 of sodium silicate to Na2O is 1.0-3.4. The mortar is composed of fine aggregate, water and a binder which is composed of bottom ash. The concrete is composed of fine aggregate, coarse aggregate, water and the binder composed of bottom ash. [Reference numerals] (AA) Strength(Mpa); (BB) Flow(mm); (CC) Weight ratio of alkali active agent and bottom ash; (DD) Slump

Description

A Non-sintering Binder Having Bottom Ash}

The present invention relates to a non-baking binder comprising a bottom ash, more specifically, to a binder in which sodium hydroxide and sodium silicate are blended with an appropriate ratio of bottom ash, an alkali activator, instead of cement, which emits a large amount of carbon dioxide by plastic working. By providing the non-fired and industrial waste bottom ash can be used to provide an environmentally friendly binder, when manufacturing the mortar or concrete using such a binder non-plastic binder that can be provided with a compressive strength of 50MPa-class cement-free mortar or concrete It is about.

With various efforts to prevent global warming (adopted in 1997, ending the Kyoto Protocol in effect in 2005), in December 2007, the Bali Roadmap was adopted in Bali, Indonesia, until 2009. Negotiations are in progress for a climate change agreement. Accordingly, there is a need to significantly reduce the amount of greenhouse gas emissions such as carbon dioxide worldwide.

Meanwhile, since the cement industry is a major carbon dioxide emission industry along with the steel industry, it produces about 0.9 tonnes of carbon dioxide to produce 1 tonne of cement, which is the basis for the production of concrete. Is urgently required.

Domestic cement production is about 60 million tons per year, releasing about 54 million tons of carbon dioxide. As part of the breakthrough for such environmental pollution, researches to replace cement using industrial by-products are constantly being conducted. Although blast furnace slag and metakaolin are mixed with cement at home and abroad, they have been widely applied to concrete. However, this method has a limit in dramatically reducing carbon dioxide.

Overseas, the technique of alkali-activated cement (concrete) by polymerization is conceptually established by Davidovits (France) in 1978 as a mechanism for using kaolinite minerals and having a structure similar to zeolite. There was no practical use because of economics.

In the prior art, there is a case in which metakaolin is used, but since the kaolin is calcined at 700 to 800 ° C. to use metakaolin, carbon dioxide is discharged in this process, and the price is high, thereby making it practical.

On the other hand, fly ash (fly ash) is mostly consumed as cement raw materials and concrete admixtures among coal ashes generated from thermal power plants.Bottom ash (floor ash) occupies about 15-25% of coal ash generated. Most of them are disposed of in landfills, which impedes economic losses due to huge disposal costs and the effective use of land due to landfill growth. Accordingly, research on cement mortar or concrete using bottom ash together with cement or as a substitute is being conducted.

Therefore, the present inventors proposed the present invention by repeatedly researching and experimenting to use the bottom ash as a mortar or a binder of concrete, and the present invention is a physically activated bottom ash instead of cement which emits a large amount of carbon dioxide during manufacture. Sodium hydroxide and sodium silicate as an alkali activator is formulated in an appropriate mixing ratio, it is an object to provide a binder that can be produced excellent cement mortar or cement cement concrete in the workability and compressive strength.

The non-baking binder including the bottom ash of the present invention for achieving the above object includes an alkali activator consisting of bottom ash and alkaline hydroxide and silicate, the alkali activator for the bottom ash 55 to 65% by weight It is characterized by being%.

The bottom ash refers to coal ash that is attached to a furnace wall when pulverized coal is burned and dropped to the bottom of the boiler by its own weight. The bottom ash reacts with an alkali activator to harden by an individual agglomeration process with Si and Al components. It has a mechanism

The hardening process of mortar or concrete to which the binder of the present invention is applied may be classified into 1) formation of precursors through the synthesis of hydroxide ions, 2) partial reconstitution of alkali-silica, and 3) reprecipitation for formation of inorganic structures. .

Thus, in the mortar or concrete to which the binder of the present invention is applied, the H 2 O / SiO 2 ratio is also important in addition to the Al / Si ratio. This is because H 2 O plays an important role in the dissolution of aluminum and silica ions.

In the present invention, the strength is enhanced by inducing a polymerization reaction (Polymersation) through a combination of an alkali activator consisting of bottom ash, alkaline hydroxide and silicate, and finally expresses a certain strength or more without using a cement without firing. It is to provide a binder that can be.

In the present invention, as the alkaline hydroxide, sodium hydroxide is preferably used, and silicate is preferably sodium silicate. Thus, the binder of the present invention is composed of bottom ash (A), sodium hydroxide (B) and sodium silicate (C), wherein the ratio of the sum of sodium hydroxide and sodium silicate (B + C) to the bottom ash (A) is It is reasonable that the weight ratio ((B + C) / A) is comprised between 55% and 65%. As such, the weight ratio (A: B + C) of the alkali activator to the bottom ash in the binder was 55% to 65%, and Si and Al and Na in the appropriate ratio required for the polymerization reaction were present. If the weight ratio is less than 55%, Na is relatively insufficient for the reaction, and the strength is lowered. On the contrary, if it exceeds 65%, the strength is reduced due to the lack of Si or Al, which contributes to the strength. As the amount of water contained in the agent increases, the slump increases, but in addition to the water required for the dissolution process of aluminum and silica ions, the residual water causes a decrease in strength, thereby limiting the mixing ratio as described above.

In addition, it is preferable that the weight ratio of sodium hydroxide and sodium silicate constituting the alkali activator is 1: 1, which shows that when a large amount of sodium hydroxide is used, the molar concentration of the mixed solution decreases, causing condensation and increasing water content. It may cause a decrease in strength. On the contrary, in the case of using less sodium hydroxide, the production of aluminosilicate is reduced at the early stage of the age, and thus the initial strength is lowered and the shrinkage is slightly increased. Therefore, a large amount of sodium silicate must be used to reinforce it. There is a problem to be limited in this way.

In addition, it is preferable to use the bottom ash having a powder of 3,800 ~ 4,100 ㎠ / g, which has a low reactivity to 1,500 ~ 1,700 ㎠ / g of the bottom ash raw material is disadvantageous in strength expression, 5,000 ㎠ / This is because high powders of more than g have high reactivity, but are inferior in construction properties, and may take a long time to fine powder, thereby degrading economic efficiency.

In addition, it is preferable to use the sodium silicate having a molar ratio of SiO ₂ and Na ₂ O in the range of 1.0 to 3.4. When the molar ratio is less than 1.0, the viscosity of the binder increases rapidly and the slump is lowered, resulting in poor workability. In addition, since the Si component required for the polymerization reaction is small, the long-term strength is decreased, and when the molar ratio exceeds 3.4, it does not affect the workability, but there is a problem that the initial strength is decreased due to the decrease of Na ions. . Furthermore, the silicic acid to obtain excellent workability and strength than sodium, it is more preferable to use the molar ratio of SiO ₂ and Na ₂ O 2.8 ~ 3.2.

As the alkaline hydrate, sodium hydroxide is used, with sodium hydroxide in the range of 6 to 16 M being preferred. If less than 6M is used, the amount of bottom ash is insufficient than necessary for all reactions, and sufficient alkali activation reaction does not occur, which may reduce the strength. If more than 16M is used, the amount of alkali hydrate material is relatively expensive. This is because the strength improvement effect is insignificant, which is disadvantageous in economic terms.

Meanwhile, the present invention may be composed of cement mortar by blending fine aggregate and water in the non-baking binder including the bottom ash mentioned above, and mixing coarse aggregate, fine aggregate, and water in the non-baking binder including the bottom ash. Cementless concrete can be constructed. In such mortars and concrete, admixtures, reinforcing fibers, etc. may be reinforced as necessary.

The non-plastic binder including the bottom ash of the present invention as described above can secure a compressive strength range of 30 to 50 MPa at high temperature curing depending on the mixing ratio, thereby providing a cement mortar or cement concrete.

In addition, the non-plastic binder including the bottom ash of the present invention has the advantage that it can be sufficiently applied as a binder to maintain sufficient fluidity during a certain time when the mortar or concrete manufacturing, including this has the advantage that there is sufficient applicability.

In addition, by using the non-plastic binder including the bottom ash of the present invention a large amount of CO ₂ generated during cement production by completely replacing the cement Since the generation of gas can be reduced and the bottom ash, which is an industrial by-product, is recycled, there is an advantage in that not only an economic burden for securing landfills but also many environmental problems caused by leachate generated during landfill can be reduced.

1 is a graph showing the slump and compressive strength results according to the mass ratio of the alkali activator and the bottom ash as a binder component.
Figure 2 is a graph showing the slump and compressive strength results according to the mixing ratio of the alkali activator of the binder material, that is, the mixing ratio of sodium silicate and sodium hydroxide.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Since the embodiment according to the present invention may be modified in various other forms, the scope of the present invention is not limited to the embodiments described below.

In the embodiment of the present invention, in order to analyze the effect of the bottom ash and alkali activator (sodium hydroxide, sodium silicate) in the production of mortar using the binder according to the invention provides an experimental example under two conditions. First, the effect of the weight ratio of alkali activator on bottom ash was analyzed. At this time, sodium hydroxide and sodium silicate constituting the alkali activator is blended in a weight ratio of 1: 1. Second, while fixing the relative weight of the bottom ash and the relative weight of the alkali activator, the effect of the mixing ratio between sodium hydroxide and sodium silicate constituting the alkali activator was analyzed.

≪ Example 1 >

Alkali activators  Weight ratio effect

The weight ratio of bottom ash and alkali activator is 100: 55 in bottom ash, alkali activator (sodium hydroxide (NaOH) 9M, sodium silicate having a molar ratio of SiO ₂ / Na ₂ O of 3.2) having a powder degree of 4,000 cm 2 / g. 100: 60, 100: 65, and 100: 70, where the weight ratio of sodium hydroxide and sodium silicate is used in a 1: 1 ratio, and the aggregate is composed of SiO ₂ to minimize the influence of other materials. Australian silica sand, which is 99.7%, was used.

The mortar thus prepared was subjected to a slump test according to KS L 5111, a 50 × 50 × 50mm cube test body was prepared, cured at 60 ° C. for 2 days, demolded, and then demolished at room temperature (humidity 50 ± 5%, temperature 20 ±). 2 ° C.) was cured and measured according to KS F 5105 at 28 days of age. The results are summarized in FIG. 1.

As can be seen in Figure 1, when the relative weight ratio of the alkali activator to the weight of the bottom ash is less than 55%, the compressive strength is advantageous but the slump is small, when 60 ~ 65% the slump and the compressive strength is good However, when it exceeds 65%, the slump is large, but the strength decreases. In other words, Si and Al and Na in the proper ratio required for the polymerization reaction are present, but if the weight of the bottom ash is constant, but the amount of the alkali activator is large, the lack of Si or Al contributing to the strength is the cause of the decrease in strength, alkali activation As the amount of water contained in the agent increases, the slump grows, but the remaining water in addition to the water required for the dissolution process of aluminum and silica ions is thought to cause a decrease in strength. Therefore, it is judged that the relative weight ratio of the alkali activator to the weight of the bottom ash is 55% to 65%, which is a proper blending ratio in terms of strength and slump. More preferably, the relative weight ratio of the alkali activator to the weight of the bottom ash is 60 to 65. It is reasonable to be%.

<Example 2>

Sodium hydroxide and Sodium silicate  Weight ratio effect

The bottom ash having a powder degree of 4,000 cm 2 / g, an alkali activator (sodium hydroxide (NaOH) 9M, sodium silicate having a molar ratio of SiO ₂ / Na ₂ O is 3.2), but the bottom ash as seen in Example 1 And an alkali activator at an appropriate weight ratio of 100: 60, and a weight ratio of sodium silicate and sodium hydroxide constituting the alkali activator is 20:40, 30:30, 36:24, and 40:20, respectively. Used. That is, the aggregate is minimized the influence of other materials on the binder compound containing alkali activator: sodium silicate: sodium hydroxide at 100: 20: 40, 100: 30: 30, 100: 36: 24, and 100: 40: 20, respectively. For this purpose, Australian silica sand having a 99.7% SiO ₂ component was used.

In this example, the mortar thus prepared was subjected to a slump test according to KS L 5111, a 50 × 50 × 50 mm cube test body was prepared, cured at 60 ° C. for 2 days, and then demolded, and then at room temperature (humidity 50 ± 5%). Curing was carried out at a temperature of 20 ± 2 ° C.) and measured according to KS F 5105 at 28 days of age. The results are summarized in FIG. 2.

As can be seen in Figure 2, when the relative weight ratio of the bottom ash and alkali activator is constant, the mixing ratio of sodium silicate and sodium hydroxide is 20:40 (1: 2) (corresponding to the horizontal axis 0.5 in Figure 2) It was large, but it was small in terms of early strength and long term strength. In this case, the more sodium hydroxide, the greater the water content, the larger the slump, but relatively lack of sodium silicate, it is judged to be the cause of the decrease in strength. In addition, when the mixing ratio is 36:24 (1.5: 1) (corresponding to the horizontal axis 1.5 in FIG. 2) and 40:20 (2: 1) (corresponding to the horizontal axis 2 in FIG. 2), the slump is constant but the compressive strength gradually increases. It was found to degrade. In this case, as the amount of sodium silicate is increased, the viscosity of the activator is increased and the slump is lowered. Therefore, as can be seen in the present embodiment, the most preferable compounding ratio of the alkali activator is sodium silicate in view of the slump of the water content of sodium hydroxide and the strength of the contribution of Na of sodium hydroxide and Si of sodium silicate. It is considered reasonable that the sodium hydroxide is mixed in a weight ratio of 1: 1.

From the above results, the bottom ash, sodium hydroxide, sodium silicate composition ratio is 55% to 65% of the weight ratio of the alkali activator to the bottom ash, mortar using the same when the weight ratio of sodium silicate and sodium hydroxide is 1: 1 Alternatively, the concrete exhibits excellent workability and compressive strength, so that the binder of the present invention can completely replace cement.

Claims (8)

A non-plastic binder comprising a bottom ash and an alkali activator comprising an alkali hydroxide and a silicate, wherein the alkali activator is 55% to 65% by weight. The method of claim 1,
Non-plastic binder comprising a bottom ash, characterized in that the alkali hydroxide and silicate constituting the alkali activator is 1: 1 by weight. The method of claim 1,
The non-plastic binder containing the bottom ash, characterized in that the powder of the bottom ash is 3,800 ~ 4,100 ㎠ / g. The method of claim 1,
The alkaline hydroxide is a non-plastic binder comprising a bottom ash, characterized in that sodium hydroxide in the range of 6 to 16M. The method of claim 1,
The silicate is a non-plastic binder comprising a bottom ash, characterized in that sodium silicate. 6. The method of claim 5,
The sodium silicate is a non-plastic binder comprising a bottom ash, characterized in that the molar ratio of SiO ₂ and Na ₂ O is 1.0 to 3.4. In mortar composed of fine aggregate, water, binder,
The binder is mortar, characterized in that the binder of any one of claims 1 to 6. In concrete composed of fine aggregate, coarse aggregate, water, binder,
The binder is concrete, characterized in that the binder of any one of claims 1 to 6.

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