CN1718557A - Expanding agent used for cement or concrete and its manufacturing method - Google Patents

Abstract

A bulking agent for cement or concrete is prepared from Al-contained garbage (Al slags for example), soluble calcium oxide and soluble sulfate through proportional mixing, adding water, reacting to obtain ettringite, and calcining at 60-900 deg.C to obtain said product containing amorphous phase, calcium aluminate and calcium thioaluminate.

Description

Expansive agent for cement or concrete and its production method

Technical Field

The present invention relates to a composition and a method for manufacturing the same, and more particularly, to an expanding agent for cement or concrete and a method for manufacturing the same, which can reduce heat energy consumption and cost.

Background

To improve the natural property of concrete shrinkage, obtaining a certain degree of expansion at the early stage of hardening is an important means, and for this reason, various types of expansive cements and expansive agents are competitively developed for use in various countries around the world, and the expansive agents are added into concrete to expand so as to compensate the shrinkage of the concrete and further reduce the generation of shrinkage cracks.

In 1965, before the invention of the expanding agent in Japan, both the U.S. and the English countries generate expansion in the early hardening stage of cement mortar or concrete by means of ettringite, Calcium Sulphoaluminate (CSA) and lime type expanding agents are further developed and produced, the calcium sulphoaluminate and lime type expanding agents become the earliest world using expanding agents, and the clinker and part of gypsum are respectively calcined and then are mixed in proportion during grinding.

As far as the development is concerned, various types of expanding agents added to cement or concrete are known, such as calcium oxide (CaO), magnesium oxide (MgO), C₄A₃S(4CaO_iDAl₂O_iDSO₃) High alumina cement type, etc.; there are three types of reactions: hydration of calcium oxide (CaO) to Ca (OH)₂Hydration of magnesium oxide (MgO) to Mg (OH)₂And C₄A₃S is hydrated to form hydrated calcium sulphoaluminate(i.e. ettringite). Because the expansion amount of calcium oxide (CaO) and magnesium oxide (MgO) in the expansion process is difficult to accurately control, the calcium oxide (CaO) and the magnesium oxide (MgO) are rarely used as main components in the expanding agent at present, and the hydrated calcium sulphoaluminate (namely ettringite) is considered to be an expansion source which can be mainly utilized at present and in the future.

Therefore, in the starting point of not reducing the quality requirement of raw materials and greatly reducing the cost, the inventor develops a new manufacturing process of the expanding agent, namely, the calcination and mixing of the gypsum material are completed by two working procedures, firstly, limestone, gypsum and aluminum ore are respectively crushed and uniformly mixed, and are calcined at the high temperature of 1200-1400 ℃ in a rotary kiln to prepare calcium sulfate clinker, and finally, the clinker and the gypsum are mixed, ground and added with a proper amount of limestone to generate the CSA type expanding agent.

However, although the above-mentioned method for manufacturing the expanding agent can manufacture the expanding agent for use, since the components to be mixed are all solid phases, the three solid phase components must be synthesized by calcining at a high temperature of 1200 ℃ or higher in a rotary kiln, and thus the high energy consumption in the manufacturing process increases the manufacturing cost.

Disclosure of Invention

The invention aims to provide an expanding agent for cement or concrete and a manufacturing method thereof, wherein the expanding agent can effectively reduce the consumption of heat energy in the manufacturing process so as to save the cost.

In order to achieve the purpose, the technical solution of the invention is as follows:

the invention is an expanding agent for cement or concrete, which comprises waste, soluble calcium oxide and soluble sulfate compound; the waste contains compounds capable of dissociating aluminum ions, and the mole ratio of the compounds capable of dissociating aluminum ions in the waste to soluble calcium oxide to soluble sulfate is 2: 3-40: 3-18, namely: ca2 +: Al3 +: SO42- ═ 3-40 to (2) to (3-18), or CaO: Al2O3 to CaSO4 to (3-40) to (1) to (3-18).

The amount of aluminum ions dissociated from the waste was 2 mol, and 3 mol of soluble calcium oxide (CaO) and 3 mol of soluble sulfate (CaSO) were required₄) Mixing the two with each other.

A method for manufacturing an expanding agent for cement or concrete, the manufacturing method comprising the following steps in sequence:

(1) mixing and stirring: preparing waste capable of dissociating aluminum ions, and soluble calcium oxide, soluble sulfate and other compounds, and mixing the three components at normal temperature;

(2) the reaction steps are as follows: mixing all the above-mentioned compounds uniformly, adding water, using said water as medium to synthesize ettringite by reaction;

(3) and (3) calcining: calcining the ettringite at a temperature ranging from 60 ℃ to 900 ℃ so as to change the phase change of the ettringite to form an expanding agent for adding in cement or concrete.

Between the reaction step and the calcination step, a degassing step is further included to remove excess gas generated during the generation of the reaction step.

Between the degassing step and the calcining step, a water removing step is further included for removing excess free water after the reaction in the reaction step.

The waste may contain any one of aluminum nitride, aluminum hydroxide or metal aluminum powder or a combination of any two or more of them.

The soluble calcium oxide can be quicklime and slaked lime.

The soluble sulfate can be dihydrate gypsum, semi-hydrate gypsum, anhydrous gypsum and sodium sulfate.

The phase change formed by the ettringite in the calcination step can be an amorphous phase.

The phase change formed by the ettringite in the calcining step can be mainly calcium aluminate and calcium sulphoaluminate.

After the scheme is adopted, the invention is based on the utilization of the aluminum ion waste obtained by dissociation, thereby reducing the cost and saving the expense.

The manufacturing method of the invention sequentially comprises a mixing step, a reaction step and a calcination step; the three components are mixed in a certain proportion at normal temperature, then in the reaction step, water is added into the mixed mixture separately and the water is used as medium to react and synthesize ettringite, finally in the calcination step, the ettringite in the reaction product is calcined at the temperature of more than 60 ℃ and less than 900 ℃ so as to change the phase change of the ettringite into an amorphous phase or other crystalline phases, the ettringite is suitable for being added into cement or concrete to be used as an expanding agent, in addition, raw material sources are recovered from the waste in the manufacturing process, the raw material cost can be effectively reduced, and a high-temperature manufacturing process is not needed, so that the cost consumption can be reduced.

The invention is further described with reference to the following figures and specific embodiments.

Drawings

FIG. 1 is a flow chart of a method of manufacturing a preferred embodiment of the present invention;

FIG. 2 is a test X-ray diffraction pattern of the example illustrating the relationship of the calcination temperature and the calcination phase;

FIG. 3 is a test chart of this example, illustrating the different expansion properties of the expanding agent at different calcination temperatures.

Detailed Description

Referring to fig. 1, a preferred embodiment of the present invention sequentially comprises a mixing step 1, a reaction step 2, a degassing step 3, a water removal step 4, and a calcination step 5.

(1) Mixing step 1: firstly, preparing waste capable of dissociating aluminum ions, and soluble calcium oxide, soluble sulfate and other compounds, wherein:

1. soluble calcium oxide, such as quicklime, slaked lime, etc., is represented by quicklime in this embodiment.

2. Soluble sulfates such as dihydrate gypsum, hemihydrate gypsum, anhydrite, sodium sulfate, etc., are represented by anhydrite in this example.

3. The waste that can be dissociated to produce aluminum ions, such as aluminum slag, or the waste contains aluminum nitride, aluminum hydroxide, aluminum powder, etc., but the waste can be any compound or a combination of two or more compounds⁺⁺⁺The so-called soluble aluminum is simply called soluble aluminum hereinafter, and the proportion analysis of the aluminum slag composition phase sampled at this time is further analyzed to obtain:

Al₂O₃--------------------------50％

MgAl₂O₄------------------------20％

aluminum nitride (AlN) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -15%

Aluminum (Al) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Other impurities- -10%, etc

Of course, the obtaining of the aluminum slag varies with the plant type, the production period, etc. of the sampled aluminum slag, and the sample is only one of the samples obtained in this embodiment, and of course, the sample can be obtained from waste or other industrial byproducts besides aluminum slag; furthermore, since the aluminum slag obtained in this embodiment contains aluminum nitride (AlN) and aluminum (Al), ammonia (NH) will be generated in the subsequent manufacturing process₃) With hydrogen (H)₂) If the aluminum dross sample contains only Al (OH)₃It can be synthesized without generating gas, so it is obvious.

α is used by aluminum slag_(g)For example, the weight of soluble aluminum that can be dissociated from the aluminum dross sampleComprises the following steps:

AlN＝0.15α_(g)，Al＝0.05α_(g)

therefore, the temperature of the molten metal is controlled,

(containing I)

The molar number of total soluble aluminium istherefore:

$\frac{0.15\mathrm{\α}}{41}+\frac{0.05\mathrm{\α}}{27}=0.00551\mathrm{\α}$

in view of the reactively synthesized ettringite formula:

(CaO)₃.(Al₂O₃).(CaSO₄)₃.32H₂O_(S)

therefore, CaO and Al are contained in the alloy₂O₃、CaSO₄The molar ratio of (A):

CaO∶Al₂O₃∶CaSO₄＝3∶1∶3

can also be converted into Ca²⁺∶Al³⁺∶SO₄ ^2-＝3∶2∶3

As can be seen from the analysis of the chemical formula of procalcitonite and the molar ratio, at least 3 mol CaO and at least 3 mol CaSO are required per 2 mol of aluminum ions₄Can be completely reacted if 2 mol of aluminum ions are converted into Al₂O₃Namely 1 mol; so, Al is utilized as follows₂O₃The molar amount of the total soluble aluminum was 0.00551 α, thus converted to Al, for the calculation basis₂O₃Is composed of

Mole, and the respective requirements:

$\mathrm{CaO}\≥3\×\left(\frac{0.00551\mathrm{\α}}{2}\right)$ mole ear

$\mathrm{CaS}{O}_4\≥3\×\left(\frac{0.00551\mathrm{\α}}{2}\right)$ Mole ear

Therefore, the following steps are carried out:

(1) quicklime (CaO): at least

Mole ear

(2) Gypsum (CaSO)₄): at least

Mole ear

(3) Aluminum slag-soluble aluminum available in Moore (0.00551 α)

The three compounds existing in solid phase are further uniformly mixed at normal temperature, and the weight ratio of the mixture is as follows:

quicklime (CaO): aluminum slag: gypsum (CaSO)₄)

$=(3\×\frac{0.00551\mathrm{\α}}{2}\×56):$ α： $(3\×\frac{0.00551\mathrm{\α}}{2}\×136)$

$=0.4629:1:1241$

(2) And 2, reaction step: the uniformly mixed compounds are separately mixedAdding water and using the water as a medium to synthesize ettringite by reaction, wherein the reaction formula can be expressed by the following two reaction formulas: ..(1) ..(2)

furthermore, since the obtained aluminum slag sample contains aluminum nitride (AlN) and aluminum (Al), excessive gases such as ammonia and hydrogen are generated during the reaction in the reaction step 2.

(3) And (3) degassing: since the excess gas such as ammonia and hydrogen generated in the reaction process of the reaction step 2 generally escapes into the atmosphere along with stirring, disturbance and other actions, the quality of the expanding agent produced in the future is not affected, and the current relevant regulations are checked, only taiwan industrial safety regulations indicate that the ammonia concentration in the working environment must be less than 50PPM, and certainly, in the embodiment, in order to better meet the current taiwan industrial safety regulations, the degassing step 3 is further performed to remove the excess gas according to whether the excess gas is generated or not, so as to improve the safety of the working environment.

(4) And (4) dewatering: thereby removing the excessive free water after the reaction in the reaction step 2 and facilitating the subsequent treatment.

(5) The calcination step 5 is to calcine the ettringite at a temperature ranging from 60 ℃ to 900 ℃ to change the amorphous phase (amorphous) of the ettringite or other phases such as main calcium aluminate and calcium sulfoaluminate to form a latent expansive material suitable for being added into cement or concrete as an expanding agent.

Referring to fig. 1 and 2, if no gas is generated from other sampled wastes, and it is considered that the process of the calcination step 5 is not required to be performed after the reaction step 2, but the sampled aluminum slag contains gas, so the calcination step 5 in this embodiment is to calcine ettringite obtained after the degassing step 3 and the dewatering step 4, and when the ettringite is calcined from low temperature to high temperature, tests show that when the ettringite is calcined from low temperature to high temperatureWhen the ettringite is calcined at a calcination temperature of 300 ℃ or lower, the crystal phase formed by the ettringite is in an amorphous phase (amorphous) state by removing crystal water, and when the calcination temperature is further continuously increased to 600 ℃, the ettringite is clearly decomposed into C₁₂A₇+ CS + C (where C denotes CaO and A denotes Al₂O₃S table SO₃) When the calcination temperature reaches 900 ℃, ettringite is decomposed to form C₄A₃S+C₁₂A₇+ CS + C (where C denotes CaO and A denotes Al₂O₃S table SO₃) That is, the crystal phases of calcium aluminate and calcium sulphoaluminate are changed, so that the amorphous phase (amorphous) formed by ettringite or other crystal phases mainly comprising calcium aluminate and calcium sulphoaluminate can be changed along with the change of the calcination temperature.

Referring to fig. 3, the specific compound and the expansion function of the expansion agent obtained from the manufacturing process are tested by the ASTM C806 test method, that is, the expansion effect is obtained by comparing the expansion rate data when the expansion agent is added and 20% is used as the basis of the expansion rate test and the calcination temperature range is heated from normal temperature to 900 ℃, and only the linear changes of the calcination temperature at 120 ℃, 300 ℃, 600 ℃ and 900 ℃ are respectively displayed, the data obtained from the test proves that the expansion agent composition obtained when the combustion temperature is not higher can be suitable for being added into cement or concrete to be used as the expansion agent, and the expansion effect can be controlled by the addition amount.

In conclusion, the present invention utilizes the waste capable of dissociating aluminum ions, soluble calcium oxide, soluble sulfate, etc. to mix, and uses water as reaction medium, and then timely supplements the steps of degassing, dewatering and calcining to form the expansion agent with potential expansibility, so that the present invention is suitable for being added into cement or concrete.

However, the above description is only a preferred embodiment of the present invention, and should not be taken as limiting the scope of the invention, i.e., the invention is not limited by the claims and the description of the invention.

Claims (10)

1. An expanding agent for cement or concrete, characterized in that: it comprises waste, soluble calcium oxide and soluble sulfate compound; the waste contains compounds capable of dissociating aluminumions, and the mole ratio of the compounds capable of dissociating aluminum ions in the waste to soluble calcium oxide to soluble sulfate is 2: 3-40: 3-18.

2. The expanding agent for cement or concrete according to claim 1, characterized in that: the amount of aluminum ions dissociated from the waste was 2 mol, and 3 mol of soluble calcium oxide (CaO) and 3 mol of soluble sulfate (CaSO) were required₄) Mixing the two with each other.

3. A method for producing an expansive agent for cement or concrete according to claim 1, wherein: the manufacturing method sequentially comprises the following steps:

(1) mixing and stirring: preparing waste capable of dissociating aluminum ions, and soluble calcium oxide, soluble sulfate and other compounds, and mixing the three components at normal temperature;

(2) the reaction steps are as follows: mixing all the above-mentioned compounds uniformly, adding water, using said water as medium to synthesize ettringite by reaction; and

(3) and (3) calcining: calcining the ettringite at a temperature ranging from 60 ℃ to 900 ℃ so as to change the phase change of the ettringite to form an expanding agent for adding in cement or concrete.

4. The method for producing an expansive agent for cement or concrete according to claim 3, further comprising, between the reacting step and the calcining step, a degassing step of removing an excess gas generated during the generating step of the reacting step.

5. The process for producing an expansive agent for cement or concrete according to claim 4, wherein:

the method further comprisesa water removal step between the degassing step and the calcination step for removing excess free water after the reaction in the reaction step.

6. The expanding agent for cement or concrete according to claim 1, wherein:

the waste may contain any one or a combination of two or more of aluminum nitride, aluminum hydroxide and aluminum powder.

7. The expanding agent for cement or concrete according to claim 1, wherein:

the soluble calcium oxide can be quicklime or slaked lime.

8. The expanding agent for cement or concrete according to claim 1, wherein:

the soluble sulfate can be dihydrate gypsum, hemihydrate gypsum, anhydrite and sodium sulfate.

9. The process for producing an expansive agent for cement or concrete according to claim 3, wherein:

the phase change formed by the ettringite during the calcination step may be an amorphous phase.

10. The process for producing an expansive agent for cement or concrete according to claim 3, wherein:

the phase change formed by the ettringite in the calcination step can be mainly calcium aluminate and calcium sulphoaluminate.

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