阅读说明：本技术 低模数硅酸钠溶液及其制备方法 (Low modulus sodium silicate solution and method for preparing same ) 是由 叶家元 史迪 张文生 于 2019-09-05 设计创作，主要内容包括：本发明是关于一种低模数硅酸钠溶液及其制备方法。该低模数硅酸钠溶液的制备方法包括：在常温条件下,向NaOH溶液中加入纳米SiO<Sub>2</Sub>颗粒,进行搅拌、分散,得到设定模数的低模数硅酸钠溶液。本发明还提供了以该方法制得的低模数硅酸钠溶液作为激发剂制备的碱激发胶凝材料。本发明基于纳米SiO<Sub>2</Sub>颗粒在常温下的强碱溶液中快速溶解而形成单体[SiO<Sub>n</Sub>(OH)<Sup>4-n</Sup>]<Sup>n-</Sup>的原理,纳米SiO<Sub>2</Sub>颗粒发挥对溶液可溶性硅的快速补充作用,快速地获得具有低模数、低粘度、强稳定性特征的硅酸钠溶液。本发明制备方法制得的低模数硅酸钠溶液无论是即配即用还是长时间陈放,纳米SiO<Sub>2</Sub>颗粒均可发挥其效应而改善碱激发胶凝材料性能。(The invention relates to a low modulus sodium silicate solution and a preparation method thereof. The preparation method of the low modulus sodium silicate solution comprises the following steps: and (3) adding nano SiO2 particles into the NaOH solution at normal temperature, stirring and dispersing to obtain the low-modulus sodium silicate solution with the set modulus. The invention also provides an alkali-activated cementing material prepared by using the low-modulus sodium silicate solution prepared by the method as an activator. The invention is based on the principle that nano SiO2 particles are quickly dissolved in strong alkali solution at normal temperature to form monomer [ SiOn (OH)4-n ] n-, nano SiO2 particles play a role in quickly supplementing soluble silicon in the solution, and sodium silicate solution with the characteristics of low modulus, low viscosity and strong stability is quickly obtained. The low-modulus sodium silicate solution prepared by the preparation method can play the effect of the nano SiO2 particles to improve the performance of the alkali-activated cementing material no matter the low-modulus sodium silicate solution is ready to use after being prepared or stored for a long time.)

1. A method for preparing a low modulus sodium silicate solution, comprising:

And (3) adding nano SiO2 particles into the NaOH solution at normal temperature, stirring and dispersing to obtain the low-modulus sodium silicate solution with the set modulus.

2. The method for preparing a low modulus sodium silicate solution according to claim 1,

The addition amount of the nano SiO2 particles satisfies formula (1):

m＝30×c×V×n (1)

In the formula (1), the reaction mixture is,

m is the addition amount of nano SiO2 particles in NaOH solution, unit g;

c is the concentration of NaOH solution, unit mol/L;

V is the volume of NaOH solution, unit L;

n is a set modulus, where 0< n <1.

3. The method for preparing a low modulus sodium silicate solution according to claim 1,

The specific surface area of the nano SiO2 particles is 120-400 m2/g, and the particle size D0.5 is 7-200 nm.

4. The method for preparing a low modulus sodium silicate solution according to claim 1,

The nano SiO2 particles are hydrophilic nano SiO2 particles.

5. the method for preparing a low modulus sodium silicate solution according to claim 1,

The stirring is mechanical stirring, the rotating speed of the stirring is 500-900 r/min, and the time is 10-30 min; the dispersion is ultrasonic dispersion, which is carried out after mechanical stirring, and the dispersion time is 5-10 min.

6. The method for preparing a low modulus sodium silicate solution according to claim 1,

When the modulus n is set to be more than or equal to 0.6, the nano SiO2 particles are divided into two parts with similar mass and added in two times, so as to avoid the problem that stirring cannot be carried out due to one-time addition.

7. A low modulus sodium silicate solution, characterized in that it is prepared by the method of any one of claims 1 to 6.

8. The low modulus sodium silicate solution according to claim 7, wherein the viscosity of said low modulus sodium silicate solution is 10 to 20 mPa-s.

9. An alkali-activated cementitious material, characterised in that it uses as alkali activator the low modulus sodium silicate solution according to claim 7 or 8.

10. The alkali-activated cementitious material of claim 9, wherein the low modulus sodium silicate solution is a clear solution that can be used immediately to prepare the alkali-activated cementitious material without the need for aging after mechanical agitation and ultrasonic dispersion.

Technical Field

The invention relates to the technical field of water glass, in particular to a low-modulus sodium silicate solution and a preparation method thereof.

Background

The alkali activator is the most important component of the alkali-activated cementing material, and dissolves the silicon-aluminum raw material particles and releases silicon and aluminum monomers. The release process of silicon and aluminum monomers is a controlled process of silicon-aluminum polymerization reaction, so that the alkali activator has a crucial influence on the setting and hardening performance, the microstructure development and the performance development of the cementing material. Different raw materials have different requirements on the characteristics of the alkali-activator. For high calcium, high silicon and low aluminum raw materials such as slag, the high modulus (n ═ SiO2/Na2O) water glass solution not only can provide a proper alkaline environment, but also the supply of soluble silicon ((poly) silicate ions) is enough to ensure the smooth progress of silicon-aluminum polymerization reaction. For low-calcium, high-aluminum and high-silicon raw materials such as fly ash, a strong enough alkaline environment material is needed to release silicon and aluminum monomers, so a high-concentration NaOH solution is usually selected. However, the gelled material system prepared by using the fly ash as the raw material only has enough alkaline environment and is not enough to enable the fly ash to quickly release silicon and aluminum monomers at normal temperature, namely the fly ash is abnormally slow in setting and hardening at normal temperature. In order to increase the reaction speed, the curing temperature is generally increased to promote the setting hardening process, promote the formation of microstructures, and increase the strength. The method not only has high energy consumption, but also is only suitable for prefabricated parts, so that the development of normal-temperature maintenance technology is urgently needed.

In order to realize normal temperature curing, additional supplement of silicon monomer in the form of soluble silicon in a cementing material system is a feasible method. The source of soluble silicon may be a sodium silicate solution (water glass). For the cementing material prepared by taking the fly ash as the raw material, because a strong enough alkaline environment is needed, a proper water glass solution (prepared by adding NaOH into a high-modulus water glass solution and needing to be aged for 24 hours to reach the balance) is bound to have the characteristic of low modulus (n is less than 1.0). For low-modulus water glass, the water glass has the characteristics of strong alkali and ionic soluble silicon, is extremely unstable, and can generate crystallization and delamination after being placed for several days. Therefore, the low-modulus water glass as the excitant brings a plurality of uncertain factors to the preparation of the material and the performance regulation thereof, which is extremely unfavorable for industrial production. Therefore, alternatives to soluble silicon supply are also sought.

Disclosure of Invention

The invention mainly aims to provide a preparation method of a low-modulus sodium silicate solution (water glass), and aims to solve the technical problems that the low-modulus sodium silicate solution is ready to use (does not need to be stored for a long time) and has improved stability (can be stored for a long time) when being prepared, and the low-modulus sodium silicate solution has the characteristics of strong alkali and rapid soluble silicon supply.

The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. The invention provides a preparation method of a low-modulus sodium silicate solution, which comprises the following steps:

and (3) adding nano SiO2 particles into the NaOH solution at normal temperature, stirring and dispersing to obtain the low-modulus sodium silicate solution with the set modulus.

The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.

preferably, the method for preparing the low modulus sodium silicate solution, wherein the nano SiO2 particles are added in an amount satisfying formula (1):

m＝30×c×V×n (1)

In the formula (1), the reaction mixture is,

m is the addition amount of nano SiO2 particles in NaOH solution, unit g;

c is the concentration of NaOH solution, unit mol/L;

V is the volume of NaOH solution, unit L;

n is a set modulus, where 0< n <1.

Preferably, in the preparation method of the low-modulus sodium silicate solution, the specific surface area of the nano SiO2 particles is 120-400 m2/g, and the particle size D0.5 is 7-200 nm.

Preferably, in the preparation method of the low-modulus sodium silicate solution, the nano SiO2 particles are hydrophilic nano SiO2 particles.

Preferably, in the preparation method of the low-modulus sodium silicate solution, the stirring is mechanical stirring, the rotating speed of the stirring is 500-900 r/min, and the time is 10-30 min; the dispersion is ultrasonic dispersion, which is carried out after mechanical stirring, and the dispersion time is 5-10 min.

preferably, in the preparation method of the low modulus sodium silicate solution, when the modulus n is set to be more than or equal to 0.6, the nano SiO2 particles are divided into two parts with similar mass and added in two parts, so as to avoid the problem of incapability of stirring caused by one-time addition.

the object of the present invention and the technical problem to be solved are also achieved by the following technical means. The invention provides a low-modulus sodium silicate solution prepared by the preparation method of any one of the above-mentioned materials.

Preferably, the low-modulus sodium silicate solution has a viscosity of 10 to 20mPa · s.

The object of the present invention and the technical problem to be solved are also achieved by the following technical means. According to the alkali-activated cementing material provided by the invention, the low-modulus sodium silicate solution is used as an alkali activator.

The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.

Preferably, the alkali-activated binding material, wherein the low modulus sodium silicate solution is a clear solution, does not need to be aged after mechanical stirring and ultrasonic dispersion, and can be immediately used for preparing the alkali-activated binding material.

by the technical scheme, the low-modulus sodium silicate solution and the preparation method thereof provided by the invention at least have the following advantages:

1. The preparation method of the invention is that a certain amount of nano SiO2 particles are added into NaOH solution at normal temperature, and the sodium silicate solution with low modulus can be obtained after mechanical stirring and ultrasonic dispersion, and can be prepared and used immediately without aging, and is simple and rapid.

2. In the preparation method, only partial particles of the nano SiO2 particles are dissolved in the ready-to-use low-modulus sodium silicate solution, so that the nano SiO2 particles can play a chemical role in providing soluble silicon, and undissolved particles can play a physical filling role and a crystal nucleus role of ultrafine particles, so that the preparation method has an obvious effect of improving the early strength of the alkali-activated binding material; for the low modulus sodium silicate solution that has been aged for a long time, the nano SiO2 particles have completely dissolved, when they only play a chemical role of "providing soluble silicon". Despite the lack of physical filling and nucleation, the soluble silicon is supplied in greater amounts, i.e., the chemical action is exerted more fully, and the strength of the alkali-activated cementitious material is also significantly increased. Therefore, the low-modulus sodium silicate solution prepared by the method can exert the effect of the nano SiO2 particles to improve the performance of the alkali-activated cementing material no matter the low-modulus sodium silicate solution is ready to use after being prepared or is stored for a long time.

3. The nano SiO2 particles added in the method have the characteristic of high activity, can quickly supplement high-activity silicon monomer ([ SiOn (OH)4-n ] n-) of a system, further can realize the preparation of the alkali-activated cementing material from high-silicon and high-aluminum raw materials (such as fly ash) under the normal temperature condition, avoids heating and maintenance, has remarkable energy-saving significance, and also expands the application range of the material (can be used for prefabricated parts and cast-in-place structures).

4. The low-modulus sodium silicate solution prepared by the preparation method disclosed by the invention has the characteristic of low viscosity, the viscosity of the low-modulus sodium silicate solution is 10-20 mPa & s, and the low-modulus sodium silicate solution can be stored for a long time due to the change of the supply state of soluble silicon, so that the low-modulus sodium silicate solution is obviously beneficial to industrial production and application of alkali-activated cementing materials.

5. the method has no influence on the pH value of the solution. The added nano SiO2 particles dissolve rapidly and provide monomers [ SiOn (OH)4-n ] n-, without polymerization, without changing the solution characteristics.

6. The invention is based on the principle that nano SiO2 particles are quickly dissolved in strong alkali solution at normal temperature to form monomer [ SiOn (OH)4-n ] n-, nano SiO2 particles play a role in quickly supplementing soluble silicon in the solution, and sodium silicate solution with the characteristics of low modulus, low viscosity and strong stability is quickly obtained.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.

Drawings

FIG. 1 is a graph of the exotherm rate of a solution after the addition of nano-sized particles of SiO2 to a NaOH solution according to an embodiment of the present invention;

FIG. 2 is a graph showing the change of opacity of a NaOH solution containing nano-SiO 2 particles according to an embodiment of the present invention;

FIG. 3 is a viscosity change curve of a solution after nano SiO2 particles are added into a NaOH solution according to an embodiment of the invention;

FIG. 4 is a FTIR vibration characteristic curve of a solution after adding nano SiO2 particles in NaOH solution according to an embodiment of the present invention;

Figure 5 is a graph of the hydration exotherm rate for a low modulus sodium silicate solution-excited sample according to an embodiment of the present invention.

Detailed Description

to further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description of the embodiments, structures, characteristics and effects of the low modulus sodium silicate solution and the preparation method thereof according to the present invention will be made with reference to the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The embodiment of the invention provides a preparation method of a low-modulus sodium silicate solution, which comprises the following steps:

and (3) adding nano SiO2 particles into the NaOH solution at normal temperature, stirring and dispersing to obtain the low-modulus sodium silicate solution with the set modulus.

In the embodiment of the invention, the addition amount of the nano SiO2 particles is determined according to the set modulus and the concentration of NaOH solution. Before the nano SiO2 particles are added, NaOH solution meeting the set water-cement ratio and concentration needs to be prepared in advance, so that the nano SiO2 particles are more favorably dispersed and quickly dissolved, the low viscosity is kept, the problem that the water in the solution is insufficient, extra water needs to be supplemented when the alkali-activated cementing material is formed is avoided, and the phenomenon that the solution is too high in viscosity and even becomes jelly-shaped and cannot be used due to the fact that the water in the solution is insufficient is avoided.

Preferably, the nano SiO2 particles are added in an amount satisfying formula (1):

m＝30×c×V×n (1)

in the formula (1), the reaction mixture is,

m is the addition amount of nano SiO2 particles in NaOH solution, unit g;

c is the concentration of NaOH solution, unit mol/L;

V is the volume of NaOH solution, unit L;

n is a set modulus, where 0< n <1.

it is important to note that the low modulus of the present invention is relative to current commercial products. The modulus of commercial products (water glass solution, i.e. water solution with dissolved sodium silicate) is usually 2.0-2.4 and 3.0-3.4, so the disclosed modulus range (0.0-1.0) is lower than that of commercial products.

in the embodiment of the invention, before the nano SiO2 particles are added, a NaOH solution meeting the set water-cement ratio of the alkali-activated cementing material and the required concentration of the alkali-activated cementing material is prepared. In general, 450g of powder raw materials are needed in an alkali-activated cementing material mortar experiment, and assuming that the water-cement ratio is gamma and the doping amount of the low-modulus sodium silicate solution is beta (%, in terms of the mass percentage of the Na2O content in the powder raw materials in the alkali-activated cementing material), the water demand m' (in g) for preparing the NaOH solution with the required concentration at the moment satisfies the formula (2):

m’＝450×γ (2)

in the formula (2), the reaction mixture is,

m' is the water demand of the NaOH solution with the required concentration, and the unit g is;

gamma is the set water-cement ratio (mass of water divided by mass of powder raw material) of the alkali-activated cement.

The desired concentration c of the NaOH solution satisfies formula (3):

c＝10×β/(31×γ) (3)

In the formula (3), the reaction mixture is,

c is the required concentration of NaOH solution, unit mol/L;

beta is the doping amount of the low-modulus sodium silicate solution, and is calculated by the mass percentage of the Na2O content in the powder raw material in the alkali-activated binding material;

gamma is the set water-cement ratio (mass of water divided by mass of powder raw material) of the alkali-activated cement.

Under the conditions of water demand and concentration, preparing (9 multiplied by gamma/20) L NaOH solution to meet the set water-cement ratio of the alkali-activated cementing material; the set modulus can be satisfied by adding (15X 9X beta X n/31) g of nano SiO2 particles into NaOH solution.

According to the method, the nano SiO2 particles are added into the NaOH solution, so that the sodium silicate solution with low modulus can be quickly obtained, and the sodium silicate solution has the characteristics of low viscosity and long-term storage.

In the method, for the low-modulus sodium silicate solution which is ready to be prepared, only partial particles of the nano SiO2 particles are dissolved, so that the chemical action of providing soluble silicon can be exerted, the undissolved particles can also exert the physical filling action and the crystal nucleus action of ultrafine particles, and the method has obvious effect on improving the early strength of the alkali-activated cementing material; for the low modulus sodium silicate solution that has been aged for a long time, the nano SiO2 particles have completely dissolved, when they only play a chemical role of "providing soluble silicon". Despite the lack of physical filling and nucleation, the soluble silicon is supplied in greater amounts, i.e., the chemical action is exerted more fully, and the strength of the alkali-activated cementitious material is also significantly increased. Therefore, no matter the low-modulus sodium silicate solution is prepared and used immediately or stored for a long time, the nano SiO2 particles can exert the effect to improve the performance of the alkali-activated cementing material.

The nano SiO2 particles added in the method have the characteristic of high activity, and can quickly supplement high-activity silicon monomer ([ SiOn (OH)4-n ] n-) of the system, thereby realizing the preparation of alkali-activated cementing material from high-silicon and high-aluminum raw materials (such as fly ash) under the condition of normal temperature and avoiding heating and maintenance. The method has no influence on the pH value of the solution. The added nano SiO2 particles dissolve rapidly and provide monomers [ SiOn (OH)4-n ] n-, without polymerization, without changing the solution characteristics.

Compared with the existing commercial products, the sodium silicate solution with the modulus of less than or equal to 0.5 (0< n ≦ 0.5) is called the ultra-low modulus sodium silicate solution in the embodiment of the invention. The method has more outstanding advantages in preparing the sodium silicate solution with the ultralow modulus and n less than or equal to 0.5: based on the principle that nano SiO2 particles are quickly dissolved in a normal-temperature strong alkali solution to form a monomer [ SiOn (OH)4-n ] n-, nano SiO2 particles play a role in quickly supplementing soluble silicon in the solution, and the sodium silicate solution with the characteristics of ultralow modulus, ultralow viscosity and strong stability is quickly obtained.

Preferably, the specific surface area of the nano SiO2 particles is 120-400 m2/g, and the particle size D0.5 is 7-200 nm.

Preferably, the nano SiO2 particles are hydrophilic nano SiO2 particles.

Preferably, the stirring is mechanical stirring, the rotating speed of the stirring is 500-900 r/min, and the time is 10-30 min; the dispersion is ultrasonic dispersion, which is carried out after mechanical stirring, and the dispersion time is 5-10 min.

Preferably, when the modulus n is more than or equal to 0.6, the nano SiO2 particles are divided into two parts with similar mass and added in two times, so as to avoid the problem of incapability of stirring caused by one-time addition.

The embodiment of the invention also provides a low-modulus sodium silicate solution which is prepared by the preparation method at normal temperature.

In the embodiment of the invention, the preparation method of the low-modulus sodium silicate solution is simple and quick, is carried out at normal temperature, is ready to use after preparation, and does not need to be stored for a long time to balance.

The invention adopts the function of 'providing the compensating soluble silicon' of the high-activity nano SiO2, so that the obtained low-modulus sodium silicate solution has the characteristics of high activity, low viscosity and good stability.

The low-modulus sodium silicate solution of the invention not only has the characteristic of ultra-low viscosity, but also can be stored for a long time due to the change of the supply state of the soluble silicon, which is obviously beneficial to the industrial production and application of the alkali-activated cementing material.

Preferably, the viscosity of the low-modulus sodium silicate solution is 10-20 mPas.

The embodiment of the invention also provides an alkali-activated cementing material, which takes the low-modulus sodium silicate solution as an alkali activator, takes the low-modulus sodium silicate solution as a clear solution, does not need to be aged after mechanical stirring and ultrasonic dispersion, and can be immediately used for preparing the alkali-activated cementing material

The principle of the invention is as follows: under the condition of normal temperature, the nano SiO2 particles can be dissolved in a strong alkali solution, the NaOH solution is a strong alkali solution, and the nano SiO2 particles can be quickly dissolved in the strong alkali solution. The exotherm rate curve for the addition of 0.03g of nano-sized SiO2 particles to 2.2g of NaOH solution (containing 0.2g of Na2O +2.0g of water) was determined using a microcalorimeter, as shown in FIG. 1. The results show that the solution has a significant long-time exothermic process in the environment of 20 ℃, which indicates that the nano SiO2 particles and the NaOH solution have a certain chemical process. According to its exothermic history, the explanation is as follows: the surface of the hydrophilic nano SiO2 particle is wetted by water to release heat, and the violent heat release lasting for tens of minutes in the first stage is shown; the hydrophilic nano SiO2 particles dissolve in the solution and release heat, releasing soluble silicon and forming [ SiOn (OH)4-n ] n-, which shows a slow heat release lasting for hours in the second stage. The above exothermic behavior confirmed that the nano SiO2 particles were soluble in NaOH solution. The process is long, but the nano SiO2 particles exert their modifying effect whenever a formulated low modulus sodium silicate solution is used. If the nano SiO2 particles are used immediately, the nano SiO2 particles are only partially dissolved in the solution, and the chemical action of providing solubility and the physical filling action and the crystal nucleus action of the superfine particles can be simultaneously exerted; if the nano SiO2 particles are used after long-term aging, the nano SiO2 particles in the solution are completely dissolved, and the chemical effect of providing solubility can be exerted to the maximum extent.

The dissolution characteristics of the nano SiO2 particles in the NaOH solution can be further verified by using a laser particle size analyzer. The dissolution characteristic of the nano SiO2 particles is characterized by the parameter of the opacity of a laser particle sizer. The light-shielding degree refers to the optical concentration of the particles in the solution, and when the particles are finer and more well dispersed, the light-shielding degree of the solution is higher on the premise that the same mass of particles is added. The nano SiO2 particles have small size reaching the nanometer level, and when the nano SiO2 particles are added into a solution in a small amount and are subjected to ultrasonic dispersion, the light shading degree of the solution is close to 20 percent quickly. If the nano SiO2 is always dispersed in the solution in the form of particles, the light shielding degree of the solution is maintained at about 20%. The change curve of the opacity of the solution after adding nano SiO2 particles to the NaOH solution is shown in FIG. 2. The results show that the opacity of the solution drops rapidly within a few tenths of a minute, which means dissolution of the nano SiO2 particles; the shade then slowly diminishes and this trend is maintained to hundreds of minutes, which indicates that the nano SiO2 particles gradually dissolve; after a sufficiently long time (200 minutes) the opacity has decreased from the initial about 20% to about 1%, indicating that again during this time most of the nano-SiO 2 particles have dissolved. The duration of this process is almost identical to the duration of the exotherm of the addition of the nano SiO2 particles to the NaOH solution, which again indicates the solubility of the nano SiO2 particles in the NaOH solution, i.e. the nano SiO2 particles in this solution can indeed act to provide soluble silicon.

The dissolution process of the nano SiO2 particles is necessarily accompanied by the change of the viscosity of the solution. If the nano SiO2 is in a granular state, the solution viscosity is inevitably increased remarkably due to the hydrophilic property; the viscosity must drop significantly if it dissolves and becomes a component of the solution. The change curve of the solution viscosity after adding nano SiO2 particles into NaOH solution is shown in FIG. 3. The results show that the change rule of the viscosity of the solution after adding the nano SiO2 at normal temperature accords with the conjecture, and the solution changes from a turbid state to a clear state, the viscosity is close to that of the initial solution, which again shows the soluble characteristic of the nano SiO2 particles, and the solution viscosity is hardly influenced.

Based on the dissolubility of the nano SiO2 particles in the normal-temperature NaOH solution, the invention designs a scheme for preparing the low-modulus sodium silicate solution by adding the nano SiO2 particles in the NaOH solution. The low-modulus sodium silicate solution can be quickly obtained at normal temperature, and has the characteristics of high activity, low viscosity and high stability.

The present invention will be further described with reference to the following specific examples, which should not be construed as limiting the scope of the invention, but rather as providing those skilled in the art with certain insubstantial modifications and adaptations of the invention based on the teachings of the invention set forth herein.