CN115353317B - High-aluminum-content accelerator and preparation method thereof - Google Patents

Abstract

The invention provides a high-aluminum content accelerator and a preparation method thereof, wherein the high-aluminum content accelerator comprises the following preparation raw materials: according to the weight percentage, 60 to 72 percent of aluminum sulfate, 6 to 12 percent of nano modified alcohol amine, 1 to 2 percent of viscosity reducer, 1 to 1.5 percent of pH regulator, 0.5 to 1 percent of suspending agent, 0.2 to 0.5 percent of dispersant and the balance of water. The high-aluminum content accelerator can keep supersaturated aluminum sulfate in the high-aluminum content accelerator for a long time in a stable state by adding the nano modified alcohol amine, the viscosity reducer, the pH regulator, the antifreezing agent, the suspending agent and the dispersant, and can effectively shorten the setting time of concrete by adding the concrete.

Description

High-aluminum-content accelerator and preparation method thereof

Technical Field

The invention relates to the field of concrete building materials, in particular to a high-aluminum-content accelerator, and also relates to a preparation method of the high-aluminum-content accelerator.

Background

The liquid accelerator is used as an indispensable additive for sprayed concrete, can promote the rapid setting and hardening of the cement concrete, and is widely applied to tunnel construction of engineering projects such as railways, highways and the like. At present, most of liquid accelerators for spraying concrete on the market are alkali or low-alkali liquid accelerators, the alkali content of the liquid accelerators is generally more than 1%, and the liquid accelerators have more or less adverse effects on the mechanical property and durability of the concrete. A few liquid alkali-free accelerators are produced by generally adopting industrial-grade aluminum sulfate as a main raw material and adding some auxiliary materials, and although the alkali content is less than 1%, the alkali-free liquid accelerators have the following problems: 1) The mixing amount is high, and the solubility of the main coagulation promoting component aluminum phase substance is still limited under the condition of heating in the production process. 2) Poor stability, short shelf life, easy hydrolysis of aluminum ions, short storage time, crystallization, delamination or precipitation of the accelerator and the like. 3) Poor freezing resistance, easy crystallization under negative temperature condition, and rapid increase and even solidification of liquid viscosity, which leads to abnormal use in low temperature environment. 4) The sprayed concrete doped with the accelerating agent has high rebound rate and undesirable application effect. 5) The adaptability is poor. The adaptability of the accelerator and cement is poor, the engineering project requirements of using different cements can not be met, and the popularization and the application are not facilitated.

The application of the liquid alkali-free accelerator in heavy projects such as Sichuan and Tibet railways is subject to severe environmental conditions such as severe cold in plateaus and multiple tests of construction environments requiring ultra-fast support such as weak surrounding rocks and overbreak water seepage, and particularly presents great challenges to the stability and frost resistance of the liquid alkali-free accelerator under negative temperature conditions (below 0 ℃).

Disclosure of Invention

The invention provides a high-aluminum-content accelerator which has higher aluminum content, can effectively improve the setting rate of concrete and shorten the setting time of the concrete.

The high-aluminum content accelerator comprises the following preparation raw materials in percentage by weight: aluminum sulfate: 60% -72%, nano modified alcohol amine: 6% -12%, viscosity reducer: 1% -2%, pH regulator: 1% -1.5%, suspending agent: 0.5% -1%, dispersant: 0.2 to 0.5 percent of the total weight of the composition, and the balance of water.

The high-aluminum content accelerator disclosed by the invention can be used for keeping supersaturated aluminum sulfate in a stable state for a long time in the high-aluminum content accelerator by adding the nano modified alcohol amine, the viscosity reducer, the pH regulator, the antifreezing agent, the suspending agent and the dispersing agent.

Furthermore, the raw materials for preparing the nano modified alcohol amine comprise organic alcohol amine and a nano material, wherein the mass ratio of the organic alcohol amine to the nano material is 1 (0.05-0.15).

Further, the nano material comprises at least one of nano silica sol, nano aluminum sol and carbon nano tube dispersion liquid.

Furthermore, the preparation raw material of the accelerator with high aluminum content also comprises 2-3% of a synergist, 1-2% of an excitant and/or 1-1.5% of an antifreeze.

Further, the synergist comprises nano calcium silicate hydrate; the activator comprises at least one of sodium metaaluminate, sodium formate, manganese sulfate and lithium sulfate; the antifreeze comprises at least one of ethylene glycol, urea and diethylene glycol.

Further, the viscosity reducer comprises at least one of dimethylethanolamine, 2-amino-2-methyl-1-propanol and hydrophilic fumed silica.

Further, the pH regulator comprises at least one of lysine, glycine and polyaspartic acid.

Further, the suspending agent includes at least one of ultra-fine sepiolite, lithium magnesium silicate, and pseudo-boehmite.

Further, the dispersant comprises a polyacrylic ammonium salt dispersant.

The invention also provides a preparation method of the accelerating agent with high aluminum content, which comprises the following steps:

adding water, a dispersing agent and a suspending agent into a reaction container, and uniformly stirring to obtain a modified suspension;

and adding aluminum sulfate and nano modified alcohol amine into the modified suspension, uniformly stirring, adding a pH regulator and a viscosity reducer, and uniformly stirring to obtain the accelerator with high aluminum content.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The experimental procedures in the following examples are conventional unless otherwise specified. The test materials used in the following examples were purchased from a conventional biochemical reagent store unless otherwise specified. In addition, unless otherwise specified, all terms and processes related to the present embodiment should be understood according to the conventional knowledge and conventional methods in the art.

A high-aluminum content accelerator comprises the following preparation raw materials: according to the weight percentage, 60 to 72 percent of aluminum sulfate, 6 to 12 percent of nano modified alcohol amine, 1 to 2 percent of viscosity reducer, 1 to 1.5 percent of pH regulator, 0.5 to 1 percent of suspending agent, 0.2 to 0.5 percent of dispersant and the balance of water.

The aluminum sulfate of the accelerator with high aluminum content dissociates in water, SO42- (sulfate ion) generated by hydrolysis reacts with Ca2+ (calcium ion) generated by hydration of cement to generate fine secondary gypsum, the activity of the gypsum is higher than that of the original gypsum in the cement, the reaction process with C3A (tricalcium aluminate) in the cement is accelerated, needle-shaped ettringite crystals are easier to generate, the aluminum sulfate can directly and rapidly react with Ca (OH) 2 in a liquid phase to generate ettringite, the ettringite expands in volume and is mutually staggered to form a compact net-shaped structure, pores are filled, slurry is compact, strength development is facilitated, and cement concrete is rapidly coagulated; on the other hand, since the concentration of Ca2+ in the liquid phase is reduced, dissolution of C3A is promoted; al3+ (aluminum ions) can also accelerate the generation of C-S-H gel, shorten the induction period of C3S, accelerate the further hydration of C3S and enable the cement to be rapidly set. The aluminum sulfate of the invention can be preferably industrial grade powdery aluminum sulfate octadecahydrate or polyaluminum sulfate with the alumina content of more than or equal to 16.0 percent.

The nano modified alcohol amine adopts nano materials to modify the organic alcohol amine, can effectively improve the complexing capacity of the organic alcohol amine to aluminum ions, greatly promotes more aluminum sulfate to be fully dissolved compared with common organic alcohol amine substances, and can complete the dissolution of aluminum sulfate raw materials without additional heating, so that the accelerator disclosed by the invention has higher aluminum content, and can meet the accelerating requirement under the condition of lower mixing amount (4% -6% of the content of a gelled material). Meanwhile, a small amount of nano materials are introduced, and the filling effect and the crystal nucleus induction effect of the nano materials have certain effect of improving the strength of the concrete.

The mass ratio of the organic alcohol amine to the nano material is 1 (0.05-0.15), the organic alcohol amine can be preferably monoethanolamine and diethanolamine, and the triethanolamine is prepared from the following raw materials in the mass ratio of (10-20): (70-80): (5-10). The N atom of the organic alcohol amine has lone pair electrons, can participate in complexing metal ions, can generate water-soluble complexing ions with Al < 3+ > (aluminum ions) and the like, and improves the solubility of the aluminum sulfate of the accelerator with high aluminum content. Meanwhile, after the accelerator with high aluminum content is mixed with concrete, organic alcohol amine can generate complex ions which are easy to dissolve in water with Ca & lt 2+ & gt (calcium ions), fe & lt 3+ & gt (iron ions) and the like, the solubility of the surface of cement particles is improved, an impermeable layer at the initial stage of hydration is prevented from being formed on the surface of C3A (tricalcium aluminate), the dissolution of C3A and C4AF (tetracalcium aluminoferrite) is promoted, and the reaction of the accelerator and gypsum is accelerated to generate calcium sulphoaluminate. Meanwhile, the reaction also reduces the concentration of calcium ions and aluminum ions in the liquid phase, and further promotes the hydration of C3S (tricalcium silicate), thereby promoting the early strength of the concrete to be increased.

The nano material has larger specific surface area and high surface energy unstable atoms, is easy to adsorb and bond with organic alcohol amine, provides active atoms with large surface due to smaller particle size and belongs to nano level, can improve the activity of the organic alcohol amine, enables the organic alcohol amine to have stronger complexing ability and stronger coagulation promoting ability of concrete, and can form dissolving adsorption on Al < 3+ > due to the adsorption effect of the nano material, so that the solubility of the Al < 3+ > of the accelerator with high aluminum content is improved. The nano material preferably comprises at least one of nano silica sol, nano aluminum sol and carbon nano tube dispersion liquid, wherein the nano silica sol can adopt Levasil CB45A sold on the market, the nano aluminum sol can adopt VL-L10A sold on the market, and the carbon nano tube dispersion liquid can adopt XFNAO sold on the market. Organic alcohol amine and a nano material are mixed according to the mass ratio of 1 (0.05-0.15), and then are subjected to ultrasonic dispersion for a certain time, so that uniform and stable nano modified alcohol amine can be prepared.

The preparation raw material of the high-aluminum content accelerator also preferably comprises 2-3% of synergist and/or 1-2% of excitant and/or 1-1.5% of antifreeze. The synergist can reduce the nucleation barrier of cement hydration, provide nucleation growing points of cement hydration products, accelerate the cement hydration process, and compared with the traditional synergist or an early strength agent, the synergist can effectively improve the compressive strength of mortar and concrete doped with the accelerator within 6-24H in the very early stage, has high later strength guarantee rate, preferably adopts nano C-S-H hydrated calcium silicate with the grain size of 50-100nm, and has better crystal nucleus effect. The synergist can be purchased from GK-3Z nano microcrystalline material and nano C-S-H hydrated calcium silicate suspension sold in Shanghai Yangtze building materials Co.

The activator component can adopt inorganic salts (the dosage is controlled so that the alkali content introduced into the accelerator is less than or equal to 1.0 percent), and on the basis of not influencing the accelerating effect of the accelerator, the activator can activate the hydration rate of cement minerals and obviously improve the early strength of mortar or concrete doped with the accelerator with high aluminum content. The activator preferably comprises at least one of sodium metaaluminate, sodium formate, manganese sulfate and lithium sulfate.

The antifreezing agent can harden the concrete at negative temperature and reach the expected performance and sufficient antifreezing strength under the specified curing condition. Prevent the water in the concrete from freezing at low temperature, ensure the normal construction of the concrete at negative temperature and reduce the freezing point in the concrete mixture. The antifreezing agent can be water-soluble organic compounds or composite antifreezing agents. The antifreezing agent is added into the high-aluminum content accelerator, so that the antifreezing property and low-temperature stability of the accelerator can be further improved; the antifreeze comprises at least one of ethylene glycol, urea and diethylene glycol.

The viscosity reducer can reduce the viscosity of the accelerator with high aluminum content, and if the viscosity is too high, the viscosity reducer is easy to block a pipeline of construction equipment during use, can reduce the unfavorable phenomena of easy solidification and crystallization at negative temperature, and greatly improves the negative temperature stability and frost resistance of the accelerator. The viscosity reducer preferably comprises at least one of dimethylethanolamine, 2-amino-2-methyl-1-propanol and hydrophilic fumed silica.

The pH regulator is acidic substance, and can be organic acid or inorganic acid, and can increase hydrogen ion amount of accelerator mixture, inhibit hydrolysis of aluminum ion in accelerator, and effectively prevent formation of aluminum hydroxide precipitate, and preferably contains at least one of lysine, glycine, and polyaspartic acid.

The suspending agent component and the dispersant component act together to form a well-dispersed modified suspension, and the suspending agent is silicate mineral and presents a three-dimensional network structure after absorbing water, so that the suspending aluminum can be adsorbed. However, the suspending agent is easy to settle and separate, and the dispersing agent is added to disperse the suspending agent, so that the suspending agent can be stably suspended in the high-aluminum content accelerating agent. Compared with the common unmodified suspending agent, the suspending efficiency of supersaturated aluminum phase substances in the accelerating agent is greatly improved, and under the synergistic action of the pH regulator, the aluminum phase substances in a partial suspending state are prevented from crystallizing in a normal-temperature storage mode or at a low temperature, so that the stability and the freezing resistance are greatly improved. The suspending agent comprises at least one of ultra-fine sepiolite, lithium magnesium silicate and pseudo-boehmite, the ultra-fine sepiolite preferably having an average particle size of less than 5um. The dispersant includes a polyacrylic ammonium salt dispersant, such as a dow OROTAN1618 type dispersant.

The accelerator with high aluminum content is liquid, has high aluminum content, alkali content of less than or equal to 1.0 percent, chloride ion content of less than or equal to 0.05 percent and fluoride ion content of less than or equal to 0.05 percent, is low in doping amount in concrete, ensures that the early strength of the concrete is high, the 6h compressive strength of more than or equal to 3.0MPa, the 1d compressive strength of more than or equal to 18MPa, the later strength is not lost, the retention rate of the 90d compressive strength of more than or equal to 105 percent, has good stability and frost resistance, the shelf life of more than 9 months at normal temperature, has the shelf life of more than 6 months at the temperature of 18 ℃ below zero, has good adaptability to cement, low rebound rate of sprayed concrete and rebound rate of less than 5 percent, and all indexes meet the requirements of GB/T35159-2017 accelerator for sprayed concrete and Q/CR807-2020 liquid alkali-free accelerator for tunnel sprayed concrete.

The invention also provides a preparation method of the accelerating agent with high aluminum content, which comprises the following steps:

preparing nano modified alcohol amine: mixing organic alcohol amine with the nano material, and performing ultrasonic dispersion for 0.5-1h to obtain the nano modified alcohol amine.

Preparation of modified suspension: adding water, a dispersing agent and a suspending agent into a reaction container, and stirring at a high speed of 2000-3000rpm for 30-60 min by adopting a high-speed shearing dispersion machine to obtain a modified suspension.

Preparing a high-aluminum-content accelerator: adding exciting agent into the modified suspension, stirring for 10-20min, adding 1/2 of the total amount of aluminum sulfate and nano modified alcohol amine, stirring for 30-60 min at the stirring speed of 400-500rpm, adding the rest 1/2 of aluminum sulfate, and stirring uniformly. Adding a pH regulator and a viscosity reducer, and uniformly stirring to obtain the accelerator with high aluminum content.

In order to enable the high-aluminum-content accelerator prepared by the invention to have the advantages of improving the early strength and frost resistance of concrete, an exciting agent can be added before aluminum sulfate is added into modified suspension, a synergist can be added dropwise at a constant speed after the aluminum sulfate is added, the dropwise adding time can be flexibly controlled, for example, 1-3h, and the high-speed stirring is carried out while dropwise adding, wherein the stirring speed is 1000-2000rpm. After the synergist is added, the antifreezing agent is added.

The high-aluminum content accelerator prepared by the method is liquid, and the temperature is normal temperature and heating is not needed in the whole preparation process. The alkaline synergist can be dropwise added at a constant speed under a high-speed stirring state, so that the problem of poor stability of the accelerator caused by directly adding the alkaline synergist into the acidic accelerator at one time can be solved.

The following describes in detail specific embodiments of the present invention.

Example 1

The raw materials for preparing the high-aluminum content accelerator of the embodiment comprise 60% of aluminum sulfate, 6% of nano modified alcohol amine, 2% of synergist, 1% of excitant, 2% of viscosity reducer, 1% of pH regulator, 1% of antifreeze, 1% of suspending agent, 0.2% of dispersant and the balance of water.

The aluminum sulfate of the embodiment is industrial grade powdery aluminum sulfate octadecahydrate with 16.2 percent of alumina content; the nanometer modified alcohol amine is prepared by mixing components A and B according to the mass ratio of 1:0.05 and then performing ultrasonic dispersion for 0.5h, wherein the component A is mixed organic alcohol amine consisting of monoethanolamine, diethanolamine and triethanolamine, the mass ratio of the components A is respectively 10wt%, 80wt% and 10wt%, and the component B is nanometer silica sol; the synergist is GK-3Z nano microcrystalline material of the Minghuanyuanyuanzai building materials Co., ltd, which is nano C-S-H hydrated calcium silicate suspension with the average particle size of 50 nm; the excitant is sodium metaaluminate; the viscosity reducer of the embodiment is dimethylethanolamine; the pH regulator is lysine; the antifreezing agent is ethylene glycol; the suspending agent is ultra-fine sepiolite; the dispersant is a Touretan 1618 type dispersant.

The preparation method of the accelerator with high aluminum content comprises the following steps:

preparing nano modified alcohol amine: mixing organic alcohol amine mixed with the component A and a nanometer material of the component B according to the mass ratio of 1:0.05, and performing ultrasonic dispersion for 0.5h to obtain the nano modified alcohol amine.

Preparation of modified suspension: weighing raw materials according to the proportion, sequentially adding water, a dispersing agent and a suspending agent into a reaction vessel, and stirring at a high speed of 2000rpm for 30min by a high-speed shearing disperser to obtain a well-dispersed modified suspension.

Preparing a high-aluminum-content accelerator: adding exciting agent into the obtained modified suspension, and stirring for 10min; then sequentially adding 1/2 of aluminum sulfate and the prepared nano modified alcohol amine, and stirring for 30min at the stirring speed of 400rpm; adding the rest 1/2 of aluminum sulfate, then immediately dropwise adding the synergist into the reaction container at a constant speed, stirring at a high speed while dropwise adding, wherein the dropwise adding and stirring time is 60min, and the stirring speed is 1000rpm. After the dropping of the synergist is finished, the stirring speed is reduced to 400rpm, the pH regulator is added, and the stirring is carried out for 20min. And continuously adding the antifreezing agent and the viscosity reducer, and stirring for 20min. The accelerator with high aluminum content can be obtained.

The temperature of the whole preparation process is normal temperature, and heating is not needed.

Example 2

The high-aluminum content accelerator of the embodiment is prepared from the raw materials of 63% of aluminum sulfate, 8% of nano-modified alcohol amine, 3% of synergist, 2% of excitant, 1% of viscosity reducer, 1% of pH regulator, 1.5% of antifreezing agent, 1% of suspending agent, 0.3% of dispersing agent and the balance of water.

The aluminum sulfate of the embodiment is industrial grade powdery polyaluminum sulfate with 16.5% of alumina content; the nanometer modified alcohol amine is prepared by mixing the components A and B according to the mass ratio of 1. The component A is a mixed organic alcohol amine consisting of monoethanolamine, diethanolamine and triethanolamine, the mass ratio of which is respectively 20wt%, 75 wt% and 5wt%, and the component B is nano-alumina sol; the synergist is GK-3Z nano microcrystalline material of Changchun Youcai building materials Co.Ltd in Shijiazhuang, which is nano C-S-H hydrated calcium silicate suspension with the average grain diameter of 70 nm; the excitant is manganese sulfate; the viscosity reducer of the embodiment is dimethylethanolamine; the pH regulator is glycine; the antifreeze is urea; the suspending agent is magnesium lithium silicate; the dispersant is a Dow OROTAN1618 type dispersant.

The preparation method of the accelerator with high aluminum content comprises the following steps:

preparing nano modified alcohol amine: mixing organic alcohol amine mixed with the component A and a nanometer material of the component B according to the mass ratio of 1:0.1 mixing, and ultrasonic dispersing for 0.5h to obtain the nano modified alcohol amine for later use.

Preparation of modified suspension: weighing raw materials according to the proportion, sequentially adding water, a dispersing agent and a suspending agent into a reaction vessel, and stirring for 45min at a high speed of 2500rpm through a high-speed shearing disperser to obtain a well-dispersed modified suspension.

Preparing a high-aluminum-content accelerator: adding exciting agent into the obtained modified suspension, and stirring for 10min; then sequentially adding 1/2 of aluminum sulfate and the prepared nano modified alcohol amine, and stirring for 30min at the stirring speed of 450rpm; adding the rest 1/2 of aluminum sulfate, then immediately dripping the synergist into the reaction container at a constant speed, stirring at a high speed while dripping, wherein the dripping and stirring time is 60min, and the stirring speed is 1200rpm. After the dropping of the synergist is finished, the stirring speed is reduced to 450rpm, the synergist and the pH regulator are added, and the stirring is carried out for 20min. Adding the antifreeze and the viscosity reducer, and stirring for 20min. The accelerator with high aluminum content can be obtained.

The temperature of the whole preparation process is normal temperature, and heating is not needed.

Example 3

The raw materials for preparing the high-aluminum-content accelerator comprise 65% of aluminum sulfate, 9% of nano-modified alcohol amine, 2% of synergist, 2% of excitant, 1.5% of viscosity reducer, 1.2% of pH regulator, 1.2% of antifreezing agent, 0.5% of suspending agent, 0.4% of dispersing agent and the balance of water.

The aluminum sulfate of the embodiment is industrial grade powdery aluminum sulfate octadecahydrate with 16.5 percent of alumina content; the nano modified alcohol amine is prepared by mixing components A and B according to the mass ratio of 1:0.1 and then performing ultrasonic dispersion for 1h, wherein the component A is mixed organic alcohol amine consisting of monoethanolamine, diethanolamine and triethanolamine, the mass ratio of the components A is respectively 15wt%, 75 wt% and 10wt%, and the component B is carbon nano tube dispersion liquid; the synergist is GK-3Z nano microcrystalline material of Changchun Youcai building materials Co.Ltd in Shijiazhuang, which is nano C-S-H hydrated calcium silicate suspension with the average grain diameter of 50 nm; the excitant is lithium sulfate; the viscosity reducing agent of this example was AMP95 (2-amino-2-methyl-1-propanol); the pH regulator is polyaspartic acid; the antifreezing agent is ethylene glycol; the suspending agent is pseudo-boehmite; the dispersant is a Touretan 1618 type dispersant.

The preparation method of the accelerator with high aluminum content comprises the following steps:

preparing nano modified alcohol amine: mixing component A with organic alcohol amine and component B nano material according to the mass ratio of 1:0.1, and performing ultrasonic dispersion for 1 hour to obtain the nano modified alcohol amine for later use.

Preparation of modified suspension: weighing raw materials according to the proportion, sequentially adding water, a dispersing agent and a suspending agent into a reaction vessel, and stirring for 45min at a high speed of 2500rpm through a high-speed shearing disperser to obtain a well-dispersed modified suspension.

Preparing a high-aluminum-content accelerator: adding exciting agent into the obtained modified suspension, and stirring for 15min; then sequentially adding 1/2 of aluminum sulfate and the prepared nano modified alcohol amine, and stirring for 60min at the stirring speed of 500rpm; adding the rest 1/2 of aluminum sulfate, then immediately dripping the synergist into the reaction container at a constant speed, stirring at a high speed while dripping, wherein the dripping and stirring time is 75min, and the stirring speed is 1500rpm. After the dropping of the synergist is finished, the stirring speed is reduced to 500rpm, the synergist and the pH regulator are added, and the mixture is stirred for 30min. Adding the antifreeze and the viscosity reducer, and stirring for 30min. The accelerator with high aluminum content can be obtained.

The temperature of the whole preparation process is normal temperature, and heating is not needed.

Example 4

The high-aluminum content accelerator of the embodiment is prepared from raw materials comprising 68% of aluminum sulfate, 11% of nano-modified alcohol amine, 3% of synergist, 1% of activator, 2% of viscosity reducer, 1% of pH regulator, 1% of antifreeze, 0.5% of suspending agent, 0.5% of dispersant and the balance of water.

The aluminum sulfate in the embodiment is industrial grade powdery polyaluminum sulfate with the aluminum oxide content of 17.0%; the nano modified alcohol amine is prepared by mixing components A and B according to the mass ratio of 1:0.15 and then performing ultrasonic dispersion for 1h, wherein the component A is mixed organic alcohol amine consisting of monoethanolamine, diethanolamine and triethanolamine, the mass ratio of the components A is respectively 13wt%, 80wt% and 7wt%, and the component B is nano silica sol; the synergist is GK-3Z nano microcrystalline material of Changchun Youcai building materials Co.Ltd in Shijiazhuang, which is nano C-S-H hydrated calcium silicate suspension with the average grain diameter of 50 nm; the exciting agent is sodium formate; the viscosity reducer of the embodiment is hydrophilic fumed silica; the pH regulator is lysine; the antifreezing agent is diethylene glycol; the suspending agent is lithium magnesium silicate; the dispersant is a Touretan 1618 type dispersant.

The preparation method of the accelerator with high aluminum content comprises the following steps:

preparing nano modified alcohol amine: mixing organic alcohol amine mixed with the component A and a nanometer material of the component B according to the mass ratio of 1:0.15, and ultrasonic dispersion for 1h to obtain the nano modified alcohol amine for later use.

Preparation of modified suspension: weighing raw materials according to a mixture ratio, sequentially adding water, a dispersing agent and a suspending agent into a reaction container, and stirring at a high speed of 3000rpm for 60min by a high-speed shearing disperser to obtain a well-dispersed modified suspension.

Preparing a high-aluminum-content accelerator: adding exciting agent into the obtained modified suspension, and stirring for 10-20min; then sequentially adding 1/2 of aluminum sulfate and the prepared nano modified alcohol amine, and stirring for 60min at the stirring speed of 500rpm; adding the rest 1/2 of aluminum sulfate, then immediately dripping the synergist into the reaction container at a constant speed, stirring at a high speed while dripping, wherein the dripping and stirring time is 90min, and the stirring speed is 2000rpm. After the dropping of the synergist is finished, the stirring speed is reduced to 500rpm, the synergist and the pH regulator are sequentially added, and the stirring is carried out for 30min. Sequentially adding the antifreezing agent and the viscosity reducer, and stirring for 30min. The accelerator with high aluminum content can be obtained.

The temperature of the whole preparation process is normal temperature, and heating is not needed.

The following are experimental test sections of the invention

The recommended mixing amount of the accelerator with high aluminum content in the sprayed concrete is 4-8% of the total amount of the cementing material. The general requirements of Q/CR807-2020 on alkali-free setting accelerators are: the alkali content is less than or equal to 1.0 percent, the chloride ion content is less than or equal to 0.05 percent, and the fluorine ion content is less than or equal to 0.05 percent; the performance requirements of the clean slurry and the mortar doped with the liquid alkali-free accelerator (the doping amount is 6-8%) are shown in the table 1. Because the performance index requirement of GB/T35159-2017 accelerator for sprayed concrete is lower than the Q/CR807-2020 standard, if the requirement of the Q/CR807-2020 standard is met, the requirement of the GB/T35159-2017 standard is definitely met.

TABLE 1 Accelerator admixtures neat and mortar Performance requirements (Standard Q/CR 807-2020)

Test item one

The high aluminum content setting accelerators prepared in examples 1 to 4 were subjected to index tests such as setting time and compressive strength according to the test method specified in Q/CR807-2020 alkali-free liquid setting accelerator for tunnel shotcrete. The test cement was the reference cement p.i42.5.

The test example of the non-accelerating agent is used as a blank group, the alkali-free accelerating agent prepared in example 1 of patent document CN113213805A is used as comparative example 1, the alkali-free accelerating agent prepared in example 5 of patent document CN111892327A is used as comparative example 2, the alkali-free accelerating agent prepared in example 4 of patent document CN113603384A is used as comparative example 3, and the test results are shown in Table 2.

TABLE 2 Accelerator Properties (reference Cement)

As can be seen from the data in Table 2, the accelerator with high aluminum content has excellent performance, the viscosity is lower than 150mPa.s, the phenomenon that construction equipment is easily blocked due to overlarge viscosity (particularly at low temperature) is avoided, and the construction is more convenient; the use amount is 5-6 percent, which is lower than the required amount (6-8 percent) of standard Q/CR807-2020 and the required amount (6-9 percent) of GB/T35159-2017, and is more beneficial to saving the project cost.

In the embodiment, the performance indexes meet the requirements of two standards of Q/CR807-2020 and GB/T35159-2017 by adopting standard cement detection under the condition of 5% -6% of doping amount. The compressive strength in 6 hours is more than 3.0MPa, even up to 4.3MPa, the compressive strength in 1 day is more than 15.0MPa, the compressive strength in 6 percent is more than 18MPa, the compressive strength in 6 hours to 24 hours is high in the ultra-early stage, the construction safety and the construction progress are ensured, and the method is particularly suitable for engineering projects which have complicated geological conditions such as weak surrounding rocks and need quick support. The later strength is not reduced or even improved, the 28-day compressive strength ratio is more than 100 percent, the 90-day compressive strength retention rate is more than 105 percent, and the engineering quality is fully guaranteed.

The liquid accelerators of comparative examples 1-3 have higher viscosity than the examples of the present invention, and the risk of clogging of construction equipment is relatively high due to the increase in viscosity as the ambient temperature is lowered, particularly comparative example 3. According to the performance requirements of Q/CR807-2020 liquid alkali-free setting accelerator for tunnel sprayed concrete in Table 1, the liquid alkali-free setting accelerator in comparative example 1 has unqualified final setting time, 6h compressive strength and 90d compressive strength retention rate when the amount of the liquid alkali-free setting accelerator is 5 percent, and has unqualified mortar 90d retention rate when the amount of the liquid alkali-free setting accelerator is 6 percent; in the comparative example 2, the compressive strength is unqualified in 6h under the condition of 5 percent of doping amount, and the compressive strength in 6h is only 1.5MPa although the setting time is faster under the condition of 6 percent of doping amount, which is far lower than the compressive strength in 6h of the embodiment of the invention under the same doping amount, and the retention rate of the compressive strength in 90d is also lower than that of the embodiment of the invention; the liquid accelerator of the comparative example 3 has unqualified retention rates of 5 percent of addition amount, final setting time and 90d compressive strength, has slower setting time than that of the embodiment of the invention under 6 percent of addition amount, and has the compressive strength of less than 3.0MPa after 6h, compared with the high-aluminum-content accelerator of the invention, the comprehensive performance is better.

Test item two

Extracting 4 kinds of cement: whelk cement p.o42.5, starship city cement p.o42.5, southwest cement p.o42.5 and rhinestone cement p.o42.5, the compatibility test of the high aluminum content accelerator of example 4 with cement was tested, and the test results are shown in table 3.

TABLE 3 high aluminum content accelerator Performance (engineering cement)

As can be seen from the data in Table 3, the high-aluminum content accelerator disclosed by the invention adopts cement for various engineering projects, and all performance indexes of the cement meet the performance requirements of Q/CR807-2020 on a liquid alkali-free accelerator in Table 1, so that the high-aluminum content accelerator disclosed by the invention has good adaptability with various cements and can meet the use requirements of various engineering projects.

Test item three

According to the test method of the stability of the quick-setting agent in the Q/CR807-2020 standard, the quick-setting agent with high aluminum content of each example is placed at different temperatures and stored for a certain time, if the volume of the supernatant (or the bottom sediment) in 100mL of the liquid quick-setting agent is less than or equal to 5mL, the stability is qualified in the storage period, otherwise, the stability is unqualified. Also, the viscosity of the quick-setting admixture was measured up to 3 months of storage, and the results are shown in Table 4, "√ denotes a satisfactory stability, and" × "denotes a unsatisfactory stability. The accelerator of comparative example 2 in table 4 was the same as the accelerator of comparative example 2 in test item one.

TABLE 4 stability and viscosity of the setting accelerators

As can be seen from Table 4, the high-aluminum-content accelerator disclosed by the invention is good in stability and frost resistance, the shelf life (storage life) at the normal temperature of 20 ℃ can be more than 9 months, the storage life at the negative temperature of-18 ℃ can be more than 6 months (even 9 months), the high-aluminum-content accelerator disclosed by the invention can be stored for 3 months, the liquid viscosity at the negative temperature of 18 ℃ is still lower (less than 500mPa.s), the shelf life is long, and the accelerator is very suitable for construction projects in severe cold areas in plateaus such as Sichuan railway and the like. The normal-temperature shelf life of the comparative example 2 is 6 months, the negative-temperature shelf life is 3 months, the viscosity of the product stored at the negative temperature for 3 months is obviously increased and exceeds 1200mPa.S, and the risk of blockage of the construction equipment hose is huge.

Test item four

The rebound resilience of shotcrete incorporating the high aluminum content accelerator of the invention was tested according to the method mentioned in appendix G of JGJ/T372-2016 shotcrete application Specification, and the test results are shown in Table 5. The cement used in the rebound resilience test is Heqing P.O42.5 cement, and the water reducing agent is a GK-3000 polycarboxylic acid high-performance water reducing agent produced by Shijiazhuang Yongyuancai building materials Co.

TABLE 5 shotcrete rebound incorporating high aluminum content accelerators

As can be seen from Table 5, under the same sprayed concrete mixing proportion, the rebound rate of the sprayed concrete is lower (less than 5%) by adopting the high-aluminum-content accelerator provided by the invention under the mixing amount of 5-6%, and the application effect is good.

In conclusion, the high-aluminum-content accelerator disclosed by the invention is good in comprehensive performance, can meet the performance index requirements of standard Q/CR807-2020 alkali-free liquid accelerator for tunnel shotcrete and GB/T35159-2017 accelerator for shotcrete under the condition of low doping amount of 5% -6%, the compressive strength of mortar at 6h is more than or equal to 3.0MPa, the compressive strength at 1d is more than 15MPa, and the retention rate of compressive strength at 90d is more than 105%, and has the characteristics of high compressive strength of mortar at the ultra-early age of 6h-24h, high retention rate of later strength, good stability and freezing resistance, namely the storage period at minus 18 ℃ can reach more than 6 months), good adaptability to cement, and low rebound rate of shotcrete doped with the high-aluminum-content accelerator, and the preparation process of the accelerator disclosed by the invention does not need heating, is simple in preparation process, free of fluorine, free of alkali and chlorine, green and very suitable for popularization and application, and is particularly suitable for engineering projects requiring quick support, such as plateau severe cold and weak surrounding rock tunnels.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that, in the above embodiments, the various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present invention does not separately describe various possible combinations.

Claims (9)

1. A high-aluminum content accelerator is characterized in that: the high-aluminum content accelerator comprises the following preparation raw materials in percentage by weight: aluminum sulfate: 60% -72%, nano modified alcohol amine: 6% -12%, viscosity reducer: 1% -2%, pH regulator: 1% -1.5%, suspending agent: 0.5% -1%, dispersant: 0.2 to 0.5 percent of the total weight of the composition, and the balance of water; the nano modified alcohol amine is prepared by mixing organic alcohol amine and a nano material and then performing ultrasonic dispersion; the nano material comprises at least one of nano silica sol, nano aluminum sol and carbon nano tube dispersion liquid.

2. The high aluminum content accelerator according to claim 1, characterized in that: the raw materials for preparing the nano modified alcohol amine comprise organic alcohol amine and a nano material, wherein the mass ratio of the organic alcohol amine to the nano material is 1 (0.05-0.15).

3. The accelerator with high aluminum content according to claim 1, characterized in that: the preparation raw material of the accelerator with high aluminum content also comprises 2-3% of a synergist, 1-2% of an excitant and/or 1-1.5% of an antifreezing agent.

4. The high aluminum content accelerator according to claim 3, characterized in that: the synergist comprises nano calcium silicate hydrate; the activator comprises at least one of sodium metaaluminate, sodium formate, manganese sulfate and lithium sulfate; the antifreeze comprises at least one of ethylene glycol, urea and diethylene glycol.

5. The high aluminum content accelerator according to claim 1, characterized in that: the viscosity reducer comprises at least one of dimethylethanolamine, 2-amino-2-methyl-1-propanol and hydrophilic fumed silica.

6. The high aluminum content accelerator according to claim 1, characterized in that: the pH regulator comprises at least one of lysine, glycine and polyaspartic acid.

7. The high aluminum content accelerator according to claim 1, characterized in that: the suspending agent comprises at least one of ultra-fine sepiolite, lithium magnesium silicate and pseudo-boehmite.

8. The high aluminum content accelerator according to any one of claims 1 to 7, characterized in that: the dispersant comprises a polyacrylic ammonium salt dispersant.

9. A method for producing the accelerator with a high aluminum content according to claim 1, characterized in that: the method comprises the following steps:

adding water, a dispersing agent and a suspending agent into a reaction container, and uniformly stirring to obtain a modified suspension;

and adding aluminum sulfate and nano modified alcohol amine into the modified suspension, uniformly stirring, adding a pH regulator and a viscosity reducer, and uniformly stirring to obtain the accelerator with high aluminum content.