Fluorine-free and alkali-free liquid accelerator, preparation method and application thereof

Abstract

The application provides a fluorine-free and alkali-free liquid accelerator and a preparation method and application thereof. The fluorine-free and alkali-free liquid accelerator comprises the following components in parts by weight: 40-45 parts of aluminum sulfate, 1-5 parts of amorphous aluminum hydroxide, 1-3 parts of nano iron hydroxide, 5-9 parts of alcohol amine, 0.1-0.4 parts of a stabilizer and 40-45 parts of deionized water. The nano iron hydroxide is used in the application, which serves as an alkaline agent to further promote the polymerization of aluminum sulfate and increase the stability of the system, and on the other hand, introduces high-activity iron ions to promote the generation of iron-containing ettringite and provide a crystal nucleus site for the hydration products such as ettringite, thereby reducing the setting time and promoting the early strength. After the accelerator is mixed with cement, the 1d compressive strength is greater than 16.0 MPa, the 28d compressive strength ratio is greater than 110%, and the 90d compressive strength retention rate is greater than 100%.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a fluorine-free and alkali-free liquid quick-setting agent, its preparation method, and its application. Background Technology

[0002] Shotcrete is widely used for the initial support of underground engineering projects such as tunnels and underground mines. Concrete accelerators, as the core material of shotcrete, enable the concrete to set and harden rapidly to meet engineering requirements. Concrete accelerators are divided into alkali-based and alkali-free accelerators. Traditional alkali-based accelerators were widely used in the past, but due to the reduction in later-stage concrete strength caused by high dosage and the alkali-aggregate reaction caused by high alkalinity, they are gradually being replaced by low-alkali or alkali-free accelerators.

[0003] Commercially available alkali-free quick-setting agents are mainly aluminum sulfate-based. Because aluminum sulfate has low solubility, complexing agents are needed to increase the aluminum source in the solution. Commonly used complexing agents are hydrofluoric acid and sodium fluoride. However, hydrofluoric acid is seriously harmful to health, posing risks not only during synthesis and preparation but also during construction. Furthermore, uncomplexed fluoride ions can complex with both aluminum and calcium ions in cement, hindering cement hydration and reducing the early strength of concrete. High amounts of aluminum sulfate can lead to excessive sulfate ions, causing not only the hydrolysis of aluminum ions but also sulfate corrosion, resulting in reduced later-stage concrete strength.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] This invention addresses the problems of existing alkali-free accelerators, such as low aluminum source concentration, aluminum ion supersaturation, poor stability, low early and late strength, and safety concerns related to fluorine content. The aim of this invention is to provide a safe, efficient, stable, and mechanically superior fluorine-free alkali-free liquid accelerator, along with its preparation method and applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a fluorine-free and alkali-free liquid quick-setting agent, comprising the following components in parts by weight: 40-45 parts aluminum sulfate, 1-5 parts amorphous aluminum hydroxide, 1-3 parts nano-ferric hydroxide, 5-9 parts alkanolamine, 0.1-0.4 parts stabilizer, and 40-45 parts deionized water.

[0008] Preferably, the alkanolamine is diethanolamine or / and triethanolamine;

[0009] Preferably, when the alkanolamine is diethanolamine and triethanolamine, the mixing mass ratio of diethanolamine to triethanolamine is 2:3;

[0010] Preferably, the stabilizer is polyacrylamide with a molecular weight of 500w to 800w.

[0011] Preferably, the amorphous aluminum hydroxide has an average particle size of 50–70 nm; the nano-iron hydroxide has an average particle size of 10–30 nm.

[0012] This invention provides a method for preparing a fluorine-free and alkali-free liquid quick-setting agent, comprising the following steps:

[0013] (1) Preparation of amorphous aluminum hydroxide;

[0014] (2) Preparation of nano-ferric hydroxide;

[0015] (3) Weigh each raw material component according to the mass fraction and set aside;

[0016] (4) Take 1 to 3 parts by mass of alcohol amine, mix the stabilizer, alcohol amine and deionized water, and stir at 60 to 80°C for 1 to 2 hours to obtain a suspension;

[0017] (5) Add aluminum sulfate and amorphous aluminum hydroxide to the suspension and stir at 60-70°C for 1-2 hours to obtain the quick-setting component;

[0018] (6) Add the remaining mass fraction of alkanolamine and nano-ferric hydroxide to the quick-setting component and stir at 60-70°C for 1-2 hours to obtain the final product.

[0019] The preferred method for preparing amorphous aluminum hydroxide is as follows: neutralize aluminum sulfate solution with ammonia water, adjust the pH of the solution to 6-6.5 to generate amorphous aluminum hydroxide, centrifuge, wash, dry, and grind to obtain the product;

[0020] Preferably, the aluminum sulfate solution has a mass concentration of 50 g / L, and the ammonia solution has a volume concentration of 25%.

[0021] Preferably, the stirring speed in step (4) is 600 r / min; the stirring speed in step (5) is 1200 r / min; and the stirring speed in step (6) is 1000 r / min.

[0022] Preferably, the preparation method of nano-ferric hydroxide is as follows: neutralize the ferric sulfate solution containing magnesium silicate with ammonia water, adjust the pH of the solution to 6-6.5 to generate nano-ferric hydroxide, centrifuge and wash to obtain the nano-ferric hydroxide.

[0023] Preferably, the ferric sulfate solution has a ferric sulfate concentration of 25 g / L and a magnesium silicate content of 1-2% by mass; the ammonia solution has a volume concentration of 25%.

[0024] This invention provides an application of a fluorine-free and alkali-free liquid quick-setting agent in shotcrete.

[0025] Preferably, the dosage of the fluorine-free and alkali-free liquid accelerator is 6-9% of the cement mass.

[0026] Beneficial effects:

[0027] (1) This invention uses aluminum sulfate and amorphous aluminum hydroxide as the main aluminum phase components. It utilizes highly active aluminum hydroxide and aluminum sulfate to perform hydrolysis and polymerization to achieve the formation of polymerized aluminum sulfate, thereby increasing the concentration of highly active aluminum ions in the alkali-free system.

[0028] (2) The present invention uses nano-ferric hydroxide, which can be used as an alkaline agent to further promote the polymerization of aluminum sulfate and increase the stability of the system. On the other hand, the introduction of highly active iron ions can promote the formation of iron-containing ettringite and provide crystal nucleation sites for hydrated products such as ettringite, thereby reducing the solidification time and promoting early strength.

[0029] (3) The fluorine-free and alkali-free liquid quick-setting agent of the present invention was mixed with cement, and the performance of the fluorine-free and alkali-free liquid quick-setting agent of the present invention was determined according to GB / T 35159-2017 "Quick-setting Agent for Shotcrete". The setting time of the cement paste and the strength of the mortar both meet the performance requirements of GB / T 35159-2017 "Quick-setting Agent for Shotcrete", namely, 1d compressive strength > 16.0 MPa, 28d compressive strength ratio > 110%, and 90d compressive strength retention rate > 100%. Attached Figure Description

[0030] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0031] Figure 1 The image shows the XRD pattern of the nano-ferric hydroxide prepared in Example 1 of this invention.

[0032] Figure 2 The XRD pattern is shown in the experimental example of introducing iron ions into the synthesis of ettringite according to the present invention.

[0033] Among them, Fe 3+ The first image shows the XRD pattern when ferric sulfate is added during the synthesis of ettringite, while the second image shows the XRD pattern when ferric ions are not added during the synthesis of ettringite.

[0034] Figure 3 The graph shows the relationship between the weight loss rate of nano-ferric hydroxide and time. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0036] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0037] This invention addresses the safety concerns of current alkali-free quick-setting agents, including low aluminum source concentration, aluminum ion supersaturation, poor stability, low early and late strength, and the presence of toxic fluorine. It provides a fluorine-free and alkali-free liquid quick-setting agent comprising the following components in parts by weight: 40-45 parts aluminum sulfate (e.g., 40, 41, 42, 43, 44, or 45 parts), 1-5 parts amorphous aluminum hydroxide (e.g., 1, 2, 3, 4, or 5 parts), 1-3 parts nano-ferric hydroxide (e.g., 1, 2, or 3 parts), 5-9 parts alkanolamine (e.g., 5, 6, 7, 8, or 9 parts), 0.1-0.4 parts stabilizer (e.g., 0.1, 0.2, 0.3, or 0.4 parts), and 40-45 parts deionized water (e.g., 40, 41, 42, 43, 44, or 45 parts).

[0038] This invention addresses the disadvantages of instability and slow early strength development in alkali-free accelerator systems by using nano-ferric hydroxide as an alkali agent and early strength agent. Without introducing other impurity ions, it can rapidly promote cement mineral hydration, harmlessly improve the early strength of cement, and reduce setting time. On the other hand, it utilizes nano-ferric hydroxide as an alkali agent to promote the formation of polyaluminum and, together with amide organic stabilizers, improves the stability of the system.

[0039] In a preferred embodiment of the present invention, the amine is diethanolamine and / or triethanolamine; the stabilizer is polyacrylamide with a molecular weight of 500w to 800w (e.g., 500w, 600w, 700w, or 800w). The mass ratio of diethanolamine to triethanolamine used in combination is 2:3.

[0040] The present invention uses diethanolamine and / or triethanolamine. On the one hand, diethanolamine and triethanolamine can complex with aluminum ions to increase the stability of the system. On the other hand, they can be used as early strength agents to improve early strength.

[0041] This invention uses polyacrylamide with a molecular weight of 500-800w, which has good dispersing effect and can better improve system stability.

[0042] In a preferred embodiment of the present invention, the average particle size of amorphous aluminum hydroxide is 50-70 nm; the average particle size of nano-ferric hydroxide is 10-30 nm.

[0043] This invention selects amorphous aluminum hydroxide with an average particle size of 50-70 nm and nano-iron hydroxide with an average particle size of 10-30 nm. Under these particle size conditions, amorphous aluminum hydroxide and nano-iron hydroxide have a large specific surface area and a good crystal nucleation effect.

[0044] This invention also proposes a method for preparing a fluorine-free and alkali-free liquid quick-setting agent, comprising the following steps:

[0045] (1) Preparation of amorphous aluminum hydroxide;

[0046] (2) Preparation of nano-ferric hydroxide;

[0047] (3) Weigh each raw material component according to the mass fraction and set aside;

[0048] (4) Take 1 to 3 parts by weight (e.g., 1 part, 2 parts or 3 parts) of alcohol amine, mix the stabilizer, alcohol amine and deionized water, and stir in a water bath at 60 to 80°C (e.g. 60°C, 70°C or 80°C) for 1 to 2 hours (e.g. 1 hour, 1.5 hours or 2 hours) to obtain a suspension.

[0049] (5) Add aluminum sulfate and amorphous aluminum hydroxide to the suspension and stir in a water bath at 60-70°C (e.g., 60°C, 65°C or 70°C) for 1-2 hours (e.g., 1 hour, 1.5 hours or 2 hours) to obtain the quick-setting component.

[0050] (6) Add the remaining mass of alkanolamine and nano-ferric hydroxide to the quick-setting component and stir in a water bath at 60-70°C (e.g., 60°C, 65°C or 70°C) for 1-2 hours (e.g., 1 hour, 1.5 hours or 2 hours) to obtain the final product.

[0051] This invention relates to an alkali-free liquid accelerator with aluminum sulfate and amorphous aluminum hydroxide as the main accelerator components. It achieves the formation of polyaluminum sulfate by reacting aluminum sulfate and highly active amorphous aluminum hydroxide at a specific temperature, and further improves the stability and performance of the system by synthesizing modified nano-ferric hydroxide using the sol-gel method. The polyaluminum sulfate is a polymeric compound formed by reacting aluminum sulfate with an alkalizing agent at a specific temperature and then aging it. Its stability at a certain alkalinity is higher than that of ordinary aluminum sulfate. Currently, most commercially available products increase the aluminum phase concentration by increasing the proportion of aluminum sulfate, which introduces a large amount of sulfate ions along with aluminum ions. Excessive sulfate concentration in the system reduces the durability of cement-based materials against sulfate attack. The synthesis of polyaluminum sulfate using aluminum sulfate and amorphous aluminum hydroxide increases the liquid aluminum phase without introducing excessive sulfate ions, thus promoting setting time without affecting later strength.

[0052] In a preferred embodiment of the present invention, amorphous aluminum hydroxide is prepared by neutralizing aluminum sulfate solution with ammonia water, adjusting the pH of the solution to 6-6.5 to generate amorphous aluminum hydroxide, and then centrifuging, washing, drying, and grinding to obtain the product.

[0053] In a preferred embodiment of the present invention, the mass concentration of aluminum sulfate in the aluminum sulfate solution is 50 g / L; and the volume concentration of ammonia water is 25%.

[0054] The concentration of the aluminum sulfate solution should not be too high, as this will affect the activity of aluminum hydroxide. In a preferred embodiment of the present invention, the preparation method of nano-ferric hydroxide is as follows: neutralize the ferric sulfate solution containing magnesium silicate with ammonia water, adjust the pH of the solution to 6-6.5 to generate nano-ferric hydroxide, centrifuge, wash, and obtain the final product.

[0055] In a preferred embodiment of the present invention, the ferric sulfate solution has a mass concentration of 25 g / L, and the magnesium silicate content in the ferric sulfate solution is 1-2% by mass (e.g., 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%); the ammonia solution has a volume concentration of 25%.

[0056] Freshly prepared nano-ferric hydroxide can partially dissolve under certain acidic conditions, while ferric hydroxide modified with magnesium silicate has a smaller particle size and higher activity after entering the system. Specifically, the modified nano-ferric hydroxide acts as an alkaline agent, promoting the formation of polyaluminum sulfate and providing highly active iron ions to the system. The introduction of iron ions promotes the formation of ettringite, thereby accelerating solidification and improving early strength.

[0057] In a preferred embodiment of the present invention, the stirring speed in step (4) is 600 r / min; the stirring speed in step (5) is 1200 r / min; and the stirring speed in step (6) is 1000 r / min.

[0058] This invention also proposes the application of a fluorine-free and alkali-free liquid quick-setting agent in shotcrete.

[0059] In a specific embodiment of the present invention, when the fluorine-free and alkali-free liquid accelerator is applied to shotcrete, the dosage of the fluorine-free and alkali-free liquid accelerator is 6 to 9% of the cement mass (e.g., 6%, 7%, 8% or 9%).

[0060] The following detailed description of the fluorine-free and alkali-free liquid quick-setting agent and its preparation method according to specific embodiments is provided below.

[0061] The raw materials used in the following examples:

[0062] The alcohol amine is diethanolamine and / or triethanolamine;

[0063] The stabilizer is polyacrylamide with a molecular weight of 500w-800w.

[0064] The average particle size of amorphous aluminum hydroxide is 50–70 nm;

[0065] The average particle size of nano-ferric hydroxide is 10–30 nm.

[0066] Example 1

[0067] A fluorine-free and alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 1 part nano iron hydroxide, 9 parts diethanolamine, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0068] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0069] (1) Preparation of amorphous aluminum hydroxide;

[0070] Dissolve 50g of aluminum sulfate in 1L of deionized water to obtain an aluminum sulfate solution; neutralize the aluminum sulfate solution with 25% (v / v) ammonia water, adjust the pH of the solution to 6.5, and generate amorphous aluminum hydroxide. Centrifuge, wash three times with alcohol, dry in a vacuum drying oven at 50℃ for 48h, and then grind into powder to obtain the final product.

[0071] (2) Preparation of nano-ferric hydroxide;

[0072] Dissolve 25g of ferric sulfate and 0.15g of magnesium silicate in 1L of deionized water to obtain a ferric sulfate solution containing magnesium silicate. Neutralize the ferric sulfate solution containing 1.5% (wt) magnesium silicate with 25% (v / v) ammonia water to adjust the pH to 6.5, generating nano-ferric hydroxide. Centrifuge and wash three times with deionized water to obtain the final product.

[0073] (3) Weigh each raw material component according to the mass fraction and set aside;

[0074] (4) Mix 0.1g stabilizer, 2g diethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0075] (5) Add 40g of aluminum sulfate and 2g of amorphous aluminum hydroxide to the suspension and stir in a 70℃ water bath at 1200r / min for 1h to obtain the quick-setting component;

[0076] (6) Add 7g of diethanolamine and 1g of nano-ferric hydroxide to the quick-setting component, and stir in a 70℃ water bath at 1000r / min for 1.5h to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0077] X-ray diffraction (XRD) analysis was performed on the nano-ferric hydroxide prepared in step (2), and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the poor crystal form of nano-ferric hydroxide indicates that its high solubility allows for the introduction of more active ions, meaning that nano-ferric hydroxide has higher activity.

[0078] Example 2

[0079] A fluorine-free and alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 2 parts nano iron hydroxide, 9 parts diethanolamine, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0080] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0081] (1) Preparation of amorphous aluminum hydroxide;

[0082] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0083] (2) Preparation of nano-ferric hydroxide;

[0084] The preparation method of nano-ferric hydroxide is the same as in Example 1.

[0085] (3) Weigh each raw material component according to the mass fraction and set aside;

[0086] (4) Mix 0.1g stabilizer, 2g diethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0087] (5) Add 40g of aluminum sulfate and 2g of amorphous aluminum hydroxide to the suspension and stir in a 70℃ water bath at 1200r / min for 1h to obtain the quick-setting component.

[0088] (6) Add 7g of diethanolamine and 2g of nano-ferric hydroxide to the quick-setting component, and stir in a 70℃ water bath at 1000r / min for 1.5h to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0089] Example 3

[0090] A fluorine-free and alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 3 parts nano iron hydroxide, 9 parts diethanolamine, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0091] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0092] (1) Preparation of amorphous aluminum hydroxide;

[0093] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0094] (2) Preparation of nano-ferric hydroxide;

[0095] The preparation method of nano-ferric hydroxide is the same as in Example 1.

[0096] (3) Weigh each raw material component according to the mass fraction and set aside;

[0097] (4) Mix 0.1g stabilizer, 2g diethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0098] (5) Add 40g of aluminum sulfate and 2g of amorphous aluminum hydroxide to the suspension and stir in a 70℃ water bath at 1200r / min for 1h to obtain the quick-setting component;

[0099] (6) Add 7g of diethanolamine and 3g of nano-ferric hydroxide to the quick-setting component, and stir in a 70℃ water bath at 1000r / min for 1.5h to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0100] Example 4

[0101] A fluorine-free and alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 3 parts nano iron hydroxide, 9 parts triethanolamine, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0102] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0103] (1) Preparation of amorphous aluminum hydroxide;

[0104] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0105] (2) Preparation of nano-ferric hydroxide;

[0106] The preparation method of nano-ferric hydroxide is the same as in Example 1.

[0107] (3) Weigh each raw material component according to the mass fraction and set aside;

[0108] (4) Mix 0.1g stabilizer, 2g triethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0109] (5) Add 40g of aluminum sulfate and 2g of amorphous aluminum hydroxide to the suspension and stir in a 70℃ water bath at 1200r / min for 1h to obtain the quick-setting component;

[0110] (6) Add 7g of triethanolamine and 3g of nano-ferric hydroxide to the quick-setting component, and stir in a 70℃ water bath at 1000r / min for 1.5h to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0111] Example 5

[0112] A fluorine-free and alkali-free liquid quick-setting agent comprises the following components in parts by weight: 45 parts aluminum sulfate, 3 parts amorphous aluminum hydroxide, 3 parts nano iron hydroxide, 6 parts alkanolamine (diethanolamine and triethanolamine are mixed in a mass ratio of 2:3), 0.2 parts stabilizer (polyacrylamide with a molecular weight of 500w), and 45 parts deionized water.

[0113] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0114] (1) Preparation of amorphous aluminum hydroxide;

[0115] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0116] (2) Preparation of nano-ferric hydroxide;

[0117] The preparation method of nano-ferric hydroxide is the same as in Example 1.

[0118] (3) Weigh each raw material component according to the mass fraction and set aside;

[0119] (4) Mix 0.2g stabilizer, 2g alkanolamine and 45g deionized water, and stir in a 60℃ water bath at 600r / min for 2h to obtain a suspension;

[0120] (5) Add 45g of aluminum sulfate and 3g of amorphous aluminum hydroxide to the suspension and stir in a 60℃ water bath at 1200r / min for 2h to obtain the quick-setting component;

[0121] (6) Add 4g of alkanolamine and 3g of nano-ferric hydroxide to the quick-setting component, and stir in a 60℃ water bath at 1000r / min for 2h to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0122] Example 6

[0123] A fluorine-free and alkali-free liquid quick-setting agent comprises the following components in parts by weight: 43 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 1 part nano iron hydroxide, 9 parts alkanolamine (diethanolamine and triethanolamine are mixed in a mass ratio of 2:3), 0.4 parts stabilizer (polyacrylamide with a molecular weight of 600w), and 40 parts deionized water.

[0124] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0125] (1) Preparation of amorphous aluminum hydroxide;

[0126] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0127] (2) Preparation of nano-ferric hydroxide;

[0128] The preparation method of nano-ferric hydroxide is the same as in Example 1.

[0129] (3) Weigh each raw material component according to the mass fraction and set aside;

[0130] (4) Mix 0.4g stabilizer, 3g alkanolamine and 40g deionized water, and stir in an 80℃ water bath at 600r / min for 1.5h to obtain a suspension;

[0131] (5) Add 43g of aluminum sulfate and 2g of amorphous aluminum hydroxide to the suspension and stir in a 65℃ water bath at 1200r / min for 1.5h to obtain the quick-setting component;

[0132] (6) Add 6g of alkanolamine and 1g of nano-ferric hydroxide to the quick-setting component, and stir in a water bath at 1000r / min for 1h at 65℃ to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0133] Comparative Example 1

[0134] The only difference between the quick-setting agent composition in this comparative example and that in Example 1 is that nano-ferric hydroxide is not involved, and the amount of diethanolamine used is different.

[0135] An alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 2 parts diethanolamine, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0136] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0137] (1) Preparation of amorphous aluminum hydroxide;

[0138] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0139] (2) Weigh each raw material component according to the mass fraction and set aside;

[0140] (3) Mix 0.1g stabilizer, 2g diethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0141] (4) Add 40g of aluminum sulfate and 2g of amorphous aluminum hydroxide to the suspension and stir at 1000r / min for 1.5h in a 70℃ water bath to obtain a colorless, transparent, alkali-free liquid quick-setting agent.

[0142] Comparative Example 2

[0143] The only difference between the quick-setting agent composition in this comparative example and that in Example 3 is that it does not involve nano-ferric hydroxide, but uses ferric sulfate, and the amount of diethanolamine is different.

[0144] An alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 2 parts diethanolamine, 3 parts ferric sulfate, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0145] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0146] (1) Preparation of amorphous aluminum hydroxide;

[0147] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0148] (2) Weigh each raw material component according to the mass fraction and set aside;

[0149] (3) Mix 0.1g stabilizer, 2g diethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0150] (4) Add 40g aluminum sulfate, 2g amorphous aluminum hydroxide and 3g ferric sulfate to the suspension and stir at 1000r / min for 1.5h in a 70℃ water bath to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0151] Comparative Example 3

[0152] The only difference between the quick-setting agent composition in this comparative example and that in Example 3 is that it does not involve nano-ferric hydroxide, but uses ferric nitrate, and the amount of diethanolamine is different.

[0153] An alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 2 parts diethanolamine, 3 parts ferric nitrate, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0154] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0155] (1) Preparation of amorphous aluminum hydroxide;

[0156] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0157] (2) Weigh each raw material component according to the mass fraction and set aside;

[0158] (3) Mix 0.1g stabilizer, 2g diethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0159] (4) Add 40g aluminum sulfate, 2g amorphous aluminum hydroxide and 3g ferric nitrate to the suspension and stir at 1000r / min for 1.5h in a 70℃ water bath to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0160] Comparative Example 4

[0161] The only difference between the quick-setting agent in this comparative example and that in Example 3 is the use of nano-ferric hydroxide without magnesium silicate modification.

[0162] A fluorine-free and alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 2 parts amorphous aluminum hydroxide, 3 parts nano iron hydroxide, 9 parts diethanolamine, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0163] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0164] (1) Preparation of amorphous aluminum hydroxide;

[0165] The preparation method of amorphous aluminum hydroxide is the same as in Example 1.

[0166] (2) Preparation of nano-ferric hydroxide;

[0167] Dissolve 25g of ferric sulfate in 1L of deionized water to obtain a ferric sulfate solution. Neutralize the ferric sulfate solution with 25% (v / v) ammonia water and adjust the pH of the solution to 6.5 to generate nano-ferric hydroxide. Centrifuge and wash three times with deionized water to obtain the final product.

[0168] (3) Weigh each raw material component according to the mass fraction and set aside;

[0169] (4) Mix 0.1g stabilizer, 2g diethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0170] (5) Add 40g of aluminum sulfate and 2g of amorphous aluminum hydroxide to the suspension and stir in a 70℃ water bath at 1200r / min for 1h to obtain the quick-setting component;

[0171] (6) Add 7g of diethanolamine and 3g of nano-ferric hydroxide to the quick-setting component, and stir in a 70℃ water bath at 1000r / min for 1.5h to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0172] Comparative Example 5

[0173] The only difference between the quick-setting agent in this comparative example and that in Example 3 is that it does not involve amorphous aluminum hydroxide, but uses nano-iron hydroxide that is not modified with magnesium silicate.

[0174] An alkali-free liquid quick-setting agent comprises the following components in parts by weight: 40 parts aluminum sulfate, 9 parts diethanolamine, 3 parts nano-ferric hydroxide, 0.1 parts stabilizer (polyacrylamide with a molecular weight of 800w), and 40 parts deionized water.

[0175] The preparation method of this fluorine-free and alkali-free liquid quick-setting agent includes the following steps:

[0176] (1) Preparation of nano-ferric hydroxide;

[0177] Dissolve 25g of ferric sulfate in 1L of deionized water to obtain a ferric sulfate solution. Neutralize the ferric sulfate solution with 25% (v / v) ammonia water and adjust the pH of the solution to 6.5 to generate nano-ferric hydroxide. Centrifuge and wash three times with deionized water to obtain the final product.

[0178] (2) Weigh each raw material component according to the mass fraction and set aside;

[0179] (3) Mix 0.1g stabilizer, 2g diethanolamine and 40g deionized water, and stir in a 70℃ water bath at 600r / min for 1h to obtain a suspension;

[0180] (4) Add 40g of aluminum sulfate to the suspension and stir in a 70℃ water bath at 1200r / min for 1h to obtain the quick-setting component;

[0181] (5) Add 7g of diethanolamine and 3g of nano-ferric hydroxide to the quick-setting component, and stir in a 70℃ water bath at 1000r / min for 1.5h to obtain a reddish-brown alkali-free liquid quick-setting agent.

[0182] Experimental Example

[0183] 1. To investigate the effect of iron ions on the ettringite phase in concrete, iron ions were introduced into the synthesis of ettringite. ettringite was synthesized using calcium nitrate, aluminum sulfate, and sodium hydroxide. Ferric sulfate was added during the synthesis process, and the X-ray diffraction (XRD) patterns were measured with and without added iron ions. The results are as follows: Figure 2 As shown, Fe 3+ The first image shows the XRD pattern when ferric sulfate was added, and the second image shows the XRD pattern when no iron ions were added. This verifies that the iron ions generated from the partial dissolution of nano-ferric hydroxide can form iron-like ettringite, which shortens the setting time.

[0184] Freshly prepared nano-ferric hydroxide was placed in a dialysis bag (with cement clinker outside the bag), and the weight loss rate of the nano-ferric hydroxide was analyzed over time. The results are as follows: Figure 3As shown, the weight loss rate inside the dialysis bag changed from positive to negative over time, indicating that the weight inside the bag first decreased and then increased. This suggests that ions from outside the dialysis bag entered the bag and formed other substances on the nano-iron hydroxide, verifying the existence of crystal nucleation in the nano-iron hydroxide.

[0185] 2. The relevant properties of commercially available alkali-free liquid accelerators, as well as those obtained in the examples and comparative examples, were determined according to GB / T 35159-2017 "Accelerators for Shotcrete". Ordinary Portland cement was used, the dosage of the liquid accelerator was 8% of the cement mass, and the water-cement ratio (weight ratio of water to cement) was 0.35. The results are shown in Table 1 below.

[0186] Table 1. Performance Comparison of Different Alkali-Free Liquid Accelerators

[0187]

[0188] As shown in Table 1, compared with commercially available alkali-free liquid accelerators, the fluorine-free and alkali-free liquid accelerator of this application exhibits higher 1-day compressive strength (>16 MPa) and higher 28-day compressive strength (>110%) at the same dosage, and also demonstrates better system stability. Compared with the comparative example, the introduction of nano-ferric hydroxide in this application shortens the setting time, improves the mortar strength, and exhibits the best system stability.

[0189] In summary, the fluorine-free and alkali-free liquid accelerator prepared by this invention uses nano-ferric hydroxide and amorphous aluminum hydroxide, which not only increases the stability of the system but also improves the 1-day compressive strength, promotes the formation of cement hydration products, and makes the cement hydration products more compact. This effectively solves the defect of low early strength of alkali-free liquid accelerators, while having no effect on later strength.

[0190] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fluorine-free and alkali-free liquid quick-setting agent, characterized in that, It comprises the following components in parts by weight: 40-45 parts aluminum sulfate, 1-5 parts amorphous aluminum hydroxide, 1-3 parts nano iron hydroxide, 5-9 parts alkanolamine, 0.1-0.4 parts stabilizer, and 40-45 parts deionized water; The average particle size of the nano-ferric hydroxide is 10~30nm; the preparation method of nano-ferric hydroxide is as follows: neutralize the ferric sulfate solution containing magnesium silicate with ammonia water, adjust the pH of the solution to 6~6.5 to generate nano-ferric hydroxide, centrifuge and wash to obtain the nano-ferric hydroxide.

2. The fluorine-free and alkali-free liquid quick-setting agent as described in claim 1, characterized in that, The alkanolamine is diethanolamine or / and triethanolamine; When the alkanolamine is diethanolamine and triethanolamine, the mixing mass ratio of diethanolamine to triethanolamine is 2:3; The stabilizer is polyacrylamide with a molecular weight of 500w to 800w.

3. The fluorine-free and alkali-free liquid quick-setting agent as described in claim 1, characterized in that, The amorphous aluminum hydroxide has an average particle size of 50~70 nm.

4. The method for preparing the fluorine-free and alkali-free liquid quick-setting agent according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Preparation of amorphous aluminum hydroxide; (2) Preparation of nano-ferric hydroxide; (3) Weigh each raw material component according to its mass percentage and set aside; (4) Take 1-3 parts by weight of alkanolamine, mix the stabilizer, alkanolamine and deionized water, and stir at 60-80℃ for 1-2 hours to obtain a suspension; (5) Add aluminum sulfate and amorphous aluminum hydroxide to the suspension and stir at 60~70℃ for 1h~2h to obtain the quick-setting component; (6) Add the remaining mass of alkanolamine and nano-ferric hydroxide to the quick-setting component and stir at 60~70℃ for 1h~2h to obtain the product.

5. The preparation method of the fluorine-free and alkali-free liquid quick-setting agent as described in claim 4, characterized in that, The preparation method of amorphous aluminum hydroxide is as follows: neutralize aluminum sulfate solution with ammonia water, adjust the pH of the solution to 6~6.5 to generate amorphous aluminum hydroxide, centrifuge, wash, dry and grind to obtain the product; The aluminum sulfate solution has a mass concentration of 50 g / L; the ammonia solution has a volume concentration of 25%.

6. The preparation method of the fluorine-free and alkali-free liquid quick-setting agent as described in claim 4, characterized in that, The stirring speed in step (4) is 600 r / min; the stirring speed in step (5) is 1200 r / min; and the stirring speed in step (6) is 1000 r / min.

7. The preparation method of the fluorine-free and alkali-free liquid quick-setting agent as described in claim 1, characterized in that, The ferric sulfate solution has a ferric sulfate concentration of 25 g / L and a magnesium silicate content of 1-2% by mass; the ammonia solution has a volume concentration of 25%.

8. The application of the fluorine-free and alkali-free liquid quick-setting agent as described in any one of claims 1 to 3 in shotcrete.

9. The application as described in claim 8, characterized in that, The dosage of fluorine-free and alkali-free liquid accelerator is 6-9% of the cement mass.

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