Method for preparing a material having both chlorine fixation and cement hydration promotion functions

Abstract

The application discloses a preparation method of a functional material with the functions of chlorine fixation and cement hydration promotion, and belongs to the field of building material manufacturing.The application is aimed at solving the problems that the high content of LDH affects the mechanical properties of cement-based materials, and that sulfate ions and carbonate ions compete with chlorine ions for adsorption and displace the adsorbed chlorine ions.The method comprises the following steps: stirring a certain volume of ethanol and ammonia water in a water bath, adding TEOs to obtain solution A;mixing ethanol and deionized water, adding LDH, and ultrasonic dispersing for ten minutes to obtain solution B;pouring solution B into solution A, filtering and drying, drying, grinding into powder, and heating at 500 DEG C for 5 hours to further grind, so as to obtain the functional material.The composite material prepared by the method has better dispersity, the adsorption performance of chlorine ions is promoted, the negative influence of CLDH on the mechanical properties of cement can be offset, and the release of chlorine ions in the LDH can be prevented to a certain extent.

Description

TECHNICAL FIELD

[0001] The present application relates to a cement-based functional material preparation method, and belongs to the field of building material manufacturing. BACKGROUND

[0002] In cement-based materials, the ingress of chloride is widely considered to be a detrimental process affecting the durability of concrete, because the increase in the concentration of free chloride ions in the pore solution is a key condition for the initiation of steel corrosion, which is the main cause of failure of reinforced concrete structures. Chloride ions in concrete are generally in two forms of binding, namely chemical binding to Friedel's salt and physical binding to calcium silicate hydrate (i.e. in the C-(A)-S-H diffusion layer). For ordinary cement-based materials, the contribution of chemical binding is about 70%, and the contribution of physical binding is about 25-28%. Some scholars have found that alkali-activated slag cement has a potential high chloride ion binding capacity, because compared with ordinary Portland cement systems, the product has a double-layer hydroxide (hydrotalcite phase), i.e. LDHs, with a general formula of , wherein M 2+ and M 3+ represent divalent and trivalent metal ions (such as Mg 2+ , Al 3+ , etc.), and A n- represents interlayer anions such as CO3 2- , SO4 2- , OH − , Cl − , etc. This mineral with a positively charged layered structure can absorb chloride ions through anion exchange capacity in a brucite-like lattice structure in which divalent cations are partially replaced by trivalent cations, thereby retaining chloride ions in the alkali-activated reaction product LDHs through chemical binding, delaying the migration of chloride ions in concrete, and thus reducing the migration rate of chloride ions. In addition, LDHs also exhibit another important feature "memory effect", the crystalline phase of LDHs decomposes at a temperature range of 500-600°C to form a new crystal structure, called calcined LDH (CLDH or LDO), and CLDH can be rehydrated into LDH when appropriate anions enter its layered crystal structure through an aqueous solution. The rehydration process of CLDHs not only includes the adsorption of chloride ions, but also the release of hydroxide ions, which is beneficial to improve the corrosion resistance of steel bars. While using LDHs and CLDHs to solidify and adsorb chloride ions, there are often many problems, such as that a too high amount of LDHs will affect the mechanical properties of cement-based materials, and a too high amount of LDHs will also cause LDH aggregation; sulfate and carbonate ions compete with chloride ions for adsorption, resulting in a decrease in the ability of LDHs to absorb chloride ions, or displacing the already adsorbed chloride ions. SUMMARY

[0003] The application aims to solve the technical problems that too high LDH content will affect the mechanical properties of cement-based materials, to a certain extent, improve the chloride ion absorption performance, sulfate and carbonate ions compete with chloride ions for adsorption, resulting in reduced LDH chloride ion absorption performance, and replace the adsorbed chloride ions, and provides a preparation method of a functional material with both chloride fixation and cement hydration promotion functions.

[0004] The preparation method of the functional material with both chloride fixation and cement hydration promotion functions is as follows:

[0005] I. Under room temperature conditions, ethanol and ammonia water with a volume ratio of 60:1~3 are stirred in a 70℃ water bath for half an hour, then TEOs are added, the volume ratio of TEOs to ammonia water is 6:1, and the stirring is continued in a 70℃ water bath for 1 hour to obtain solution A;

[0006] II. Ethanol and deionized water with a volume ratio of 1:2 are mixed, then LDH is added, the mass ratio of LDH to water is 1:4, and ultrasonic dispersion is performed for ten minutes to obtain solution B;

[0007] III. Solution B is poured into solution A, the volume ratio of ethanol in solution A to ethanol in solution B is 3:2, stirring is performed in a 70℃ water bath for 3 hours, filtration and drying are performed, after drying, grinding into powder, and then placed into a high-temperature furnace, heating at 500℃ for 5 hours, and further grinding, the functional material with both chloride fixation and cement hydration promotion functions is obtained, and the material is recorded as SiO2@CLDH.

[0008] The application proposes a new method for preparing SiO2@CLDH composite material by modifying CLDH with nano-silicon dioxide, the composite material prepared by the method has better dispersity, the adsorption performance of chloride ions is promoted when a small amount of nano-silicon dioxide is loaded, the surface covered nano-silicon dioxide can offset the negative impact of CLDH on the mechanical properties of cement, and the early reaction rate and early strength development of cement can be improved, in addition, when encountering sulfate or carbonate, the silicon dioxide on the surface of the composite material reacts with calcium hydroxide to generate a gel layer, which can prevent the release of chloride ions in LDH to a certain extent. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 It is a morphology diagram of the functional material with both chloride fixation and cement hydration promotion functions SiO2@CLDH prepared in experiment I;

[0010] Figure 2 It is a hydration heat diagram of cement after 5% of the functional materials with both chloride fixation and cement hydration promotion functions SiO2@CLDH-1 and 3 prepared in experiments I and III and the corresponding control group and CLDH are added into cement respectively;

[0011] Figure 3 is the chloride ion adsorption isotherm diagram of the SiO2@CLDH and CLDH prepared in Experiment 1, which has the functions of chlorine fixation and cement hydration promotion. DETAILED DESCRIPTION

[0012] The technical solution of the present application is not limited to the following specific embodiments, but also includes any combination of the specific embodiments.

[0013] Specific embodiment one: the preparation method of the functional material with the functions of chlorine fixation and cement hydration promotion is as follows:

[0014] I. Under room temperature conditions, 60:1-3 volume ratio of ethanol and ammonia water is stirred in a 70℃ water bath for half an hour, then TEOs are added, the volume ratio of TEOs to ammonia water is 6:1, and the stirring is continued in a 70℃ water bath for 1 hour to obtain solution A;

[0015] II. 1:2 volume ratio of ethanol and deionized water is mixed, then LDH is added, the mass ratio of LDH to water is 1:4, and ultrasonic dispersion is carried out for ten minutes to obtain solution B;

[0016] III. Solution B is poured into solution A, the volume ratio of ethanol in solution A to ethanol in solution B is 3:2, stirring is carried out in a 70℃ water bath for 3 hours, filtration and drying are carried out, after drying, grinding into powder, and then put into a high-temperature furnace, heating at 500℃ for 5 hours, further grinding, and then the functional material SiO2@CLDH with the functions of chlorine fixation and cement hydration promotion is obtained.

[0017] Specific embodiment two: the difference between this embodiment and specific embodiment one is that in step one, 60:2 volume ratio of ethanol and ammonia water is stirred in a 70℃ water bath for half an hour, then TEOs with a volume ratio of 6:1 to ammonia water are added. The others are the same as specific embodiment one.

[0018] Specific embodiment three: the difference between this embodiment and specific embodiment one or two is that in step one, 60:3 volume ratio of ethanol and ammonia water is stirred in a 70℃ water bath for half an hour, TEOs with a volume ratio of 6:1 to ammonia water are added; the ultrasonic frequency in step two is 40kHz. The others are the same as specific embodiment one or two.

[0019] The following experiments are used to verify the effect of the present application:

[0020] Raw materials: tetraethyl orthosilicate (TEOS), ethanol, ammonia water (mass fraction of 28%) and commercial MgAl-CO3 LDH (Mg4Al2(OH) 12 CO3⋅mH2O). All reagents are of analytical purity and can be directly used without purification. Deionized water is used in the whole experiment.

[0021] Experiment one:

[0022] The preparation method of the functional material with the functions of chlorine fixation and cement hydration promotion is as follows:

[0023] I. Under room temperature conditions, 30 ml of ethanol and 0.5 ml of ammonia water are added to a flask, stirred in a 70°C water bath for half an hour, then 3 ml of TEOs is added, and stirring is continued in a 70°C water bath for 1 hour to obtain solution A;

[0024] II. 20 ml of ethanol and 40 ml of deionized water are mixed, then 10 g of LDH is added, and ultrasonic dispersion is carried out for ten minutes to obtain solution B;

[0025] III. Solution B is poured into solution A, stirred in a 70°C water bath for 3 hours, filtered and dried, after drying, ground into powder, placed into a high-temperature furnace, heated at 500°C for 5 hours, and further ground, to obtain the functional material SiO2@CLDH-1 with the functions of chlorine fixation and cement hydration promotion, and the SiO2 content accounts for 10% of the composite material.

[0026] Experiment two:

[0027] The preparation method of the functional material with the functions of chlorine fixation and cement hydration promotion is as follows:

[0028] I. Under room temperature conditions, 30 ml of ethanol and 1 ml of ammonia water are added to a flask, stirred in a 70°C water bath for half an hour, then 6 ml of TEOs is added, and stirring is continued in a 70°C water bath for 1 hour to obtain solution A;

[0029] II. 20 ml of ethanol and 40 ml of deionized water are mixed, then 10 g of LDH is added, and ultrasonic dispersion is carried out for ten minutes to obtain solution B;

[0030] III. Solution B is poured into solution A, stirred in a 70°C water bath for 3 hours, filtered and dried, after drying, ground into powder, placed into a high-temperature furnace, heated at 500°C for 5 hours, and further ground, to obtain the functional material SiO2@CLDH-2 with the functions of chlorine fixation and cement hydration promotion, and the SiO2 content accounts for 20% of the composite material.

[0031] Experiment three:

[0032] The preparation method of the functional material with the functions of chlorine fixation and cement hydration promotion is as follows:

[0033] I. Under room temperature conditions, 30 ml of ethanol and 1.5 ml of ammonia water are added to a flask, stirred in a 70°C water bath for half an hour, then 9 ml of TEOs is added, and stirring is continued in a 70°C water bath for 1 hour to obtain solution A;

[0034] II. 20ml of ethanol and 40ml of deionized water are mixed, then 10g of LDH is added and ultrasonic dispersed for ten minutes to obtain solution B;

[0035] III. Solution B is poured into solution A, stirred in a 70℃ water bath for 3 hours, filtered and dried, after drying, ground into powder, put into a high temperature furnace, heated at 500℃ for 5 hours, further ground, to obtain the functional material SiO2@CLDH-3 with solid chlorine and promoting cement hydration, the SiO2 content accounts for 30% of the composite material.

[0036] Figure 2 CLDH, synthesized composite material SiO2@CLDH-1, SiO2@CLDH-3, separate CLDH and nano-SiO2 (not synthesized, commercially available, to verify that the synthesized composite material has better dispersion of silicon dioxide), are added to cement, the hydration heat is measured, and the reaction rate of cement (the heat release corresponds to the reaction degree and reaction rate of cement, the greater the heat release, the faster the heat release rate corresponds to the greater the reaction degree and the faster the reaction rate of cement) is measured.

Claims

1. A method for preparing a material having both chlorine fixation and cement hydration promotion functions, characterized in that The preparation method of the material with the functions of chlorine fixation and cement hydration promotion is as follows: I. Under the room temperature, the ethanol and ammonia water with the volume ratio of 60:1-3 are stirred in the water bath at 70 DEG C for half an hour, then TEOS is added, the volume ratio of TEOS and ammonia water is 6:1, the stirring in the water bath at 70 DEG C is continued for 1 hour, solution A is obtained; II. The ethanol and deionized water with the volume ratio of 1:2 are mixed, then LDH is added, the mass ratio of LDH and water is 1:4, ultrasonic dispersion is carried out for ten minutes, solution B is obtained; III. Solution B is poured into solution A, the volume ratio of ethanol in solution A and ethanol in solution B is 3:2, the stirring in the water bath at 70 DEG C is carried out for 3 hours, filtration and drying are carried out, after drying, grinding into powder, putting into high temperature furnace, heating at 500 DEG C for 5 hours, grinding, the material SiO2@CLDH with the functions of chlorine fixation and cement hydration promotion is obtained, the maximum adsorption capacity Qmax of the material to chlorine ion is 153.9 mg / g.

2. The method for preparing the material with both functions of fixing chlorine and promoting cement hydration according to claim 1, characterized in that I. The ethanol and ammonia water with the volume ratio of 60:2 are stirred in the water bath at 70 DEG C for half an hour, then TEOS with the volume ratio of 6:1 to ammonia water is added.

3. The method for preparing the material with both functions of fixing chlorine and promoting cement hydration according to claim 1, characterized in that I. The ethanol and ammonia water with the volume ratio of 60:3 are stirred in the water bath at 70 DEG C for half an hour, TEOS with the volume ratio of 6:1 to ammonia water is added; the ultrasonic frequency in step II is 40 kHz.

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