A nanosilicate gel and a method for preparing the same

Abstract

The application discloses a kind of nanometer silicate gel and preparation method thereof, by weight fraction, nanometer silicate gel includes the following components: nanometer silicon oxide, superfine grinding clinker, orthosilicic acid, deionized water, eluant, silane coupling agent, nanometer cellulose;Wherein, nanometer silicon oxide 15~23 parts, superfine grinding clinker 54~90 parts, orthosilicic acid 20~26 parts, deionized water 1200~1800 parts, eluant 0.3~0.5 parts, silane coupling agent 16~29 parts, nanometer cellulose 17~28 parts.Eluent includes one or more of CuSO4, FeSO4, Na2SO4.By the above mode, the nanometer silicate gel prepared by the application can be externally added to concrete to improve the workability and early strength of concrete.

Description

Technical Field

[0001] This invention relates to the field of silicate gel technology, and more specifically to a nano-silicate gel and its preparation method. Background Technology

[0002] In the ready-mixed concrete industry, there is a lack of reusable admixtures that can effectively improve both workability and early strength of concrete. Currently, accelerators and viscosity modifiers are used separately to address both needs. However, the use of organic admixtures for adjustments is often limited by raw material availability; when concrete raw materials change, the ratio of organic admixtures to the original concrete mix may become incompatible. Therefore, there is a need to design products that can effectively improve both early strength and workability of concrete. Summary of the Invention

[0003] The technical problem to be solved by this invention is: This invention proposes a nano-silicate gel and its preparation method to solve the problem of the difficulty in adjusting the cohesiveness and early strength of concrete, and to significantly reduce the possibility of concrete segregation.

[0004] The technical solution of the present invention is: a nano silicate gel, comprising, by weight, 15-23 parts of nano silica, 54-90 parts of ultrafine ground clinker, 12-16 parts of orthosilicic acid, 1200-1800 parts of deionized water, 0.3-0.5 parts of dissolving agent, 16-29 parts of silane coupling agent, and 17-28 parts of nanocellulose.

[0005] Preferably, the nano-silica is prepared by the sol-gel method, with a particle size between 20 and 60 nm, a purity of 99%, and an amount of 17 to 21 parts.

[0006] Preferably, the ultrafine powder clinker includes one or both of milled tricalcium silicate and milled dicalcium silicate. The milled tricalcium silicate is obtained by milling tricalcium silicate through a high-fineness mill, with a fineness between 8 and 15 μm and a purity of 99%. The milled dicalcium silicate is obtained by milling dicalcium silicate through a high-fineness mill, with a fineness between 8 and 15 μm and a purity of 99%, and the dosage is 68 to 76 parts.

[0007] Preferably, the orthosilicic acid is a colorless and transparent colloid with the chemical formula H4SiO4 and a density of 2.62–2.65 mg / m³. 3 The dosage is 13 to 15 portions.

[0008] The deionized water is pure water that has been treated to remove ionized substances.

[0009] Preferably, the dissolving agent is one or more of CuSO4, FeSO4, and Na2SO4.

[0010] Preferably, the silane coupling agent is γ-aminopropyltriethoxysilane, and the amount used is 19 to 26 parts.

[0011] Preferably, the nanocellulose has a width of 20-50 nm, a length of 0.8-2 μm, a purity of 99%, and is used in amounts of 21-24 parts.

[0012] The preparation method of nano-silicate gel includes the following steps:

[0013] Step 1: Weigh the components according to the mass ratio. Add nano-silica and ultrafine ground clinker to a planetary mixer and mix for 15 seconds. Add 20-25 parts of deionized water to the planetary mixer and mix for 150 seconds to obtain a gelling component slurry. After the slurry has stood for 240 seconds, add 575-780 parts of deionized water and orthosilicic acid while stirring. After the addition is complete, stir for more than 300 seconds to obtain the initial silicate gel. Let the initial silicate gel stand for 150 minutes. During this process, the ultrafine ground clinker undergoes a hydration reaction to generate calcium hydroxide and hydrated calcium silicate gel. The nano-silica reacts with the products... Calcium hydroxide can undergo a secondary reaction to form hydrated calcium silicate gel. This process increases the formation of calcium silicate products while consuming some calcium hydroxide, thus increasing the concentration of the hydrated calcium silicate gel. Simultaneously, the addition of orthosilicic acid not only consumes residual calcium hydroxide and forms hydrated calcium silicate gel, but also allows excess orthosilicic acid to dissolve and disperse between the clinker particles and the hydrated calcium silicate products. In deionized water, this orthosilicic acid undergoes a condensation reaction, forming a network-like structure with strong water retention. This structure increases the surface tension of the hydrated calcium silicate gel suspension, resulting in a state exhibiting non-Newtonian fluid characteristics. To prevent the calcium silicate gels formed during the hydration process from overlapping and forming continuous structural units, more deionized water is added and continuously stirred to disperse the hydrated calcium silicate products, forming individual nano-sized hydrated calcium silicate. The condensation of silicic acid in the suspension keeps the unreacted clinker and hydrated calcium silicate in a dispersed state, preventing the subsequent hydration products from overlapping and forming large particle structures.

[0014] Step 2: Stir the initial silicate gel after it has been allowed to stand at 300 r / min, and add 0.3 to 0.5 parts of dissolving agent dropwise at a uniform rate, controlling the dropwise addition time to 30 to 35 min, to obtain dissolved silicate gel. At the same time, add nanocellulose to 600 to 1000 parts of deionized water and stir to dissolve, to obtain nanocellulose solution.

[0015] Step 3: Add the nanocellulose solution to the dissolved silicate gel and stir at 500 r / min for 60 s. Then, add the silane coupling agent into the mixer and stir continuously for 120 s to obtain a nanosilicate gel suspension. After the suspension has stood for 24 h, filter out the excess water using a filter press. Place the filter product in an oven and set the oven temperature to 120-140 ℃. Bake for 24 h to obtain nanosilicate gel powder.

[0016] In steps two and three, the dissolving agent absorbs free calcium from the suspension, further improving the purity of the reaction product. In an aqueous medium, the ethoxysilane groups of the silane coupling agent hydrolyze to form silanols. The surface of nanocellulose contains a large number of hydroxyl groups, and the silanols undergo a condensation reaction with the hydroxyl groups to form stable covalent bonds. The unreacted hydroxyl groups on the surface of the nanocellulose are adsorbed onto the surface of the hydrated calcium silicate gel. Thus, a nano-silicate gel with the ability to regulate the cohesiveness and early strength of concrete is obtained.

[0017] Application of nano-silicate gel in concrete.

[0018] The beneficial effects of this invention are:

[0019] 1. The nano-silicate gel powder prepared in this invention is added to concrete. After thorough stirring, the nano-hydrated calcium silicate gel particles are uniformly dispersed in the concrete paste. The silanol end of the silane coupling agent is adsorbed on the surface of the nano-hydrated calcium silicate along with the nano-cellulose. The large number of hydroxyl groups on the surface of the nano-cellulose increases the hydrogen bonding force of water molecules, thereby making the concrete paste more viscous. The network structure formed by the condensation silica attached to the surrounding area reduces the flow between water molecules, thereby improving the overall fluid cohesiveness of the concrete.

[0020] 2. The uniformly dispersed nano-calcium silicate gel particles in the concrete paste can fully exert the "induced molding" effect. The strength structure formed by the hydration of the cementitious material paste in the concrete can be rapidly formed on the nano-calcium silicate gel particles and interconnected to form strength. At the same time, the composition of the nano-calcium silicate gel particles is the same as that of the hydration products of the concrete cementitious material paste. The nano-calcium silicate gel can fill the gaps formed after the concrete hardens, reduce the generation of microcracks, effectively improve the early strength of concrete, and reduce the possibility of concrete cracking.

[0021] 3. As the hydration reaction of the slurry in the concrete proceeds, the alkalinity inside the concrete increases, and the nanocellulose no longer adsorbs on the surface of the nanosilicate gel. The nanocellulose in the slurry undergoes a condensation reaction in the alkaline environment to form long-chain fiber macromolecules. The fiber macromolecules are distributed in the strength structure of the hardened concrete, which can effectively improve the toughness of the concrete and enhance its flexural strength. Detailed Implementation

[0022] The technical solution of the present invention will be further illustrated below through specific implementation examples. These examples are intended to explain the present invention and not to limit it.

[0023] Example 1: Preparation of a nano-silicate gel, the steps of which are as follows:

[0024] (1) By mass fraction: 15 parts of nano-silica and 54 parts of ultrafine powder clinker were added to a planetary mixer and stirred for 15s. 20 parts of deionized water were added to the planetary mixer and stirred for 150s to obtain a gelling component slurry. After the slurry was allowed to stand for 240s, 580 parts of deionized water and 12 parts of orthosilicic acid were added while stirring the slurry. After the addition was completed, the mixture was stirred for more than 300s to obtain the initial silicate gel. The initial silicate gel was allowed to stand for 150min.

[0025] (2) Stir the initial silicate gel that has been allowed to stand in step (1) at a speed of 300 r / min, and add 0.4 parts of dissolving agent dropwise at a uniform speed during the process, controlling the dropwise addition time to be 30-35 min, to obtain dissolved silicate gel. At the same time, add 17 parts of nanocellulose to 600 parts of deionized water and stir to dissolve, to obtain nanocellulose solution.

[0026] (3) Add the nanocellulose solution from step (2) to the dissolved silicate gel and stir at 500 r / min for 60 s. Then add 16 parts of silane coupling agent into the mixer and stir continuously for 120 s to obtain a nanosilicate gel suspension. After the suspension is left to stand for 24 h, filter out the excess water using a filter press. Place the filter product in an oven and set the oven temperature to 120 ℃. After baking for 24 h, obtain nanosilicate gel powder.

[0027] Example 2: Preparation of a nano-silicate gel, the steps of which are as follows:

[0028] (1) By mass fraction: 19 parts of nano-silica and 72 parts of ultrafine powder clinker were added to a planetary mixer and stirred for 15s. 22 parts of deionized water were added to the planetary mixer and stirred for 150s to obtain a gelling component slurry. After the slurry was allowed to stand for 240s, 640 parts of deionized water and 14 parts of orthosilicic acid were added while stirring the slurry. After the addition was completed, the mixture was stirred for more than 300s to obtain the initial silicate gel. The initial silicate gel was allowed to stand for 150min.

[0029] (2) Stir the initial silicate gel that has been allowed to stand in step (1) at a speed of 300 r / min, and add 0.4 parts of dissolving agent dropwise at a uniform speed during the process, controlling the dropwise addition time to be 30-35 min, to obtain dissolved silicate gel. At the same time, add 22 parts of nanocellulose to 700 parts of deionized water and stir to dissolve, to obtain nanocellulose solution.

[0030] (3) Add the nanocellulose solution from step (2) to the dissolved silicate gel and stir at 500 r / min for 60 s. Then add 23 parts of silane coupling agent into the mixer and stir continuously for 120 s to obtain a nanosilicate gel suspension. After the suspension is left to stand for 24 h, filter out the excess water using a filter press. Place the filter product in an oven and set the oven temperature to 130 ℃. After baking for 24 h, obtain nanosilicate gel powder.

[0031] Example 3: Preparation of a nano-silicate gel, the steps of which are as follows:

[0032] (1) By mass fraction: 23 parts of nano-silica and 54-90 parts of ultrafine powder clinker are added to a planetary mixer and stirred for 15s. 25 parts of deionized water are added to the planetary mixer and stirred for 150s to obtain a gelling component slurry. After the slurry has stood for 240s, 720 parts of deionized water and 16 parts of orthosilicic acid are added while stirring the slurry. After the addition is completed, the mixture is stirred for more than 300s to obtain the initial silicate gel. The initial silicate gel is then left to stand for 150min.

[0033] (2) Stir the initial silicate gel that has been allowed to stand in step (1) at a speed of 300 r / min, and add 0.4 parts of dissolving agent dropwise at a uniform speed during the process, controlling the dropwise addition time to be 30-35 min, to obtain dissolved silicate gel. At the same time, add 28 parts of nanocellulose to 1000 parts of deionized water and stir to dissolve, to obtain nanocellulose solution.

[0034] (3) Add the nanocellulose solution from step (2) to the dissolved silicate gel and stir at 500 r / min for 60 s. Then add 29 parts of silane coupling agent into the mixer and stir continuously for 120 s to obtain a nanosilicate gel suspension. After the suspension is left to stand for 24 h, filter out the excess water using a filter press. Place the filter product in an oven and set the oven temperature to 140 ℃. After baking for 24 h, obtain nanosilicate gel powder.

[0035] The nano-silicate gels prepared in Examples 1-3 were incorporated into C30 and C60 grade concrete at a cementitious material ratio of 5%, respectively. The concrete mix proportions by mass are shown in the table below:

[0036] Table 1 Concrete Mix Proportions

[0037] cement Mineral powder fly ash gravel Manufactured sand water Nano silicate gel C30 190 40 90 940 900 160 16 C60 280 60 80 1020 890 135 21

[0038] In addition, control groups were set up: control group 1 was C30 concrete without nano-silicate gel, and control group 2 was C60 concrete without nano-silicate gel. Their properties are shown in Tables 2 and 3.

[0039] Table 2 Performance Indicators of C30 Concrete

[0040]

[0041] Table 3 Performance Indicators of C60 Concrete

[0042]

[0043] The results in Tables 2 and 3 show that the early strength (1d and 7d) of both C30 and C60 grade concrete was significantly improved after incorporating nano-silicate gel. In particular, in Example 2, the 1d compressive strength of C30 and C60 concrete increased by 190% and 158%, respectively. Furthermore, despite this significant improvement in early strength, their later strength was not lower than that of the control group. Moreover, the flexural strength of the concrete also showed a substantial increase under the influence of nano-cellulose.

[0044] After incorporating nano-silicate gel, the cohesiveness and water retention of concrete are improved, thus significantly increasing the segregation resistance of concrete. In Examples 2 and 3, the segregation resistance of C30 and C60 concrete both reached 99%.

[0045] A comprehensive comparison reveals that when the formulation value of nano-silicate gel is lower than the preferred range, the effect on improving early strength and workability is not as good as the value within the preferred range; when it is higher than the preferred range, the strength of concrete is not lower than the preferred range, but the slump and spread decrease rapidly, and its fluidity is far lower than the preferred range.

[0046] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A nanosilicate gel, characterized in that, By weight, including nano silicon oxide 15~23 parts, superfine grinding clinker 54~90 parts, orthosilicic acid 12~16 parts, deionized water 1200~1800 parts, elution agent 0.3~0.5 parts, silane coupling agent 16~29 parts, nano cellulose 17~28 parts.

2. Nanosilicate gel according to claim 1, characterized in that: The nano silicon oxide is prepared by sol-gel method, the particle size is between 20~60nm, the purity is 99%, and the amount is 17~21 parts.

3. Nanosilicate gel according to claim 1, characterized in that: The superfine grinding clinker includes one or both of ground tricalcium silicate and ground dicalcium silicate, wherein the ground tricalcium silicate is obtained by grinding tricalcium silicate by a high-fineness grinder, the fineness is between 8~15 microns, the purity is 99%, and the amount is 68~76 parts.

4. Nanosilicate gel according to claim 1, characterized in that: The orthosilicic acid is colorless transparent colloid, the chemical formula is H4SiO4, and the amount is 13~15 parts.

5. Nanosilicate gel according to claim 1, characterized in that: The elution agent is one or more of CuSO4, FeSO4 and Na2SO4.

6. Nanosilicate gel according to claim 1, characterized in that: The silane coupling agent is γ―aminopropyl triethoxysilane, and the amount is 19~26 parts.

7. Nanosilicate gel according to claim 1, characterized in that: The nano cellulose has a width of 20~50nm, a length of 0.8~2 microns, a purity of 99%, and an amount of 21~24 parts.

8. Process for the preparation of nanosilicate gels according to any one of claims 1 to 7, characterized in that: Including the following steps: Step one: weigh the amount of each component according to the mass ratio, put the nano silicon oxide and superfine grinding clinker into the planetary mixer and stir for 15s, add 20~25 parts of deionized water into the planetary mixer and stir for 150s to obtain a slurry of gelling components, then let the slurry stand for 240s, add 575~780 parts of deionized water and orthosilicic acid to the stirring slurry, stir for more than 300s after the feeding is completed to obtain an initial silicate gel, and then let the initial silicate gel stand for 150min; Step two: stir the initial silicate gel after standing at a speed of 300r / min, and add the elution agent at a constant speed during the stirring, control the dropping time to be 30~35min to obtain an eluted silicate gel, and at the same time, add the nano cellulose into 600~1000 parts of deionized water to stir and dissolve to obtain a nano cellulose solution; Step three: add the nano cellulose solution to the eluted silicate gel, stir at a speed of 500r / min for 60s, then add the silane coupling agent into the stirrer and continue to stir for 120s to obtain a nano silicate gel suspension, let the suspension stand for 24h, then use a filter press to filter out excess water, put the filter press product into an oven, set the oven temperature to 120~140℃, and bake for 24h to obtain a nano silicate gel powder.

9. The application of the nano silicate gel in concrete according to any one of claims 1-7.

Images