Cement-based material, method for its production and use

Abstract

The application discloses a cement-based material and a preparation method and application thereof. The cement-based material comprises the following raw materials in mass parts: cement: 100 parts; quartz sand: 80-100 parts; nano-silicon dioxide: 0.5-3.5 parts; polycarboxylic acid water reducing agent: 0.5-1.5 parts; dispersant: 0-1 part; and water: 20-35 parts. The preparation method of the cement-based material comprises the following steps: 1) preparing a nano-silicon dioxide dispersion liquid; 2) preparing a cement mortar; 3) pre-vibration and vacuum vibration compaction of the cement mortar; and 4) water vapor curing and water immersion curing of a formed piece. The cement-based material has the advantages of high flexural strength, low porosity, good durability and the like, and the preparation method is simple, the production cost is low, the cement-based material can be applied in a harsh marine environment, and is suitable for large-scale industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a cement-based material and a preparation method and application thereof. BACKGROUND

[0002] The cement-based material is a composite material taking cement as a matrix, and is the most widely used and largest amount of artificial material in engineering construction. However, due to a large number of ions existing in the marine environment and the complex hydrological environment, the existing cement-based material used in marine construction engineering is prone to problems such as carbonation reaction, steel corrosion, alkali-aggregate reaction, freeze-thaw damage (i.e., the durability cannot meet the actual application requirements), which not only causes huge economic losses, but also threatens personal safety.

[0003] At present, the main measures to improve the durability of the cement-based material include: 1) improving the aggregate gradation to achieve dense packing and reduce material defects, but this method cannot completely eliminate macro defects; 2) compounding organic matters to form an organic-inorganic crosslinked network to block the transmission channel of harmful media, but the introduction of most organic matters will lead to a decrease in the strength of the cement-based material, and the organic matters are prone to aging failure; 3) using a third-party medium such as waterproof coiled material to block the contact of harmful media with the cement matrix, but this method causes greater environmental pollution, and the third-party medium is prone to aging failure.

[0004] In recent years, the research on nano-modified cement-based materials has attracted much attention. The nano-materials have small particle size and high surface activity, can provide nucleation sites to promote cement hydration and fill the pores and cracks inside the cement-based material, and part of the nano-materials have pozzolanic activity, can absorb calcium hydroxide to form hydration products in the cement hydration process, so as to improve the interface transition zone and micro-pore structure of the cement-based material, make the structure more compact, and enhance the mechanical properties and durability of the cement-based material. However, most of the nano-materials have high cost, and if used in large quantities, the production cost of the cement-based material will be greatly increased, and the particle size of the nano-materials is greatly different from the size of the internal defects of the cement-based material, so that the filling effect of the nano-materials cannot be fully played, in addition, the nano-materials often need a surfactant as a dispersant to assist dispersion, and the surfactant has air entraining effect, which is easy to introduce air holes into the cement-based material, thereby leading to a decrease in the strength of the cement-based material.

[0005] Therefore, it is of great significance to develop a cement-based material with high bending strength, low porosity and good durability. SUMMARY

[0006] The present application aims to provide a cement-based material and a preparation method and application thereof.

[0007] The technical scheme adopted by the present application is as follows:

[0008] A cement-based material comprises the following mass parts of raw materials for preparation:

[0009] Cement: 100 parts;

[0010] Quartz sand: 80-100 parts;

[0011] Nano-silica: 0.5-3.5 parts;

[0012] Polycarboxylic acid water reducer: 0.5-1.5 parts;

[0013] Dispersant: 0-1 part;

[0014] Water: 20-35 parts.

[0015] Preferably, the cement is Portland cement with a strength grade ≥ 42.5.

[0016] Preferably, the quartz sand is at least two of quartz sand with a mesh size of 26-40, quartz sand with a mesh size of 40-70, and quartz sand with a mesh size of 70-120.

[0017] Preferably, the nano-silica is one of nano-silica with a particle size of 10-20 nm and nano-silica with a particle size of 25-35 nm. Nano-silica has pozzolanic activity, and has a small size and a large specific surface area, so it has high chemical reactivity. It not only can play a physical filling effect and provide cement hydration nucleation sites, but also can quickly react with calcium hydroxide to generate hydrated calcium silicate, thereby promoting the hydration reaction of the cementitious material, densifying the microstructure of the material, and improving the performance of the cement-based material.

[0018] Preferably, the SiO2 content of the nano-silica is ≥ 99%.

[0019] Preferably, the dispersant is at least one of sodium dodecyl benzene sulfonate, polyvinyl pyrrolidone, and alkyl phenol polyoxyethylene ether. The dispersant can prevent the agglomeration of nano-silica through electrostatic and steric effects, thereby making the dispersion system have good dispersion stability.

[0020] Preferably, the number average molecular weight of the polyvinyl pyrrolidone is 40,000-70,000.

[0021] A method for preparing a cement-based material as described above comprises the following steps:

[0022] 1) mixing nano-silica, a dispersant, and part of water to perform ultrasonic dispersion to obtain a nano-silica dispersion;

[0023] 2) stirring the cement and quartz sand uniformly, adding the nano-silica dispersion liquid, adding the polycarboxylic acid water reducing agent and the remaining water while stirring, and stirring uniformly to obtain the cement mortar;

[0024] 3) pouring the cement mortar into a mold, pre-vibrating and compacting on a vibration table, vacuumizing to less than -0.1 MPa, vacuum vibrating and compacting, demolding after the cement mortar hardens, and obtaining a formed piece;

[0025] 4) performing water vapor curing and water immersion curing on the formed piece to obtain the cement-based material.

[0026] Preferably, the ultrasonic dispersion in step 1) uses an ultrasonic cell crusher.

[0027] Preferably, the ultrasonic dispersion in step 1) is performed under the condition that the output frequency of the ultrasonic cell crusher is 20 kHz and the ultrasonic power is 650 W, the ultrasonic mode is working for 5 s and stopping for 1.5 s, and the dispersion time is 30 min to 60 min. The impact wave generated by ultrasonic cavitation weakens the interaction energy between particles, so that the nano-silica is uniformly dispersed, and the nano-silica dispersion liquid with good dispersion is obtained.

[0028] Preferably, the pre-vibrating and compacting in step 3) is performed for 25 s to 35 s. The pre-vibrating and compacting helps to discharge the air holes in the cement mortar and makes the surface of the cement mortar smoother.

[0029] Preferably, the vacuum vibrating and compacting in step 3) is performed for 30 s to 600 s. The vacuum vibrating and compacting helps to discharge the remaining air holes in the cement mortar or divide the large air holes into non-continuous small air holes, and eliminates most of the macroscopic defects of the cement-based material, so as to fully utilize the physical filling effect of the nano-silica to improve the internal microscopic defects of the cement-based material.

[0030] Preferably, the water vapor curing in step 4) is performed in saturated water vapor at 80 ℃ to 90 ℃, and the curing time is 3 days to 7 days.

[0031] Preferably, the water immersion curing in step 4) is performed in water at 18 ℃ to 22 ℃, and the curing time is 25 days to 28 days.

[0032] The cement-based material as described above is applied in marine construction engineering.

[0033] The cement-based material has the advantages of high flexural strength, low porosity, good durability, and the like, and the preparation method is simple and the production cost is low, so the cement-based material can be applied in a harsh marine environment and is suitable for large-scale industrial application.

[0034] Specifically:

[0035] 1) The present application can prepare cement-based materials with high flexural strength (28d flexural strength up to 32.2MPa) and low porosity (porosity as low as 4.35%) by using vacuum vibration compaction and the crystal nucleus effect, physical filling effect and pozzolanic effect of nanomaterials, which can be applied in harsh marine environments;

[0036] 2) The present application can effectively promote the discharge of internal pores of cement-based materials by using vacuum vibration compaction forming process and providing a vacuum environment for vibration compaction process by continuous vacuum extraction during the forming process, which can significantly reduce the negative effects of air entrainment caused by dispersants;

[0037] 3) The present application can more fully exert the physical filling effect of nanomaterials on the internal pores of cement-based materials by eliminating most of the macroscopic defects in the internal pores of cement-based materials, which can improve the microstructure of cement-based materials and improve the mechanical properties and durability of cement-based materials. DETAILED DESCRIPTION

[0038] The present application will be further explained and described below in conjunction with specific examples.

[0039] Example 1:

[0040] A cement-based material, the raw material composition is shown in the following table:

[0041] Table 1 Raw material composition table of a cement-based material

[0042]

[0043]

[0044] The preparation method of the above cement-based material is as follows:

[0045] 1) Mix nanosilica and 4 / 5 of water, then use an ultrasonic cell crusher to ultrasonic disperse for 40min under the condition of output frequency of 20kHz and ultrasonic power of 650W by the mode of working for 5s and stopping for 1.5s, to obtain a nanosilica dispersion liquid;

[0046] 2) Add P.O. 42.5 Portland cement and quartz sand into a cement mixer and stir for 2min, then slowly add the nanosilica dispersion liquid while stirring, then add polycarboxylic acid water reducer and the remaining water and stir for 1min to obtain a cement mortar;

[0047] 3) After the cement mortar is injected into the mold, it is placed on a vibration table and vibrated for 30 s, left to stand for 10 min, then vacuumized to a vacuum degree less than -0.1 MPa, continuously vacuumized for 180 s, vibrated and compacted at a vibration frequency of 18 Hz and a pressure of 0.6 MPa at the same time as vacuumizing for 600 s, and then demolded after the cement mortar is hardened, to obtain a shaped piece;

[0048] 4) The shaped piece is placed in saturated water vapor at 80°C for curing for 3 days, then placed in a standard curing chamber for water immersion curing for 25 days, to obtain the cement-based material.

[0049] Example 2:

[0050] A cement-based material, the raw material composition of which is shown in the following table:

[0051] Table 2 Raw material composition table of a cement-based material

[0052]

[0053]

[0054] The preparation method of the above cement-based material is as follows:

[0055] 1) The nanosilica and 4 / 5 of the water are mixed, and then ultrasonic dispersion is performed for 50 min by using an ultrasonic cell crusher under the condition that the output frequency is 20 kHz and the ultrasonic power is 650 W, in a mode that working for 5 s and stopping for 1.5 s;

[0056] 2) The P.O. 42.5 Portland cement and quartz sand are added into a cement mixer and stirred for 2 min, then the nanosilica dispersion liquid is slowly added while stirring, and then the polycarboxylate superplasticizer and the remaining water are added and stirred for 1 min, to obtain a cement mortar;

[0057] 3) After the cement mortar is injected into the mold, it is placed on a vibration table and vibrated for 30 s, left to stand for 8 min, then vacuumized to a vacuum degree less than -0.1 MPa, continuously vacuumized for 30 s, vibrated and compacted at a vibration frequency of 24 Hz and a pressure of 0.6 MPa at the same time as vacuumizing for 60 s, and then demolded after the cement mortar is hardened, to obtain a shaped piece;

[0058] 4) The shaped piece is placed in saturated water vapor at 80°C for curing for 3 days, then placed in a standard curing chamber for water immersion curing for 25 days, to obtain the cement-based material.

[0059] Example 3:

[0060] A cement-based material, the raw material composition of which is shown in the following table:

[0061] Table 3 Raw material composition table of a cement-based material

[0062]

[0063] The preparation method of the cement-based material is as follows:

[0064] 1) Mix nano-silica, polyvinylpyrrolidone and 4 / 5 of water, and then ultrasonically disperse for 50 min by using an ultrasonic cell crusher under the condition of an output frequency of 20 kHz and an ultrasonic power of 650 W through the mode of working for 5 s and stopping for 1.5 s, to obtain a nano-silica dispersion liquid;

[0065] 2) Add P.O. 42.5 Portland cement and quartz sand into a cement mixer and stir for 2 min, then slowly add the nano-silica dispersion liquid while stirring, and then add a polycarboxylate superplasticizer and the remaining water and stir for 1 min, to obtain a cement mortar;

[0066] 3) Pour the cement mortar into a mold, place it on a vibration table, and vibrate for 30 s, and then stand for 10 min, and then continuously vacuumize for 30 s until the vacuum degree is less than -0.1 MPa, and then vibrate and compact for 60 s at a vibration frequency of 24 Hz and a pressure of 0.6 MPa while vacuumizing, and then demold after the cement mortar hardens, to obtain a shaped piece;

[0067] 4) Place the shaped piece in saturated water vapor at 80°C for 3 days, and then immerse it in a standard curing room for 25 days, to obtain the cement-based material.

[0068] Example 4:

[0069] A cement-based material, the raw material composition of which is shown in the following table:

[0070] Table 4 Raw material composition table of a cement-based material

[0071]

[0072] The preparation method of the cement-based material is as follows:

[0073] 1) Mix nano-silica, Triton X-405 and 18 / 23 of water, and then ultrasonically disperse for 60 min by using an ultrasonic cell crusher under the condition of an output frequency of 20 kHz and an ultrasonic power of 650 W through the mode of working for 5 s and stopping for 1.5 s, to obtain a nano-silica dispersion liquid;

[0074] 2) Add P.O. 42.5 Portland cement and quartz sand into a cement mixer and stir for 2 min, then slowly add the nano-silica dispersion liquid while stirring, and then add a polycarboxylate superplasticizer and the remaining water and stir for 1 min, to obtain a cement mortar;

[0075] 3) After the cement mortar is injected into the mold, it is placed on a vibration table and vibrated for 30 s, left to stand for 10 min, then vacuumized to a vacuum degree less than -0.1 MPa, continuously vacuumized for 180 s, vibrated and compacted at a vibration frequency of 18 Hz and a pressure of 0.6 MPa at the same time as vacuumizing for 600 s, and then demolded after the cement mortar is hardened, to obtain a shaped piece;

[0076] 4) The shaped piece is placed in saturated water vapor at 80°C for curing for 3 days, then placed in a standard curing chamber for water immersion curing for 25 days, to obtain the cement-based material.

[0077] Example 5:

[0078] A cement-based material, the raw material composition of which is shown in the following table:

[0079] Table 5 Raw material composition table of a cement-based material

[0080]

[0081] The preparation method of the above cement-based material is as follows:

[0082] 1) The nanosilica and 4 / 5 of the water are mixed, and then ultrasonic dispersion is performed for 50 min by using an ultrasonic cell crusher under the condition that the output frequency is 20 kHz and the ultrasonic power is 650 W, in a mode that working for 5 s and stopping for 1.5 s;

[0083] 2) The P.O. 42.5 Portland cement and quartz sand are added into a cement mixer and stirred for 2 min, then the nanosilica dispersion liquid is slowly added while stirring, and then the polycarboxylate superplasticizer and the remaining water are added and stirred for 1 min, to obtain a cement mortar;

[0084] 3) The cement mortar is injected into the mold, then placed on a vibration table and vibrated for 30 s, left to stand for 8 min, then vacuumized to a vacuum degree less than -0.1 MPa, continuously vacuumized for 30 s, vibrated and compacted at a vibration frequency of 24 Hz and a pressure of 0.6 MPa at the same time as vacuumizing for 60 s, and then demolded after the cement mortar is hardened, to obtain a shaped piece;

[0085] 4) The shaped piece is placed in saturated water vapor at 80°C for curing for 3 days, then placed in a standard curing chamber for water immersion curing for 25 days, to obtain the cement-based material.

[0086] Comparative Example 1:

[0087] A cement-based material, the raw material composition of which is shown in the following table:

[0088] Table 6 Raw material composition table of a cement-based material

[0089]

[0090] The preparation method of the cement-based material is as follows:

[0091] 1) uniformly stirring P.O. 42.5 Portland cement, quartz sand, polycarboxylate superplasticizer and water to obtain a cement mortar;

[0092] 2) after the cement mortar is injected into a mold, placing the mold on a vibration table, vibrating for 30 s, standing for 10 min, continuously vacuumizing for 180 s after vacuumizing to less than -0.1 MPa, vibrating and compacting for 600 s at a vibration frequency of 18 Hz and a pressure of 0.6 MPa at the same time of vacuumizing, demolding after the cement mortar is hardened, and obtaining a formed piece;

[0093] 3) placing the formed piece in saturated water vapor at 80℃ for 3 days, and then placing the formed piece in a standard curing room for water immersion curing for 25 days, thereby obtaining the cement-based material.

[0094] Comparative Example 2:

[0095] A cement-based material, the raw material composition of which is shown in the following table:

[0096] Table 7 Raw material composition table of a cement-based material

[0097]

[0098]

[0099] The preparation method of the cement-based material is as follows:

[0100] 1) uniformly stirring P.O. 42.5 Portland cement, quartz sand, polycarboxylate superplasticizer and water to obtain a cement mortar;

[0101] 2) after the cement mortar is injected into a mold, placing the mold on a vibration table, vibrating for 30 s, standing for 10 min, continuously vacuumizing for 180 s after vacuumizing to less than -0.1 MPa, vibrating and compacting for 600 s at a vibration frequency of 18 Hz and a pressure of 0.6 MPa at the same time of vacuumizing, demolding after the cement mortar is hardened, and obtaining a formed piece;

[0102] 3) placing the formed piece in saturated water vapor at 80℃ for 3 days, and then placing the formed piece in a standard curing room for water immersion curing for 25 days, thereby obtaining the cement-based material.

[0103] Comparative Example 3:

[0104] A cement-based material, the raw material composition of which is shown in the following table:

[0105] Table 8 Raw material composition table of a cement-based material

[0106]

[0107] The preparation method of the cement-based material is as follows:

[0108] 1) P.O. 42.5 Portland cement, quartz sand, nano-silica, polycarboxylate superplasticizer, polyvinylpyrrolidone and water were stirred uniformly to obtain a cement mortar;

[0109] 2) The cement mortar was injected into a mold and placed on a vibration table for vibration for 30 s, and after the cement mortar hardened, the mold was removed to obtain a shaped piece;

[0110] 3) The shaped piece was placed in a standard curing chamber for water immersion curing for 28 days to obtain a cement-based material.

[0111] Performance test:

[0112] The performance test data of the cement-based materials of Examples 1-5 and Comparative Examples 1-3 are shown in the following table:

[0113] Table 9 Performance test data of the cement-based materials of Examples 1-5 and Comparative Examples 1-3

[0114] Test item 28d flexural strength (MPa) Porosity (%) chloride ion migration coefficient (m 2 / s) Example 1 30.8 4.78 3.27 x 10 -12 ]]> Example 2 32.2 4.35 4.21 x 10 -12 ]] Example 3 31.0 5.16 4.71 x 10 -12 ]] Example 4 29.5 4.92 4.46 x 10 -12 ]] Example 5 27.3 6.14 5.82 x 10 -12 ]] Comparative Example 1 17.5 7.62 6.65 x 10 -12 ]]> Comparative Example 2 11.3 16.23 4.07 x 10 -11 ]] Comparative Example 3 10.7 17.12 6.11 x 10 -11 ]]

[0115] Notes:

[0116] 28d flexural strength: tested according to "JC / T 446-2000 Concrete Pavement Brick";

[0117] Porosity: after the flexural strength test, the sample was cut into a cube with a side length of 5mm-15mm, placed in a freeze dryer for freeze drying for 3 days to terminate hydration, then placed in a vacuum drying oven at 40°C for vacuum drying for 7 days, and then a mercury porosimeter of AutoPore Iv9510 type was used for porosity test;

[0118] Chloride ion migration coefficient: a dry-wet cycle method was used, a 5% NaCl solution was added to the bottom of the liquid storage tank of the dry-wet cycle box, the sample with epoxy resin brushed on the surface was dried and then moved into the dry-wet cycle test box for layering and spacing, a cycle period of 24h was set, the dry-wet cycle system was: liquid inlet for 28min, soaking for 15h, liquid extraction for 32min, air drying for 1h, drying for 6h, cooling for 1h, the solution in the water storage tank was replaced every 7 days, the free chloride ion content in the cement-based material at different erosion periods was determined by electrode method, the chloride ion content data at different depths in the cement-based material and the dry-wet cycle period were fitted to obtain the chloride ion diffusion coefficient.

[0119] From Table 9, it can be seen that:

[0120] a) The cement-based material of Comparative Example 1 has a 28d flexural strength increased by 55% compared with the cement-based material of Comparative Example 2, a porosity reduced by 53%, and a chloride ion migration coefficient reduced by 84%, indicating that the use of the vacuum vibration compaction forming process can reduce the particle spacing of the cement-based material and eliminate most of the macroscopic defects;

[0121] b) The cement-based material of Example 1 has a 76% increase in 28d flexural strength, a 37% decrease in porosity, and a 51% decrease in chloride ion migration coefficient compared to the cement-based material of Comparative Example 1, indicating that the microstructure of the cement-based material can be improved at the microscale by introducing nanomaterials on the basis of eliminating macroscopic defects through vacuum vibration compaction molding;

[0122] c) The cement-based material of Example 2 has a 185% increase in 28d flexural strength, a 73% decrease in porosity, and a 90% decrease in chloride ion migration coefficient compared to the cement-based material of Comparative Example 2, indicating that the comprehensive performance of the cement-based material is greatly improved under the combined action of the vacuum vibration compaction molding process and nanomaterial modification;

[0123] d) The cement-based material of Example 3 has a 190% increase in 28d flexural strength, a 70% decrease in porosity, and a 92% decrease in chloride ion migration coefficient compared to the cement-based material of Comparative Example 3, indicating that the negative effects caused by the air entraining effect of the dispersant can be reduced through the vacuum vibration compaction process.

[0124] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A cementitious material, characterized in that, The preparation raw materials include the following quality parts: Cement: 100 parts; Quartz sand: 80-100 parts; Nano-silica: 0.5-3.5 parts; Polycarboxylic acid water reducing agent: 0.5-1.5 parts; Dispersant: 0-1 part; Water: 20-35 parts; The nano-silica is one of nano-silica with a particle size of 10-20 nm and nano-silica with a particle size of 25-35 nm; The cement-based material is made by a preparation method including the following steps: 1) mixing nano-silica, dispersant and part of water to perform ultrasonic dispersion, to obtain a nano-silica dispersion liquid; 2) stirring cement and quartz sand uniformly, then adding the nano-silica dispersion liquid while stirring, then adding polycarboxylic acid water reducing agent and the remaining water and stirring uniformly, to obtain a cement mortar; 3) injecting the cement mortar into a mold, then placing the mold on a vibration table to perform pre-vibration compaction, then performing vacuum vibration compaction after vacuumizing to a vacuum degree less than -0.1 MPa, then demolding after the cement mortar hardens, to obtain a formed piece; 4) performing water vapor curing and water immersion curing on the formed piece, to obtain the cement-based material.

2. The cementitious material of claim 1, wherein: The cement is portland cement with a strength grade ≥42.

5.

3. Cementitious material according to claim 1 or 2, characterized in that: The quartz sand is at least two of quartz sand with a mesh size of 26-40, quartz sand with a mesh size of 40-70 and quartz sand with a mesh size of 70-120.

4. Cementitious material according to claim 1 or 2, characterized in that: The dispersant is at least one of sodium dodecyl benzene sulfonate, polyvinyl pyrrolidone and alkyl phenol polyoxyethylene ether.

5. The cementitious material of claim 1, wherein: The ultrasonic dispersion in step 1) is performed by using an ultrasonic cell crusher.

6. Cementitious material according to claim 1 or 2, characterized in that: The time for the pre-vibration compaction in step 3) is 25-35 s; and the time for the vacuum vibration compaction in step 3) is 30-600 s.

7. Cementitious material according to claim 1 or 2, characterized in that: The water vapor curing in step 4) is performed in saturated water vapor at 80-90℃, and the curing time is 3-7 days; and the water immersion curing in step 4) is performed in water at 18-22℃, and the curing time is 25-28 days.

8. Application of the cement-based material according to any one of claims 1-7 in marine construction engineering.

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