CN113213855B

CN113213855B - Anti-freezing cement-based material, preparation method and application thereof

Info

Publication number: CN113213855B
Application number: CN202110723766.2A
Authority: CN
Inventors: 赖远明; 曾红燕
Original assignee: Northwest Institute of Eco Environment and Resources of CAS
Current assignee: Northwest Institute of Eco Environment and Resources of CAS
Priority date: 2021-06-29
Filing date: 2021-06-29
Publication date: 2022-11-22
Anticipated expiration: 2041-06-29
Also published as: CN113213855A

Abstract

The invention discloses an anti-freezing cement-based material, a preparation method and application thereof, and relates to the technical field of concrete. The anti-freezing cement-based material comprises the following raw materials: 100 parts of cement, 200-400 parts of sand, 0.03-0.07 part of graphene oxide and 1-4 parts of sodium dodecyl benzene sulfonate. By optimizing the raw materials of the cement-based material, introducing the graphene oxide and the sodium dodecyl benzene sulfonate on the basis of cement and sand and controlling the proportion of the raw materials, the cement-based material not only has good frost resistance, but also has excellent mechanical properties.

Description

Anti-freezing cement-based material, preparation method and application thereof

Technical Field

The invention relates to the technical field of concrete, in particular to an anti-freezing cement-based material, and a preparation method and application thereof.

Background

In northern cold regions, the temperature in winter often reaches twenty degrees below zero, even up to four or fifty degrees below zero. In such places, higher requirements are put on the anti-freezing performance of the building engineering, especially on roads, bridges and the like, and concrete of the building engineering needs to resist ultralow temperature for a long time on one hand and is subjected to repeated freezing and thawing tests on the other hand. In order to meet the requirements in the aspect, the industry provides concepts and requirements of the frost-resistant concrete, and the frost-resistant concrete refers to the structural design requirement that the concrete has the durability for resisting freeze-thaw cycles for a long time, namely, meets the frost-resistant grade specified by the structural design.

At present, the commonly used methods for improving the frost resistance of concrete mainly include the following four methods: increasing ice crystal growth space (e.g. adding air entraining agent), reducing porosity (e.g. adding filler or using pozzolan cement), inhibiting microcrack growth (e.g. adding short fiber and various nanomaterials), and retarding water penetration (e.g. adding hydrophobic agent). Among these methods, an air entraining agent, which is widely used for the first time and is known to be effective, is an admixture capable of introducing a large number of uniformly distributed, stable and closed fine air bubbles into concrete during the stirring process, thereby improving the durability of the concrete.

A large number of experimental researches show that when the content of the bubbles is 5-6%, the frost resistance of the cement-based material is improved most remarkably by the air entraining agent. However, the air entraining agent introduces these micro-bubbles like balls, which reduces the frictional resistance between the materials and also reduces the effective area of the slurry, resulting in a significant reduction in the strength of the concrete. Research shows that when the air content of the concrete is increased by 1%, the compressive strength is reduced by about 4-6%, and the flexural strength is reduced by about 2-3%. Although theoretically, if the diameter of the air bubbles introduced by the air entraining agent is controlled within the range of 20 μm to 200 μm, the frost resistance of the cement-based material can be improved and the structural strength can be ensured, it is difficult to control the air bubbles completely within such a good diameter range in practice.

Therefore, how to win both the mechanical property and the freezing resistance of the final concrete is a technical problem which needs to be solved urgently.

Disclosure of Invention

The invention aims to provide an anti-freezing cement-based material and a preparation method thereof, and aims to simultaneously improve the mechanical property and the freezing resistance of the material.

The invention also aims to provide application of the anti-freezing cement-based material in preparation of anti-freezing concrete buildings.

The invention is realized by the following steps:

in a first aspect, the invention provides an anti-freezing cement-based material, which comprises the following raw materials in parts by weight: 100 parts of cement, 200-400 parts of sand, 0.03-0.07 part of graphene oxide and 1-4 parts of sodium dodecyl benzene sulfonate.

In a second aspect, the present invention provides a method for preparing the above frost resistant cement-based material according to the above embodiments, wherein the method is carried out by using the above raw materials of the frost resistant cement-based material.

In a third aspect, the present invention provides the use of a frost resistant cementitious material as described in the previous embodiments or as prepared by a method as described in the previous embodiments, in the preparation of a frost resistant concrete building.

The invention has the following beneficial effects: by optimizing the raw materials of the cement-based material, introducing the graphene oxide and the sodium dodecyl benzene sulfonate on the basis of cement and sand and controlling the proportion of the raw materials, the inventor finds that: the cement-based material not only has good frost resistance, but also has excellent mechanical properties.

It needs to be explained that how to make cement-based materials have excellent frost resistance and simultaneously ensure good mechanical properties is a great problem which has plagued the field for a long time. The inventor creatively utilizes the matching of graphene oxide and sodium dodecyl benzene sulfonate, and the sodium dodecyl benzene sulfonate not only plays a role of an air entraining agent to improve the frost resistance, but also can improve the dispersibility of the graphene oxide, thereby being beneficial to further improving the mechanical property.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a graph of intensity reduction factor versus number of freeze-thaw cycles;

FIG. 2 is a topography of different sample hydrated crystals;

FIG. 3 is a micro-crack test chart of different samples under an electron microscope;

FIG. 4 is a comparative photograph of a GO dispersion sample after resting for 2 hours;

FIG. 5 is a comparative photograph of a GO dispersion sample after standing for 2 days;

FIG. 6 is a comparative photograph of a GO dispersion sample after resting for 2 weeks;

FIG. 7 shows the results of UV-Vis spectral analysis.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The embodiment of the invention provides an anti-freezing cement-based material which comprises the following raw materials in parts by weight: 100 parts of cement, 200-400 parts of sand, 0.03-0.07 part of graphene oxide and 1-4 parts of sodium dodecyl benzene sulfonate.

The inventor creatively introduces the graphene oxide and the sodium dodecyl benzene sulfonate, and the mechanical property and the durability of the cement-based material are obviously improved. The sodium dodecyl benzene sulfonate not only plays a role of an air entraining agent, but also can improve the dispersibility of the graphene oxide, and is beneficial to further improving the mechanical property.

Additionally, the inventors found that the use of graphene oxide enables the material to have superior mechanical properties and durability compared to graphene, which may be due to: although both of the two-dimensional carbon nanomaterials are two-dimensional carbon nanomaterials, graphene oxide has a special sheet structure, high strength and large specific surface area, and contains a large number of oxygen-containing functional groups on the surface, and the existence of the groups enables the graphene oxide to have better water solubility than graphene.

The cement mortar used in the embodiment of the invention is gas-containing cement mortar, and the main component of the used air entraining agent is sodium dodecyl benzene sulfonate, so that the frost resistance of the material can be improved. However, the mechanical property of concrete can be weakened by adding the air entraining agent, and the inventor achieves the purpose of obviously improving the mechanical property by introducing the matching of the graphene oxide and the sodium dodecyl benzene sulfonate, thereby realizing the win-win of the mechanical property and the freezing resistance. Compared with the case of independently introducing graphene oxide, the mechanical property can be further improved by using the cooperation of the graphene oxide and sodium dodecyl benzene sulfonate, and the technical effect exceeds the expectation of the technical personnel in the field.

In order to further improve the mechanical property and the freezing resistance of the material, the inventor further optimizes the dosage of the raw materials: the raw materials comprise the following components in parts by weight: 100 parts of cement, 280-320 parts of sand, 0.03-0.05 part of graphene oxide and 2.0-3.0 parts of sodium dodecyl benzene sulfonate.

The use amount of the graphene oxide is too small, so that the control is difficult, and the improvement of the mechanical property is not obvious; the use amount of the graphene oxide is too large, the mechanical property is not further improved, and the production cost is obviously improved.

Specifically, graphene oxide is a commercially available material, and the thickness of the graphene oxide can be 0.5-2nm, and the diameter of the graphene oxide is approximately 10-50 μm, and generally, commercially available graphene oxide can be used in the embodiments of the present invention.

In some embodiments, the cement is portland cement, which is readily available and widely used. In other embodiments, the cement can be other types which need to be hydrated and formed, and the anti-freezing performance and the mechanical property can be improved by adopting the formula composition in the embodiment of the invention.

In some embodiments, the sand is washed medium sand, and the raw material of the anti-freezing cement-based material further comprises 0.6-1.0 part of a water reducing agent; the water reducing agent can be a polycarboxylic acid water reducing agent. The washed middlings are adopted as raw materials and need to be matched with a water reducing agent, and the type of the water reducing agent can not be limited to a polycarboxylic acid water reducing agent.

In other embodiments, the sand may also be fine sand, in which case the water reducing agent may also not be introduced according to the prior art.

The embodiment of the invention also provides a preparation method of the antifreezing cement-based material, which is characterized in that the antifreezing cement-based material is prepared from the raw materials, and the materials are mixed by adopting a conventional mixing mode.

In order to further improve the performance of the material, the inventor further optimizes the mixing sequence of the raw materials: mixing graphene oxide, sodium dodecyl benzene sulfonate and water to obtain a first dispersion liquid; the cement, sand and the first dispersion are then mixed. Firstly, the graphene oxide and sodium dodecyl benzene sulfonate are mixed to prepare a form of dispersion liquid, which is beneficial to improving the dispersion performance of the graphene oxide in materials.

Specifically, in the first dispersion liquid, the mass concentration of the graphene oxide is 0.5-2g/L (such as 0.5g/L, 1g/L, 1.5g/L, 2.0 g/L), and the mass concentration of the sodium dodecyl benzene sulfonate is 50-60g/L (50 g/L, 55g/L, 60 g/L). The concentrations of the graphene oxide and the sodium dodecylbenzene sulfonate in the first dispersion liquid can be not limited to the above ranges, and the raw materials can be uniformly mixed.

Further, the preparation process of the first dispersion comprises: mixing and stirring graphene oxide, sodium dodecyl benzene sulfonate and water, then carrying out ultrasonic treatment for 15-25min, and cooling to room temperature. The mode of adopting ultrasonic treatment can guarantee the homogeneity that the oxidation graphite alkene mixes to improve its dispersion effect, can shorten the compounding time moreover. After ultrasonic treatment, the temperature of the material is approximately raised to over 70 ℃, and the material is mixed with cement after being cooled so as to avoid influencing the cement forming effect.

It needs to be supplemented that, in order to achieve the anti-freezing effect in the prior art, before a concrete sample is prepared, modified graphene composite intercalated oil shale needs to be prepared, and the process control is complex, the consumed time is long, and the engineering practical construction is not facilitated. The time required by the embodiment of the invention is obviously reduced, and the graphene oxide aqueous dispersion is prepared for later use only by using an ultrasonic dispersion instrument. Therefore, the material preparation process provided by the embodiment of the invention only needs about 60min, and has few influencing factors and strong result controllability.

In some embodiments, the ultrasonic working time in one cycle is controlled to be 9-11s (e.g., 9s, 10s, 11s, etc.) and the gap time is controlled to be 1.5-2.5s (e.g., 1.5s, 2.0s, 2.5s, etc.) during the ultrasonic treatment. For example, the ultrasound operation time may be 10s in one cycle, and the next cycle is entered after 2s interval.

In order to increase the uniformity of the mixed materials, cement and sand are mixed to obtain a first mixed material, the first dispersion liquid and the water reducing agent are added into the first mixed material for multiple times, and the mixture is uniformly stirred to obtain a second mixed material.

The total amount of water is adjusted according to the conventional technical means in the mixing process so as to control the water-cement ratio to be 0.4-0.5.

In some embodiments, the method further comprises shaping and curing the second mixed material to obtain the concrete material. It should be noted that the forming and curing can be performed by the existing means, and belongs to the optional step.

The embodiment of the invention also provides application of the antifreeze type cement-based material or the antifreeze type cement-based material prepared by the preparation method in preparation of an antifreeze type concrete building.

The features and properties of the present invention are described in further detail below with reference to examples.

It should be noted that the properties of the graphene oxide used in the following examples are as follows: purity 95% and density 2.1g/cm ³ 1 to 2 layers, about 1nm thickness and 10 to 5 diameters0 μm. In the following examples, the composition of the rinsing sands used is shown in table 1:

TABLE 1 grading of washed sands

Mesh size (mm)	4.75	2.36	1.18	0.6	0.3	0.15
							Cumulative screen residue (%)	0	20	36	48	86	100

Example 1

The embodiment of the invention provides a preparation method of an anti-freezing cement-based material, which comprises the following steps:

(1) Preparation of graphene oxide Dispersion

Weighing 0.03 part of graphene oxide, 2.5 parts of sodium dodecyl benzene sulfonate powder and a certain amount of water (controlling the mass concentration of the graphene oxide to be about 0.67 g/L); respectively pouring graphene oxide and sodium dodecyl benzene sulfonate into water, and stirring for 3min by using a stirring rod; immediately placing the sample in an ultrasonic dispersion instrument for dispersion, wherein the working time of the dispersion instrument is 10s, the gap time is 2s, and the whole process time is 20min; after dispersion, the dispersion was allowed to stand naturally, and the solution was cooled to room temperature.

(2) Preparation of high freezing resistance gas-containing cement-based material sample

Weighing 100 parts of portland cement, 300 parts of sand in water washing and 0.8 part of high-efficiency polycarboxylic acid water reducing agent according to the proportion, and controlling the water-cement ratio to be 0.45, the sand-cement ratio to be 1:3 and the using amount of the water reducing agent to be 0.8 percent (accounting for 0.8 percent of the total amount of the cement) according to the amount of water taken.

The method comprises the steps of mixing cement and sand to obtain a first mixed material, pouring cooled graphene oxide dispersion liquid and a water reducing agent into the first mixed material in batches, and stirring continuously to enable the mixture to be as uniform as possible.

Example 2

(1) Preparation of graphene oxide Dispersion

Weighing 0.07 part of graphene oxide, 3.5 parts of sodium dodecyl benzene sulfonate powder and a certain amount of water (controlling the mass concentration of the graphene oxide to be about 1.6 g/L); respectively pouring graphene oxide and sodium dodecyl benzene sulfonate into water, and stirring for 3min by using a stirring rod; then immediately placing the sample in an ultrasonic dispersion instrument for dispersion, wherein the working time of the dispersion instrument is 9s, the gap time is 1.5s, and the whole process time is 25min; after dispersion, the dispersion was allowed to stand naturally, and the solution was cooled to room temperature.

(2) Preparation of high frost resistance gas-containing cement-based material sample

Weighing 100 parts of portland cement, 200 parts of sand in water washing and 0.6 part of high-efficiency polycarboxylic acid water reducing agent according to the proportion, and controlling the water-cement ratio to be 0.45, the sand-cement ratio to be 1:2 and the using amount of the water reducing agent to be 0.6 percent (accounting for 0.6 percent of the total amount of the cement) according to the amount of water taken.

Example 3

(1) Preparation of graphene oxide Dispersion

Weighing 0.05 part of graphene oxide, 3 parts of sodium dodecyl benzene sulfonate powder and a certain amount of water (controlling the mass concentration of the graphene oxide to be about 1.1 g/L); respectively pouring graphene oxide and sodium dodecyl benzene sulfonate into water, and stirring for 3min by using a stirring rod; then immediately placing the sample in an ultrasonic dispersion instrument for dispersion, wherein the working time of the dispersion instrument is 11s, the gap time is 2.5s, and the whole process time is 15min; after dispersion, the dispersion was allowed to stand naturally, and the solution was cooled to room temperature.

Weighing 100 parts of portland cement, 400 parts of sand in water washing and 1.0 part of high-efficiency polycarboxylic acid water reducing agent according to the proportion, and controlling the water-cement ratio to be 0.45, the sand-cement ratio to be 1:4 and the using amount of the water reducing agent to be 1.0 percent (accounting for 1.0 percent of the total amount of the cement) according to the amount of water taken.

Comparative example 1

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: and adding no graphene oxide and sodium dodecyl benzene sulfonate powder to obtain the cement-based material M00.

Comparative example 2

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: and adding 2 parts of sodium dodecyl benzene sulfonate powder without adding graphene oxide to obtain the cement-based material MAE-1.

Comparative example 3

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: and adding 2.5 parts of sodium dodecyl benzene sulfonate powder without adding graphene oxide to obtain the cement-based material MAE-2.

Comparative example 4

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: and (3) adding 3 parts of sodium dodecyl benzene sulfonate powder without adding graphene oxide to obtain the cement-based material MAE-3.

Comparative example 5

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: and the addition of the graphene oxide is 0.01 part, and sodium dodecyl benzene sulfonate powder is not added to obtain the cement-based material MGO-1.

Comparative example 6

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: the addition amount of the graphene oxide is 0.03 part, and sodium dodecyl benzene sulfonate powder is not added to obtain the cement-based material MGO-2.

Comparative example 7

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: the addition of the graphene oxide is 0.05 part, and sodium dodecyl benzene sulfonate powder is not added, so that the cement-based material MGO-3 is obtained.

Comparative example 8

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: the addition amount of the graphene oxide is 0.01 part, and the addition amount of the sodium dodecyl benzene sulfonate powder is 2.5 parts, so that the cement-based material MAG-1 is obtained.

Note: the cement-based material obtained in example 1 is designated MAG-2

Comparative example 9

This comparative example provides a method for the preparation of a cement-based material, differing from example 1 only in that: the addition amount of the graphene oxide is 0.05 part, and the addition amount of the sodium dodecyl benzene sulfonate powder is 2.5 parts, so that the cement-based material MAG-3 is obtained.

Test example 1

The cement-based materials of example 1 and comparative examples 1 to 9 were molded and cured, and the resulting materials were subjected to mortar freezing resistance tests to test mechanical properties and freezing resistance, with the results shown in table 2.

And (3) forming and maintaining processes: pouring the mixed slurry into a prepared mould, integrally placing the mould on a vibration table for 10s, and scraping redundant leftover materials by using a spatula; after the sample is preliminarily molded, the sample is immediately placed in a curing room with the temperature of 25 ℃ and the humidity of 98 percent, and curing is continued for 28 days.

Mortar freezing resistance test: according to the regulation of JGJ T70-2010, the sample is taken out from the curing chamber after being cured for 24 days, and is continuously soaked in clear water for 4 days; after the soaking is finished, immediately performing appearance inspection to record the original condition of the soaked object, and measuring the initial quality and the 28-day compressive strength; then, putting the residual water-saturated sample into a sample barrel of a freeze-thaw circulator, adding water until the water completely submerges the sample, setting the circulating temperature between 20 ℃ and-18 ℃, wherein each circulation needs to be completed within 8h, the time for thawing is not less than 1/4 of the whole freeze-thaw time, and the conversion time between freezing and thawing is not more than 10min; the experiment was suspended every 50 cycles, visual inspection was performed, and the mass and compressive strength were measured simultaneously until the experiment was stopped after 300 cycles. When the compressive strength of the test piece was measured using a universal tester, the loading rate was set to 1.5kN/s. Taking 300 freeze-thaw cycles as an example, the mechanical properties and frost resistance results (compared to the plain mortar) are shown in table 2.

The plain mortar refers to mortar prepared by using the cement, the sand and the water reducing agent in example 1 as a comparative object without adding graphene oxide and sodium dodecyl benzene sulfonate.

Note: because the concrete is quick in strength degradation after being frozen and cannot completely reflect frost resistance only by the residual strength, the national standard provides a concept of strength reduction coefficient to measure the frost resistance of the cement-based material, and the strength reduction coefficient refers to the ratio of the residual compressive strength to the initial compressive strength, so the unit is 1.

TABLE 2 mechanical Properties and Freeze resistance test results

From the experimental results in table 2, it can be seen that although the air entraining agent can significantly improve the frost resistance of the cement material, the compressive strength is reduced by 11.1%, and a small amount (0.03%) of graphene oxide not only improves the frost resistance durability of the gas-containing cement-based material by 115.7%, but also improves the compressive strength by 41.9%, which indicates that the graphene oxide can significantly improve the frost resistance and solve the problem of strength reduction of the gas-containing concrete.

Because the initial strength of the adopted samples is different, and the mechanical strength after degradation is directly compared, the frost resistance of each sample cannot be accurately reflected, the following method is adopted to test the frost resistance improvement rate in the national standard:

the national standard stipulates that when the strength loss exceeds 25%, the concrete loses frost resistance, and the strength reduction coefficient is 0.75. The strength reduction factors for M00 (plain mortar), MGO-2 (containing 0.03% GO), MAE-2 (containing 2.5% AE), and MAG-2 (containing both 0.03% GO and 2.5% AE) are presented in FIG. 1.

It can be seen that when the strength reduction factor is 0.75, the number of freeze-thaw cycles of the corresponding sample is 127 times, 151 times, 243 times and 274 times, i.e. 0.03% of GO can only improve the frost resistance durability of the plain mortar by 18.9%, 2.5% of AE can improve the frost resistance of the plain mortar by 91.3%, and when both are present, the frost resistance of the plain mortar can be improved by 115.7%. The specification shows that both GO and AE can improve the frost resistance of cement mortar, but compared with an air entraining agent, GO is not obviously improved in frost resistance, but when the GO and the air entraining agent are added simultaneously, the frost resistance can be greatly improved, not only is the effect of the air entraining agent, but also the dispersity of GO is obviously improved due to the addition of the air entraining agent, and thus the frost resistance of the cement-based material is obviously improved.

Test example 2

The mortar prepared from the ingredients in Table 3 was cured by the method of test example 1, and then subjected to scanning electron microscope test, and the results are shown in FIGS. 2 to 3.

TABLE 3 sample formulation

Sample name	Water cement ratio	Ratio of ash to sand	Doping amount of graphene oxide	Mixing amount of water reducing agent
					M00	0.45	1:3	-	0.70
M12	0.45	1:3	0.01％	0.8％
					M14	0.45	1:3	0.03％	0.8％
M16	0.45	1:3	0.05％	0.8％

In fig. 2 and 3, (a) represents M00, (b) represents M12, (c) represents M14, and (d) represents M16.

The morphology of the hydrated product can be clearly seen by using a high power electron microscope, and as can be seen from fig. 2, a large number of irregular flocculent hydrated crystals are arranged in the plain mortar (fig. 2 (a)), while under the same magnification, the morphology of the hydrated calcium silicate crystals in the other three electron microscope pictures of fig. 2 is more regular, as in a flower, which indicates that the graphene oxide can change the morphology of the hydrated crystals to form a more uniform and compact microstructure.

Fig. 3 shows electron microscope pictures of micro cracks in the plain mortar and the graphene oxide modified mortar, and as cement is subjected to effects such as shrinkage during hydration, some micro cracks are inevitably generated as shown in fig. 3 (a), which provides a smooth path for transmission of water or ions. However, only a small number of short cracks can be found in the graphene oxide-modified cement material, as shown in fig. 3 (b) - (d). The result shows that the existence of the graphene oxide can effectively inhibit the propagation of microcracks, and the generation of a large number of short cracks can improve the tortuosity of the structure, so that the transmission characteristic of the cement-based material can be reduced.

In general, compared with the traditional nano additive, the graphene oxide nano sheet has a unique two-dimensional carbon nano structure and a larger specific surface area, so that the growth of microcracks can be more easily inhibited on a nano scale, the hydration reaction process can be promoted, and the microstructure and the spatial position of a hydrated crystal can be optimized.

According to the analysis, the graphene oxide enables the appearance of the hydrated crystal to be more regular by adjusting the hydration reaction of cement, and can also inhibit microcracks and enable the microstructure to be more compact, so that the addition of the graphene oxide can prevent water from entering the matrix, and the frost resistance of the cement-based material is improved. This explains to a certain extent why the addition of graphene oxide can improve the freezing resistance on the premise of improving the mechanical properties.

Although all the samples do not contain an air entraining agent (sodium dodecyl benzene sulfonate), the electron microscope results can independently prove the micro-modification effect of the graphene oxide on the cement matrix, and the graphene oxide can improve the microstructure and does not sacrifice the mechanical property when the frost resistance is improved.

Test example 3

The influence of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate on the dispersion performance of graphene oxide is explored:

1. procedure of experiment

In order to study the influence of the type and the doping amount of the air entraining agent on the GO dispersity, a dispersity test is firstly carried out before preparing a modified mortar sample. When the dispersion liquid is prepared, the mass concentration of GO is fixed at 1.1g/L, and the mass concentration of SDBS (or SDS) is three, namely 0.22g/L, 1.1g/L and 2.2g/L. The specific procedure of the dispersion test is as follows: weighing a certain amount of GO, water and SDBS (or SDS) powder; respectively pouring GO and SDBS (or SDS) powder into water, and stirring for 3min by using a stirring rod; then immediately placing the sample in an ultrasonic dispersion instrument for dispersion, wherein the working time of the dispersion instrument is 10s, the gap time is 2s, and the whole process time is 20min; immediately after the end of the dispersion, the conductivity and temperature of the solution were measured with a conductivity pen. According to different types, mixing amounts and dispersing means of the added air entraining agents, 10 GO dispersion liquid comparison samples are manufactured in the test, and specific information of each sample is shown in table 4.

TABLE 4 configuration information and physical Properties of GO Dispersion

2. Results of the experiment

The method is one of important ways for ensuring the performance improvement effect of GO on cement-based materials, and the influence of alkyl sulfonate on the GO dispersibility is represented by conductivity, UV-visible spectrum analysis and the stability of a dispersion liquid, so that the type of an air entraining agent used in the frost resistance test in this chapter is determined according to the influence.

(1) Effect of dispersant on conductivity

From the results of the tests, table 4 lists the solution temperature and conductivity at the end of the dispersion, it can be seen that the temperature of the solution after manual stirring is between about 12 ℃ and 16 ℃, and the solution temperature rises sharply by ultrasonic treatment, about 72 ℃, so that when making a mortar sample, GO dispersion is mixed with cement sand after it has cooled to 25 ℃ to prevent the temperature from being too high and affecting the cement hydration reaction.

Comparing the conductivity results of the UV-1 to UV-4 samples, it can be seen that the conductivity of the dispersion increases significantly with increasing concentration of SDBS, while their temperatures are almost the same, all around 72 ℃, and similar conclusions (compare UV-6 to UV-8) also apply when the solute is SDS, indicating that the concentration of solute has a significant effect on conductivity and a minor effect on temperature, which is consistent with previous findings.

In fact, comparing the temperatures of all samples, it can be found that the temperature of the untreated clean water is 12.6 ℃, the temperature after manual stirring is 12.9 ℃, which is due to the effect of manual stirring work and room temperature, and the temperature after ultrasonic dispersion reaches 72 ℃, which shows that the temperature is only related to the dispersion mode, but not to the solution concentration and solute type. In addition, when the solution concentration is the same, the solution conductivity is lower when adding SDBS than when adding SDS, for example, the conductivity of UV-3 (containing 1.1g/L GO and 2.2g/L SDBS) is 1.38mS/cm, and the conductivity of UV-8 (containing 1.1g/L GO and 2.2g/L SDS) is 1.52mS/cm, because the conductivity has a certain relation with the amount of electrolyte, and the concentration of ions in a certain concentration range is larger, the more the charge is, the larger the conductivity is, therefore, the alkyl sulfonate containing benzene ring has higher steric hindrance, and the sheet aggregation of GO in the aqueous solution can be reduced to the greatest extent.

(2) Stability of GO dispersions

Fig. 4-6 show comparative photographs of these 10 GO dispersion samples after resting for 2 hours, 2 days, and 2 weeks, respectively.

Observing the solutions of UV-3 and UV-4 can find that the solution without ultrasonic treatment (UV-4) begins to generate flocculent precipitate or obvious layering phenomenon after standing for a period of time, and the layering or precipitation phenomenon becomes more and more obvious along with the increase of the standing time, while the sample after ultrasonic treatment (UV-3) still keeps uniform black after standing for 2 weeks, turbidity or agglomeration phenomenon is not observed by naked eyes, and meanwhile, the samples of UV-8 and UV-9 also have similar phenomena, which shows that the ultrasonic wave has very obvious effect on improving the dispersity of GO in water.

The degree of precipitation or delamination was more significant for the UV-0 sample than for the UV-1-3 (or UV-6-8) samples at the same standing time. Comparing all the photographs of the dispersions containing the alkylsulfonate, it can be seen that, in addition to the samples UV-2 to 4 and UV-7 to 8, the samples were found to show different degrees of flocculation and demixing after being left for 2 hours, and it is noted that the samples UV-4 and UV-7 showed demixing after being left for 2 days, and the samples UV-2 and UV-8 showed demixing until 2 weeks, and the sedimentation rate of the sample UV-2 was significantly higher than that of the sample UV-8, while the sample UV-3 did not show any demixing or sedimentation during the whole test, indicating that the dispersibility of the sample UV-3 was the most stable among all the samples, but no flocs visible to the naked eye appeared, and no change in dispersibility was represented, and the dispersibility of the solution was quantified by means of UV-Vis spectroscopy.

(3) UV-Vis spectral analysis

In order to quantitatively characterize the effect of SDS, SDBS and ultrasonics on the dispersibility of GO in aqueous GO solution, after initial dispersion and standing for 2 days, the supernatants of samples UV-0, UV-3, UV-4, UV-5, UV-8 and UV-9 were taken, and the absorbance of the solution under UV-visible light was measured using deionized water as a control, as shown in FIG. 7, wherein the dispersion treatment means for the left column of samples (in turn UV-0, UV-3 and UV-8) were all ultrasonicated, the dispersion means for the right column of samples (in turn UV-5, UV-4 and UV-9) were all stirred manually, and the difference between the rows in FIG. 7 is that no dispersant (UV-0 and UV-5), SDBS (UV-3 and UV-4) and SDS (UV-8 and UV-9) were added, respectively.

Comparing the absorbances of the UV-0 and UV-5 samples, it can be seen that the dispersibility of the GO aqueous solution can be improved briefly by ultrasonic treatment without the aid of a dispersing agent, but after standing for 2 days, the absorbances of the two samples are almost consistent, and the light absorption intensity of the visible light part approaches zero, indicating that the supernatant at this time is almost close to deionized water. The samples UV-3, UV-4, UV-8 and UV-9 show very different absorption properties compared to the samples UV-5 and UV-0, especially the absorbance in the visible part (wavelength. Gtoreq.400 nm), with significant fluctuations. It is however noted that UV-4, UV-8 and UV-9 show a sharp decrease in the absorption intensity after 2 days of standing at wavelengths of visible light above 500nm, 650nm and 400nm, respectively (compared to the initial time), whereas the absorbance curves of UV-3 at the initial time and after 2 days of standing almost completely coincide, which means that the dispersion performance of sample No. UV-3 is best and most stable in all samples, and SDBS acts as a dispersant for aqueous GO solution, which has a better dispersion effect than SDS.

Because the closed bubbles which are uniformly distributed and have good stability have great significance for improving the frost resistance of the cement-based material, the air entraining agent mixed liquid selected by the freeze-thaw test is mainly composed of sodium dodecyl benzene sulfonate by integrating the analysis.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The anti-freezing cement-based material is characterized by comprising the following raw materials in parts by weight: 100 parts of cement, 200-400 parts of sand, 0.03-0.07 part of graphene oxide and 1-4 parts of sodium dodecyl benzene sulfonate;

the preparation method of the anti-freezing cement-based material comprises the following steps: mixing and stirring the graphene oxide, the sodium dodecyl benzene sulfonate and water, then carrying out ultrasonic treatment for 15-25min, and cooling to room temperature to obtain a first dispersion liquid; mixing cement, sand and the first dispersion.

2. The antifreeze cement-based material of claim 1, wherein the antifreeze cement-based material comprises the following raw materials in parts by weight: 100 parts of cement, 280-320 parts of sand, 0.03-0.05 part of graphene oxide and 2.0-3.0 parts of sodium dodecyl benzene sulfonate.

3. Anti-freeze based material according to claim 1 or 2, wherein the cement is portland cement.

4. Antifreeze cement-based material according to claim 1 or 2, wherein the sand is washed medium sand, and the raw material of the antifreeze cement-based material further comprises 0.6 to 1.0 part of a water reducing agent.

5. The frost-resistant cementitious material of claim 4, wherein the water reducer is a polycarboxylic acid water reducer.

6. Anti-freeze cement-based material according to claim 1, wherein during the sonication process, the sonication working time is controlled to be 9-11s and the gap time is controlled to be 1.5-2.5s in one cycle.

7. The frost-resistant cementitious material of claim 4, wherein the cement is mixed with sand to form a first mixture, the first dispersion and the water reducing agent are added to the first mixture in multiple portions, and the mixture is stirred to form a second mixture.

8. Anti-freeze cement-based material according to claim 7, characterised in that the total amount of water used is adjusted during mixing to control the water cement ratio between 0.4 and 0.5.

9. The freeze resistant cementitious-based material of claim 7, further comprising forming and curing the second admixture.

10. Use of a frost resistant cementitious material according to any of claims 1 to 9 in the production of a frost resistant concrete building.