CN116143428B - A cementitious material containing recycled brick powder and cement-based material - Google Patents

Abstract

The invention relates to a cementitious material and a cement-based material containing recycled brick powder. The cementitious material comprises cement and recycled brick powder. The cement content is 70%-100% by weight. The recycled brick powder content is 0%-30%. The preparation method of the recycled brick powder comprises the following steps: step 1, preparing waste brick powder; step 2, activating: heating the waste brick powder to a temperature T, subjecting the waste brick powder to a constant temperature treatment for 2-8 hours, then cooling the waste brick powder to room temperature, and sieving the waste brick powder. The temperature T is 100-1000° C. The invention not only reduces the amount of cement in the cementitious material, but also provides a new application path for the reuse of waste brick powder, thereby expanding the application scope of the recycled brick powder.

Description

A cementitious material containing recycled brick powder and cement-based material

Technical Field

The invention belongs to the technical field of cement-based materials, and particularly relates to a preparation method and application of recycled brick powder.

Background technique

Cementitious materials, also known as binders, can be transformed from slurry into a solid stone-like body under physical and chemical effects, and can bind other materials to form a composite solid substance with a certain mechanical strength. As an important cementitious material, cement is widely used in civil engineering, water conservancy, national defense and other projects; however, in recent years, with the continuous development of civil engineering, the demand for cement has increased, and it often faces a situation of supply exceeding demand.

Recycled brick powder is usually made from construction waste bricks through crushing and grinding. Its main components are SiO ₂ and Al ₂ O ₃ , and it has volcanic ash activity similar to fly ash and slag. At present, its recycling is usually to add it as an aggregate admixture into concrete. However, its use as an admixture is limited. At present, a large number of buildings have reached the end of their service life, and there is still a large amount of brick solid waste.

Therefore, developing a cementitious material containing recycled brick powder is particularly important for saving cement, developing new application methods of recycled brick powder, and expanding the application scope of recycled brick powder.

Summary of the invention

The purpose of the present invention is to overcome the defects in the prior art and provide a cementitious material and a cement-based material containing recycled brick powder. The recycled brick powder is used to replace part of the cement as the cementitious material, which not only reduces the amount of cement in the cementitious material, but also provides a new application path for the reuse of waste brick powder, thereby expanding the application scope of the recycled brick powder.

To achieve the above purpose, the technical solution adopted by the present invention is as follows:

Technical solution 1:

A cementitious material containing recycled brick powder comprises cement and recycled brick powder; in terms of weight percentage, the percentage of cement is 70%-100%; the percentage of recycled brick powder is 0%-30%.

As a preferred technical solution, the percentage of cement is 70%-90%; the percentage of recycled brick powder is 10%-30%.

As a preferred technical solution, the method for preparing the recycled brick powder comprises the following steps:

Step 1, preparation of waste brick powder;

Step 2, activation: after heating the waste brick powder to a temperature T, keep the temperature constant for 2h-8h, then cool it to room temperature, sieve it, and obtain the waste brick powder; the temperature T is 100℃-1000℃;

As a preferred technical solution, in step 1, the preparation of the waste brick powder comprises the following steps:

After the waste bricks are crushed into waste brick particles with a particle size less than or equal to 5mm-10mm, the waste brick particles are dried, crushed, and sieved through a 100-400 mesh sieve, and the waste brick powder is collected and set aside.

As a preferred technical solution, in step 2, during the heating process, the heating rate is 2°C/min-10°C/min;

In step 2, during the cooling process,

When the temperature T is greater than 500°C, cool it down to 500°C at a cooling rate of 2°C/min-10°C/min, and then cool it down naturally to room temperature;

When the temperature T is less than or equal to 500°C, it is naturally cooled to room temperature.

As a preferred technical solution, the temperature T in step 2 is 200°C-1000°C.

As a preferred technical solution, the temperature T in step 2 is 200°C-800°C.

As a preferred technical solution, in step 2, the sieving uses a 100-400 mesh sieve;

As a preferred technical solution, in step 2, the heat-activated waste brick powder balls need to be ball-milled before screening.

As a preferred technical solution, the ball milling uses a ball mill, and the ball milling time is 30 minutes to 200 minutes.

Technical solution 2:

A cement-based material comprises the cementitious material containing recycled brick powder.

As a preferred technical solution, it also includes aggregate materials, auxiliary materials and water.

As a preferred technical solution, the aggregate material includes sand;

The auxiliary materials include one or more of fly ash, silica fume, expansion agent and water reducing agent.

As a preferred technical solution, the cement-based material includes the following raw materials in parts by weight: 100 parts of cementitious material, 40-85 parts of sand, 5-25 parts of fly ash, 0.5-5 parts of silica fume; 0.2-3 parts of expansion agent; 0.2-2 parts of water reducer; and 10-40 parts of water.

Compared with the prior art, the present invention has the following beneficial effects:

Since the recycled brick powder prepared by the traditional crushing and pulverizing process has a large porosity, it affects the strength and fluidity of the cement-based material. The fluidity can be compensated by increasing the mixing time, but there is no remedial measure for the strength, thus limiting the amount of recycled brick powder added to the cementitious material. The present invention prepares recycled brick powder by treating waste brick powder in a thermal activation manner, which promotes the formation of calcium aluminate in the brick powder, improves the mechanical properties of the material, and improves the compressive strength of the cement-based material, thereby making it possible to add a high content of recycled brick powder to the cementitious material.

The present invention adopts a ball milling process to mechanically activate the brick powder after thermal activation. Although it increases the specific surface area of the brick powder particles, it reduces the edges and corners of the brick powder particles, making them more rounded, thereby increasing the dense filling effect of the cementitious material system, increasing the density of the cement-based material, and not only improving the compressive strength of the cement-based material, but also reducing the porosity of the cement-based material, slightly reducing the water absorption rate, and slightly increasing the fluidity.

The present invention comprehensively considers the compressive strength, fluidity, water absorption and density of the material, and controls the replacement rate of recycled brick powder in cement in the cementitious material to 0-30%, so that the cement-based material not only has good mechanical properties, but also has good workability, ensuring the comprehensive performance of the material. Among them, when the replacement rate of recycled brick powder in cement in the cementitious material is controlled at 10-30%, the cement-based material still maintains a better performance level.

The present invention uses recycled brick powder as a cementitious material to replace part of cement, which not only reduces the amount of cement used and saves cement resources, but also provides a new way for the resource utilization of waste brick powder and expands the application scope of recycled brick powder.

The present invention strictly controls various parameters of the recycling process of waste brick powder, the selection and proportion of various raw materials in the cementitious material and the cement-based material. The comprehensive effect of various parameters makes the prepared cement-based material have good mechanical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a graph showing the compressive strength of cement-based material specimens prepared at different recycled brick powder replacement rates in Examples 1-7;

FIG2 is a flow graph of cement-based material specimens prepared with different recycled brick powder replacement rates in Examples 1-7;

FIG3 is a graph showing the water absorption of cement-based material specimens prepared at different recycled brick powder replacement rates in Examples 1-7;

FIG4 is a density diagram of cement-based material specimens prepared with different recycled brick powder replacement rates in Examples 1-7;

FIG5 is a graph showing the compressive strength of cement-based material specimens prepared from recycled brick powder at different activation temperatures T in Examples 8-12;

FIG6 is a crystal phase analysis diagram of recycled brick powder at different activation temperatures T in Examples 8-12;

FIG7 is a microscopic morphology of the cross section of cement-based material specimens prepared in Examples 1, 6, and 11;

FIG8 is a crystal phase analysis diagram of cement-based material specimens prepared in Examples 1, 6, and 11.

Detailed ways

The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In the present invention:

The cement was P•O 52.5 produced by Zhucheng Jiuqi Building Materials Co., Ltd.;

The sand is from the Pearl River, with a particle size of less than 0.6 mm and a fineness of 1.3-2.1;

The water reducing agent is polycarboxylate water reducing agent, and the mortar water reducing rate (%) is ≥ 14%;

The expansion agent is a calcium sulphoaluminate cement expansion agent;

The fly ash is Class I fly ash;

Silica fume (98%);

The water is tap water; the waste bricks are construction red bricks.

The chemical composition of the recycled brick powder obtained by crushing waste bricks is shown in Table 1;

Table 1

Element SiO ₂ Al ₂ O _{3 Fe2O3 ​ TiO2} CaO MgO _{K2O Na2O} content/% 67.88 19.52 4.55 0.68 0.65 0.83 3.32 0.36

The present invention is described in further detail below with reference to the accompanying drawings.

Example 1-7: Test on the influence of cement substitution degree in cementitious materials on the performance of cement-based materials

A cement-based material comprising the following raw materials in parts by weight:

Cementitious material: 100 parts;

Fly ash: 15 parts;

Water reducing agent: 0.45 parts;

Silica fume: 2 parts;

Bulking agent: 1 part;

Sand: 62.4 parts;

Water: 28.5 parts.

Wherein, the cementitious material includes cement and recycled brick powder;

The preparation method of the recycled brick powder comprises the following steps: crushing the waste bricks by a crusher to prepare waste brick particles with a particle size less than or equal to 6 mm, drying the waste brick particles, crushing them by a pulverizer, passing them through a 200-mesh sieve, and collecting the waste brick powder, which is the recycled brick powder.

The amounts of cement and recycled brick powder used in the cementitious materials of Examples 1-7 are shown in Table 2.

Table 2

Examples 8-12: Effects of waste brick powder activated at different temperatures on the compressive properties of cement-based materials

A cement-based material comprising the following raw materials in parts by weight:

Cementitious material: 100 parts;

Fly ash: 15 parts;

Water reducing agent: 0.45 parts;

Silica fume: 2 parts;

Bulking agent: 1 part;

Sand: 62.4 parts;

Water: 28.5 parts.

Wherein, the cementitious material comprises cement and recycled brick powder, in parts by weight, wherein the cement is 75 parts by weight and the recycled brick powder is 25 parts by weight;

The method for preparing the recycled brick powder comprises the following steps:

Step 1: Preparation of waste brick powder: crush the waste bricks with a crusher to produce waste brick particles with a particle size of less than or equal to 6 mm, dry the waste brick particles, and then crush them with a pulverizer, pass through a 200-mesh sieve, and collect the waste brick powder for later use;

Step 2: thermal activation: after heating the waste brick powder to temperature T at a heating rate of 5°C/min, keep the temperature constant for 6 hours for thermal activation, and then cool it to room temperature to obtain thermally activated brick powder;

During the cooling process,

When the temperature T is greater than 500°C, the temperature is lowered to 500°C at a cooling rate of 5°C/min, and then naturally lowered to room temperature;

When the temperature T is less than or equal to 500°C, it will naturally cool down to room temperature;

Step 3: Screening: The brick powder heat-activated in step 2 is screened through a 200-mesh sieve using a vibrating screen to obtain recycled brick powder.

The activation temperatures of Examples 8-12 during the preparation of recycled brick powder are shown in Table 3.

table 3

Embodiment 13:

A cement-based material comprising the following raw materials in parts by weight:

Cementitious material: 100 parts;

Fly ash: 15 parts;

Water reducing agent: 0.45 parts;

Silica fume: 2 parts;

Bulking agent: 1 part;

Sand: 62.4 parts;

Water: 28.5 parts.

Wherein, the cementitious material comprises cement and recycled brick powder, in parts by weight, wherein the cement is 75 parts by weight and the recycled brick powder is 25 parts by weight;

The method for preparing the recycled brick powder comprises the following steps:

Step 1: Preparation of waste brick powder: crush the waste bricks with a crusher to produce waste brick particles with a particle size of less than or equal to 6 mm, dry the waste brick particles, and then crush them with a pulverizer, pass through a 200-mesh sieve, and collect the waste brick powder for later use;

Step 2: thermal activation: the waste brick powder is heated to a temperature of T 800 °C at a heating rate of 5 °C/min, and then treated at a constant temperature for 5 h. After cooling to 500 °C at a cooling rate of 5 °C/min, the waste brick powder is naturally cooled to room temperature to obtain thermally activated brick powder.

Step 3: Mechanical activation: ball-milling the thermally activated brick powder in step 2 to obtain composite activated brick powder;

Step 4, sieving: the composite activated brick powder in step 3 is sieved through a 200-mesh sieve using a vibrating sieve machine to obtain regenerated brick powder.

Embodiment 14:

A cement-based material comprising the following raw materials in parts by weight:

Cementitious material: 100 parts;

Fly ash: 15 parts;

Water reducing agent: 0.45 parts;

Silica fume: 2 parts;

Bulking agent: 1 part;

Sand: 62.4 parts;

Water: 28.5 parts.

Wherein, the cementitious material comprises cement and recycled brick powder, in parts by weight, wherein the cement is 90 parts by weight and the recycled brick powder is 10 parts by weight;

The method for preparing the recycled brick powder comprises the following steps:

Step 1: Preparation of waste brick powder: crush the waste bricks with a crusher to produce waste brick particles with a particle size of less than or equal to 6 mm, dry the waste brick particles, and then crush them with a pulverizer, pass through a 200-mesh sieve, and collect the waste brick powder for later use;

Step 2: thermal activation: the waste brick powder is heated to a temperature of T 200 °C at a heating rate of 2 °C/min, treated at a constant temperature for 8 h, and then naturally cooled to room temperature to obtain thermally activated brick powder;

Step 3: Mechanical activation: ball-milling the thermally activated brick powder in step 2 to obtain composite activated brick powder;

Step 4: Screening: The composite activated brick powder in step 3 is screened through a 200-mesh sieve using a vibrating screen to obtain recycled brick powder.

Embodiment 15:

A cement-based material comprising the following raw materials in parts by weight:

Cementitious material: 100 parts;

Fly ash: 15 parts;

Water reducing agent: 0.45 parts;

Silica fume: 2 parts;

Bulking agent: 1 part;

Sand: 62.4 parts;

Water: 28.5 parts.

Wherein, the cementitious material comprises cement and recycled brick powder, in parts by weight, wherein the cement is 70 parts by weight and the recycled brick powder is 30 parts by weight;

The method for preparing the recycled brick powder comprises the following steps:

Step 1: Preparation of waste brick powder: crush the waste bricks with a crusher to produce waste brick particles with a particle size of less than or equal to 6 mm, dry the waste brick particles, and then crush them with a pulverizer, pass through a 300-mesh sieve, and collect the waste brick powder for later use;

Step 2: thermal activation: the waste brick powder is heated to a temperature of T1000 °C at a heating rate of 10 °C/min, and then kept at a constant temperature for 4 h. After cooling to 500 °C at a cooling rate of 10 °C/min, the waste brick powder is naturally cooled to room temperature to obtain thermally activated brick powder.

Step 3: ball-milling the heat-activated brick powder in step 2 to obtain composite activated brick powder;

Step 4: Screening: The composite activated brick powder in step 3 is screened through a 200-mesh sieve using a vibrating screen to obtain recycled brick powder.

Effect Example 1

1. Test methods:

1. Preparation and maintenance of specimens:

When the cement-based material prepared in each embodiment is used, after weighing each component in proportion, first, fly ash, water reducing agent, silica fume, and expansion agent are added to a mortar mixer and dry mixed and stirred evenly, and then water is added to the mortar mixer. After adding the cementitious material to the mortar mixer, after 30 seconds of low-speed rotation, sand is poured into the mortar mixer and stirred at a low speed for 30 seconds, and then rotated at a high speed for 90 seconds. After standing for 15 seconds, it is added to the test mold.

The size of the cement block produced in the experiment was 70.7 mm × 70.7 mm × 70.7 mm. After stirring, it was compacted on a vibration table and demolded after curing at room temperature for 48 h. In the compression test, the demolded test block was cured in a water bath at 55 °C for 7 days before testing its compressive strength.

2. Test indicators:

1) Compressive strength test: refer to the compressive strength test method of cement mortar in JGJ/T70-2009 "Standard for Basic Performance Test Methods of Building Mortar". Mortar cube compressive strength (MPa) = 1.35* (Nu /A); Nu - cube failure pressure (N), A - specimen pressure bearing area ( ^mm2 ).

2) Fluidity test: refer to GB/T 2419-2004 "Determination of fluidity of cement mortar". Mortar fluidity instrument, NLD-3 type, vibration frequency is 1 Hz, vibration plane diameter is 300 mm ± 1 mm, vibration number is 25 times, vibration drop distance is 10 mm ± 0.2 mm.

3) Water absorption test: refer to JGJ/T 70-2009 "Standard for test methods of basic properties of building mortar".

4) Density test: Refer to JGJ/T 70-2009 "Standard for Test Methods for Basic Properties of Building Mortar" to test dry weight. Density of test block (g/cm ³ ) = G/V; G - dry weight of test block (g), V - volume of test block (7.07 cm*7.07 cm*7.07 cm).

5) Crystal phase analysis: Take the center pieces of the compression test, place the samples in an oven for drying, grind the dried samples into powder, sieve through 200 mesh, and analyze them using a X-ray diffractometer. Brick powder is directly sieved through 200 mesh and dried, and then its crystal phase is analyzed using an X-ray diffractometer.

6) Characterization of cross-sectional microstructure: Take granular fragments with a particle size of 2-10 mm crushed in the compression test, place the fragments in ethanol for ultrasonic treatment to remove surface dust, and observe their cross-section using an electron microscope after high-temperature drying.

2. Test results and analysis:

1. The effect of the compounding ratio of cement and recycled brick powder in cementitious materials on the gel properties of cement-based materials. The results are shown in Figures 1-4.

1) Compression test: From the comparison of Examples 1-7 in Figure 1, it can be seen that:

When the replacement rate of recycled brick powder is less than 15%, the compressive strength of the test block decreases with the increase of the replacement rate of recycled brick powder. This is because after the addition of recycled micropowder, the overall gel properties of the cementitious material decreases, which leads to a decrease in the compressive strength of the cement-based material test block.

When the replacement rate of recycled brick powder is between 15% and 25%, the compressive strength of the test block increases with the increase of the replacement rate of recycled brick powder. This may be due to the fact that the internal structure of the recycled brick powder prepared by crushing and grinding waste bricks is loose and porous. Therefore, in the early stage, it can absorb more water to react with hydration and generate more cementitious materials, which improves the early strength. At the same time, the inactive fine particles in the recycled micro-powder can play a "micro-aggregate role", improve the particle grading of cement cementitious materials, fill the pores in the cement-based material slurry, and improve the density of the cement-based material topic, so that the filling water required between particles is reduced, and the hydration water in the slurry is relatively increased, so that the cement hydration is more sufficient;

When the replacement rate of recycled brick powder is greater than 25%, the compressive strength of the test block decreases with the increase of the replacement rate of recycled brick powder. This may be because, when the replacement rate of recycled brick powder is too large, the cementitious material generated in the test block is significantly reduced, and the material supporting the strength of the specimen is reduced. Therefore, the compressive strength is significantly reduced.

2) Fluidity: From Figure 2, it can be seen that:

As the replacement rate of recycled brick powder increases, the fluidity of cement-based material slurry decreases. This is because: compared with cement particles, recycled brick powder particles are finer, have a larger specific surface area, and require more water. Therefore, water is adsorbed by recycled brick powder, resulting in a decrease in the water content between the pores of cement particles and a decrease in the fluidity of cement-based material slurry. In addition, the early activity of recycled brick powder is low, and the particle size is small. It fills between cement particles, increasing the flow resistance of cement-based material slurry. At the same time, recycled brick powder itself has more pores, and the water absorption capacity of recycled brick powder is enhanced, while the water between cement-based material particles is reduced, and the internal friction resistance between particles is increased, causing the fluidity of cement-based material slurry to decrease with the increase of the replacement rate of recycled brick powder.

3) Water absorption rate: From Figure 3, it can be seen from Examples 1-7:

As the replacement rate of recycled brick powder increases, the water absorption of cement-based material specimens increases first and then decreases. After analysis, it is believed that this is because the particle size of the recycled brick powder particles after crushing and pulverization is finer. Therefore, when the replacement rate of recycled brick powder is greater than 20%, the "micro-aggregate effect" of the recycled brick powder fills the internal pores of the cement-based material, reducing its porosity and thus reducing its water absorption rate; when the replacement rate of recycled brick powder is less than 20%, the "micro-aggregate effect" of the recycled brick powder is very weak or even non-existent, which is not enough to make up for the adsorption of water by the micropores of the recycled brick powder itself.

4) Density: From Figure 4, examples 1-7, it can be seen that:

With the increase of the replacement rate of recycled brick powder, its density decreases first and then increases, and the density change difference can reach about 10%. After analysis, this may be because the building red brick powder is a light powder with low density. At the same time, the water absorption rate of brick powder varies greatly, and there are more pores inside the material, so the density of the test block prepared with recycled brick powder becomes smaller.

2. Effect of waste brick powder activated at different temperatures on the compressive properties of cement-based materials. The results are shown in Figure 5.

From the comparison of Examples 8-12 in Figure 5, it can be seen that the temperature T of the activation treatment has a great influence on the compressive strength of the cement-based material. As the temperature T increases, the compressive strength of the cement-based material shows a trend of first decreasing, then increasing, and then decreasing. In the temperature range of 700-900°C, the compressive strength is good, and when the temperature T is 800°C, the compressive strength of the cement-based material reaches a peak.

In addition, from the data comparison between Example 6 in FIG. 1 and Example 11 in FIG. 5 , it can be seen that Example 11 uses a high temperature of 800° C. to perform thermal activation treatment on waste brick powder, and the compressive strength is increased by 30% compared with Example 6 which is not thermally activated.

3. Crystalline phase analysis of recycled brick powder activated at different temperatures. The results are shown in Figure 6

As can be seen from Figure 6: the heat-activated brick powder obtained by treating at 200°C in Example 8 and the heat-activated brick powder obtained by treating at 400°C in Example 9 showed diffraction peaks of _SiO2 and _{calcitriol ( CaAl2Si2O8} · _4H2O ), while the heat-activated brick powder obtained by treating at 600°C in Example 10, 800°C in Example 11, and 1000°C in Example 12 only showed the _SiO2 diffraction peak, indicating that under high temperatures of 200°C and 400°C, substances such as _SiO2 , _{Al2O3 ,} and CaO in the heat-activated brick powder react to generate calcitriol, and when the temperature exceeds 600°C, calcitriol decomposes.

4. The effect of recycled brick powder preparation process on the microstructure of cement-based material test blocks, see Figure 7;

As can be seen from Figure 7: in Example 1, the cement-based material specimen in which the recycled brick powder was not added to the cementitious material, the needle-shaped calcium sulfonate crystals grew well; while in Example 6, the cement-based material specimen in which the crushed recycled brick powder was added, it was difficult to observe the crystals in the cross section of the specimen; and in Example 11, the cement-based material specimen in which the recycled brick powder activated at 800°C was added, needle-shaped crystals were observed again in the cross section of the specimen. Therefore, it can be concluded that the crystals in the recycled brick powder were restored after high-temperature activation at 800°C, and thermal activation can promote the formation of calcium sulfonate in the recycled brick powder, thereby improving the mechanical properties of the material.

5. The influence of the preparation process of recycled brick powder on the crystal phase of cement-based material test pieces, see Figure 8;

As shown in Figure 8, in the cement-based material specimen without recycled brick powder in Example 1, the diffraction peaks of quartz phase (SiO ₂ ), hydrated calcium silicate phase (Ca ₃ Si ₂ O ₇ ·2H ₂ O), and calcium hydroxide phase (Ca(OH) ₂ ) are obvious; while in the cement-based material specimen with recycled brick powder treated by crushing in Example 6, the intensity of the diffraction peak of the quartz phase decreases; while in the cement-based material specimen with recycled brick powder treated by high temperature heat activation at 800°C in Example 11, the intensity of the diffraction peak of the quartz phase is significantly enhanced;

Since _SiO2 in recycled brick powder has high volcanic ash activity, it can quickly react with calcium hydroxide produced by cement during the hydration process, effectively refine calcium hydroxide grains, and generate high-strength hydrated calcium silicate (CSH gel). At the same time, since _SiO2 can well fill the pores after the hydration reaction of concrete, it can improve the density of cement, thereby effectively improving the early strength of cement-based materials. At the same time, after directly adding 25% brick powder to prepare cement-based materials, the XRD diagram of the cross-section of the test block shows that the diffraction peak of zeolite disappears, and the XRD diagram of the material prepared by adding high-temperature activated brick powder finds that the diffraction peak of zeolite reappears, indicating that the addition of thermally activated waste brick powder can promote the formation of zeolite and help improve the compressive strength of the material.

6. The effect of the preparation process of recycled brick powder on the gel properties of cement-based material test blocks is shown in Table 4;

Table 4

Example 1 Example 6 Embodiment 11 Example 13 Compressive strength/MPa 95 89.5 103.2 109.6 Fluidity/mm 300 294 270 275 Water absorption/% 3.3 5.5 4.5 4.1 Density/g/ ^cm3 2.08 1.8 1.89 1.92

From the comparison between Example 6 and Example 11, it can be seen that the use of 800°C heat-activated waste brick powder to prepare recycled brick powder can significantly improve the mechanical properties of the material and the compressive strength of the cement-based material because the formation of calcium aluminate and/or hydrated calcium zeolite in the brick powder is promoted; however, due to the dehydration of the recycled brick powder during the heat activation process, the water absorption rate of the brick powder increases when the mortar is stirred, the free water content between the mortar particles decreases, and the fluidity of the cement-based material slurry decreases slightly.

From the comparison between Example 11 and Example 13, it can be seen that the present invention adopts ball milling process to process the recycled brick powder after heat activation. Although it increases the specific surface area of the brick powder particles, it reduces the edges and corners of the brick powder particles, making them more rounded, thereby increasing the dense filling effect of the cementitious material system, increasing the density of the cement-based material, and not only improving the compressive strength of the cement-based material, but also reducing the porosity of the cement-based material, slightly reducing the water absorption rate, and slightly increasing the fluidity.

7. Gel properties of cement-based material test blocks prepared by thermal activation + mechanical activation, see Table 5

table 5

Example 13 Embodiment 14 Embodiment 15 Compressive strength/MPa 109.6 85.4 95.5 Fluidity/mm 275 295 280 Water absorption/% 4.1 3.52 4.2 Density/g/ ^cm3 1.92 2.03 2.02

The above-described embodiments are only preferred embodiments of the present invention, and are not exhaustive of the feasible implementations of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims (6)

1. A cementitious material comprising recycled brick dust, comprising cement and recycled brick dust; the percentage content of the cement is 75-85% by weight; the percentage content of the regenerated brick powder is 15% -25%;

The preparation method of the regenerated brick powder comprises the following steps:

step 1, preparing waste brick powder: crushing waste bricks to obtain waste brick particles with the particle size of less than or equal to 5mm-10mm, drying, crushing and sieving the waste brick particles with a 100-400-mesh sieve, and collecting waste brick powder for later use;

The waste bricks adopt building red bricks;

step 2, activating: heating the waste brick powder to a temperature T, performing constant temperature treatment for 2-8 hours for heat activation, cooling to room temperature, and sieving to obtain the modified brick; the temperature T is 200-800 ℃;

In the step 2, a 100-400 mesh sieve is adopted for sieving;

In the step2, before sieving, the waste brick powder after heat activation is subjected to ball milling treatment;

the ball milling time is 30 minutes to 200 minutes.

2. A cementitious material comprising reclaimed tile powder as recited in claim 1,

In the step 2, in the heating process, the heating rate is 2 ℃/min-10 ℃/min;

In the step 2, in the process of cooling,

When the temperature T is higher than 500 ℃, naturally cooling to room temperature after cooling to 500 ℃ at a cooling rate of 2 ℃/min-10 ℃/min;

When the temperature T is less than or equal to 500 ℃, naturally cooling to room temperature.

3. A cementitious material comprising reclaimed tile powder as recited in claim 1,

The ball milling adopts a ball mill.

4. A cement-based material comprising the cement-based material comprising reclaimed brick powder of any one of claims 1-3.

5. The cementitious material of claim 4, further comprising aggregate material, adjuvant, and water.

6. A cement-based material according to claim 5, wherein,

The aggregate material comprises sand;

the auxiliary materials comprise one or more of fly ash, silica fume, an expanding agent and a water reducing agent.