Recycled concrete and preparation method thereof
1. A recycled concrete characterized by: the recycled concrete is prepared from the following raw materials in parts by weight:
40-50 parts of cement, 125 parts of coarse aggregate 105 and regenerated fine aggregate, 10-15 parts of vitrified micro bubbles, 1-2.5 parts of an additive and 13-20 parts of water;
the recycled fine aggregate is prepared by activating coal cinder by using an activating material, wherein the weight ratio of the activating material to the coal cinder is (0.5-2): 1; the activating material comprises fly ash, granulated blast furnace slag and attapulgite.
2. Recycled concrete according to claim 1, characterized in that: the total weight of the fly ash and the granulated blast furnace slag accounts for 70-95% of the weight of the coal slag.
3. Recycled concrete according to claim 2, characterized in that: the weight ratio of the granulated blast furnace slag to the fly ash is (1.2-2.7): (0.8-1.3).
4. Recycled concrete according to claim 1, characterized in that: in the coal cinder, the content of silicon dioxide is more than 45 percent, and the content of aluminum oxide is more than 20 percent.
5. Recycled concrete according to any one of claims 1 to 4, characterized in that: the recycled fine aggregate is prepared by the following method:
roasting the coal cinder, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; and then mixing the coal cinder powder with an activating material, and carrying out ultrasonic treatment to obtain the regenerated fine aggregate.
6. Recycled concrete according to claim 5, characterized in that: the cinder roasting process comprises the following steps: the coal slag is roasted for 2 to 4 hours at 580-620 ℃.
7. Recycled concrete according to claim 5, characterized in that: in the step of ball milling, active carbon is added into the coal cinder, and the weight of the active carbon accounts for 0.5-1.2% of the weight of the coal cinder.
8. Recycled concrete according to claim 1, characterized in that: the additive comprises a water reducing agent, a retarder and a waterproof agent.
9. The method for producing recycled concrete of any one of claims 1 to 8, wherein: the method comprises the following steps:
and uniformly mixing the cement, the coarse aggregate, the recycled fine aggregate, the vitrified micro bubbles, the additive and the water to obtain the recycled concrete.
10. The method for producing recycled concrete according to claim 9, wherein: the preparation steps of the recycled fine aggregate are as follows:
roasting the coal cinder, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then mixing the coal cinder powder with an activating material, and carrying out ultrasonic treatment to obtain regenerated fine aggregate;
and during roasting, roasting the coal cinder at 580-620 ℃ for 2-4 hours.
Background
Every year, construction of infrastructure in China needs hundreds of millions of tons of sand and stone materials, and when a high building is pulled out, the phenomena of white hanging of a green mountain and yellow river water are caused, so that the environment of China is seriously influenced. Meanwhile, the sandstone resources are not regenerated, so that in order to protect the environment and the limited sandstone resources, other materials are urgently needed to replace the sandstone resources.
Meanwhile, with the increasing growth of the scale of the coal chemical industry in China, the yield of the coal cinder is increased year by year, the land is invaded by simple landfill, the safety and environmental protection risks are increasingly emphasized, and the newly issued standard for controlling pollutants in a common industrial solid waste storage site and a disposal site also provides a stricter standard for common industrial solid waste landfill. Therefore, in order to improve the recycling added value and widen the recycling way of the coal slag, the current critical problem is to treat waste by waste and change waste into valuable.
Disclosure of Invention
The application provides recycled concrete and a preparation method thereof, which can take the processed coal cinder as concrete aggregate, change the coal cinder into valuables, reduce the exploitation of natural aggregate, and are beneficial to saving resources and protecting the environment.
In a first aspect, the present application provides a recycled concrete:
the recycled concrete is prepared from the following raw materials in parts by weight:
40-50 parts of cement, 125 parts of coarse aggregate 105 and regenerated fine aggregate, 10-15 parts of vitrified micro bubbles, 1-2.5 parts of an additive and 13-20 parts of water;
the recycled fine aggregate is prepared by activating coal cinder by using an activating material, wherein the weight ratio of the activating material to the coal cinder is (0.5-2): 1; the activating material comprises fly ash, granulated blast furnace slag and attapulgite.
By adopting the technical scheme, the coal slag is treated by the activating material mainly prepared from the fly ash, the granulated blast furnace slag and the attapulgite, so that the recycled fine aggregate can be prepared, the waste coal slag and the slag are changed into valuable, the exploitation of the natural fine aggregate is reduced, the resource recycling is facilitated, and the environment is protected. Furthermore, it is most important that the recycled concrete can be prepared by applying the fine aggregate to concrete without impairing the basic mechanical properties of the recycled concrete.
The coal ash, the granulated blast furnace slag and the attapulgite are matched with each other to activate the coal slag, so that the later strength of the recycled concrete can be enhanced, and the impermeability coefficient of the recycled concrete can be reduced.
In the application, the recycled fine aggregate and the vitrified micro bubbles are mutually matched, so that the workability of recycled concrete can be improved, and the strength of the recycled concrete is improved.
Preferably, the total weight of the fly ash and the granulated blast furnace slag accounts for 70-95% of the weight of the coal slag. Further preferably, the weight ratio of the granulated blast furnace slag to the fly ash is (1.2-2.7): (0.8-1.3).
By adopting the technical scheme, the fly ash and the granulated blast furnace slag are matched according to a specific proportion, so that the strength of the recycled concrete can be enhanced, and the workability of the recycled concrete can be improved. The inventors found that when the weight ratio of the activating material to the coal slag is 0.7:1, the total weight of the fly ash and the granulated blast furnace slag accounts for 80 percent of the weight of the fly ash, and when the weight ratio of the granulated blast furnace slag to the fly ash is 2.5:1, the performance of the obtained recycled fine aggregate is the best, and at the moment, the recycled fine aggregate is applied to recycled concrete, and the performance of the recycled concrete is the best.
Preferably, in the coal cinder, the content of silicon dioxide is more than 45%, and the content of aluminum oxide is more than 20%.
The coal cinder generally comprises high-calcium type coal cinder, high-iron type coal cinder and high-silicon type coal cinder, and in the application, the high-silicon type coal cinder with the silicon dioxide content of more than 45% and the aluminum oxide content of more than 20% is adopted, and the existence of oxides such as silicon dioxide, aluminum oxide and the like guarantees that the coal cinder has enough strength, thereby being beneficial to improving the strength of recycled concrete.
Preferably, the recycled fine aggregate is prepared by a method comprising the following steps:
roasting the coal cinder, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; and then mixing the coal cinder powder with an activating material, and carrying out ultrasonic treatment to obtain the regenerated fine aggregate. Further preferably, the cinder roasting process comprises the following steps: the coal slag is roasted for 2 to 4 hours at 580-620 ℃.
Firstly, roasting the coal cinder, removing water in the coal cinder and increasing active sites on the surface of the coal cinder; then ball milling is carried out, and the coal cinder is changed into coal cinder powder with the required particle size; the coal cinder powder and the active material are subjected to ultrasonic treatment, so that the coal cinder can be activated, and the recycled fine aggregate is prepared. The ultrasonic treatment is beneficial to enhancing the activity of the coal cinder, and can accelerate the activation rate, in addition, the ultrasonic treatment can reduce the particle size of the coal cinder powder, and improve the workability of the recycled concrete. Preferably, the frequency of sonication is between 10 and 20 kHz.
When the coal slag is roasted, the activity of the coal slag can be influenced by overhigh or overlow temperature, and when the coal slag is roasted for 2-4 hours at 580-620 ℃, the roasting activity is good and the roasting efficiency is fastest.
Preferably, in the ball milling step, activated carbon is added into the coal cinder, and the weight of the activated carbon accounts for 0.5-1.2% of the weight of the coal cinder.
By adopting the technical scheme, the active carbon is added into the coal cinder during ball milling, on one hand, the active carbon can adsorb the smell of the coal cinder, so that the taste of the recycled fine aggregate can be reduced, and on the other hand, the addition of the active carbon is beneficial to improving the grinding efficiency and enables the grinding to be more uniform.
Preferably, the admixture comprises a water reducing agent, a retarder and a waterproofing agent. Preferably, the water reducing agent can be a polycarboxylic acid water reducing agent, the retarder can be tartaric acid or calcium saccharate, and the waterproof agent can be modified organosilicon waterproof agent WR 2. The admixture composed of the water reducing agent, the retarder and the waterproof agent is added into the recycled concrete, so that the construction performance and the waterproof performance of the concrete are improved. The inventor finds that in the admixture, when the weight ratio of the water reducing agent, the retarder and the waterproof agent is 1: (0.2-0.5) and (0.1-0.3), the concrete has the best performance, and the weight ratio of the water reducing agent, the retarder and the waterproofing agent is 1: 0.5:0.2.
In a second aspect, the present application provides a method for preparing recycled concrete as described above, which adopts the following technical scheme: a preparation method of recycled concrete comprises the following steps:
and uniformly mixing the cement, the coarse aggregate, the recycled fine aggregate, the vitrified micro bubbles, the additive and the water to obtain the recycled concrete.
Preferably, the preparation steps of the recycled fine aggregate are as follows
Roasting the coal cinder, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then mixing the coal cinder powder with an activating material, and carrying out ultrasonic treatment to obtain regenerated fine aggregate;
and during roasting, roasting the coal cinder at 580-620 ℃ for 2-4 hours.
By adopting the technical scheme, the activation treatment of the coal cinder is relatively simple, and in addition, the coal cinder has wide sources and low price, so the cost of the recycled fine aggregate is low, and the cost of recycled concrete can be reduced.
In summary, the present application has the following beneficial effects:
1. the natural fine aggregate is replaced by the material which is obtained by activating the coal cinder by using the fly ash, the granulated blast furnace slag and the attapulgite, so that the exploitation of the natural aggregate is reduced while the waste of the coal cinder is changed into valuable, the resource is saved, and the environment is protected;
2. the coal slag is activated by using specific amount of fly ash, granulated blast furnace slag and attapulgite, so that the later strength of the recycled concrete can be enhanced, and the impermeability coefficient of the recycled concrete can be reduced.
Detailed Description
The present application will be described in further detail with reference to examples. Specifically, the following are described: the following examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer; the starting materials used in the following examples are all those conventionally commercially available except where specifically noted.
Coal cinder: in preparation examples 1 to 7, the coal slag is high-silicon type coal slag, specifically, the high-silicon type coal slag contains 47.12% of silicon dioxide, 22.3% of aluminum oxide and 12.09% of calcium oxide;
in preparation example 8, the coal slag is high-calcium type coal slag, and specifically, the high-calcium type coal slag contains 37.14% of silicon dioxide, 13.63% of aluminum oxide and 29.82% of calcium oxide.
Preparation of recycled fine aggregate
Preparation example 1
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-silicon coal cinder at 500 ℃ for 2h, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then, the pulverized coal slag was mixed with 16.67kg of fly ash, 16.67kg of granulated blast furnace slag and 16.67kg of attapulgite, and subjected to ultrasonic treatment at a frequency of 13kHz for 15min to obtain a recycled fine aggregate 1.
Preparation example 2
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-silicon coal cinder at 500 ℃ for 2h, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then, the pulverized coal slag was mixed with 33.33kg of fly ash, 33.33kg of granulated blast furnace slag and 33.33kg of attapulgite, and subjected to ultrasonic treatment at a frequency of 13kHz for 15min to obtain a recycled fine aggregate 2.
Preparation example 3
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-silicon coal cinder at 500 ℃ for 2h, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; subsequently, the pulverized coal slag was mixed with 66.67kg of fly ash, 66.67kg of granulated blast furnace slag and 66.67kg of attapulgite, and subjected to ultrasonic treatment at a frequency of 13kHz for 15min to obtain a recycled fine aggregate 3.
Preparation example 4
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-silicon coal cinder at 500 ℃ for 2h, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then, the pulverized coal slag is mixed with 28kg of pulverized coal ash, 28kg of granulated blast furnace slag and 14kg of attapulgite, and ultrasonic treatment is carried out for 15min at the frequency of 13kHz, thus obtaining the recycled fine aggregate 4.
Preparation example 5
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-silicon coal cinder at 500 ℃ for 2h, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then, the pulverized coal slag was mixed with 44.89kg of fly ash, 21.62kg of granulated blast furnace slag and 3.5kg of attapulgite, and subjected to ultrasonic treatment at a frequency of 13kHz for 15min to obtain a recycled fine aggregate 5.
Preparation example 6
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-silicon coal cinder at 500 ℃ for 2h, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then, the pulverized coal slag is mixed with 40kg of pulverized coal ash, 16kg of granulated blast furnace slag and 14kg of attapulgite, and ultrasonic treatment is carried out for 15min at the frequency of 13kHz, thus obtaining the recycled fine aggregate 6.
Preparation example 7
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-silicon coal cinder at 500 ℃ for 2h, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then, the pulverized coal slag was mixed with 29.4kg of fly ash, 19.6kg of granulated blast furnace slag and 21kg of attapulgite, and subjected to ultrasonic treatment at a frequency of 13kHz for 15min to obtain a recycled fine aggregate 7.
Preparation example 8
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-calcium type coal cinder at 500 ℃ for 2h, and then carrying out ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then, the pulverized coal slag is mixed with 40kg of pulverized coal ash, 16kg of granulated blast furnace slag and 14kg of attapulgite, and ultrasonic treatment is carried out for 15min at the frequency of 13kHz, thus obtaining the recycled fine aggregate 8.
Preparation example 9
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-calcium type coal cinder at 500 ℃ for 2h, and then adding 1.2kg of activated carbon for ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; then, the pulverized coal slag was mixed with 40kg of fly ash, 16kg of granulated blast furnace slag and 14kg of attapulgite, and subjected to ultrasonic treatment at a frequency of 13kHz for 15min to obtain a recycled fine aggregate 9.
Recycled Fine aggregate comparative example 1
The preparation steps of the recycled fine aggregate are as follows:
roasting 100kg of high-calcium type coal cinder at 500 ℃ for 2h, and then adding 1.2kg of activated carbon for ball milling to obtain coal cinder powder with the particle size of less than or equal to 4.75 mm; and then mixing the coal slag powder with 70kg of fly ash, and carrying out ultrasonic treatment for 15min at the frequency of 13kHz to obtain the comparative recycled fine aggregate 1.
Examples
Example 1
A preparation method of recycled concrete comprises the following steps:
uniformly mixing 40kg of cement, 105kg of coarse aggregate, 72kg of recycled fine aggregate 1, 15kg of vitrified micro bubbles, 1kg of polycarboxylic acid water reducing agent and 20kg of water to obtain the recycled concrete.
Example 2
A preparation method of recycled concrete comprises the following steps:
50kg of cement, 125kg of coarse aggregate, 60kg of recycled fine aggregate 1, 10kg of vitrified micro bubbles, 1.5kg of polycarboxylic acid water reducing agent and 27kg of water are uniformly mixed to prepare the recycled concrete.
Example 3
A preparation method of recycled concrete comprises the following steps:
47.2kg of cement, 117kg of coarse aggregate, 68kg of recycled fine aggregate 1, 13kg of vitrified micro bubbles, 1.2kg of polycarboxylic acid water reducing agent and 23kg of water are uniformly mixed to prepare the recycled concrete.
Example 4
A preparation method of recycled concrete comprises the following steps:
47.2kg of cement, 117kg of coarse aggregate, 68kg of recycled fine aggregate 1, 13kg of vitrified micro bubbles, 0.92kg of polycarboxylic acid water reducing agent, 0.18kg of sugar calcium, 0.1kg of modified organosilicon waterproofing agent WR2 and water are mixed uniformly to prepare the recycled concrete.
Example 5
A preparation method of recycled concrete comprises the following steps:
47.2kg of cement, 117kg of coarse aggregate, 68kg of recycled fine aggregate 1, 13kg of vitrified micro bubbles, 0.66kg of polycarboxylic acid water reducing agent, 0.34kg of sugar calcium, 0.2kg of modified organosilicon waterproofing agent WR2 and water are mixed uniformly to prepare the recycled concrete.
Example 6
A preparation method of recycled concrete comprises the following steps:
47.2kg of cement, 117kg of coarse aggregate, 68kg of recycled fine aggregate 1, 13kg of vitrified micro bubbles, 0.71kg of polycarboxylic acid water reducing agent, 0.35kg of calcium saccharate, 0.14kg of modified organosilicon waterproofing agent WR2 and water are mixed uniformly to prepare the recycled concrete.
Examples 7 to 14
Examples 7 to 14 differ from example 6 only in that in examples 7 to 14, recycled fine aggregates prepared in different recycled fine aggregate preparation examples were selected, as shown in table 1 below.
TABLE 1 list of recycled fine aggregates used in examples 7-14
Comparative example
Comparative example 1
Comparative example 1 differs from example 14 only in that in comparative example 1, recycled fine aggregate was used and comparative recycled fine aggregate 1 was prepared in comparative example 1, and the rest was identical to example 14.
Comparative example 2
Comparative example 2 differs from example 14 only in that in comparative example 2, natural sand was used instead of the recycled fine aggregate 9, and the rest was the same as example 14.
Comparative example 3
Comparative example 3 differs from example 14 only in that in comparative example 3, part of the recycled fine aggregate 9 is replaced with part of natural sand; that is, in comparative example 3, 68kg of fine aggregate was composed of 34kg of natural sand and 34kg of recycled fine aggregate 9, and the remainder was identical to example 14.
Comparative example 4
Comparative example 4 differs from example 14 only in that in comparative example 4, no vitrified small balls are added, and the rest corresponds to example 14.
Performance test
The compression strength, the impermeability rating and the slump (initial slump, 1-hour slump) of the recycled concrete samples prepared in examples 1 to 14 and comparative examples 1 to 4 were measured, and the specific measurement results are shown in Table 2 below.
Compressive strength: detecting according to the standard GB/T50081-2002 Standard for testing the mechanical properties of common concrete; slump: detecting according to a standard GB/T50080-2016 standard of a common concrete mixture performance detection method;
and (3) anti-permeability grade: and (3) detecting according to the standard GB/T50082-2009 Standard test method for the long-term performance and the durability of the common concrete.
TABLE 2 Performance test Table for each sample of recycled concrete
It can be seen from the combination of examples 1-3 and Table 2 that the ratio of recycled concrete affects the properties;
it can be seen by combining examples 3-6 with Table 2 that the selection and proportion of the admixture also affects the properties of the recycled concrete, when the weight ratio of the water reducing agent, retarder and waterproofing agent is 1: (0.2-0.5) when the components are mixed according to the proportion of (0.1-0.3), the performance of the concrete is better; optimally, the weight ratio of the water reducing agent to the retarder to the waterproofing agent is 1: 0.5:0.2.
It can be seen by combining examples 6 to 8 and comparative example 1 with table 2 that the weight ratio of the activating material to the cinder of the recycled fine aggregate affects the properties of the recycled concrete when the weight ratio of the activating material to the cinder (0.5 to 0.1): 1, the performance of the recycled concrete is good; optimally, the weight ratio of the activating material to the coal slag is 0.7: 1;
it can be seen by combining examples 9-12 and comparative example 1 with Table 2 that the composition and ratio of fly ash, granulated blast furnace slag and attapulgite all affect the properties of recycled concrete; when the weight ratio of the activating material to the coal cinder is 0.7:1, the total weight of the fly ash and the granulated blast furnace slag accounts for 80 percent of the weight of the coal slag, and when the weight ratio of the granulated blast furnace slag to the fly ash is 2.5:1, the performance of the obtained recycled concrete is optimal.
Combining example 11 and example 13, it is known that the type of cinder affects the performance of the recycled concrete, and the selection of high-silicon cinder is beneficial to improving the strength of the recycled concrete.
Combining example 11 and example 14, it is clear that the addition of activated carbon to the ground coal does not affect the properties of the recycled concrete.
As can be seen from comparative example 14 and comparative examples 2 to 3, the use of the recycled fine aggregate of the present application in the complete replacement or partial replacement of natural sand does not affect the properties of recycled concrete; in practical application, in order to reduce the cost and the exploitation of natural sand, the recycled fine aggregate is used for completely replacing the natural sand.
It can be seen from comparative example 14 and comparative example 4 that the strength and the impermeability of the recycled concrete can be improved by the combination of the vitrified small balls and the recycled fine aggregate.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
