Mix proportion design method of vitrified microbead regenerated thermal insulation concrete

Abstract

The invention discloses a mix proportion design method of vitrified microbead regenerated thermal insulation concrete, which comprises the following steps: based on common concrete, replacing natural coarse aggregate with regenerated coarse aggregate in equal volume, and doping vitrified microbead particles into the regenerated concrete as thermal insulation aggregate; a response surface method is adopted to describe the influence of the water-binder ratio, the replacement rate of the recycled coarse aggregate, the mixing amount of the vitrified microbeads and the interaction between every two on the compressive strength and the heat conductivity coefficient of the vitrified microbead recycled thermal insulation concrete; and establishing a regression prediction model, and performing expected assignment on the regression prediction model to obtain the maximum value of compressive strength and the minimum value of heat conductivity coefficient, thereby obtaining the optimal mix proportion of the vitrified microbead regenerated thermal insulation concrete. The recycled aggregate is used for replacing natural aggregate, the utilization rate of natural gravel is reduced, and a new thought is provided for consumption of waste concrete; the heat conductivity coefficient of the concrete is reduced by doping the vitrified microbead heat-insulating aggregate, the building self-heat-insulating effect is improved on the premise of ensuring the compressive strength of the concrete, and the building energy consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete materials, and particularly relates to a mix proportion design method for vitrified microsphere recycled thermal insulation concrete. Background Art

[0002] At present, there is a serious shortage in the supply of natural sand and gravel in China. Due to reasons such as municipal construction, a large amount of waste concrete will be generated from demolished buildings. Processing waste concrete into recycled aggregate for preparing recycled concrete not only solves the problem of waste concrete disposal but also alleviates the shortage of natural sand and gravel resources. The building operation industry, as an important field of energy consumption and carbon emission, it is urgent to promote energy conservation and emission reduction measures. The reason for the high energy consumption of buildings is usually the poor thermal insulation performance and large thermal conductivity of the external wall enclosure structure. Vitrified microspheres are inorganic lightweight adiabatic spherical particles with a vitrified surface and a honeycomb-like porous structure inside. Research shows that concrete incorporated with vitrified microspheres can have dual functions of heat insulation and load-bearing.

[0003] Since there are more and more complex interfacial weak links in recycled aggregate compared with natural aggregate, the compressive strength of recycled concrete will decrease, but the mortar attached to its surface can reduce the thermal conductivity of concrete. As a lightweight material, a large amount of vitrified microspheres incorporated will reduce the compressive strength of concrete, but at the same time its cavity structure will reduce the thermal conductivity. Therefore, it is necessary to find a balance point to make the compressive strength of recycled thermal insulation concrete as high as possible and the thermal conductivity as low as possible. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a mix proportion design method for vitrified microsphere recycled thermal insulation concrete, including:

[0005] Based on ordinary concrete, natural coarse aggregate is replaced by recycled coarse aggregate with equal mass, and at the same time, vitrified microsphere particles are incorporated into recycled concrete as thermal insulation aggregate;

[0006] The response surface method is used to describe the effects of water-binder ratio, recycled coarse aggregate replacement rate, vitrified microsphere content, and the interaction between them on the compressive strength and thermal conductivity of vitrified microsphere recycled thermal insulation concrete;

[0007] A regression prediction model is established, and expected values are assigned to the regression prediction model to obtain the maximum value of compressive strength and the minimum value of thermal conductivity, and then the optimal mix proportion of vitrified microsphere recycled thermal insulation concrete is selected.

[0008] Preferably, the process of using the response surface method to describe the effects of water-binder ratio, recycled coarse aggregate replacement rate, vitrified microsphere content, and the interaction between them on the compressive strength and thermal conductivity of vitrified microsphere recycled thermal insulation concrete includes:

[0009] The water-binder ratio, replacement rate of recycled coarse aggregate, and dosage of expanded perlite are selected as influencing factors;

[0010] Three levels are determined as follows: water-binder ratio of 0.45, 0.5, 0.55; replacement rate of recycled coarse aggregate of 0%, 50%, 100%; dosage of expanded perlite of 80 kg / m 3 、130 kg / m 3 、180 kg / m 3 ;

[0011] Based on the Box-Behnken method in the response surface method, a design mix ratio is established. The compressive strength and thermal conductivity of the recycled thermal insulation concrete are used as evaluation indexes. According to the design mix ratio, test blocks of expanded perlite recycled thermal insulation concrete are prepared, and the compressive strength and thermal conductivity are measured. The response surface method is used to establish a fitting equation between the factors and the responses, and the fitting situation between the predicted values and the measured values is analyzed.

[0012] Preferably, the compressive strength and thermal conductivity show a downward trend with the increase in the replacement rate of recycled coarse aggregate;

[0013] The compressive strength and thermal conductivity show a downward trend with the increase in the dosage of expanded perlite.

[0014] Preferably, the preparation process of the expanded perlite recycled thermal insulation concrete includes:

[0015] Pour the expanded perlite into the mixer, and pour in half of the water and stir for 60 seconds to fully pre-wet the expanded perlite;

[0016] According to the design mix ratio, weigh the recycled aggregate and natural aggregate and pour them into the mixer and stir for 60 seconds. Finally, add the remaining water and water reducer and stir for 240 seconds;

[0017] Pour the prepared recycled thermal insulation concrete mixture into the oiled mold, place it on the vibrating table, wait until the concrete fully fills the mold, then level the surface with a trowel, cover it with a plastic film, and demold after 24 hours;

[0018] After the curing of the expanded perlite recycled thermal insulation concrete test blocks, carry out the compressive strength test and the thermal conductivity test.

[0019] Preferably, the components of the expanded perlite recycled thermal insulation concrete include:

[0020] Cement, fly ash, natural coarse aggregate, recycled coarse aggregate, fine aggregate, expanded perlite, water reducer, and water.

[0021] Preferably, the cement is P·O 42.5 ordinary Portland cement;

[0022] The fly ash is of grade II;

[0023] The natural coarse aggregate has a particle size of 4.75 mm to 20 mm;

[0024] The fine aggregate is washed sand with a fineness modulus of 3.27;

[0025] The water reducing agent is a polycarboxylate-based high-performance water reducing agent with a water reducing efficiency of 25% to 30%.

[0026] Preferably, the process for obtaining the recycled coarse aggregate includes:

[0027] After the waste concrete building structure is demolished, it is first crushed by a jaw crusher, then washed, impurities are removed, and the recycled coarse aggregate is obtained by screening;

[0028] The recycled coarse aggregate has a particle size of 4.75 mm to 20 mm and a replacement rate range of 0% to 100%.

[0029] Preferably, the water-binder ratio range is 0.45 to 0.55;

[0030] The vitrified microbead particles are closed-cell perlite with a particle size of 0.53 mm to 0.85 mm, and the dosage range is 80 kg / m 3 ~180 kg / m 3 , the bulk density is 107 kg / m 3 , the cylinder compressive strength is 197 KPa, the thermal conductivity is 0.041 W / (m·k), the volume water absorption rate is 16%, the surface vitrified closed-cell rate is 95%, and the volume floating rate is 91%.

[0031] Preferably, the process of establishing the fitting equation between factors and responses by the response surface method includes:

[0032] Establish a first regression equation for the compressive strength with respect to the water-binder ratio, the replacement rate of the recycled coarse aggregate, and the dosage of the vitrified microbeads, and establish a second regression equation for the thermal conductivity with respect to the water-binder ratio, the replacement rate of the recycled coarse aggregate, and the dosage of the vitrified microbeads.

[0033] Preferably, the formula expression of the first regression equation is:

[0034] Y1 = 233.29 - 678.6A - 0.1066B - 0.069C - 0.06AB + 0.62AC

[0035] + 0.00012BC + 540A 2 + 0.001B 2 - 0.0013C 2

[0036] The formula expression of the second regression equation is:

[0037] Y2 = 1.01943 + 0.0825A - 0.00041B - 0.002187C

[0038] Among them, Y1 is the compressive strength of the vitrified microsphere recycled thermal insulation concrete, Y2 is the thermal conductivity of the vitrified microsphere recycled thermal insulation concrete, A is the water-binder ratio, B is the replacement rate of recycled coarse aggregate, and C is the dosage of vitrified microspheres.

[0039] Compared with the prior art, the present invention has the following advantages and technical effects:

[0040] The present invention uses recycled aggregate to replace natural aggregate, reduces the usage rate of natural sand and gravel, and provides a new idea for disposing of waste concrete; adding vitrified microsphere thermal insulation aggregate reduces the thermal conductivity of concrete, increases the self-thermal insulation effect of the building on the premise of ensuring the compressive strength of the concrete, reduces building energy consumption, and reduces the expenditure required for maintaining building insulation.

[0041] The present invention establishes the relationship between the water-binder ratio, the replacement rate of recycled coarse aggregate, the dosage of vitrified microspheres and the compressive strength and thermal conductivity of the vitrified microsphere recycled thermal insulation concrete; at the same time, the optimal mix ratio is obtained and can be used for actual production applications. Description of the Drawings

[0042] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0043] Figure 1 is a schematic flow chart of the method of the embodiment of the present invention;

[0044] Figure 2 is a relationship diagram between the predicted value and the actual value of the compressive strength prediction model of the embodiment of the present invention;

[0045] Figure 3 is a 3D response surface prediction diagram of the compressive strength of the embodiment of the present invention;

[0046] Figure 4 is a relationship diagram between the predicted value and the actual value of the thermal conductivity prediction model of the embodiment of the present invention;

[0047] Figure 5 is a 3D response surface prediction diagram of the thermal conductivity of the embodiment of the present invention. Detailed Embodiments

[0048] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine the embodiments to detail this application.

[0049] It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0050] As Figures 1-5 shown, in this embodiment, a mix proportion design method for vitrified microbead recycled thermal insulation concrete is provided. On the basis of ordinary concrete, natural coarse aggregate is replaced by recycled coarse aggregate in equal mass, and at the same time, vitrified microbead particles are incorporated into the recycled concrete as thermal insulation aggregate; the response surface method is used to describe the effects of water-binder ratio, recycled coarse aggregate replacement rate, vitrified microbead content, and the interaction between them on the compressive strength and thermal conductivity of vitrified microbead recycled thermal insulation concrete; a regression prediction model is established, and expected values are assigned to the regression prediction model to obtain the maximum value of compressive strength and the minimum value of thermal conductivity, and then the optimal mix proportion of vitrified microbead recycled thermal insulation concrete is selected.

[0051] Specifically, it includes the following steps:

[0052] Step 1, determine three factors and three levels, and design the mix proportion. Select the water-binder ratio, recycled coarse aggregate replacement rate, and vitrified microbead content as the three influencing factors; the three levels are proposed as follows: water-binder ratio 0.45, 0.5, 0.55, recycled coarse aggregate replacement rate 0%, 50%, 100%, and vitrified microbead content 80 kg / m 3 、130 kg / m 3 、180 kg / m 3 ; Combine the Box-Behnken (BBD) method in the response surface method to establish the design mix proportion;

[0053] Among them, the response surface method is a mathematical statistical method that obtains an explicit functional relationship by fitting a series of experimental data, approximately expressing the relationship between factors and response values, and testing the regression model through the goodness of fit, signal-to-noise ratio, and each significant factor of the equation of the fitting equation.

[0054] Step 2, conduct two-response experiments and establish a fitting model. Take the compressive strength and thermal conductivity of the recycled thermal insulation concrete as evaluation indexes, prepare vitrified microbead recycled thermal insulation concrete test blocks according to the design mix proportion, measure their compressive strength and thermal conductivity, use the response surface method to establish a fitting equation between factors and responses, and analyze the fitting situation between predicted values and measured values;

[0055] Step 3, select the optimal mix proportion. Assign expected values to the prediction model to obtain the maximum value of compressive strength and the minimum value of thermal conductivity, select the optimal mix proportion and conduct verification.

[0056] In this embodiment, vitrified microspheres are used as thermal insulation aggregates and incorporated into recycled concrete to enhance the self-thermal insulation effect of the concrete structure while meeting its own load-bearing capacity. The response surface method is used to describe the effects of water-binder ratio, recycled coarse aggregate replacement rate, vitrified microsphere content, and the interaction between them on the compressive strength and thermal conductivity of vitrified microsphere recycled thermal insulation concrete. Through the establishment of a regression model for prediction, the optimal mix ratio is obtained.

[0057] On the one hand, this embodiment innovatively applies the mathematical statistical method - the response surface method to the field of concrete materials, obtains the optimal mix ratio of vitrified microsphere recycled thermal insulation concrete, and plays a guiding role in actual production and application. On the other hand, it saves energy and utilizes waste, helping to promote the "dual carbon" goal.

[0058] Furthermore, the compressive strength and thermal conductivity show a downward trend with the increase of the recycled coarse aggregate replacement rate, and also show a downward trend with the increase of the vitrified microsphere content.

[0059] Furthermore, the vitrified microsphere recycled thermal insulation concrete includes the following components: cement, fly ash, natural coarse aggregate, recycled coarse aggregate, fine aggregate, vitrified microspheres, water reducer, and water.

[0060] More specifically, the cement is P·O42.5 ordinary Portland cement, the fly ash grade is II, and the natural coarse aggregate particle size is 4.75mm - 20mm.

[0061] The recycled coarse aggregate is obtained by first crushing the waste concrete building structure with a jaw crusher, then washing and removing impurities. The particle size of the screened recycled aggregate is 4.75mm - 20mm, and the replacement rate range is 0% - 100%.

[0062] The fine aggregate is washed sand with a fineness modulus of 3.27. The water-binder ratio range is 0.45 - 0.55.

[0063] The water reducer is a polycarboxylate-based high-performance water reducer with a water reduction efficiency of 25% - 30%.

[0064] The vitrified microsphere particles are closed-cell perlite with a particle size of 0.53mm - 0.85mm, and the content range is 80kg / m 3 ~180kg / m 3 。The bulk density is 107kg / m 3 , the cylinder compressive strength is 197KPa, the thermal conductivity is 0.041W / (m·k), the volume water absorption rate is 16%, the surface vitrification closed-cell rate is 95%, and the volume floating rate is 91%.

[0065] Even further, the preparation method of the vitrified microsphere recycled thermal insulation concrete includes the following steps:

[0066] Step 1: Pour the vitrified microbeads into a blender, and pour in half of the water and stir well for 60 seconds to ensure that the vitrified microbeads are fully pre-wetted.

[0067] Step 2: Pour the weighed recycled aggregate, natural aggregate and various materials into the blender according to the mix ratio and stir for 60 seconds. Finally, add the remaining water and water reducer and stir for 240 seconds.

[0068] Step 3: Pour the prepared vitrified microbead recycled thermal insulation concrete mixture into an oiled mold, place it on a vibrating table, and use a trowel to level the surface after the concrete fully fills the mold. Cover it with a plastic film and remove the mold after 24 hours.

[0069] Step 4: After the curing of the vitrified microbead recycled thermal insulation concrete test block is completed, conduct a compressive strength test and a thermal conductivity test.

[0070] The factor levels and design mix ratios of the present invention are shown in Table 1 and Table 2:

[0071] Table 1

[0072]

[0073] Table 2

[0074]

[0075] The regression equation of the compressive strength in this embodiment with respect to the water-binder ratio, the replacement rate of recycled coarse aggregate and the content of vitrified microbeads is as follows:

[0076] Y1 = 233.29 - 678.6A - 0.1066B - 0.069C - 0.06AB + 0.62AC

[0077] + 0.00012BC + 540A 2 + 0.001B 2 - 0.0013C 2

[0078] The regression equation of the thermal conductivity in the present invention with respect to the water-binder ratio, the replacement rate of recycled coarse aggregate and the content of vitrified microbeads is as follows:

[0079] Y2 = 1.01943 + 0.0825A - 0.00041B - 0.002187C

[0080] Among them, Y1 is the compressive strength of the vitrified microbead recycled thermal insulation concrete, Y2 is the thermal conductivity of the vitrified microbead recycled thermal insulation concrete, A is the water-binder ratio, B is the replacement rate of recycled coarse aggregate, and C is the content of vitrified microbeads.

[0081] According to the regression equation, the relationships between the predicted values and the actual values of the compressive strength and the thermal conductivity models are respectively asFigure 1 , Figure 3 As shown, the horizontal and vertical coordinates in the figure respectively represent the actual value and the predicted value of the compressive strength. The points are evenly distributed on both sides of the diagonal line y = x, indicating that the model has a high degree of fitting with the actual situation, and the constructed model can provide accurate predictions. The response surface diagrams are respectively as Figure 2 , Figure 4 shown. Based on the fitting equation, by setting the expected compressive strength to take the maximum value and the minimum value of the thermal conductivity to predict and optimize the mix ratio, the recommended optimal mix ratio of the model can be obtained as the water-binder ratio of 0.45, the replacement rate of recycled coarse aggregate of 100%, and the dosage of expanded perlite of 135.9 kg / m 3 . The predicted thermal conductivity is 0.718 W / (m·k), and the predicted compressive strength is 40 MPa. Subsequent tests show that the error between the actual value and the predicted value of this mix ratio is within 10%.

[0082] In this embodiment, the recycled aggregate partially replaces the natural aggregate, and a new type of inorganic thermal insulation material, expanded perlite, is incorporated in a certain proportion to make expanded perlite recycled thermal insulation concrete. While meeting its own load-bearing capacity, it can enhance the self-thermal insulation effect of the concrete structure, thereby reducing the design of internal and external thermal insulation of building components, alleviating the tight supply and demand of natural aggregates, promoting the recycling of construction waste, achieving the effect of energy conservation and environmental protection, and having broad development prospects in the field of building energy conservation.

[0083] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A mix design method for vitrified microsphere regenerated thermal insulation concrete, characterized in that: include: Based on ordinary concrete, natural coarse aggregate is replaced by recycled coarse aggregate of equal quality, and vitrified microsphere particles are added to the recycled concrete as thermal insulation aggregate; The response surface methodology was used to describe the effects of water-binder ratio, recycled coarse aggregate replacement rate, glass bead content and the interaction between them on the compressive strength and thermal conductivity of glass bead recycled insulation concrete. A regression prediction model is established, and expected values ​​are assigned to the regression prediction model to obtain the maximum value of the compressive strength and the minimum value of the thermal conductivity, so as to select the optimal mix ratio of the glass bead recycled thermal insulation concrete.

2. The method according to claim 1, characterized in that The process of using response surface methodology to describe the effects of water-binder ratio, recycled coarse aggregate replacement rate, glass bead content, and the interaction between the two on the compressive strength and thermal conductivity of glass bead recycled insulation concrete includes: The water-cement ratio, recycled coarse aggregate replacement rate and vitrified microsphere dosage were selected as influencing factors; The three levels are proposed: water-cement ratio 0.45, 0.5, 0.55, recycled coarse aggregate replacement rate 0%, 50%, 100%, vitrified microsphere dosage 80kg / m 3 , 130kg / m 3 、180kg / m 3 ; The designed mix ratio was established based on the Box-Behnken method in the response surface methodology. The compressive strength and thermal conductivity of the recycled thermal insulation concrete were taken as evaluation indicators. Vitrified microsphere recycled thermal insulation concrete test blocks were prepared according to the designed mix ratio, and the compressive strength and thermal conductivity were measured. The response surface methodology was used to establish the fitting equation between the factors and the responses, and the fitting between the predicted values ​​and the measured values ​​was analyzed.

3. The method according to claim 1, characterized in that The compressive strength and thermal conductivity show a decreasing trend as the replacement rate of recycled coarse aggregate increases; The compressive strength and thermal conductivity show a downward trend as the amount of glass microspheres added increases.

4. The method according to claim 1, characterized in that: The preparation process of the vitrified microsphere regenerated thermal insulation concrete includes: Pour the vitrified microspheres into a blender, add half of the water and stir thoroughly for 60 seconds to fully pre-wet the vitrified microspheres; Pour the weighed recycled aggregate and natural aggregate into the mixer according to the designed mix ratio and stir for 60 seconds. Finally, add the remaining water and water reducer and stir for 240 seconds. Pour the prepared recycled thermal insulation concrete mixture into the oiled mold and place it on a vibration table. After the concrete fully fills the mold, smooth the surface with a spatula and cover it with a plastic film. Remove the mold after 24 hours. After the curing of the vitrified microsphere recycled insulation concrete specimens was completed, compressive strength tests and thermal conductivity tests were carried out.

5. The method according to claim 1, characterized in that The components of the vitrified microsphere regenerated thermal insulation concrete include: Cement, fly ash, natural coarse aggregate, recycled coarse aggregate, fine aggregate, vitrified microspheres, water reducing agent and water.

6. The method according to claim 5, characterized in that The cement is P·O 42.5 ordinary Portland cement; The fly ash grade is grade II; The particle size of the natural coarse aggregate is 4.75 mm to 20 mm; The fine aggregate is washed sand with a fineness modulus of 3.27; The water reducing agent is a polycarboxylic acid-based high-performance water reducing agent with a water reducing efficiency of 25% to 30%.

7. The method according to claim 5, characterized in that The process of obtaining the recycled coarse aggregate includes: After the abandoned concrete building structure is dismantled, it is first crushed by a jaw crusher, then cleaned, impurities are removed, and the recycled coarse aggregate is obtained by screening; The particle size of the recycled coarse aggregate is 4.75 mm to 20 mm, and the replacement rate ranges from 0% to 100%.

8. The method according to claim 2, characterized in that: The water-to-binder ratio ranges from 0.45 to 0.55; The vitrified microsphere particles are closed-cell perlite with a particle size of 0.53 mm to 0.85 mm and a dosage range of 80 kg / m 3 ~180kg / m 3 , bulk density is 107kg / m 3 The cylinder pressure strength is 197KPa, the thermal conductivity is 0.041W / (m·k), the volume water absorption is 16%, the surface vitrified closed porosity is 95%, and the volume floating rate is 91%.

9. The method according to claim 2, characterized in that: The process of establishing the fitting equation between factors and responses using response surface methodology includes: The first regression equation of compressive strength on water-binder ratio, replacement rate of recycled coarse aggregate and content of vitrified microspheres was established, and the second regression equation of thermal conductivity on water-binder ratio, replacement rate of recycled coarse aggregate and content of vitrified microspheres was established.

10. The method according to claim 9, characterized in that The formula expression of the first regression equation is: Y1=233.29-678.6A-0.1066B-0.069C-0.06AB+0.62AC+0.00012BC+540A 2 +0.001B 2 -0.0013C 2 The formula expression of the second regression equation is: Y2=1.01943+0.0825A-0.00041B-0.002187C Among them, Y1 is the compressive strength of vitrified microsphere recycled thermal insulation concrete, Y2 is the thermal conductivity of vitrified microsphere recycled thermal insulation concrete, A is the water-cement ratio, B is the replacement rate of recycled coarse aggregate, and C is the amount of vitrified microspheres.

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