A low-carbon concrete mix proportion design method

Abstract

This invention relates to a low-carbon concrete mix design method, specifically a mix proportioning method for building materials. Its purpose is to provide a method for designing low-carbon recycled aggregate concrete mix proportions that meet compressive strength requirements when carbon emissions per cubic meter of concrete are limited. This invention's low-carbon concrete mix design method first introduces the Bolome formula for the 28-day compressive strength of ordinary concrete and the b / W relationship. It then introduces a recycled coarse aggregate influence factor to reflect the impact of recycled coarse aggregate addition on the performance of recycled concrete. The water absorption rate of recycled coarse aggregate is considered the main influencing factor, simplifying the expression for the compressive strength of recycled aggregate concrete. The water absorption rate of recycled coarse aggregate is chosen as the single factor to represent its influence. g We constructed a fitted regression equation for the carbon emissions of recycled aggregate concrete and the replacement rate of recycled aggregate, and finally obtained a calculation formula that uses carbon emissions to represent the strength of recycled aggregate concrete.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a mechanism sand concrete mix proportion design method considering the thickness of the slurry wrapping layer. BACKGROUND

[0002] Concrete is one of the core basic materials for building a large country, and is the most widely used and largest man-made material in the national economy. According to authoritative data, the engineering construction industry accounts for more than 40% of global carbon emissions, and the consumption of resources and energy and carbon emissions in the whole life cycle of building materials are particularly prominent.

[0003] Under the background of low-carbon development of the building materials industry, the application of low-carbon concrete has become an inevitable trend, so as to strictly limit the carbon emissions of concrete. For single concrete, there is currently a lack of a low-carbon recycled aggregate concrete mix proportion design method that meets the compressive strength requirement when limiting the carbon emissions of single concrete, so as to guide the design of the mix proportion of low-carbon recycled aggregate concrete that meets the compressive strength requirement. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a low-carbon concrete mix proportion design method that meets the compressive strength requirement, for solving the problem of designing the mix proportion of low-carbon recycled aggregate concrete that meets the compressive strength when limiting the carbon emissions of single concrete.

[0005] The present application is a low-carbon concrete mix proportion design method, which designs the concrete mix proportion according to the requirement of carbon emission limitation, including the following steps:

[0006] S10, introducing the Bolognini calculation formula of the relationship between the 28-day compressive strength of ordinary concrete and b / W:

[0007]

[0008] In the formula, f0 is the compressive strength of ordinary concrete; f ce is the strength of cementitious materials; A and B are linear regression coefficients of ordinary concrete; b is the amount of cementitious materials; and W is the water consumption of ordinary concrete mixture.

[0009] S20, the recycled aggregate concrete is a composite material, in which ordinary concrete is used as a base phase, and recycled coarse aggregate is used as a negative reinforcing phase. The influence factor a g of recycled coarse aggregate is introduced to reflect the influence of the addition of recycled coarse aggregate on the performance of recycled concrete, and the calculation formula of the compressive strength of recycled aggregate concrete is obtained:

[0010] f Rg = f0(1-ag λ g )=Af ce (b / WB)(1-α g λ g )

[0011] In the formula, f0 is the compressive strength of ordinary concrete; f ce For the strength of cementitious materials; α g λ is the influencing factor of recycled coarse aggregate. g denoted as , where b is the replacement rate of recycled aggregate; b is the amount of cementitious materials used; W is the water consumption of ordinary concrete mixture; A and B are the linear regression coefficients of ordinary concrete.

[0012] For S30, the influence of various performance indicators of recycled coarse aggregate on its influencing factors varies significantly. The correlation is as follows: water absorption rate has the highest influence, followed by apparent density, and then crushing index has the lowest. Based on the differences in the influence of various performance indicators of recycled coarse aggregate on its influencing factors, water absorption rate is considered the main influencing factor. The expression for the compressive strength of recycled aggregate concrete is simplified, and the water absorption rate ω of recycled coarse aggregate is selected as the primary influencing factor. a This single factor is used to represent its influence factor α. g The water absorption rate ω of recycled coarse aggregate a Its influence factor α g Relationship:

[0013] α g =7.607ω a -0.074

[0014] Thus, considering the quality of recycled coarse aggregate, the relationship between the compressive strength of recycled concrete and the replacement rate of recycled aggregate can be obtained as follows:

[0015] f Rg =Af ce (b / WB)[1-(7.607ω a -0.074)λ g ]

[0016] S40, construct a fitted regression equation for the carbon emissions of recycled aggregate concrete and the replacement rate of recycled aggregate:

[0017] C Rg =-16.62λ g +329.17

[0018] Right now

[0019] This equation can be adjusted according to changes in the quality of the recycled aggregate itself. By substituting the replacement rate of the recycled aggregate into the relationship between the compressive strength of recycled concrete and the replacement rate, a formula for calculating the strength of recycled aggregate concrete in terms of carbon emissions is obtained:

[0020]

[0021] In the formula: C Rg Carbon emissions per cubic meter of recycled aggregate concrete, expressed in kgCO2 / m³ 3 ;f ce b represents the strength of the cementitious material, in MPa; b represents the amount of cementitious material used in ordinary concrete, in kg / m³. 3 W represents the water content of ordinary concrete mixture, in kg / m³. 3 ;ω a , where is the water absorption rate of recycled coarse aggregate, as a percentage; A and B are the linear regression coefficients of ordinary concrete;

[0022] S50, according to the "Specification for Mix Proportion Design of Ordinary Concrete" (JGJ 55-2011), the cement-water ratio b / W in the formula for calculating the compressive strength of recycled aggregate concrete is calculated. ω is obtained based on experimental testing of the recycled aggregate used. a The amount of mineral admixtures, i.e., coarse and fine aggregates, in low-carbon recycled aggregate concrete is determined by the following formula:

[0023] When calculating the amount of coarse and fine aggregates using the mass method, the following formula should be used:

[0024] m fo +m co +m go +m so +m wo =m cp

[0025]

[0026] Where: m f0 The amount of cement used per cubic meter of concrete, expressed in kg; m Rg The mass of recycled aggregate concrete is expressed in kg; m g0 Total coarse aggregate usage per cubic meter of concrete, in kg; m s0 The amount of fine aggregate per cubic meter of concrete, expressed in kg; m w0 Water consumption per cubic meter of concrete, expressed in kg; β s Sand ratio, percentage; m cp This is the assumed mass of concrete mixture per cubic meter, expressed in kg, and can be taken as 2350-2450 kg.

[0027] When the volume method is used to calculate the amount of coarse and fine aggregates, the following formula should be used:

[0028]

[0029] In the formula, ρ c is the density of cement, ρ f is the density of mineral admixtures, with the unit of kg / m 3 , which should be determined according to the “Cement Density Determination Method” (GB / T 208-2014), ρ c may also be 2900-3100 kg / m 3 ; ρ g is the apparent density of coarse aggregate, ρ s is the apparent density of fine aggregate, with the unit of kg / m 3 , which should be determined according to the current industry standard “Standard for Quality and Testing Methods of Sand and Stone for Ordinary Concrete” (JGJ 52-2006); ρ w is the density of water, with the unit of kg / m 3 , which may be 1000 kg / m 3 ; and α is the air content of concrete, in percentage, which may be 1 when no air-entraining admixtures are used.

[0030] The low-carbon concrete mix proportion design method of the application, wherein the replacement rate of the recycled aggregate is 0-100%.

[0031] The low-carbon concrete mix proportion design method of the application, wherein the fly ash content in the cementitious material is in the range of 0-15%.

[0032] The low-carbon concrete mix proportion design method of the application, wherein the mineral powder content in the cementitious material is in the range of 0-20%.

[0033] The low-carbon concrete mix proportion design method of the application, wherein the silica fume content in the cementitious material is in the range of 0-10%.

[0034] The low-carbon concrete mix proportion design method of the application is different from the prior art in that the low-carbon concrete mix proportion design method of the application can meet the requirements of low-carbon recycled aggregate concrete mix proportion on the compressive strength of concrete when limiting the carbon emission of single concrete. DETAILED DESCRIPTION

[0035] The following examples are used to illustrate the application, but not to limit the scope of the application.

[0036] The application provides a design method of low-carbon concrete mix proportion under the condition of considering carbon emission limitation, and the following selects different carbon emissions to design the low-carbon concrete mix proportion, selects P·O 42.5 grade Portland cement, the density is 3000kg / m 3 ; grade II fly ash, the density is 2000kg / m 3 ; high-performance water reducing agent, the density is approximately 1000kg / m 3 ; Hubei 5-31.5mm continuous gradation macadam, the density is 2720kg / m 3 , the water demand rate is 0; Shanghai 5-31.5mm continuous gradation macadam of recycled coarse aggregate, the water absorption rate is 3.0%, the density is 2420kg / m 3 ; machine-made sand, the density is 2630kg / m 3 .

[0037] Taking C30 concrete as an example, low-carbon recycled aggregate concrete is designed according to different carbon emission limitation requirements.

[0038] Comparative example 1

[0039] C30 ordinary concrete with a single carbon emission of 329.17kgCO2 / m 3 is designed.

[0040] Step 1, the compressive strength of C30 ordinary concrete is calculated according to the carbon emission, and the carbon emission is brought into the following calculation formula:

[0041]

[0042] The compressive strength formula is obtained as:

[0043]

[0044] Step 2, the cement-water ratio b / W is obtained according to the calculation process in the 'Ordinary Concrete Mix Proportion Design Regulation' (JGJ 55-2011):

[0045]

[0046] The final cement-water ratio is 1.825.

[0047] Step 3, the cement-water ratio is brought into the compressive strength calculation formula, and the compressive strength is obtained as 42.29Mpa, which meets the compressive strength requirement of C30 ordinary concrete.

[0048] Step 4, according to the above calculation, the water-cement ratio is 1.825, and the water-cement ratio is 0.55. According to the "Ordinary Concrete Mix Design Regulation" (JGJ 55-2011), the water amount is selected as 222.5 kg, the total amount of cementitious materials is 404.5 kg, the fly ash replacement rate is selected as 15%, the mineral powder is 10%, the fly ash amount is 60.7 kg, the mineral powder amount is 40.5 kg, and the cement amount is 303.3 kg.

[0049] Step 5, the amount of coarse and fine aggregate is calculated by mass method, and the assumed mass of each cubic meter of concrete mixture is 2400 kg / m 3 , which should be calculated according to the following formula:

[0050] m fo +m co +m go +m so +m wo =m cp

[0051]

[0052] According to the "Ordinary Concrete Mix Design Regulation" (JGJ 55-2011), the sand rate is selected as 36%, and the amount of ordinary crushed stone is obtained as 1134.8 kg, and the amount of machine-made sand is 638.2 kg.

[0053] According to the amount of each raw material calculated in Comparative Example 1, the concrete is mixed and formed according to the standards of GB / T50080-2016, GB / T50081-2019 and GB / T 50082-2009, and the expansion and slump are tested, and the compressive strength test is carried out after curing to the corresponding age.

[0054] Example 1

[0055] The design of single carbon emission of C30 low-carbon recycled aggregate concrete is 323.1 kgCO2 / m 3 .

[0056] Step 1, according to the carbon emission to calculate the compressive strength of C30 low-carbon recycled aggregate concrete, the carbon emission is brought into the following calculation formula:

[0057]

[0058] The compressive strength formula is:

[0059]

[0060] Step 2, according to the calculation process in the Design Standard for Normal Concrete Mix Proportion (JGJ 55-2011), the water-cement ratio b / W is obtained:

[0061]

[0062] The final water-cement ratio is 1.825.

[0063] Step 3, the water-cement ratio is brought into the compressive strength calculation formula, and the compressive strength is 40.12 MPa, which meets the compressive strength requirement of C30 normal concrete.

[0064] Step 4, according to the above calculation, the water-cement ratio is 1.825, and the water-cement ratio is 0.55. According to the Design Standard for Normal Concrete Mix Proportion (JGJ 55-2011), the water amount is selected as 222.5 kg, the total amount of cementitious materials is 404.5 kg, the fly ash replacement rate is selected as 15%, the mineral powder is 10%, the fly ash amount is 60.7 kg, the mineral powder amount is 40.5 kg, and the cement amount is 303.3 kg.

[0065] Step 5, the mass method is used to calculate the amount of coarse and fine aggregate, and the assumed mass of each cubic meter of concrete mixture is 2400 kg / m 3 , which should be calculated according to the following formula:

[0066] m fo +m co +m go +m so +m wo =m cp

[0067]

[0068] According to the Design Standard for Normal Concrete Mix Proportion (JGJ 55-2011), the sand rate is selected as 36%, and the amount of ordinary crushed stone is obtained as 720.3 kg, the amount of recycled crushed stone is 414.5 kg, and the amount of machine-made sand is 638.2 kg.

[0069] According to the amount of each raw material calculated in Example 1, the concrete is mixed and formed according to the standards of GB / T50080-2016, GB / T50081-2019 and GB / T 50082-2009, and the expansion and slump are tested, and the compressive strength test is carried out after curing to the corresponding age.

[0070] Example 2

[0071] Design C30 low-carbon recycled aggregate concrete with single-party carbon emission of 316 kgCO2 / m 3 .

[0072] Step 1, calculate the compressive strength of C30 low carbon concrete according to carbon emissions, and bring the carbon emissions into the following calculation formula:

[0073]

[0074] The compressive strength formula is obtained as:

[0075]

[0076] Step 2, according to the calculation process in "Ordinary Concrete Mix Design Regulation" (JGJ 55-2011), the water-cement ratio b / W is obtained:

[0077]

[0078] The final water-cement ratio is 1.825.

[0079] Step 3, substitute the water-cement ratio into the compressive strength calculation formula, and the compressive strength is 37.27 MPa, which meets the compressive strength requirements of C30 ordinary concrete.

[0080] Step 4, according to the above calculation, the water-cement ratio is 1.743, and the water-cement ratio is 0.55. According to "Ordinary Concrete Mix Design Regulation" (JGJ 55-2011), the water consumption is selected as 222.5 kg, the total amount of cementitious materials is 387.8 kg, the fly ash replacement rate is selected as 15%, the fly ash consumption is 58.2 kg, and the cement consumption is 329.6 kg.

[0081] Step 5, when calculating the amount of coarse and fine aggregate by mass method, the assumed mass of each cubic meter of concrete mixture is 2400 kg / m 3 , which should be calculated according to the following formula:

[0082] m fo +m co +m go +m so +m wo =m cp

[0083]

[0084] According to "Ordinary Concrete Mix Design Regulation" (JGJ 55-2011), the sand rate is selected as 36%, and the amount of ordinary crushed stone is obtained as 235.6 kg, the amount of recycled crushed stone is 899.2 kg, and the amount of machine-made sand is 638.2 kg.

[0085] The amount of each raw material calculated according to the calculation in Example 2 is proportioned, and the concrete is mixed and formed according to the standards of GB / T50080-2016, GB / T50081-2019 and GB / T 50082-2009, the spread and slump are tested, and the compressive strength test is carried out after curing to the corresponding age.

[0086] Example 3

[0087] The design single carbon emission of C30 low-carbon recycled aggregate concrete is 312.55 kgCO2 / m 3 .

[0088] Step 1, calculate the compressive strength of C30 low-carbon concrete according to carbon emission, and bring the carbon emission into the following calculation formula:

[0089]

[0090] The compressive strength formula is:

[0091]

[0092] Step 2, according to the calculation process in the “Code for Design of Normal Concrete Mix Proportion” (JGJ 55-2011), the water-cement ratio b / W is obtained:

[0093]

[0094] The final water-cement ratio is 1.825.

[0095] Step 3, substitute the water-cement ratio into the compressive strength calculation formula, and the compressive strength is 35.92 MPa, which meets the compressive strength requirement of C30 ordinary concrete.

[0096] Step 4, according to the above calculation, the water-cement ratio is 1.825, so the water-cement ratio is 0.55. According to the “Code for Design of Normal Concrete Mix Proportion” (JGJ 55-2011), the water amount is selected as 222.5 kg, the total amount of cementitious materials is 387.8 kg, the fly ash replacement rate is selected as 15%, the fly ash amount is 58.2 kg, and the cement amount is 329.6 kg.

[0097] Step 5, the amount of coarse and fine aggregate is calculated by mass method, the assumed mass of each cubic meter of concrete mixture is 2400 kg / m 3 , which should be calculated according to the following formula:

[0098] m fo +m co +m go +m so +m wo =mcp

[0099]

[0100] According to the sand rate selected as 36% in the General Concrete Mix Design Regulation (JGJ 55-2011), the amount of recycled gravel is 1145.4 kg, and the amount of machine-made sand is 644.3 kg.

[0101] The amount of each raw material calculated in Example 3 is proportioned, and the concrete is mixed and formed according to the standards of GB / T50080-2016, GB / T50081-2019 and GB / T 50082-2009, the expansion degree and the slump degree are tested, and the compressive strength test is carried out after curing to the corresponding age.

[0102] The data obtained in Comparative Example 1 and Examples 1-3 are arranged to obtain the following table.

[0103]

[0104] Comparing Examples 1-3 with Comparative Example 1, it can be found that the strength of the low-carbon recycled aggregate concrete prepared by the method provided by the application meets the requirements of the relevant standards under different carbon emissions, which illustrates the feasibility of the method provided by the application. The method provided by the application can solve the problem of meeting the requirements of the compressive strength of the low-carbon recycled aggregate concrete mix on the concrete under the limitation of the carbon emission of the single concrete.

[0105] Although the application has been described in detail in the foregoing general description and examples, modifications and improvements to the application will occur to those skilled in the art. These modifications and improvements are within the scope of the application, which is not intended to be limited to the embodiments disclosed herein, but is to be accorded the full scope of the claims to follow.

Claims

1. A method for mix proportion design of low-carbon concrete, characterized in that: Designing the concrete mix proportion according to the requirement of carbon emission limit, comprising the following steps: S10, introducing the Bowermi calculation formula of the relationship between the 28-day compressive strength of ordinary concrete and b / W: In the formula, f0 is the compressive strength of ordinary concrete; f ce is the strength of the cementitious material; A, B are linear regression coefficients of ordinary concrete; b is the amount of cementitious material; and W is the water content of the ordinary concrete mixture. S20, in recycled aggregate concrete, ordinary concrete is used as the base phase, and recycled coarse aggregate is used as the negative reinforcing phase, and by introducing the recycled coarse aggregate influencing factor α g to reflect the influence of the addition of recycled coarse aggregate on the performance of recycled concrete, and the compressive strength calculation formula of recycled aggregate concrete is obtained. f Rg = f0(1 - a g λ g ) = Af ce (b / W - B)(1 - a g λ g ) In the formula, α g is a recycled coarse aggregate influence factor; λ g is a replacement rate of recycled aggregate; S30, the main influencing factor of the water absorption rate of the recycled coarse aggregate, simplifies the expression of the compressive strength of recycled aggregate concrete, selects the water absorption rate ω of the recycled coarse aggregate a This single factor to represent its influence factor α g , wherein the water absorption rate ω of the recycled coarse aggregate a And its influence factor α g The relationship formula: a g = 7.607 ω a -0.074 Then the relationship formula between the compressive strength of recycled concrete and the replacement rate of recycled aggregate is: f Rg = Af ce (b / W-B)[1-(7.607ω a -0.074)λ g ] S40, constructing the fitting regression equation of the carbon emission of recycled aggregate concrete and the replacement rate of recycled aggregate: C Rg = -16.62λ g + 329.17 That is where C Rg For the carbon emissions of single-component recycled aggregate concrete, the replacement rate of recycled aggregate is brought into the relationship between the compressive strength of recycled concrete and the replacement rate of recycled aggregate, and the calculation formula of recycled aggregate concrete strength represented by carbon emissions is obtained: S50, the water-cement ratio b / W in the calculation formula of the compressive strength of the recycled aggregate concrete is calculated according to the “Mix Proportion Design Regulation for Common Concrete” (JGJ 55-2011), and ω is obtained by testing the recycled aggregate used a , the amounts of the coarse and fine aggregates of the low-carbon recycled aggregate concrete are calculated according to the mass method or the volume method.

2. The method for mix proportion design of low-carbon concrete according to claim 1, characterized in that: The mass method should be calculated according to the following formula: m fo +m co +m go +m so +m wo =m cp wherein: m f0 is the cement content per cubic meter of concrete; m Rg is the mass of recycled aggregate concrete; m g0 is the total coarse aggregate content per cubic meter of concrete; m s0 is the fine aggregate content per cubic meter of concrete; m w0 is the water content per cubic meter of concrete; β s is the sand ratio; m cp is the assumed mass of the concrete mix per cubic meter.

3. The method according to claim 2, characterized in that: The assumed mass of each cubic meter of concrete mixture ranges from 2350 to 2450 kg.

4. The method for mix proportion design of low-carbon concrete according to claim 1, characterized in that: The volume method should be calculated according to the following formula: In the formula; p c is the cement density, p f is the mineral admixture density, which shall be determined according to the “Cement Density Determination Method” (GB / T 208-2014); p g is the apparent density of coarse aggregate, p s is the apparent density of fine aggregate, which shall be determined according to the current industry standard “Standard for Quality and Test Methods of Sand and Stone for Ordinary Concrete” (JGJ 52-2006); p w is the density of water; and a is the air content of the concrete.

5. The method for mix proportion design of low-carbon concrete according to claim 4, characterized in that: The cement density is in the range of 2900-3100 kg / m 3 .

6. The method for mix proportion design of low-carbon concrete according to claim 4, characterized in that: When not using air-entraining admixtures, the value of the air content of the concrete is 1.

7. The method for mix proportion design of low-carbon concrete according to claim 1, characterized in that: The replacement rate of the recycled aggregate is 0-100%.

8. The method for mix proportion design of low-carbon concrete according to claim 1, characterized in that: The fly ash content in the cementitious material ranges from 0 to 15%.

9. The method for mix proportion design of low-carbon concrete according to claim 1, characterized in that: The mineral powder content in the cementitious material ranges from 0 to 20%.

10. The method for mix proportion design of low-carbon concrete according to claim 1, characterized in that: The silica fume content in the cementitious material ranges from 0 to 10%.

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