Low-carbon concrete mix proportion design method

Abstract

The invention discloses a low-carbon concrete mix proportion design method, and relates to a mix proportion method for building materials. The invention aims to provide a method for designing the mix proportion of the low-carbon recycled aggregate concrete meeting the requirement of compressive strength when carbon emission of the concrete per cubic meter is limited. The low-carbon concrete mix proportion design method comprises the following steps: firstly, introducing a Boromi calculation formula of a relationship between 28-day compressive strength of common concrete and b / W, introducing a recycled coarse aggregate influence factor to reflect the influence of the doping of the recycled coarse aggregate on the performance of the recycled concrete, and taking the water absorption rate of the recycled coarse aggregate as a main influence factor of the influence factor; the method comprises the following steps: simplifying an expression of compressive strength of recycled aggregate concrete, selecting a single factor of water absorption of recycled coarse aggregate to represent an influence factor g of the recycled coarse aggregate, constructing a fitting regression equation of carbon emission of the recycled aggregate concrete and a substitution rate of the recycled aggregate, and finally obtaining a calculation formula of representing the strength of the recycled aggregate concrete by using the carbon emission.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a method for designing the mix ratio of machine-made sand concrete taking into account the thickness of a slurry coating layer. Background Art

[0002] Concrete is one of the core basic materials for building a great construction country. It is also the largest building material in the world so far. It is the most widely used and largest man-made material in the national economy and people's livelihood. According to authoritative data, the engineering construction industry accounts for more than 40% of global carbon emissions, among which the consumption of resources and energy by building materials and their carbon emissions throughout their life cycle are particularly prominent.

[0003] In the context of low-carbon development in the building materials industry, the application of low-carbon concrete has become an inevitable trend, so that the carbon emissions of concrete can be strictly limited. For single cubic meter concrete, when limiting the carbon emissions of single cubic meter concrete, there is currently a lack of a low-carbon recycled aggregate concrete mix design method that meets the compressive strength requirements, and thus it is impossible to guide the design of the mix ratio of low-carbon recycled aggregate concrete based on meeting the compressive strength requirements. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a low-carbon concrete mix ratio design method that meets the compressive strength requirements, which is used to solve the problem of designing the mix ratio of low-carbon recycled aggregate concrete that meets the compressive strength when limiting the carbon emissions of a single cubic meter of concrete.

[0005] The present invention provides a low-carbon concrete mix design method, which designs a concrete mix according to the requirement of carbon emission limit, and comprises the following steps:

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

[0007]

[0008] Where f0 is the compressive strength of ordinary concrete; f ce is the strength of cementitious materials; A and B are the linear regression coefficients of ordinary concrete; b is the amount of cementitious materials; W is the amount of water used in ordinary concrete mixture;

[0009] S20, recycled aggregate concrete is a composite material, in which ordinary concrete is used as the base phase and recycled coarse aggregate is used as the negative reinforcement phase. By introducing the influence factor α of recycled coarse aggregate g To reflect the effect of adding recycled coarse aggregate on the performance of recycled concrete, the calculation formula for the compressive strength of recycled aggregate concrete is obtained:

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

[0011] Where f0 is the compressive strength of ordinary concrete; f ce is the strength of the cementitious material; α g is the impact factor of recycled coarse aggregate; g is the replacement rate of recycled aggregate; b is the amount of cementitious material; W is the water consumption of ordinary concrete mixture; A and B are the linear regression coefficients of ordinary concrete;

[0012] S30, the degree of influence of each performance index of recycled coarse aggregate on its influencing factor is very different, and the correlation is that water absorption is the largest, apparent density is the second, and crushing index is the smallest. According to the difference in the degree of influence of each performance index of recycled coarse aggregate on its influencing factor, the water absorption of recycled coarse aggregate is the main influencing factor of the influencing factor, and the expression of the compressive strength of recycled aggregate concrete is simplified. The water absorption rate of recycled coarse aggregate ω is selected a This single factor represents its impact factor α g , where the water absorption rate of recycled coarse aggregate ω a Its impact factor α g The relationship is:

[0013] α g =7.607ω a -0.074

[0014] In this way, the relationship between the compressive strength of recycled concrete and the replacement rate of recycled aggregate can be obtained based on the quality of recycled coarse aggregate:

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

[0016] S40, construct the fitting regression equation of carbon emission of recycled aggregate concrete and the replacement rate of recycled aggregate:

[0017] C Rg =-16.62λ g +329.17

[0018] Right now

[0019] The equation can be adjusted according to the change of the quality of the recycled aggregate itself. By bringing the replacement rate of the recycled aggregate into the relationship between the compressive strength of the recycled concrete and the replacement rate, the calculation formula that uses carbon emissions to represent the strength of the recycled aggregate concrete is obtained:

[0020]

[0021] Where: C Rg Carbon emissions per cubic meter of recycled aggregate concrete, in kgCO2 / m 3 ;f ce is the strength of cementitious materials, in MPa; b is the amount of cementitious materials used in ordinary concrete, in kg / m 3 ; W is the water consumption of ordinary concrete mixture, unit is kg / m 3 ;ω a is the water absorption rate of recycled coarse aggregate, in percentage; A and B are the linear regression coefficients of ordinary concrete;

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

[0023] When the mass method is used to calculate the amount of coarse and fine aggregates, 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 cement consumption per cubic meter of concrete, in kg; m Rg is the mass of recycled aggregate concrete, in kg; m g0 The total amount of coarse aggregate per cubic meter of concrete, in kg; m s0 The amount of fine aggregate per cubic meter of concrete, in kg; m w0 The amount of water per cubic meter of concrete, in kg; s is the sand ratio, percentage; m cp is the assumed mass of concrete mixture per cubic meter, in kg, which can be 2350-2450kg;

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

[0028]

[0029] Where: c is the cement density, ρ f is the density of mineral admixture, in kg / m 3 , should be determined according to the "Determination Method of Cement Density" (GB / T 208-2014), ρ c 2900-3100kg / m 3 ρ g is the apparent density of coarse aggregate, ρ s is the apparent density of fine aggregate, in kg / m 3 , should be measured according to the current industry standard "Standard for Quality and Inspection Methods of Sand and Stone for Ordinary Concrete" (JGJ 52-2006); ρ w is the density of water in kg / m 3 , can be 1000kg / m 3 ; α is the air content of concrete, in percentage. When no air-entraining admixture is used, α can be taken as 1.

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

[0031] The invention discloses a low-carbon concrete mix ratio design method, wherein the fly ash content in the cementitious material is within a range of 0 to 15%.

[0032] The invention discloses a low-carbon concrete mix ratio design method, wherein the mineral powder content in the cementitious material is within a range of 0 to 20%.

[0033] The invention discloses a low-carbon concrete mix ratio design method, wherein the silica fume content in the cementitious material is within a range of 0-10%.

[0034] The low-carbon concrete mix design method of the present invention is different from the prior art in that the low-carbon concrete mix design method of the present invention can meet the requirements of the low-carbon recycled aggregate concrete mix for concrete compressive strength while limiting the carbon emissions of a single cubic meter of concrete. DETAILED DESCRIPTION

[0035] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0036] The present invention provides a design method for a low-carbon concrete mix ratio under the condition of limiting carbon emissions. The following selects different carbon emissions to carry out low-carbon concrete mix ratio design, and selects P·O 42.5 grade silicate cement with a density of 3000kg / m 3 ; Grade II fly ash, density 2000kg / m 3 ; High performance water reducing agent, density is similar to water 1000kg / m 3 ; 5-31.5mm continuous graded crushed stone produced in Hubei, density 2720kg / m 3 , water requirement is 0; Shanghai produced recycled coarse aggregate 5-31.5mm continuous graded crushed stone, water absorption rate is 3.0%, density is 2420kg / m 3 ; Artificial sand, density is 2630kg / m 3 .

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

[0038] Comparative Example 1

[0039] The designed carbon emission per cubic meter is 329.17kgCO2 / m 3 C30 ordinary concrete.

[0040] Step 1: Calculate the compressive strength of C30 ordinary concrete based on carbon emissions, and substitute carbon emissions into the following calculation formula:

[0041]

[0042] The compressive strength formula is:

[0043]

[0044] Step 2: Obtain the ash-water ratio b / W according to the calculation process in the "Ordinary Concrete Mix Design Formula Code" (JGJ 55-2011):

[0045]

[0046] The final gray-water ratio was 1.825.

[0047] Step 3, substituting the ash-water ratio into the compressive strength calculation formula, the compressive strength is obtained to be 42.29 MPa, which meets the compressive strength requirements of C30 ordinary concrete.

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

[0049] Step 5: Calculate the amount of coarse and fine aggregate using the mass method. The assumed mass of concrete mixture per cubic meter is 2400 kg / m 3 , 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 Code" (JGJ 55-2011), the sand ratio is selected as 36%, the amount of ordinary crushed stone is 1134.8 / kg, and the amount of machine-made sand is 638.2kg.

[0053] The proportions of the raw materials were calculated according to the comparative example 1, and then the concrete was mixed and formed according to the standards of GB / T50080-2016, GB / T50081-2019 and GB / T 50082-2009, and the expansion and slump were tested. After curing to the corresponding age, the compressive strength test was carried out.

[0054] Example 1

[0055] The designed carbon emission per cubic meter is 323.1kgCO2 / m 3 C30 low carbon recycled aggregate concrete.

[0056] Step 1: Calculate the compressive strength of C30 low-carbon recycled aggregate concrete based on carbon emissions, and substitute carbon emissions into the following calculation formula:

[0057]

[0058] The compressive strength formula is:

[0059]

[0060] Step 2: Obtain the ash-water ratio b / W according to the calculation process in the "Ordinary Concrete Mix Design Formula Code" (JGJ 55-2011):

[0061]

[0062] The final gray-water ratio was 1.825.

[0063] Step 3, substituting the ash-water ratio into the compressive strength calculation formula, the compressive strength is obtained to be 40.12MPa, which meets the compressive strength requirements of C30 ordinary concrete.

[0064] Step 4, according to the above calculation, the ash-water ratio is 1.825, and the water-cement ratio is 0.55. According to the "Ordinary Concrete Mix Design Formula Code" (JGJ 55-2011), the water dosage is selected as 222.5kg, the total cementitious material dosage is 404.5kg, the fly ash replacement rate is selected as 15%, the mineral powder is 10%, the fly ash dosage is 60.7kg, the mineral powder dosage is 40.5kg, and the cement dosage is 303.3kg.

[0065] Step 5: Calculate the amount of coarse and fine aggregate using the mass method. The assumed mass of concrete mixture per cubic meter is 2400 kg / m 3 , 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 "Specifications for Design of Ordinary Concrete Mix" (JGJ 55-2011), the sand ratio is selected to be 36%, and the amount of ordinary crushed stone is 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] The proportions of the raw materials were calculated according to Example 1, and then the concrete was mixed and formed according to the standards of GB / T50080-2016, GB / T50081-2019 and GB / T 50082-2009, and the expansion and slump were tested. After curing to the corresponding age, the compressive strength test was carried out.

[0070] Example 2

[0071] The designed carbon emission per cubic meter is 316kgCO2 / m 3 C30 low carbon recycled aggregate concrete.

[0072] Step 1: Calculate the compressive strength of C30 low-carbon concrete based on carbon emissions, and substitute carbon emissions into the following calculation formula:

[0073]

[0074] The compressive strength formula is:

[0075]

[0076] Step 2: Obtain the ash-water ratio b / W according to the calculation process in the "Ordinary Concrete Mix Design Formula Code" (JGJ 55-2011):

[0077]

[0078] The final gray-water ratio was 1.825.

[0079] Step 3, substituting the ash-water ratio into the compressive strength calculation formula, the compressive strength is obtained to be 37.27 MPa, which meets the compressive strength requirements of C30 ordinary concrete.

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

[0081] Step 5: When using the mass method to calculate the amount of coarse and fine aggregate, the assumed mass of each cubic meter of concrete mixture is 2400kg / m 3 , 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 the "Ordinary Concrete Mix Design Code" (JGJ 55-2011), the sand ratio is selected to be 36%, and the amount of ordinary crushed stone is 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 proportions of the raw materials were calculated according to Example 2, and then the concrete was mixed and formed according to the standards of GB / T50080-2016, GB / T50081-2019 and GB / T 50082-2009, and the expansion and slump were tested. After curing to the corresponding age, the compressive strength test was carried out.

[0086] Example 3

[0087] The designed carbon emission per cubic meter is 312.55kgCO2 / m 3 C30 low carbon recycled aggregate concrete.

[0088] Step 1: Calculate the compressive strength of C30 low-carbon concrete based on carbon emissions, and substitute carbon emissions into the following calculation formula:

[0089]

[0090] The compressive strength formula is:

[0091]

[0092] Step 2: Obtain the ash-water ratio b / W according to the calculation process in the "Ordinary Concrete Mix Design Formula Code" (JGJ 55-2011):

[0093]

[0094] The final gray-water ratio was 1.825.

[0095] Step 3, substituting the ash-water ratio into the compressive strength calculation formula, the compressive strength is obtained to be 35.92 MPa, which meets the compressive strength requirements of C30 ordinary concrete.

[0096] Step 4, according to the above calculation, the ash-water ratio is 1.825, and the water-cement ratio is 0.55. According to the "Ordinary Concrete Mix Design Formula Code" (JGJ 55-2011), the water dosage is selected as 222.5kg, the total cementitious material dosage is 387.8kg, the fly ash replacement rate is selected as 15%, the fly ash dosage is 58.2kg, and the cement dosage is 329.6kg.

[0097] Step 5: Calculate the amount of coarse and fine aggregate using the mass method. The assumed mass of concrete mixture per cubic meter is 2400 kg / m 3 , 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 "Specifications for Design of Ordinary Concrete Mix" (JGJ 55-2011), the sand ratio is selected to be 36%, the amount of ordinary recycled crushed stone is 1145.4 kg, and the amount of machine-made sand is 644.3 kg.

[0101] The proportions of the raw materials were calculated according to Example 3, and then the concrete was mixed and formed according to the standards of GB / T50080-2016, GB / T50081-2019 and GB / T 50082-2009, and the expansion and slump were tested. After curing to the corresponding age, the compressive strength test was carried out.

[0102] The following table can be obtained by arranging the data obtained in Comparative Example 1 and Examples 1-3.

[0103]

[0104] By comparing Examples 1-3 with Comparative Example 1, it can be found that the strength of low-carbon recycled aggregate concrete with different carbon emissions prepared by the method provided by the present invention meets the requirements of relevant standards, indicating the feasibility of the method provided by the present invention. The method provided by the present invention can solve the problem of meeting the requirements of low-carbon recycled aggregate concrete mix ratio for concrete compressive strength when limiting the carbon emissions of a single cubic meter of concrete.

[0105] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A low-carbon concrete mix design method, characterized in that: Designing concrete mixes based on carbon emission limits involves the following steps: S10, introduce the Borromi calculation formula of the relationship between the 28-day compressive strength of ordinary concrete and b / W: Where f0 is the compressive strength of ordinary concrete; f ce is the strength of cementitious materials; A and B are the linear regression coefficients of ordinary concrete; b is the amount of cementitious materials; W is the amount of water used in ordinary concrete mixture; S20, in recycled aggregate concrete, ordinary concrete is used as the base phase, recycled coarse aggregate is used as the negative reinforcement phase, and the impact factor α of recycled coarse aggregate is introduced. g To reflect the effect of adding recycled coarse aggregate on the performance of recycled concrete, the calculation formula for the compressive strength of recycled aggregate concrete is obtained: f Rg =f0(1-a g l g )=Af ce (b / WB)(1-a) g l g ) In the formula, α g is the impact factor of recycled coarse aggregate; g is the replacement rate of recycled aggregate; S30, taking the water absorption rate of recycled coarse aggregate as the main influencing factor, simplifying the expression of the compressive strength of recycled aggregate concrete, and selecting the water absorption rate of recycled coarse aggregate ω a This single factor represents its impact factor α g , where the water absorption rate of recycled coarse aggregate ω a Its impact factor α g The relationship is: a g =7.607h a -0.074 The relationship between the compressive strength of recycled concrete and the replacement rate of recycled aggregate is: f Rg =Af ce (b / WB)[1-(7.607h a -0.074)l g ] S40, construct the fitting regression equation of carbon emission of recycled aggregate concrete and the replacement rate of recycled aggregate: C Rg =-16.62l g +329.17 Right now Where C Rg The carbon emissions per cubic meter of recycled aggregate concrete are calculated by substituting the replacement rate of recycled aggregate into the relationship between the compressive strength of recycled concrete and the replacement rate of recycled aggregate to obtain the calculation formula that uses carbon emissions to represent the strength of recycled aggregate concrete: S50, according to the "Ordinary Concrete Mix Design Code" (JGJ 55-2011), the lime-water ratio b / W in the calculation formula of the compressive strength of recycled aggregate concrete is calculated, and the ω is obtained by testing the recycled aggregate used. a The amount of coarse and fine aggregate in low-carbon recycled aggregate concrete is calculated according to the mass method or volume method.

2. A low-carbon concrete mix design method according to claim 1, characterized in that: The mass method shall be calculated according to the following formula: m fo +m co +m go +m so +m wo =m cp Where: m f0 is the amount of cement per cubic meter of concrete; m Rg is the mass of recycled aggregate concrete; m g0 Total amount of coarse aggregate per cubic meter of concrete; m s0 Fine aggregate dosage per cubic meter of concrete; m w0 Water consumption per cubic meter of concrete; β s is the sand ratio; m cp is the assumed mass of concrete mixture per cubic meter.

3. A low-carbon concrete mix design method according to claim 2, characterized in that: The assumed mass of concrete mixture per cubic meter is in the range of 2350-2450 kg.

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

5. A low-carbon concrete mix design method according to claim 4, characterized in that: The cement density ranges from 2900-3100 kg / m 3 .

6. A low-carbon concrete mix design method according to claim 4, characterized in that: When no air-entraining admixtures are used, the air content of concrete is 1.

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

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

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

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

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