Shell-based zero-carbon concrete and mix proportion design method thereof

Abstract

The application discloses a kind of zero-carbon concrete based on shell and its mix proportion design method, belong to green building material technical field, the mix proportion design method of the zero-carbon concrete based on shell includes the following steps: calculating and trial-blending to determine the mix proportion of certain strength grade ordinary concrete, as reference mix proportion;Based on life cycle analysis method, determine the carbon emission inventory database of reference concrete, build carbon footprint accounting model;According to the principle of life cycle carbon footprint zero, calculate and determine shell replacement amount;Correct the actual amount of replaced sand aggregate, and then determine the mix proportion and strength grade of zero-carbon concrete.The application has the advantages of simple method, quantitative objective, low cost, easy to popularize and the like, fills the blank of zero-carbon building material design preparation method, and helps to promote the resource utilization of shell waste.

Description

Technical Field

[0001] This invention belongs to the field of green building materials technology, specifically relating to a shell-based zero-carbon concrete and its mix design method. Background Technology

[0002] In the construction industry, zero-carbon buildings are gaining increasing attention as a crucial pathway to carbon neutrality. Zero-carbon buildings not only represent an innovation in architectural design and construction concepts but also a profound practice of sustainable development. The core of zero-carbon buildings lies in achieving net-zero carbon emissions throughout their entire life cycle, which relies on the integrated application of a series of zero-carbon technologies. The traditional building materials industry, especially cement production, is one of the main sources of carbon emissions. Therefore, developing and applying low-carbon and zero-carbon building materials is crucial for reducing the carbon footprint of the construction industry. Addressing the high carbon emissions in current concrete production processes, the industry is undergoing a profound shift from a performance-oriented approach to a low-carbon and even zero-carbon approach. This shift not only requires optimizing concrete production processes to reduce carbon emissions during production but also encourages the use of alternative materials and increased material recycling rates to reduce carbon emissions at the source. Therefore, the shift in concrete design from a performance-based approach to a development strategy that emphasizes carbon reduction and even zero-carbonization is of great significance to the sustainable development of the construction industry and the world.

[0003] Chinese patent document CN 117602878 A discloses a solid waste concrete and its preparation method based on the principle of joint activation of solid waste from industry, agriculture and city. It can effectively reduce the production cost of concrete, reduce carbon emissions, and realize the treatment of waste with waste. At present, the main methods that can effectively reduce the carbon emissions of concrete include: [1] improving the efficiency of cement use to reduce the amount used; [2] adding auxiliary cementitious materials (fly ash, mineral powder, etc.) to replace part of the cement; [3] using new cementitious materials (alkali-activated cementitious materials, etc.) to prepare concrete; [4] adding "negative carbon" materials to offset carbon emissions. Among them, the first three methods can only reduce CO2 emissions, while the fourth method uses "negative carbon" materials, which is expected to completely offset the direct and indirect carbon emissions of other raw materials and production processes of concrete, achieve "zero emissions", and obtain "carbon neutrality" properties. It can be seen that zero-carbon concrete designed and prepared based on "negative carbon" materials is a green material that can effectively promote the building materials industry to achieve "carbon neutrality". Among the common "negative carbon" materials, shells have strong carbon sequestration capacity and high strength, and have obvious advantages in concrete carbon reduction design. Specifically, firstly, shells are over 90% calcium carbonate, meaning that one ton of shells can absorb and fix an average of 0.45 tons of CO2, demonstrating a significant carbon sequestration capacity. Secondly, shells can be added in large quantities to concrete aggregates, having minimal impact on the concrete's mechanical properties while substantially increasing carbon sequestration, achieving "zero emissions." Thirdly, shellfish farming yields a huge amount of material, and shells are considered household waste, making them inexpensive. In conclusion, using shells to prepare zero-carbon concrete not only yields inexpensive and high-quality concrete but also directly contributes to the building materials industry's timely achievement of its carbon neutrality goals.

[0004] However, existing technical reports on shell concrete usually still focus on the design concept of concrete strength, and there is no invention literature that utilizes the "negative carbon" property of shells to design zero-carbon concrete. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a shell-based zero-carbon concrete and its mix design method, so as to solve the technical problem that the existing shell concrete mainly focuses on improving concrete strength and does not make full use of the "negative carbon" property of shells to design zero-carbon concrete.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for designing zero-carbon concrete mix proportions based on seashells, including:

[0008] 1) Determine the benchmark concrete mix proportion;

[0009] 2) Calculate the carbon footprint of the reference concrete based on the reference concrete mix proportion;

[0010] 3) Calculate the amount of shell replacement in the benchmark concrete mix design according to the zero-carbon life cycle principle;

[0011] 4) Determine the mix proportion and strength grade of zero-carbon concrete based on the amount of shell replacement.

[0012] Preferably, in step 2), a life-cycle-based benchmark concrete carbon footprint accounting model is constructed to calculate the benchmark concrete carbon footprint.

[0013] More preferably, in step 2), the life-cycle-based benchmark concrete carbon footprint accounting model is specifically as follows:

[0014] CF0=∑m i c i +∑m i l i c li +m e c e (1)

[0015] In the formula, CF0 represents the carbon footprint of concrete;

[0016] m i This is the baseline dosage for each component in concrete;

[0017] c i The carbon emission factors of each component in concrete;

[0018] l i This refers to the transportation distance of each component in the concrete;

[0019] c li The carbon emission factors for the transportation of each component in concrete;

[0020] m e Electricity consumption during the concrete production process;

[0021] c e It is a carbon emission factor for electricity.

[0022] Preferably, in step 3), the zero-carbon life cycle principle specifically means:

[0023] (CF0-m s *c a -m s *l a *c la )+m s *c s +m s *l s *c ls =0 (2)

[0025] In the formula, m s This refers to the amount of shell replacement.

[0026] c a The carbon emission factor of the replaced sand and gravel aggregate;

[0027] l a The transportation distance for the replaced sand and gravel aggregate;

[0028] c la The carbon emission factor for the transportation of the replaced sand and gravel aggregates;

[0029] c s Carbon emission factors for shell aggregate;

[0030] l s The transportation distance for shell aggregate;

[0031] c ls Carbon emission factors for the transportation of shell aggregates.

[0032] Preferably, the actual amount of replaced sand and gravel aggregate in zero-carbon concrete is calculated as follows:

[0033] m ac =m a -m s (3)

[0034] In the formula, m ac This refers to the actual amount of sand and gravel aggregate that was replaced.

[0035] m a The baseline dosage of the sand and gravel aggregate being replaced.

[0036] Preferably, the shell-based zero-carbon concrete obtained in step 4) includes: cementitious materials, sand, gravel, water, water-reducing agent and shell aggregate.

[0037] More preferably, the shell-based zero-carbon concrete obtained in step 4) is obtained by uniformly mixing cementitious materials, sand, gravel, water, water-reducing agent and shell aggregate in a mass mix ratio of 1:(1.04~1.94):(1.61~3.41):(0.48~0.59):(0.005~0.02):(1.36~1.68).

[0038] More preferably, the shell aggregate is obtained by crushing the shells of artificially cultured shellfish, and the shell aggregate is fine shells with a particle size not exceeding 4.75 mm or coarse shells with a particle size of 4.75 to 25 mm.

[0039] More preferably, the cementing material is general-purpose cement or special cement; the sand is natural river sand or artificial sand with a particle size of 0.075 to 4.75 mm; the gravel is building pebbles or crushed stone with a particle size of 4.75 to 25 mm.

[0040] The present invention also discloses a shell-based zero-carbon concrete, which is obtained by using the above-mentioned shell-based zero-carbon concrete mix design method.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention discloses a mix design method for zero-carbon concrete based on seashells. The method calculates and trial-mixes to determine the mix proportion of ordinary concrete of a certain strength grade, serving as a baseline mix proportion. Based on life cycle analysis, a carbon emission inventory database for the baseline concrete is established, and a carbon footprint accounting model is constructed. The amount of seashells to be replaced is calculated according to the principle of zero life cycle carbon footprint. The actual amount of sand and gravel aggregates to be replaced is adjusted, thereby determining the mix proportion and strength grade of the zero-carbon concrete. This method quantitatively calculates the carbon emissions of the baseline concrete based on life cycle analysis, and then uses a certain amount of crushed seashell aggregate as a "carbon sequestration" carrier to partially replace concrete aggregates, offsetting the direct and indirect carbon emissions from raw material production, transportation, and concrete preparation processes, thus achieving "zero emissions" throughout the concrete's life cycle. This invention has the advantages of simple method, objective quantification, low cost, and ease of promotion, filling the gap in the methodology and technology for zero-carbon building material design and promoting the resource utilization of seashell waste.

[0043] This invention also discloses shell-based zero-carbon concrete obtained using the above-mentioned mix design method. This shell-based zero-carbon concrete ensures that the carbon emissions of the concrete reach or approach zero throughout its entire life cycle (from raw material mining, production, transportation to concrete preparation). This is of great significance for mitigating global climate change and reducing greenhouse gas emissions. Shells, as waste, are traditionally disposed of by discarding or landfilling, which not only occupies land resources but may also pollute the environment. Using them as concrete aggregate not only solves the problem of shell disposal but also realizes the resource utilization of waste, improving resource utilization efficiency. As a natural material, shells may have lower collection and processing costs compared to concrete aggregates. Appropriate addition of shell aggregates may improve the workability, strength, and durability of concrete. The calcium content in shells helps improve the compressive strength and impermeability of concrete, while its unique microstructure may also have a positive impact on the crack resistance of concrete. This shell-based zero-carbon concrete provides a new approach and technical path for the research and development of green building materials. Through scientific design and verification, it demonstrates the application potential of shells in concrete and provides valuable experience for the resource utilization of other waste materials in building materials. Attached Figure Description

[0044] Figure 1 This is a flowchart of the zero-carbon concrete mix design method based on seashells disclosed in this invention. Detailed Implementation

[0045] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0046] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0047] The present invention will now be described in further detail with reference to the accompanying drawings:

[0048] See Figure 1 This is a flowchart of the shell-based zero-carbon concrete mix design method disclosed in this invention. As shown in the diagram, the method includes: first, determining the baseline concrete mix proportion; then, calculating the baseline concrete carbon footprint; next, calculating the shell replacement amount according to the "lifecycle zero carbon" principle; and finally, determining the zero-carbon concrete mix proportion and measuring the concrete strength grade. The method is simple, quantitatively objective, low-cost, and easy to promote, filling a gap in the design and preparation methods for zero-carbon building materials, while also contributing to the resource utilization of shellfish waste.

[0049] This invention discloses a shell-based zero-carbon concrete, which is made by uniformly mixing the components in the following mass ratio: cementitious materials, sand, gravel, water, water-reducing agent and shell aggregate are uniformly mixed in the mass ratio of 1: (1.04~1.94): (1.61~3.41): (0.48~0.59): (0.005~0.02): (1.36~1.68).

[0050] Among them, the strength grades of zero-carbon concrete are C15 to C35.

[0051] Shell aggregate is prepared by crushing the shells of artificially cultured shellfish, resulting in fine shells with a particle size not exceeding 4.75 mm or coarse shells with a particle size of 4.75–25 mm.

[0052] The cementitious material is general-purpose cement or special-purpose cement. Sand, as the fine aggregate of concrete, includes natural river sand or manufactured sand with a particle size of 0.075 to 4.75 mm; gravel, as the coarse aggregate of concrete, includes building pebbles or crushed stone with a particle size of 4.75 to 25 mm.

[0053] The zero-carbon concrete mix design method of the present invention includes the following steps:

[0054] 1) Determine the reference concrete mix proportion

[0055] Based on the characteristics of raw materials and application requirements, the mix proportion of ordinary concrete of a certain strength grade was calculated and determined by means of the methods given in the relevant provisions such as "JGJ 55-2011 Code for Mix Proportion Design of Ordinary Concrete", and used as the benchmark concrete mix proportion.

[0056] 2) Calculate the carbon footprint of benchmark concrete

[0057] The carbon emissions of baseline concrete were calculated using a life cycle analysis approach. To collect emission data at each stage and establish an inventory database, the baseline dosage of each component in the concrete was denoted as m. i (kg / t), the carbon emission factor of each component in concrete is denoted as c. i (kg CO 2e / t), the transport distance of each component in the concrete is denoted as l. i (km), the carbon emission factor of each component in concrete during transportation is denoted as c. li (kg CO 2e / (km·t)); The electricity consumption during the concrete production process (batch and mixing process) is recorded as m e (kW·h), the carbon emission factor of electricity is denoted as c. e (kg CO 2e / (kW·h)). Based on this, a life-cycle-based benchmark concrete carbon footprint CF0 (kg CO) is constructed. 2e / t) accounting model, as shown in formula (1):

[0058] CF0=∑m i c i +∑m i l i c li +m e c e(1)

[0059] 3) Calculate the amount of shell replacement according to the "zero carbon life cycle" principle.

[0060] The amount of shell aggregate that replaces the sand and gravel aggregate, i.e., the amount of shell replacement, is denoted as m. s (kg / t), the carbon emission factor of shell aggregate is denoted as c. s (kg CO 2e / t), the transport distance of the shell aggregate is denoted as l s (km), the carbon emission factor for transporting shell aggregate is denoted as c. ls (kg CO 2e / (km·t)); the carbon emission factor of the sand and gravel aggregate to be replaced is denoted as c. a (kg CO 2e / t), the transport distance of the shell aggregate is denoted as l a (km), the carbon emission factor of the transportation of the replaced sand and gravel aggregate is denoted as c. la (kg CO 2e / (km·t)). The life cycle carbon footprint of zero-carbon concrete should be zero, that is, zero-carbon concrete should satisfy formula (2), so that the amount of shell replacement m can be calculated. s .

[0061] (CF0-m s *c a -m s *l a *c la )+m s *c s +m s *l s *c ls =0 (2)

[0062] 4) Determine the mix proportion and strength grade of zero-carbon concrete.

[0063] Based on the clearly defined usage of shell aggregate, the baseline usage m of the sand and gravel aggregate to be replaced is determined. a (kg / t) adjusted to actual usage (m) ac The mix proportions for zero-carbon concrete can be obtained by calculating (kg / t). The actual amount of replaced sand and gravel aggregate (m³) ac The solution can be obtained using formula (3). It should be noted that the 28-day strength of zero-carbon concrete with shells replacing sand and gravel aggregate may be lower than that of the benchmark concrete. Its actual strength grade needs to be determined by testing in accordance with relevant national or industry standards.

[0064] m ac =m a -m s (3)

[0065] The technical solution of the present invention will be clearly and completely described below. Obviously, the following embodiments are only some examples of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0066] Example 1

[0067] The mix design method for preparing shell zero-carbon concrete based on conventional C15 concrete includes the following steps:

[0068] 1) Determine the reference concrete mix proportion

[0069] P·O 32.5 cement was used as the cementitious material to prepare C15 reference concrete. Theoretical calculations and experimental verification yielded the following mix proportions: cement: natural river sand (medium sand): granite crushed stone (particle size 4.75~25mm): water: water-reducing agent = 1:2.58:3.41:0.59:0.01.

[0070] 2) Calculate the carbon footprint of benchmark concrete

[0071] The carbon emission factors, dosage, transportation carbon emission factors, and transport distance of each component in the reference concrete are shown in Table 1. The average electricity consumption for preparing 1 cubic meter of concrete (calculated as 2.4 tons) is 2 kWh, and the current carbon emission factor of electricity in my country is 0.5839 kg CO2e / (kWh). Based on the life cycle analysis method, the carbon footprint CF0 of C15 reference concrete can be calculated as 80.83 kg CO2e / t by substituting the data in the table into formula (1).

[0072] CF0=∑m i c i +∑m i l i c li +m e c e (1)

[0073] In the formula, CF0 is the carbon footprint of concrete, kg CO 2e / t;m i The standard dosage of each component in concrete is expressed in kg / t; c i The carbon emission factors of each component in concrete, kg CO 2e / t;l i c represents the transport distance of each component in concrete, in km; li The transport carbon emission factor of each component in concrete, kg CO 2e / (km·t); m e Electricity consumption during concrete production, kW·h; ce For the carbon emission factor of electricity, kg CO 2e / (kW·h).

[0074] Table 1. Parameters of each component of C15 reference concrete

[0075]

[0076] 3) Calculate the amount of shell replacement according to the "zero carbon life cycle" principle.

[0077] In this embodiment, clam shells are used to partially replace the sand aggregate in the reference concrete. The carbon emission factor of fine clam shell aggregate is -397.1 kg CO2e / t, and the average transportation distance and transportation carbon emission factor are calculated based on 50 km and 0.14 kg / (km·t), respectively. The life cycle carbon footprint of zero-carbon concrete should be zero, that is, zero-carbon concrete should satisfy formula (2), and then the amount of fine clam shell aggregate m is calculated. s The concentration was 202.3 kg / t, and the replacement rate of sand aggregate was 59.52%.

[0078] (CF0-m s *c a -m s *l a *c la )+m s *c s +m s *l s *c ls =0 (2)

[0079] In the formula, m s c represents the amount of shell replacement, expressed in kg / t. a The carbon emission factor of the replaced sand and gravel aggregate, kg CO 2e / t;l a The transport distance of the replaced sand and gravel aggregate, (km); c la The carbon emission factor for the transportation of the replaced sand and gravel aggregates, (kg CO) 2e / (km·t)); c s Carbon emission factor of shell aggregate, kg CO 2e / t;l s For transport distance, in km; c ls For transporting carbon emission factors, kg CO 2e / (km·t).

[0080] 4) Determine the mix proportion and strength grade of zero-carbon concrete.

[0081] Based on the clear dosage of clam shell fine aggregate, the mix proportion of zero-carbon concrete can be obtained by adjusting the dosage of sand aggregate in the benchmark mix proportion to the actual dosage after clam shell replacement. Calculated using formula (3), the actual dosage of benchmark sand aggregate is 137.6 kg / t. The mix proportion of zero-carbon concrete with clam shell replacing part of the sand aggregate is cement:sand:clam shell:gravel:water:water-reducing agent = 1:1.04:1.54:3.41:0.59:0.01. The 28-day compressive strength of concrete is 13-15 MPa. After a large amount of clam shell replaces sand, the concrete strength is significantly reduced. According to the national standard GB 50010-2010 Code for Design of Concrete Structures, this zero-carbon concrete can reach the C10 strength grade.

[0082] m ac =m a -m s (3)

[0083] In the formula, m ac The actual amount of sand and gravel aggregate replaced; m a The baseline dosage of the sand and gravel aggregate being replaced.

[0084] Example 2

[0085] The mix design method for preparing shell zero-carbon concrete based on conventional C20 concrete includes the following steps:

[0086] 1) Determine the reference concrete mix proportion

[0087] P·O 32.5 cement was used as the cementitious material to prepare C20 reference concrete. Theoretical calculation and experimental verification yielded the following mix proportions: cement: natural river sand (medium sand): granite crushed stone (particle size 4.75~25mm): water: water-reducing agent = 1:1.94:3.77:0.52:0.005.

[0088] 2) Calculate the carbon footprint of benchmark concrete

[0089] The carbon emission factors, dosage, transportation carbon emission factors, and transportation distance of each component in the reference concrete are shown in Table 2. The average electricity consumption for preparing 1 cubic meter of concrete (calculated as 2.4 tons) is 2 kWh, and the current carbon emission factor of electricity in my country is 0.5839 kg CO2e / (kWh). Based on the life cycle analysis method, the carbon footprint CF0 of C20 reference concrete can be calculated as 85.51 kg CO2e / t by substituting the above data into formula (1).

[0090] CF0=∑m i c i +∑m i l i c li +m ec e (1)

[0091] In the formula, CF0 is the carbon footprint of concrete, kg CO 2e / t;m i The standard dosage of each component in concrete is expressed in kg / t; c i The carbon emission factors of each component in concrete, kg CO 2e / t;l i c represents the transport distance of each component in concrete, in km; li The transport carbon emission factor of each component in concrete, kg CO 2e / (km·t); m e Electricity consumption during concrete production, kW·h; c e For the carbon emission factor of electricity, kg CO 2e / (kW·h).

[0092] Table 2 Parameters of each component of C20 reference concrete

[0093]

[0094] 3) Calculate the amount of shell replacement according to the "zero carbon life cycle" principle.

[0095] In this embodiment, oyster shells are used to partially replace the aggregate in the reference concrete. The carbon emission factor of oyster shell coarse aggregate is -455.6 kg CO2e / t, and the average transportation distance and transportation carbon emission factor are calculated based on 80 km and 0.142 kg / (km·t), respectively. The life cycle carbon footprint of zero-carbon concrete should be zero, that is, it should satisfy formula (2), and then the amount of oyster shell aggregate m can be calculated. s The yield was 187.8 kg / t, and the replacement rate of gravel aggregate was 36.07%.

[0096] (CF0-m s *c a -m s *l a *c la )+m s *c s +m s *l s *c ls =0 (2)

[0097] In the formula, m s c represents the amount of shell replacement, expressed in kg / t. a The carbon emission factor of the replaced sand and gravel aggregate, kg CO 2e / t;l a The transport distance of the replaced sand and gravel aggregate, (km); cla The carbon emission factor for the transportation of the replaced sand and gravel aggregates, (kg CO) 2e / (km·t)); c s Carbon emission factor of shell aggregate, kg CO 2e / t;l s For transport distance, in km; c ls For transporting carbon emission factors, kg CO 2e / (km·t).

[0098] 4) Determine the mix proportion and strength grade of zero-carbon concrete.

[0099] Based on the clearly defined amount of oyster shell coarse aggregate, the mix proportion of zero-carbon concrete can be obtained by adjusting the amount of gravel aggregate in the benchmark mix proportion to the actual amount after partial replacement with shells. The actual amount of benchmark gravel aggregate can be calculated using formula (3) as 332.9 kg / t. The mix proportion of zero-carbon concrete with partial replacement of gravel aggregate with oyster shells is cement: sand: gravel: oyster shells: water: water-reducing agent = 1:1.94:2.41:1.36:0.52:0.005. The 28-day compressive strength of the concrete is in the range of 20-22.5 MPa. According to the national standard "GB 50010-2010 Code for Design of Concrete Structures", the concrete can also reach the C20 strength grade.

[0100] m ac =m a -m s (3)

[0101] In the formula, m ac The actual amount of sand and gravel aggregate replaced; m a The baseline dosage of the sand and gravel aggregate being replaced.

[0102] Example 3

[0103] The mix design method for preparing shell zero-carbon concrete based on conventional C30 concrete includes the following steps:

[0104] 1) Determine the reference concrete mix proportion

[0105] P·O 42.5 cement was used as the cementitious material to prepare C30 reference concrete. Theoretical calculation and experimental verification yielded the following mix proportions: cement: natural river sand (medium sand): granite crushed stone (particle size 4.75~25mm): water: water-reducing agent = 1:1.82:3.41:0.54:0.01.

[0106] 2) Calculate the carbon footprint of benchmark concrete

[0107] The carbon emission factors, dosage, transportation carbon emission factors, and transport distance of each component in the reference concrete are shown in Table 3. The average electricity consumption for preparing 1 cubic meter of concrete (calculated as 2.4 tons) is 2 kWh, and the current carbon emission factor of electricity in my country is 0.5839 kg CO2e / (kWh). Based on the life cycle analysis method, the carbon footprint CF0 of C30 reference concrete can be calculated as 98.01 kg CO2e / t by substituting the above data into formula (1).

[0108] CF0=∑m i c i +∑m i l i c li +m e c e (1)

[0109] In the formula, CF0 is the carbon footprint of concrete, kg CO 2e / t;m i The standard dosage of each component in concrete is expressed in kg / t; c i The carbon emission factors of each component in concrete, kg CO 2e / t;l i c represents the transport distance of each component in concrete, in km; li The transport carbon emission factor of each component in concrete, kg CO 2e / (km·t); m e Electricity consumption during concrete production, kW·h; c e For the carbon emission factor of electricity, kg CO 2e / (kW·h).

[0110] Table 3 Parameters of each component of C30 reference concrete

[0111]

[0112] 3) Calculate the amount of shell replacement according to the "zero carbon life cycle" principle.

[0113] In this embodiment, scallop shells are used to partially replace the aggregate in the reference concrete. The carbon emission factor of scallop shell coarse aggregate is -393.8 kg CO2e / t, and the average transportation distance and transportation carbon emission factor are calculated based on 50 km and 0.14 kg / (km·t), respectively. The life cycle carbon footprint of zero-carbon concrete should be zero, that is, it should satisfy formula (2), and then the amount of scallop shell aggregate m can be calculated. s The yield was 247.58 kg / t, and the replacement rate of gravel aggregate was 49.23%.

[0114] (CF0-m s *c a-m s *l a *c la )+m s *c s +m s *l s *c ls =0 (2)

[0115] In the formula, m s c represents the amount of shell replacement, expressed in kg / t. a The carbon emission factor of the replaced sand and gravel aggregate, kg CO 2e / t;l a The transport distance of the replaced sand and gravel aggregate, (km); c la The carbon emission factor for the transportation of the replaced sand and gravel aggregates, (kg CO) 2e / (km·t)); c s Carbon emission factor of shell aggregate, kg CO 2e / t;l s For transport distance, in km; c ls For transporting carbon emission factors, kg CO 2e / (km·t).

[0116] 4) Determine the mix proportion and strength grade of zero-carbon concrete.

[0117] Based on the clear usage of coarse scallop shells, the zero-carbon concrete mix proportion can be obtained by adjusting the amount of aggregate in the benchmark mix proportion to the actual amount after shell replacement. The actual amount of benchmark aggregate can be calculated using formula (3) as 255.32 kg / t. The zero-carbon concrete mix proportion using coarse scallop shells to replace part of the aggregate is cement: sand: aggregate: scallop shell: water: water-reducing agent = 1:1.82:1.73:1.68:0.54:0.01. The 28-day compressive strength of concrete is 27-29.5 MPa. According to the national standard "GB 50010-2010 Code for Design of Concrete Structures", the concrete strength is reduced to grade C25. The concrete strength is significantly affected after a large amount of scallop shells replace the aggregate.

[0118] m ac =m a -m s (3)

[0119] In the formula, m ac The actual amount of sand and gravel aggregate replaced; m a The baseline dosage of the sand and gravel aggregate being replaced.

[0120] Example 4

[0121] The mix design method for preparing shell zero-carbon concrete based on conventional C35 concrete includes the following steps:

[0122] 1) Determine the reference concrete mix proportion

[0123] P·O 42.5 cement was used as the cementitious material to prepare C35 reference concrete. Theoretical calculation and experimental verification yielded the following mix proportions: cement: natural river sand (medium sand): granite crushed stone (particle size 4.75~25mm): water: water-reducing agent = 1:1.86:3.05:0.48:0.02.

[0124] 2) Calculate the carbon footprint of benchmark concrete

[0125] The carbon emission factors, dosage, transportation carbon emission factors, and transportation distance of each component in the reference concrete are shown in Table 4. The average electricity consumption for preparing 1 cubic meter of concrete (calculated as 2.4 tons) is 2 kWh, and the current carbon emission factor of electricity in my country is 0.5839 kg CO2e / (kWh). Based on the life cycle analysis method, the carbon footprint CF0 of C35 reference concrete can be calculated as 102.7 kg CO2e / t by substituting the above data into formula (1).

[0126] CF0=∑m i c i +∑m i l i c li +m e c e (1)

[0127] In the formula, CF0 is the carbon footprint of concrete, kg CO 2e / t;m i The standard dosage of each component in concrete is expressed in kg / t; c i The carbon emission factors of each component in concrete, kg CO 2e / t;l i c represents the transport distance of each component in concrete, in km; li The transport carbon emission factor of each component in concrete, kg CO 2e / (km·t); m e Electricity consumption during concrete production, kW·h; c e For the carbon emission factor of electricity, kg CO 2e / (kW·h).

[0128] Table 4. Parameters of each component of C35 reference concrete

[0129]

[0130] 3) Calculate the amount of shell replacement according to the "zero carbon life cycle" principle.

[0131] In this embodiment, oyster shells are used to partially replace the aggregate in the reference concrete. The carbon emission factor of oyster shell coarse aggregate is -455.6 kg CO2e / t, and the average transportation distance and transportation carbon emission factor are calculated based on 50 km and 0.14 kg / (km·t), respectively. The life cycle carbon footprint of zero-carbon concrete should be zero, that is, it should satisfy formula (2), and then the amount of oyster shell aggregate m can be calculated. s The concentration was 224.74 kg / t, and the replacement rate of gravel aggregate was 47.23%.

[0132] (CF0-m s *c a -m s *l a *c la )+m s *c s +m s *l s *c ls =0 (2)

[0133] In the formula, m s c represents the amount of shell replacement, expressed in kg / t. a The carbon emission factor of the replaced sand and gravel aggregate, kg CO 2e / t;l a The transport distance of the replaced sand and gravel aggregate, (km); c la The carbon emission factor for the transportation of the replaced sand and gravel aggregates, (kg CO) 2e / (km·t)); c s Carbon emission factor of shell aggregate, kg CO 2e / t;l s For transport distance, in km; c ls For transporting carbon emission factors, kg CO 2e / (km·t).

[0134] 4) Determine the mix proportion and strength grade of zero-carbon concrete.

[0135] Based on the clearly defined amount of coarse oyster shells, the amount of aggregate in the benchmark mix proportion can be adjusted to the actual amount after the shells are replaced to obtain the zero-carbon concrete mix proportion. The actual amount of benchmark aggregate can be calculated using formula (3) as 251.1 kg / t. The zero-carbon concrete mix proportion using coarse oyster shells to replace part of the aggregate is cement:sand:aggregate:oyster shell:water:water-reducing agent = 1:1.86:1.61:1.44:0.48:0.02. The 28-day compressive strength of the concrete is 35-37 MPa. According to the national standard GB 50010-2010 Code for Design of Concrete Structures, the concrete strength can reach grade C35.

[0136] m ac =m a -m s (3)

[0137] In the formula, m ac The actual amount of sand and gravel aggregate replaced; m a The baseline dosage of the sand and gravel aggregate being replaced.

[0138] The zero-carbon concrete mix design method based on shells disclosed in this invention includes: calculating and trial-mixing to determine the mix proportion of ordinary concrete of a certain strength grade as a benchmark mix proportion; determining a benchmark concrete carbon emission inventory database based on life cycle analysis methods and constructing a carbon footprint accounting model; calculating and determining the amount of shell replacement according to the principle of zero life cycle carbon footprint; correcting the actual amount of replaced sand and gravel aggregates to determine the zero-carbon concrete mix proportion and strength grade. This method has advantages such as simplicity, objective quantification, low cost, and ease of promotion, filling the gap in the design and preparation methods for zero-carbon building materials, and also contributing to the resource utilization of shellfish waste.

[0139] Any practice that utilizes the "carbon-negative" properties of seashells to offset the carbon emissions of concrete throughout its lifecycle falls within the scope of protection of the claims of this invention. Examples include: 1) adding other raw materials (admixtures, additives, etc.) to concrete, and then using "carbon-negative" materials to offset their carbon emissions; 2) considering not only electricity consumption but also carbon emissions from water and other resource usage during concrete mix design, and then using "carbon-negative" materials to offset these emissions; 3) after determining the zero-carbon concrete mix proportion according to the principles of this invention, further adjusting the raw material mix proportions to optimize concrete performance (e.g., adjusting water usage, optimizing the gradation of sand, gravel, and seashell aggregates, using seashells to simultaneously replace coarse and fine aggregates or simultaneously replace aggregates and cementitious materials, modifying and strengthening seashells, etc.), thereby correcting the seashell usage to achieve zero carbon again; 4) other technological innovations based on the principles of this invention.

[0140] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for designing the mix proportion of zero-carbon concrete based on seashells, characterized in that, include: 1) Determine the benchmark concrete mix proportion; 2) Calculate the carbon footprint of the reference concrete based on the reference concrete mix proportion; A life-cycle-based benchmark concrete carbon footprint accounting model is constructed for calculating the benchmark concrete carbon footprint. The life-cycle-based benchmark concrete carbon footprint accounting model is as follows: （1） In the formula, CF0 represents the carbon footprint of concrete, measured in kg CO2. 2e / t; m i This represents the standard dosage of each component in concrete, expressed in kg / t. c i The carbon emission factor of each component in concrete is expressed in kg CO. 2e / t; l i The transport distance of each component in the concrete is expressed in km. c li The transport carbon emission factor of each component in concrete is expressed in kg CO. 2e / (km·t); m e Electricity consumption during concrete production, expressed in kW·h / t; c e Carbon emission factor for electricity, unit is kg CO 2e / (kW·h); 3) Calculate the amount of shell replacement in the benchmark concrete mix design according to the zero-carbon life cycle principle; The zero-carbon lifecycle principle is specifically as follows: （2） In the formula, m s The amount of shell replacement is expressed in kg / t. c a The carbon emission factor of the replaced sand and gravel aggregate is expressed in kg CO. 2e / t; l a The transport distance of the replaced sand and gravel aggregate, in km; c la The carbon emission factor for the transportation of the replaced sand and gravel aggregates is expressed in kg CO. 2e / (km·t); c s Carbon emission factor of shell aggregate, unit is kg CO. 2e / t; l s The transport distance for shell aggregate is expressed in km. c ls Carbon emission factor for the transportation of shell aggregate, in kg CO 2e / (km·t); 4) Determine the mix proportion and strength grade of zero-carbon concrete based on the amount of shell replacement; Shell-based zero-carbon concrete includes: cementitious materials, sand, gravel, water, water-reducing agent, and shell aggregate.

2. The shell-based zero-carbon concrete mix design method according to claim 1, characterized in that, The actual amount of sand and gravel aggregate replaced in zero-carbon concrete is calculated as follows: （3） In the formula, m ac The actual amount of sand and gravel aggregate replaced is expressed in kg / t. m a The standard dosage of the replaced sand and gravel aggregate is expressed in kg / t.

3. The shell-based zero-carbon concrete mix design method according to claim 1, characterized in that, Step 4) The shell-based zero-carbon concrete obtained is made by uniformly mixing cementitious materials, sand, gravel, water, water-reducing agent and shell aggregate according to the mass mix ratio 1: (1.04~1.94): (1.61~3.41): (0.48~0.59): (0.005~0.02): (1.36~1.68).

4. The shell-based zero-carbon concrete mix design method according to claim 1, characterized in that, The shell aggregate is obtained by crushing the shells of artificially cultured shellfish. The shell aggregate is fine shells with a particle size of no more than 4.75 mm or coarse shells with a particle size of 4.75~25 mm.

5. The shell-based zero-carbon concrete mix design method according to claim 1, characterized in that, The cementing material is general-purpose cement or special-purpose cement; the sand is natural river sand or artificial sand with a particle size of 0.075~4.75 mm; the gravel is building pebbles or crushed stone with a particle size of 4.75~25 mm.

6. A zero-carbon concrete based on seashells, characterized in that, The mix design method for zero-carbon concrete based on shells, as described in any one of claims 1 to 5, is used.

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