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

Abstract

The invention discloses zero-carbon concrete based on shells and a mix proportion design method thereof, and belongs to the technical field of green building materials, the mix proportion design method of the zero-carbon concrete based on the shells comprises the following steps: calculating and trying to determine the mix proportion of common concrete with a certain strength grade as a reference mix proportion; based on a life cycle analysis method, determining a reference concrete carbon emission list database, and constructing a carbon footprint accounting model; calculating and determining the shell replacement amount according to the principle that the life cycle carbon footprint is zero; and correcting the actual use amount of the replaced sandstone aggregate so as to determine the mix proportion and the strength grade of the zero-carbon concrete. The method has the advantages of being simple, objective in quantification, low in cost, easy to popularize and the like, fills the blank of the method for designing and preparing the zero-carbon building material, and is beneficial for promoting resource utilization of the shellfish waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of green building materials, and in particular relates to a shell-based zero-carbon concrete and a mix ratio design method thereof. Background Art

[0002] In the field of construction, zero-carbon buildings are gaining increasing attention as an important way to achieve carbon neutrality. Zero-carbon buildings not only represent the innovation of architectural design and construction concepts, but also a profound practice of the concept of sustainable development. The core of zero-carbon buildings lies in their ability to achieve net zero carbon emissions throughout their 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, the development and application of low-carbon and zero-carbon building materials play a vital role in reducing the carbon footprint of the construction industry. In response to the current high carbon emissions in the concrete production process, the industry is undergoing a profound transformation from performance-oriented to low-carbon and even zero-carbon-oriented. This transformation not only requires optimizing the production process of concrete and reducing carbon emissions in the production process, but also encourages the use of alternative materials and enhancing the recycling rate of materials to reduce carbon emissions from the source. Therefore, the transformation of concrete from the previous performance-based design concept to a development concept that focuses more on carbon reduction and emission reduction and even zero carbonization is of great significance to the sustainable development of the construction industry and even the world.

[0003] Chinese patent document CN 117602878 A discloses a solid waste concrete prepared based on the principle of joint activation of industrial, agricultural and urban solid wastes and its preparation method, which can effectively reduce the cost of concrete production, reduce carbon emissions, and achieve waste treatment. At present, the methods that can effectively reduce the carbon emissions of concrete mainly include: [1] improving the efficiency of cement use to reduce the amount of cement 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 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 sink capacity and high strength, and have obvious advantages in concrete carbon reduction design. Specifically, first, more than 90% of shells are calcium carbonate, and one ton of shells can absorb and fix an average of 0.45 tons of CO2, with a very significant carbon sink capacity; second, shells can be added in large quantities as concrete aggregates, which has little effect on the mechanical properties of concrete but can greatly increase the amount of carbon fixation and achieve "zero emissions"; third, shellfish farming has a huge output, and shells are domestic waste and are low-cost. In summary, the preparation of zero-carbon concrete based on shells can not only produce cheap and high-quality concrete, but will also make a direct contribution to the building materials industry's achievement of carbon neutrality goals as scheduled.

[0004] However, existing technical reports on shell concrete are usually still based on the design concept of concrete strength, and there is no invention literature on designing zero-carbon concrete using the "negative carbon" properties of shells. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a shell-based zero-carbon concrete and a mix design method thereof, so as to solve the technical problem that the existing shell concrete mainly focuses on improving the strength of concrete and does not fully utilize the "negative carbon" properties of shells to design zero-carbon concrete.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The invention discloses a shell-based zero-carbon concrete mix design method, comprising:

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

[0009] 2) Calculate the carbon footprint of benchmark concrete based on the benchmark concrete mix ratio;

[0010] 3) Calculate the amount of shells replaced in the benchmark concrete mix according to the zero carbon life cycle principle;

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

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

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

[0015] Where CF0 is the carbon footprint of concrete;

[0016] m i It is the reference amount of each component in concrete;

[0017] c i is the carbon emission factor of each component in concrete;

[0018] l i is the transportation distance of each component in concrete;

[0019] c li is the transport carbon emission factor of each component in concrete;

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

[0021] c e is the carbon emission factor of electricity.

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

[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 The amount of shell replacement;

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

[0027] l a is the transportation distance of the replaced sand and gravel aggregate;

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

[0029] c s is the carbon emission factor of shell aggregate;

[0030] l s is the transportation distance of shell aggregate;

[0031] c ls is the carbon emission factor for the transportation of shell aggregate.

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

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

[0034] In the formula, m ac is the actual amount of sand and gravel aggregate replaced;

[0035] m a It is the benchmark amount of sand and gravel aggregate to be replaced.

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

[0037] Further preferably, the shell-based zero-carbon concrete obtained in step 4) is obtained by uniformly mixing cementitious materials, sand, gravel, water, water reducer 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] Further 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] Further preferably, the cementitious material is general-purpose cement or special cement; the sand is natural river sand or artificial sand, and the particle size of the sand is 0.075-4.75 mm; the gravel is pebbles or crushed stones for construction; and the particle size of the gravel is 4.75-25 mm.

[0040] The present invention also discloses a shell-based zero-carbon concrete, which is obtained by adopting 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] The present invention discloses a mix design method for zero-carbon concrete based on shells. The mix ratio of ordinary concrete of a certain strength grade is determined by calculation and trial mixing as a benchmark mix ratio; based on the life cycle analysis method, the benchmark concrete carbon emission inventory database is determined, and a carbon footprint accounting model is constructed; the shell replacement amount is calculated and determined according to the principle of zero life cycle carbon footprint; the actual amount of replaced sand and gravel aggregate is corrected, and then the zero-carbon concrete mix ratio and strength grade are determined. The method quantitatively calculates the carbon emissions of benchmark concrete based on the life cycle analysis method, and then uses a certain amount of crushed shell aggregate as a "carbon fixation" carrier to partially replace concrete aggregate, offsetting the direct and indirect carbon emissions of raw material production, transportation and concrete preparation processes, so that concrete achieves "zero emissions" in the life cycle. The present invention has the advantages of simple method, objective quantification, low cost, and easy promotion. It fills the method and technology gap of zero-carbon building material design and promotes the resource utilization of shell waste.

[0043] The present invention also discloses shell-based zero-carbon concrete obtained by the above-mentioned mix design method, which ensures that the carbon emissions of concrete throughout its life cycle (from raw material mining, production, transportation to concrete preparation) are at or close to zero. This is of great significance for alleviating global climate change and reducing greenhouse gas emissions. As a waste, shells are usually disposed of or landfilled in the traditional way, which not only occupies land resources, but also may pollute the environment. Using them as concrete aggregates not only solves the problem of shell disposal, but also realizes the resource utilization of waste and improves resource utilization efficiency. Shells, as natural materials, may have lower collection and processing costs than concrete sand and gravel aggregates. The appropriate addition of shell aggregates may improve the workability, strength and durability of concrete. The calcium component in shells helps to improve the compressive strength and impermeability of concrete, and its unique microstructure may also have a positive effect on the crack resistance of concrete. This shell-based zero-carbon concrete provides new ideas and technical paths for the research and development of green building materials. Through scientific design and verification, it proves the application potential of shells in concrete and provides reference experience for the resource utilization of other wastes in building materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of the shell-based zero-carbon concrete mix design method disclosed in the present invention. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0048] See also Figure 1 This is a flow chart of the shell-based zero-carbon concrete mix design method disclosed in the present invention. As can be seen from the figure, the shell-based zero-carbon concrete mix design method includes: first determining the base concrete mix; then calculating the base concrete carbon footprint; then calculating the shell replacement amount according to the "life cycle zero carbon" principle; and finally determining the zero-carbon concrete mix and determining the concrete strength grade. The whole method has the advantages of simplicity, objective quantification, low cost, and easy promotion. It fills the gap in the method of designing and preparing zero-carbon building materials, and at the same time helps to promote the resource utilization of shellfish waste.

[0049] The present invention discloses a shell-based zero-carbon concrete, which is obtained by uniformly mixing the components in the following mass ratio: cementitious material, sand, gravel, water, water reducer and shell aggregate in a 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 grade of zero carbon concrete is C15~C35.

[0051] Shell aggregates are fine shells with a particle size not exceeding 4.75 mm or coarse shells with a particle size of 4.75 to 25 mm, which are prepared by crushing the shells of artificially cultured shellfish.

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

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

[0054] 1) Determine the benchmark concrete mix ratio

[0055] According to the characteristics of raw materials and application requirements, the ordinary concrete mix ratio of a certain strength grade is calculated and determined by trial mixing using the method given in "JGJ 55-2011 Ordinary Concrete Mix Design Code" and other relevant regulations, and it is used as the benchmark concrete mix ratio.

[0056] 2) Calculate the baseline concrete carbon footprint

[0057] The life cycle analysis method is used to calculate the carbon emissions of benchmark concrete. In order to collect emission data at each stage and determine the inventory database, the benchmark amount of each component in concrete is recorded as m i (kg / t), the carbon emission factor of each component in concrete is denoted as c i (kg CO 2e / t), the transportation distance of each component in concrete is recorded as l i (km), the transportation carbon emission factor of each component in concrete is denoted as c li (kg CO 2e / (km·t)); the electricity consumption in 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 On this basis, a benchmark concrete carbon footprint CF0 (kg CO 2e / t) calculation 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 replacing the replaced sand and gravel aggregate, that is, the shell replacement amount, is recorded as m s (kg / t), the carbon emission factor of shell aggregate is denoted as c s (kg CO 2e / t), the transportation distance of shell aggregate is recorded as l s (km), the carbon emission factor of shell aggregate transportation is denoted as c ls (kg CO 2e / (km·t)); the carbon emission factor of the replaced sand and gravel aggregate is denoted as c a (kg CO 2e / t), the transportation distance of shell aggregate is recorded as l a (km), the carbon emission factor of the transportation of 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 shell replacement amount 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 ratio and strength grade of zero carbon concrete

[0063] On the basis of clarifying the amount of shell aggregate, the benchmark amount of sand and gravel aggregate to be replaced is m a (kg / t) adjusted to actual usage m ac (kg / t) can get the mix ratio of zero carbon concrete. The actual amount of replaced sand and gravel aggregate m ac It can be solved by formula (3). It should be pointed out that the 28-day strength of zero-carbon concrete with shells replacing sand and gravel aggregates may be lower than that of the benchmark concrete. Its actual strength grade needs to be tested and measured according to relevant national standards or industry standards.

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

[0065] The technical solution of the present invention will be described clearly and completely below. Obviously, the following embodiments are only some examples of the present invention, and all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work 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 benchmark concrete mix ratio

[0069] P·O 32.5 cement was used as the cementitious material to prepare C15 benchmark concrete. Theoretical calculation and experimental verification showed that the mix ratio of each component was cement: natural river sand (medium sand): granite crushed stone (particle size 4.75-25 mm): water: water reducing agent = 1:2.58:3.41:0.59:0.01.

[0070] 2) Calculate the baseline concrete carbon footprint

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

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

[0073] Where CF0 is the carbon footprint of concrete, kg CO 2e / t;m i is the reference amount of each component in concrete, kg / t; c i is the carbon emission factor of each component in concrete, kg CO 2e / t;l i is the transportation distance of each component in concrete, km; c li is the transport carbon emission factor of each component in concrete, kg CO 2e / (km·t);m e is the electricity consumption in the concrete production process, kW·h; ce is the carbon emission factor of electricity, kg CO 2e / (kW·h).

[0074] Table 1 Parameters of each component of C15 benchmark concrete

[0075]

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

[0077] In this example, clamshells are used to partially replace the sand aggregate in the benchmark concrete. The carbon emission factor of fine clamshell aggregate is -397.1 kg CO2e / t, and the average transportation distance and transportation carbon emission factor are calculated as 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 clamshell fine aggregate m is calculated. s It is 202.3kg / t, and the replacement rate of sand aggregate is 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 is the shell replacement amount, kg / t; c a is the carbon emission factor of the replaced sand and gravel aggregate, kg CO 2e / t;l a is the transportation distance of the replaced sand and gravel aggregate, (km); c la is the carbon emission factor of the transport of replaced sand and gravel aggregate, (kg CO 2e / (km·t));c s is the carbon emission factor of shell aggregate, kg CO 2e / t;l s is the transport distance, km; c ls is the transport carbon emission factor, kg CO 2e / (km·t).

[0080] 4) Determine the mix ratio and strength grade of zero carbon concrete

[0081] On the basis of clarifying the amount of clam shell fine aggregate, the amount of sand aggregate in the benchmark mix ratio is adjusted to the actual amount after shell replacement to obtain the mix ratio of zero carbon concrete. Calculated by formula (3), the actual amount of benchmark sand aggregate is 137.6 kg / t. The mix ratio of zero carbon concrete with clam shell replacing part of the sand aggregate is cement: sand: clam shell: gravel: water: water reducer = 1: 1.04: 1.54: 3.41: 0.59: 0.01. The 28-day compressive strength of concrete is 13-15 MPa. The strength of concrete is significantly reduced after clam shell replaces sand in large quantities. According to the national standard "GB 50010-2010 Code for Design of Concrete Structures", it can be seen that the zero carbon concrete can reach the C10 strength grade.

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

[0083] In the formula, m ac is the actual amount of sand and gravel aggregate replaced; m a It is the benchmark amount of sand and gravel aggregate to be 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 benchmark concrete mix ratio

[0087] P·O 32.5 cement was used as the cementitious material to prepare C20 benchmark concrete. The mix ratio of each component was obtained through theoretical calculation and experimental verification as follows: cement: natural river sand (medium sand): granite crushed stone (particle size 4.75-25 mm): water: water reducing agent = 1:1.94:3.77:0.52:0.005.

[0088] 2) Calculate the baseline concrete carbon footprint

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

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

[0091] Where CF0 is the carbon footprint of concrete, kg CO 2e / t;m i is the reference amount of each component in concrete, kg / t; c i is the carbon emission factor of each component in concrete, kg CO 2e / t;l i is the transportation distance of each component in concrete, km; c li is the transport carbon emission factor of each component in concrete, kg CO 2e / (km·t);m e is the electricity consumption in the concrete production process, kW·h; c e is the carbon emission factor of electricity, kg CO 2e / (kW·h).

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

[0093]

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

[0095] In this example, oyster shells are used to partially replace the stone aggregate in the benchmark 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 as 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 It is 187.8kg / t, and the replacement rate of stone aggregate is 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 is the shell replacement amount, kg / t; c a is the carbon emission factor of the replaced sand and gravel aggregate, kg CO 2e / t;l a is the transportation distance of the replaced sand and gravel aggregate, (km); cla is the carbon emission factor of the transport of replaced sand and gravel aggregate, (kg CO 2e / (km·t));c s is the carbon emission factor of shell aggregate, kg CO 2e / t;l s is the transport distance, km; c ls is the transport carbon emission factor, kg CO 2e / (km·t).

[0098] 4) Determine the mix ratio and strength grade of zero carbon concrete

[0099] On the basis of clarifying the amount of oyster shell coarse aggregate, the amount of gravel aggregate in the benchmark mix ratio is adjusted to the actual amount after the shells are partially replaced to obtain the mix ratio of zero carbon concrete. The actual amount of benchmark gravel aggregate can be calculated by formula (3) to be 332.9 kg / t. The mix ratio of zero carbon concrete using oyster shells to replace part of the gravel aggregate is cement: sand: gravel: oyster shell: water: water reducer = 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 to 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 is the actual amount of sand and gravel aggregate replaced; m a It is the benchmark amount of sand and gravel aggregate to be 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 benchmark concrete mix ratio

[0105] P·O 42.5 cement was used as the cementitious material to prepare C30 benchmark concrete. The mix ratio of each component was obtained through theoretical calculation and experimental verification as follows: cement: natural river sand (medium sand): granite crushed stone (particle size 4.75-25 mm): water: water reducing agent = 1:1.82:3.41:0.54:0.01.

[0106] 2) Calculate the baseline concrete carbon footprint

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

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

[0109] Where CF0 is the carbon footprint of concrete, kg CO 2e / t;m i is the reference amount of each component in concrete, kg / t; c i is the carbon emission factor of each component in concrete, kg CO 2e / t;l i is the transportation distance of each component in concrete, km; c li is the transport carbon emission factor of each component in concrete, kg CO 2e / (km·t);m e is the electricity consumption in the concrete production process, kW·h; c e is the carbon emission factor of electricity, kg CO 2e / (kW·h).

[0110] Table 3 Parameters of each component of C30 benchmark 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 stone aggregate in the benchmark concrete. The carbon emission factor of scallop shell coarse aggregate is -393.8kg CO2e / t, and the average transportation distance and transportation carbon emission factor are calculated as 50km and 0.14kg / (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 It is 247.58kg / t, and the replacement rate of stone aggregate is 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 is the shell replacement amount, kg / t; c a is the carbon emission factor of the replaced sand and gravel aggregate, kg CO 2e / t;l a is the transportation distance of the replaced sand and gravel aggregate, (km); c la is the carbon emission factor of the transport of replaced sand and gravel aggregate, (kg CO 2e / (km·t));c s is the carbon emission factor of shell aggregate, kg CO 2e / t;l s is the transport distance, km; c ls is the transport carbon emission factor, kg CO 2e / (km·t).

[0116] 4) Determine the mix ratio and strength grade of zero carbon concrete

[0117] On the basis of clarifying the amount of coarse scallop shells, the amount of gravel aggregate in the benchmark mix ratio is adjusted to the actual amount after shell replacement to obtain the zero-carbon concrete mix ratio. The actual amount of benchmark gravel aggregate is 255.32 kg / t calculated by formula (3). The zero-carbon concrete mix ratio using coarse scallop shells to replace part of the gravel aggregate is cement: sand: gravel: scallop shells: water: water reducer = 1: 1.82: 1.73: 1.68: 0.54: 0.01. The 28-day compressive strength of the concrete is 27-29.5 MPa. According to the national standard "GB 50010-2010 Code for Design of Concrete Structures", the strength of the concrete is reduced to C25 grade. The strength of the concrete is significantly affected after a large amount of scallop shells replace gravel.

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

[0119] In the formula, m ac is the actual amount of sand and gravel aggregate replaced; m a It is the benchmark amount of sand and gravel aggregate to be 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 benchmark concrete mix ratio

[0123] P·O 42.5 cement was used as the cementitious material to prepare C35 benchmark concrete. The mix ratio of each component was obtained through theoretical calculation and experimental verification as follows: cement: natural river sand (medium sand): granite crushed stone (particle size 4.75-25 mm): water: water reducing agent = 1:1.86:3.05:0.48:0.02.

[0124] 2) Calculate the baseline concrete carbon footprint

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

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

[0127] Where CF0 is the carbon footprint of concrete, kg CO 2e / t;m i is the reference amount of each component in concrete, kg / t; c i is the carbon emission factor of each component in concrete, kg CO 2e / t;l i is the transportation distance of each component in concrete, km; c li is the transport carbon emission factor of each component in concrete, kg CO 2e / (km·t);m e is the electricity consumption in the concrete production process, kW·h; c e is the carbon emission factor of electricity, kg CO 2e / (kW·h).

[0128] Table 4 Parameters of each component of C35 benchmark concrete

[0129]

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

[0131] In this example, oyster shells are used to partially replace the stone aggregate in the benchmark 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 as 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 It is 224.74kg / t, and the replacement rate for stone aggregate is 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 is the shell replacement amount, kg / t; c a is the carbon emission factor of the replaced sand and gravel aggregate, kg CO 2e / t;l a is the transportation distance of the replaced sand and gravel aggregate, (km); c la is the carbon emission factor of the transport of replaced sand and gravel aggregate, (kg CO 2e / (km·t));c s is the carbon emission factor of shell aggregate, kg CO 2e / t;l s is the transport distance, km; c ls is the transport carbon emission factor, kg CO 2e / (km·t).

[0134] 4) Determine the mix ratio and strength grade of zero carbon concrete

[0135] On the basis of clarifying the amount of coarse oyster shells, the amount of gravel aggregate in the benchmark mix is ​​adjusted to the actual amount after shells are replaced to obtain the zero-carbon concrete mix. The actual amount of benchmark gravel aggregate is 251.1 kg / t calculated by formula (3). The zero-carbon concrete mix ratio using coarse oyster shells to replace part of the gravel aggregate is cement: sand: gravel: oyster shell: water: water reducer = 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 strength of the concrete can reach C35 grade.

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

[0137] In the formula, m ac is the actual amount of sand and gravel aggregate replaced; m a It is the benchmark amount of sand and gravel aggregate to be replaced.

[0138] The shell-based zero-carbon concrete mix design method disclosed in the present invention includes: calculating and trial-mixing to determine the mix ratio of ordinary concrete of a certain strength grade as the benchmark mix ratio; determining the benchmark concrete carbon emission inventory database based on the life cycle analysis method, and building a carbon footprint accounting model; calculating and determining the shell replacement amount according to the principle of zero life cycle carbon footprint; correcting the actual amount of replaced sand and gravel aggregates, and then determining the zero-carbon concrete mix ratio and strength grade. It has the advantages of simple method, objective quantification, low cost, and easy promotion, filling the gap in the method of designing and preparing zero-carbon building materials, and at the same time helping to promote the resource utilization of shellfish waste.

[0139] Any practice of using the "negative carbon" properties of shells to offset the carbon emissions of concrete during its life cycle falls within the scope of protection of the claims of the present invention. For example: 1) Add other raw materials (admixtures, additives, etc.) to concrete, and then use "negative carbon" materials to offset their carbon emissions; 2) The concrete preparation process not only considers electricity consumption, but also carbon emissions from the use of resources such as water, and then uses "negative carbon" materials to offset its carbon emissions; 3) After determining the zero-carbon concrete mix ratio according to the concept of the present invention, continue to adjust the raw material mix ratio to optimize the concrete performance (for example, adjust the water consumption, optimize the grading of sand and gravel and shell aggregates, use shells to replace coarse and fine aggregates at the same time or replace aggregates and cementitious materials at the same time, modify and strengthen shells, etc.), and then calibrate the amount of shells to achieve zero carbonization again; 4) Other technical innovations proposed based on the concept of the present invention.

[0140] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A shell-based zero-carbon concrete mix design method, characterized in that: include: 1) Determine the benchmark concrete mix ratio; 2) Calculate the carbon footprint of benchmark concrete based on the benchmark concrete mix ratio; 3) Calculate the amount of shells replaced in the benchmark concrete mix according to the zero carbon life cycle principle; 4) Determine the mix proportion and strength grade of shell-based zero-carbon concrete according to the shell replacement amount.

2. The shell-based zero-carbon concrete mix design method according to claim 1, characterized in that: In step 2), a life cycle-based benchmark concrete carbon footprint accounting model is constructed to calculate the benchmark concrete carbon footprint.

3. The shell-based zero-carbon concrete mix design method according to claim 2, characterized in that: In step 2), the life cycle-based benchmark concrete carbon footprint accounting model is specifically: CF0=∑m i c i +∑m i l i c li +m e c e (1) Where CF0 is the carbon footprint of concrete; m i It is the reference amount of each component in concrete; c i is the carbon emission factor of each component in concrete; l i is the transportation distance of each component in concrete; c li is the transport carbon emission factor of each component in concrete; m e The electricity consumption during the concrete production process; c e is the carbon emission factor of electricity.

4. The shell-based zero-carbon concrete mix design method according to claim 1, characterized in that: In step 3), the life cycle zero carbon principle is specifically: (CF0-m s *c a -m s *l a *c la )+m s *c s +m s *l s *c ls =0 (2) In the formula, m s The amount of shell replacement; c a is the carbon emission factor of the replaced sand and gravel aggregate; l a is the transportation distance of the replaced sand and gravel aggregate; c la is the carbon emission factor for the transportation of replaced sand and gravel aggregate; c s is the carbon emission factor of shell aggregate; l s is the transportation distance of shell aggregate; c ls is the carbon emission factor for the transportation of shell aggregate.

5. 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: m ac =m a -m s (3) In the formula, m ac is the actual amount of sand and gravel aggregate replaced; m a It is the benchmark amount of sand and gravel aggregate to be replaced.

6. The shell-based zero-carbon concrete mix design method according to claim 1, characterized in that: The shell-based zero-carbon concrete obtained in step 4) includes: cementitious materials, sand, gravel, water, water reducing agent and shell aggregate.

7. The shell-based zero-carbon concrete mix design method according to claim 6, characterized in that: 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 according to the 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).

8. The shell-based zero-carbon concrete mix design method according to claim 6, 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 not exceeding 4.75 mm or coarse shells with a particle size of 4.75 to 25 mm.

9. The shell-based zero-carbon concrete mix design method according to claim 6, characterized in that: The cementitious material is general cement or special cement; the sand is natural river sand or artificial sand, and the particle size of the sand is 0.075-4.75 mm; the stone is pebbles or crushed stones for construction, and the particle size of the stone is 4.75-25 mm.

10. A shell-based zero-carbon concrete, characterized in that: It is obtained by adopting the shell-based zero-carbon concrete mix design method described in any one of claims 1 to 9.

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