Microbial self-repairing concrete mix proportion design method and design system

Abstract

The application is a microbial self-repairing concrete mix proportion design method and design system, the core of which is to establish a quantitative design model with the goal of maximizing microbial repair potential, and to realize the collaborative optimization with conventional concrete mix proportion parameters. First, the required calcium carbonate generation amount is determined based on the target crack size; then, the optimal microbial and nutrient content is calculated through the established microbial metabolism kinetics model; the key is to establish the correlation model of the microbial system as a key factor affecting the water-cement ratio and fluidity and the dosage of the additive, and to perform integrated calculation of the water-cement ratio-aggregate system-additive. The application realizes the leap of self-repairing concrete mix proportion from empirical exploration to quantitative, precise and integrated design.

Description

Technical Field

[0001] This invention relates to the technical field of building materials, and in particular to a method and system for designing the mix proportion of microbial self-healing concrete. Background Technology

[0002] Concrete, due to its excellent compressive strength and wide availability of raw materials, is the most widely used building material in the world. However, the inherent quasi-brittleness of concrete makes it prone to microcracks during its service life. These microcracks provide channels for the rapid intrusion of moisture and corrosive media (such as chloride and sulfate ions), severely accelerating steel corrosion and concrete deterioration, ultimately leading to a decrease in structural load-bearing capacity and a shortened service life.

[0003] To address the problem of concrete cracking, the concept of self-healing concrete has emerged. Among these, microbial self-healing technology has become a research hotspot due to its green, efficient, and intrinsically repairing characteristics. The main principle of this technology is to introduce specific microorganisms (such as Bacillus pasteurellii) and their nutrients into the concrete in spore form. When cracks form and moisture seeps in, the microbial spores are activated, using their metabolism to convert pre-placed nutrients (such as calcium and organic carbon sources) into calcium carbonate precipitates, thereby autonomously sealing the cracks.

[0004] However, current microbial self-healing concrete technology still has significant limitations. Its mix design mostly relies on trial and error and empirical exploration, lacking systematic theoretical guidance and quantitative design models. Engineers find it difficult to accurately determine the optimal dosage of microorganisms and nutrients, leading to the following problems: (1) When the dosage is insufficient, the repair effect is not up to standard and the target cracks cannot be effectively sealed; (2) When the dosage is too high, it not only significantly increases the material cost, but may also negatively affect the workability, mechanical strength and long-term durability of concrete due to the introduction of too much organic matter or changes in the hydration process.

[0005] Therefore, developing a method and system that can quantitatively and accurately design the mix proportions of microbial self-healing concrete is crucial for promoting the practical engineering application of this technology. Summary of the Invention

[0006] The present invention aims to address the shortcomings of the prior art by providing a method and system for designing the mix proportion of microbial self-healing concrete.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for designing the mix proportions of microbial self-healing concrete includes the following steps:

[0009] S1. Determine the basic performance requirements for concrete;

[0010] S2. Determine the target parameters for repair, including the target crack width w, the expected repair time t, and the repair efficiency coefficient η;

[0011] S3. Based on the target repair parameters, calculate the theoretically required amount of calcium carbonate deposition, M. CaCO3 ;

[0012] S4. Establish a microbial metabolic kinetic model based on the theoretically required calcium carbonate deposition amount M. CaCO3 And the alkaline environment (pH value) inside the concrete, calculate the initial viable microbial concentration N0 and the total nutrient concentration C. nutrient ;

[0013] S5. The initial viable microbial concentration N0 and the total nutrient concentration C nutrient This translates into specific material dosages in concrete, including the dosage of microbial spores (m). spore Dosage m of nutrient complex nutrient ;

[0014] S6. Perform integrated mix proportion calculation, specifically as follows:

[0015] S6.1 Determine the baseline water-cement ratio W / C base Based on the water absorption capacity of nutrients and microbial spores and their impact on flowability, the effective water consumption W is calculated. effective And the corrected water-cement ratio W / C corrected ;

[0016] S6.2. Based on the absolute volume method, calculate the required total aggregate volume V according to the target bulk density, cementitious material dosage, effective water dosage, and the volume of microorganisms and nutrients. aggregate ;

[0017] S6.3. Based on aggregate gradation theory and workability requirements, determine the fine aggregate ratio and calculate the fine aggregate dosage m. sand Coarse aggregate usage (m) coarse ;

[0018] S6.4. Based on the corrected water-cement ratio and flowability requirements, the water-reducing agent dosage m is calculated using the flowability-admixture dosage relationship model. superplasticizer ;

[0019] S6.5, The final output is a complete self-healing concrete mix design.

[0020] In step S3, the theoretically required amount of calcium carbonate deposition M CaCO3 Calculated using the following formula:

[0021] M CaCO3 =k×ρ CaCO3 ×V crack ;

[0022] in,

[0023] V crack =α×w 2 ×L represents the approximate volume of the crack to be repaired;

[0024] k is the safety factor, which ranges from 1.5 to 2.0;

[0025] ρ CaCO3 The density of calcium carbonate;

[0026] α is the crack morphology coefficient;

[0027] L is the estimated total length of cracks per unit volume of concrete.

[0028] w represents the target crack width.

[0029] In step S4, the core formula of the microbial metabolic kinetics model is:

[0030] M CaCO3 =η×Y×N0×(1-e -μt )×f(pH);

[0031] in,

[0032] Y is the yield coefficient of calcium carbonate produced by microorganisms;

[0033] μ represents the specific growth rate of microorganisms under specific nutritional conditions.

[0034] f(pH) is the pH effect function, characterizing the degree of inhibition of microbial activity by the alkaline environment of concrete. Its expression is f(pH) = 1 / (1 + e^{β(pH - pH) ... opt )}), β is the inhibition coefficient, pH opt This is the optimal pH value for microorganisms.

[0035] In step S4, the total nutrient concentration C nutrient Calculated using the nutrient consumption measurement formula:

[0036] C nutrient =(M CaCO3 / Mw CaCO3 )×S n ;

[0037] in,

[0038] Mw CaCO3 This is the molar mass of calcium carbonate.

[0039] S n The number of moles of nutrients required to produce one mole of calcium carbonate is determined based on the specific stoichiometric relationship of the selected nutrient (such as calcium nitrate, yeast extract, etc.).

[0040] In step S6.1, the corrected water-cement ratio W / C corrected Calculated using the following formula:

[0041] W effective =W total -(m spore ×k spore +m nutrient ×k nutrient );

[0042] W / C corrected =W effective / m cement ;

[0043] in,

[0044] W total This represents the total water consumption.

[0045] k spore and k nutrient These are the water adsorption coefficients per unit mass of the microbial spore and nutrient complex;

[0046] m cement This refers to the amount of cementitious material used.

[0047] In step S6.2, the total aggregate volume V aggregate Calculated using the absolute volume method:

[0048] V aggregate =1-(m cement / ρ cement +W effective / ρ water +m spore / ρ spore +m nutrient / ρ nutrient +V air );

[0049] in,

[0050] ρ cement ,ρ water ,ρ spore ,ρ nutrient The apparent densities are those of cement, water, spores, and nutrients, respectively.

[0051] V air To design the gas content volume.

[0052] In step S6.4, the amount of water-reducing agent m superplasticizer Determined through the following model:

[0053] m superplasticizer =A×(W / Cbase -W / C corrected ) / (W / C corrected )+B×(m spore +m nutrient ) / m cement ;

[0054] in,

[0055] A and B are coefficients obtained by fitting experimental data, representing the sensitivity to changes in water-cement ratio and the compensation effect on the loss of fluidity introduced by solid admixtures, respectively.

[0056] A microbial self-healing concrete mix design system, used in the aforementioned microbial self-healing concrete mix design method, comprising:

[0057] Data input module: used to receive user-defined repair target parameters, selected microorganisms and nutrient types, selected material properties, and baseline concrete performance requirements;

[0058] Core calculation module: Built-in microbial metabolic kinetics model and integrated ratio calculation algorithm, used to perform calculations based on input parameters to solve for the optimal microbial and nutrient content and complete ratio;

[0059] Results output module: Used to generate and display a complete concrete mix design report, including the amount of each component material, predicted repair performance, and basic mechanical properties of the concrete.

[0060] The core computing module also includes an optimization submodule. The optimization submodule uses an iterative algorithm to perform multi-objective optimization on parameters such as microbial content, nutrient content, and water-cement ratio, with the goal of maximizing the repair efficiency-cost ratio or minimizing the total material cost.

[0061] The beneficial effects of this invention are:

[0062] 1. Quantification and Precision: The original experience-based formula design is transformed into quantitative calculation based on theoretical models, making the repair effect predictable and controllable.

[0063] 2. Optimal efficiency and cost: The model accurately calculates the minimum necessary dosage, avoiding material waste and achieving the best balance between repair effectiveness and material cost.

[0064] 3. Systematic: It provides a complete design process from repair objectives to final material proportions, and has developed a corresponding design system, which greatly improves design efficiency and is easy to promote in engineering. Attached Figure Description

[0065] Figure 1 This is a flowchart illustrating the steps of the microbial self-healing concrete mix design method in this invention.

[0066] Figure 2 This is a schematic diagram of the microbial self-healing concrete mix design system of the present invention;

[0067] Figure 3 This is a diagram showing the self-healing effect of the benchmark group specimens during the self-healing performance test in a specific embodiment of the present invention.

[0068] Figure 4 This is a diagram showing the self-healing effect of the test specimens during the self-healing performance test in a specific embodiment of the present invention.

[0069] The following will describe in detail, with reference to the accompanying drawings, embodiments of the present invention. Detailed Implementation

[0070] The principles and features of the present invention are described below with reference to the accompanying drawings. The embodiments given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0072] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0073] A method for designing mix proportions of microbial self-healing concrete, such as Figure 1 As shown, it includes the following steps:

[0074] S1. Determine the basic performance requirements for concrete;

[0075] S2. Determine the target parameters for repair, including the target crack width w, the expected repair time t, and the repair efficiency coefficient η;

[0076] S3. Based on the target repair parameters, calculate the theoretically required amount of calcium carbonate deposition, M. CaCO3 ;

[0077] S4. Establish a microbial metabolic kinetic model based on the theoretically required calcium carbonate deposition amount M. CaCO3 And the internal pH value of the concrete, calculate the initial viable microbial concentration N0 and the total nutrient concentration C. nutrient;

[0078] S5. The initial viable microbial concentration N0 and the total nutrient concentration C nutrient This translates into specific material dosages in concrete, including the dosage of microbial spores (m). spore Dosage m of nutrient complex nutrient ;

[0079] S6. Perform integrated mix proportion calculation, specifically as follows:

[0080] S6.1 Determine the baseline water-cement ratio W / C base Based on the water absorption capacity of nutrients and microbial spores and their impact on flowability, the effective water consumption W is calculated. effective And the corrected water-cement ratio W / C corrected ;

[0081] S6.2. Based on the absolute volume method, calculate the required total aggregate volume V according to the target bulk density, cementitious material dosage, effective water dosage, and the volume of microorganisms and nutrients. aggregate ;

[0082] S6.3. Based on aggregate gradation theory and workability requirements, determine the fine aggregate ratio and calculate the fine aggregate dosage m. sand Coarse aggregate usage (m) coarse ;

[0083] S6.4. Based on the corrected water-cement ratio and flowability requirements, the water-reducing agent dosage m is calculated using the flowability-admixture dosage relationship model. superplasticizer ;

[0084] S6.5, The final output is a complete self-healing concrete mix design.

[0085] The core of the above design method is to establish and solve a quantitative model based on the microbial remediation mechanism. This method directly transforms the remediation objectives (crack size, remediation time) into specific material proportions.

[0086] The details are as follows:

[0087] 1. Calculation of the theoretically required amount of calcium carbonate deposition.

[0088] Repairing cracks essentially involves filling the crack spaces with calcium carbonate. Therefore, the first step is to determine the theoretically required amount of calcium carbonate, M. CaCO3 The crack can be simplified as a wedge-shaped or plate-like body with an average width w and a certain depth and length. Its approximate volume V crack It can be represented as:

[0089] V crack =α×w 2 ×L;

[0090] Where α is a coefficient related to the crack morphology (α≈1 for ideal sheet cracks); L is an estimated total length of cracks that need to be repaired per unit volume of concrete, which can be set according to structural design requirements.

[0091] Considering the incompleteness of deposition and the density of the filling, a safety factor k (typically taken as 1.5~2.0) is introduced. Therefore, the theoretically required amount of calcium carbonate deposition is:

[0092] M CaCO3 =k×ρ CaCO3 ×V crack ;

[0093] Where, ρ CaCO3 The density of calcium carbonate;

[0094] This formula stems from the combination of geometric volume calculations and engineering safety margins. The square relationship w² of the crack volume is based on fluid mechanics and extensive experimental observations, assuming that the water conductivity of a crack is proportional to the square of its width. Therefore, the core objective of repair is to seal this water-conducting channel. The safety factor k is a commonly used method in engineering practice to cover uncertainties caused by model simplification, material inhomogeneity, and fluctuations in actual repair efficiency.

[0095] 2. Establishment and solution of microbial metabolic kinetic model.

[0096] The calcium carbonate production by microorganisms in the internal environment of concrete is a function of their quantity, activity, nutrient supply, and environmental conditions. This invention establishes the following kinetic model:

[0097] M CaCO3 =η×Y×N0×(1-e -μt )×f(pH);

[0098] Among them, M CaCO3 : The theoretical amount of calcium carbonate required, calculated from step 1; η: Comprehensive remediation efficiency coefficient (0 < η ≤ 1), used to correct for the difference between the ideal model and the real complex environment (such as uneven spore distribution and partial loss); Y: Microbial calcium carbonate production yield coefficient (g-CaCO3 / CFU), i.e., the maximum amount of calcium carbonate that a unit number of microorganisms can produce, which is determined by microbiological experiments; N0: The initial viable cell concentration of microorganisms to be solved (CFU / m³). 3 μ: Specific growth rate of microorganisms at a specific nutrient concentration (1 / day), which can be expressed by the Monod equation μ = μ max ×(C nutrient / (K s +C nutrient )) is related to nutrient concentration, where μ max For the maximum specific growth rate, Ks t: expected repair time; f(pH): pH effect function. The high alkalinity of concrete (pH>12) strongly inhibits common microorganisms. This function characterizes this inhibitory effect, where f(pH)=1 / (1+e^{β(pH-pH_opt)}), which is an sigmoid inhibition function. When the environmental pH is much higher than the optimal pH for microorganisms... opt When the pH value approaches 0, it indicates that the activity is completely inhibited; when the pH value approaches pH 10, the function value approaches 0. opt At this point, the function value rapidly increases to 1. β is the steepness coefficient, describing the intensity of the inhibitory effect.

[0099] This model draws on classical kinetic theory from bioreaction engineering. N0×(1-e -μt The term describes the cumulative non-steady-state growth of microorganisms under limited resources. The term f(pH) is an adaptive modification of the classic enzyme kinetics or microbial growth pH inhibition model, using a logistic function to simulate the common "threshold" effect in biology, which can better fit the phenomenon of a sharp decline in microbial activity near the critical pH.

[0100] 3. Calculation of nutrient concentration.

[0101] According to the stoichiometry of microbial metabolism, a specific proportion of nutrients is required to produce a certain amount of calcium carbonate. The calculation formula is as follows:

[0102] C nutrient =(M CaCO3 / Mw CaCO3 )×S n ;

[0103] Among them, C nutrient M represents the total nutrient concentration. CaCO3 This represents the theoretically required amount of calcium carbonate deposited; Mw CaCO3 S is the molar mass of calcium carbonate; n S is the stoichiometric coefficient, which is the number of moles of nutrients required to produce 1 mole of calcium carbonate. For example, if calcium nitrate (Ca(NO3)2) is used as the calcium and nitrogen source, and yeast extract is used as the carbon source, then S n It needs to be determined based on the global chemical equation of the specific metabolic pathway (such as the urease pathway or the denitrification pathway).

[0104] This formula is directly derived from the law of conservation of mass in chemical and biological reactions. The molar ratio S can be determined by using the complete or simplified biochemical reaction equation for the production of CaCO3 by microorganisms from specific nutrients. n .

[0105] 4. Conversion of material admixtures.

[0106] The microbial concentration N0 (CFU / m³) was obtained. 3 ) and nutrient concentration C nutrient (mol / m 3 Afterwards, based on the effective spore content (CFU / g) of the selected microbial agent and the purity and molecular weight of the nutrient compound, it is converted into the required mass of microbial agent to be added per cubic meter of concrete (m³). spore ) and the quality of nutrient complex (m nutrient ).

[0107] 5. Integrated mix proportion calculation.

[0108] (1) Determination and correction of water-cement ratio.

[0109] The water-cement ratio is the primary factor affecting the strength and durability of concrete. However, microbial spores and porous nutrients (such as yeast extract and light calcium carbonate) adsorb and fix some of the mixing water, resulting in a reduction in the effective water volume (W) actually used for lubricating the slurry. effective Reduce. This is equivalent to implicitly lowering the water-cement ratio, which may cause the concrete to become too dry and hard, resulting in poor workability.

[0110] Therefore, the water-cement ratio must be corrected, and the correction formula is as follows:

[0111] W effective =W total -(m spore ×k spore +m nutrient ×k nutrient );

[0112] W / C corrected =W effective / m cement ;

[0113] This formula is based on the principle of material balance. Where W... total Total water consumption; k spore and k nutrient These represent the water adsorption coefficients per unit mass of the microbial spore and nutrient complex, which can be pre-determined through a simple water absorption rate test. cement This represents the amount of cementitious material used. This correction ensures that the calculated water-cement ratio is an effective water-cement ratio that reflects the true flow state of the slurry, providing an accurate basis for subsequent calculations of admixture dosage.

[0114] (2) Calculation of aggregate usage.

[0115] The absolute volume method is adopted, which means that the volume of each cubic meter of concrete is equal to the sum of the absolute volumes of each component.

[0116] V aggregate =1-(mcement / ρ cement +W effective / ρ water +m spore / ρ spore +m nutrient / ρ nutrient +V air );

[0117] Where, ρ cement ,ρ water ,ρ spore ,ρ nutrient The apparent densities of cement, water, spores, and nutrients are respectively; V air To design the gas content volume.

[0118] The absolute volume method is the most fundamental and accurate physical principle in concrete mix design. This formula calculates the volume remaining for aggregate filling after filling with cementitious materials, effective water, repair components, and designed pores.

[0119] From this, the total mass of the aggregate can be calculated: m aggregate =V aggregate ×ρ aggregate (ρ) aggregate (This refers to the apparent density of the aggregate mixture).

[0120] (3) Determining the ratio of fine aggregate to coarse aggregate.

[0121] Based on the workability and pumpability requirements of concrete, select a suitable fine aggregate ratio (Sand Ratio). Then calculate:

[0122] m sand =m aggregate ×SandRatio;

[0123] m coarse =m aggregate ×(1-SandRatio);

[0124] Where, m sand Fine aggregate dosage; m coarse This refers to the amount of coarse aggregate used.

[0125] The selection of fine aggregate ratio relies on charts or databases summarizing extensive engineering experience, with the goal of forming the densest packing structure and good workability.

[0126] (4) Calculation of the amount of admixture.

[0127] To compensate for the loss of flowability caused by water absorption by the repair components, a high-efficiency water-reducing agent must be used. Its dosage is not a fixed value but is related to changes in the system. This invention establishes the following model:

[0128] m superplasticizer =A×(W / C base -W / C corrected ) / (W / C corrected )+B×(m spore +m nutrient ) / m cement ;

[0129] This model is a semi-empirical, semi-theoretical formula:

[0130] ① The first term A×(W / C) base -W / C corrected ) / (W / C corrected This represents the increased demand for water-reducing agents due to a decrease in the effective water-cement ratio. The W / C ratio in the denominator... corrected This demonstrates the nonlinear relationship that the efficiency of the water-reducing agent varies at low water-cement ratios. The coefficient A is fitted by measuring the amount of water-reducing agent required to achieve the target flowability at different water-cement ratios.

[0131] ② The second term B×(m) spore +m nutrient ) / m cement The coefficient B characterizes the negative impact of the solid particles in the remediation components on flowability (e.g., increased specific surface area, introduction of irregularly shaped particles). The higher the concentration of these particles relative to the cementitious material, the greater the demand for water-reducing agents. The coefficient B was fitted using flowability experiments with varying remediation component concentrations while maintaining a fixed water-cement ratio.

[0132] Through the above integrated calculations, a complete, quantitative, and feasible mix proportion is finally output, which includes cementitious materials, effective water, microbial spores, nutrients, fine aggregates, coarse aggregates, and water-reducing agents, fundamentally solving the problem of synergy between repair function and matrix performance.

[0133] A microbial self-healing concrete mix design system, such as Figure 2 As shown, it includes: a data input module, a core calculation module, and a result output module.

[0134] Data input module: Used to receive user-defined repair target parameters, selected types of microorganisms and nutrients, and baseline concrete performance requirements.

[0135] Core calculation module: Built-in microbial metabolic kinetics model and ratio conversion algorithm, used to perform calculations based on input parameters to solve for the optimal microbial and nutrient content.

[0136] The core computing module also includes an optimization submodule, which uses an iterative algorithm to perform multi-objective optimization of microbial content, nutrient content, and water-cement ratio with the goal of maximizing the repair efficiency-cost ratio or minimizing the total material cost.

[0137] Results output module: Used to generate and display a complete concrete mix design report, including the amount of each component material, predicted repair performance, and basic mechanical properties of the concrete.

[0138] The design process of the present invention is described in detail below through non-limiting embodiments. Comparative Example 1 is a manual design process based on calculation formulas, designed to clearly demonstrate the core calculation logic of the present invention; Example 1 is an automated design process implemented using the design system of the present invention, designed to demonstrate the efficiency and convenience of the present invention in practice.

[0139] Comparative Example 1: Manual Calculation Design Method.

[0140] With the goal of preparing C30 self-healing concrete to repair microcracks with a width of 0.2mm, the manual calculation process of the mix proportion is shown in detail.

[0141] 1. Set basic parameters:

[0142] (1) Concrete target: strength grade C30, slump requirement is 180±20mm.

[0143] (2) Repair objectives: crack width w=0.2mm, repair time t=28d, repair efficiency coefficient η=0.5.

[0144] (3) Material parameters:

[0145] ① Cement: P.O42.5, density ρ cement =3100kg / m 3 Dosage m cement =380kg / m 3 .

[0146] ② Microorganisms: Bacillus pasteurellium spore powder, effective viable count 2×10 10 CFU / g, density ρ spore =1100kg / m 3 Water absorption coefficient k spore =0.3.

[0147] ③Nutrients: Calcium nitrate and yeast extract complex, density ρ nutrient =1500kg / m 3 Water absorption coefficient k nutrient =0.6.

[0148] ④ Aggregate: Medium sand, apparent density ρ sand =2650kg / m 3 Crushed stone, particle size 5-20mm, apparent density ρ coarse =2700kg / m 3 .

[0149] ⑤ Water-reducing agent: Polycarboxylate-based high-performance water-reducing agent with a solid content of 40%.

[0150] (4) Model constants:

[0151] ①k=1.8, α=1.0, L=100m / m 3 (Estimated)

[0152] ②Y=5×10 -8 g / CFU, μ=0.15day -1 pH=12.5, pH opt =9.5, β=1.5.

[0153] ③S n =1.2 mol_nutrient / mol_CaCO3 (simplified quantification based on the denitrification pathway).

[0154] 2. Calculate the theoretically required amount of calcium carbonate, M. CaCO3 :

[0155] V crack =α×w 2 ×L=1.0×(0.0002) 2 ×100=4×10 -6 m 3 ;

[0156] M CaCO3 =k×ρ CaCO3 ×V crack =1.8×2710kg / m 3 ×4×10 -6 m 3 ≈0.0195kg / m 3 (i.e., 19.5g / m) 3 ).

[0157] 3. Calculate the amount of microorganisms and nutrients added:

[0158] (1) Calculate the pH effect function:

[0159] f(pH) = 1 / (1 + e^{β×(pH - pH)) opt )})=1 / (1+e^{1.5×(12.5-9.5)})=1 / (1+e^{4.5})≈0.011.

[0160] (2) Calculate N0 based on the dynamic model:

[0161] M CaCO3 =η×Y×N0×(1-e^{-μt})×f(pH);

[0162] 0.0195=0.5×(5×10^{-8})×N0×(1-e^{-0.15×28})×0.011;

[0163] The calculation yields N0≈7.2×10 7 CFU / m 3 .

[0164] (3) Calculate the mass of microbial spore powder:

[0165] m spore =N0 / (live bacteria count)=(7.2×10) 7 CFU / m 3 ) / (2×10 10 CFU / g) = 0.0036 kg / m 3 (i.e., 3.6g / m) 3 ).

[0166] (4) Calculate nutrient concentration and mass:

[0167] C nutrient =(M CaCO3 / Mw CaCO3 )×S n =(0.0195kg / 0.1kg / mol)×1.2=0.234mol / m 3 ;

[0168] m nutrient =C nutrient ×Mw nutrient (Assuming the average molar mass of the nutrient complex is 0.2 kg / mol);

[0169] m nutrient ≈0.234mol / m 3 ×0.2kg / mol=0.0468kg / m 3 (i.e., 46.8g / m) 3 ).

[0170] 4. Integrated mix proportion calculation:

[0171] (1) Determine the baseline water consumption and the corrected water-cement ratio:

[0172] Based on experience with C30 and 180mm slump, a baseline total water consumption W is set. total =195kg / m 3 .

[0173] Reference water-cement ratio W / C base =195 / 380≈0.513.

[0174] (2) Calculate the effective water consumption:

[0175] W effective =W total -(m spore ×k spore +m nutrient ×k nutrient );

[0176] W effective =195-(0.0036×0.3+0.0468×0.6)≈194.97kg;

[0177] Corrected water-cement ratio W / C corrected =194.97 / 380≈0.513. In this example, because the dosage of the repair component is extremely low, the correction amount can be ignored.

[0178] (3) Calculate the total volume of aggregate:

[0179] Design gas content V air =0.02m 3 .

[0180] V aggregate =1-(m cement / ρ cement +W effective / ρ water +m spore / ρ spore +m nutrient / ρ nutrient +V air );

[0181] V aggregate =1-(380 / 3100+194.97 / 1000+0.0036 / 1100+0.0468 / 1500+0.02)≈0.6624m 3 ;

[0182] Total aggregate mass m aggregate =V aggregate ×ρ aggregate (Assuming the mixed density is 2670 kg / m³) ≈ 0.6624 × 2670 ≈ 1768.6 kg.

[0183] (4) Determine the amount of sand and gravel to be used:

[0184] The fine aggregate ratio SandRatio was selected as 40%.

[0185] m sand =1768.6kg × 0.40 = 707.4kg.

[0186] m coarse =1768.6kg × 0.60 = 1061.2kg.

[0187] (5) Calculate the amount of water-reducing agent:

[0188] Use empirical coefficients A=0.8, B=0.5.

[0189] m superplasticizer =A×(W / C base -W / C corrected ) / (W / C corrected )+B×(m spore +m nutrient ) / m cement ;

[0190] Due to W / C base ≈W / C corrected The first term is approximately 0.

[0191] m superplasticizer ≈0 + 0.5 × (0.0036 + 0.0468) / 380 ≈ 6.63 × 10 -5 kg (solid content);

[0192] Equivalent to a 40% concentration of commercial water-reducing agent: (6.63 × 10⁻⁶) -5 (0.4)×1000≈0.17g / m 3 If this value is too low, add the minimum recommended dosage by the manufacturer (usually 0.2% to 0.4% of the adhesive material weight), tentatively set at 1.0 kg / m³. 3 (commercial liquid).

[0193] 5. Final mix proportion (per cubic meter):

[0194] Cement: 380kg; Water: 195kg; Microbial spore powder: 3.6g; Nutrient compound agent: 46.8g; Medium sand: 707kg; Crushed stone: 1061kg; Polycarboxylate superplasticizer (40% concentration): 1.0kg.

[0195] Example 1: An automated calculation method based on a design system.

[0196] Example 1 uses the same design objectives and basic parameters as Comparative Example 1 to demonstrate how to quickly complete the mix design using the design system.

[0197] 1. System input:

[0198] (1) The user enters the following information in the data input module interface:

[0199] Performance requirements: Strength grade C30, slump 180mm; Repair target: crack width 0.2mm, repair period 28 days; Material library selection: Select "P.O42.5 cement" and "Bacillus pasteurellium spore powder (2e)" from the drop-down menu.10 “CFU / g”, “Calcium nitrate-yeast extract compound nutrients”, “Medium sand”, “5-20mm crushed stone”, “Polycarboxylate superplasticizer (40%)”.

[0200] (2) Model parameter confirmation: The system default model constants are used (the same as Comparative Example 1), and users can also make fine adjustments based on the experimental data of specific strains.

[0201] 2. System Calculation and Optimization:

[0202] After the user clicks the "Calculate" button, the core calculation module automatically executes the following process:

[0203] (1) Call the built-in repair model to calculate M CaCO3 =19.5g / m 3 .

[0204] (2) Run the microbial kinetic model and calculate the optimal microbial dosage m. spore =3.6g / m 3 Nutrient content m nutrient =47g / m 3 (The system rounds the numbers.)

[0205] (3) Startup of the integrated mix proportion calculation submodule:

[0206] ①Based on the strength-water-cement ratio database, the system intelligently recommends a baseline water-cement ratio of 0.51 and a water consumption of 195 kg.

[0207] ②Based on the input k spore and k nutrient It automatically corrects the effective water consumption and water-cement ratio.

[0208] ③ Based on the absolute volume method and the system aggregate gradation optimization algorithm, calculate and optimize the sand and gravel ratio, and output m. sand =708kg,m coarse =1060kg.

[0209] (4) Optimization of sub-module intervention:

[0210] The system performs iterative calculations with the goal of achieving the lowest total material cost. Considering that manual calculations are impractical due to excessively low water-reducing agent dosage, the system automatically adjusts the scheme: slightly reducing the baseline water consumption to 193 kg and correspondingly increasing the recommended water-reducing agent dosage to 0.3% of the adhesive material weight, i.e., 1.14 kg / m³, to ensure good workability.

[0211] 3. System output:

[0212] The results output module immediately generates a clear, formatted mix design report, including:

[0213] (1) Final mix proportion: cement: 380kg; water: 193kg; microbial spore powder: 3.6g; nutrient compound agent: 47g; medium sand: 708kg; crushed stone: 1060kg; polycarboxylate superplasticizer (40%): 1.14kg.

[0214] (2) Performance prediction: Predicted 28-day compressive strength: ≥35MPa; predicted slump: 175-185mm; theoretical repair capability: can effectively seal cracks with a width ≤0.22mm.

[0215] (3) Cost estimation: Displays the estimated material cost per cubic meter of concrete.

[0216] Comparison and advantages: By comparing Comparative Example 1 (manual calculation) and Example 1 (computer calculation), it can be seen that the design system of the present invention not only completely replicates all the logic of manual calculation, but also, through its built-in optimization algorithm and engineering database, can quickly process complex parameters, avoid human error, and automatically seek more economical and easier-to-construct mix design schemes while meeting all performance requirements, thus greatly improving design efficiency and quality.

[0217] To verify the actual effect of the mix proportion designed according to the present invention, trial mixing and performance testing were conducted on the final mix proportion generated by the system in Example 1, and compared with the benchmark concrete without the addition of repair components.

[0218] 1. Trial fitting and mechanical property testing

[0219] (1) Experimental group: Concrete specimens were prepared strictly according to the final mix proportion of Example 1 (including 3.6 g / m³ of microbial spore powder and 47 g / m³ of nutrients).

[0220] (2) Baseline group: Except for the absence of microbial spore powder and nutrients, the dosage of other components (cement, water, aggregate, water-reducing agent) is exactly the same as that of the experimental group.

[0221] (3) Test method: Refer to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2019) to test the compressive strength and flexural strength at 7 days and 28 days.

[0222] (4) Test results:

[0223] The strength test results are shown in the table below.

[0224] Table 1 Comparison of Intensity Between the Baseline and Experimental Groups

[0225] Results Analysis: The strength of the experimental group at each age was within 3% of that of the benchmark group. This indicates that the addition of the trace repair component calculated according to the method of this invention did not have a significant negative impact on the macroscopic mechanical properties of concrete, proving the effectiveness of this invention in ensuring structural performance.

[0226] 2. Self-healing performance test

[0227] Specimen preparation: A rectangular specimen of 40mm×40mm×160mm was used. After 28 days of standard curing, a crack with a width of approximately 0.6mm~0.7mm was prefabricated.

[0228] Repair conditions: The pre-cracked specimens were placed in an environment with a temperature of 20°C and a humidity of over 95% for curing to activate the microbial repair function.

[0229] 3. Observation and Evaluation:

[0230] (1) Apparent observation: Comparison of self-healing effects between the reference group specimens and the experimental group specimens. Figure 3 , Figure 4 As shown, white precipitate gradually formed and covered the crack surface of the test group specimens, and by 28 days, the crack entrance was basically sealed. In contrast, the crack surface of the baseline group specimens showed no change.

[0231] (2) Water seepage performance test: After 28 days of repair and maintenance, a crack water seepage test was conducted. The crack of the specimen was placed facing a water tank with a water pressure of 0.1 MPa for 30 minutes.

[0232] ① Baseline group: There is obvious water seepage at the crack.

[0233] ② Test group: No water droplets seeped out from the cracks, only the surface was damp.

[0234] (3) Quantitative analysis of healing: The repaired specimen was split, and the area filled with calcium carbonate at the crack cross-section was measured using image analysis software. The average healing rate of the crack (calcium carbonate filling area / original crack area) reached 65%, which met the preset repair target.

[0235] Experimental Verification Conclusion: The above-mentioned systematic experimental verification shows that, based on the design method and system calculation of the self-healing concrete mix proportion provided by this invention, effective self-healing of microcracks has been successfully achieved while ensuring that the basic mechanical properties of concrete do not deteriorate. This fully demonstrates the scientific nature, accuracy, and engineering practical value of the quantitative design model and integrated calculation method proposed in this invention.

[0236] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for designing the mix proportion of microbial self-healing concrete, characterized in that, Includes the following steps: S1. Determine the concrete performance requirements; S2. Determine the target parameters for repair, including the target crack width w, the expected repair time t, and the repair efficiency coefficient η; S3. Based on the target repair parameters, calculate the theoretically required amount of calcium carbonate deposition, M. CaCO3 ; S4. Establish a microbial metabolic kinetic model based on the theoretically required calcium carbonate deposition amount M. CaCO3 And the internal pH value of the concrete, calculate the initial viable microbial concentration N0 and the total nutrient concentration C. nutrient ; S5. The initial viable microbial concentration N0 and the total nutrient concentration C nutrient This translates into specific material dosages in concrete, including the dosage of microbial spores (m). spore Dosage of nutrient complex agent m nutrient ; S6. Perform integrated mix proportion calculation, specifically as follows: S6.1 Determine the baseline water-cement ratio W / C base Based on the water absorption capacity of nutrients and microbial spores and their impact on flowability, the effective water consumption W is calculated. effective And the corrected water-cement ratio W / C corrected ; S6.

2. Based on the absolute volume method, calculate the required total aggregate volume V according to the target bulk density, cementitious material dosage, effective water dosage, and the volume of microorganisms and nutrients. aggregate ; S6.

3. Based on aggregate gradation theory and workability requirements, determine the fine aggregate ratio and calculate the fine aggregate dosage m. sand Coarse aggregate usage (m) coarse ; S6.

4. Based on the corrected water-cement ratio and flowability requirements, the water-reducing agent dosage m is calculated using the flowability-admixture dosage relationship model. superplasticizer ; S6.5, The final output is a complete self-healing concrete mix design.

2. The method for designing the mix proportion of microbial self-healing concrete according to claim 1, characterized in that, In step S3, the theoretically required amount of calcium carbonate deposition M CaCO3 Calculated using the following formula: M CaCO3 =k×ρ CaCO3 ×V crack ; in, V crack =α×w 2 ×L represents the approximate volume of the crack to be repaired; k is the safety factor, which ranges from 1.5 to 2.0; ρ CaCO3 The density of calcium carbonate; α is the crack morphology coefficient; L is the estimated total length of cracks per unit volume of concrete. w represents the target crack width.

3. The method for designing the mix proportion of microbial self-healing concrete according to claim 1, characterized in that, In step S4, the core formula of the microbial metabolic kinetics model is: M CaCO3 =η×Y×N0×(1-e -μt )×f(pH); in, Y is the yield coefficient of calcium carbonate produced by microorganisms; μ represents the specific growth rate of microorganisms under preset nutrient conditions; f(pH) is the pH effect function, characterizing the degree of inhibition of microbial activity by the alkaline environment of concrete. Its expression is f(pH) = 1 / (1 + e^{β(pH - pH) ... opt )}), β is the inhibition coefficient, pH opt This is the optimal pH value for microorganisms.

4. The method for designing the mix proportion of microbial self-healing concrete according to claim 3, characterized in that, In step S4, the total nutrient concentration C nutrient Calculated using the nutrient consumption measurement formula: C nutrient =(I CaCO3 / Mw CaCO3 )×S n ; in, Mw CaCO3 This is the molar mass of calcium carbonate. S n The number of moles of nutrient required to produce one mole of calcium carbonate is determined based on the specific stoichiometric relationship of the selected nutrient.

5. The method for designing the mix proportion of microbial self-healing concrete according to claim 1, characterized in that, In step S6.1, the corrected water-cement ratio W / C corrected Calculated using the following formula: W effective =W total -(m spore ×k spore +m nutrient ×k nutrient ); W / C corrected =W effective / m cement ; in, W total This represents the total water consumption. k spore and k nutrient These are the water adsorption coefficients per unit mass of the microbial spore and nutrient complex; m cement This refers to the amount of cementitious material used.

6. The method for designing the mix proportion of microbial self-healing concrete according to claim 5, characterized in that, In step S6.2, the total aggregate volume V aggregate Calculated using the absolute volume method: V aggregate =1-(m cement / r cement +W effective / r water +m spore / r spore +m nutrient / r nutrient +V air ); in, ρ cement ,ρ water ,ρ spore ,ρ nutrient The apparent densities are those of cement, water, spores, and nutrients, respectively. V air To design the gas content volume.

7. The method for designing the mix proportion of microbial self-healing concrete according to claim 6, characterized in that, In step S6.4, the amount of water-reducing agent m superplasticizer Determined through the following model: m superplasticizer =A×(W / C base -W / C corrected ) / (W / C corrected )+B×(m spore +m nutrient ) / m cement ; in, A and B are coefficients obtained by fitting experimental data, representing the sensitivity to changes in water-cement ratio and the compensation effect on the loss of fluidity introduced by solid admixtures, respectively.

8. A microbial self-healing concrete mix design system, characterized in that, A method for designing the mix proportion of microbial self-healing concrete as described in any one of claims 1-7 includes: Data input module: used to receive user-defined repair target parameters, selected microorganisms and nutrient types, selected material properties, and baseline concrete performance requirements; Core calculation module: Built-in microbial metabolic kinetics model and integrated ratio calculation algorithm, used to perform calculations based on input parameters to solve for the optimal microbial and nutrient content and complete ratio; Results output module: Used to generate and display a complete concrete mix design report, including the amount of each component material, predicted repair performance, and concrete mechanical properties.

9. The microbial self-healing concrete mix design system according to claim 8, characterized in that, The core computing module also includes an optimization submodule. The optimization submodule uses an iterative algorithm to perform multi-objective optimization of parameters such as microbial dosage, nutrient dosage, and water-cement ratio, with the goal of maximizing the repair efficiency-cost ratio or minimizing the total material cost.

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