A method for constructing a prediction model for the slow setting performance of silicate cement and its calculation and analysis instrument

Abstract

The present invention discloses a method for constructing a prediction model of the retarding performance of silicate cement and a calculation analyzer thereof, the method comprising the following steps: 1) establishing a control equation for the hydration process of tricalcium silicate under the influence of sodium gluconate in view of the two retarding mechanisms of sodium gluconate, namely, adsorption and complex reaction; 2) establishing a hydration exothermic rate equation of tricalcium silicate under the influence of sodium gluconate in combination with the hydration exothermic characteristics of tricalcium silicate under the influence of sodium gluconate, and obtaining a prediction model of the retarding performance of tricalcium silicate hydration process by sodium gluconate. The method for constructing a prediction model of the retarding performance of silicate cement proposed by the present invention can not only effectively improve the use efficiency of sodium gluconate retarder in actual engineering, but also provide new ideas and new tools for the performance regulation research of admixtures in the hydration process of cement-based materials.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis methods, and in particular relates to a method for constructing a prediction model for the slow-setting performance of silicate cement and a calculation analyzer thereof. Background Art

[0002] In order to cope with the rapid development of my country's economy and the growing demand for transportation, bridge technology is also constantly developing and following up. From the original cross-river bridges to the current cross-sea bridges and mountain bridges, the development of bridge technology has effectively promoted the sustained and efficient development of economic construction. Compared with the structural form, concrete materials are the most widely used bridge construction materials. The performance of concrete materials is the key to ensuring that bridges are still safe and reliable in harsh environments such as deep sea and high altitude. In the process of concrete technology development, the invention and application of chemical admixtures are recognized as the third technological leap in the field of concrete technology after reinforced concrete and prestressed reinforced concrete technology. In recent years, the substantial improvement in the performance of concrete materials and the rapid development of construction technology mainly rely on the improvement of the performance of chemical admixtures and the popularization of their application. Chemical admixtures have become the fifth important component of concrete, and are also indispensable materials for the preparation of high-performance concrete with good construction performance, high strength and good durability.

[0003] At present, in terms of engineering applications, experimental test methods or empirical formulas are mainly used for the use of retarders. However, experimental methods are time-consuming, labor-intensive and costly, and the applicability of empirical formulas is relatively narrow. Therefore, there is a lack of a convenient, fast and highly applicable method to guide the use of retarders in engineering. In terms of the design and preparation of admixtures, the current research methods on the mechanism of admixtures have fallen into a bottleneck and it is difficult to make breakthroughs. For example, previous studies generally believed that the addition of sodium gluconate (SG) retarder would delay the hydration of silicate cement. The mechanism of SG delaying the hydration of silicate cement is attributed to: 1) adsorption, SG is adsorbed on the surface of cement minerals or hydration products, hindering the dissolution of cement mineral phases or reducing CSH nucleation sites, resulting in a slowdown in the cement hydration rate; 2) complexation reaction, the carboxyl group in SG can complex the free calcium ions in the solution, reduce the concentration of free calcium ions in the liquid phase, and prolong the time required to reach supersaturation, thereby causing retardation. As to which of the above two effects is the main reason for the delay in silicate cement hydration, it is still under exploration. However, existing research on the use of sodium gluconate retarder to delay the hydration of silicate cement is mostly based on experimental methods, and most of them remain at the level of qualitative description, with insufficient quantitative analysis and no corresponding theoretical model for in-depth research. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for constructing a prediction model for the retarding performance of silicate cement in view of the deficiencies in the prior art. Tricalcium silicate (C3S) is the main component of silicate cement, so it is taken as the direct object of model construction. The method provided by the present invention analyzes the influence of the addition of sodium gluconate retarder on important change processes such as particle dissolution, product precipitation, ion diffusion, hydration exotherm, etc. in the hydration process of C3S, and establishes a theoretical model of the hydration reaction process of sodium gluconate retarder and C3S. The action mechanism of sodium gluconate retarder on the hydration process of C3S can be theoretically verified. At the same time, a quantitative analysis method for the hydration retarding effect of C3S by adsorption and complex reaction is proposed, which provides new ideas and new tools for the performance regulation research of admixtures in the hydration process of cement-based materials.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is:

[0006] A method for constructing a prediction model for the slow setting performance of silicate cement, characterized by comprising the following steps:

[0007] (1) According to the adsorption and complexation reaction of sodium gluconate in the hydration process of tricalcium silicate in Portland cement, the control equation of the hydration process of tricalcium silicate under the influence of sodium gluconate was established based on the obstacle theory and complexation reaction kinetics;

[0008] (2) By superimposing the heat release of water adsorption during the initial contact process of tricalcium silicate and the heat release of chemical reactions during the hydration process, a formula for calculating the heat release rate of the entire hydration process of tricalcium silicate under the influence of sodium gluconate was established. Then, based on the concentrations of various ions calculated by the control equation of the hydration process of tricalcium silicate under the influence of sodium gluconate, the heat release rate curve was calculated, and the effects of different sodium gluconate dosages on the heat release rate of tricalcium silicate hydration were analyzed. A prediction model for the retarding performance of tricalcium silicate hydration process with sodium gluconate was obtained.

[0009] In the above scheme, according to the barrier theory, the presence of the adsorption layer formed by sodium gluconate molecules on the surface of the C3S particles in step (1) hinders the contact between water and the C3S particles. Therefore, the adsorption layer acts as a sieve, allowing water molecules to pass only when they can pass through the free space in the adsorption layer. In the model proposed based on this theory, sodium gluconate molecules are considered to be randomly adsorbed on the surface of the C3S particles. Therefore, the size of the free space is defined as follows: a random origin is taken in the adsorption layer, and a circular surface is expanded from this point until the nearest sodium gluconate molecule center is reached. The calculation steps of the differential pore distribution function are:

[0010] like Figure 1As shown, origin is the origin. Since the movement of water molecules through the adsorption layer composed of sodium gluconate molecules is modeled on a two-dimensional plane, the number of sodium gluconate molecules centered between L and (L+dL) is derived as follows:

[0011]

[0012] Where dn is the number of sodium gluconate molecules centered between L and (L+dL); is the number of sodium gluconate molecules per unit area of ​​the adsorption layer.

[0013] The probability that the space is between L and (L+dL) is defined as the combined probability that no contact occurs within a distance L from the origin and at least one contact occurs between L and (L+dL). The derivation steps are as follows:

[0014]

[0015] dP1=exp(-λΛ) (29)

[0016] dP2=1-exp(-λdΛ)=λdΛ (30)

[0017] dP=λdΛexp(-λΛ) (31)

[0018]

[0019] Wherein, λ is the rectangular distribution density; Λ is the rectangular distribution range; dΛ is the infinitesimal element of the rectangular distribution range; dP1, dP2 and dP are the probability that the edge of the pores in the adsorption layer has no contact with sodium gluconate, the probability that the edge of the pores in the adsorption layer has at least one contact with sodium gluconate, and the probability that the edge of the pores in the adsorption layer has the first contact with sodium gluconate; g(L) is the differential pore distribution function.

[0020] In the above scheme, in step (1), according to the adsorption layer formed by the adsorption of sodium gluconate on the surface of tricalcium silicate particles, a calculation formula for the ion diffusion coefficient of tricalcium silicate hydration process based on the obstacle theory is established, as shown in the following formulas 1 to 4:

[0021]

[0022]

[0023]

[0024]

[0025] In the formula, the subscript i represents the type of ion, which are Ca 2+, H3SiO4- and OH-; P r is the barrier coefficient; g(L) is the differential pore distribution function; L is the pore radius of the adsorption layer; dL is the microelement of the pore radius of the adsorption layer; is the number of sodium gluconate molecules per unit area of ​​the adsorption layer; r w and r SG are the radii of water molecule and sodium gluconate molecule respectively; M ads is the adsorption ratio; N A is Avogadro's constant; M w is the relative molecular mass of sodium gluconate molecule; η is the dosage of sodium gluconate; t ads is the time to reach saturated adsorption; D i , and are the diffusion coefficients of different ion types, the initial diffusion coefficients and the equilibrium diffusion coefficients respectively.

[0026] In the above scheme, the carboxyl group of calcium gluconate in step (1) reacts with the free calcium ions generated by the hydration of C3S in the liquid phase to form a complex. Therefore, assuming that some free calcium ions generated by the dissolution of C3S are consumed by the complex reaction, thereby reducing the concentration of free calcium ions in the solution phase and prolonging the time required to achieve supersaturation, the solubility is determined by the thermodynamic solubility product (calcium gluconate complex with a stoichiometric ratio of 1:1) and increases with the increase of ionic strength. The complex reaction rate calculation formula based on the complex reaction kinetics is established, as shown in the following formulas 5 to 9:

[0027]

[0028]

[0029]

[0030]

[0031]

[0032] In the formula, v complex is the complexation reaction rate; k complex and K complex are the rate constant and equilibrium constant of the complex reaction respectively; α i , γ i , I and z i are the chemical activity of different ion types, the chemical activity coefficient of different ion types, the ionic strength and the balancing coefficient; c i is the concentration of different ion types; A is the characteristic parameter of ion activity; e0, ε rand ε0 are the basic charge number, the dielectric constant of water, and the dielectric constant of vacuum, respectively; T, F, and R are the temperature, Faraday constant, and ideal gas constant, respectively.

[0033] In the above scheme, the Poisson-Nernst-Planck equation is used in step (1) and a multi-physics, multi-scale and multi-driving model of C3S hydration is proposed by solving the theory. The thermal-chemical-electric coupling field in the C3S hydration process is used to establish the Nernst-Planck, Poisson and heat conduction equations. The effects of adsorption and complexation reaction are considered at the same time, and the control equations of the tricalcium silicate hydration process under the influence of sodium gluconate are established, as shown in the following equations 10 to 19:

[0034]

[0035]

[0036] In the formula, is the Hamiltonian operator, and are divergence and gradient respectively; c i , t and J i They are the concentration of different types of ions, time variables and diffusion fluxes; and They are the stoichiometric constants of different types of ions in the precipitation of calcium silicate hydrate, calcium hydroxide precipitation and the complexation of calcium ions with sodium gluconate; v CSH , v CH and v complex are the C3S dissolution rate, CSH deposition rate, CH deposition rate and complex reaction rate respectively; D i , z i and γ i are the diffusion coefficient, balancing coefficient and chemical activity coefficient of different ion types respectively; ψ is the electric potential; k CSH and k CH They are the dissolution rate constant of tricalcium silicate, the precipitation rate constant of hydrated calcium silicate and the precipitation rate constant of calcium hydroxide respectively; and are the specific surface area of ​​tricalcium silicate, the molar mass of tricalcium silicate and the surface area of ​​tricalcium silicate particles per unit volume of hydrated slurry; β CSH is the characteristic variable of the activity product; K CH and K CSH They are the supersaturation concentration of different types of ions, the equilibrium constant of calcium hydroxide and the equilibrium constant of calcium silicate hydrate; and t mixare the adsorption energy of water on the surface of tricalcium silicate particles per unit volume and the stirring time; w / c is the water-cement ratio; ρ P , C P and k P They are respectively the density of C3S hydrated slurry, the specific heat capacity of C3S hydrated slurry and the thermal conductivity of C3S hydrated slurry; and are the densities of water and tricalcium silicate, respectively; and are the specific heat capacities of water and tricalcium silicate respectively; α i is the chemical activity of different ion types; T, F and R are temperature, Faraday constant and ideal gas constant respectively; ε r and ε0 are the dielectric constants of water and vacuum, respectively.

[0037] In the above scheme, in step (2), a heat release rate calculation formula for the whole process of tricalcium silicate hydration under the influence of sodium gluconate is established, as shown in the following equations 20 to 26:

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044] In the formula, and They are the whole process heat release rate, short-range heat release rate and long-range heat release rate respectively; E ads and E a are the adsorption energy of water on the surface of tricalcium silicate particles per unit mass, the adsorption energy of water on the surface of tricalcium silicate particles per unit mole, and the activation energy of the hydration reaction of tricalcium silicate; t ads is the adsorption time; w / c is the water-cement ratio; β S , β L and τ are short-range characteristic parameter, long-range characteristic parameter and characteristic time respectively; is the specific heat capacity of tricalcium silicate; η is the dosage; is the specific surface area of ​​C3S; K complex is the complexation reaction equilibrium constant; h P and H C3S are the convective heat transfer coefficient of tricalcium silicate hydrate slurry and the heat released by complete hydration of unit mole of tricalcium silicate; Q fin, dξ and dt are the total accumulated heat, distance microelement and time microelement during the reaction time, respectively; t total and l are the total calculation time and the calculation domain length respectively; v CSH is the deposition rate of CSH.

[0045] The present invention also claims a computing analyzer using the above-mentioned silicate cement slow setting performance prediction model, which includes an input module, a computing module and an output module;

[0046] The input module is used to input the initial parameters required for the calculation of the hydration process of tricalcium silicate doped with sodium gluconate;

[0047] A calculation module is used to establish a control equation for the hydration process of tricalcium silicate under the influence of sodium gluconate based on the adsorption and complex reaction effects of sodium gluconate in the hydration process of tricalcium silicate in silicate cement, based on the obstacle theory and complex reaction kinetics; a heat release rate calculation formula for the whole hydration process of tricalcium silicate under the influence of sodium gluconate is established by superimposing the heat release of water adsorption of tricalcium silicate in the initial contact process and the heat release of chemical reaction in the hydration process; then, the heat release rate curve is calculated based on the various ion concentrations calculated by the control equation, the influence of different sodium gluconate dosages on the heat release rate of tricalcium silicate hydration is analyzed, and a prediction model for the retarding performance of sodium gluconate in the hydration process of tricalcium silicate is obtained;

[0048] The output module is used to output the model calculation results of the hydration process of tricalcium silicate under the influence of sodium gluconate.

[0049] In the above scheme, the computing analyzer of the silicate cement retarding performance prediction model comprises the following hardware:

[0050] A memory, used for storing intermediate variables and final results when calculating a prediction model of the retarding performance of tricalcium silicate hydration process by sodium gluconate;

[0051] The arithmetic unit is the core part of the hardware configuration, connected to the processor, and is used to realize the software functions and algorithms of the input module, calculation module and output module in the calculation analyzer;

[0052] An input device, connected to the processor, for manually inputting measured parameter values ​​to be processed and calculated;

[0053] The display is connected to the processor and is used to display the intermediate variables and final results calculated by the calculation analyzer.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1) The present invention obtains the influence of the dosage of sodium gluconate retarder on the retarding performance of silicate cement (tricalcium silicate) through theoretical calculation, thereby providing certain theoretical guidance for concrete mix design.

[0056] 2) The present invention compares and quantitatively analyzes the two mechanisms of adsorption and complex reaction, thereby concluding that adsorption is the dominant effect of sodium gluconate in delaying the hydration of tricalcium silicate, which essentially reveals the influence of admixtures on cement hydration and provides an effective theoretical tool for the design and preparation of admixtures.

[0057] 3) The present invention has wide applicability and can be easily extended to the theoretical research of other admixtures with similar action mechanisms. It has important theoretical significance and practical value in guiding the use, design and preparation of admixtures. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The figure is a schematic diagram of the derivation of the differential pore distribution function in the process of hindering hydration of the surface of tricalcium silicate particles adsorbed by sodium gluconate according to the present invention; in the figure, origin is the origin.

[0059] Figure 2 The present invention is a schematic diagram of a calculation analyzer for predicting the retarding performance of sodium gluconate in the hydration process of tricalcium silicate.

[0060] Figure 3 The present invention is a schematic diagram of the calculation process of the prediction model of the retarding performance of sodium gluconate in the hydration process of tricalcium silicate.

[0061] Figure 4 This is a graph showing the change in heat release rate of tricalcium silicate hydration over time at different sodium gluconate dosages calculated using the method described in Example 1.

[0062] Figure 5 This is a graph showing the change in the exothermic rate of hydration of tricalcium silicate over time under the influence of different adsorption parameters and complexation parameters calculated by the method described in Example 2 (large changes in adsorption parameters).

[0063] Figure 6 This is a graph showing the change in the exothermic rate of hydration of tricalcium silicate over time under the influence of different adsorption parameters and complexation parameters calculated by the method described in Example 2 (large changes in complexation parameters). DETAILED DESCRIPTION

[0064] The technical solution of the present invention will be fully and clearly described below in conjunction with specific embodiments, but the described embodiments are only some embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0065] In the following embodiments, a method for constructing a prediction model for the retarding properties of tricalcium silicate is first provided, which mainly comprises the following steps:

[0066] 1) Aiming at the two retarding mechanisms of sodium gluconate, adsorption and complex reaction, the control equation of tricalcium silicate hydration process under the influence of sodium gluconate was established based on the hindering theory and complex reaction kinetics;

[0067] 2) Combined with the hydration exothermic characteristics of tricalcium silicate under the influence of sodium gluconate, the hydration exothermic rate equation of tricalcium silicate under the influence of sodium gluconate was established, and the influence of different sodium gluconate dosages on the hydration exothermic rate of tricalcium silicate was calculated, and a prediction model for the retarding performance of tricalcium silicate hydration process with sodium gluconate was obtained.

[0068] The method specifically comprises the following steps:

[0069] (1) Establishment of differential pore distribution equation

[0070] like Figure 1 As shown, since the movement of water molecules through the adsorption layer composed of sodium gluconate molecules is modeled on a two-dimensional plane, the number of sodium gluconate molecules centered between L and (L+dL) is derived as follows:

[0071]

[0072] Where dn is the number of sodium gluconate molecules centered between L and (L+dL); is the number of sodium gluconate molecules per unit area of ​​the adsorption layer.

[0073] The probability that the space is between L and (L+dL) is defined as the combined probability that no contact occurs within a distance L from the origin and at least one contact occurs between L and (L+dL). The derivation steps are as follows:

[0074]

[0075] dP1=exp(-λΛ) (29)

[0076] dP2=1-exp(-λdΛ)=λdΛ (30)

[0077] dP=λdΛexp(-λΛ) (31)

[0078]

[0079] Wherein, λ is the rectangular distribution density; Λ is the rectangular distribution range; dΛ is the infinitesimal element of the rectangular distribution range; dP1, dP2 and dP are the probability that the edge of the pores in the adsorption layer has no contact with sodium gluconate, the probability that the edge of the pores in the adsorption layer has at least one contact with sodium gluconate, and the probability that the edge of the pores in the adsorption layer has the first contact with sodium gluconate; g(L) is the differential pore distribution function.

[0080] (2) Establishment of the equation for the ion diffusion coefficient of tricalcium silicate hydration under the influence of adsorption

[0081] According to the adsorption layer formed by the adsorption of sodium gluconate on the surface of tricalcium silicate particles, a calculation formula for the ion diffusion coefficient of tricalcium silicate hydration process based on the obstacle theory was established, as shown in the following equations 1 to 4:

[0082]

[0083] In the formula, the subscript i represents the type of ion, which are Ca 2 +, H3SiO4- and OH-; P r is the barrier coefficient; g(L) is the differential pore distribution function; L is the pore radius of the adsorption layer; dL is the microelement of the pore radius of the adsorption layer; is the number of sodium gluconate molecules per unit area of ​​the adsorption layer; r w and r SG are the radii of water molecule and sodium gluconate molecule respectively; M ads is the adsorption ratio; N A is Avogadro's constant; M w is the relative molecular mass of sodium gluconate molecule; η is the dosage of sodium gluconate; t ads is the time to reach saturated adsorption; D i , and are the diffusion coefficients of different ion types, the initial diffusion coefficients and the equilibrium diffusion coefficients respectively.

[0084] (3) Establish the complexation reaction rate equation of tricalcium silicate hydration process under the influence of complexation

[0085] The carboxyl groups of calcium gluconate react with the free calcium ions produced by the hydration of C3S in the liquid phase to form a complex. Therefore, it is assumed that some of the free calcium ions produced by the dissolution of C3S are consumed by the complex reaction, thereby reducing the concentration of free calcium ions in the solution phase and prolonging the time required to achieve supersaturation. The solubility is determined by the thermodynamic solubility product (calcium gluconate complex with a stoichiometric ratio of 1:1) and increases with increasing ionic strength. The calculation formula for the complex reaction rate based on the complex reaction kinetics is established as shown in the following equations 5 to 9:

[0086]

[0087] In the formula, v complex is the complexation reaction rate; k complex and K complex are the rate constant and equilibrium constant of the complex reaction respectively; α i , γ i , I and z i are the chemical activity of different ion types, the chemical activity coefficient of different ion types, the ionic strength and the balancing coefficient; c i is the concentration of different ion types; A is the characteristic parameter of ion activity; e0, ε r and ε0 are the basic charge number, the dielectric constant of water, and the dielectric constant of vacuum, respectively; T, F, and R are the temperature, Faraday constant, and ideal gas constant, respectively.

[0088] (4) Establish the control equation of tricalcium silicate hydration process under the influence of sodium gluconate

[0089] The multi-physics, multi-scale and multi-driving model of C3S hydration was proposed by using the Poisson-Nernst-Planck equation and solving the theory. The Nernst-Planck, Poisson and heat conduction equations were established by using the thermal-chemical-electric coupling field in the C3S hydration process. The effects of adsorption and complexation reaction were considered at the same time, and the control equations of the tricalcium silicate hydration process under the influence of sodium gluconate were established, as shown in the following equations 10 to 19:

[0090]

[0091] In the formula, is the Hamiltonian operator, and are divergence and gradient respectively; c i , t and J i They are the concentration of different types of ions, time variables and diffusion fluxes; and They are the stoichiometric constants of different types of ions in the precipitation of calcium silicate hydrate, calcium hydroxide precipitation and the complexation of calcium ions with sodium gluconate; v CSH , v CH and v complex are the C3S dissolution rate, CSH deposition rate, CH deposition rate and complex reaction rate respectively; D i , z i and γ i are the diffusion coefficient, balancing coefficient and chemical activity coefficient of different ion types respectively; ψ is the electric potential; k CSH and k CHThey are the dissolution rate constant of tricalcium silicate, the precipitation rate constant of hydrated calcium silicate and the precipitation rate constant of calcium hydroxide respectively; and are the specific surface area of ​​tricalcium silicate, the molar mass of tricalcium silicate and the surface area of ​​tricalcium silicate particles per unit volume of hydrated slurry; β CSH is the characteristic variable of the activity product; K CH and K CSH They are the supersaturation concentration of different types of ions, the equilibrium constant of calcium hydroxide and the equilibrium constant of calcium silicate hydrate; and t mix are the adsorption energy of water on the surface of tricalcium silicate particles per unit volume and the stirring time; w / c is the water-cement ratio; ρ P , C P and k P They are respectively the density of C3S hydrated slurry, the specific heat capacity of C3S hydrated slurry and the thermal conductivity of C3S hydrated slurry; and are the densities of water and tricalcium silicate, respectively; and are the specific heat capacities of water and tricalcium silicate respectively; α i is the chemical activity of different ion types; T, F and R are temperature, Faraday constant and ideal gas constant respectively; ε r and ε0 are the dielectric constants of water and vacuum, respectively.

[0092] (5) Establish the exothermic rate equation for the whole process of tricalcium silicate hydration under the influence of sodium gluconate

[0093] Considering the surface adsorption energy of the reaction between C3S particles and water and the heat released by the chemical reaction, a calculation formula for the heat release rate of the whole process of tricalcium silicate hydration under the influence of sodium gluconate was established, as shown in the following equations 20 to 26:

[0094]

[0095] In the formula, and They are the whole process heat release rate, short-range heat release rate and long-range heat release rate respectively; E ads and E a are the adsorption energy of water on the surface of tricalcium silicate particles per unit mass, the adsorption energy of water on the surface of tricalcium silicate particles per unit mole, and the activation energy of the hydration reaction of tricalcium silicate; t ads is the adsorption time; w / c is the water-cement ratio; β S , β L and τ are short-range characteristic parameter, long-range characteristic parameter and characteristic time respectively; is the specific heat capacity of tricalcium silicate; η is the dosage; is the specific surface area of ​​C3S; K complex is the complexation reaction equilibrium constant; h P and are the convective heat transfer coefficient of tricalcium silicate hydrate slurry and the heat released by complete hydration of unit mole of tricalcium silicate; Q fin , dξ and dt are the total accumulated heat, distance microelement and time microelement during the reaction time, respectively; t total and l are the total calculation time and the calculation domain length respectively; v CSH is the deposition rate of CSH.

[0096] (6) Construct a computing analyzer using the prediction model of the slow setting performance of silicate cement of the present invention, such as Figure 2 and Figure 3 As shown, the steps are as follows:

[0097] 1) Input the initial parameters, including dosage, water-cement ratio, temperature, specific surface area of ​​tricalcium silicate, average molecular radius of sodium gluconate, adsorption ratio of sodium gluconate, and stirring time;

[0098] 2) Establish the hydration control equation and hydration heat release rate equation of tricalcium silicate under the influence of sodium gluconate in the calculation module, then input the boundary conditions and initial conditions according to the actual situation of the hydration process of tricalcium silicate under the influence of sodium gluconate, and use the Newton iteration method to perform iterative calculation, with a relative tolerance of 0.01;

[0099] 3) Output the calcium ion concentration, silicate ion concentration, hydroxide ion concentration, sodium gluconate carboxyl concentration, potential, temperature, heat release rate and retarding time data of the whole process of tricalcium silicate hydration under the influence of sodium gluconate.

[0100] Example 1

[0101] The retarding performance prediction model of the present invention is used to calculate and analyze the hydration heat release rate of tricalcium silicate at different sodium gluconate dosages, and the specific steps include:

[0102] 1) The specific conditions of material characteristics and experimental environment are as follows: water-cement ratio is 0.5, C3S specific surface area is 1.6818m 2 / g, ambient temperature is 25℃;

[0103] 2) The calculation equation for the heat release rate of tricalcium silicate hydration under the influence of sodium gluconate is as follows:

[0104]

[0105]

[0106] The introduced calculation parameters are shown in Table 1.

[0107] Table 1 Calculation parameters

[0108]

[0109]

[0110] The heat release rate curve of tricalcium silicate hydration at different sodium gluconate dosages calculated by the method described in this example is shown in FIG. Figure 4 ,The error calculation of each peak time is shown in Table 2.

[0111] Table 2 Comparison of theoretical calculation results and experimental results

[0112] Sodium gluconate dosage (%) Experimental peak time (h) Calculate peak time (h) Relative error (%) 0 7.72 7.61 1.42 0.01 11.63 11.44 1.63 0.02 16.33 16.77 2.69 0.03 21.47 22.45 4.56 0.04 25.02 24.50 2.08

[0113] The results show that the analytical method of the present invention has high accuracy in determining the hydration heat release rate of tricalcium silicate at different sodium gluconate dosages.

[0114] Example 2

[0115] The prediction model of the retarding performance of the present invention is used to compare and analyze the two retarding mechanisms of sodium gluconate, namely, adsorption and complexation. ads and k complex The specific adjustment parameters of these two parameters are shown in Table 3. The calculation method is roughly the same as that of Example 1. The calculation results are shown in Figure 5 and Figure 6 .

[0116] The results showed that adsorption was the main factor for sodium gluconate to delay the hydration of tricalcium silicate.

[0117] Table 3 Adsorption and complexation parameter adjustment table

[0118] <![CDATA[Adsorption parameter (M ads )]]> <![CDATA[Complexation parameter (k complex )]]> <![CDATA[Adsorption parameter (M ads )]]> <![CDATA[Complexation parameter (k complex )]]> 10％ 10％ 10％ 10％ 50％ 10％ 10％ 100％ 100％ 10％ 10％ 200％ 150％ 10％ 10％ 300％ 10％ 100％ 50％ 10％ 50％ 100％ 50％ 100％ 100％ 100％ 50％ 200％ 150％ 100％ 50％ 300％

Claims

1. A method for constructing a prediction model for the slow setting performance of silicate cement, characterized in that: The steps include: (1) According to the adsorption and complexation reaction of sodium gluconate in the hydration process of tricalcium silicate in Portland cement, the control equation of the hydration process of tricalcium silicate under the influence of sodium gluconate was established based on the inhibition theory and complexation reaction kinetics; (2) By superimposing the heat release of water adsorption during the initial contact process of tricalcium silicate and the heat release of chemical reactions during the hydration process, a formula for calculating the heat release rate of the entire hydration process of tricalcium silicate under the influence of sodium gluconate was established. Then, based on the concentrations of various ions calculated by the control equation of the hydration process of tricalcium silicate under the influence of sodium gluconate, the heat release rate curve was calculated, and the effects of different sodium gluconate dosages on the heat release rate of tricalcium silicate hydration were analyzed. A prediction model for the retarding performance of tricalcium silicate hydration process by sodium gluconate was obtained. In step (1), the carboxyl group of sodium gluconate reacts with the free calcium ions released by the dissolution of tricalcium silicate in the liquid phase to form a complex reaction rate calculation formula based on the complex reaction kinetics: (5) In the formula, is the complexation reaction rate; and are the rate constant and equilibrium constant of the complexation reaction respectively; is the chemical activity of different ion species; The control equation for the hydration process of tricalcium silicate under the influence of sodium gluconate established in step (1) is: (10) In the formula, is the Hamiltonian operator, and are the divergence and gradient respectively; , and They are the concentration of different types of ions, time variables and diffusion fluxes; , and are the stoichiometric constants of different types of ions in the precipitation of calcium silicate hydrate, calcium hydroxide precipitation and the complexation of calcium ions with sodium gluconate; , , and They are C3S dissolution rate, CSH deposition rate, CH deposition rate and complexation reaction rate; The heat release rate calculation formula for the whole process of tricalcium silicate hydration under the influence of sodium gluconate established in step (2) is: (20) In the formula, , and They are the whole process heat release rate, short-range heat release rate and long-range heat release rate respectively.

2. The method for constructing a prediction model of the slow setting performance of tricalcium silicate hydration process by sodium gluconate according to claim 1, characterized in that: In step (1), according to the adsorption layer formed by the adsorption of sodium gluconate on the surface of tricalcium silicate particles, a calculation formula for the ion diffusion coefficient of the tricalcium silicate hydration process based on the obstacle theory is established, as shown in the following formulas 1 to 4: (1) (2) (3) (4) In the formula, the subscript i Indicates the type of ions, namely Ca 2+ 、H3SiO4 - and OH - ; is the obstruction coefficient; is the differential pore distribution function; is the pore radius of the adsorption layer; is the microelement of the pore radius of the adsorption layer; is the number of sodium gluconate molecules per unit area of ​​the adsorption layer; and are the radii of water molecule and sodium gluconate molecule respectively; is the adsorption ratio; is Avogadro's constant; is the relative molecular mass of sodium gluconate molecule; is the dosage of sodium gluconate; is the time to reach saturated adsorption; , and are the diffusion coefficients of different ion types, the initial diffusion coefficients and the equilibrium diffusion coefficients respectively.

3. The method for constructing a prediction model for slow setting performance of silicate cement according to claim 1, characterized in that: In step (1), according to the complexation reaction between the carboxyl group of sodium gluconate and the free calcium ions released by the dissolution of tricalcium silicate in the liquid phase, a calculation formula for the complexation reaction rate based on the complexation reaction kinetics is established, which also includes: (6) (7) (8) (9) In the formula, , , and They are the chemical activity of different ion types, chemical activity coefficient of different ion types, ionic strength and balancing coefficient; is the concentration of different ion species; is the characteristic parameter of ion activity; , and are the basic charge number, the dielectric constant of water, and the dielectric constant of vacuum; , and are temperature, Faraday constant and ideal gas constant respectively.

4. The method for constructing a prediction model for slow setting performance of silicate cement according to claim 1, characterized in that: The control equation for the hydration process of tricalcium silicate under the influence of sodium gluconate is established in step (1), and further includes: (11) (12) (13) (14) (15) (16) (17) (18) (19) In the formula, , and They are the diffusion coefficient, balancing coefficient and chemical activity coefficient of different ion types respectively; is the electric potential; , and They are the dissolution rate constant of tricalcium silicate, the precipitation rate constant of hydrated calcium silicate and the precipitation rate constant of calcium hydroxide respectively; , and are the specific surface area of ​​tricalcium silicate, the molar mass of tricalcium silicate and the surface area of ​​tricalcium silicate particles per unit volume of hydrated slurry, respectively; is the characteristic variable of the activity product; , and They are the supersaturation concentration of different types of ions, the equilibrium constant of calcium hydroxide and the equilibrium constant of calcium silicate hydrate; and are the adsorption energy of water on the surface of tricalcium silicate particles per unit volume and the stirring time, respectively; is the water-cement ratio; , and They are respectively the density of C3S hydrated slurry, the specific heat capacity of C3S hydrated slurry and the thermal conductivity of C3S hydrated slurry; and are the densities of water and tricalcium silicate, respectively; and are the specific heat capacities of water and tricalcium silicate, respectively; is the chemical activity of different ion species; , and are temperature, Faraday constant and ideal gas constant respectively; and are the dielectric constant of water and the dielectric constant of vacuum respectively.

5. The method for constructing a prediction model for retarding properties of silicate cement according to claim 1, characterized in that: The heat release rate calculation formula for the whole process of tricalcium silicate hydration under the influence of sodium gluconate established in step (2) also includes: (21) (22) (23) (24) (25) (26) In the formula, , and are respectively the adsorption energy of water on the surface of tricalcium silicate particles per unit mass, the adsorption energy of water on the surface of tricalcium silicate particles per unit mole, and the activation energy of the hydration reaction of tricalcium silicate; is the adsorption time; is the water-cement ratio; , and They are short-range characteristic parameters, long-range characteristic parameters and characteristic time respectively; is the specific heat capacity of tricalcium silicate; is the dosage; is the specific surface area of ​​C3S; is the equilibrium constant of the complexation reaction; and are the convective heat transfer coefficient of tricalcium silicate hydrate slurry and the heat released by complete hydration of unit mole of tricalcium silicate; , and are the total accumulated heat, distance microelement and time microelement during the reaction time respectively; and They are the total calculation time and the calculation domain length respectively; is the deposition rate of CSH.

6. A computing analyzer based on the prediction model of slow setting performance of silicate cement according to any one of claims 1 to 5, characterized in that: It includes input module, calculation module and output module; An input module, used to input the initial parameters required for the calculation of the hydration process of tricalcium silicate doped with sodium gluconate; A calculation module is used to establish a control equation for the hydration process of tricalcium silicate under the influence of sodium gluconate based on the adsorption and complex reaction effects of sodium gluconate in the hydration process of tricalcium silicate in silicate cement, based on the obstacle theory and complex reaction kinetics; a heat release rate calculation formula for the whole hydration process of tricalcium silicate under the influence of sodium gluconate is established by superimposing the heat release of water adsorption of tricalcium silicate in the initial contact process and the heat release of chemical reaction in the hydration process; then, the heat release rate curve is calculated based on the various ion concentrations calculated by the control equation, the influence of different sodium gluconate dosages on the heat release rate of tricalcium silicate hydration is analyzed, and a prediction model for the retarding performance of sodium gluconate in the hydration process of tricalcium silicate is obtained; The output module is used to output the model calculation results of the hydration process of tricalcium silicate under the influence of sodium gluconate.

7. The calculation and analysis instrument of the prediction model of slow setting performance of silicate cement according to claim 6, characterized in that: Includes the following hardware: A memory, used for storing intermediate variables and final results when calculating a prediction model of the retarding performance of tricalcium silicate hydration process by sodium gluconate; The arithmetic unit is connected to the processor and is used to realize the software functions and algorithms of the input module, the calculation module and the output module in the calculation analyzer; An input device, connected to the processor, for manually inputting measured parameter values ​​to be processed and calculated; The display is connected to the processor and is used to display the intermediate variables and final results calculated by the calculation analyzer.

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