A method for determining the LC3 concrete vibrating time based on rheological parameters

Abstract

The application discloses an LC 3 concrete vibration time determination method, comprising: preparing corresponding net slurry consistent with target LC 3 concrete mortar phase, the yield stress τ and the plastic viscosity μ of the net slurry are determined at a plurality of standing time nodes, and a time evolution prediction model of the yield stress and the plastic viscosity is established based on the initial time measured value; the reference vibration time is determined through the vibration time gradient test in the initial standing state, and the ratio of the optimal vibration time at t time to the reference vibration time is defined as the vibration damping coefficient; the quantitative relationship between the vibration damping coefficient and the rheological parameter is constructed by taking the time growth ratio of the rheological parameter of the net slurry as the independent variable. In engineering application, the predicted yield stress and plastic viscosity at the current time are calculated by the evolution model, and the optimal vibration time is calculated by substituting the predicted yield stress and plastic viscosity into the quantitative relationship, so that the artificial experience judgment is got rid of, the under-vibration and over-vibration are effectively inhibited, and the real-time quantitative determination of the LC 3 concrete vibration time is realized.

Description

Technical Field

[0001] This invention belongs to the field of building materials and construction technology, specifically relating to an LC based on rheological parameters. 3 Method for determining concrete vibration time. Background Technology

[0002] LC 3 Limestone calcined clay cement concrete is a novel low-carbon cementitious material system that partially replaces silicate cement clinker with calcined clay and limestone powder. It boasts significant advantages such as low clinker consumption and low carbon emissions, making it an important direction for the green development of concrete. Because calcined clay and limestone powder partially replace clinker, the hydration and structural formation processes of its cementitious system differ from those of ordinary silicate cement. Furthermore, the rheological properties of the mixture and its development over time also differ significantly from those of ordinary concrete.

[0003] Vibration is a crucial step in ensuring the dense compaction of concrete. Essentially, it uses vibration energy to overcome the yield stress of the mixture, causing localized liquefaction and flow, and expelling internal air bubbles to achieve a uniform and dense structure. Insufficient vibration (under-vibration) leaves residual pores and defects, reducing strength and durability; excessive vibration (over-vibration) causes aggregate settling, paste floating, and segregation, similarly impairing the final quality. Theoretically, the optimal vibration time should vary depending on the rheological state of the mixture.

[0004] However, LC 3 The rheological properties of concrete present new challenges for vibration compaction. Calcined clay, with its large specific surface area and high surface activity, makes LC... 3 The mixture exhibits a significant structural reconstruction effect during the standing process; its yield stress and plastic viscosity increase rapidly with standing time, with a significantly greater increase than that of ordinary Portland cement concrete, and considerable changes can occur even within a short waiting period. Therefore, LC 3 Concrete undergoes continuous rheological changes during discharge, transportation, and waiting for pouring, resulting in a significant decrease in its vibratory compactibility. The mixture at different pouring times for the same component often exhibits distinctly different rheological states, corresponding to different optimal vibration times. For ordinary concrete, whose rheological properties change slowly over time, a fixed vibration time may be barely applicable; however, for LC concrete, whose vibratory compactibility decreases significantly over time… 3 If a fixed vibration time is used for concrete or the operator's experience is relied upon, it is very easy to cause some batches to be under-vibrated and some batches to be over-vibrated, resulting in inconsistent component forming quality.

[0005] Current concrete construction specifications rely primarily on empirical values ​​for vibration parameters and generally do not consider LC (concrete compaction). 3The dynamic evolution of concrete rheological properties with resting time; existing research also lacks information on LC. 3 Systematic research on the quantitative relationship between the rheological state of concrete and its required optimal vibration time has long resulted in a lack of scientific basis for determining the vibration time, making it impossible to adjust it in real time according to changes in the rheological state of the mixture. Therefore, there is an urgent need for a method that can adjust the vibration time based on LC... 3 A method for quantitatively determining the optimal vibration time based on the real-time rheological state of concrete is proposed to adapt to the rapid time-dependent evolution of its vibrability and achieve stable and controllable vibration quality. Summary of the Invention

[0006] The existing technology has difficulty adapting the fixed vibration time to LC. 3 The rapid evolution of concrete's vibratory compactability over time, leading to inconsistent molding quality of the same component at different pouring times, is a problem addressed by this invention. The technical problem this invention aims to solve is to provide an LC method based on rheological parameters. 3 The method for determining concrete vibration time involves applying damping compensation to the benchmark vibration time to determine the optimal vibration time.

[0007] The technical solution adopted by the present invention to solve the aforementioned technical problem is as follows: An LC based on rheological parameters 3 A method for determining concrete vibration time, comprising the following steps: S1, Preparation and Target LC 3 For a concrete mortar with consistent water-cement ratio, cementitious material composition, and admixture dosage, the yield stress and plastic viscosity of the mortar were tested at several static time points. Based on the measured values ​​at the initial static time point, a prediction model for the evolution of yield stress and plastic viscosity over time in the whole time domain was established. S2, Preparation of the target LC 3 For concrete, a vibration time gradient test was conducted under the initial static state of the mixture. The macroscopic properties of the hardened specimens were used as the evaluation index to determine the reference vibration time T for the system. base ; S3, LC at time t 3 The actual optimal vibration time T for concrete v (t) and the reference vibration time T determined by S2 base The ratio is defined as the vibration damping coefficient Ω(t) at that moment: using the time-dependent increase ratio of the cement paste rheological parameters as the independent variable, a quantitative relationship between the vibration damping coefficient Ω(t) and the rheological parameters is established: Ω(t) = K · [α·(τ(t) / τ0) + (1-α)·(μ(t) / μ0)]^β In the formula, τ(t) and μ(t) are the predicted values ​​of yield stress and plastic viscosity at time t, τ0 and μ0 are the yield stress and plastic viscosity at the initial time; τ(t) / τ0 is the time-dependent growth ratio of yield stress; μ(t) / μ0 is the time-dependent growth ratio of plastic viscosity; α is the yield stress weighting factor, with a value range of [0,1], β is the nonlinear damping evolution exponent, and α and β are the factors reflecting the LC 3 Material intrinsic constants that represent the time-dependent damping evolution of the material; K is the field system calibration constant; S4, Collection site for LC to be poured 3 The actual settling time t of the concrete is calculated using the S1 evolution prediction model, which calculates τ(t) and μ(t). These values ​​are then substituted into the aforementioned quantitative relationship to obtain the current vibration damping coefficient, which is then calculated according to T. v (t) = T base × Ω(t) is used to determine the optimal vibration time for the current batch, and the optimal vibration time for the current batch is used to guide the on-site vibration operation.

[0008] Compared with the prior art, the present invention has the following beneficial effects: The formulation and target LC of this invention 3 For the corresponding neat cement paste with the same concrete mortar consistency, the yield stress τ and plastic viscosity μ were measured at several static time points. Based on the measured values ​​at the initial moment, a predictive model for the time-dependent evolution of yield stress and plastic viscosity was established. The reference vibration time T was determined through vibration time gradient tests under the initial static state. base And the optimal vibration time T at time t. v (t) and T base The ratio is defined as the vibration damping coefficient Ω(t), and Ω(t) is constructed using the time-dependent growth ratio of the neat cement paste rheological parameters as the independent variable: Ω(t) = K·[α·(τ(t) / τ0)+(1-α)·(μ(t) / μ0)]^β. In engineering applications, only the actual settling time t of the concrete to be poured needs to be measured on-site. The τ(t) and μ(t) calculated from the evolution model are then substituted into the above formula, and the result can be calculated according to T. v (t)=T base ×Ω(t) directly calculates the optimal vibration time that matches the current rheological state, eliminating the need for manual judgment and effectively suppressing under-vibration and over-vibration, thus achieving LC. 3 Real-time quantitative determination of concrete vibration time.

[0009] This invention determines LC through experiments. 3The time-dependent rheological development model of slurry yield stress and plastic viscosity replaces the highly discrete and cumbersome concrete rheological test with the slurry rheological test, which can quantitatively predict the rheological state at any static time. Moreover, the model characterizes the rheological development by the time-dependent growth ratio of the rheological parameters relative to the measured values ​​at the initial time (i.e., τ(t) / τ0, μ(t) / μ0). This growth ratio is a dimensionless relative quantity, so it is only necessary to grasp its time-dependent development trend without relying on absolute values. The test is simple and has good repeatability, providing a reliable input for the quantitative calculation of vibration time.

[0010] Based on this, the present invention proposes a formula for the vibration damping coefficient, decomposing the optimal vibration time into the product of the baseline vibration time and the vibration damping coefficient. This coefficient is constructed using the time-dependent development trend of the neat cement paste rheological parameters as the independent variable, enabling the vibration time to adaptively increase with the time-dependent deterioration of the rheological state. This achieves mechanistic control of LC... 3 Precise compensation for the decrease in the vibratory resilience of concrete over time. At the same time, the formula separates the intrinsic time-dependent damping evolution of the material from the systematic differences in field equipment and operations. Material parameters can be universally applied across construction sites after a single calibration in the laboratory, requiring only single-point calibration on site, resulting in low calibration costs and high promotion efficiency.

[0011] Using this method, the construction site only needs to measure the LC of the material to be poured. 3 The actual settling time of concrete can be directly calculated using the rheological development model and the vibration damping coefficient formula to determine the optimal vibration time that matches its current rheological state. This eliminates the reliance on manual experience and judgment, effectively suppressing both under-vibration and over-vibration, thereby consistently achieving a dense, uniform, and consistent satisfactory vibration effect, significantly improving the performance of concrete compaction (LC). 3 Quality stability and operability of concrete vibration construction. Attached Figure Description

[0012] Figure 1 This invention is based on rheological parameters for LC. 3 A flowchart illustrating the method for determining concrete vibration time.

[0013] Figure 2 The curve showing the change in compressive strength of L-150 mix ratio with vibration time after 28 days under static condition at 0 min in this embodiment of the invention.

[0014] Figure 3 The curve showing the change of macroscopic harmful porosity with vibration time for L-150 mix ratio under 0 min static condition in this embodiment of the invention. Detailed Implementation

[0015] The present invention will be further described below with reference to embodiments, but these are not intended to limit the scope of protection of this application.

[0016] Currently, concrete vibration compaction still relies heavily on manual experience, with operators judging the start, end, and duration of vibration visually, lacking quantitative data. For ordinary concrete, whose rheological properties change slowly over time, this crude method is barely applicable; however, for LC... 3 The rheological properties of concrete differ significantly from those of LC. Its yield stress and plastic viscosity increase rapidly with resting time, while its vibrability decreases significantly over time. The vibration effect is highly sensitive to changes in the rheological state; relying on fixed durations or empirical judgments easily leads to under-vibration or over-vibration, thus affecting the molding quality. Therefore, this invention creatively addresses this issue... 3 Research on vibration control of concrete was conducted based on its rheological properties, and a method for determining vibration time driven quantitatively by the rheological state was established. The specific steps include: S1, Preparation and Target LC 3 For a concrete mortar with consistent water-cement ratio, cementitious material composition, and admixture dosage, the yield stress and plastic viscosity of the mortar were tested at several static time points. Based on the measured values ​​at the initial static time point, a prediction model for the evolution of yield stress and plastic viscosity over time in the whole time domain was established by nonlinear regression. S2, Preparation of the target LC 3 For concrete, a vibration time gradient test was conducted under the initial static state of the mixture. The macroscopic properties of the hardened specimens were used as the evaluation index to determine the reference vibration time T for the system. base ; S3, LC at time t 3 The actual optimal vibration time T for concrete v (t) and the reference vibration time T determined by S2 base The ratio is defined as the vibration damping coefficient Ω(t) at that moment: Ω(t) = T v (t) / T base The damping coefficient characterizes LC 3 The increase in vibration time required due to the deterioration of concrete rheological properties over time, relative to the initial reference state; and then, using the time-dependent increase ratio of the neat cement paste rheological parameters as independent variables, a quantitative relationship is established between the vibration damping coefficient Ω(t) and the rheological parameters (yield stress and plastic viscosity): Ω(t) = K · [α·(τ(t) / τ0) + (1-α)·(μ(t) / μ0)]^β In the formula, τ(t) and μ(t) are the predicted values ​​of yield stress and plastic viscosity at time t, and τ0 and μ0 are the benchmark test values ​​at the initial time; α is the yield stress weighting factor, with a value range of [0,1], reflecting the relative contribution of yield stress and plastic viscosity to vibration damping; β is the nonlinear damping evolution index, reflecting the nonlinear amplification effect of vibration damping as the rheological state deteriorates; α and β reflect the LC 3 The intrinsic constants of the material, which determine the time-dependent damping evolution, are fixed after calibration through vibration molding experiments at different non-zero static time points under standard test conditions (where K is defined as 1.0). For the same LC... 3 The material system is universal across construction sites; K is the on-site system calibration constant, reflecting the systematic differences between on-site vibration equipment and operating conditions and standard test conditions, and is determined through on-site single-point vibration molding experiments.

[0017] S4, Collection site for LC to be poured 3 The actual settling time t of the concrete is calculated using τ(t) and μ(t) from the S1 evolution prediction model. Substituting these values ​​into Ω(t) yields the current damping coefficient. The optimal vibration time for the current batch is then calculated using the following formula, which guides the on-site vibration operation: T v (t) = T base × Ω(t).

[0018] Furthermore, the resting time nodes mentioned in S1 are set to, for example, 0 min, 15 min, 30 min, 45 min, and 60 min; the yield stress evolution prediction model over time is as follows: τ(t) = τ0 · exp(a·t^b) The time-dependent evolution prediction model for plastic viscosity is as follows: μ(t) = μ0 · (1 + c·t^d) Wherein, τ0 and μ0 are the initial yield stress and initial plastic viscosity measured at 0 min; a, b, c, and d are time-varying characteristic constants, which are determined by nonlinear fitting of the measured data at each static time node using the least squares method with τ0 and μ0 as the reference values.

[0019] Furthermore, in S2, the LC in the 0-minute static state... 3 The concrete mixture was poured into standard molds and subjected to vibration time gradients of 5s, 10s, 15s, 20s, 25s, 30s, 35s, and 40s, respectively. After standard curing for 28 days, the compressive strength and internal macroscopic harmful porosity of each specimen were measured. The shortest vibration time corresponding to the inflection point where the compressive strength curve reaches a plateau and the macroscopic harmful porosity reaches a minimum was taken as the baseline vibration time T for this mix design. baseThis is the 28-day compressive strength-macroscopic harmful porosity criterion.

[0020] Furthermore, the reference vibration time T base Alternatively, a rapid criterion can be used: measure the apparent density of the mixture after different vibration times, and take the shortest vibration time corresponding to the peak plateau of apparent density as the actual optimal vibration time; or replace the rapid apparent density criterion with the air content criterion of fresh concrete, and take the shortest vibration time corresponding to the minimum air content plateau. During the laboratory calibration stage, the results obtained from the rapid criterion and the 28-day macroscopic performance criterion can be measured simultaneously to verify the T values ​​determined by both. base Once the criteria are met, T can be directly determined using a fast criterion in practical applications. base Based on this, α and β are calibrated, and then the on-site system calibration constant K is calibrated based on the calibrated α and β. Since there is no need to wait for the 28-day aging period, the above calibration work can be completed on the day the on-site work begins.

[0021] Furthermore, the calibration method for the material intrinsic constants α and β in S3 is as follows: select two non-zero static time nodes t1 and t2, neither of which is 0 min, and conduct vibration compaction experiments according to the same method as in S2, and measure the corresponding actual optimal vibration time T. v (t1) and T v (t2), from which we obtain two sets of actual vibration damping coefficients Ω(t1)=T v (t1) / T base Ω(t2)=T v (t2) / T base Together with the time-dependent growth ratios τ(t1) / τ0, μ(t1) / μ0, τ(t2) / τ0, and μ(t2) / μ0 of the corresponding rheological parameters given by the S1 evolution prediction model, substituting them into the following system of equations, we can numerically solve for α and β under the constraint α∈[0,1]: Ω(t1) = [α·(τ(t1) / τ0) + (1-α)·(μ(t1) / μ0)]^β Ω(t2) = [α·(τ(t2) / τ0) + (1-α)·(μ(t2) / μ0)]^β α and β are intrinsic constants of the material, which are fixed after being calibrated once under standard test conditions. For the same LC... 3 The material system is universal across construction sites and does not require repeated calibration.

[0022] Furthermore, as a preferred calibration method for α and β, vibration molding experiments are conducted at no less than three non-zero static time nodes. Under the constraint of α∈[0,1], the least squares method is used to perform nonlinear fitting between the actual vibration damping coefficient and the corresponding rheological growth ratio of each node to determine α and β, so as to improve the calibration robustness.

[0023] Furthermore, the calibration method for the field system calibration constant K in S3 is as follows: LC data are collected during the initial static time (t min) at the start of field construction. 3 For the concrete mixture, determine the actual optimal vibration time T under the given site conditions. v (t), solve for it using the following formula: K = (T v (t) / T base ) / [α·(τ(t) / τ0) + (1-α)·(μ(t) / μ0)]^β In the formula, τ(t) and μ(t) are the predicted values ​​of yield stress and plastic viscosity given by the S1 prediction model at tmin; K reflects the systematic differences between the on-site vibration equipment, operating conditions and standard test conditions, and is calibrated once for each construction site and then used for a fixed purpose.

[0024] Furthermore, after determining α, β, and K, a non-zero resting time node that was not involved in the calibration is selected as the verification node, according to T. v (t)=T base The predicted optimal vibration time of the verification node is calculated by ×Ω(t), and compared with the actual optimal vibration time measured at the node. When the deviation between the two is within the preset tolerance range, it is confirmed that the established quantitative relationship between the vibration damping coefficient and the rheological parameters is effective within the applicable resting time range.

[0025] Furthermore, in S4, the actual on-site settling time t to which this method applies does not exceed the LC. 3 Initial setting time of concrete system; when according to T v (t)=T base The optimal vibration time calculated by ×Ω(t) reaches the preset upper limit of vibration time T. max When, take T v (t)=T max This is to prevent segregation caused by excessive vibration.

[0026] Example 1: LC 3 Determination of rheological parameters of concrete paste and establishment of a time-dependent evolution prediction model In this embodiment, following step S1, LC is used with three flowability grades (slump 80mm, 150mm, and 220mm). 3 Using concrete paste as the research object, the yield stress τ (Pa) and plastic viscosity μ (mPa·s) were measured at five static time points: 0 min, 15 min, 30 min, 45 min, and 60 min. The results are shown in Table 1.

[0027] Table 1. Results of Rheological Parameter Measurement for Different Mixture Proportions of Neat Paste

[0028] Based on the measured values ​​τ0 and μ0 at the initial settling time point (0 min), the values ​​of each LC were analyzed. 3 Nonlinear regression fitting was performed on the rheological data to establish the following time-dependent evolution prediction model: Predictive model for the evolution of yield stress over time: τ(t) = τ0 · exp(a·t^b) Predictive model for the evolution of plastic viscosity over time: μ(t) = μ0 · (1 + c·t^d) The time-varying characteristic constants obtained from fitting each ratio are shown in Table 2. The yield stress model R 2 All are not less than 0.92, plastic viscosity model R 2 All values ​​are no less than 0.9, indicating a good fit.

[0029] Table 2 Fitting results of the time-dependent evolution model of rheological parameters

[0030] In engineering applications, τ0 and μ0 are measured immediately after mixing. By substituting them into the above-mentioned time-dependent evolution prediction model, τ(t) and μ(t) at any resting time t can be predicted without repeating the test at subsequent times.

[0031] Example 2: Reference vibration time T base Calibration and determination of material intrinsic constants α and β This embodiment uses an LC with a slump of 150mm. 3 Using concrete (L-150) as the object, follow steps S2 and S3 to complete the benchmark vibration time T. base The calibration and determination of the material's intrinsic constants α and β.

[0032] 1. Reference vibration time T base Calibration (S2) Take the L-150 mixture that has been left to stand for 0 minutes, and fill it into a standard cylindrical specimen (Φ150 mm × 300 mm). Apply vibration for 5s, 10s, 15s, 20s, 25s, 30s, 35s, and 40s respectively to form the specimen. Make 3 parallel specimens in each group. Cure the specimens according to standard for 28 days and measure the compressive strength and internal porosity of each specimen.

[0033] Depend on Figure 3It can be seen that: the compressive strength increased from 27.67 MPa at 5s to 35.17 MPa at T=15s, and remained basically flat within the range of 35~37 MPa from 15s to 40s, indicating that the compressive strength had entered a plateau period at T=15s; the porosity decreased from 2.07% at 5s to 0.82% at T=15s, and showed no significant decreasing trend with the extension of vibration time after 15s, indicating that the porosity had reached a minimum inflection point at T=15s. This process is the 28-day strength-porosity criterion. The two criteria are consistent. T base = 15s.

[0034] Simultaneously, a rapid criterion (apparent density method) was used for verification: the apparent density also reached a peak plateau at T=15s, which is consistent with the conclusion obtained from the 28-day strength-porosity criterion, indicating that the rapid criterion can be equivalently replaced by the age criterion for determining the optimal vibration time in this system.

[0035] 2. Determination of intrinsic material constants α and β (S3) Selecting t1=15min and t2=45min as two non-zero settling time nodes, vibration compaction experiments were conducted using the same method as S2 (rapid criterion), and the corresponding actual optimal vibration time T was measured. v (t1) and T v (t2), from which two sets of actual vibration damping coefficients are obtained: Ω(t1) = T v (t1) / T base = 30s / 15s = 2.00 Ω(t2) = T v (t2) / T base = 50s / 15s = 3.33 Based on the evolution prediction model established in Example 1, the time-dependent growth ratio of rheological parameters at t1=15min and t2=45min was calculated: τ(15) / τ0 = exp(0.2619×15^0.4581) = exp(0.9053) = 2.4726 μ(15) / μ0 = 1+0.0856×15^0.7146 = 1+0.5931 = 1.5931 τ(45) / τ0 = exp(0.2619×45^0.4581) = exp(1.4974) = 4.4700 μ(45) / μ0 = 1+0.0856×45^0.7146 = 1+1.3004 = 2.3004 Under standard test conditions, let K=1.0, substitute the above values ​​into the following system of equations, and solve the numerical system simultaneously under the constraint α∈[0,1]: Ω(t1) = [α·(τ(t1) / τ0) + (1-α)·(μ(t1) / μ0)]^β → 2.00 = [α·2.4726 +(1-α)·1.5931]^β Ω(t2) = [α·(τ(t2) / τ0) + (1-α)·(μ(t2) / μ0)]^β → 3.33 = [α·4.4700 +(1-α)·2.3004]^β Numerical solution yields: α = 0.3771, β = 1.0585 Cross-match verification To verify the applicability of the material intrinsic constants α=0.3771 and β=1.0585 determined by L-150 to other mix proportions, a cross-mix proportion verification experiment was conducted using the L-80 mix proportion (slump 80mm).

[0036] The L-80 rheological evolution model (τ0=80.38Pa, a=0.1649, b=0.5627; μ0=4732.1mPa·s, c=0.1203, d=0.3202) and its own separately calibrated reference vibration time T according to the S2 method were used. base Based on a time of 20 seconds, substituting α=0.3771 and β=1.0585, the optimal vibration time for a settling period of t=45 minutes is calculated: τ(45) / τ0 = exp(0.1649×45^0.5627) = exp(0.1649×8.517) = 4.073 μ(45) / μ0 = 1+0.1203×45^0.3202 = 1+0.1203×3.370 = 1.405 Ω(45) = [0.3771×4.073 + 0.6229×1.405]^1.0585 = [1.536+0.875]^1.0585 = 2.411^1.0585 = 2.54 T v (45) = T base × Ω(45) = 20 × 2.54 ≈ 50s Three parallel molding experiments were conducted, with three parallel specimens in each group. After standard curing for 28 days, the compressive strength and macroscopic harmful porosity were measured. The results are shown in Table 3. Table 3. Results of molding quality verification across mix proportions

[0037] As shown in Table 3, after standing for 45 minutes, Group B, still molded for 20 seconds, showed a 18.0% decrease in compressive strength compared to Group A, and an increase in macroscopic harmful porosity from 2.1% to 7.4%, indicating a significant deterioration in molding quality. Group C, according to the T predicted by this method... v (45) After molding for 50 seconds, the compressive strength increased by 14.2% compared to Group B, and the porosity decreased from 7.4% to 4.2%, indicating a significant improvement in molding quality. Although there was still a certain gap compared to the benchmark of Group A (strength difference of 6.3%), this was due to the irreversible structuralization during the static setting of concrete, which is a normal phenomenon. The above results show that this method can effectively compensate for LC. 3 The vibrational properties of the concrete deteriorated after standing, and the values ​​of α=0.3771 and β=1.0585, which were calibrated by the L-150 mix design, were successfully transferred to the L-80 mix design, verifying the applicability of the material's intrinsic constants across mix designs.

[0038] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. An LC based on rheological parameters 3 The method for determining concrete vibration time is characterized by, The method includes the following steps: S1, Preparation and Target LC 3 For a concrete mortar with consistent water-cement ratio, cementitious material composition, and admixture dosage, the yield stress and plastic viscosity of the mortar were tested at several static time points. Based on the measured values ​​at the initial static time point, a prediction model for the evolution of yield stress and plastic viscosity over time in the whole time domain was established. S2, Preparation of the target LC 3 For concrete, a vibration time gradient test was conducted under the initial static state of the mixture. The macroscopic properties of the hardened specimens were used as the evaluation index to determine the reference vibration time T for the system. base ; S3, LC at time t 3 The actual optimal vibration time T for concrete v (t) and the reference vibration time T determined by S2 base The ratio is defined as the vibration damping coefficient Ω(t) at that moment: using the time-dependent increase ratio of the cement paste rheological parameters as the independent variable, a quantitative relationship between the vibration damping coefficient Ω(t) and the rheological parameters is established: Ω(t) = K · [α·(τ(t) / τ0) + (1-α)·(μ(t) / μ0)]^β, In the formula, τ(t) and μ(t) are the predicted values ​​of yield stress and plastic viscosity at time t, τ0 and μ0 are the yield stress and plastic viscosity at the initial time; τ(t) / τ0 is the time-dependent growth ratio of yield stress; μ(t) / μ0 is the time-dependent growth ratio of plastic viscosity; α is the yield stress weighting factor, with a value range of [0,1], β is the nonlinear damping evolution exponent, and α and β are the factors reflecting the LC 3 Material intrinsic constants that represent the time-dependent damping evolution of the material; K is the field system calibration constant; S4, Collection site for LC to be poured 3 The actual settling time t of the concrete is calculated using the S1 evolution prediction model, which calculates τ(t) and μ(t). These values ​​are then substituted into the aforementioned quantitative relationship to obtain the current vibration damping coefficient, which is then calculated according to T. v (t) = T base × Ω(t) is used to determine the optimal vibration time for the current batch, and the optimal vibration time for the current batch is used to guide the on-site vibration operation.

2. The method according to claim 1, characterized in that, In S1, the settling time nodes are set to 0 min, 15 min, 30 min, 45 min, and 60 min; the yield stress evolution prediction model over time is: τ(t) = τ0 · exp(a·t^b), The time-dependent evolution prediction model for plastic viscosity is as follows: μ(t) = μ0 · (1 + c·t^d), Where τ0 and μ0 are the measured initial yield stress and initial plastic viscosity at 0 min; a, b, c, and d are time-varying characteristic constants; t is time; using τ0 and μ0 as reference values, the measured data at each static time node are nonlinearly fitted using the least squares method.

3. The method according to claim 1, characterized in that, In S2, the LC in the 0min static state is... 3 The concrete mixture was poured into standard molds and subjected to vibration time gradients of 5s, 10s, 15s, 20s, 25s, 30s, 35s, and 40s, respectively. After standard curing for 28 days, the compressive strength and internal macroscopic harmful porosity of each specimen were measured. The shortest vibration time corresponding to the inflection point where the compressive strength curve reaches a plateau and the macroscopic harmful porosity reaches a minimum was taken as the baseline vibration time T for this mix design. base This is the 28-day compressive strength-macroscopic harmful porosity criterion.

4. The method according to claim 3, characterized in that, The benchmark vibration time can also be determined by a rapid criterion: measure the apparent density of the mixture after being vibrated for different times, and take the shortest vibration time corresponding to the peak plateau of the apparent density as the actual optimal vibration time; or measure the air content of the fresh concrete, and take the shortest vibration time corresponding to the minimum plateau of the air content. During the laboratory calibration phase, the results obtained from the rapid criterion and the 28-day compressive strength-macroscopic harmful porosity criterion can be simultaneously measured to verify the T values ​​determined by both. base Once the match is found, in actual use, a quick criterion is directly used to determine T. base Based on this, α and β are calibrated, and then the field system calibration constant K is calibrated based on the calibrated α and β.

5. The method according to claim 4, characterized in that, The calibration process for the intrinsic constants α and β of the material in S3 is as follows: Select two non-zero static time nodes t1 and t2, both of which are not 0 min, and conduct vibration compaction experiments in the same manner as in S2, and measure the corresponding actual optimal vibration time T. v (t1) and T v (t2), from which we obtain two sets of actual vibration damping coefficients Ω(t1)=T v (t1) / T base Ω(t2)=T v (t2) / T base Together with the time-dependent growth ratios τ(t1) / τ0, μ(t1) / μ0, τ(t2) / τ0, and μ(t2) / μ0 of the corresponding rheological parameters given by the S1 evolution prediction model, substituting them into the following system of equations, we can numerically solve for α and β under the constraint α∈[0,1]: Ω(t1) = [α·(τ(t1) / τ0) + (1-α)·(μ(t1) / μ0)]^β, Ω(t2) = [α·(τ(t2) / τ0) + (1-α)·(μ(t2) / μ0)]^β.

6. The method according to claim 5, characterized in that, The calibration process for the intrinsic constants α and β of the material in S3 is as follows: select no less than three non-zero static time nodes to conduct vibration molding experiments, and use the least squares method to perform nonlinear fitting of the actual vibration damping coefficient and the time growth ratio of the corresponding rheological parameters of each node under the constraint of α∈[0,1], to determine α and β.

7. The method according to claim 5, characterized in that, The calibration process for the field system calibration constant K in S3 is as follows: LC data are collected during the initial settling time (t min) at the start of field construction. 3 For the concrete mixture, determine the actual optimal vibration time T under the given site conditions. v (t), solve for it using the following formula: K = (T v (t) / T base ) / [α·(τ(t) / τ0) + (1-α)·(μ(t) / μ0)]^β, In the formula, τ(t) and μ(t) are the predicted values ​​of yield stress and plastic viscosity given by the S1 prediction model at tmin; K reflects the systematic differences between the on-site vibration equipment, operating conditions and standard test conditions, and is calibrated once for each construction site and then used for a fixed purpose.

8. The method according to claim 5, characterized in that, After determining α, β, and K, select a non-zero resting time node that was not involved in the calibration as the verification node, and proceed according to T. v (t)=T base The predicted optimal vibration time of the verification node is calculated by ×Ω(t), and compared with the actual optimal vibration time measured at the node. When the deviation between the two is within the preset tolerance range, it is confirmed that the established quantitative relationship between the vibration damping coefficient and the rheological parameters is effective within the applicable resting time range.

9. The method according to claim 1, characterized in that, In S4, the actual settling time t on site does not exceed the LC. 3 Initial setting time of concrete system; when according to T v (t)=T base The optimal vibration time calculated by ×Ω(t) reaches the preset upper limit of vibration time T. max When, take T v (t)=T max This is to prevent segregation caused by excessive vibration.

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