Method for predicting actual water content of ready-mixed concrete based on low-field magnetic resonance technology

Abstract

The present application relates to the technical field of magnetic resonance testing, and particularly relates to a method for predicting actual water consumption of premixed concrete based on low-field magnetic resonance technology. The method is specifically aimed at the problem that in the prior art, it is difficult to quickly and accurately measure the actual water consumption per cubic meter of premixed concrete on the construction site, so that the quality of the concrete cannot be judged. The method for predicting actual water consumption of premixed concrete based on low-field magnetic resonance technology is provided. FID free induction decay sequence is used to perform magnetic resonance testing and analysis on calibration samples of a certain specification. By setting a very short sampling time interval, the relaxation signals of all the water contained in the freshly mixed concrete samples are completely obtained, and the water content of the calibration mortar samples and the freshly mixed concrete samples is accurately determined by fitting a sum function composed of a single exponential term and two Gaussian terms, so that the actual water consumption per cubic meter of premixed concrete can be quickly and accurately determined, and the quality of the concrete can be controlled on the construction site.

Description

Technical Field

[0001] This invention relates to the field of magnetic resonance testing technology, and more specifically to a method for predicting the actual water consumption of ready-mixed concrete using low-field magnetic resonance technology. Background Technology

[0002] With the continuous development of my country's construction industry and increasing emphasis on on-site construction environment, ready-mixed concrete has become the main material source for on-site concrete pouring. After ready-mixed concrete is transported from the mixing plant to the site, it needs to be sampled and its key performance indicators tested on-site. Workability indicators such as slump can be tested quickly and directly on-site. However, mechanical properties such as strength require curing under standard conditions for a certain period before testing. If the strength is found to be below design requirements, reinforcement, repair, or demolition and reconstruction will incur significant additional manpower, material resources, and financial costs, while also causing serious delays in construction progress and resulting in substantial economic losses. The mechanical properties, volume stability, and durability of ready-mixed concrete are closely related to its water content per cubic meter and are highly sensitive to actual water usage. In terms of mechanical properties, excessive water content per cubic meter leads to reduced concrete strength; in terms of volume stability, changes in water content per cubic meter significantly alter the early crack resistance of concrete; and in terms of durability, excessive water content per cubic meter increases concrete porosity, significantly reduces carbonation resistance and ion attack resistance, and accelerates the deterioration and damage of concrete materials and structures. In my country, the construction methods for ready-mixed concrete are relatively extensive. There is often a large discrepancy between the actual water consumption per cubic meter of ready-mixed concrete and the designed water consumption per cubic meter. From the perspective of controlling concrete quality, it is necessary to quickly and accurately detect the actual water consumption per cubic meter.

[0003] By sampling freshly mixed concrete and determining its moisture content, the actual water consumption per cubic meter can be quickly determined. Traditional methods for testing concrete moisture content are mainly divided into two categories: direct methods and indirect methods. Direct methods mainly include the drying method and the calcium carbide moisture content test method. The drying method determines the moisture content by removing internal water from the concrete and measuring the water loss mass, but the drying time is long and cannot quickly obtain the moisture content. The calcium carbide moisture content test method utilizes the property that water reacts with calcium carbide to produce acetylene, and calculates the amount of gas produced by the gas pressure increase to calculate the moisture content, but the accuracy is low. Indirect methods mainly include the resistance measurement method, the gamma-ray attenuation method, and the low-field magnetic resonance method. The resistance measurement method determines the moisture content by the relationship between the concrete resistance and the moisture content. This method is greatly affected by the type and concentration of ions in the pore water, making it difficult to accurately measure the moisture content. The gamma-ray attenuation method uses radioactive isotopes. 137 Cs and 241Moisture content is measured using am (Am) methods, which infer moisture content by testing the attenuation of gamma rays. However, this method is radioactive and has limited accuracy. Low-field magnetic resonance (LMR) testing determines moisture content by the relationship between relaxation signals and moisture content. This method is significantly affected by the iron content in the concrete, making it difficult to guarantee accuracy. Currently, CPMG sequences are commonly used in LMR testing to test the moisture content of silicate concrete. The silicate cement in concrete contains a large amount of tetracalcium aluminoferrite (TeCFA), which generates an additional magnetic field gradient near iron ions. This reduces the local magnetic field uniformity, leading to a significant increase in the transverse relaxation (spin-spin relaxation) rate. Some relaxation signals cannot be detected due to equipment limitations, resulting in a significantly lower measured moisture content.

[0004] Therefore, existing technologies have the problem that it is difficult to quickly and accurately measure the actual water consumption per cubic meter of ready-mixed concrete at the construction site, thus making it impossible to assist in the on-site evaluation of concrete quality. Summary of the Invention

[0005] To address the problem in existing technologies where it is difficult to quickly and accurately measure the actual water content per cubic meter of ready-mixed concrete at construction sites, thus hindering on-site assessment of concrete quality, this invention proposes a method for predicting the actual water content of ready-mixed concrete using low-field magnetic resonance technology. This method enables rapid and accurate determination of the actual water content of concrete at construction sites, thereby effectively assessing concrete quality. Furthermore, this method allows for rapid and accurate measurement of the water content per cubic meter of ready-mixed concrete at construction sites, facilitating effective on-site assessment of concrete quality, improving the precision of concrete quality control and on-site construction, and ultimately promoting the orderly development of the entire building materials and construction industries.

[0006] The technical solution of this application is:

[0007] 1. A method for predicting the actual water consumption of ready-mixed concrete based on low-field magnetic resonance technology, including:

[0008] S1: Pre-calibration to obtain the FID relaxation signal corresponding to a unit mass of water in the freshly mixed slurry; the specific process includes:

[0009] S1.1: Preparation of calibration sample: Prepare fresh mortar material with the same mix ratio as ready-mixed concrete but without coarse aggregate, take an appropriate amount of mortar, fill a glass bottle with a lid and seal it tightly;

[0010] S1.2: Calculate the moisture content of the calibration sample: Weigh the total mass of mortar in the calibration sample, and calculate the moisture content of the calibration sample based on the mass fraction of water in the mortar mix proportion in S1.1;

[0011] S1.3: Test and calibrate the sample; the specific process is as follows:

[0012] S1.3.1: Preheating of the low-field NMR spectrometer;

[0013] The specific process is as follows: turn on the equipment, set the target temperature of the magnet to be slightly higher than the ambient temperature, preheat for a period of time until the magnet temperature is constant;

[0014] S1.3.2: Set low-field magnetic resonance test parameters: Select the free induction decay sequence and set the corresponding test parameters;

[0015] S1.3.3: Noise relaxation signal acquisition: Using the free induction decay sequence, magnetic resonance testing is performed on an empty glass bottle to obtain the FID relaxation signal of the noise;

[0016] S1.3.4: Acquisition of relaxation signal of calibration sample: Using the free induction decay sequence, the calibration sample prepared in S1.1 is immediately subjected to magnetic resonance test to obtain the FID relaxation signal of the calibration sample;

[0017] S1.3.5: Relaxation signal analysis: Invert analysis of the FID relaxation signals collected in S1.3.3 and S1.3.4, and calculate the amount of noise and the relaxation signal at time zero of the calibration sample;

[0018] S1.4: Calculate the FID relaxation signal corresponding to a unit mass of water in freshly mixed slurry: Obtain the difference between the relaxation signal of the calibration sample and the noise at time zero using S1.3.5, divide it by the water content of the calibration sample in S1.2, and calculate the result.

[0019] S2: On-site sampling test: The specific process is as follows:

[0020] S2.1: Calculate the mass fraction p of mortar in ready-mixed concrete: Based on the design mix proportion of ready-mixed concrete, calculate by dividing the sum of the masses of all materials except aggregate by the total mass of all materials;

[0021] S2.2: Preparation of on-site test samples: Take an appropriate amount of ready-mixed concrete on-site, sieve out the stones in the ready-mixed concrete, put the remaining mortar into a glass bottle with a lid and seal it tightly, and weigh the mass of the mortar in the bottle.

[0022] S2.3: Test field sample: Place the glass bottle containing the field sample in the sample chamber of the low-field NMR spectrometer, and perform FID test analysis on the field sample through the same steps as in S1.3 to calculate the relaxation signal quantity of the field sample;

[0023] S2.4: Calculate the actual moisture content of the field sample: Based on the relaxation signal of the field sample in S2.3, and combined with the FID relaxation signal corresponding to the unit mass of water in the freshly mixed slurry obtained in S1.4, the actual moisture content m of the field sample is calculated. t ;

[0024] S3: Calculate the actual water consumption (m³) per cubic meter of concrete. c The specific process is as follows:

[0025] S3.1: Calculate the mass m of a unit cubic meter of ready-mixed concrete: Calculated by the apparent density of the ready-mixed concrete;

[0026] S3.2: Actual moisture content (m) of the field sample obtained from S2.4 t The mortar quality m obtained in S2.2 s Calculate the actual water consumption per cubic meter of concrete, m, based on the mass fraction p of mortar in ready-mixed concrete obtained in S2.1 and the mass m of ready-mixed concrete per unit cubic meter obtained in S3.1. c The calculation formula is as follows:

[0027]

[0028] The advantages of this invention are as follows: By utilizing the FID free induction decay sequence to perform magnetic resonance testing and analysis on calibration samples of a certain specification, and by setting an extremely short sampling time interval, the rapid relaxation signal that cannot be measured by the CPMG sequence is obtained, thereby completely acquiring the relaxation signal of all the water contained in the fresh concrete sample. Furthermore, by fitting a sum function composed of a single exponential term and two Gaussian terms, the water content of the calibration mortar sample and the fresh concrete sample is accurately determined. This allows for the rapid and accurate estimation of the actual water consumption per cubic meter of ready-mixed concrete, assisting in the control of concrete quality on the construction site, improving the precision of on-site concrete construction, and promoting the orderly development of the building materials industry and the construction sector. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the method for rapidly determining the actual water consumption per cubic meter of ready-mixed concrete using low-field magnetic resonance technology, as described in this invention.

[0030] Figure 2 This is a schematic diagram showing the relationship between the measured moisture content and the actual moisture content of the calibrated mortar sample in S1.3 of the present invention;

[0031] Figure 3 This is a schematic diagram illustrating the effect of fitting the relaxed signal using a sum function consisting of a single exponential term and two Gaussian terms in this invention.

[0032] Figure 4 This is a schematic diagram illustrating the effect of fitting the relaxed signal using a sum function composed of a single exponential term and a single Gaussian term, as described in this invention. Detailed Implementation

[0033] Specific implementation method one: Combining Figure 1 This implementation method is described as follows: Figure 1As shown, this embodiment addresses the engineering need for rapid and accurate testing of the actual water content per cubic meter of ready-mixed concrete at the construction site, a capability that existing technologies cannot fulfill, thus failing to assist in on-site concrete quality control. Therefore, it proposes a method for predicting the actual water content of ready-mixed concrete based on low-field magnetic resonance technology, including:

[0034] S1: Pre-calibration to obtain the FID relaxation signal quantity corresponding to the unit mass of water in the freshly mixed slurry;

[0035] S2: On-site sampling and testing to obtain the actual moisture content of the on-site samples;

[0036] S3: Calculate the actual water consumption per cubic meter of concrete on site, mc.

[0037] In the above technical solution, step S1 can be performed before on-site sampling, and steps S2 and S3 require very little time, greatly reducing the time needed to quickly determine the actual water content per cubic meter of ready-mixed concrete on-site. This allows for effective evaluation of concrete quality and improves the precision of on-site construction. The method for predicting the actual water content of ready-mixed concrete using low-field magnetic resonance technology can obtain the actual water content per cubic meter of ready-mixed concrete, avoiding rework due to quality problems caused by excessively high concrete water content, and preventing unnecessary increases in construction costs and serious delays in project progress. The concrete mainly includes cementitious materials, water, fine aggregate, coarse aggregate, and various admixtures; mortar does not contain coarse aggregate, and neat cement paste does not contain coarse or fine aggregate; cementitious materials refer to cement and fly ash, etc., as auxiliary cementitious materials.

[0038] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that step S1 involves pre-calibration to obtain the FID relaxation signal quantity corresponding to a unit mass of water in the freshly mixed slurry; the specific process includes:

[0039] S1.1: Preparation of calibration samples, the specific process is as follows:

[0040] Prepare fresh mortar with the same mix ratio as ready-mixed concrete; fill a capped glass bottle with the fresh mortar and seal it tightly to obtain a calibration sample; the fresh mortar material does not include coarse aggregate.

[0041] The capped glass bottle has an outer diameter of 50 mm and a height of 75 mm; the volume of the calibration sample in the glass bottle in S1.1 ranges from 20 to 135 mL; the water-cement ratio (W / C) in the calibration sample mix ratio ranges from [0.2:1, 0.6:1];

[0042] S1.2: Calculate the moisture content of the calibration sample. The specific process is as follows:

[0043] Weigh the calibration sample to obtain the total mass of the mortar. Based on the water-cement ratio W / C in the mix proportion of the calibration sample determined in S1.1, obtain the mass fraction of water in the mix proportion of the calibration sample. Multiply the total mass of the mortar by the mass fraction of water in the mix proportion of the calibration sample to calculate the moisture content of the calibration sample.

[0044] The formula for calculating the mass fraction of water in the calibration sample mix proportion is: Mass fraction of water = Water-cement ratio / (1 + Water-cement ratio)

[0045] S1.3: Low-field nuclear magnetic resonance spectrometer was used to test empty glass bottles and calibration samples to obtain noise and the relaxation signal of the calibration sample at time zero.

[0046] S1.4: Based on the noise obtained in S1.3 and the relaxation signal quantity of the calibration sample at time zero, calculate the FID relaxation signal quantity corresponding to a unit mass of water in the freshly mixed slurry. Other steps and parameters are the same as in Specific Implementation Method 1.

[0047] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that, in step S1.3, the calibration sample is tested to obtain the noise and the relaxation signal quantity of the calibration sample at time zero; the specific process is as follows:

[0048] Before step S1.3.1, the low-field NMR spectrometer needs to be preheated. The specific process is as follows:

[0049] Turn on the low-field NMR spectrometer, set the target magnet temperature to be higher than the ambient temperature, and preheat for a period of time until the magnet temperature is constant to complete the preheating of the low-field NMR spectrometer.

[0050] S1.3.1: Set the test parameters for the low-field NMR spectrometer. The specific process is as follows:

[0051] The low-field NMR spectrometer selects the free induction decay sequence and sets the test parameters for the free induction decay sequence;

[0052] In low-field magnetic resonance (LCR) testing, CPMG sequences are often used to determine the water content of silicate concrete. However, the presence of iron significantly affects the measurement results. The silicate cement used in concrete contains a relatively high amount of tetracalcium aluminoferrite (Tetracalcium ferroaluminate), which generates an additional magnetic field gradient near the iron ions. This reduces the local magnetic field uniformity, leading to a significant increase in the transverse relaxation (spin-spin relaxation) rate. Some relaxation signals are undetectable due to equipment limitations, resulting in a significantly lower-than-expected water content reading.

[0053] This embodiment utilizes a free induction decay sequence for testing. By using a low-field nuclear magnetic resonance spectrometer with a lower main frequency / magnetic field and setting an extremely short sampling time interval, it measures the fast relaxation signal that cannot be obtained by commonly used CPMG sequences, thereby completely obtaining the relaxation signal of all the moisture contained in the fresh concrete sample.

[0054] The Free Induction Delay (FID) sequence is a sequence used in Nuclear Magnetic Resonance (NMR) testing to measure changes in the free induction signal at different times.

[0055] In the free induction decay test, the system emits a 90-degree radio frequency pulse with a specific pulse width and energy to excite the nuclear spin from a low-energy state to a high-energy state. At this time, the macroscopic magnetization vector will rotate 90 degrees relative to the direction of the net magnetic field B0, that is, rotate to the transverse plane and maintain the initial phase. Due to the influence of spin-nuclear interaction and energy exchange leading to dephasing, the transverse component of the magnetization vector gradually decays and recovers to its initial value of 0. The FID test mainly measures the decay process of the transverse component of the magnetization vector (transverse relaxation signal) over time, thereby probing the physical environment of the hydrogen nucleus. This embodiment uses a free induction decay sequence for testing. The free induction decay signal includes two components: Gaussian decay and exponential decay. Due to the extremely short sampling time interval, the magnetic field inhomogeneity causes different relaxation rates of the relaxation signal.

[0056] S1.3.2: Acquire the FID relaxation signal of the noise. The specific process is as follows:

[0057] The low-field nuclear magnetic resonance spectrometer uses a free induction decay sequence to perform magnetic resonance testing on an empty glass bottle and obtain the FID relaxation signal of the noise.

[0058] S1.3.3: Acquire the FID relaxation signal of the calibration sample. The specific process is as follows:

[0059] The low-field nuclear magnetic resonance spectrometer uses the free induction decay sequence to perform magnetic resonance testing on the calibration sample prepared in S1.1 and obtain the FID relaxation signal of the calibration sample.

[0060] The relaxation time starts from the center moment of the 90-degree pulse. The acquisition time of the first relaxation signal is the sum of half the width of the 90-degree pulse, the acquisition delay time, and the discharge time. The difference in acquisition time between any two adjacent relaxation signals is the sampling time interval, T. 2S T is the horizontal relaxation time of the exponential term. 2F1 and T 2F2 Let be the transverse relaxation time of the two Gaussian terms.

[0061] S1.3.4: Perform inversion analysis on the noise-relaxed FID signal acquired in S1.3.2; calculate the amount of relaxed signal at the noise zero time.

[0062] Inversion analysis was performed on the FID relaxation signal of the calibration sample collected in S1.3.3 to calculate the relaxation signal quantity of the calibration sample at time zero. There are several methods for inversion analysis of the FID relaxation signal of the calibration sample collected in S1.3.3.

[0063] The process includes: 1. Fitting a sum function consisting of a single exponential term and two Gaussian terms; 2. Fitting a sum function consisting of a single exponential term and a single Gaussian term; 3. Fitting a function consisting of a single exponential term; and 4. Fitting a function consisting of a single Gaussian term. Other steps and parameters are the same as in Specific Implementation Method Two.

[0064] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One and Three in that the test parameters for the free induction decay sequence in S1.3.2 include: 90-degree pulse width (t90), number of scans, repetition time, damping time, acquisition delay time, dwell time, and number of data points, the magnetic field strength of the low-field nuclear magnetic resonance spectrometer, and the resonance frequency of the hydrogen nucleus.

[0065] In S1.3.2, the initial time for the magnetic resonance test of the empty glass bottle is set to the relaxation time starting from the center of the 90-degree pulse. The acquisition time of the first relaxation signal is the sum of half the width of the 90-degree pulse, the acquisition delay time, and the discharge time. The acquisition time difference between two adjacent relaxation signals is the sampling time interval.

[0066] In S1.3.3, the initial time for performing magnetic resonance testing on the calibration sample prepared in S1.1 is set to the relaxation time starting from the center of the 90-degree pulse. The acquisition time of the first relaxation signal is the sum of half the 90-degree pulse width time, the acquisition delay time, and the discharge time. The acquisition time difference between two adjacent relaxation signals is the sampling time interval. Other steps and parameters are the same as in Specific Implementation Method 3.

[0067] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One through Four in that...

[0068] The 90-degree pulse width is 13 μs, the number of scans ranges from [64, 8192], the waiting time ranges from [10s, 15s], the discharge time is 25 μs, the acquisition delay time is 50 μs, the sampling interval ranges from [0.5 μs, 4 μs], and the number of data points acquired ranges from [50000, 200000]. The magnetic field strength of the low-field nuclear magnetic resonance spectrometer is 0.047 T, and the resonance frequency of the hydrogen nucleus is 2 MHz. By setting an extremely short sampling time interval (e.g., dwell time ≤ 4 μs), a rapid relaxation signal that cannot be measured by commonly used CPMG sequences is obtained, thereby obtaining all the relaxation signals of the water content in the calibrated sample, making the water content measurement more accurate. Other steps and parameters are the same as in specific implementation method four.

[0069] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the specific process of inverting and analyzing the acquired FID relaxation signal in S1.3.4 is as follows:

[0070] The FID relaxation signal was inverted and analyzed by using a sum function consisting of a single exponential term and two Gaussian terms with relaxation time as the independent variable. The relaxation signal quantity at time zero was obtained by substituting t=0 into the fitting function.

[0071] The fitting function expression for the inversion analysis of the acquired FID relaxation signal is as follows:

[0072]

[0073] Where M(t) is the relaxation signal of the calibration sample or noise, M S M is the relaxation semaphore of the exponential term. F1 and M F2 These are the relaxation semaphores of the two Gaussian terms, where t is the relaxation signal acquisition time; T 2S T is the horizontal relaxation time of the exponential term. 2F1 and T 2F2 Let be the transverse relaxation time of the two Gaussian terms;

[0074] Substituting the value of 0 into the fitting function, we obtain the relaxation signal at time zero.

[0075] The Free Induction Decay (FID) sequence obtains water content information in the sample by acquiring hydrogen signals in the sample water. During the FID test, a 90-degree radio frequency pulse with a duration of t90 is first emitted, followed by a discharge time to eliminate residual radio frequency energy, and then a signal acquisition begins after a acquisition delay. Relaxation signals are acquired at regular sampling intervals until a predetermined number of relaxation data points are collected. Finally, a series of relaxation signals that decay over time are obtained. The water content of the sample is determined by analyzing these relaxation signals.

[0076] The free-induction decay signal comprises two components: one is signal attenuation caused by magnetic field inhomogeneity, exhibiting Gaussian attenuation; the other is signal attenuation caused by spin-spin interactions, exhibiting exponential attenuation. Therefore, this embodiment uses a sum function consisting of a single exponential term and two Gaussian terms for fitting. This embodiment utilizes the free-induction decay sequence to perform magnetic resonance testing on calibration samples with different water contents. The relationship between the water content of the calibration samples obtained from the fitting test in S1.3 and the actual water content is as follows: Figure 2 As shown, this embodiment uses a sum function consisting of a single exponential term and two Gaussian terms for fitting, through... Figure 3 and Figure 4 The experimental results show that the fitting effect of the sum function composed of a single exponential term and two Gaussian terms is much better than that of the sum function composed of a single exponential term and a single Gaussian term, the fitting of the single exponential term function, and the fitting of the single Gaussian term function. This effectively verifies the fitting effect of the sum function composed of a single exponential term and two Gaussian terms. Other steps and parameters are the same as in Specific Implementation Method Five.

[0077] Specific implementation method seven: Combining Figure 2 This embodiment differs from specific embodiment one or two in that step S1.4 calculates the FID relaxation signal quantity corresponding to a unit mass of water in the freshly mixed slurry based on the noise obtained in S1.3 and the relaxation signal quantity of the calibration sample at time zero. The specific process is as follows:

[0078] The relaxation signal of the calibration sample at time zero is obtained by subtracting the relaxation signal of the noise at time zero from the relaxation signal of the calibration sample at time zero using S1.3.5. Then, the difference is divided by the moisture content of the calibration sample in S1.2 to obtain the FID relaxation signal corresponding to a unit mass of water in the freshly mixed slurry. Other steps and parameters are the same as in Specific Implementation Method Five.

[0079] Specific implementation method eight: Combination Figure 3 and Figure 4 This embodiment differs from specific embodiment one or two in that the on-site sampling and testing in step S2 obtains the actual moisture content of the on-site sample; the specific process is as follows:

[0080] S2.1: Preparation of on-site test samples: The specific process is as follows:

[0081] Take ready-mixed concrete from the site, sieve out the aggregate, and put the remaining mortar into a sealed glass bottle. Weigh the bottle to obtain the mass m of the mortar in the bottle. s ;

[0082] S2.2: On-site test samples: The specific process is as follows:

[0083] The glass bottle containing the field sample was placed in the sample chamber of the low-field nuclear magnetic resonance spectrometer. The field sample was subjected to FID test analysis through the same steps as in S1.3, and the relaxation signal quantity of the field sample was calculated.

[0084] S2.3: Calculate the actual moisture content of the field samples. The specific process is as follows:

[0085] The actual moisture content m of the field sample is calculated by dividing the relaxation signal of the field sample obtained in S2.2 by the FID relaxation signal of the freshly mixed slurry per unit mass of water obtained in S1.4. t .

[0086] Before S2.1, it is also necessary to calculate the mass fraction p of mortar in a unit cubic meter of ready-mixed concrete. The specific process is as follows:

[0087] Based on the design mix proportion of ready-mixed concrete, the mass fraction p of mortar in a unit cubic meter of ready-mixed concrete is obtained by dividing the sum of the masses of all materials except for aggregate by the total mass of all materials.

[0088] The other steps and parameters are the same as in Specific Implementation Method Six.

[0089] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method One or Two in that, in S2.1, a square-hole sieve is used to remove aggregates from the ready-mixed concrete. The side length of the square holes in the square-hole sieve is 5mm.

[0090] The ready-mixed concrete in S2.1 also includes: active admixtures such as fly ash, slag, and silica fume, as well as inert admixtures such as limestone powder.

[0091] Concrete commonly incorporates active admixtures such as fly ash, slag, and silica fume, as well as inert admixtures like limestone powder. These materials typically have a high iron content. When ready-mixed concrete contains cementitious materials with a high iron content, the actual water consumption per unit cubic meter of ready-mixed concrete can be rapidly determined using a method based on low-field magnetic resonance technology. This improves the practicality of the invention. Other steps and parameters are the same as in specific embodiment eight.

[0092] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method One or Two in that the premixed concrete in S2.1 and the actual water consumption per cubic meter of concrete calculated in S3 are... c The specific process is as follows:

[0093] S3.1: Calculate the mass m of one cubic meter of ready-mixed concrete; the specific process is as follows:

[0094] Take a sample from the ready-mixed concrete; test the apparent density of the ready-mixed concrete, and multiply the apparent density of the ready-mixed concrete by 1 cubic meter to obtain the mass m of the concrete per cubic meter.

[0095] At the construction site, the apparent density of concrete is tested. Since the apparent density must include the internal pores, the volume is usually measured using the drainage method. The apparent density of the ready-mixed concrete is obtained by dividing the measured weight of the ready-mixed concrete by the measured volume of the ready-mixed concrete.

[0096] S3.2: Calculate the actual water consumption (m³) per cubic meter of concrete. c The calculation formula is as follows:

[0097]

[0098] Where, m t The actual moisture content of the field sample, m s The mortar quality is obtained, p is the mass fraction of mortar in ready-mixed concrete, and m is the mass of ready-mixed concrete per cubic meter. Other steps and parameters are the same as in specific implementation method nine.

[0099] The above description is merely of preferred embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention, and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for predicting the actual water consumption of ready-mixed concrete based on low-field magnetic resonance technology, characterized in that, include: S1: Pre-calibration to obtain the FID relaxation signal quantity corresponding to the unit mass of water in the freshly mixed slurry; The specific process includes: S1.1: Preparation of calibration samples, the specific process is as follows: Prepare fresh grout with the same mix ratio as ready-mixed concrete; fill a capped glass bottle with the fresh grout and seal it tightly to obtain a calibration sample. The capped glass bottle has an outer diameter of 50 mm and a height of 75 mm; the water-cement ratio (W / C) in the calibrated sample mix proportion is in the range of [0.2:1~0.6:1]. S1.2: Calculate the moisture content of the calibration sample. The specific process is as follows: Weigh the calibration sample to obtain the total mass of the mortar. Based on the water-cement ratio W / C in the mix proportion of the calibration sample determined in S1.1, obtain the mass fraction of water in the mix proportion of the calibration sample. Multiply the total mass of the mortar by the mass fraction of water in the mix proportion of the calibration sample to calculate the moisture content of the calibration sample. S1.3: Low-field nuclear magnetic resonance spectrometer was used to test empty glass bottles and calibration samples to obtain noise and the relaxation signal of the calibration sample at time zero. S1.4: Based on the noise obtained in S1.3 and the relaxation signal quantity of the calibration sample at time zero, calculate the FID relaxation signal quantity corresponding to a unit mass of water in the freshly mixed slurry; In step S1.3, the calibration sample is tested to obtain the noise and the relaxation signal quantity of the calibration sample at time zero; the specific process is as follows: S1.3.1: Set the test parameters for the low-field NMR spectrometer. The specific process is as follows: The low-field NMR spectrometer selects the free induction decay sequence and sets the test parameters for the free induction decay sequence; S1.3.2: Acquire the FID relaxation signal of the noise. The specific process is as follows: The low-field nuclear magnetic resonance spectrometer uses a free induction decay sequence to perform magnetic resonance testing on an empty glass bottle and obtain the FID relaxation signal of the noise. S1.3.3: Acquire the FID relaxation signal of the calibration sample. The specific process is as follows: The low-field nuclear magnetic resonance spectrometer uses the free induction decay sequence to perform magnetic resonance testing on the calibration sample prepared in S1.1 and obtain the FID relaxation signal of the calibration sample. S1.3.4: Perform inversion analysis on the FID relaxation signal of the noise collected in S1.3.2; calculate the relaxation signal quantity at time zero of noise; Inversion analysis was performed on the FID relaxation signal of the calibration sample collected in S1.3.3 to calculate the relaxation signal quantity of the calibration sample at time zero. The specific process of inverting and analyzing the FID relaxation signals of the collected calibration samples is as follows: The fitting function expression for the inversion analysis of the FID relaxation signal of the collected calibration sample is as follows: in, To calibrate the relaxation signal of the sample or noise, For the relaxation signal of the exponential term, and These are the relaxation signal quantities of the two Gaussian terms, respectively, and t is the relaxation signal acquisition time; Let be the horizontal relaxation time of the exponential term. and Let be the transverse relaxation time of the two Gaussian terms; Substituting the value of 0 into the fitting function, we obtain the relaxation signal at time zero; S2: On-site sampling and testing to obtain the actual moisture content of the on-site samples; the specific process is as follows: S2.1: Preparation of on-site test samples: Take ready-mixed concrete from the site, sieve out the aggregate, and put the remaining mortar into a sealed glass bottle. Weigh the mortar in the bottle to obtain its mass. ; S2.2: Samples tested on-site: The glass bottle containing the field sample was placed in the sample chamber of the low-field nuclear magnetic resonance spectrometer. The field sample was subjected to FID test analysis through the same steps as in S1.3, and the relaxation signal quantity of the field sample was calculated. S2.3: Calculate the actual moisture content of the field sample: The actual moisture content of the field sample is calculated by dividing the relaxation signal of the field sample obtained in S2.2 by the FID relaxation signal of the freshly mixed slurry per unit mass of water obtained in S1.

4. ; S3: Calculate the actual water consumption (m³) per cubic meter of concrete on site. c .

2. The method for predicting the actual water consumption of ready-mixed concrete based on low-field magnetic resonance technology according to claim 1, characterized in that, The test parameters for the free induction decay sequence in S1.3.1 include: 90-degree pulse width, number of scans, waiting time, discharge time, acquisition delay time, sampling time interval and number of data points acquired, magnetic field strength of the low-field nuclear magnetic resonance spectrometer, and resonance frequency of hydrogen nuclei. In S1.3.2, the initial time for the magnetic resonance test of the empty glass bottle is set to the center time of the 90-degree pulse. The acquisition time of the first relaxation signal is the sum of half the width of the 90-degree pulse, the acquisition delay time, and the discharge time. The acquisition time difference between two adjacent relaxation signals is the sampling time interval. In S1.3.3, the initial time for performing magnetic resonance testing on the calibration sample prepared in S1.1 is set to the center time of the 90-degree pulse. The acquisition time of the first relaxation signal is the sum of half the width of the 90-degree pulse, the acquisition delay time, and the discharge time. The acquisition time difference between two adjacent relaxation signals is the sampling time interval.

3. The method for predicting the actual water consumption of ready-mixed concrete based on low-field magnetic resonance technology according to claim 2, characterized in that, The 90-degree pulse width is 13 μs, the number of scans ranges from [64, 8192], the waiting time ranges from [10s, 15s], the discharge time is 25 μs, the acquisition delay time is 50 μs, the sampling interval ranges from [0.5 μs, 4 μs], and the number of data points acquired ranges from [50000, 200000]; the magnetic field strength of the low-field nuclear magnetic resonance spectrometer is 0.047 T, and the resonance frequency of the hydrogen nucleus is 2 MHz.

4. The method for predicting the actual water consumption of ready-mixed concrete based on low-field magnetic resonance technology according to claim 3, characterized in that, S1.4 calculates the FID relaxation signal quantity corresponding to a unit mass of water in the freshly mixed slurry based on the noise obtained in S1.3 and the relaxation signal quantity of the calibration sample at time zero; the specific process is as follows: Use S1.3.4 to obtain the relaxation signal of the calibration sample at time zero, subtract the relaxation signal of the noise at time zero, and then divide the difference by the water content of the calibration sample in S1.2 to obtain the FID relaxation signal corresponding to a unit mass of water in the freshly mixed slurry.

5. The method for predicting the actual water consumption of ready-mixed concrete based on low-field magnetic resonance technology according to claim 2, characterized in that, In step S2.1, a square-hole sieve is used to remove aggregate from the ready-mixed concrete. The square hole side length of the sieve is 5mm. The ready-mixed concrete in S2.1 also includes: fly ash, slag, silica fume, active admixtures, and limestone powder inert admixtures.

6. The method for predicting the actual water consumption of ready-mixed concrete based on low-field magnetic resonance technology according to claim 3, characterized in that, S3 calculates the actual water consumption per cubic meter of concrete on site. The specific process is as follows: in, The actual moisture content of the field samples, The mortar mass is denoted by p, where p is the mass fraction of mortar in the ready-mixed concrete, and m is the mass of ready-mixed concrete per cubic meter.

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