Mortar working performance prediction method based on wet measurement method and compressible stacking model

Abstract

The invention relates to the technical field of buildings, in particular to a mortar working performance prediction method based on a wet measurement method and a compressible stacking model, which comprises the following steps: preparing raw materials for preparing mortar; determining the working performance of the designed mortar; measuring the particle sizes and volume fractions of the cement and the fly ash through a laser particle size analyzer; adopting a wet test method to test to obtain the actual stacking compactness of each graded material, and inversely calculating the residual stacking compactness; according to the residual stacking compactness, the actual stacking compactness of the mixture is obtained by applying a compressible stacking model; according to a result output by the compressible stacking model, calculating the film thickness of the mortar by applying a film thickness theory, and realizing prediction of the working performance of the mortar; the mix proportion calculated by the method has high working performance, can reflect the influence of different water reducing agent dosages on the working performance of mortar, and can provide a certain scientific basis for later research on the working performance of concrete based on a film thickness theory.

Description

Technical Field

[0001] The present invention relates to the field of construction technology, and particularly to a method for predicting the workability of mortar based on the wet measurement method and the compressible packing model. Background Art

[0002] As an important component of concrete, the performance of mortar directly affects the workability and mechanical performance of concrete. In recent years, with the rapid development of complex engineering structures such as high dams, super high-rise buildings, and long-span bridges, comprehensive performance requirements such as high strength, high fluidity, and low shrinkage have been put forward for concrete materials. Among them, workability, as the core index of concrete construction quality, is directly related to key technological links such as pumping efficiency and dense forming.

[0003] Research shows that the incorporation of water reducing agents can significantly improve the rheological properties of concrete and enhance the strength by reducing the water-cement ratio. However, most of the existing workability prediction models are constructed based on traditional parameters such as aggregate gradation and water-binder ratio, ignoring the non-linear effect of the dosage of water reducing agents on the rheological behavior of the paste. Experimental data shows that when the dosage of polycarboxylate water reducing agent exceeds the critical value, the viscosity of mortar will show a sudden change characteristic, and it is difficult for traditional empirical formulas to capture this dose-response relationship. This disconnection between the theoretical model and engineering practice leads to a situation where the actual slump deviates from the predicted value by more than 20% in the design of concrete mix proportions, seriously restricting the precise preparation of high-performance concrete. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for predicting the workability of mortar based on the wet measurement method and the compressible packing model, which can reflect the influence of different dosages of water reducing agents on the workability of mortar.

[0005] To achieve the above purpose, the present invention provides a method for predicting the workability of mortar based on the wet measurement method and the compressible packing model, including:

[0006] Preparing raw materials for preparing mortar;

[0007] Determining the designed workability of mortar;

[0008] Measuring the particle size and volume fraction of cement and fly ash through a laser particle size analyzer;

[0009] Using the wet measurement method to test and obtain the actual packing density of each gradation material, and back-calculating the remaining packing density;

[0010] According to the remaining packing density, using the compressible packing model to obtain the actual packing density of the mixture;

[0011] According to the result output by the compressible packing model, using the film thickness theory to calculate the film thickness of the mortar, so as to realize the prediction of the workability of the mortar.

[0012] Among them, the raw materials of the mortar include water, cement, water reducer, and river sand.

[0013] Among them, the specific steps for back-calculating the remaining bulk density by using the wet measurement method to test the actual bulk density of various graded materials include:

[0014] Determine the water-solid ratio, and prepare water, cement, water reducer, and river sand under this ratio;

[0015] Add river sand to the mixing pot and then add water;

[0016] Add half of the cement and water reducer to the mixing pot and stir for 3 minutes, then divide the remaining cement and water reducer into four equal parts and add them to the mixing pot in sequence and stir for 3 minutes;

[0017] After mixing is completed, fill the mortar into a 300 ml beaker, place it on a vibrating table for vibration, use a spatula to remove the excess part, and weigh the mass of the slurry in the beaker;

[0018] Reduce the water-solid ratio and repeat the above steps until the maximum solid concentration is obtained.

[0019] Among them, the operation process of the compressible packing model includes:

[0020] Determine the parameters of each material;

[0021] Calculate the initial remaining bulk density;

[0022] Add water reducer, and calculate the remaining bulk density and volume fraction after compounding;

[0023] Calculate the loosening effect and the coefficient of wall adhesion effect;

[0024] Calculate the virtual bulk density according to the initial remaining bulk density and the remaining bulk density after compounding;

[0025] Output the actual bulk density of the mixture;

[0026] Use the film thickness theory to calculate the water film thickness and the net paste film to predict the workability of the mortar.

[0027] A method for predicting the workability of mortar based on the wet measurement method and the compressible packing model. First, the remaining packing density of each material is obtained through the wet measurement method experiment. Then, the actual packing density of the paste is determined according to the compressible packing model. Next, the thickness of the paste film is calculated based on the film thickness theory to predict the workability of the mortar. Finally, the final mix ratio is obtained through the water-cement ratio and the mortar aggregate ratio. The present invention calculates the influence of the water reducer on the workability of the mortar based on the wet measurement method - compressible packing model - film thickness theory. Therefore, the mix ratio calculated by the method of the present invention has high workability and can reflect the influence of different water reducer dosages on the workability of the mortar. By making full use of the existing data, the requirement for the experience of the experimenters is reduced, the number of experiments is greatly reduced, and at the same time, it can provide a certain scientific basis for the future research on the workability of concrete based on the film thickness theory. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 It is a schematic diagram of the loosening effect and the wall attachment effect of the present invention.

[0030] Figure 2 It is a flowchart of the method for predicting the workability of mortar based on the wet measurement method and the compressible packing model of the present invention.

[0031] Figure 3 It is a flowchart of obtaining the remaining packing density of the paste through the wet measurement method experiment of the present invention.

[0032] Figure 4 It is a flowchart of the operation of the compressible packing model of the present invention.

[0033] Figure 5 It is a schematic diagram of the water reducer content with different mix ratios of the present invention.

[0034] Figure 6 It is a calculation example diagram of the present invention.

[0035] Figure 7 It is a table of the values of K under different packing methods of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0037] Please refer to Figures 1 to 7 , the present invention provides a method for predicting the working performance of mortar based on the wet measurement method and the compressible packing model, including:

[0038] S1 Prepare the raw materials for preparing mortar;

[0039] Prepare water, cement, water reducer, and sand for preparing mortar. When specifically preparing the above materials, it can be prepared according to the standards of the "Code for Design of Mix Proportions of Masonry Mortar" (JGJT98-2019). For the powder-sand ratio (volume ratio of powder to sand) C / A = 0.75, carry out cement mortar experiments with water reducers of 0, 0.1%, 0.2%, 0.3%, and 0.4%. For C / A = 0.85, carry out cement mortar tests with water reducers of 0, 0.1%, 0.2%, and 0.3%, as Figure 5 shown.

[0040] S2 Determine the designed working performance of the mortar;

[0041] S3 Determine the particle sizes and volume fractions of cement and fine sand particles through a laser particle size analyzer;

[0042] S4 Use the wet measurement method to test and obtain the actual packing density of the slurry of each gradation material;

[0043] The specific steps include:

[0044] S41 Determine the water-solid ratio, and prepare water, cement, water reducer, and river sand at this ratio;

[0045] Determine the water-solid ratio, start the test from a larger water-solid ratio, respectively weigh the masses of water, cement, water reducer, and river sand at this ratio, and pack them in containers.

[0046] S42 Add river sand to the mixing pot and then add water;

[0047] Add river sand to the funnel in advance, and wait for the program to automatically control the slow addition of river sand to the mixing pot; moisten the mixing pot and add the weighed tap water to the mixing pot.

[0048] S43 Add half of the cement and water reducer to the mixing pot and stir for 3 minutes, then divide the remaining cement and water reducer into four equal parts and add them to the mixing pot in sequence and stir for 3 minutes;

[0049] Add half of the cement and water reducer into the mixing pan and run at low speed for 3 minutes; divide the remaining cement and water reducer into four equal parts and add them into the mixing pan successively, then stir at low speed for 3 minutes.

[0050] S44 After the stirring is completed, fill a 300 ml beaker with the mortar, place it on the vibrating table for vibration, remove the excess part with a spatula and weigh the mass of the paste in the beaker;

[0051] After the stirring is completed, fill a 300 ml beaker with the mortar, place it on the vibrating table for vibration, remove the excess part with a spatula and weigh the mass of the paste in the beaker.

[0052] S45 Reduce the water-solid ratio and repeat the above steps until the maximum solid concentration is obtained;

[0053] Reduce the water-solid ratio and repeat the above steps until the maximum solid concentration M is obtained, and then end the test.

[0054] S5 According to the remaining packing density, use the compressible packing model to obtain the actual packing density of the mixture;

[0055] The operation process of the compressible packing model includes:

[0056] Determine each material parameter; calculate the initial remaining packing density; add the water reducer and calculate the remaining packing density and volume fraction after compounding; calculate the loosening effect and wall-attached effect coefficients; calculate the virtual packing density according to the initial remaining packing density and the remaining packing density after compounding; output the actual packing density of the mixture; use the film thickness theory to calculate the water film thickness and the net paste film to predict the workability of the mortar.

[0057] The compressible packing model of the present invention will be described below.

[0058] The compressible packing model is developed on the basis of the linear packing model. This model not only considers the interaction between particles, that is, the wall-attached effect formed by small particles around large particles and the loosening effect formed by large particles near small particles, but also considers the influence of different construction processes on the material properties. In the process of calculating the packing density, it is necessary to determine the particle size distribution, and at the same time, some parameters need to be determined through experiments. The calculation formulas of each parameter are as follows:

[0059] (1) The characteristic particle size d of each particle size range i : First, determine the particle size distribution of the solid particles of each material, then divide the particle size range, and determine the characteristic particle size of this particle size range. The formula is as follows:

[0060] log 10 (d i ) = [log10 (d max ) + log 10 (d min )) / 2] (1)

[0061] where d in which d min and d and d max respectively represent the diameter of the smallest or largest particle in a particle size range, in mm. respectively represent the diameter of the smallest or largest particle in a particle size range, in mm.

[0062] (2) The volume fraction y (2) The volume fraction y i of each particle size of each material: For powder materials, it can be measured by a laser particle size analyzer; for sand and gravel, it is calculated by screening with a standard vibrating sieve machine. of each particle size of each material: For powder materials, it can be measured by a laser particle size analyzer; for sand and gravel, it is calculated by screening with a standard vibrating sieve machine.

[0063] (3) When an n - element mixture is stacked, the formula for the virtual stacking density when the i - th particle is the main one is: (3) When an n - element mixture is stacked, the formula for the virtual stacking density when the i - th particle is the main one is:

[0064]

[0065] where γ where γ i represents the virtual stacking density of the i - th particle size particle; β represents the virtual stacking density of the i - th particle size particle; β i represents the remaining stacking density of the i - th particle size particle; a represents the remaining stacking density of the i - th particle size particle; a ij represents the loosening effect coefficient generated by the j - th particle size particle on the i - th particle size particle; b represents the loosening effect coefficient generated by the j - th particle size particle on the i - th particle size particle; b ij represents the wall - adhering effect coefficient generated by the j - th particle size particle on the i - th particle size particle; y represents the wall - adhering effect coefficient generated by the j - th particle size particle on the i - th particle size particle; y j represents the volume fraction of the j - th particle size particle. represents the volume fraction of the j - th particle size particle.

[0066]

[0067] b b ij =1 - (1 - d = 1 - (1 - d i / d / d j ) ) 1.50 (j = 1, 2, 3,......, i - 1) (4) (j = 1, 2, 3,......, i - 1) (4)

[0068] In addition, due to the non - penetrability condition constraint of the i - th particle, γ = min(λ In addition, due to the non - penetrability condition constraint of the i - th particle, γ = min(λ i ), where 1 ≤ i ≤ n. ), where 1 ≤ i ≤ n.

[0069] The above content is the theoretical formula for the important parameters related to the virtual stacking density. In order to combine with the actual stacking model of the mixture, De Larrard proposed the compaction index K, an important parameter reflecting the relationship between the virtual stacking density and the actual stacking density, based on the different actual compaction effects of the mixture under different compaction methods, as shown in the following formula (5): The above content is the theoretical formula for the important parameters related to the virtual stacking density. In order to combine with the actual stacking model of the mixture, De Larrard proposed the compaction index K, an important parameter reflecting the relationship between the virtual stacking density and the actual stacking density, based on the different actual compaction effects of the mixture under different compaction methods, as shown in the following formula (5):

[0070]

[0071] In the formula, K represents the compaction index; α In the formula, K represents the compaction index; α tIndicates the actual packing density.

[0072] Among them, the compaction index K has a great relationship with the packing method. De Larrard summarized the values of K through a large number of experiments as follows Figure 7 . According to Figure 7 the value table of K under different packing methods shown, when K takes 6.7 for the packing method of the mixture particle system, the actual packing density of the mixture particle system can be inversely calculated.

[0073] (4) The remaining packing density β of each particle size grade of each material: For quartz sand and gravel, screening can be carried out first, and then the actual packing density is measured for each particle size grade through experiments, and substituted into formula (6) to inversely calculate β i , formula (5) is d1 = d2 = … = d n = d i , and y1 = y2 = … = y n = y i substituted into (2) and (5). However, for powder materials, it is difficult to screen them and conduct experiments on each particle size grade to determine. Here, we must assume that the remaining packing densities of each particle size grade of this powder material are equal, that is, β1 = β2 = … = β n = β i , then determine its actual packing density α of this material through experiments t , and then inversely calculate β through (2) and (5) i .

[0074]

[0075] (5) Assume that a certain concrete has n kinds of materials (components), the solid volume ratios of each component are Y (x = 1, …, n) and there is each material has its own particle size distribution curve, but has a common m particle size grade intervals, and the characteristic particle size of each particle size grade interval is d i (i = 1, 2 …, m). Let the volume ratio of the particles in the i-th particle size grade interval of the j-th material in this material be y ix , where its remaining packing density is β ij , then, we use the following two formulas to convert an n-phase into an m-level mixed system, where the particle size of each level is d i , the composite solid volume fraction is y i *, and the composite remaining packing density is β i * is calculated by the following two formulas for the composite volume fraction and the composite remaining packing density.

[0076]

[0077] For calculation examples, seeFigure 6 。

[0078] Based on the result output by the compressible packing model of S6, the film thickness of the mortar is calculated by using the film thickness theory to realize the prediction of the working performance of the mortar.

[0079] A method for predicting the working performance of mortar based on the wet measurement method and the compressible packing model of the present invention. First, the remaining packing density of each material is obtained according to the wet measurement method experiment, then the actual packing density of the paste is determined according to the compressible packing model, and then the working performance of the mortar is predicted by calculating the paste film thickness according to the film thickness theory; finally, the final mix ratio is obtained through the water-cement ratio and the mortar aggregate ratio. The present invention calculates the influence of the water reducer on the working performance of the mortar based on the wet measurement method - compressible packing model - film thickness theory. Therefore, the mix ratio calculated by using the method of the present invention has high working performance and can reflect the influence of different water reducer dosages on the working performance of the mortar. By making full use of the existing data, the requirement for the experience of experimental personnel is reduced, the number of experiments is greatly reduced, and at the same time, it can provide a certain scientific basis for the future research on the working performance of concrete based on the film thickness theory.

[0080] The above-disclosed is only a preferred embodiment of the present invention, and of course, it cannot be used to limit the scope of the rights of the present invention. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A method for predicting the workability of mortar based on the wet measurement method and the compressible packing model, characterized in that Including: Preparing raw materials for preparing mortar; Determining the designed working performance of mortar; Measuring the particle sizes and volume fractions of cement and fly ash by a laser particle size analyzer; Using the wet measurement method to test and obtain the actual packing density of each gradation material, and back-calculating the remaining packing density; According to the remaining packing density, using the compressible packing model to obtain the actual packing density of the mixture; According to the result output by the compressible packing model, using the film thickness theory to calculate the film thickness of mortar to realize the prediction of the working performance of mortar.

2. The method for predicting the working performance of mortar based on the wet measurement method and the compressible packing model according to claim 1, wherein The raw materials of the mortar include water, cement, water reducer, fly ash, and river sand.

3. The method for predicting the working performance of mortar soil based on the wet measurement method and the compressible packing model according to claim 2, wherein The specific steps of using the wet measurement method to test and obtain the actual packing density of each gradation material and back-calculating the remaining packing density include: Determining the water-solid ratio and preparing water, cement, water reducer, and river sand at this ratio; Adding river sand to the mixing pot and then adding water; Adding half of the cement and water reducer to the mixing pot and stirring for 3 minutes, and then dividing the remaining cement and water reducer into four equal parts and adding them to the mixing pot in turn and stirring for 3 minutes; After stirring is completed, filling the mortar into a beaker with a volume of 300 ml, placing it on a vibrating table for vibration, removing the excess part with a spatula and weighing the mass of the slurry in the beaker; Reducing the water-solid ratio and repeating the above steps until the maximum solid concentration is obtained.

4. The method for predicting the working performance of mortar based on the wet measurement method and the compressible packing model according to claim 3, wherein The operation process of the compressible packing model includes: Determining each material parameter; Calculating the initial remaining packing density; Adding a water reducer and calculating the remaining packing density and volume fraction after compounding; Calculating the loosening effect and the wall adhesion effect coefficient; Calculating the virtual packing density according to the initial remaining packing density and the remaining packing density after compounding; Outputting the actual packing density of the mixture; Using the film thickness theory to calculate the water film thickness and the neat cement paste film to predict the working performance of mortar.

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