CN115855768A - Quantitative analysis method for surface characteristics and mortar performance of machine-made sand based on double parameters - Google Patents
Quantitative analysis method for surface characteristics and mortar performance of machine-made sand based on double parameters Download PDFInfo
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Abstract
The invention belongs to the technical field of detection of fine aggregates for mortar and concrete, and discloses a quantitative analysis method for surface characteristics and mortar performance of machine-made sand based on double parameters. The double-parameter machine-made sand surface characteristic analysis method adopted by the invention integrates the macroscopic morphology characteristics such as edges and roundness and the microscopic surface characteristics such as fracture, stone powder content and adsorbability of machine-made sand by adopting an image analysis method, thereby better and more comprehensively representing the machine-made sand surface characteristics, further analyzing the influence of the machine-made sand surface characteristics on various performances of mortar, verifying the correlation between the double-parameter machine-made sand surface characteristic representation method and the mortar performance by a statistical method, and solving the problem that the relationship between the current machine-made sand surface characteristic parameters and the mortar performance is difficult to establish.
Description
Technical Field
The invention belongs to the technical field of detection of fine aggregates for mortar and concrete, and particularly relates to a quantitative analysis method for surface characteristics and mortar performance of machine-made sand based on double parameters.
Background
The fine aggregate is one of main components of mortar and concrete, river sand is the most traditional fine aggregate, excessive mining is caused due to huge demand of the fine aggregate in engineering construction, under the requirement of environmental protection, river sand mining is gradually prohibited, and supply is in short supply, in order to meet the high demand of building construction and infrastructure construction on the fine aggregate, the machine-made sand is gradually a substitute of the river sand, the machine-made sand is the fine aggregate prepared by crushing, shaping, screening and other processes of parent rock, the machine-made sand and natural sand have different forming processes and have great difference, and the research on relevant parameters and indexes of the machine-made sand particle shape is not sufficient in the existing data documents, and only the research is related in few specifications;
the current research mostly focuses on quantitative or qualitative research on the surface characteristics of the machine-made sand by using various technical measures or qualitative research on the influence of the surface characteristics of the machine-made sand on the performance of the cement-based material, and part of the existing standards provide a testing method for particle morphology parameters, but cannot provide specific index requirements, and even cannot provide a quantitative relation with the cement-based material: it is seen that it is still difficult to establish a quantitative relationship between the surface characteristics of the machine-made sand and the properties of the cement-based material at home and abroad at present: therefore, the invention aims to fill the gap and establish the quantitative relation between the surface characteristics of the machine-made sand and the performance of the cement-based material, thereby promoting the better application of the machine-made sand in mortar and concrete, further ensuring various performances of the cement-based material and effectively relieving the resources and economic pressure of river sand.
Disclosure of Invention
The invention aims to provide a quantitative analysis method for the surface characteristics and mortar performance of machine-made sand based on double parameters, so as to solve the problems in the background technology.
In order to achieve the above purpose, the invention provides the following technical scheme: a quantitative analysis method of surface characteristics and mortar performance of machine-made sand based on double parameters comprises the steps of firstly, analyzing a machine-made sand sample with certain mass by adopting an image analysis method and a nitrogen adsorption BET method to respectively obtain double parameters of circularity and specific surface area of the machine-made sand sample; secondly, establishing the relativity of the flexural strength, the compressive strength, the tensile strength and the fluidity of the machine-made sand and the mortar; and then, quantitatively representing the influence of the surface characteristics of the machine-made sand on the fluidity and various strengths of the mortar through double parameters.
Preferably, the mechanical sand sample is analyzed by an image analysis method to obtain the circularity parameter of the mechanical sand.
Preferably, the nitrogen adsorption BET method is used for analyzing the machine-made sand sample to obtain the specific surface area parameter of the machine-made sand.
Preferably, the influence of the surface characteristics of the machine-made sand on the flexural strength of the mortar and the influence of the surface morphology and the edges of the machine-made sand on the strength of the mortar are quantitatively characterized through double parameters of the surface characteristics of the machine-made sand.
Preferably, the influence of the surface characteristics of the machine-made sand on the compressive strength of the mortar is quantified and characterized by two parameters of the surface characteristics of the machine-made sand.
Preferably, the influence of the surface characteristics of the machine-made sand on the tensile strength of the mortar is quantified and characterized by two parameters of the surface characteristics of the machine-made sand.
Preferably, the influence of the machine-made sand on the fluidity of the mortar is quantified and characterized by the double parameters of the surface characteristics of the machine-made sand, and the correlation is greatly higher than that of a single image analysis method.
Preferably, a quantitative relation between the saturation surface dry water absorption and the specific surface area of the machine-made sand is established, so that a path for deducing the specific surface area of the machine-made sand is obtained, and the specific surface area obtaining method is simplified.
Preferably, the correlation coefficient of the surface characteristics of the machine-made sand based on the double parameters and the quantized relationship among the flexural strength, the compressive strength and the tensile strength of the mortar is more than 0.90, and the correlation coefficient of the fluidity is more than 0.85.
The invention has the following beneficial effects:
the invention aims to solve the problem that the quantitative relationship cannot be established between the surface characteristics of the machine-made sand and the corresponding properties of a cement-based material at present, combines the circularity obtained by adopting an image analysis method and the specific surface area measured by a nitrogen adsorption BET method, establishes the correlation between the surface characteristics of the machine-made sand and the fluidity of the machine-made sand mortar and various strengths, has better correlation with the properties of the machine-made sand mortar compared with the existing single image analysis method or the specific surface area method, and overcomes the defect that the existing machine-made sand surface characteristic representation method is difficult to establish the relationship with the properties of the mortar.
Drawings
FIG. 1 is an image of a typical machine-made sand particle of the present invention;
FIG. 2 is a schematic illustration of the particle morphology parameters of the present invention;
FIG. 3 is a graph showing a comparison of the change trend of the circularity of the present invention;
FIG. 4 is a comparison graph of aspect ratio variation trend according to the present invention;
FIG. 5 is a graph showing the results of compressive strengths of the mortar of the present invention for 1,3,7 and 28 days;
FIG. 6 is a graph showing the results of flexural strength of the mortar of the invention for 1,3,7 and 28 days;
FIG. 7 is a graph showing the results of tensile strength of the mortar of the present invention at 1,3,7 and 28 days;
FIG. 8 is a graphical representation of the results of the fluidity of the mortar of the present invention;
FIG. 9 is a graph of the dry water absorption versus specific surface area for a saturated surface of a machined sand in accordance with the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1 to fig. 9, an embodiment of the present invention provides a quantitative analysis method for surface characteristics and mortar performance of machine-made sand based on two parameters, first, by analyzing a certain mass of machine-made sand sample by using an image analysis method and a nitrogen adsorption BET method, two parameters of circularity (Rd) and specific surface area (SSANA) of the machine-made sand sample are respectively obtained; secondly, establishing the relativity of the flexural strength, the compressive strength, the tensile strength and the fluidity of the machine-made sand and the mortar; and then, quantitatively representing the influence of the mechanical sand surface characteristics on the fluidity and various strengths of the mortar through double parameters of the mechanical sand surface characteristics.
Analyzing a machine-made sand sample by using an image analysis method to obtain a circularity parameter of the machine-made sand;
firstly, screening machine-made sand, then respectively carrying out image acquisition on the machine-made sand with the particle sizes of 2.36mm, 1.15mm, 0.60mm, 0.30mm and 0.15mm, and analyzing the acquired image by adopting image analysis software to obtain primary parameters such as area, perimeter, length (Fisher diameter along the small axis of an object) and width (Fisher diameter along the long axis of the object); then, continuously operating the primary parameters obtained by image processing to obtain other secondary characterization parameters such as circularity, length-diameter ratio and the like, and further obtaining two-dimensional morphology parameters of the machine-made sand, wherein the minimum sample quantities corresponding to the machine-made sand with the particle sizes of 2.36mm, 1.15mm, 0.60mm, 0.30mm and 0.15mm and meeting the statistical significance are respectively 6 g, 3 g, 1 g, 0.1 g and 0.01 g;
the digital image of mechanism sand sample is obtained through industry electron microscope, and this system includes 2K high definition camera, electron display screen, the micro-auxiliary objective of high definition electron of different multiples, eyepiece, lifting support, portable objective table and parallel bottom light source. Can select the camera lens of suitable multiple to carry out image observation and shooting according to the sample demand of different particle diameters, portable objective table facilitates for the selection of sample field of vision, and high definition camera is arranged in directly over objective table and the parallel bottom light source, avoids the shadow to the interference of mechanism sand image.
After the machine-made sand images of all the particle sizes are obtained, image-Pro Plus software (hereinafter abbreviated as IPP) is used for processing and analyzing the images, supports various digital cameras, image acquisition cards and other equipment, contains abnormally rich enhancement and measurement tools, and can be used for 2D and 3D Image analysis. The IPP software provides convenience for the application of the digital image method in the aspects of image processing, counting measurement, calculation analysis and the like. Primary parameters such as area, perimeter, length (fischer-tropsch diameter along the minor axis of the object) and width (fischer-tropsch diameter along the major axis of the object) are directly available. And then, continuously operating the primary parameters obtained by image processing to obtain other secondary characterization parameters such as circularity, length-diameter ratio and the like. Quantizing two-dimensional (2D) information of the particle;
the method comprises the following specific steps:
(one) digital image acquisition:
(1) Weighing the mass of the sample by using an electronic analytical balance;
(2) Turning on a power supply of an industrial electron microscope system, and turning on a display screen and a flat light source below an objective table;
(3) Placing a small amount of samples on an objective table, and adjusting the magnification and distance of a microscope until clear and moderate-size particle images are obtained;
(4) Taking back a sample, placing the scale on an objective table, adjusting the direction to enable the scale to be parallel to the picture boundary, and clicking a mouse to shoot an image;
(5) Slowly pouring a proper amount of samples onto an industrial electron microscope stage in a manner of dispersing as much as possible, and separating the overlapped samples by using tools such as a small stick;
(6) Clicking a mouse to shoot an image after confirming that the samples are not overlapped;
(7) Removing the shot sample by using a brush;
(8) And (5) repeating the steps 5-7 until all the samples in the group are shot, and storing the images.
(II) digital image processing:
(1) Opening the shot image in IPP software;
(2) Length calibration: selecting a scale image, clicking Measure-Calibration-Spatial, and setting a scale;
(3) Selecting measurement parameters: clicking Measure-Count/Size-Measure-Select measures-to Select the required measurement parameters and limiting the parameter range;
(4) Target selection and measurement: selecting a sample image, clicking Measure-Calibration-Select Spatial, selecting the scale set in the step 3, clicking Measure-Count/Size-Select Colors-history Based, and selecting missing color blocks to ensure that the boundary selection is accurate as much as possible, namely-Apply Mask-Close-Count;
(5) Exporting the measurement result to an EXCEL table;
(6) And (5) repeating the steps 4-5 until all the images are processed, closing the IPP software, and opening the EXCEL table for data statistics.
Based on the above data, parameters such as roundness (Rd), aspect ratio (LW), etc., describing the shape of the particles were calculated. The roundness can be expressed as:
wherein Rd is roundness, A is particle shadow area, mm 2 And P is the projected perimeter of the particle, mm. The aspect ratio can be expressed as:
where LW is the aspect ratio, L is the length (Fisher-Elder diameter along the minor axis of the object), mm, and W is the diameter (Fisher-Elder diameter along the major axis of the object), mm.
In order to obtain representative surface characteristic parameters of the machine-made sand, the minimum number of machine-made sand samples for image analysis is determined. Most of the existing test analysis methods adopt the quantity of sand particles as a measurement unit, which is not universal with a mass unit used in actual engineering application and is inconvenient to operate. The invention tries to determine the minimum sample quality of the machine-made sand required by the image analysis method through statistical analysis so as to ensure the stability and the representativeness of various image characteristic parameters and meet the requirements of practical engineering application. Through repeated tests, the minimum sampling mass when the deviation of the specific circumferences of the three parallel groups is not more than 5% is taken as the sampling mass, so that the minimum sampling mass of the machine-made sand with each particle size is obtained as shown in table 1:
TABLE 1 minimum sample Mass for image analysis
| Particle size (mm) | 2.36 | 1.18 | 0.60 | 0.30 | 0.15 |
| Number of samples (g) | 6.00 | 3.00 | 1.00 | 0.10 | 0.01 |
A typical machine-made sand particle image is shown in figure 1 of the specification.
Analyzing a machine-made sand sample by using a nitrogen adsorption BET method to obtain a specific surface area parameter of the machine-made sand;
the sample adopts full-grade prepared machine-made sand, and the quantity of the sample is 10g, so that the influence of factors such as stone powder content, particle surface cracks and the like in the machine-made sand on the specific surface area of the fine aggregate can be considered;
the nitrogen adsorption BET method combines the microscopic surface characteristics of the machine-made sand such as surface cracks, adsorbability and the like, can reflect the influence of the content of the stone powder on the specific surface area of the machine-made sand, and can better analyze the surface characteristics of the machine-made sand. The sand samples used in the nitrogen adsorption test were fully graded and mixed uniformly, and each test sample was about 10g. And (3) analyzing the full-grade sand sample by a nitrogen adsorption method by adopting a static volumetric method specific surface and aperture analyzer.
The specific surface area instrument test principle is as follows:
introducing a certain amount of adsorbate gas (N is adopted in the invention) into the sample tube under the condition of low temperature (liquid nitrogen bath is adopted in the invention, 77.3K) 2 ) Directly measuring the adsorption partial pressure by controlling the equilibrium pressure in the sample tube, and obtaining the adsorption quantity of the partial pressure point by a gas state equation (PV = nRT); increasing the adsorption equilibrium pressure by gradually adding adsorbate gas to obtain an adsorption isotherm; by gradually pumpingAnd (4) discharging the adsorbate gas to reduce the adsorption equilibrium pressure to obtain a desorption isotherm. The sample to be measured is in a sample tube with a fixed volume, and the adsorbate does not flow relative to the dynamic chromatography, so the method is called as a static volume method.
BET specific surface area hypothesis theory:
the BET specific surface area test method is known based on the well-known BET theory. BET is an acronym for three scientists (Brunauer, emmett, and Teller) who propose a model for monolayer adsorption and derive from classical statistical theory the equation of the relationship between the monolayer adsorption quantity Vm and the multilayer adsorption quantity V, the well-known BET equation. The equation is established on the theoretical basis of multilayer adsorption, is closer to the actual adsorption process of substances, and becomes the theoretical basis of particle surface adsorption science. Because the test result is more accurate, the method is widely applied to the research of the adsorption performance of the particle surface and the data processing of related detection instruments.
The BET equation is expressed as:
can be converted into
In the formula:
p is the pressure after adsorption equilibrium, bar;
c-a constant related to the adsorption performance of the adsorbent;
po — the saturated vapor pressure of the adsorbate at the adsorption temperature;
vm-single layer saturated adsorption capacity of adsorbent to adsorbate, ml/g;
v is the adsorption capacity of the adsorbent to the adsorbate at the adsorption equilibrium pressure P, ml/g.
Will be provided with
Is paired and/or matched>
Plotting the resulting intercept->
Slope->
Can obtain the product
Then
Specific surface area calculation formula
S＝4.35V m (7)
In the formula: s is the specific surface area, m 2 (ii)/g; 4.35 area occupied by 1ml of nitrogen monolayer under standard conditions, m 2 And/ml. Theory and practice show that when the P/P0 point is in the range of 0.05-0.35, the BET equation is identical with the actual adsorption process, and the graphic linearity is good, so the point selection in the actual test process is in the range.
The method comprises the following steps of (1) quantitatively representing the influence of the surface characteristics of the machine-made sand on the flexural strength of the mortar and the influence of the surface morphology and the edges of the machine-made sand on the strength of the mortar through double parameters of the surface characteristics of the machine-made sand;
obtaining two mechanism sand characteristic parameters of circularity and specific surface area by an image analysis method and a nitrogen adsorption BET method, carrying out a mortar performance test, and carrying out a flexural strength test according to the cement mortar strength test method GB/T17671; establishing the correlation between the mortar performance and the surface characteristics of the machine-made sand according to various performance indexes of the mortar, the circularity (Rd) obtained by a two-dimensional image analysis method and the specific surface area (SSANA) obtained by a nitrogen adsorption BET method, and obtaining the relation between the rupture strength and the surface characteristics of the machine-made sand as follows:
the relation between the 28-day mortar flexural strength (ff, 28) and two parameters can be expressed as follows: f. of f,28 ＝A f – B f ·Rd+C f ·SSA NA ，A f 、B f And C f The coefficient is the regression coefficient of the flexural strength under the conditions of different water-gel ratios and rubber-sand ratios.
The influence of the surface characteristics of the machine-made sand on the compressive strength of the mortar is represented by double-parameter quantification of the surface characteristics of the machine-made sand;
obtaining two mechanism sand characteristic parameters of circularity and specific surface area by an image analysis method and a nitrogen adsorption BET method, carrying out a mortar performance test, and carrying out a compressive strength test according to the cement mortar strength test method GB/T17671; establishing the correlation between the mortar performance and the surface characteristics of the machine-made sand according to various performance indexes of the mortar, the circularity (Rd) obtained by a two-dimensional image analysis method and the specific surface area (SSANA) obtained by a nitrogen adsorption BET method, and obtaining the relation between the compression strength and the surface characteristics of the machine-made sand as follows:
the relation between the 28-day mortar compressive strength (fc, 28) and the two parameters can be expressed as f c,28 ＝A c – B c ·Rd+C c ·SSA NA ，A c 、B c And C c And the coefficient is the regression coefficient of the compressive strength under the conditions of different water-cement ratios and mortar ratios.
The influence of the surface characteristics of the machine-made sand on the tensile strength of the mortar is represented by double-parameter quantification of the surface characteristics of the machine-made sand;
obtaining two mechanism sand characteristic parameters of circularity and specific surface area by an image analysis method and a nitrogen adsorption BET method, carrying out a mortar performance test, and carrying out a tensile strength test according to a hydraulic concrete test method DL/T5150; establishing the correlation between the mortar performance and the surface characteristics of the machine-made sand according to various performance indexes of the mortar, the circularity (Rd) obtained by a two-dimensional image analysis method and the specific surface area (SSANA) obtained by a nitrogen adsorption BET method, and obtaining the relation between the compression strength and the surface characteristics of the machine-made sand as follows:
the 28-day tensile strength (ft, 28) versus two parameters can be expressed as: f. of t,28 ＝A t –B t ·Rd+ C t ·SSA NA ，A t 、B t And C t The coefficient is the regression coefficient of the tensile strength under the conditions of different water-to-gel ratios and different rubber-to-sand ratios.
The influence of the machine-made sand on the mortar Fluidity (FL) is represented in a quantitative manner by double parameters of the surface characteristics of the machine-made sand, and the correlation is greatly higher than that of a single image analysis method;
obtaining two mechanism sand characteristic parameters of circularity and specific surface area by an image analysis method and a nitrogen adsorption BET method, performing a mortar performance test, and performing a fluidity test on mortar prepared from different sand samples according to the Cement mortar fluidity determination method GB/T2419; establishing the correlation between the mortar performance and the surface characteristics of the machine-made sand according to various performance indexes of the mortar, the circularity (Rd) obtained by a two-dimensional image analysis method and the specific surface area (SSANA) obtained by a nitrogen adsorption BET method, and obtaining the relation between the fluidity and the surface characteristics of the machine-made sand as follows:
the relationship between fluidity and two parameters can be expressed as: FL = A fl +B fl ·Rd+C fl ·SSA NA ，A fl 、 B fl And C fl The flow regression coefficients under different water-to-gel ratios and rubber-to-sand ratios are obtained.
The method comprises the following steps of establishing a quantitative relation between the saturation surface dry water absorption and the specific surface area of the machine-made sand, so as to obtain a path for deducing the specific surface area of the machine-made sand, and simplifying a specific surface area acquisition method;
establishing a relation with the specific surface area through saturation surface dry water absorption (SWA), thereby obtaining a path for deducing the specific surface area, simplifying a specific surface area test method, wherein the saturation surface dry water absorption (SWA) and the specific surface area of the machine-made sand have good correlation and can be expressed as follows: SSA NA ＝1.4·(SWA) A + B, A and B are regression coefficients of quantitative relationship between saturated surface dry water absorption and specific surface area.
Wherein, the correlation coefficient of the quantitative relation between the surface characteristics of the machine-made sand based on the double parameters and the flexural strength, compressive strength and tensile strength of the mortar is more than 0.90, and the correlation coefficient of the fluidity is more than 0.85;
through analysis of a large amount of data of various machine-made sand samples, the correlation coefficients of the surface characteristics of the double-parameter machine-made sand, the conversion strength, the compressive strength and the tensile strength of the mortar are all above 0.90, and the correlation coefficient of the surface characteristics of the double-parameter machine-made sand and the fluidity of the mortar is above 0.85, so that high correlation is presented.
The computational analysis of circularity and aspect ratio was performed as follows: in order to continuously explore the relationship between the mortar performance and the appearance of the fine aggregate particles, the primary parameters obtained by image processing are continuously calculated to obtain other secondary characterization parameters such as circularity, length-diameter ratio and the like.
The circularity calculation formula:
in the formula:
rd-circularity;
a-projected area of particle, mm 2 ；
P-projected perimeter of the particle, mm.
According to the sample mass with the smallest particle size, the circularity of each particle is calculated comprehensively and then averaged, and the result is shown in the attached figure 3 of the specification.
The closer the circularity is to 1, the closer the particle projection is to a circle. In the case of a profile shape close to each other, the circularity also expresses the roughness of the surface, and the smaller the circularity, the rougher the particle surface. As can be seen from the comparison graph of the change trend of the circularity in fig. 3, the total circularity of the standard sand and river sand as natural sand is larger than that of two kinds of machine-made sand, namely, tuff sand and granite sand, i.e., the particles are closer to a circle, the surface is smoother, and the result is consistent with the observation result of a macroscopic viewing angle. The overall circularity is ranked from large to small as "standard sand > river sand > tuff sand > granite sand".
Besides circularity, another parameter having a representation, i.e. aspect ratio, can be obtained, which is calculated by the formula:
in the formula:
LW-aspect ratio;
l is the length of the minimum circumscribed rectangle of the particle projection, mm;
w is the width of the minimum circumscribed rectangle of the particle projection, mm.
The length-diameter ratio of each particle is calculated and then averaged, and the calculation result is shown in figure 4 in the specification.
The larger the length-diameter ratio, the more slender the particle morphology is; the smaller the aspect ratio, the more uniform the particle morphology along each axis. In general, the aspect ratio tends to increase with decreasing particle size, and natural sand generally has an aspect ratio less than machine-made sand.
And then, carrying out a nitrogen adsorption test on the unscreened raw sand sample by using a static capacity method specific surface and aperture analyzer. The test procedure was as follows:
weighing sample
(1) Putting the measuring cylinder into an electronic analytical balance, and peeling;
(2) Placing a large sample tube in the measuring cylinder, and weighing the large sample tube to obtain the mass A of the large sample tube;
(3) And taking out the large-size sample tube, placing a sample loading funnel at the tube opening of the sample tube, and loading about 10g of fully-graded fine aggregate sample which is uniformly mixed.
(II) degassing
(1) Fixing the sample tube with the sample on a degassing position, and properly tightening screws (if the sample tube is over tightened, the sample tube is easy to break, and if the sample tube is not over tightened, air leakage occurs);
(2) Sleeving the heating furnace on the sample tube, and moving out the bearing plate to support the heating furnace;
(3) Opening gas (high-purity nitrogen gas 0.3MPa and high-purity helium gas 0.2 MPa), turning on a power supply and software;
(4) Setting degassing state parameters (degassing at 200 ℃, degassing time of 180min, and difficult flying mode);
(5) Starting degassing, and observing for a period of time until the degassing position can be temporarily separated if the airtightness detection is successful;
(6) After degassing is finished, taking down the heating furnace to restore the sample tube to normal temperature;
(7) The sample tube was taken off and placed in a graduated cylinder on an electronic analytical balance, and its total mass B was weighed.
(III) test
(1) Adding a filling rod into the sample tube, installing a test position, and properly tightening a screw;
(2) Installing an analysis station plug or an empty sample tube at the original degassing position;
(3) Pouring liquid nitrogen into the Dewar cup, placing the Dewar cup under a test position, and covering a protective cover;
(4) Setting test parameters (sample name, sample mass C = B-A, effective analysis station, test content, liquid nitrogen temperature 77.3K);
(5) Starting the test, observing for a period of time until the test site can leave temporarily if the airtightness detection is successful;
(6) After the test is finished, covering the Dewar cup cover to prevent the liquid nitrogen from volatilizing, and storing an analysis report;
(7) After the sample tube is restored to normal temperature, taking down the sample tube, and replacing the original test station with a clean empty sample tube;
(8) Closing the software, the power supply and the steel cylinder valve;
(9) And pouring out the sample, and cleaning and drying glass equipment such as a sample tube, a sample loading funnel, a filling rod and the like.
The nitrogen adsorption method obtains the sample specific surface area and pore size distribution test results based on the BET equation and BJH hypothesis as shown in table 2 below.
TABLE 2 specific surface area test results
The specific surface areas obtained by the BET method are classified according to the size, and have great differences, namely 'tuff sand > river sand > granite sand > standard sand'. The accumulated pore volume sequencing result obtained by the BJH method is 'tuff sand > river sand > granite sand > standard sand', and the change trend of the tested data is similar to the change trend of the corresponding BET specific surface area numerical value. It is judged from this that the specific surface area result of the particles obtained by the BET method is less affected by the change in particle shape and mainly consists of the pore area.
And (3) carrying out fluidity test on the mortar consisting of different sand samples according to GB/T2419 Cement mortar fluidity test method. The flexural strength and the compressive strength are carried out according to GB/T17671 of cement mortar strength test method, and the tensile strength is carried out according to DL/T5150 of hydraulic concrete test method.
The mortar mixture ratio is shown in table 3:
TABLE 3 Cement mortar ratio
| Cement (g) | Sand (g) | Water (g) | Water cement ratio |
| 450 | 1350 | 225 | 0.5 |
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (9)
1. A quantitative analysis method for surface characteristics and mortar performance of machine-made sand based on double parameters is characterized by comprising the following steps: firstly, analyzing a machine-made sand sample with certain mass by adopting an image analysis method and a nitrogen adsorption BET method to respectively obtain two parameters of the circularity and the specific surface area of the machine-made sand sample; secondly, establishing the relativity of the flexural strength, the compressive strength, the tensile strength and the fluidity of the machine-made sand and the mortar; and then, quantitatively representing the influence of the mechanical sand surface characteristics on the fluidity and various strengths of the mortar through double parameters of the mechanical sand surface characteristics.
2. The quantitative analysis method for the surface characteristics and the mortar performance of the machine-made sand based on the double parameters of claim 1, which is characterized in that: and analyzing the machine-made sand sample by using an image analysis method to obtain the circularity parameter of the machine-made sand.
3. The quantitative analysis method for the surface characteristics and the mortar performance of the machine-made sand based on the double parameters of claim 1, which is characterized in that: and analyzing the machine-made sand sample by using a nitrogen adsorption BET method to obtain the specific surface area parameter of the machine-made sand.
4. The quantitative analysis method for the surface characteristics and the mortar performance of the machine-made sand based on the double parameters of claim 1, which is characterized in that: the influence of the surface characteristics of the machine-made sand on the flexural strength of the mortar and the influence of the surface morphology and the edges of the machine-made sand on the strength of the mortar are quantitatively represented by double parameters of the surface characteristics of the machine-made sand.
5. The quantitative analysis method for the surface characteristics and the mortar performance of the machine-made sand based on the double parameters of claim 1, which is characterized in that: the influence of the surface characteristics of the machine-made sand on the compressive strength of the mortar is quantitatively represented by the double parameters of the surface characteristics of the machine-made sand.
6. The quantitative analysis method for the surface characteristics and the mortar performance of the machine-made sand based on the double parameters of claim 1, which is characterized in that: the influence of the surface characteristics of the machine-made sand on the tensile strength of the mortar is quantitatively represented by the double parameters of the surface characteristics of the machine-made sand.
7. The quantitative analysis method for the surface characteristics and the mortar performance of the machine-made sand based on the double parameters of claim 1, which is characterized in that: the influence of the machine-made sand on the fluidity of the mortar is represented by double-parameter quantification of the surface characteristics of the machine-made sand, and the correlation is greatly higher than that of a single image analysis method.
8. The quantitative analysis method for the surface characteristics and the mortar performance of the machine-made sand based on the double parameters of claim 1, which is characterized in that: a quantitative relation between the dry water absorption of the saturation surface and the specific surface area of the machine-made sand is established, so that a path for deducing the specific surface area of the machine-made sand is obtained, and the specific surface area acquisition method is simplified.
9. The method for quantitatively analyzing the surface characteristics and the mortar performance of the machine-made sand based on the double parameters according to claim 1, wherein the method comprises the following steps: the correlation coefficient of the quantitative relation between the surface characteristics of the machine-made sand and the flexural strength, compressive strength and tensile strength of the mortar based on the double parameters is more than 0.90, and the correlation coefficient of the fluidity is more than 0.85.
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| CN117686378B (en) * | 2024-02-02 | 2024-05-03 | 中国电建集团西北勘测设计研究院有限公司 | Method for measuring saturation surface dry water absorption rate of artificial fine aggregate |
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