CN110672494B - Method for rapidly measuring different porosities of porous concrete - Google Patents
Method for rapidly measuring different porosities of porous concrete Download PDFInfo
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- CN110672494B CN110672494B CN201911021025.9A CN201911021025A CN110672494B CN 110672494 B CN110672494 B CN 110672494B CN 201911021025 A CN201911021025 A CN 201911021025A CN 110672494 B CN110672494 B CN 110672494B
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Abstract
The invention relates to a method for measuring different porosities of porous concrete, belonging to the technical field of porosity measurement. Firstly, calculating the volume of a porous concrete sample; drying the porous concrete sample to be detected; coating wax liquid on five surfaces of the dried porous concrete sample for wax sealing, weighing, and recording the absolute dry mass M of the samplead(ii) a Placing the wax-sealed sample in a vacuumizing device, enabling the surface without wax sealing to be upward, vacuumizing, injecting liquid without air into the vacuumizing device, enabling water to cover the sample, taking out the porous concrete sample to be tested, enabling the surface without wax sealing to be upward all the time in the taking-out process, weighing, and recording as the saturated mass M of the samplesw(ii) a The liquid filled in the communicating hole was discharged again and weighed, and the mass M after the liquid discharge was recordedd(ii) a And calculating to obtain the total porosity, the effective porosity and the ineffective porosity of the porous concrete to be detected. The invention has the advantages of simple device, simple operation, short time consumption and more accurate result.
Description
Technical Field
The invention belongs to the technical field of porosity determination, and particularly relates to a method for determining different porosities of porous concrete.
Background
In recent years, along with the growing situation of urban inland inundation, governments have developed a series of sponge urban policy measures, wherein porous concrete plays a vital role in improving the rainwater retention phenomenon of the traditional hardened pavement, and the application range is wider and wider. The porous concrete is a cellular structure with uniformly distributed pores, which is prepared by taking cement as a cementing material, special graded aggregate, water and an additive according to a certain proportion and a specific process, and is often free of fine aggregate, also called as sand-free concrete.
The porosity in the porous concrete can be divided into three forms of communicated porosity, semi-communicated porosity and closed porosity according to the communication condition of the porous concrete, the sum of the three forms is total porosity, and the porosity is divided into two forms of ineffective porosity and effective porosity according to the effective use condition. Wherein the closed pores cannot play a drainage role due to the isolated and disconnected characteristics, so the closed pores are called as ineffective pores; the communicated pores have better water permeability and drainage performance and are effective pores; the semi-communicated pores are pores with one open end and one closed end, have certain water storage capacity although having no water permeating and draining functions, and are effective to the aspect of road surface precipitation, and are also called as effective pores.
The experimental methods for conventional porosity determination include both gravimetric and volumetric methods. The gravimetric method is to use an electronic balance to measure the porosity, respectively weigh the weight of the test piece after being dried and the weight in water, the difference between the two is the actual buoyancy force of the test piece due to the fact that the pores are filled with the water, and if the test piece is provided with no pores, the actual buoyancy force is subtracted from the theoretical buoyancy force to obtain the formula of the porosity P, and the calculation formula is P ═ 1- (m) buoyancy force2-m1) V). times.100%, wherein m1Weight (g) of the test piece in water, m2Weight (g) of the test piece after drying in an oven for 24 hours, and V is the volume of the test piece. The metering equipment used by the volume method is a Corelork vacuum seal instrument, the Corelork vacuum seal instrument is used for measuring the bulk density and the maximum apparent density of a compacted test piece, and the communication pore of the test piece is calculated according to the bulk density and the maximum apparent density, and the method comprises the following specific operation steps: (1) calculating the density rho of the vacuum-sealed test piece together with the sealing bag1(2) cutting off the sealing bag wrapped by the test piece under water, and calculating to obtain the density rho of the test piece in water2The connected pores are defined by rho1And ρ2Substituting into a formula: p ═ P (ρ)1-ρ2)/ρ2X 100% calculated.
The traditional porous concrete porosity testing method comprises a gravimetric method and a volumetric method, and the closed and partially semi-communicated pores cannot be effectively distinguished, so that the effective porosity testing result is larger; the traditional porous concrete porosity testing method is carried out under normal pressure, and the exhaust process is long, so that the testing time is 4-5 h; the traditional porous concrete porosity testing method cannot measure the distribution of different porosities; in the traditional porous concrete porosity testing method, because the saturated water absorption sample can flow out and lose absorbed water in the gap in the sample moving and testing processes, experimental errors are caused. Although the result of the porosity analyzed by the porous concrete CT (computed tomography) image processing technology is accurate, the instrument is expensive, the cost is high, the testing time is long, at least 10 hours are needed, and the testing time is longer for a large sample.
The Chinese invention patent (publication No. CN106442259A) discloses a method and a device for rapidly determining the effective porosity of ecological porous concrete, wherein the effective pore volume of the ecological porous concrete is equivalently replaced by the volume of injected water. Water is slowly extruded into the test mould through the extruding and pushing device, and when the water level in the test mould is level with the top of the test mould, the volume of the water in the test mould is the effective pore volume of the concrete. In the method, water is drained under the conditions of normal temperature and normal pressure, residual air in the sample is ignored, and water is not completely drained.
The Chinese invention patent (publication No. CN103940721A) discloses a method for rapidly measuring the porosity of a freshly mixed porous concrete material, and the method can detect the porosity of pervious concrete in a mixing site by a mode of vacuumizing and then injecting water. But the method ignores the test error caused by the dissolved gas of the injected water, and only stays at the monitoring of the full porosity.
The Chinese invention patent (publication No. CN108627442A) discloses a porous concrete porosity rapid testing device. According to the method, after the sample is drained, buoyancy data are measured, and then the porosity is obtained. The method adopts an ultrasonic vibration device to quickly discharge bubbles in a test block through vibration.
In recent years, in the field of research on concrete pore structures, an image processing method has shown unique advantages, the image analysis method is a method for obtaining porosity by technical analysis and extraction of a mathematical model combined with image processing, and chinese invention patent (publication No. CN205280548U) discloses a method for calculating porosity and characterizing porosity of porous concrete, and a CT scanning two-dimensional tomographic image is analyzed by the image processing method to obtain pore structure parameters such as planar porosity, effective pore diameter and pore diameter distribution of porous concrete, and the method comprises the following steps: (1) acquiring a porous concrete continuous section image; (2) standardizing the continuous sectional images; (3) rebuilding a porous concrete model; (4) calculating porosity; (5) characterizing the pore characteristic parameter. Although the image processing method can acquire the pore structure parameters more accurately and comprehensively, the method has higher requirements on a testing instrument and data processing, and has complex process, high cost and long time.
In conclusion, the existing traditional experimental methods (weight method and volume method) and some novel testing devices neglect the existence of closed pores, and the tested porosity is too single; although the image processing method can accurately obtain abundant pore structure parameters, the test price is high, the operation is complex, and the technical requirement is high, so that the image processing method is difficult to popularize in practical engineering application.
Disclosure of Invention
The invention solves the technical problems of inaccurate result, single tested porosity and complex operation in the determination process of the porosity of the porous concrete in the prior art. In order to overcome the defects of the prior art, the invention provides a method for efficiently and accurately measuring the pore structure parameters of the porous concrete. By the method, the pore structure parameters such as the full porosity, the effective porosity, the ineffective porosity and the like of the porous concrete can be simply, quickly and accurately detected.
According to the purpose of the invention, the method for rapidly determining the full porosity of the porous concrete comprises the following steps:
(1) multiplying the length, the width and the height of a cubic porous concrete sample to be measured to obtain the volume V of the porous concrete sampleT；
(2) Drying the porous concrete sample to be detected, and removing water in the sample;
(3) coating wax liquid on five surfaces of the dried porous concrete sample obtained in the step (2), sealing with wax, weighing, and recording as the oven-dry mass M of the samplead；
(4) Putting the sample subjected to wax sealing in the step (3) into a vacuumizing device, enabling the surface without wax sealing to be upward, vacuumizing, injecting liquid without air into the vacuumizing device, and enabling the liquid to cover the sample, wherein the density of the liquid without air is rhow(ii) a After soaking, taking out the porous concrete sample to be measured, enabling the surface which is not wax-sealed to be upward all the time in the taking-out process to prevent liquid in pores from leaking out, weighing, and recording as the saturated mass M of the samplesw；
(5) Calculation of the Total porosity PTThe calculation formula is as follows:
according to another aspect of the present invention, there is provided a method for rapidly determining the ineffective porosity of porous concrete, comprising the steps of:
(1) multiplying the length, the width and the height of a cubic porous concrete sample to be measured to obtain the volume V of the porous concrete sampleT；
(2) Drying the porous concrete sample to be detected, and removing water in the sample;
(3) coating wax liquid on five surfaces of the dried porous concrete sample obtained in the step (2), sealing with wax, weighing, and recording as the oven-dry mass M of the samplead；
(4) Putting the sample subjected to wax sealing in the step (3) into a vacuumizing device, enabling the surface without wax sealing to be upward, vacuumizing, injecting liquid without air into the vacuumizing device, and enabling the liquid to cover the sample, wherein the density of the liquid without air is rhow(ii) a After soaking, taking out the porous concrete sample to be tested;
(5) the liquid filled in the communicating holes in the sample is discharged from the sample by the self-gravity with the non-wax-sealed surface of the porous concrete sample with the liquid filled in the pores facing downward, and then the sample is weighed and the weight M is recorded as the mass M after the liquid is discharged from the sampled；
(6) Calculating the ineffective porosity PIThe calculation formula is as follows:
according to another aspect of the present invention, there is provided a method for rapidly determining the effective porosity of porous concrete, comprising the steps of:
(1) multiplying the length, the width and the height of a cubic porous concrete sample to be measured to obtain the volume V of the porous concrete sampleT；
(2) Drying the porous concrete sample to be detected, and removing water in the sample;
(3) drying the obtained product in the step (2)Five surfaces of the dried porous concrete sample are coated with wax liquid for wax sealing, and the weight is recorded as the absolute dry mass M of the samplead；
(4) Putting the sample subjected to wax sealing in the step (3) into a vacuumizing device, enabling the surface without wax sealing to be upward, vacuumizing, injecting liquid without air into the vacuumizing device, and enabling the liquid to cover the sample, wherein the density of the liquid without air is rhow(ii) a After soaking, taking out the porous concrete sample to be measured, enabling the surface which is not wax-sealed to be upward all the time in the taking-out process to prevent liquid in pores from leaking out, weighing, and recording as the saturated mass M of the samplesw；
(5) The liquid filled in the communicating holes in the sample is discharged from the sample by the self-gravity with the non-wax-sealed surface of the porous concrete sample with the liquid filled in the pores facing downward, and then the sample is weighed and the weight M is recorded as the mass M after the liquid is discharged from the sampled；
(6) Calculating the effective porosity Pv by the following formula:
preferably, the drying temperature in the step (2) is 100-120 ℃, and the drying time is 20-30 h.
Preferably, the soaking time in the step (4) is 20min-30 min; and (4) the liquid level in the step (4) is 3-5cm higher than the sample.
Preferably, the volume V of the porous concrete sampleTGreater than or equal to 50cm3。
Preferably, when the thickness of the porous concrete sample is less than 50mm, the water drainage time in the step (5) is 10min-15 min; when the thickness of the porous concrete sample is 50mm-100mm, the drainage time is 20min-27 min; and when the thickness of the porous concrete sample is 100mm-150mm, the drainage time is 30min-40 min.
Preferably, after the vacuum is drawn in the step (4), the pressure in the vacuum-drawing device is 90kPa to 95 kPa.
Preferably, the porous concrete sample is portland cement.
Preferably, the liquid containing no air is water containing no air.
Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
(1) the invention aims at the porous concrete porosity testing method and adds the procedures of wax sealing and vacuumizing. The vacuumizing can discharge the gas in the test block as much as possible through the pressure difference between the inside and the outside of the test sample, and can fill water quickly, so that the problem that closed pores and part of semi-communicated pores are neglected due to incomplete gas discharge is solved, the test time is effectively saved, and the common test time can be finished within 1 h; the wax seal can avoid the loss of water filled in pores of the saturated sample in the moving and testing processes, so that the saturated quality of the sample is more accurate. Through sample verification, the accuracy error of the porosity result analyzed by the method and the CT image processing technology is +/-1.5%. In a word, the invention has the advantages of simple device, simple operation, short time consumption and more accurate result.
(2) Aiming at the problem that closed pores and part of semi-communicated pores are neglected in the measurement of the porosity of the porous concrete by the conventional experimental method, the invention introduces vacuumizing and air-free water for improvement, and can effectively solve the problem.
(3) The invention solves the problems of residual air in a sample, residual air in water and incomplete drainage in the traditional test method by vacuumizing and using airless water. The invention can simultaneously detect various porosities such as full porosity, effective porosity and ineffective porosity through the added procedures of wax sealing, water drainage and the like. Compared with the existing testing method, the vacuum pumping can lead water molecules to penetrate through the thinner calcium silicate hydrate mineral component by virtue of the advantage of pressure difference and enter and fill ineffective closed pores.
(4) The device is simple and easy to obtain, and can be used after simple assembly; the operation is simple, and the test flow is simple and easy to learn; the time consumption is short, the vacuumizing process greatly shortens the testing time, and the main body test can be completed within 1 h.
Drawings
Fig. 1 is a drawing of a porous concrete vacuum-pumping device, in which: 1-water tank, 2-water without air, 3-vacuum device cylinder, 4-sealing cover, 5-pressure gauge, 6-vacuum pump, 7-porous concrete sample.
FIG. 2 is a process flow diagram of the present invention.
FIG. 3 is a three-dimensional model of porous concrete.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In order to achieve the purpose, the invention adopts the following technical scheme: preparing porous concrete according to the optimized formula; the whole measurement process is roughly divided into the processes of drying, wax sealing, vacuumizing, water soaking, draining and the like.
The method specifically comprises the following steps: the first step is as follows: measuring the apparent volume V of the porous concrete sample to be measuredT(ii) a The second step is that: placing a porous concrete sample to be tested in a 105 +/-1 ℃ oven for drying for 24 hours; the third step: coating other outer surfaces of the dried sample except the upper surface with wax liquid (the coating thickness is as thin as possible, and the exposed pore of the sealing surface is only needed), and weighing the oven-dried mass M of the sample at the momentad(ii) a The fourth step: and (3) placing the oven-dried sample in a vacuum device (the vacuum device is provided with a pressure gauge, and the two interfaces are an interface A and an interface B respectively), wherein the interface A is connected with an airless water tank and closed, the interface B is connected with a vacuum pump, the pressure in the cylinder is stabilized at about 95kPa by adjusting a control valve, and the cylinder is stably vacuumized for 30 min. Opening the interface A after vacuumizing, injecting the airless water into a vacuum device to enable the airless water to cover the sample, enabling the liquid level to be 3-5cm higher than the sample, soaking for 20min, wiping the surface water of the sample with a wet cloth, and weighing the saturated mass M of the watersw(ii) a The fifth step: the saturated sample is shown in the tablePlacing face down, draining water by using self gravity, weighing the mass M after draining water for 10mind。
Substituting the obtained numerical value into the following formula to obtain the corresponding porosity of the porous concrete: the total porosity is:
ineffective porosity:
effective porosity:
PV＝PT-PI
PT-full porosity (%) of the porous concrete sample;
PI-void porosity (%) of the porous concrete sample;
PV-effective porosity (%) of the porous concrete sample;
Mad-oven dry mass (g) of porous concrete samples;
Msw-porous concrete sample saturation mass (g);
Md-mass after drainage (g) of the porous concrete sample;
ρwdensity of airless water (g/cm)3)；
VTAppearance volume (cm) of porous concrete sample3)。
The parameters of the porous concrete material and the testing system used in the invention are as follows:
(1) the cement used in the cellular concrete was 42.5 portland cement.
(2) The particle size of the stones used in the porous concrete is in the range of 2-5 mm.
(3) The length, height and width of the tested test piece are 40 +/-0.5 mm multiplied by 40 +/-0.5 mm, and the volume of the tested sample is not less than 50cm3。
(4) The water used in the test was airless water. The airless water can be freshly prepared distilled water, otherwise the water tank is subjected to air exhaust treatment before the test (the water is filled into a water container and placed in a vacuum extractor, and the vacuum extractor is slowly vacuumized to a vacuum degree of 90-95kPa until no air bubbles emerge from the air suction bottle).
The following describes the method for testing the porosity of porous concrete in detail with reference to the schematic diagram.
Example 1
And preparing a porous concrete sample to be detected. The preparation process is approximately as follows: the raw materials are 42.5 ordinary portland cement and stones with the particle size range of 2-5mm, a certain raw material mixing ratio and a certain water cement ratio are set, the raw materials are mixed, stirred and injected into a 40mm multiplied by 40mm mould, then the mould is placed on an oscillating table, a certain oscillating frequency and oscillating time are set, the mould is oscillated and formed, and after demoulding, the mould is maintained under certain conditions.
And (4) wax sealing the porous concrete sample. The specific wax sealing process is as follows: the paraffin and the rosin are prepared into a paraffin liquid with certain viscosity according to a certain proportion, and the paraffin liquid is lightly smeared on the side surfaces and the surface layers of the bottom surfaces of the porous concrete, so that the main purpose is to fill and seal the surface pores of the side surfaces and the bottom surfaces.
FIG. 1 shows a vacuum-pumping apparatus. The water tank 1 is filled with water 2 without air, the water tank 1 is connected with an interface A on a sealing cover 4 of a vacuum device cylinder 3, an interface B on the sealing cover 4 of the vacuum device cylinder 3 is connected with a vacuum pump 6, a pressure gauge 5 is connected on the sealing cover 4, a porous concrete sample 7 is positioned on the lower surface of the vacuum device cylinder 3, and the surface of the porous concrete sample 7 which is not wax-sealed is upward.
Fig. 2 is a test flow chart of the present invention, and the specific operation process is as follows:
(1) the first step is as follows: measuring the external dimension of the porous concrete sample to be measured by using a vernier caliper and calculating the volume V of the porous concrete sampleT：52.325cm3. The precision of the vernier caliper is 0.02 mm.
(2) The second step is that: and (3) drying the porous concrete sample to be detected in a drying oven at 105 +/-1 ℃ for 24 h.
(3) The third step: the dried sample except for the upper surface,coating other outer surfaces with wax liquid (the coating thickness is as thin as possible, only the exposed pore on the sealing surface is needed), and weighing the oven-dry mass M of the sample at the momentad：100.83g。
(4) The fourth step: and (3) placing the absolutely dry sample in a vacuum device (the vacuum device is provided with a pressure gauge, and the two interfaces are interface A and interface B respectively), wherein the interface A is connected with and closed to the airless water tank, the interface B is connected with a vacuum pump, the pressure in the cylinder is stabilized at about 95kPa by adjusting a control valve until no bubble emerges from the air suction bottle, and the sample is stably vacuumized for 30 min. Opening the interface A after vacuumizing, injecting the airless water into a vacuum device to enable the airless water to cover the sample, enabling the liquid level to be 3-5cm higher than the sample, soaking for 20min, wiping the surface water of the sample with a wet cloth, and weighing the saturated mass M of the watersw：113.84g。
(5) The fifth step: placing the saturated sample with its upper surface facing downwards, draining water by using its own gravity, and weighing the mass M after draining water for 10mind：103.51g；
The precision of an electronic scale for measuring the oven dry mass, the saturated mass and the mass after water discharge of the porous concrete sample was 0.01 g.
Substituting the obtained numerical value into the following formula to obtain the corresponding porosity of the porous concrete; the total porosity is:
ineffective porosity:
effective porosity:
PV＝PT-PI
PT-full porosity (%) of the porous concrete sample;
PI-void porosity (%) of the porous concrete sample;
PV-effective pore of porous concrete sampleA porosity (%);
Mad-oven dry mass (g) of porous concrete samples;
Msw-porous concrete sample saturation mass (g);
Md-mass after drainage (g) of the porous concrete sample;
ρwdensity of airless water (g/cm)3)；
VTAppearance volume (cm) of porous concrete sample3)。
The total porosity of the sample was calculated to be 24.8%, the effective porosity 19.8%, and the ineffective porosity 5.0%.
FIG. 3 is a three-dimensional model diagram of porous concrete for image analysis, comparing the test results of the present invention with the image analysis test results.
Experiments prove that the porosity measured by the method is slightly increased compared with the porosity measured by the traditional experimental method, but is closer to the porosity result analyzed by the CT image processing technology, and the difference is within +/-1.5%. The results of the different tests are shown in Table 1. In more detail, compared with the porosity results analyzed by the CT image processing technology, the error of the test results of the determination method of the invention on various porosities of the porous concrete can be kept within +/-1.5%, and the comparison results are shown in Table 2. Fully shows that the porosity measured by the method is closer to an accurate value, and meanwhile, the method has the advantages of simple device, simple and convenient operation, short testing time and the like.
TABLE 1 comparison of the results of the tests on the total porosity of cellular concrete according to the different methods (%)
TABLE 2 comparison of the results of various porosity tests on porous concrete according to different methods (%)
Example 2
And preparing a porous concrete sample to be detected. The preparation process is approximately as follows: the raw materials are 42.5 ordinary portland cement and stones with the particle size range of 2-5mm, a certain raw material mixing ratio and a certain water cement ratio are set, the raw materials are mixed, stirred and injected into a 60mm multiplied by 60mm mould, then the mould is placed on an oscillating table, a certain oscillating frequency and oscillating time are set, the mould is oscillated and formed, and after demoulding, the mould is maintained under certain conditions.
And (4) wax sealing the porous concrete sample. The specific wax sealing process is as follows: the paraffin and the rosin are prepared into a paraffin liquid with certain viscosity according to a certain proportion, and the paraffin liquid is lightly smeared on the side surfaces and the surface layers of the bottom surfaces of the porous concrete, so that the main purpose is to fill and seal the surface pores of the side surfaces and the bottom surfaces.
FIG. 1 shows a vacuum-pumping apparatus. The water tank 1 is filled with water 2 without air, the water tank 1 is connected with an interface A on a sealing cover 4 of a vacuum device cylinder 3, an interface B on the sealing cover 4 of the vacuum device cylinder 3 is connected with a vacuum pump 6, a pressure gauge 5 is connected on the sealing cover 4, a porous concrete sample 7 is positioned on the lower surface of the vacuum device cylinder 3, and the surface of the porous concrete sample 7 which is not wax-sealed faces upwards.
Fig. 2 is a test flow chart of the present invention, and the specific operation process is as follows:
(1) the first step is as follows: measuring the external dimension of the porous concrete sample to be measured by using a vernier caliper and calculating the volume V of the porous concrete sampleT：183.137cm3. The precision of the vernier caliper is 0.02 mm.
(2) The second step is that: and (3) drying the porous concrete sample to be detected in an oven at 105 +/-1 ℃ for 24 hours.
(3) The third step: coating the outer surfaces of the dried sample except the upper surface with wax liquid (prepared from paraffin and rosin according to a certain mass ratio) (the coating thickness is as thin as possible, and the exposed pores on the surface are sealed), and weighing the oven-dried mass M of the samplead：342.72g。
(4) The fourth step: placing the oven-dried sample in a vacuum device (the vacuum device is provided with a pressure gauge, two interfaces are interface A and interface B respectively), wherein interface A is connected with an airless water tank and closed, interface B is connected with a vacuum pump, and the vacuum device is controlled by adjusting a control valveThe pressure in the cylinder is stabilized at about 95kPa until no bubble emerges from the air suction bottle, and the vacuum is stably pumped for 30 min. Opening the interface A after vacuumizing, injecting the airless water into a vacuum device to enable the airless water to cover the sample, enabling the liquid level to be 3-5cm higher than the sample, soaking for 20min, wiping the surface water of the sample with a wet cloth, and weighing the saturated mass M of the watersw：387.83g。
(5) The fifth step: placing the saturated sample with the upper surface facing downwards, draining water by using self gravity, and weighing the mass M after draining water for 25mind：351.90g；
The precision of an electronic scale for measuring the oven dry mass, the saturated mass and the mass after water discharge of the porous concrete sample was 0.01 g.
The sample was calculated to have a total porosity of 24.6%, an effective porosity of 19.4%, and an ineffective porosity of 5.2%.
Example 3
And preparing a porous concrete sample to be detected. The preparation process is approximately as follows: the raw materials are 42.5 ordinary portland cement and stones with the particle size range of 2-5mm, a certain raw material mixing ratio and a certain water cement ratio are set, the raw materials are mixed, stirred and injected into a 130mm X130 mm mould, then the mould is placed on an oscillating table, a certain oscillating frequency and oscillating time are set, the mould is oscillated and formed, and after demoulding, the mould is maintained under certain conditions.
And (4) wax sealing the porous concrete sample. The specific wax sealing process is as follows: the paraffin and the rosin are prepared into a paraffin liquid with certain viscosity according to a certain proportion, and the paraffin liquid is lightly smeared on the side surfaces and the surface layers of the bottom surfaces of the porous concrete, so that the main purpose is to fill and seal the surface pores of the side surfaces and the bottom surfaces.
FIG. 1 shows a vacuum-pumping apparatus. The water tank 1 is filled with water 2 without air, the water tank 1 is connected with an interface A on a sealing cover 4 of a vacuum device cylinder 3, an interface B on the sealing cover 4 of the vacuum device cylinder 3 is connected with a vacuum pump 6, a pressure gauge 5 is connected on the sealing cover 4, a porous concrete sample 7 is positioned on the lower surface of the vacuum device cylinder 3, and the surface of the porous concrete sample 7 which is not wax-sealed is upward.
Fig. 2 is a test flow chart of the present invention, and the specific operation process is as follows:
(1) the first step is as follows: using a cursorThe caliper measures the external dimension of the porous concrete sample to be measured and calculates the volume V thereofT：1805.213cm3. The precision of the vernier caliper is 0.02 mm.
(2) The second step is that: and (3) drying the porous concrete sample to be detected in a drying oven at 105 +/-1 ℃ for 24 h.
(3) The third step: coating the outer surfaces of the dried sample except the upper surface with wax liquid (prepared from paraffin and rosin according to a certain mass ratio) (the coating thickness is as thin as possible, and the exposed pores on the surface are sealed), and weighing the oven-dried mass M of the samplead：3462.48g。
(4) The fourth step: and (3) placing the oven-dried sample in a vacuum device (the vacuum device is provided with a pressure gauge, and the two interfaces are an interface A and an interface B respectively), wherein the interface A is connected with the airless water tank and closed, the interface B is connected with a vacuum pump, the pressure in the cylinder is stabilized at about 95kPa by adjusting a control valve until no bubble emerges from the air suction bottle, and the air suction bottle is stably vacuumized for 30 min. Opening the interface A after vacuumizing, injecting the airless water into a vacuum device to enable the airless water to cover the sample, enabling the liquid level to be 3-5cm higher than the sample, soaking for 20min, wiping the surface water of the sample with a wet cloth, and weighing the saturated mass M of the watersw：3905.62g。
(5) The fifth step: placing the saturated sample with its upper surface facing downwards, draining water by using its own gravity, draining water for 35min, and weighing the mass M after drainingd：3560.43g；
The precision of an electronic scale for measuring the oven dry mass, the saturated mass and the mass after water discharge of the porous concrete sample was 0.01 g.
The sample was calculated to have a total porosity of 24.5%, an effective porosity of 19.4%, and an ineffective porosity of 5.1%.
The method for measuring porosity of porous concrete and the system for testing the same are described in detail, and the structural principle and the embodiments of the present invention are illustrated by the specific examples, and it is easily understood by those skilled in the art that the above description is only a preferred example of the present invention and is not intended to limit the present invention, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method for rapidly measuring the full porosity of porous concrete is characterized by comprising the following steps:
(1) multiplying the length, the width and the height of a cubic porous concrete sample to be measured to obtain the volume V of the porous concrete sampleT；
(2) Drying the porous concrete sample to be detected, and removing water in the sample;
(3) coating wax liquid on five surfaces of the dried porous concrete sample obtained in the step (2), sealing with wax, weighing, and recording as the oven-dry mass M of the samplead；
(4) Putting the sample subjected to wax sealing in the step (3) into a vacuumizing device, enabling the surface without wax sealing to be upward, vacuumizing, injecting liquid without air into the vacuumizing device, and enabling the liquid to cover the sample, wherein the density of the liquid without air is rhow(ii) a After soaking, taking out the porous concrete sample to be measured, enabling the surface which is not wax-sealed to face upwards all the time in the taking-out process so as to prevent liquid in pores from leaking out, weighing, and recording as the saturated mass M of the samplesw；
(5) Calculation of the Total porosity PTThe calculation formula is as follows:
2. a method for rapidly determining the ineffective porosity of porous concrete is characterized by comprising the following steps:
(1) multiplying the length, the width and the height of a cubic porous concrete sample to be measured to obtain the volume V of the porous concrete sampleT；
(2) Drying the porous concrete sample to be detected, and removing moisture in the sample;
(3) coating wax liquid on five surfaces of the dried porous concrete sample obtained in the step (2), sealing with wax, weighing, and recordingMass M for sample oven dryingad；
(4) Putting the sample subjected to wax sealing in the step (3) into a vacuumizing device, enabling the surface without wax sealing to be upward, vacuumizing, injecting liquid without air into the vacuumizing device, and enabling the liquid to cover the sample, wherein the density of the liquid without air is rhow(ii) a After soaking, taking out the porous concrete sample to be tested;
(5) the liquid filled in the communicating holes in the sample is discharged from the sample by the self-gravity with the non-wax-sealed surface of the porous concrete sample with the liquid filled in the pores facing downward, and then the sample is weighed to obtain the mass M after the liquid is discharged from the sampled；
(6) Calculating the ineffective porosity PIThe calculation formula is as follows:
3. a method for rapidly measuring the effective porosity of porous concrete is characterized by comprising the following steps:
(1) multiplying the length, the width and the height of a cubic porous concrete sample to be measured to obtain the volume V of the porous concrete sampleT；
(2) Drying the porous concrete sample to be detected, and removing water in the sample;
(3) coating wax liquid on five surfaces of the dried porous concrete sample obtained in the step (2), sealing with wax, weighing, and recording as the oven-dry mass M of the samplead；
(4) Putting the sample subjected to wax sealing in the step (3) into a vacuumizing device, enabling the surface without wax sealing to be upward, vacuumizing, injecting liquid without air into the vacuumizing device, and enabling the liquid to cover the sample, wherein the density of the liquid without air is rhow(ii) a After soaking, taking out the porous concrete sample to be measured, enabling the surface which is not wax-sealed to be upward all the time in the taking-out process to prevent liquid in pores from leaking out, weighing, and recording as the saturated mass M of the samplesw；
(5) Will holeThe liquid filled in the communicating holes in the sample is discharged from the sample by its own weight with the non-wax-sealed surface of the porous concrete sample filled with the liquid in the gap facing downward, and then weighed to be recorded as the mass M after the sample is dischargedd；
(6) Calculating the effective porosity Pv by the following formula:
4. the method according to any one of claims 1 to 3, wherein the drying in step (2) is carried out at a temperature of 100 ℃ to 120 ℃ for a time of 20 hours to 30 hours.
5. The assay method according to any one of claims 1 to 3, wherein the soaking time in step (4) is 20min to 30 min; and (4) the liquid level in the step (4) is 3-5cm higher than the sample.
6. The method according to any one of claims 1 to 3, wherein the volume V of the porous concrete sampleTGreater than or equal to 50cm3。
7. The measuring method according to claim 2 or 3, wherein when the thickness of the porous concrete sample is less than 50mm, the water discharge time in the step (5) is 10min to 15 min; when the thickness of the porous concrete sample is 50mm-100mm, the drainage time is 20min-27 min; and when the thickness of the porous concrete sample is 100mm-150mm, the drainage time is 30min-40 min.
8. The measuring method according to any one of claims 1 to 3, wherein the pressure in the vacuum-pumping means after the vacuum-pumping in step (4) is 90kPa to 95 kPa.
9. The method according to any one of claims 1 to 3, wherein the porous concrete sample is portland cement.
10. The assay of any one of claims 1 to 3 wherein the non-air containing liquid is non-air containing water.
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| CN112147054B (en) * | 2020-09-25 | 2023-02-28 | 青岛路桥建设集团有限公司 | Rapid test method for matrix communication porosity of semi-flexible pavement |
| CN113740227A (en) * | 2021-08-26 | 2021-12-03 | 中国科学院西北生态环境资源研究院 | Survey device that soil macroporosity flows |
| CN114112861A (en) * | 2021-12-21 | 2022-03-01 | 广东石油化工学院 | Method and device for measuring porosity of ionic rare earth ore |
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