WO2018045593A1 - 一种水泥基材料干燥深度测试方法 - Google Patents

一种水泥基材料干燥深度测试方法 Download PDF

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WO2018045593A1
WO2018045593A1 PCT/CN2016/098752 CN2016098752W WO2018045593A1 WO 2018045593 A1 WO2018045593 A1 WO 2018045593A1 CN 2016098752 W CN2016098752 W CN 2016098752W WO 2018045593 A1 WO2018045593 A1 WO 2018045593A1
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cement
based material
drying
depth
material sample
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PCT/CN2016/098752
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English (en)
French (fr)
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孙红芳
邢锋
李大望
任志丽
刘剑
范冰
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深圳大学
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Priority to PCT/CN2016/098752 priority Critical patent/WO2018045593A1/zh
Priority to US15/867,680 priority patent/US10816535B2/en
Publication of WO2018045593A1 publication Critical patent/WO2018045593A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/38—Concrete; ceramics; glass; bricks
    • G01N33/383—Concrete, cement
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/02—Granular materials, e.g. microballoons
    • C04B14/04—Silica-rich materials; Silicates
    • C04B14/06—Quartz; Sand
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • C04B40/0003—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability making use of electric or wave energy or particle radiation
    • C04B40/0007—Electric, magnetic or electromagnetic fields
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/30—Staining; Impregnating ; Fixation; Dehydration; Multistep processes for preparing samples of tissue, cell or nucleic acid material and the like for analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/026—Dielectric impedance spectroscopy
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/121—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid for determining moisture content, e.g. humidity, of the fluid

Definitions

  • the invention belongs to the field of material determination or analysis, and in particular relates to a method for testing the drying depth of cement-based materials.
  • Cement-based materials include cement paste, cement mortar, cement concrete and reinforced concrete and their products; due to the excellent performance of cement-based materials, cheap and easy to obtain, it is widely used in engineering. Due to the use of the environment, the cement-based material is mostly dried from the outside to the inside after molding, and the degree of drying and depth have an important influence on its performance. For example, when the surface is dried, it causes cracking, peeling, and the like on the surface, thereby affecting structural durability. Therefore, it is of great significance to study the drying depth of cement-based materials.
  • the technical problem to be solved by the present invention is to provide a cement-based material drying depth testing method, which aims to test the drying depth of cement-based materials while considering the influence of the resistivity change on the mathematical model.
  • the present invention is achieved by a cement-based material drying depth testing method comprising the following steps:
  • the determining the impedance spectrum test mathematical model comprises: starting the cement-based material sample from the outer surface, and dividing into an electrode wetted zone, an unwet dry zone, and a non-drying affected zone, wherein the electrode wet zone and The unwet drying zone is collectively referred to as a drying affected zone; the drying effect is divided into n parts, in which the first k parts are electrode wetted zones, denoted by 1, k+1 to n parts are unwet drying zone, indicated by 2, the unaffected zone is represented by ⁇ ; t i represents the dry depth of the i-th part of the cement-based material sample, and t 2 represents the cement-based material sample The dry depth affected by the drying zone; ⁇ represents the physical quantity that determines the rate of change of resistivity;
  • the resistivity of the resistivity of the cement comprises an outer surface of the base material specimens ⁇ 0, dried resistivity were not affected area ⁇ ⁇ , wet electrode resistivity region t i at the i-th parts in dry depth ⁇ 1 ( t) and the resistivity ⁇ 2 (t) of the i-th portion at the drying depth t i of the unsoaked drying zone;
  • Z is the frequency-dependent impedance
  • ⁇ 0 is the vacuum dielectric constant
  • ⁇ is the relative dielectric constant
  • ⁇ is the pi
  • S is the cross-sectional area of the cement-based material sample
  • l is the cement-based material The length of the sample
  • j is an imaginary unit.
  • the preparing a cement-based material sample comprises:
  • the mass ratio of cement to sand is 1:1, and a cubic cement-based material sample with a size of 30 ⁇ 30 ⁇ 30 mm 3 is prepared, and the cement-based material sample is placed at a temperature of 20 ⁇ 2° C. Under the condition of humidity >95%, it is cured for a period of time to prepare a cement-based material sample.
  • the sand is an ISO standard sand.
  • the period of time includes 7 days, 14 days or 28 days.
  • drying the cement-based material sample comprises:
  • the four sides of the cement-based material sample were coated with paraffin and dried at a constant temperature of 50 ° C for 1 h, 4 h, 24 h or 48 h, and then placed in an electrode for electrochemical impedance spectroscopy.
  • drying the cement-based material sample comprises:
  • Alcohol pretreatment drying After immersing the cement-based material sample in alcohol for 24 hours, replacing the alcohol and soaking for 24 hours, the cement hydration is stopped; the four sides of the cement-based material sample are coated with paraffin, and then The mixture was baked at a constant temperature of 50 ° C for 1 h, 4 h, 24 h or 48 h, and then subjected to electrochemical impedance spectroscopy.
  • the electrochemical impedance spectroscopy test comprises:
  • AC signal is 10mA sinusoidal current, test frequency is 100mHz ⁇ 1MHz;
  • Test electrode prepare 30 ⁇ 30 mm 2 filter paper, and drop 1 ml of saturated calcium hydroxide solution on the filter paper, and fix the filter paper between the opposite faces of the cement-based material sample and the steel plate to form a conductive electrode, the steel plate Connect to an electrochemical workstation for testing.
  • the present invention has the beneficial effects that the cement-based material drying depth testing method provided by the embodiments of the present invention considers the influence of the resistivity change on the mathematical model, and reflects the regularity of the electrochemical parameters. Estimating the dryness of cement-based materials not only improves accuracy, but also Saves a lot of test manpower, time and cost compared to existing test methods.
  • the electrochemical impedance spectroscopy method provided by the invention can effectively characterize the microstructure of cement-based material samples, has high sensitivity, short test time and non-destructive test, and provides a fast and effective method for drying depth test of cement-based materials. .
  • FIG. 1 is a schematic structural diagram of a measuring electrode according to an embodiment of the present invention.
  • FIG. 3 is a schematic diagram showing correlation coefficients between measured data and a fitted figure of a cement-based material sample which is fitted and dried for 24 hours by different k and n values according to an embodiment of the present invention
  • FIG. 4a is a schematic view of a conventional model of a cement-based material sample provided by an embodiment of the present invention
  • FIG. 4b is a simplified schematic diagram of a conventional model
  • FIG. 5 is a schematic diagram showing a comparison of impedance curve fitting and a fitting curve of a conventional model to measurement data according to an embodiment of the present invention
  • FIG. 6 is a schematic diagram of a Nyquist spectrum and a fitting effect of a cement-based material sample after drying at different times according to an embodiment of the present invention
  • FIG. 7 is a graph showing the relationship between the resistivity and the depth of a cement-based material sample dried at different times according to an embodiment of the present invention.
  • FIG. 8 is a graph showing a drying depth of a cement-based material sample according to an embodiment of the present invention as a drying time
  • FIG. 9 is a schematic diagram of a Nyquist spectrum and a fitting result obtained by measuring the drying time of a cement-based material sample after alcohol pretreatment according to an embodiment of the present invention.
  • FIG. 10 is a graph showing the relationship between the resistivity and the depth of a cement-based material sample dried at different times after immersion in alcohol according to an embodiment of the present invention
  • FIG. 11 is a schematic view showing changes in drying depth of a cement-based material sample after alcohol soaking according to an embodiment of the present invention
  • FIG. 12 is a schematic diagram of a Nyquist spectrum and a fitting result of a cement-based material sample measured at different ages according to an embodiment of the present invention
  • FIG. 13 is a graph showing the relationship between the resistivity and the depth of a cement-based material sample of different ages according to an embodiment of the present invention
  • FIG. 14 is a schematic diagram showing the results of drying depth of samples of cement-based materials of different ages which are dried for 1 hour according to an embodiment of the present invention.
  • the invention provides a cement-based material drying depth testing method, comprising the following steps:
  • the determining the impedance spectrum test mathematical model comprises: starting the cement-based material sample from the outer surface, and dividing into an electrode wetted zone, an unwet dry zone, and a non-drying affected zone, wherein the electrode wet zone and The unwet drying zone is collectively referred to as a drying affected zone; the drying effect is divided into n parts, in which the first k parts are electrode wetted zones, denoted by 1, k+1 to n parts are unwet drying zone, indicated by 2, the unaffected zone is represented by ⁇ ; t i represents the dry depth of the i-th part of the cement-based material sample, and t ⁇ represents the cement-based material sample The dry depth affected by the drying zone; ⁇ represents the physical quantity that determines the rate of change of resistivity;
  • the resistivity of the resistivity of the cement comprises an outer surface of the base material specimens ⁇ 0, dried resistivity were not affected area ⁇ ⁇ , wet electrode resistivity region t i at the i-th parts in dry depth ⁇ 1 ( t) and the resistivity ⁇ 2 (t) of the i-th portion at the drying depth t i of the unsoaked drying zone;
  • Z is the frequency-dependent impedance
  • ⁇ 0 is the vacuum dielectric constant
  • ⁇ is the relative dielectric constant
  • ⁇ is the pi
  • S is the cross-sectional area of the cement-based material sample
  • l is the cement-based material The length of the sample
  • j is an imaginary unit.
  • the drying depth testing method of the cement-based material provided by the embodiment takes into account the influence of the resistivity change on the mathematical model, and reflects and calculates the drying depth of the cement-based material by changing the regularity of the electrochemical parameters, thereby improving the accuracy. And it saves a lot of test manpower, time and cost compared to existing test methods.
  • the electrochemical impedance spectroscopy method provided by the embodiment can effectively characterize the microstructure of the cement-based material sample, has high sensitivity, short test time and no damage test, and provides a fast and effective test for drying depth of cement-based materials. method.
  • the preparing a cement-based material sample includes:
  • the mass ratio of cement to sand is 1:1, and a cubic cement-based material sample with a size of 30 ⁇ 30 ⁇ 30 mm 3 is prepared, and the cement-based material sample is placed at a temperature of 20 ⁇ 2. After curing for a period of time at °C, humidity >95%, a sample of cement-based material was obtained.
  • the cement is produced by China Resources P.O.42.5 grade ordinary Portland cement and China Resources Cement (Kaifeng) Co., Ltd.
  • the water is deionized water.
  • the sand is ISO standard sand and is produced by Xiamen Ai Siou Standard Sand Co., Ltd.
  • drying the sample of the cement-based material may be:
  • the four sides of the cement-based material sample were coated with paraffin to ensure that the resistivity was changed in a single direction, and dried at a constant temperature of 50 ° C for 1 h, 4 h, 24 h, and 48 h, respectively, and then placed in an electrode for testing.
  • the sample of the cement-based material is dried, or may be pre-treated by alcohol:
  • the cement-based material sample After the cement-based material sample is immersed in alcohol for 24 hours, the cement is hydrated by replacing the alcohol for another 24 hours; the four sides of the cement-based material sample are coated with paraffin, and then kept at a constant temperature of 50 ° C.
  • the tubes were baked for 1 h, 4 h, 24 h, and 48 h, respectively, and then subjected to electrochemical impedance spectroscopy.
  • the period of time may be 7 days, 14 days, or 28 days.
  • the variation of the drying depth of the cement mortar test block at the same time in different ages can be studied.
  • the electrochemical impedance spectroscopy test includes:
  • AC signal is 10mA sinusoidal current, test frequency is 100mHz ⁇ 1MHz;
  • Test electrode prepare 30 ⁇ 30 mm 2 filter paper, and drop 1 ml of saturated calcium hydroxide solution on the filter paper. Referring to FIG. 1 , the filter paper 1 with the saturated calcium hydroxide solution is fixed on the cement-based material sample 2 A conductive electrode 10 is formed between the opposite faces and the steel plate 3, and the steel plate 3 is connected to an electrochemical workstation for testing.
  • the impedance spectrum test results are shown in Fig. 2.
  • a straight line portion is observed at the low frequency end, as shown in Figure 2, the bc segment is mainly due to the contact surface resistance of the electrode and the cement-based material sample and the double-layer capacitance, which is not the information of the sample itself.
  • a pseudo-anti-arc was observed in the low frequency band (de segment in Fig. 2) due to the influence of electrode contact.
  • the portion below 1 kHz is ignored, and only the portion of the 1 kHz-1 MHz band reflecting the sample information is fitted.
  • the high-frequency impedance spectrum part showed more and more obvious asymmetry. This is different from the symmetrical impedance spectrum tested in water saturation, which indicates that large errors occur when fitting using conventional models.
  • the equivalent circuit can represent the model shown in Figure 4a, where R 0 , R 1 , C 1 are high frequency resistance, solid-liquid interface resistance and capacitance, respectively, R ct and C dl They are cement-electrode interface charge transfer resistors and electric double layer capacitors.
  • R 0 the literature indicates that the electrochemical impedance spectrum of the cement mortar cement substrate sample is substantially at 0 o'clock with the real axis, so R 0 can be omitted.
  • the accuracy of the test mathematical model was verified by taking the impedance spectrum of the sample directly dried for 24 hours as an example.
  • the fitting curve of the test mathematical model is compared with the fitting curve of the conventional model, and the result is shown in FIG. 5.
  • the main components of the cement-based material sample include cement gel, aggregate and pore solution, wherein the cement gel and aggregate are insulators, and the cement mortar is electrically conductive through the pore solution. It can be clearly seen from FIG. 5 that the test mathematical model can accurately fit the asymmetry of the impedance spectrum, and the fitting effect far exceeds the fitting effect of the traditional model. Therefore, it can be explained that the test mathematical model provided by the embodiment has a good fitting effect on the impedance spectrum formed due to the change in resistivity caused by external drying.
  • the drying includes direct drying and alcohol pretreatment drying.
  • Table 1 shows the parameters obtained by model fitting after drying the cement substrate samples for different times, and the correlation coefficients in Table 1 are close to 1. It can be seen that the kn model has a good fitting effect at each drying time (correlation coefficient is shown in Table 1). In addition, the values of ⁇ ⁇ , ⁇ t1 and t 2 were extracted and listed in Table 1, and the resistivity ⁇ was varied with the depth of the cement substrate sample as shown in Fig. 7. The drying depth t 2 was plotted with the drying time. As shown in Figure 8.
  • the ⁇ ⁇ value resistivity not affected by the dried portion
  • the ⁇ t1 value represents the maximum value of the resistivity distribution in the entire test sample. As the drying time increases, ⁇ t1 monotonously increases, and the depth at which the maximum value ⁇ t1 appears is also deeper and deeper, indicating that the cement substrate sample is baked "dryer" and the deeper portion is affected by the drying.
  • the tendency to change with drying time is shown in Fig. 8 and Table 1. It can be seen that as the drying time increases from 1h to 48h, the drying depth increases from 0.45mm to 3.96mm, because the cement substrate sample passes more and deeper pore solution through the outside with the increase of drying time. The connected pores run out, increasing the depth of drying. However, the change in drying depth is not linear with the drying time, but is slowed as the drying time increases and the drying depth increases. This aspect is due to the tortuosity of the pore structure. As the drying depth increases, the pore water drying becomes more difficult. On the other hand, due to the evaporation of water, the pore wall undergoes slight shrinkage deformation. This makes the water more difficult to evaporate.
  • the alcohol pretreatment was dried: the samples pretreated with alcohol were dried for 1 h, 4 h, 24 h and 48 h, respectively, and the impedance spectrum measured is shown in FIG. 9 .
  • the resulting trend is similar to direct drying, but in the low frequency region, in addition to the pseudo-anti-arc, a straight line similar to that of a lower degree of dryness is observed, but this portion is also related to the electrode and therefore is not a focus of discussion.
  • the model is fitted with the model in Fig. 9.
  • the fitting curve is shown in Fig. 9. It can be seen that the fitting effect is also good.
  • Table 2 shows the parameters obtained by model fitting the samples of the alcohol-impregnated cement substrate at different times.
  • the resistivity ⁇ varies with the depth of the cement substrate sample as shown in Fig. 10.
  • the drying depth t 2 varies with the drying time. 11 is shown.
  • the cement substrate sample ⁇ ⁇ after alcohol soaking has a range of 3-7 k ⁇ *cm, which is substantially the same as the directly dried sample. It can be seen from Fig. 11 and Table 2 that as the drying time increases, the drying depth increases from 0.74 mm to 2.15 mm, and the dry depth value of the alcohol pretreatment is smaller than that of the direct drying, which is due to the alcohol pretreatment drying as much as possible. Reduced the effects of cement hydration accelerated at higher temperatures.
  • the cement mortar cement substrate samples were cured under water for 7 days, 14 days and 28 days, and then dried for 1 h.
  • the measured impedance spectrum is shown in Fig. 12.
  • the fitting results obtained by fitting this model are shown in Fig. 12.
  • Table 3 is shown. Table 3 shows the parameters obtained by model fitting of cement mortar base samples of different ages.
  • the resistivity of cement substrate samples varies with the depth of cement substrate samples as shown in Figure 13, and the drying depth changes with age. As shown in Figure 14. It can be seen from Table 3 that ⁇ ⁇ monotonically increases with increasing age, increasing from 2.03 k ⁇ *cm for 7 days to 3.96 k ⁇ *cm for 14 days and 4.17 k ⁇ *cm for 28 days.
  • the sample drying depth is from 1.74 mm in 7 days to 0.57 mm in 14 days and 0.45 mm in 28 days, and the change trend is slowing down, which is mainly related to the speed of cement hydration. related. In the early stage, the cement hydrated faster, and the density of the pores changed rapidly. The closer the age is to 28 days, the slower the hydration rate.
  • the method for testing the drying depth of cement-based materials considers the influence of the change of resistivity on the mathematical model, and reflects and estimates the drying depth of the cement-based material by changing the regularity of the electrochemical parameters, thereby not only improving the accuracy. Degree, and saves a lot of test manpower, time and cost compared to existing test methods.
  • the electrochemical impedance spectroscopy method provided by the embodiments of the invention can effectively characterize the microstructure of the cement-based material, has high sensitivity, short test time and non-destructive test, and provides a fast and effective method for drying depth test of cement-based materials. .

Abstract

一种水泥基材料干燥深度测试方法，包括以下步骤：制作水泥基材料试样；对所述水泥基材料试样进行干燥；对所述水泥基材料试样进行电化学阻抗谱测试，确定阻抗谱测试数学模型，然后确定其电阻率；确定所述水泥基材料的干燥深度测试数学模型。该水泥基材料干燥深度测试方法，考虑了电阻率变化对数学模型的影响，通过对电化学参数的规律变化来反映和推算水泥基材料的干燥深度，不仅提高了精确度，而且节省了大量的测试人力、时间和成本。

Description

一种水泥基材料干燥深度测试方法 技术领域
本发明属于材料测定或分析领域，尤其涉及一种水泥基材料干燥深度测试方法。
背景技术
水泥基材料包括水泥净浆、水泥砂浆、水泥混凝土和钢筋混凝土及其制品；由于水泥基材料性能优异、廉价易得，在工程中得以广泛应用。受使用环境作用，水泥基材料在成型后，大部分情况下都处于从外部向内部进行干燥的状态，而干燥程度及深度对其性能有重要的影响。例如，表面被干燥后，导致表面出现开裂、起皮等现象，从而影响结构耐久性。因此，对水泥基材料的干燥深度进行研究具有十分重要的意义。
然而，目前的水泥基材料干燥深度的测试方法大多为有损测试，需将水泥基材料破损后才能进行干燥深度的测试。这种测试方法比较麻烦，需要花费很多人力和时间，测试效率比较低，而且不能进行连续跟踪测试。此外，现有的采用电化学阻抗谱对水泥基材料进行的无损测试工作，并未对干燥深度进行计算，并且都将水泥基材料当做电导均匀的个体，并没有考虑水泥基材料试样内部电阻率可能发生的变化对数学模型的影响。
发明内容
本发明所要解决的技术问题在于提供一种水泥基材料干燥深度测试方法，旨在做到考虑电阻率变化对数学模型的影响的同时，对水泥基材料干燥深度进行测试。
本发明是这样实现的，一种水泥基材料干燥深度测试方法，包括以下步骤：
制作水泥基材料试样；
对所述水泥基材料试样进行干燥；
对所述水泥基材料试样进行电化学阻抗谱测试，确定阻抗谱测试数学模型，然后确定其电阻率；
确定所述水泥基材料的干燥深度测试数学模型；
所述确定阻抗谱测试数学模型包括：将所述水泥基材料试样从外表面开始，分为电极浸湿区、未浸湿干燥区及未受干燥影响区，其中所述电极浸湿区和所述未浸湿干燥区统称为受干燥影响区；将所述受干燥影响区分为n份，在这n份中，前k份为电极浸湿区，用1表示，第k+1至第n份为未浸湿干燥区，用2表示，所述未受干燥影响区用δ表示；ti表示所述水泥基材料试样第i份的干燥深度，t2表示水泥基材料试样未受干燥影响区的干燥深度；γ表示决定电阻率变化速率的物理量；
所述电阻率包括所述水泥基材料试样外表面的电阻率ρ0、未受干燥影响区的电阻率ρδ、电极浸湿区在干燥深度ti处第i份的电阻率ρ1(t)及未浸湿干燥区在干燥深度ti处第i份的电阻率ρ2(t)；
Figure PCTCN2016098752-appb-000001
Figure PCTCN2016098752-appb-000002
其中，
Figure PCTCN2016098752-appb-000003
进一步地，所述水泥基材料的干燥深度测试数学模型为
Figure PCTCN2016098752-appb-000004
其中，Z为与频率相关的阻抗，ε0为真空介电常数，ε为相对介电常数，π为圆周率，S为所述水泥基材料试样的横截面积，l为所述水泥基材料试样的长度，j为虚数单位。
进一步地，所述制作水泥基材料试样，包括：
按水灰比为0.4，水泥与砂子质量比为1:1，制成尺寸为30×30×30mm3的立方体水泥基材料试样，将所述水泥基材料试样放在温度20±2℃，湿度>95％的条件下养护一段时间，制得水泥基材料试样。
进一步地，所述砂子为ISO标准砂。
进一步地，所述一段时间包括7天、14天或28天。
进一步地，所述对所述水泥基材料试样进行干燥，包括：
将所述水泥基材料试样的四个侧面涂上石蜡，在恒温50℃条件下干燥1h、4h、24h或48h，然后放在电极中进行电化学阻抗谱测试。
进一步地，所述对所述水泥基材料试样进行干燥，包括：
酒精预处理干燥：将所述水泥基材料试样在酒精中浸泡24h后，更换酒精再浸泡24h的方式停止水泥水化；将所述水泥基材料试样的四个侧面涂上石蜡，再在恒温50℃条件下中烘1h、4h、24h或48h，然后进行电化学阻抗谱测试。
进一步地，所述电化学阻抗谱测试包括:
EIS参数设置：交流信号为10mA的正弦电流，测试频率为100mHz～1MHz；
测试电极：准备30×30mm2滤纸，并将1ml饱和氢氧化钙溶液滴在所述滤纸上，将所述滤纸固定在水泥基材料试样相对的两个面和钢板之间形成导电电极，钢板连接电化学工作站进行测试。
本发明与现有技术相比，有益效果在于：本发明实施例所提供的水泥基材料干燥深度测试方法，考虑了电阻率变化对数学模型的影响，通过对电化学参数的规律变化来反映和推算水泥基材料的干燥深度，不仅提高了精确度，而且 相比现有的测试方法，节省了大量的测试人力、时间和成本。本发明所提供的电化学阻抗谱方法可有效表征水泥基材料试样的微观结构，灵敏度高、测试时间短且是无破坏测试，为水泥基材料干燥深度测试提供了一种快速、有效的方法。
附图说明
图1是本发明实施例提供的测量电极的结构示意图；
图2是本发明实施例提供的水泥基材料试样干燥4h和24h的Nyquist谱图(奈奎斯特图)；
图3是本发明实施例提供的采用不同k、n值拟合干燥24h的水泥基材料试样的测量数据与拟合图形之间的相关系数示意图；
图4a是本发明实施例提供的水泥基材料试样的传统模型示意图，图4b是简化的传统模型示意图；
图5是本发明实施例提供的阻抗谱拟合、传统模型对测量数据的拟合曲线对比结果示意图；
图6是本发明实施例提供的水泥基材料试样干燥不同时间后测量得到的Nyquist谱图及拟合效果示意图；
图7是本发明实施例提供的干燥不同时间的水泥基材料试样的电阻率随深度的变化曲线；
图8是本发明实施例提供的水泥基材料试样的干燥深度随干燥时间的变化曲线；
图9是本发明实施例提供的酒精预处理后水泥基材料试样干燥不同时间测量得到的Nyquist谱图及拟合结果示意图；
图10是本发明实施例提供的酒精浸泡后干燥不同时间的水泥基材料试样的电阻率随深度的变化曲线；
图11是本发明实施例提供的酒精浸泡后的水泥基材料试样干燥深度随干燥时间的变化示意图；
图12是本发明实施例提供的水泥基材料试样在不同龄期测量得到的Nyquist谱图及拟合结果示意图；
图13是本发明实施例提供的不同龄期的水泥基材料试样的电阻率随深度的变化曲线；
图14是本发明实施例提供的不同龄期水泥基材料试样干燥1h的干燥深度结果示意图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明提供了一种水泥基材料干燥深度测试方法，包括以下步骤：
制作水泥基材料试样；
对所述水泥基材料试样进行干燥；
对所述水泥基材料试样进行电化学阻抗谱测试，确定阻抗谱测试数学模型，然后确定其电阻率；
确定所述水泥基材料的干燥深度测试数学模型；
所述确定阻抗谱测试数学模型包括：将所述水泥基材料试样从外表面开始，分为电极浸湿区、未浸湿干燥区及未受干燥影响区，其中所述电极浸湿区和所述未浸湿干燥区统称为受干燥影响区；将所述受干燥影响区分为n份，在这n份中，前k份为电极浸湿区，用1表示，第k+1至第n份为未浸湿干燥区，用2表示，所述未受干燥影响区用δ表示；ti表示所述水泥基材料试样第i份的干燥深度，tδ表示水泥基材料试样未受干燥影响区的干燥深度；γ表示决定电阻率变化速率的物理量；
所述电阻率包括所述水泥基材料试样外表面的电阻率ρ0、未受干燥影响区的电阻率ρδ、电极浸湿区在干燥深度ti处第i份的电阻率ρ1(t)及未浸湿干燥区在干燥深度ti处第i份的电阻率ρ2(t)；
Figure PCTCN2016098752-appb-000005
Figure PCTCN2016098752-appb-000006
其中，
Figure PCTCN2016098752-appb-000007
具体地，所述水泥基材料的干燥深度测试数学模型为
Figure PCTCN2016098752-appb-000008
其中，Z为与频率相关的阻抗，ε0为真空介电常数，ε为相对介电常数，π为圆周率，S为所述水泥基材料试样的横截面积，l为所述水泥基材料试样的长度，j为虚数单位。
本实施例所提供的水泥基材料干燥深度测试方法，考虑了电阻率变化对数学模型的影响，通过对电化学参数的规律变化来反映和推算水泥基材料的干燥深度，不仅提高了精确度，而且相比起现有的测试方法，节省了大量的测试人力、时间和成本。本实施例所提供的电化学阻抗谱方法可有效表征水泥基材料试样的微观结构，灵敏度高、测试时间短且是无破坏测试，为水泥基材料干燥深度测试提供了一种快速、有效的方法。
具体地，所述制作水泥基材料试样，包括：
按水灰比为0.4，水泥与砂子质量比为1:1，制成尺寸为30×30×30mm3的立方体水泥基材料试样，将所述水泥基材料试样放在温度为20±2℃，湿度>95％的条件下养护一段时间，制得水泥基材料试样。
其中，水泥为华润P.O.42.5级普通硅酸盐水泥，华润水泥(开封)有限公司生产。水为去离子水。所述砂子为ISO标准砂，由厦门艾思欧标准砂有限公司出品。
具体地，所述对所述水泥基材料试样进行干燥，可以是：
将所述水泥基材料试样的四个侧面涂上石蜡，以保证电阻率沿着单一方向变化，在恒温50℃条件下分别干燥1h、4h、24h、48h，然后放在电极中进行测试。
具体地，所述对所述水泥基材料试样进行干燥，也可以是酒精预处理干燥：
将所述水泥基材料试样在酒精中浸泡24h后，更换酒精再浸泡24h的方式停止水泥水化；将所述水泥基材料试样的四个侧面涂上石蜡，再在恒温50℃条件下中分别烘1h、4h、24h、48h，然后进行电化学阻抗谱测试。
具体地，所述一段时间可以为7天、14天或28天。通过对比，可研究水泥砂浆试块在不同龄期情况下干燥相同时间，其干燥深度的变化规律。
具体地，所述电化学阻抗谱测试包括:
EIS参数设置：交流信号为10mA的正弦电流，测试频率为100mHz～1MHz；
测试电极：准备30×30mm2滤纸，并将1ml饱和氢氧化钙溶液滴在所述滤纸上，参见图1，将所述滴有饱和氢氧化钙溶液的滤纸1固定在水泥基材料试样2相对的两个面和钢板3之间形成导电电极10，钢板3连接电化学工作站进行测试。
对于干燥后水泥基材料试样的阻抗谱，以干燥4h和24h的样品为例，其阻抗谱测试结果如图2所示。对于干燥4h的谱图，在低频端会观察到直线部分，如图2中的bc段，主要是由于电极与水泥基材料试样的接触面电阻和双层电容造成的，并非属于样品本身信息。而在干燥24h的阻抗谱上，在低频段观察到伪感抗弧(图2中de段)，这是由于电极接触的影响所致。因此，在进行阻抗谱分析时，将忽略掉1kHz以下的部分，只对反映了样品信息的1kHz-1MHz频段部分进行拟合。另外，我们还发现随着干燥时间的延长，高频段阻抗谱部分越来越呈现出明显的不对称性。这与处于水饱和状态下测试的对称的阻抗谱是不同的，这说明使用传统的模型进行拟合时就会出现较大的误差。
在用本实施例提供的阻抗谱测试数学模型对阻抗谱进行拟合时，需要确定k与n(分割的步长)的值，使得既能保证得到良好的拟合效果，又能尽量保证以适合有限的测量数据使所得方程解的唯一性和准确性。为了评价拟合效果，我们引入了相关系数。相关系数越接近1，表示测量数据与拟合曲线相关性越好；越接近0，表示测量数据与拟合曲线的相关性越差。以24h的阻抗谱的拟合为例，曲线相关系数与k、n取值的关系如图3所示，可以看出n取值较小时，拟合程度较差。这是由于水泥基材料试样分层不够薄，导致误差比较大。随着n值的增大，相关系数不断增大；但是当n增大到14和15时，相关系数增加的速度放缓，最高点基本上已经重合。如果n值继续增大，相关系数变化不大，但软件在拟合时误差会变大。因此，对于干燥了24h的样品，取n＝15。关于k 值的变化，可以看出，随着k值的增大，相关系数先增大后减小，当k＝4时，图形相关系数最接近1，说明其拟合程度最好，所以k取4。综上，干燥时间为24h时，用本模型对水泥基材料试样的电化学阻抗进行拟合时，取k＝4，n＝15。对于本研究中其他干燥时间处理的样品，k与n的取值将按照类似的方法确定。
对于均匀的水泥基材料试样，其等效电路可以表示图4a所示的模型，其中R0，R1，C1分别是高频电阻、固‐液界面电阻和电容，Rct和Cdl分别是水泥‐电极界面电荷转移电阻以及双电层电容。对于R0，文献表明，水泥砂浆水泥基材试样的电化学阻抗谱图基本上是与实轴相交于0点的，所以R0可以略去。对于Rct和Cdl，在Nyquist图中对应低频阻抗弧，是与电极的性质相关的物理量，当Rct足够大时，表现为一条直线。由于本文内容主要研究水泥砂浆本身的性质，因此Rct和Cdl也可以不考虑。基于此，对于本研究中的情况，图4a中的模型可以简化为图4b。
以直接干燥24h的样品的阻抗谱为例，验证所述测试数学模型的准确性。将所述测试数学模型的拟合曲线与传统模型的拟合曲线进行比较，结果如图5所示。水泥基材料试样主要组成包括是由水泥凝胶、骨料和孔溶液，其中水泥凝胶和骨料为绝缘体，而水泥砂浆通过孔溶液导电。从图5中可以明显看出，所述测试数学模型可以准确拟合出阻抗谱的不对称性，拟合效果远超传统模型的拟合效果。因此可以说明，对于由于外部干燥引起的电阻率变化而形成的阻抗谱，本实施例提供的所述测试数学模型具有较好的拟合效果。
所述干燥包括直接干燥和酒精预处理干燥。
直接干燥：对于养护28天之后的水泥基材试样，分别进行了1h、4h、24h及48h的干燥，所测得的阻抗谱如图6所示。从图6中可以看出，随着干燥时间的延长，容抗弧的半径增大，说明电阻增大，这是由于砂浆中的孔隙溶液蒸发而损失造成的。低频端的伪电感弧在干燥4h后已经开始出现了，但这部分与样品特征不相关，因此不在我们的分析范围之内。
表1为水泥基材试样干燥不同时间后用模型拟合得到的参数，对应表1中的相关系数都接近1。可见在每个干燥时间k-n模型都具有较好的拟合效果(相关系数见表1)。另外，提取出了ρδ、ρt1和t2的数值，列于表1，并得到电阻率ρ随水泥基材试样深度变化如图7所示，干燥深度t2随干燥时间的变化曲线如图8所示。
通过实验发现，即使对于同批水泥基材试样，ρδ值(未受干燥部分影响的电阻率)也存在一定差异，范围在3-5kΩ*cm之间。这主要由于水泥基材试样本身是复杂的混合物，内部成分及空隙分布未必全部均匀导致的个体差异造成的。所以基本上可以认为水泥基材试样没有被干燥的时候，水泥基材试样的阻值一般在这个范围之内。ρt1值表示的是整个测试样品中电阻率分布的最大值。随着干燥时间的增加，ρt1单调增加，出现最大值ρt1的深度也越来越深，这说明水泥基材试样被烘得“更干”，且更深的部分受到干燥的影响。
表1
Figure PCTCN2016098752-appb-000009
对于干燥深度，其随干燥时间的变化趋势如图8及表1所示。由此可见，随着干燥时间由1h增加到48h，干燥深度由0.45mm增加到3.96mm，是由于随着干燥时间的增加，水泥基材试样更多的及更深处的孔溶液通过与外界连通的孔隙跑出来，使干燥深度不断增加。但是干燥深度的变化并不是与干燥时间呈线性关系的，而是随着干燥时间的增加及干燥深度的增长在变缓。这一方面是由于孔隙结构的曲折性，随着干燥深度的增大，孔隙水干燥难度变大；另一方面是在干燥的过程中，由于水分的蒸发，使孔隙壁发生微小的收缩变形，从而使水分更难蒸发。
所述酒精预处理干燥：将酒精预处理后的样品分别干燥1h、4h、24h和48h，测得的阻抗谱图如图9所示。所得结果变化趋势与直接干燥类似，但在低频区除了伪感抗弧，还观察到类似较低干燥程度时会出现的直线，但这部分同样与电极相关，因此不作为重点讨论内容。对图9中容抗弧部分用此模型进行拟合，拟合曲线如图9所示，可见同样具有较好的拟合效果。表2为酒精浸泡水泥基材试样干燥不同时间用模型拟合得到的参数，电阻率ρ随水泥基材试样深度变化如图10所示，干燥深度t2随干燥时间的变化曲线如图11所示。
酒精浸泡后的水泥基材试样ρδ的范围在3-7kΩ*cm之间，基本上与直接干燥的样品相同。从图11和表2中可以看出，随着干燥时间的增加，干燥深度从0.74mm增加到2.15mm，且酒精预处理的干燥深度值比直接干燥的小，这是由于酒精预处理干燥尽量降低了在较高温度中加速的水泥水化的影响所导致的。
表2
Figure PCTCN2016098752-appb-000010
将水泥砂浆水泥基材试样饱水状态下养护7天、14天和28天，再干燥1h，测得的阻抗谱如图12所示，用此模型拟合得到的拟合结果如图12和表3所示。表3为不同龄期水泥砂浆水泥基材试样用模型拟合得到的参数，水泥基材试样电阻率随水泥基材试样深度的变化如图13所示，干燥深度随龄期的变化如图14所示。从表3中可以看到ρδ随着龄期的增加而单调增加，分别从7天的2.03 kΩ*cm增加到14天的3.96kΩ*cm及28天的4.17kΩ*cm。因为随着龄期的增加，水泥的水化程度不断增大，水泥砂浆的孔隙结构越来越密实。电阻率的峰值ρt1值，同样随着龄期的增加而增大，由7天的370kΩ*cm增加14天的407kΩ*cm及28天的628kΩ*cm，原因同上。
从图13中可以明显看出，随着龄期的增加，电阻率曲线越来越陡，所受影响的深度也越来越小。因为龄期较小时，水泥基材试样的水化程度较低，水泥基材试样内部的孔隙较大，水泥基材试样比较容易被干燥。而当龄期增大时，孔隙变小甚至变成闭口孔，使水泥基材试样难被干燥，只能干燥外层的孔隙水，所以干燥深度降低。
表3
Figure PCTCN2016098752-appb-000011
从图14中可以看出，经过1h的干燥，样品干燥深度从7天的1.74mm到14天的0.57mm及28天的0.45mm，其变化趋势在变缓，这主要跟水泥水化的快慢有关。在前期，水泥水化得较快，其孔隙的密实度变化得也快，而龄期越接近28天，其水化速度也就越慢。
本发明实施例所提供的水泥基材料干燥深度测试方法，考虑了电阻率变化对数学模型的影响，通过对电化学参数的规律变化来反映和推算水泥基材料的干燥深度，这样不仅提高了精确度，而且相比现有的测试方法，节省了大量的测试人力、时间和成本。本发明实施例所提供的电化学阻抗谱方法可有效表征水泥基材料的微观结构，灵敏度高，测试时间短且是无破坏测试，为水泥基材料干燥深度测试提供了一种快速、有效的方法。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (8)

  1. 一种水泥基材料干燥深度测试方法，其特征在于，包括以下步骤：
    制作水泥基材料试样；
    对所述水泥基材料试样进行干燥；
    对所述水泥基材料试样进行电化学阻抗谱测试，确定阻抗谱测试数学模型，然后确定其电阻率；
    确定所述水泥基材料的干燥深度测试数学模型；
    所述确定阻抗谱测试数学模型包括：将所述水泥基材料试样从外表面开始，分为电极浸湿区、未浸湿干燥区及未受干燥影响区，其中所述电极浸湿区和所述未浸湿干燥区统称为受干燥影响区；将所述受干燥影响区分为n份，在这n份中，前k份为电极浸湿区，用1表示，第k+1至第n份为未浸湿干燥区，用2表示，所述未受干燥影响区用δ表示；ti表示所述水泥基材料试样第i份的干燥深度，t2表示水泥基材料试样未受干燥影响区的干燥深度；γ表示决定电阻率变化速率的物理量；
    所述电阻率包括所述水泥基材料试样外表面的电阻率ρ0、未受干燥影响区的电阻率ρδ、电极浸湿区在干燥深度ti处第i份的电阻率ρ1(t)及未浸湿干燥区在干燥深度ti处第i份的电阻率ρ2(t)；
    Figure PCTCN2016098752-appb-100001
    Figure PCTCN2016098752-appb-100002
    其中，
    Figure PCTCN2016098752-appb-100003
  2. 如权利要求1所述的水泥基材料干燥深度测试方法，其特征在于，所述水泥基材料的干燥深度测试数学模型为
    Figure PCTCN2016098752-appb-100004
    其中，Z为与频率相关的阻抗，ε0为真空介电常数，ε为相对介电常数，π为圆周率，S为所述水泥基材料试样的横截面积，l为所述水泥基材料试样的长度，j为虚数单位。
  3. 如权利要求1或2所述的水泥基材料干燥深度测试方法，其特征在于，所述制作水泥基材料试样，包括：
    按水灰比为0.4，水泥与砂子质量比为1:1，制成尺寸为30×30×30mm3的立方体水泥基材料试样，将所述水泥基材料试样放在温度20±2℃，湿度>95％的条件下养护一段时间，制得水泥基材料试样。
  4. 如权利要求3所述的水泥基材料干燥深度测试方法，其特征在于，所述砂子为ISO标准砂。
  5. 如权利要求3所述的水泥基材料干燥深度测试方法，其特征在于，所述一段时间包括7天、14天或28天。
  6. 如权利要求1或2所述的水泥基材料干燥深度测试方法，其特征在于，所述对所述水泥基材料试样进行干燥，包括：
    将所述水泥基材料试样的四个侧面涂上石蜡，在恒温50℃条件下干燥1h、4h、24h或48h，然后放在电极中进行电化学阻抗谱测试。
  7. 如权利要求1或2所述的水泥基材料干燥深度测试方法，其特征在于，所述对所述水泥基材料试样进行干燥，包括：
    酒精预处理干燥：将所述水泥基材料试样在酒精中浸泡24h后，更换酒精再浸泡24h的方式停止水泥水化；将所述水泥基材料试样的四个侧面涂上石蜡，再在恒温50℃条件下中烘1h、4h、24h或48h，然后进行电化学阻抗谱测试。
  8. 如权利要求1所述的水泥基材料干燥深度测试方法，其特征在于，所述电化学阻抗谱测试包括
    EIS参数设置：交流信号为10mA的正弦电流，测试频率为100mHz～1MHz；
    测试电极：准备30×30mm2滤纸，并将1ml饱和氢氧化钙溶液滴在所述滤纸上，将所述滤纸固定在水泥基材料试样相对的两个面和钢板之间形成导电电极，钢板连接电化学工作站进行测试。
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