CN111426725B - Method and device for evaluating cement negative temperature hydration - Google Patents
Method and device for evaluating cement negative temperature hydration Download PDFInfo
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- CN111426725B CN111426725B CN202010169312.0A CN202010169312A CN111426725B CN 111426725 B CN111426725 B CN 111426725B CN 202010169312 A CN202010169312 A CN 202010169312A CN 111426725 B CN111426725 B CN 111426725B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
- G01N25/48—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on solution, sorption, or a chemical reaction not involving combustion or catalytic oxidation
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
- G01N25/48—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on solution, sorption, or a chemical reaction not involving combustion or catalytic oxidation
- G01N25/4873—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on solution, sorption, or a chemical reaction not involving combustion or catalytic oxidation for a flowing, e.g. gas sample
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Abstract
The invention mainly aims to provide a method and a device for evaluating cement negative temperature hydration. The method comprises the following steps: will test the temperature T 1 The cement is prepared into slurry; obtaining the change relation of the temperature along with the measuring time; the testing environment is kept at the testing temperature, and the heat dissipation constant between the slurry and the environment is less than or equal to 100 joules/(hour multiplied by centigrade); calculating to obtain a temperature extreme value T from the temperature change of the slurry 2 (ii) a If T is not present 2 Or (T) 2 ‑T 1 )<And if the temperature is 10 ℃, judging that the construction is not suitable for the negative temperature environment construction corresponding to the testing temperature. The method and the device can quickly and intuitively acquire the temperature change of the slurry when the cement is hydrated at the negative temperature, accurately evaluate whether the cement is hydrated at the negative temperature and how fast and violent the hydration reaction of the cement at the negative temperature, greatly shorten the research and development time of cement products, improve the efficiency, and qualitatively and quantitatively evaluate and predict the performance of the negative temperature cement, thereby being more practical.
Description
Technical Field
The invention belongs to the technical field of cement performance measurement, and particularly relates to a method and a device for evaluating cement negative temperature hydration.
Background
Negative temperature construction is more and more common in winter, and along with the polar strategy of China, the development of cement-based cementing materials meeting the negative temperature environment requirements is urgent. Under the condition of negative temperature, whether the hydration reaction of the cement occurs or not, the speed and the intensity of the hydration reaction and the like are the keys for determining whether the cement is suitable for construction in the negative temperature environment or not. Therefore, the evaluation and the test of the cement negative temperature hydration performance are extremely important for the preparation and the construction of the cement for the negative temperature environment.
According to the research of the prior art, no method and device specially aiming at the cement hydration performance evaluation under the negative temperature condition are available at present. Therefore, the evaluation of the cement negative temperature hydration performance is still blank at present, and great difficulty is caused to research and development effect evaluation and research and development efficiency improvement of research and development personnel.
In the prior art, methods for measuring the heat of hydration of cement are defined in methods for measuring the heat of hydration of cement (GB/T12959-2008). The standard specifies a test environment temperature of 20 c and correspondingly an environment temperature of 20 c for the relevant instruments. Moreover, the standard also requires that the water in the water tank of the cement hydration heat tester be kept at ambient temperature (i.e., 20℃.) at all times. Obviously, the method and the equipment specified by the standard are not suitable for evaluating the hydration performance of the cement constructed in the negative temperature environment. The reason is as follows: (1) The water in the water tank cannot be in a liquid state under the condition of negative temperature; (2) Precision components such as temperature sensors of instruments are not suitable for negative temperature environments.
Based on the above background, it is necessary to establish a hydration performance evaluation method for cement suitable for construction in a negative temperature environment and to develop an evaluation device for cement negative temperature hydration.
Disclosure of Invention
The invention mainly aims to provide a method and a device for evaluating cement negative temperature hydration, aiming at solving the technical problem that the existing method and device are not suitable for evaluating the cement negative temperature hydration performance under a negative temperature environment, and providing the method and the device for evaluating the cement negative temperature hydration, which can quickly and intuitively obtain the temperature change curve of slurry when cement is hydrated under the negative temperature, accurately evaluate whether the cement is hydrated under the negative temperature, and evaluate the speed and the intensity of the hydration reaction of the cement under the negative temperature, greatly shorten the research and development time of cement products, improve the efficiency, qualitatively and quantitatively evaluate and predict the performance of the negative temperature cement, and are more suitable for practical use.
The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. The invention provides an evaluation method of cement negative temperature hydration, which comprises the following steps:
1) Preparing cement and auxiliary materials at the test temperature into slurry at the test temperature; wherein, the test temperature T 1 ≤0℃；
2) Obtaining the change relation of the temperature of the slurry along with the measurement time; wherein the ambient temperature during the test time is maintained at the test temperature; the heat dissipation constant between the slurry and the environment is less than or equal to 100 joules/(hours multiplied by centigrade degrees);
3) Calculating a time value t with the first derivative equal to 0 and the second derivative smaller than 0 by taking the measured first derivative and the second derivative of the temperature of the slurry against time;
if the time value t does not exist, the cement is considered to be incapable of hydrating at the testing temperature, and the cement is judged to be not suitable for construction at the testing temperature; or,
taking the temperature corresponding to the minimum time in the time value T as T 2 Calculate Δ T = T 2 -T 1 In units of; if Δ T<At 10 ℃, the cement is regarded as the cement in the testAnd the cement is difficult to hydrate at the test temperature, and the cement is judged to be not suitable for construction at the test temperature.
The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.
Preferably, the method further comprises the step of, when the test temperature is-30 ℃ to-20 ℃, determining that the following conditions are met: delta T is more than or equal to 45 ℃ and T 1 ≤40min、t 2 Less than or equal to 200min; or delta T is more than or equal to 30 DEG C<At 45 ℃ and t 1 ≤30min、t 2 Less than or equal to 200min; or delta T is more than or equal to 10 DEG C<At 30 ℃ and t 1 ≤20min、t 2 Less than or equal to 100min; judging that the cement is suitable for construction in an environment of-30 ℃ to-20 ℃; wherein, t 1 Epitaxial initiation time, t, for temperature variation 2 The epitaxial termination time for temperature change.
Preferably, in the method, when the test temperature is-20 ℃ to-10 ℃, the following conditions are met if the measurement result: delta T is more than or equal to 45 ℃ and T 1 ≤40min、t 2 Less than or equal to 200min; or delta T is more than or equal to 30 DEG C<At 45 ℃ and t 1 ≤30min、t 2 Less than or equal to 200min; or delta T is more than or equal to 10 DEG C<At 30 ℃ and t 1 ≤20min、t 2 Less than or equal to 100min; judging that the cement is suitable for construction at the temperature of between 20 ℃ below zero and 10 ℃ below zero; wherein, t 1 Epitaxial initiation time, t, for temperature variation 2 The epitaxial termination time for temperature change.
Preferably, the method further comprises the step of, when the test temperature is-10 ℃ to 0 ℃, if the measurement result meets the following condition: delta T is more than or equal to 30 ℃ and T 1 ≤40min、t 2 Less than or equal to 200min; or delta T is more than or equal to 10 DEG C<At 30 ℃ and t 1 ≤20min、t 2 Less than or equal to 200min; judging that the cement is suitable for construction at the temperature of-10-0 ℃; wherein, t 1 Epitaxial start time, t, for temperature variation 2 The epitaxial termination time for temperature change.
The object of the present invention and the technical problem to be solved are also achieved by the following technical means. The invention provides an evaluation device for cement negative temperature hydration, which comprises a constant temperature bath box body, and the evaluation device comprises:
the closed container comprises a cylinder body and a cover body which are detachably connected; the barrel body and the cover body sequentially comprise an inner wall, a heat insulation material layer and an outer wall from inside to outside; the cover body is provided with a sensor interface;
the temperature sensor is detachably connected to the cover body through the sensor interface; the middle upper part of the temperature sensor is provided with threads for mounting a sensor protection shell;
the reaction container is movably arranged in the closed container and is used for containing slurry; the bottom surface of the sealed container is isolated from the bottom surface of the sealed container by adopting a heat insulation material layer, and a gap is arranged between the side wall of the sealed container and the side wall of the sealed container;
and the bracket is arranged in the constant-temperature bath box body and is used for supporting the closed container.
The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.
Preferably, the device further comprises a metal clip for fixing the temperature sensor to the cover; a rotatable wrench is arranged above the metal clamp, and the metal clamp and the wrench are integrally processed.
Preferably, the apparatus is characterized in that the closed container is placed in a constant temperature bath at a constant temperature; the distance between the outer wall of the constant temperature bath box body and the side wall, the bottom surface and the liquid level of the constant temperature bath box body is more than or equal to 10mm.
Preferably, in the device, the heat dissipation constant of the closed container is less than or equal to 100 joules/(hour × degree centigrade).
Preferably, in the device, the range of the temperature sensor is-35 to 60 ℃; the constant temperature bath box body is provided with a temperature monitoring device, and the measuring range of the temperature monitoring device is-40-60 ℃.
By means of the technical scheme, the method and the device for evaluating the cement negative temperature hydration, provided by the invention, have the advantages that:
1. according to the method and the device for evaluating the cement negative temperature hydration, the polyurethane layer and the air layer are adopted to isolate the cement paste from the external environment through the heat-insulating closed container, so that the method and the device have a good heat-insulating effect, can prevent the dissipation of heat released during the hydration of the cement, and are convenient to obtain a temperature change curve capable of accurately reflecting the hydration process;
2. according to the method and the device for evaluating the cement negative temperature hydration, the barrel body and the cover body of the closed container are connected in a threaded rotating mode, so that the method and the device have good sealing performance, are convenient and practical, and are simple to operate;
3. according to the method and the device for evaluating the cement negative temperature hydration, the metal cover body is designed in a U shape and is filled with the polyurethane layer, and the temperature sensor can be inserted into the sensor interface of the temperature sensor to enter the inside of the slurry body, so that the heat preservation performance of the whole device is further ensured, and the relative accuracy of an evaluation result is ensured;
4. according to the method and the device for evaluating the cement negative temperature hydration, the temperature sensor is fixed by the metal clamp with the threads, so that the problem that the sealing performance of the temperature sensor is influenced by the expansion of the diameter of an upper interface of a cover body due to the fact that the temperature sensor is inserted and taken for many times is solved; moreover, only the corresponding metal clip needs to be replaced when the device is disassembled and replaced, so that the service life of the device is prolonged, and the maintenance difficulty and cost are greatly reduced;
5. according to the method and the device for evaluating the negative temperature hydration of the cement, the screw thread is arranged on the middle upper part of the temperature sensor and the plastic protective shell is arranged, so that the temperature sensor and the plastic protective shell can be effectively separated, the matched plastic protective shell is installed again during the secondary test, a new sensor does not need to be replaced every time, the use times of the temperature sensor are greatly prolonged, and the cost is obviously reduced; moreover, the temperature sensor can be effectively immersed in the cement slurry, so that the accuracy of a tested temperature curve is ensured;
6. the method and the device for evaluating the cement negative temperature hydration summarize the standard of the cement negative temperature hydration reaction evaluation through a large amount of laboratory data, utilize the data for evaluating the cement negative temperature hydration performance to be identical with the actual data of engineering construction in the extremely cold region, not only can effectively guide the research and development of cement products, but also can provide a basis for the performance evaluation of products suitable for the extremely cold region.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to make the technical solutions of the present invention practical in accordance with the contents of the specification, the following detailed description is given of preferred embodiments of the present invention with reference to the accompanying drawings.
Drawings
FIG. 1 is a graph showing the change in hydration temperature of muddy water in an environment of-10 ℃;
FIG. 2 is a graph showing the change in hydration temperature of cement in an environment of-20 ℃;
FIG. 3 is a graph showing the variation of cement hydration temperature in an environment of-30 ℃;
FIG. 4 is a schematic diagram of a cement slurry reaction system in the apparatus according to the present invention;
FIG. 5 is a schematic structural diagram of a cement negative temperature hydration evaluation device provided by the invention.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be given to the specific implementation, structure, characteristics and effects of the method and apparatus for evaluating cement hydration at negative temperature according to the present invention with reference to the accompanying drawings and preferred embodiments.
The invention provides a method for evaluating cement negative temperature hydration, which comprises the following steps: 1) Preparing cement and auxiliary materials with the test temperature into slurry with the test temperature; wherein, the test temperature T 1 Less than or equal to 0 ℃; 2) Obtaining the change relation of the temperature of the slurry along with the measuring time; wherein the ambient temperature during the test time is maintained at the test temperature; the heat dissipation constant between the slurry and the environment is less than or equal to 100 joules/(hours multiplied by centigrade degrees); 3) Calculating a time value t with the first derivative equal to 0 and the second derivative smaller than 0 by taking the measured first derivative and the second derivative of the temperature of the slurry against time; if the time value t does not exist, the cement is considered to be incapable of hydrating at the testing temperature, and the cement is judged to be not suitable for construction at the testing temperature; or, the temperature corresponding to the minimum time in the time value T is taken as T 2 Calculating Δ T = T 2 -T 1 The unit is; if it isΔT<And if the temperature is 10 ℃, the cement is considered to be difficult to hydrate at the testing temperature, and the cement is judged to be not suitable for construction at the testing temperature.
When cement evaluation is carried out, firstly, the cement to be evaluated and auxiliary materials are subjected to a first constant temperature at a test temperature, prepared into slurry at the test temperature, and the slurry is placed in a heat-insulating closed container; and (3) placing the closed container at the test temperature for second constant temperature, and obtaining the temperature of the slurry within the measurement time.
Under the evaluated negative temperature condition, whether the hydration of the cement occurs or not can be judged according to whether the maximum value of temperature rise occurs or not when the temperature of the cement changes. Since the temperature of the slurry is significantly increased at any time, for example, 10 ℃, it can be determined that the hydration reaction has occurred. As long as the cement undergoes hydration reaction, the slurry can emit heat; as soon as heat is given off, the slurry is heated and its temperature rises accordingly. The specific heat capacity of water is 4.2 kilojoules/(kilogram x degree centigrade), and the specific heat capacity of the slurry is greater than that of water. Therefore, when the temperature rises to 10 ℃ or higher, the cement is subjected to hydration reaction.
Preferably, the testing temperature is-30 ℃ to 0 ℃; the method is suitable for evaluating the hydration performance of the cement-based cementing material constructed in an extremely cold area at the temperature of-30-0 ℃.
The cement can be evaluated by the evaluation method only when the cement does not freeze under the evaluation negative temperature environment.
According to the test method disclosed by the invention, through a large number of test evaluations, technical support and guidance can be provided for guiding the selection of cement in the construction process of extremely cold regions, and the specific selection can be referred to as shown in the following table 1.
TABLE 1 Cement recommendation schemes applicable in different negative temperature environments
In Table 1 above, t 1 Is the starting time of said temperature change. It should be noted that the start time here is not a start time in absolute terms, but is a time corresponding to the intersection of the tangents of the two temperature profiles in which the curve occurs, and the value of the start time is greater than the absolute start time (the time at which the temperature rise starts relative to the test temperature), so t 1 Also known as extrapolated onset time; in the same way, t 2 Is the end time of said temperature change, also called extrapolated end time.
In the prior art, the evaluation of the cement hydration performance is carried out under the positive temperature condition, but with the development of science and technology, the cement for negative temperature construction is greatly required. In the process of researching the formula of the negative-temperature cement for a long time, the applicant finds that the negative-temperature construction performance of the developed negative-temperature cement is difficult to evaluate by adopting the conventional testing method. In order to quickly evaluate the negative temperature hydration performance of the cement, the applicant provides data evaluation basis of the performance and the actual construction performance of the negative temperature cement through long-term research summary, establishes the cement negative temperature hydration evaluation method, and can quickly evaluate the performance index of the researched new formula and predict the engineering effect of the cement negative temperature hydration evaluation method.
The cement is capable of negative temperature construction. During testing, powder raw materials such as cement are subjected to constant temperature in negative-temperature air at a first constant temperature for a certain time and then mixed, necessary additives such as a water reducing agent, a water retaining agent, a retarder, an early strength additive and the like which are subjected to the first constant temperature are added into the mixture according to a cement formula, and the obtained powder is stirred and mixed; adding the antifreezing agent with the first constant temperature into water according to the formula of cement, stirring and dissolving, and placing in the air with the negative temperature at the first constant temperature for a certain time; and pouring the mixed powder into an aqueous solution added with an antifreezing agent, and stirring to obtain slurry for testing.
Preferably, the first constant temperature adopts a negative temperature air bath; the air bath can be a negative temperature freezing box, a negative temperature experiment box, a constant temperature refrigerator or a constant temperature cold storage, etc.; and the second constant temperature adopts a negative temperature liquid bath.
The first constant temperature adopts a negative temperature air bath, and aims to provide a raw material storage environment under a simulated real environment for raw materials for testing, so that the characteristic data of cement hydration can be better obtained. And the second constant temperature is carried out by adopting a negative temperature liquid bath, and the liquid bath box body is used for containing the antifreeze or the aqueous solution of the antifreeze. Here, a liquid bath is used instead of a freezer, for the reasons of one hand: the thermal conductivity of liquids is generally higher than that of air. For example, an aqueous solution of ethylene glycol has a thermal conductivity that varies depending on the concentration of the solution, but has a thermal conductivity of at least about 0.2 watts/(m × degree celsius) while air has a thermal conductivity of only about 0.023 watts/(m × degree celsius). Therefore, the ethylene glycol water solution has a large heat conductivity coefficient, so that the liquid bath can reach the first constant-temperature negative-temperature environment more quickly on the whole, and the testing efficiency is improved. Another aspect is that: the specific heat capacity of the liquid is greater than the specific heat capacity of the gas. Generally, the specific heat capacity of air is about 1 kilojoule/(kilogram × degree centigrade), while the specific heat capacity of the aqueous ethylene glycol solution is about 3 kilojoules/(kilogram × degree centigrade), and the density of the aqueous ethylene glycol solution is much higher than that of air. Therefore, the constant temperature of the glycol aqueous solution with high specific heat capacity and high density is adopted, and the glycol aqueous solution is more favorable for keeping the stability of the internal temperature of the device under the condition of small volume difference, so that the accuracy of the test result is improved. In addition, the liquid bath is more favorable for realizing the miniaturization and integration of the negative temperature hydration test device and the experimental operation.
Preferably, the concentration of the ethylene glycol aqueous solution is determined according to the negative temperature to be tested, as long as the solution is ensured to be in a liquid state at the test temperature.
Preferably, the closed container is placed in a negative temperature liquid bath for constant temperature; the distance between the outer wall of the liquid bath and the side wall, the bottom surface and the liquid level of the liquid bath is more than or equal to 10mm.
In order to reduce the influence of the external environment on the ambient environment of the closed container on the change of the cement paste temperature, the position of the closed container in the technical scheme of the invention requires that a certain distance is kept between each direction and a box body of the liquid bath, and the upper surface of the closed container also needs to be kept at a certain distance from the liquid level. From the viewpoint of test accuracy, the distance should be generally greater than or equal to 10mm, but in practical operation, the distance should not be too large, so as to realize miniaturization and integration of the thermostatic device.
Preferably, the sealing performance of each interface part between the closed container and the outside is ensured so as to prevent the glycol aqueous solution from permeating into the closed container; polytetrafluoroethylene seals may be used.
Preferably, the heat dissipation constant of the closed container is less than or equal to 100 joules/(hour multiplied by centigrade).
The closed container is arranged by adopting a heat insulation structure. Although the heat insulation described here is the most ideal state, it is difficult to absolutely insulate the closed container in actual practice.
In the testing method of the invention, in order to enable the slurry to be continuously stabilized at the negative temperature testing temperature before hydration occurs, a very stable external environment must be provided for the slurry through the second constant-temperature liquid bath, and the defect that the closed container is not completely insulated is overcome, so that the temperature of the slurry is prevented from being affected by the external environment and being disturbed, such as increased temperature, when the hydration of the slurry is not started. If this occurs, it is difficult to tell if hydration is initiated at the set negative temperature test temperature or after an increase in temperature perturbation when hydration is monitored. Once the hydration reaction is started, the invention hopes that the closed container is as heat-insulated as possible to prevent heat exchange of the container and avoid distortion of slurry temperature data, and the second constant-temperature liquid bath is adopted to always keep the external environment temperature (the set negative temperature test temperature) unchanged, so that all temperature data in the test period are based on the same base point, namely the set negative temperature test temperature, and the accuracy of the test result is ensured.
In the technical scheme of the invention, the heat dissipation constant of the closed container is controlled by adopting a heat preservation measure, so that the heat during the hydration of the slurry can be kept to the maximum, the loss of the hydration heat is reduced as much as possible, and whether the hydration of the cement occurs, the speed of the hydration of the cement and the intensity of the reaction can be accurately evaluated through the change of the temperature of the slurry.
The second constant-temperature liquid bath is used for keeping the temperature of the closed container constant before hydration is started, so that the slurry can be kept constant at the test temperature, and the monitoring of the hydration starting temperature is prevented from being influenced. After the hydration is started, the second constant-temperature bath needs to be kept at the constant temperature of the closed container so as to ensure that the base point of the external environment temperature is unchanged, and thus the data repeatability and the reproducibility of the evaluation method are improved.
Preferably, two samples are tested in parallel for each cement and the results averaged.
It should be noted here that when the test method is used for evaluating the hydration performance of cement at negative temperature, a group of tests needs to be performed on two samples independently at the same time to ensure the accuracy of the group of test results. Therefore, two sets of testing devices are required to be simultaneously carried out for each test.
As shown in fig. 4 and 5, the present invention further provides an evaluation apparatus for negative temperature hydration of cement, which comprises a constant temperature bath box 9, including:
the closed container comprises a cylinder body 1 and a cover body 2 which are detachably connected; the barrel body 1 and the cover body 2 sequentially comprise an inner wall 11, a heat insulation material layer 12 and an outer wall 13 from inside to outside; the cover body 2 is provided with a sensor interface 21;
the temperature sensor 3 is detachably connected to the cover body 2 through the sensor interface 21; the middle upper part of the temperature sensor 3 is provided with a thread 31 for installing a sensor protection shell 32.
The reaction container 4 is movably arranged in the closed container and is used for containing slurry 6; the bottom surface of the container is isolated from the bottom surface of the closed container by a heat insulation material layer 41, and a gap 42 is formed between the side wall of the container and the side wall of the closed container;
and a support 8 which is arranged in the constant temperature bath box body 9 and is used for supporting the closed container.
The closed container and the reaction container are combined into a cement slurry reaction system, and after the cement is prepared into slurry according to a formula and a process, the slurry is filled into the reaction container to generate hydration reaction.
During testing, slurry prepared according to the formula and the process is filled into a reaction container, and then the reaction container is placed into a closed container; mounting the temperature sensor on the cover body; the sensor is inserted into the slurry body for temperature measurement; the lower part of the sensor is provided with a protective shell made of plastic materials for protecting the sensor, the protective shell is sleeved outside the sensor through sensor threads, the sensor can be assembled, disassembled and replaced at any time according to needs, and the sensor can be prevented from being damaged due to the fact that the sensor and solidified slurry are solidified together.
After the test is finished, the cement paste is coagulated and hardened and is tightly bonded with the plastic sensor protective shell, the temperature sensor is driven to be separated from the plastic sensor protective shell by rotating the metal cover body, and the plastic cylinder filled with the hardened cement paste is taken out after the temperature sensor is taken out, so that the next test can be carried out.
Preferably, in one embodiment, the cylinder body of the closed container is formed by sleeving two metal cylinders (called an outer metal cylinder and an inner metal cylinder) with different diameters and bottom covers together, and an insulating material layer is filled between the inner metal cylinder and the outer metal cylinder; in one embodiment, polyurethane is filled between the two cartridges, which does not need to be replaced during use. The polyurethane has good heat insulation effect, and can approximately meet the requirement that the system is a heat insulation system.
Preferably, in one embodiment, the outer metal cylinder is made of brass, and has an outer diameter of 162mm, an inner diameter of 160mm, an outer height of 201mm, an inner height of 200mm, an outer thread of 1.5mm formed on the upper surface, and a thickness of 1mm on both the side surface and the bottom surface. The inner metal cylinder is made of brass, the outer diameter of the inner metal cylinder is 130mm, the inner diameter of the inner metal cylinder is 128mm, the outer height of the inner metal cylinder is 185mm, the inner height of the inner metal cylinder is 184mm, and the thicknesses of the side surface and the bottom surface are 1mm. When the metal tube is manufactured, polyurethane is filled between the inner metal tube and the outer metal tube, and the thickness of the polyurethane on the bottom surface and the side surface is 15mm.
Preferably, the cover body in one embodiment is also sleeved by two metal cylinders with different diameters and provided with bottom covers. The sealing device comprises a barrel, a cover body and a sealing device, wherein an external thread is arranged on the outer side of the barrel, an internal thread is arranged on the inner side of the cover body, and the barrel and the cover body are connected in a threaded fit mode to seal the closed container.
Preferably, in one embodiment, the metal cover is made of brass and has a U-shaped inner diameter of 163.5mm, an inner height of 20mm, an outer diameter of 185mm and an outer height of 30mm. The inner wall is carved with 1.5mm screw thread, can twist with outer metal cylinder. The diameter of the small hole in the center of the cover is 30mm, and 1.5mm internal threads are carved on the inner wall. The metal cover is filled with polyurethane.
Preferably, the outer walls of the cylinder and the cover are made of brass, which has excellent thermal conductivity and high heat transfer rate, and can rapidly balance the temperature of the outer wall of the closed container and the liquid in the liquid bath and maintain the stability of the reaction environment.
Preferably, the heat insulation material is polyurethane foam. During use, the polyurethane does not need to be replaced. Because the polyurethane has a good heat insulation effect, the closed container can approximately meet the requirement of heat insulation of the hydration reaction system.
Preferably, said closed container is placed on a support 8 in a thermostat bath cabinet 9 filled with an anti-freezing liquid 10.
Preferably, in one embodiment, the oven chamber has an inner length of 500mm, an inner width of 250mm and a thickness of 2mm. The constant temperature bath box body is made of plastic, and the constant temperature bath box body is filled with glycol solution during testing. The middle upper part of the constant temperature bath box body is provided with a bracket so as to fix the hydration temperature measuring device. An independent temperature monitoring device is arranged in the constant temperature bath box body and can monitor the temperature of the glycol solution in the water tank.
Preferably, the number of the supports is two, and two samples can be tested in parallel at the same time during each test so as to ensure the accuracy of the test result.
Preferably, in one embodiment, the bracket is made of brass, the length and the width of the bracket are the same as the inner size of the water tank, and the thickness of the bracket is 1mm. Two round holes with the diameter of 162mm are formed, and the hydration temperature measuring device can be placed into the round holes for fixing.
Preferably, in one embodiment, a plastic tube having an outer diameter slightly smaller than the inner diameter of the inner metal tube, i.e., a reaction vessel, is disposed inside the inner metal tube for containing cement slurry. The bottom of the plastic cylinder is provided with a polyurethane cushion layer, and the surrounding space of the plastic cylinder is filled with an air isolation layer.
Preferably, in one embodiment, the reaction vessel, i.e., the plastic cylinder, has an outer diameter of 124mm, an inner diameter of 120mm, an outer height of 150mm, an inner height of 148mm, and a side and bottom thickness of 2mm. The plastic cylinder is arranged in the inner metal cylinder, polyurethane with the thickness of 34mm is filled at the bottom of the plastic cylinder, and the plastic cylinder is not filled at the side and is filled with air. The polyurethane layer is manufactured in advance, and the adhesion of the polyurethane layer to the plastic cylinder is avoided. In the using process, the polyurethane layer does not need to be replaced. Because a gap (air layer) is arranged between the side walls of the plastic cylinder and the inner metal cylinder, the plastic cylinder is conveniently placed into or taken out of the inner metal cylinder.
Preferably, the device further comprises a temperature recording device 7. The temperature recording device adopts the prior art products sold in the market. During testing, the temperature sensor is inserted into the closed container and is immersed into the slurry so as to accurately acquire real-time temperature data of the slurry. The interface between the temperature sensor and the closed container must be sealed to prevent the closed container from being infiltrated with liquid.
Preferably, the temperature recording device is connected with the temperature sensor through a data line to record temperature data in real time.
Preferably, a memory card is arranged in the temperature recording device for recording, and data of the temperature recording device can be led into a computer for data presentation and analysis.
According to the test requirements of the method of the invention, which aim to test the negative temperature hydration performance of the cement, the temperature sensor and the constant temperature bath configured according to the invention therefore both have requirements for their operating temperature.
Preferably, the temperature sensor for acquiring the temperature of the slurry has the range of-35 to 60 ℃ and the precision of 0.1 ℃.
Preferably, the temperature monitoring device for the constant temperature bath for providing the negative temperature environment has a range of-40 to 60 ℃ and an accuracy of 0.1 ℃.
The temperature monitoring device can display temperature data in real time so as to realize real-time monitoring.
The heat dissipation constant of the device needs to be measured before the device is used, the heat dissipation constant of the device in a negative temperature test environment is required to be less than 100 joules/(hours multiplied by centigrade), the requirements in the standard (GB/T12959-2008) are met, and the device is allowed to be used for evaluation and test of cement hydration.
Preferably, it also includes a metal clip 5 for fixing the temperature sensor 3 on the cover 2; a rotatable spanner is arranged above the metal clamp 5, and the metal clamp 5 and the spanner are integrally machined.
The outer surface of the cylindrical metal clamp is provided with threads, and the cylindrical metal clamp can be screwed into a small hole (a sensor interface) of the metal cover through the threads to be fixed. The inner surface of the metal clip has certain friction force, and the temperature sensor can be clamped and fixed on the cover body. If the temperature sensor is damaged, the metal clamp for fixing the temperature sensor can be rotated, the temperature sensor and the cover body are separated, the metal clamp is detached, and the damaged sensor can be taken out and the intact sensor can be replaced.
The metal clip can be used for more conveniently mounting and dismounting the temperature sensor and the interface of the cover body.
Preferably, in one embodiment, the metal clip and the wrench are made of brass or iron.
Preferably, in one embodiment the metal clip cylinder portion has an outer diameter of 30mm, an inner diameter of 28mm and a height of 40mm. The inner part of the sensor is smooth and can clamp the upper part of the sensor; the outside has the screw thread, and the screw thread degree of depth is 1.5mm, can screw into the temperature sensor interface at metal lid body center.
Preferably, in an embodiment, a silicone gasket is disposed on an inner surface of the metal clip, so as to ensure that the temperature sensor is reliably fixed and has good sealing performance.
When the sensor is used, the sensor provided with the plastic shell is arranged on the metal cover in advance through the metal clamp, and the position is adjusted. And then, injecting the cement paste into the plastic cylinder, and screwing the metal cover, so that the temperature change in the cement paste can be recorded in real time.
The temperature curve process of cement negative temperature hydration by using the method and the device of the invention is as follows:
24h before testing, the prepared ethylene glycol aqueous solution is placed in a constant-temperature bath box body and placed in a negative-temperature environment. In particular, the cement negative temperature hydration is measured as the cement hydration temperature and its variation at constant ambient temperature. The function of the ethylene glycol aqueous solution is to ensure that the temperature of the external environment is constant during the test.
Before testing, all parts of the device and related articles are placed in a negative temperature environment for more than 24 hours. It is particularly noted that a set of tests needs to be performed independently twice at the same time to ensure the accuracy of the set of tests. Therefore, two sets of the device are required for each test.
The amount of water used to determine the standard consistency of the neat paste sample. In a negative temperature environment, the water consumption of the standard consistency of each cement sample is measured according to GB/T1346-2011 and recorded. It is to be noted that the water is an aqueous solution to which an antifreeze agent is added, and the freezing point (freezing point) of the water is much lower than 0 ℃. For example, with the addition of an aqueous solution of 26.67% calcium nitrate and 6.67% calcium formate, the freezing point can be lowered to-24 ℃.
And determining the water consumption of the mortar sample. In a negative temperature environment, 1350g of standard sand and 450g of cement are weighed, the water addition amount is calculated according to the following formula, and the calculation result is reserved to 1mL;
M＝(P+5％)×450
in the formula: m-water usage in milliliters (mL); p-water consumption for standard consistency,%; the water addition coefficient is 5%.
In a negative temperature environment, wiping a stirring pot and stirring blades by using damp flannelette, then sequentially adding weighed standard sand and cement into the stirring pot, fixing the stirring pot on a base of a stirring machine, starting the stirring machine to stir slowly for 30s, then slowly adding weighed water within 20s, continuing to stir slowly for 60s, and then stirring quickly for 60s. The stirring speed was changed without stopping.
In a negative temperature environment, after stirring, quickly taking down the stirring pot and stirring for several times by using a spoon, then weighing 2 parts of glue and sand with the mass of (800 +/-1) g, respectively filling the glue and sand into two prepared plastic cylinders, screwing down an assembled metal cover to enable a sensor positioned below the screw thread to be immersed into the slurry, and simultaneously recording by using a recording device. It should be noted that the mortar height does not exceed the threaded portion.
In the whole process, all parts except the recording device are immersed in the ethylene glycol solution, the liquid level of the ethylene glycol is at least 10mm higher than the upper surface of the cement slurry reaction system, and the fluctuation range of the environmental temperature is monitored. The allowable fluctuation range was. + -. 0.1 ℃. It is noted that the metal lid was sealed with vaseline to prevent glycol solution from entering the interior of the device.
After the test is finished, the cement paste is solidified and hardened, the plastic shell and the cement paste are tightly adhered together, and the plastic shell is separated from the sensor by unscrewing the metal cover. And (4) taking out the sensor and the plastic barrel in sequence, and installing a new plastic shell on the sensor for the next test.
The memory card in the recording device is taken out and the data can be read after the memory card is inserted into a computer. The results of the two tests are averaged.
This is further illustrated by the following more specific examples. In the examples described below, in order to visually express the course of the temperature change of the slurry, the applicant rendered the collected temperature data as a curve. In actual operation, the data of the temperature change can be processed by various data processing software to directly obtain the result.
Example 1
The prepared glycol solution is put into a water tank 24 hours before testing and is placed in an environment at the temperature of minus 10 ℃. Before testing, all parts of the device and related articles are placed in an environment with the temperature of-10 ℃ for more than 24 h. And determining the water consumption of the standard consistency of the net paste sample. The water usage at standard consistency was measured at-10 ℃ for each cement sample according to GB/T1346-2011 and recorded. The water usage for standard consistency was measured to be 0.23. And determining the water consumption of the mortar sample. 1350g of standard sand and 450g of cement are weighed at the temperature of-10 ℃, and the water consumption of a mortar sample is 126mL according to the water consumption of the standard consistency.
Wiping the stirring pot and the stirring blades by using damp flannelette at the temperature of minus 10 ℃, then sequentially adding weighed standard sand and cement into the stirring pot, fixing the stirring pot on a base of a stirring machine, starting the stirring machine to stir slowly for 30s, then slowly adding weighed water within 20s, continuing to stir slowly for 60s, and then stirring quickly for 60s. The stirring speed was changed without stopping. Under the condition of-10 ℃, after stirring, quickly taking down the stirring pot and stirring for several times by using a spoon, then weighing 2 parts of glue and sand with the mass of (800 +/-1) g, respectively filling the glue and sand into two prepared plastic cylinders, screwing down an assembled metal cover, and immersing a sensor positioned below the screw thread into the slurry, wherein the recording device records simultaneously. It should be noted that the mortar height does not exceed the threaded portion. In the whole process, all parts except the recording device are immersed in the ethylene glycol solution, the liquid level of the ethylene glycol is at least 10mm higher than the upper surface of the cement slurry reaction system, and the environmental temperature is controlled to be minus 10 +/-0.1 ℃. It is noted that the metal lid was sealed with vaseline to prevent glycol solution from entering the interior of the device.
After the test is finished, the cement paste is solidified and hardened, the plastic shell and the cement paste are tightly adhered together, and the plastic shell is separated from the sensor by unscrewing the metal cover. And (4) taking out the sensor and the plastic barrel in sequence, and installing a new plastic shell on the sensor for the next test.
The memory card in the recording device is taken out and the data can be read after the memory card is inserted into a computer. The results of the two tests are averaged. The test results are shown in FIG. 1. FIG. 1 is a hydration temperature curve at-10 ℃.
In example 1, when 10min had elapsed, the slurry corresponded to a maximum temperature of 26 ℃ and a temperature rise of 36 ℃ which was greater than 30 ℃ and less than 45 ℃; the extrapolated onset time for temperature change was 3min and the extrapolated termination time was 95min. According to the judgment criterion, the cement is suitable for construction in a negative temperature environment of-10 to 0 ℃.
Example 2
The prepared glycol solution is put into a water tank 24 hours before the test, and is placed in an environment at the temperature of minus 20 ℃. Before testing, all parts and related articles of the device are placed in an environment of-20 ℃ for more than 24 h. And determining the water consumption for the standard consistency of the net slurry sample. The water consumption for each cement sample at-20 ℃ was measured according to GB/T1346-2011 and recorded. The water usage for standard consistency was measured to be 0.23. And determining the water consumption of the mortar sample. 1350g of standard sand and 450g of cement are weighed at the temperature of minus 20 ℃, and the water consumption of a mortar sample is 126mL according to the water consumption of the standard consistency.
Wiping the stirring pot and the stirring blades by using damp flannelette at the temperature of minus 20 ℃, then sequentially adding weighed standard sand and cement into the stirring pot, fixing the stirring pot on a base of a stirring machine, starting the stirring machine to stir slowly for 30s, then slowly adding weighed water within 20s, continuing to stir slowly for 60s, and then stirring quickly for 60s. The stirring speed was changed without stopping. And (2) rapidly taking down the stirring pot after stirring is finished and stirring for several times by using a spoon at the temperature of-20 ℃, then weighing 2 parts of colloidal sand with the mass of (800 +/-1) g, respectively filling the colloidal sand into two prepared plastic cylinders, screwing down an assembled metal cover, immersing a sensor positioned below the screw thread into the slurry, and simultaneously recording by using a recording device. It should be noted that the mortar height does not exceed the thread 7 portion. In the whole process, all parts except the recording device are immersed in the ethylene glycol solution, the liquid level of the ethylene glycol is at least 10mm higher than the upper surface of the cement slurry reaction system, and the environmental temperature is controlled to be minus 20 +/-0.1 ℃. It should be noted that the metal lid was sealed with vaseline to prevent the glycol solution from entering the inside of the device.
After the test is finished, the cement paste is solidified and hardened, the plastic shell and the cement paste are tightly adhered together, and the plastic shell is separated from the sensor by unscrewing the metal cover. And (4) taking out the sensor and the plastic barrel in sequence, and installing a new plastic shell on the sensor for the next test.
The memory card in the recording device is taken out and the data can be read after the memory card is inserted into a computer. The results of the two tests are averaged. The test results are shown in FIG. 2. FIG. 2 is a hydration temperature curve at-20 ℃.
In example 2, when a duration of 12min is reached, the slurry corresponds to a maximum temperature of 23 ℃ and a temperature rise of 43 ℃, this value being greater than 30 ℃ and less than 45 ℃; the extrapolated onset time for temperature change was 6min and the extrapolated termination time was 150min. According to the judgment criterion, the cement is suitable for construction in negative temperature environment of-20 to-10 ℃.
Example 3
The prepared glycol solution is put into a water tank 24 hours before the test, and is placed in an environment at the temperature of minus 30 ℃. Before testing, all parts of the device and related articles are placed in an environment of-30 ℃ for more than 24 h. And determining the water consumption for the standard consistency of the net slurry sample. The water usage at standard consistency was measured at-30 ℃ for each cement sample according to GB/T1346-2011 and recorded. The water usage for standard consistency was measured to be 0.23. And determining the water consumption of the mortar sample. 1350g of standard sand and 450g of cement are weighed at the temperature of-30 ℃, and the water consumption of a mortar sample is 126mL according to the water consumption of the standard consistency.
Wiping the stirring pot and the stirring blades by using damp flannelette at the temperature of minus 30 ℃, then sequentially adding weighed standard sand and cement into the stirring pot, fixing the stirring pot on a base of a stirring machine, starting the stirring machine to stir slowly for 30s, then slowly adding weighed water within 20s, continuing to stir slowly for 60s, and then stirring quickly for 60s. The stirring speed was changed without stopping. Under the condition of-30 ℃, after stirring, quickly taking down the stirring pot and stirring for several times by using a spoon, then weighing 2 parts of glue and sand with the mass of (800 +/-1) g, respectively filling the glue and sand into two prepared plastic cylinders, screwing down an assembled metal cover, and immersing a sensor positioned below the screw thread into the slurry, wherein the recording device records simultaneously. It should be noted that the mortar height does not exceed the threaded portion. In the whole process, all parts except the recording device are immersed in the ethylene glycol solution, the liquid level of the ethylene glycol is at least 10mm higher than the upper surface of the cement slurry reaction system, and the environmental temperature is controlled to be minus 30 +/-0.1 ℃. It should be noted that the metal lid was sealed with vaseline to prevent the glycol solution from entering the inside of the device.
After the test is finished, the cement paste is solidified and hardened, the plastic shell and the cement paste are tightly adhered together, and the plastic shell is separated from the sensor by unscrewing the metal cover. And (4) taking out the sensor and the plastic barrel in sequence, and installing a new plastic shell on the sensor for the next test.
The memory card in the recording device is taken out and the data can be read after the memory card is inserted into a computer. The results of the two tests are averaged. The test results are shown in FIG. 3. FIG. 3 is a hydration temperature curve at-30 ℃.
In example 3, when the duration was 15min, the slurry corresponded to a maximum temperature of 12 ℃, a temperature rise of 42 ℃, a value greater than 30 ℃ and less than 45 ℃; the extrapolated onset time for temperature change is 6min and the extrapolated termination time is 180min. According to the judgment criterion, the cement is suitable for construction in a negative temperature environment of-30 to-20 ℃.
From the test results of the embodiments 1, 2 and 3, the method and the device of the present invention can conveniently measure the change of the internal temperature of the mortar sample along with the hydration time, and further judge whether the hydration reaction is started at low temperature and how fast the reaction is. In examples 1, 2 and 3, a temperature rise of more than 10 ℃ was observed in tens of minutes for all mortar samples, which indicates that the hydration reaction did occur in a negative temperature environment. The test results of comparative examples 1, 2 and 3 show that the temperature rise of the sample is most remarkable in the environment of-10 ℃ and the temperature rise of the sample is least in the environment of-30 ℃, which means that the hydration reaction is most severe under the condition of-10 ℃ and the hydration reaction is most gentle under the condition of-30 ℃, which is consistent with the theory that the temperature is the main factor for determining the speed of the chemical reaction. The above results demonstrate that it is feasible to evaluate hydration reactions using the method and apparatus of the present invention.
Features of the invention claimed and/or described in the specification may be combined and are not limited to the combinations specified in the claims. The technical solutions obtained by combining the technical features in the claims and/or the specification also belong to the scope of the present invention.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.
Claims (9)
1. The method for evaluating the negative temperature hydration of the cement is characterized by comprising the following steps of:
1) Preparing cement and auxiliary materials with the test temperature into slurry with the test temperature; wherein, the test temperature T 1 ≤0℃；
2) Obtaining the change relation of the temperature of the slurry along with the measurement time; wherein the ambient temperature during the test time is maintained at the test temperature; the heat dissipation constant between the slurry and the environment is less than or equal to 100 joules/(hours multiplied by centigrade degrees);
3) Calculating a time value t with the first derivative equal to 0 and the second derivative smaller than 0 by taking the measured first derivative and the second derivative of the temperature of the slurry against time;
if the time value t does not exist, the cement is considered to be incapable of hydrating at the testing temperature, and the cement is judged to be not suitable for construction at the testing temperature; or,
taking the temperature corresponding to the minimum time in the time value T as T 2 Calculate Δ T = T 2 -T 1 In units of; if Δ T<And (4) judging that the cement is difficult to hydrate at the testing temperature when the temperature is 10 ℃, and judging that the cement is not suitable for construction at the testing temperature.
2. The method according to claim 1, wherein when the test temperature is-30 ℃ to-20 ℃, the following condition is satisfied if the measurement result:
delta T is more than or equal to 45 ℃ and T 1 ≤40min、t 2 Less than or equal to 200min; or,
30℃≤ΔT<at 45 ℃ and t 1 ≤30min、t 2 Less than or equal to 200min; or,
10℃≤ΔT<at 30 ℃ and t 1 ≤20min、t 2 ≤100min；
Judging that the cement is suitable for construction at the temperature of-30 ℃ to-20 ℃;
wherein, t 1 Epitaxial initiation time, t, for temperature variation 2 The epitaxial termination time for temperature change.
3. The method according to claim 1, wherein when the test temperature is-20 ℃ to-10 ℃, the following condition is satisfied if the measurement result is obtained:
delta T is more than or equal to 45 ℃ and T 1 ≤40min、t 2 Less than or equal to 200min; or,
30℃≤ΔT<at 45 ℃ and t 1 ≤30min、t 2 Less than or equal to 200min; or,
10℃≤ΔT<at 30 ℃ and t 1 ≤20min、t 2 ≤100min；
Judging that the cement is suitable for construction at the temperature of between 20 ℃ below zero and 10 ℃ below zero;
wherein, t 1 Epitaxial initiation time, t, for temperature variation 2 The epitaxy termination time for temperature variation.
4. The method according to claim 1, wherein when the test temperature is-10 ℃ to 0 ℃, the following condition is satisfied if the measurement result is obtained:
delta T is more than or equal to 30 ℃ and T 1 ≤40min、t 2 Less than or equal to 200min; or,
10℃≤ΔT<at 30 ℃ and t 1 ≤20min、t 2 ≤200min；
Judging that the cement is suitable for construction at the temperature of-10-0 ℃;
wherein, t 1 Epitaxial initiation time, t, for temperature variation 2 The epitaxy termination time for temperature variation.
5. The method according to claim 1, wherein the step 2) of obtaining the temperature variation of the slurry with the measurement time is performed by an evaluation device of cement negative temperature hydration; the evaluation device for cement negative temperature hydration comprises:
a constant temperature bath box body;
the closed container comprises a cylinder body and a cover body which are detachably connected; the barrel body and the cover body sequentially comprise an inner wall, a heat insulation material layer and an outer wall from inside to outside; the cover body is provided with a sensor interface;
the temperature sensor is detachably connected to the cover body through the sensor interface; the middle upper part of the temperature sensor is provided with threads for mounting a sensor protection shell;
the reaction container is movably arranged in the closed container and is used for containing the slurry; the bottom surface of the closed container is isolated from the bottom surface of the closed container by a heat-insulating material layer, and a gap is formed between the side wall of the closed container and the side wall of the closed container;
and the bracket is arranged in the constant-temperature bath box body and is used for supporting the closed container.
6. The method according to claim 5, wherein the evaluation device for cement negative temperature hydration further comprises a metal clip for fixing the temperature sensor on the cover body; a rotatable spanner is arranged above the metal clamp, and the metal clamp and the spanner are integrally machined.
7. The method according to claim 5, wherein the closed container is placed in a constant temperature bath at a constant temperature; the distance between the outer wall of the constant temperature bath box body and the side wall, the bottom surface and the liquid level of the constant temperature bath box body is more than or equal to 10mm.
8. The method of claim 5, wherein the closed container has a thermal dissipation constant of 100 joules/(hours x degrees Celsius) or less.
9. The method of claim 5, wherein the temperature sensor ranges from-35 ℃ to 60 ℃; the thermostatic bath box body is provided with a temperature monitoring device, and the measuring range of the temperature monitoring device is-40 to 60 ℃.
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