Building materials cement paper 1
Discussion on key problems of cement detection in building raw materials
With the continuous progress of science and technology in China and the rapid development of the construction industry, building materials have also made great innovations in performance and materials. Among the building materials, cement is a common raw material in building engineering, but its role in building engineering can never be ignored. It can be said that cement can have different effects on the quality and life of concrete structures to a certain extent. It can be seen that the quality of cement itself is very important to users, and testing is the only way to accurately judge the quality of cement. Only after testing can the quality of cement raw materials be effectively guaranteed and unqualified products be prevented from being mixed into construction projects. Starting with the cement in building materials, this paper discusses the key problems in cement detection, which will play a good role in improving the cement detection of building materials and further ensuring the cement quality.
Building raw materials; Cement; Detection; survey
Introduction:
When it comes to cement in construction industry, most people are familiar with it. However, from the perspective of construction engineering, cement not only participates in the construction of concrete structures as raw materials, but also has a certain influence on the overall quality and performance of concrete structures invisibly. Therefore, in building construction, it is very important to ensure the quality of cement and test the quality of cement through experiments.
First, the theoretical overview of cement
Cement is a very common and familiar building material in daily life, such as building houses, structures or other aspects. From the perspective of building materials, the definition of cement is relatively broad. All hydraulic cementing materials that are ground into powder and can become plastic slurry after reacting with water can be hardened not only in air but also in water, and can firmly bond aggregates such as sand and stone together, which are collectively called cement.
Although from the definition of cement, cement as a building material seems not difficult to understand, and gives most people the impression that the prerequisite for being defined as cement is not harsh, but it is not. As a very important raw material in construction engineering, cement also has some properties and characteristics suitable for construction engineering, such as stability and fineness modulus. These inherent characteristics of cement can not only make cement itself play its good positive performance in concrete structures, but also play an important role in cement testing and testing.
From the perspective of the development and innovation of modern building materials, cement is also virtually divided into many categories. Generally speaking, cement can be divided into ordinary cement, special cement and characteristic cement according to its use and performance. According to the names of hydraulic substances, they can be divided into portland cement, aluminate cement, sulphoaluminate cement and ferrite cement. According to technical characteristics, cement can be divided into quick-hardening cement, hydration heat cement, sulfate-resistant cement, expansive cement and high-temperature resistant cement. The classification of cement according to different standards also reflects some inherent characteristics of cement to some extent, which further illustrates the importance of cement testing and the negative impact of unqualified cement quality on construction projects.
Second, the influencing factors of cement detection of building raw materials
Since the implementation of the new standards for building engineering, many construction enterprises have simply reformed the maintenance pool, without improving and reforming the test conditions from a scientific point of view. In some enterprises, the temperature of the molding room is very high, even reaching 28℃, and the temperature and humidity in the curing box can not meet the requirements of relevant standards. There are also enterprises that use self-made curing boxes, but they are only rough, lacking temperature and humidity control devices and monitoring measures, and cannot play a role during the curing period. Specifically, it can be understood from the following aspects.
1. measuring instrument
Building raw material cement testing and measuring instruments, such as scales, thermometers, hygrometers, water dispensers, etc. , clearly defined in the relevant test standards, and their accuracy. However, according to the actual test survey data, some laboratories still use low-precision measuring instruments, which will invisibly reduce the test accuracy and affect the test results to varying degrees. For example, some inspection rooms use water adding devices with the accuracy of 5 mm or 2 mm, which can not accurately measure the amount of water and cement, and has a great influence on the water-cement ratio and lime-sand ratio of cement mortar.
2. Test mode.
Mold test is mainly aimed at cement strength test. In the relevant standards and specifications of test and detection, there are strict and specific regulations on the materials, dimensions and assembly accuracy of die trial production. However, in the implementation of specific test regulations, some testing laboratories do not attach great importance to the regulations of model test, mainly because the size of model test is far from the standard, and the assembly accuracy can not meet the corresponding standards for cement strength testing. In the process of testing and detection, although the relevant procedures of self-calibration have been completed.
3. Molding equipment.
Generally speaking, mixer and vibration table are the main molding equipment. For the mixer, it is necessary to adjust the gap between the mixer and the stirring pot at regular intervals according to the requirements of relevant standards, and at the same time, it is necessary to observe and maintain the shaking table regularly to ensure that the relevant molding standards are met. In addition, cement testing will be affected by human factors, the habit of human operation and the different effects of different human interference will have such and such effects on cement-related test testing.
Three, the key problems of cement detection in building raw materials
1. The first step of cement raw material testing is sampling testing before cement purchase. That is to say, when building raw material cement is ready to enter the site, the testing personnel need to sample and seal it, and then send it to the laboratory or other testing institutions for testing. At the same time, in order to carry out the follow-up work smoothly, cement samples need to be kept continuously for three months. In addition, the purchase of testing instruments and related equipment needs to be calibrated in advance. In the case of testing cement-related projects, in order to get more accurate testing conclusions, we must first ensure the integrity and accuracy of testing instruments, so as to ensure the quality of cement testing conclusions on the premise.
2. Appropriate test conditions are required: for example, before the test, cement materials and water need to be put into the molding room, and their temperatures should be measured scientifically to ensure uniform temperature, and the measurement results should be recorded; In the curing box, it is necessary to adjust the cement temperature reasonably by automatically controlling the temperature and humidity. Ordinary air conditioners can also be used to indirectly control the water temperature.
3. It is necessary to apply certain standard materials and do a comparative test: in the relevant standards in China, the production requirements for standard sand are higher and the price is more expensive. In an area, there are fewer vendors, so standard sand needs to be purchased from formal channels, and the certificate of standard sand and the authorization letter of the merchant are also needed when purchasing.
4. Inspection of cement fineness: In the inspection of cement fineness, sieve analysis method can be used to express the fineness of cement samples with the mass percentage of sieve residues in small holes, which may block the sieve holes in concrete practice. Therefore, after the screen is used for more than ten times, it is necessary to clean the test screen to ensure that it is clean and smooth enough, so as to significantly improve the accuracy of the results.
5. Specific water consumption for testing the viscosity of cement: If the water consumption is fixed, if the mixing water used is about 142 ml, 500 g of cement needs to be added and their mixture needs to be stirred in a mixing tank; After the mixing process is completed, put the cone mould into the pulp cleaner and do a good job of cement tamping and vibration leveling. Finally, the leveling process is carried out to measure the sinking depth of the test cone. Generally, if the amount of cement is increased, the strength of the mixture will increase, and at the same time, the shrinkage of the material will be improved; In the process of mixing the mixture, only a small amount of cement is added.
Four. Concluding remarks
As one of the most widely used building materials, the importance of cement is self-evident. Whether the quality of cement in building materials is qualified or not will have some negative effects on concrete structures and the whole building project. Therefore, it is essential and very important to control the quality of cement in building raw materials through testing, which is of great significance for accurately identifying the quality of cement and ensuring the quality of building projects.
References:
[1], Zhang. Analysis of cement detection elements in building engineering detection [J]. Building materials and decoration, 20 12 (12): 88
[2] Huang Huajun. Cement detection elements in construction engineering detection [J]. Construction industry, 20 13 (5): 67
Building materials cement paper 2
Discussion on key problems of cement detection in building raw materials
Abstract: At present, with the rapid development of China's economy and the construction of a harmonious society, people's living standards have been continuously improved, and China's construction industry has also developed rapidly. At the same time, the construction industry is also facing the problem of improving building quality. As we all know, the quality of buildings determines the safety of residents, and to ensure the quality of buildings, we must ensure the building materials. In building construction, cement is one of the most important raw materials in building materials. If the cement quality is not up to standard, it will reduce the stability and service life of the whole building. Therefore, in the construction of building projects, we should strengthen the detection of cement, so that the quality of cement meets the relevant regulations, so that the building project can be carried out smoothly.
Keywords: building materials; Cement testing; Key issues; Sampling; promote
introduce
Cement is one of the most common and important raw materials in construction engineering. In the process of construction, we usually mix water, sand and cement to form cement concrete, which can be used in building construction. With the rapid development of China's construction industry, the use of cement concrete is becoming more and more common in China. The reason why cement concrete is slightly better than many raw materials and can be reused in construction projects is mainly because cement concrete has the following advantages: high strength, good compression, heat resistance and wear resistance. As the main raw material in cement concrete, cement plays an important role in the construction of building engineering and plays an irreplaceable role.
First, the necessity of cement testing
Because cement is one of the most important and common raw materials in building materials, people attach great importance to the detection of cement. The quality of cement not only affects the construction of the project, but also affects the planning of the later stage of the project. However, there are still some problems in today's cement testing. Every step and every small link in cement testing, such as "equipment selection and equipment debugging" and "cement extraction and preservation", plays a decisive role. Any link that goes wrong will affect the overall situation. As the classical Chinese saying goes, "One short step makes an everlasting regret", any small problem in cement testing will lead to the failure of the whole project. Therefore, the necessity of cement testing is self-evident.
Second, the influencing factors in cement testing
(A) Instrument and equipment factors
It is difficult to tell whether the manufacturer of cement testing instruments and equipment is true or false, so we should pay strict attention to the quality of instruments and equipment in the procurement process. Before choosing to buy, the relevant procurement personnel should have a full understanding of suppliers, and the best way is to establish a special supplier file. Archives should cover these aspects: whether the quality of instruments and equipment provided by the supplier meets the relevant national standards; The supplier's quality supply ability and whether the products meet the technical requirements of the testing standards; Whether the supplier can guarantee timely and accurate delivery; Whether the supplier can deal with the quality problems of the equipment in time; Supplier's instrument and equipment quality management system and other information. Only by establishing such supplier files can the quality of purchased instruments and equipment be guaranteed and the test data be truly accurate.
(B) About the factors of manual sampling
We should test the cement according to the relevant provisions of the test work. In general, the acceptance of cement quality at the factory can be divided into two types: sample inspection based on the extraction of physical objects and inspection report based on the cement quantity of the manufacturer. However, the actual situation is different from the general situation. When cement inspection was carried out on the construction site, the inspection process was not strictly in accordance with the relevant provisions in the inspection specification, and the buyers and sellers did not strictly follow the relevant provisions in the cement inspection specification for some reasons, which made the sampling on the construction site questioned.
(3) Factors related to the test environment
In the process of cement testing, in addition to the above two points, the testing environment is also an important factor affecting the testing. When testing cement, testers should set and control the test environment in strict accordance with the requirements of test standards. In addition, it is necessary to record the configuration monitoring, temperature and humidity during the testing process, so as to strictly and effectively monitor the testing environment and get real and accurate testing results.
Three, the main points of cement testing
We should take samples before testing cement.
Before testing cement, samples should be taken, sealed in containers and labeled. Samples should be kept for three months in a row for better follow-up testing, and then sent for inspection in time. In the process of purchasing testing instruments and equipment, it is necessary to conduct accurate on-site calibration of equipment and instruments and do a good job in market research. This is because only by ensuring the quality of instruments and equipment can cement be accurately detected.
(2) The test conditions should be appropriate.
For example, before the test, it is necessary to select appropriate test conditions, put cement materials and water into the molding chamber, and then test its temperature regularly, reasonably and scientifically to make it have a uniform temperature, and record the test results. The accuracy of detection will directly affect the temperature. In the curing box, by automatically controlling the temperature and humidity, the cement temperature can be adjusted reasonably and scientifically, and even the water temperature can be indirectly controlled by air conditioning. At present, with the rapid development of science and technology, more and more cement temperature control devices appear, especially automatic control system devices, which reduce or even avoid the occurrence of human detection errors and have high economic benefits.
(three) the application of a standard substance, do a good job of contrast test.
In the relevant standards of cement testing in China, the requirements for making standard sand are very high. Because the price of standard sand is relatively expensive, and there are few vendors of standard sand in a region. This requires us to strictly control the way of purchasing standard sand, and pay attention to obtaining the certificate of standard sand and the authorization of the merchant during the purchase process.
(4) detecting the fineness of cement
We can test the fineness of cement by sieve analysis. We will use a very small hole to express the fineness of cement samples by the mass percentage of the remaining substances in the sieve. But ideas are not equal to reality. In practice, the screen holes may be blocked during the screening process. This problem arises. If the sieve holes are blocked, the sieving time is limited, and the sieving results will be greatly affected. Therefore, it is necessary to clean the test network that has been screened for more than ten times in time to ensure cleanliness and smoothness and improve accuracy.
(5) Water consumption for cement viscosity test
Under the condition of fixed water quantity, if the mixing water used should be controlled at about 142 liter, it is necessary to add about 500g of cement and stir it in a stirring pot to form a mixture. After mixing, put the conical mould into a pulp cleaner to tamp and vibrate the cement. Finally, the leveling work is carried out, and then the depth of the cone test die is accurately measured. When determining the sinking depth of the cone, it must be ensured that it does not exceed 3 ".
Fourth, improve the detection method of cement materials
(A) to strengthen the control of testing instruments
Testing equipment and instruments play an indispensable role in cement testing. Therefore, the effective way to improve the detection of cement materials is to strengthen equipment control. Before the equipment is used, daily and regular inspection and adjustment must be carried out to improve the equipment testing system. Relevant testing personnel should send the equipment to the testing department for testing in time and regularly to prevent the testing work from being affected by the problems of the equipment itself. In addition, when the equipment is found to be inaccurate, I will proofread it in time.
(two) failing to implement cement testing according to the regulations.
Testing personnel should ensure that the cement testing data meet the national cement testing standards, and carry out testing according to relevant testing regulations, so as to scientifically and reasonably reduce errors and make the data accurate and reliable. For inspectors who are not familiar with the testing process, intensive training should be carried out to improve the testing technology and quality of inspectors.
(C) Pay attention to the supervision and management of cement stability testing
In the process of cement testing, attention should be paid to the detection of cement stability and strength. For the detection of cement strength and stability, regular inspection and management should be carried out according to the number of times the instrument is used, and problems should be solved in time when found. Like the problem of low accuracy of testing instruments, it is necessary to update them in time.
label
To sum up, the test and inspection of building engineering is an indispensable part of quality control in the process of building engineering construction, and it is also a very important part of completion acceptance evaluation. Testing cement materials can reduce or even avoid construction accidents. This preventive measure of detecting cement composition can improve the quality of building construction and provide guarantee for the property safety of Chinese residents.
refer to
Yin Na. Analysis of test points of cement materials [J]. Sichuan Cement, 2015,04:12.
[2], Li, Discussion on key problems of cement detection in building materials [J]. Communication Science and Technology Heilongjiang, 2015,05:174.
[3] Han Zhixin. On the detection of building raw materials [J]. Jilin Agriculture, 20 12, 1 1: 253.
[4] Zhang Zhijun. Study on quality control of concrete raw materials [D]. Hebei University of Technology, 20 14.
[5]__ Yong. Analysis of cement detection in building engineering detection [J]. Doors and windows, 2014,08:116.
Thai navy. Influencing factors and quality control of cement inspection [J]. Sichuan Cement, 20 15, 09: 9.
Building materials cement paper 3
Discussion on quality inspection of building cement
This paper introduces the detection indexes and key points of detection methods of building cement from two aspects of physical indexes and chemical indexes, expounds the factors influencing cement quality detection, and points out the control methods.
Keywords: cement; Physical and chemical indicators; Detection; Influencing factors; Control; evaluate
Cement is one of the essential basic raw materials in building construction, and the quality of cement has a great influence on the quality of building engineering. Therefore, strengthening the detection of cement quality is of great significance to ensure the quality of construction projects. This paper expounds the detection methods of cement, sums up the influencing factors in the cement detection, and probes into the measures and methods for improving the cement quality detection.
A, cement physical indicators detection
1. Water consumption for standard consistency of cement.
By measuring the water consumption when the cement slurry reaches the standard consistency, it is used as the standard of cement setting time and stability test water consumption. During the test, the estimated amount of mixed water was poured into the wetted mixing tank, and then 500 grams of cement samples were poured. Immediately after stirring, put the clean slurry into the test mold on the glass plate at one time. After tamping and vibrating, quickly put the trial connecting plate on the Vicat instrument, lower the test bar to the surface of clean cement slurry, tighten the screw and suddenly loosen it, so that the test bar can freely and vertically sink into the clean cement slurry, and record the distance between the test bar and the bottom plate until it stops sinking. Repeatedly use different estimated mixing water to test until the distance between the test bar and the bottom plate is 6mm 1mm, and the mixing water used at this time is the water consumption of standard consistency cement. Pay attention to complete the test within the specified time, and try to put water and cement at the bottom of the pot.
2. Cement setting time.
Put the cement paste with standard consistency into the test mold on the glass plate at one time, tamp and vibrate it, and then cure it. After adding water for 30 minutes, make the first measurement, so that the initial setting needle drops to the surface of the cement paste, suddenly release the needle and make it sink vertically into the cement paste. When the test needle stops sinking, observe the reading of the pointer. The initial setting time is the time from adding water to the time when the test needle sinks into clean mud and is 4 mm 1 mm away from the bottom plate. After initial setting, rotate the test mold with the slurry and put it on the glass plate to continue curing until the final setting needle sinks into the clean slurry for 0.5mm, and the time required after adding water is the final setting time. The qualified standards for initial setting of cement are all ≥45min, P? I、P？ Ⅱ cement final set qualified standard ≤390min； or less; Other qualified standards for final setting of cement are ≤600min. During the test, the vibration of the test mold should be prevented; When measuring the initial setting, the sinking position should be ≥ 10mm from the inner wall of the test mold. Don't let the needle return to the original horizontal position every time you measure. Wipe the test needle after each measurement and continue to keep the specimen.
3. Cement stability.
There are Reyes method (standard method) and cake test method (alternative method) to determine the stability. Reyes method is to put the cement slurry with standard consistency into Reyes clamp on the glass plate for molding at one time, take off the glass plate after curing, record the distance between the tips of two pointers in Reyes clamp at this time, and then boil it. After boiling, after the boiling box is cooled to room temperature, take out the Raytheon clamp, measure the distance between the tips of two pointers of the Raytheon clamp, and subtract the distance twice to get the expansion value. When making two specimens by this method, when the average expansion of the two specimens is less than ≤5.0mm and the difference between them is less than 4.0 mm, the cement stability is qualified. In this experiment, we should pay attention to the effectiveness of Reyes clamp and read the values accurately.
4. The strength of cement mortar.
Test the strength of cement at all ages to determine the strength grade; Or known strength grade, and check whether the strength meets the specification requirements. It is an important index to test the quality of cement. Firstly, mortar was prepared according to the ratio of L cement, 3 standard sand and half water (P? Standard & Poor's? P、P？ f、P？ C cement water consumption is determined by water cement ratio of 0.5 and mortar fluidity ≥ 180mm). After stirring in a stirring tank, it was molded, and after curing for 24 hours, the mold was removed, and after curing again at each test age, bending and compressive strength tests were conducted. The test results of all ages are not lower than the corresponding standards. In this test, it should be noted that the temperature and humidity of the molding laboratory and curing box meet the specification requirements; When curing, the scraping surface of the specimen should be upward and placed horizontally, and the six surfaces of the specimen should be in contact with water and have a distance from each other; Maintain the water level in the curing container. During the curing period, all curing water cannot be replaced, and different types of cement samples cannot be cured in the same container. Test equipment shall be effective; Bending and compression tests are carried out at the center of the sample at a specified rate and at a uniform speed.
5. Cement fineness. It is an optional indicator (omitted).
Second, the cement chemical index detection
1. Determination of insoluble matter.
Put the weighed sample in a beaker, add distilled water, stir and add hydrochloric acid solution for treatment, then dilute it with boiling hot water and heat it in a steam water bath for 65438±05min, then filter it with medium-speed quantitative filter paper, then treat the filtered insoluble residue with sodium hydroxide solution, neutralize it with hydrochloric acid, and fully wash it with hot ammonium nitrate solution after filtration. The residue is burned to constant weight at high temperature, and its value is the mass of insoluble matter. The ratio of insoluble matter mass to sample mass is the percentage of insoluble matter. p？ I when the value is less than or equal to 0.75%, the cement is qualified; p？ When this value is less than or equal to1.50%, Ⅱ cement is qualified.
2. Determination of ignition loss.
Put the weighed sample into a crucible that has been burned to a constant amount, and burn it in a muffle furnace at 950 25℃ to drive away water and carbon dioxide, and at the same time oxidize the existing oxidizable elements. Take out the crucible, put it into a dryer, cool and weigh it, and repeatedly burn it to a constant weight. The ratio of weightlessness to sample mass is the loss on ignition. p？ I when the value is less than or equal to 3.0%, the cement is qualified; p？ Ⅱ cement is qualified when the value is less than or equal to 3.5%; p？ O When the value is ≤5.0%, the cement is qualified.
3. Determination of sulfur trioxide.
In acidic solution, precipitate sulfate with barium chloride solution, stand for 12-24h, filter with slow quantitative filter paper, and wash with warm water until there is no chloride ion. Move the sediment and filter paper into a crucible, put it into a muffle furnace at 800 ~ 950℃ and burn it to a constant weight, weigh it in the form of barium sulfate, and the determination result is converted into SO3 content. p？ I、P？ ⅱ、P？ O When the value is ≤3.5%, the cement is qualified; p？ When the value is less than or equal to 4.0%, S cement is qualified; p？ P、P？ f、P？ When the value is ≤3.5%, the cement is qualified.
4. Determination of magnesium oxide.
Melt the sample with NaOH, and then prepare a solution with PH 10. Triethanolamine and potassium sodium tartrate were used as masking agents, and acid chrome blue K- catechol green B mixed indicator was used to titrate the total calcium and magnesium with EDTA standard solution. Deduct the volume of EDTA standard solution consumed when titrating calcium oxide and calculate the content of magnesium oxide. p？ I、P？ ⅱ、P？ O When the value is ≤5.0%, the cement is qualified; p？ s？ When the value is ≤6.0%, the cement is qualified; p？ P、P？ f、P？ When the value is ≤6.0%, P cement is qualified.
5. Determination of chloride ion. For the determination of constant chloride, thiocyanate volumetric method is generally used; Ion selective electrode method and rapid distillation-mercury titration method are commonly used to determine trace chloride. Rapid distillation-mercury titration is to decompose the sample with hydrogen peroxide and phosphoric acid at the temperature of 250℃~ 260℃ with a designated distillation device. Using purified air as carrier, chloride ions were separated by distillation. Dilute nitric acid is used as absorption solution, and when the pH value reaches about 3.5, diphenylazocarbohydrazide is used as indicator, and mercury nitrate standard solution is used for titration. Samples with chloride ion content ≤0.06% are qualified.
6. Determination of alkali content. It is an optional indicator (omitted).
Three, the influencing factors of cement quality inspection analysis and control points
1. Instrument factors and control methods.
Laboratory cement testing equipment is the basic link to test and evaluate cement quality. The quality of equipment and the accuracy of technical parameters will affect the accuracy of the test. For example, if the size of mortar test die is deviated, the level of shaking table device will cause uneven strength of specimen; If the bending machine device is not horizontal, the press can not be zeroed, and the test value will be distorted; The gap between the agitator blade and the boiler wall is large, resulting in uneven density of mortar; The temperature and humidity of curing box can not be controlled, which will affect the hydration, coagulation and hardening of cement and directly affect the test results. Therefore, the laboratory should fully understand the performance of equipment and instruments, master the use methods and skills, install them correctly, and do a good job in the maintenance of equipment and instruments. Pay attention to the daily operation inspection of equipment and instruments, regularly test and correct the accuracy of equipment and instruments, regularly send them for inspection and ask the metrology department to conduct on-site verification, and timely repair or update unqualified equipment and instruments to minimize the influence of equipment and instruments on the test results.
2. Environmental factors and control methods.
The external test environment, such as temperature and humidity, air pressure and airflow, will have certain influence on the test results. For example, the sensitivity of electronic detection equipment will fluctuate due to seasonal changes, leading to the deviation of detection data; It will also make all kinds of materials, materials and related equipment used in the test fail to reach the test temperature required by the specification, thus affecting the accuracy of the test data; The airflow will drift the number of the electronic balance, resulting in inaccurate weighing; The change of air pressure will affect the measurement of specific surface area and so on, thus indirectly affecting the test results. Therefore, we must strictly abide by the standard conditions stipulated in the test, and reduce the influence of the environment on the test results through reasonable operation, storage, maintenance and manual adjustment.
3. Operating factors and control methods.
Due to improper operation by testers, the experimental data will not be representative if they do not follow the test specification procedures; If the negative pressure screen coefficient is not corrected regularly, the screen residual value will be distorted; When curing, the test die is not placed horizontally, which will cause deformation or slurry flow of the specimen; There is no oil seal around the test mold, which will cause mud leakage; The specimens were not correctly marked in the process of molding, curing and testing, which led to the dislocation of different groups of specimens; During testing, equipment and instruments forget to zero, resulting in invalid testing data; After the test, the accuracy of cement detection will be affected by the incorrect values of a large number of discrete data and the lack of timely re-inspection. In addition, due to individual differences, different operators use the same samples and operation methods, and the test results will not be exactly the same. To sum up, the laboratory must strengthen the training and management of personnel, strictly require the testers to operate according to the specifications and design requirements, and fix a number of excellent and stable operators.
Fourth, the quality evaluation of cement
According to the test results of physical and chemical indexes of cement, cement can be divided into qualified products and unqualified products according to quality.
1. Qualified products. Cement can be judged as qualified when other indexes except alkali content, specific surface area and fineness meet the requirements of GB 175-2007. This cement can be used normally according to the design requirements.
2. Unqualified products. Cement is judged to be unqualified when other indicators except alkali content, specific surface area and fineness do not meet the requirements of GB 175-2007. Unqualified cement can reduce the standard use in construction projects. If the strength index is unqualified, the label can be reduced or used in the secondary stress part of the project.
In short, cement inspectors must master the methods and key points of cement inspection, operate in strict accordance with the specifications, reduce the errors caused by instruments, equipment, environment and human factors, improve the inspection quality, accurately and timely provide real and effective inspection data for the construction site, and ensure the quality of construction projects.
References:
[ 1] GB 175-2007。 Standard for ordinary portland cement.
[2] GB/T 176-2008。 Chemical analysis of cement.
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