Building Materials Cement Paper

Among the building materials, cement is a very common and familiar building material in daily life. The following is a sample essay on building materials cement that I compiled for you. I hope it will be helpful to everyone. You are welcome to read and refer to it!

Building Materials Cement Paper 1

Trial Discussion Key Issues in the Detection of Cement in Construction Raw Materials

Abstract With the continuous advancement of science and technology in our country, the development of the construction industry can be said to be rapid, and building materials have also achieved a large degree of performance in the development of science and technology in the industry. Innovation in materials, among building materials, cement is a very common raw material for construction projects, but its role in construction projects cannot be ignored. It can be said that cement can improve concrete to some extent. The quality and life of the structure have different effects. It can be seen that whether the quality of the cement itself is qualified or not is very important to users, and the test that can accurately determine the quality of cement is testing. Only through testing can the quality of cement raw materials be effectively guaranteed and avoid inaccuracies. Qualified products are mixed into construction projects. The author of this article starts with the cement in construction raw materials and discusses the key issues in cement testing. It will have a good promotion effect on the cement testing of construction raw materials and further ensure the quality of cement.

Keywords construction raw materials; cement; testing; discussion

Introduction:

When it comes to cement in the construction industry, most people will not be aware of it. Strange, but from the perspective of the construction engineering profession, cement is not only used as a raw material to participate in building concrete structures, but its own performance also has an invisible impact on the overall quality and performance of the concrete structure. Therefore, in construction, ensuring cement quality and testing cement quality through testing is a very important task.

1. Overview of the theory of cement

Cement is a very common and familiar building material in daily life. It is used in building houses, structures or other aspects. cement. From the perspective of building materials, the definition of cement is relatively broad. Once it is finely ground into powder, it can become a plastic slurry after reacting with water. It can not only harden in the air, but can also be obtained in water. Hydraulic cementing materials that harden and can firmly bind sand, gravel and other aggregates together are collectively called cement.

Although from the definition of cement, cement is a building material that does not seem difficult to understand, and most people have the impression that the prerequisites for being defined as cement are not stringent, but in fact this is not the case. As a very important raw material in construction projects, it also has some properties and characteristics suitable for construction projects, such as stability, fineness modulus, etc. These inherent characteristics of cement not only allow cement itself to be used in concrete structures Give full play to its good positive properties, and these properties are also important references in cement testing tests.

From the perspective of the development and innovation of modern building materials, cement has also been divided into many categories. Usually cement can be divided into ordinary cement, special cement and special cement according to its use and performance; according to the name of its hydraulic substance, it can be divided into Portland cement, aluminate cement, sulfoaluminate cement, ferroaluminate cement, etc.; According to technical characteristics, cement can be divided into fast-hardening cement, hydration heat cement, sulfate-resistant cement, expansion cement and high-temperature resistant cement. These classifications of cement according to different standards also reflect some inherent characteristics of cement itself to some extent. These characteristics further illustrate the importance of cement testing and the negative effects of unqualified cement quality on construction projects.

2. Factors affecting the detection of construction raw materials cement

Since the implementation of the new standards for construction projects, many construction companies have only made simple modifications to the maintenance pools without conducting scientific research. The test conditions have been improved and modified. The molding chambers of some companies have high temperatures, even reaching 28°C, and the temperature and humidity in the curing boxes cannot meet the relevant standard requirements. Some companies also use self-made curing boxes, but only carry out The production is relatively rough, and the temperature and humidity control devices and monitoring measures are relatively lacking. As a result, the temperature and humidity cannot be effectively controlled during the maintenance period, which has a greater impact on the accuracy of the inspection. Specifically, it can be understood from the following aspects.

1. Measuring instruments

Measuring instruments for testing construction raw materials and cement, such as weighing balances, thermometers, hygrometers, water dispensers, etc., are included in relevant test and testing standards There are clear regulations on their accuracy and other aspects. However, judging from the actual testing survey data, there are still some laboratories that still use low-precision measuring instruments, which will virtually reduce the detection efficiency. accuracy and varying degrees of impact on detection results. For example, some inspection rooms use water-adding vessels with an accuracy of 5 mm or 2 mm. This makes it impossible to accurately measure the amount of water and cement added, which has a great impact on the water-cement ratio and lime-sand ratio of cement mortar. .

2. Mold trial

Mold trial is mainly for cement strength test. In the relevant standards and specifications for test testing, the material, size and assembly accuracy of the trial mold are There are strict and specific regulations. However, in the implementation of specific test regulations, some testing laboratories did not attach great importance to their test mold regulations. The main manifestations are that the size of the test mold is far from the normative standards, and the assembly accuracy is also low. It failed to meet the corresponding standards for cement strength testing. During the implementation of the test and testing, although the relevant self-calibration procedures were also performed, there were still too many loopholes and defects.

3. Molding equipment

Generally speaking, mixers and vibrating tables are the main molding equipment. For mixers, they need to be combined with relevant equipment after a period of time. According to the standard requirements, the gap between the mixer and the mixing pot is adjusted. The vibration table generally needs to be observed and maintained regularly to ensure that it meets the relevant molding standards. In addition, cement testing will also be affected by human factors. The habits of human operations and the different effects of different human interferences will have various impacts on cement-related testing and testing.

3. Discussion on key issues in the testing of cement in construction raw materials

1. The first step in the testing of cement raw materials is the sampling and testing work before cement purchase, that is, Said, but when the construction raw material cement is ready to enter the site, the test personnel need to take samples and seal them, and then send them to the laboratory or other testing institutions for testing. At the same time, in order to carry out the follow-up work smoothly, the cement samples need to be stored for three consecutive months. for a long time. In addition, when purchasing testing instruments and related equipment, it is necessary to calibrate them in advance. When testing related items on cement, if you want to get more accurate test conclusions, you must first ensure that the testing instruments are in good condition. accuracy and accuracy, so as to ensure the quality of the conclusions of cement testing from the prerequisites.

2. There must be suitable testing conditions: for example, before the test, cement materials and water need to be put into the molding chamber, and its temperature should be measured scientifically to ensure a uniform temperature, and the measurement results should be recorded ; In the curing box, the temperature of the cement needs to be adjusted reasonably, and the method used is to automatically control 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 comparative testing: among the relevant standards in my country, the production requirements for standard sand are relatively high and have relatively expensive prices. In a region, there are There are fewer sellers, and standard sand needs to be purchased from formal channels, and when purchasing, the standard sand certificate and the merchant's authorization also need to be obtained.

4. Test the fineness of cement: In the test of cement fineness, the sieving method can be applied, using very small holes, and using the mass percentage of the sieved residue to determine the fineness of the cement. Indicates the fineness of the cement sample, which may clog the sieve holes during actual practice. Therefore, after the sieve has been used for more than ten times, the test sieve needs to be cleaned to ensure that it is clean and smooth enough, so that the accuracy of the results can be significantly improved.

5. The specific amount of water used to detect the viscosity of cement: If the amount of water is fixed, then if the mixing water used is about 142 ml, 500 g of cement needs to be added, and Stir their mixture in the mixing pot; after completing the mixing process, it is necessary to put the cone mold in the slurry machine, and do the cement tamping and vibration scraping. The smoothing process is carried out last, and the test cone sinks. The depth is measured; usually, if the cement dosage is increased, the strength of the mixture will be increased, and the shrinkage of the material will also be improved; in the process of mixing the mixture, only a smaller dosage of cement is added.

4. Conclusion

As one of the most widely used construction raw materials, cement plays an important role. It is self-evident that the quality of cement in construction raw materials is qualified or not. , will have some adverse negative effects on the concrete structure of the construction project and the entire construction project. Therefore, quality control of cement in construction raw materials through testing and testing is essential and very important work. It is of great significance to accurately identify the quality of cement and ensure the quality of construction projects.

References:

[1] Wen Wei, Zhang Guanbin. Analysis of cement testing elements in construction engineering testing [J]. Building Materials and Decoration, 2012(12): 88

[2] Huang Huajun. Cement testing elements in construction engineering testing [J]. Construction Industry, 2013(5): 67

Paper on Building Materials Cement 2

A brief discussion on the key issues in the detection of cement in construction raw materials

Abstract: At present, with the rapid development of our country’s economy and the construction of a harmonious society, people’s living standards have also been continuously improved. The industry is also developing rapidly. At the same time, the construction industry is also facing the problem of improving construction quality. As we all know, the quality of the building determines the safety of the people living there, and if we want to ensure the quality of the building, we must ensure the building materials. In construction projects, cement is one of the most important raw materials in building materials. If the quality of the cement is not up to par, it will reduce the stability and service life of the entire building. Therefore, during the construction of construction projects, we must strengthen the testing of cement to ensure that the quality of cement meets relevant regulations so that the construction project can proceed smoothly.

Keywords: construction raw materials; cement testing; key issues; sampling; improvement

Introduction

Cement is one of the most common and important raw materials in construction projects. one. During the construction process, we usually mix water, sand and cement to form cement concrete, which can be used in building construction. With the rapid development of my country's construction industry, the use of cement concrete in building construction in China is becoming more and more common. The reason why cement concrete is better than many raw materials and is reused in construction projects is mainly because cement concrete has the following advantages: high strength, good pressure resistance, heat resistance, wear resistance, etc. Cement, as the primary raw material in cement concrete, plays an important role in the construction of construction projects and plays an irreplaceable role.

1. The necessity of cement testing

Since cement is one of the most important and common raw materials in building materials, people attach great importance to the testing of cement. The quality of cement not only affects the construction of the project but also affects the later planning of the project throughout. However, there are still some problems in today's cement testing work.

Every step in cement testing, such as "selecting equipment and debugging equipment", "cement extraction and storage", etc., play a decisive role. If there is an error in any link, it will affect the overall situation. Just like the saying in classical Chinese, "A slight mistake can lead to a thousand miles of error." Any tiny problem in the cement testing work will cause the failure of the entire project. Therefore, the necessity of cement testing is self-evident.

2. Influencing factors in cement testing

(1) Factors regarding instruments and equipment

It is difficult to distinguish the authenticity of the manufacturers of cement testing instruments and equipment, so In the process of purchasing instruments and equipment, we must pay strict attention to the quality issues of the instruments and equipment. Before choosing to purchase, relevant purchasing personnel must have a full understanding of the supplier. The best way is to establish a special supplier file. The files should cover these aspects: whether the product quality of the instruments and equipment provided by the supplier meets relevant national standards; the supplier's quality supply capabilities, and whether the products meet the technical requirements of the testing standards; whether the supplier can guarantee timely and accurate supply. ; Whether the supplier can deal with equipment quality issues in a timely manner; relevant information about the supplier's instrument and equipment quality management system, etc. Only by establishing such a supplier file can the quality of the purchased instruments and equipment be guaranteed and the detected data truly accurate.

(2) Factors regarding artificial sampling

We must test the cement in accordance with the relevant regulations on testing work. Under normal circumstances, the acceptance work of cement quality during delivery is divided into: There are two types of inspection: sample inspection based on the actual product and inspection report based on the manufacturer's cement number. However, the actual situation is different from the general situation. When the cement testing was carried out at the construction site, the testing process did not strictly follow the relevant provisions of the testing specifications. For some reasons, the buyer and the seller also did not strictly follow the relevant regulations of the cement testing specifications. This made Sampling at construction sites has been questioned.

(3) Factors related to the test environment

In the process of cement testing, in addition to the above two points, the test environment is also an important factor affecting the testing. When testing cement, the testing personnel must set up and control the testing environment in strict accordance with the requirements of the testing standards. In addition, the configuration monitoring and temperature and humidity during the testing process must be recorded, so as to strictly and effectively monitor the test environment and obtain true and accurate test results.

3. Key points of cement testing

(1) Before testing the cement, you must take a sample first

Before testing the cement, you must first take a sample. Seal the sample in a container, label it, and store the sample for three consecutive months so that subsequent testing can be carried out better, and then send it for testing in a timely manner. In the process of purchasing testing instruments and equipment, it is necessary to accurately calibrate the equipment and instruments on site and conduct market research at the same time. This is because only by ensuring the quality of instruments and equipment can cement be accurately tested.

(2) The testing conditions must be appropriate

For example, before the test, appropriate testing conditions must be selected, cement materials and water must be put into the molding chamber, and then Detect its temperature at reasonable times and scientifically, so that it has a uniform temperature, and record the measurement results at the same time. Temperature is directly affected by the accuracy of detection. In the curing box, the temperature of the cement should be reasonably and scientifically adjusted by automatically controlling the temperature and humidity. Air conditioning can even be used to indirectly control the water temperature. Currently, with the rapid development of science and technology, more and more cement temperature control equipment has appeared, especially automatic control system equipment, which reduces or even avoids the occurrence of human detection errors and has high economic benefits.

(3) Use certain standard materials and do comparative testing

my country’s relevant standards for cement testing have very high requirements for the production of standard sand. Because the price of standard sand is relatively expensive, and there are few sellers of standard sand in a region. This requires us to more strictly control the purchasing channels of standard sand, and during the procurement process, we must also pay attention to obtaining the certificate of standard sand and the authorization letter from the merchant.

(4) Testing the fineness of cement

We can use the screening method to test the fineness of cement. We will use very small holes and use the mass percentage of the remaining material to express the fineness of the cement sample. However, imagination does not equal reality. In actual practice, the screen holes may be blocked during the screening process. Then a problem arises. If the sieve holes are blocked and the time of sieving analysis is limited, the results of sieving analysis will be greatly affected. Therefore, we must promptly clean the test sieves that have been screened for more than ten times to ensure that they are clean and smooth, thereby improving accuracy.

(5) Water consumption for testing cement viscosity

If the water volume is fixed, then if the mixing water used must be controlled at about 142 liters, 500g needs to be added Mix the cement on the left and right sides in a mixing pot to form a mixture. After the mixing is completed, a cone mold should be placed in the pulp purifier, and the cement should be pounded and vibrated to smooth it. Finally, smoothing work is carried out, and then the depth of the test cone mold is accurately measured. When measuring the depth of the cone sinking, it needs to be ensured that it does not exceed 3".

IV. Methods to improve the detection of cement materials

(1) Strengthen the control of detection instruments

Testing equipment and instruments play an indispensable role in cement testing. Therefore, an effective way to improve cement material testing is to strengthen equipment control. Before using the equipment, it must be inspected and adjusted regularly and soundly. Improve the equipment testing system. Relevant testing personnel must send equipment to the testing department for testing in a timely manner to prevent problems with the equipment itself from affecting the testing work. In addition, when the equipment is found to be inaccurate, it must be calibrated in a timely manner. p>

(2) Implement cement testing in accordance with regulations

Testing personnel must ensure that the cement testing data meets the national cement testing standards, test in accordance with relevant testing procedures, scientifically and reasonably reduce errors, and make the data accurate , reliable. For inspection personnel who are not familiar with the inspection process, they should be provided with intensive training to improve the inspection technology and quality of the inspection personnel.

(3) Pay attention to the supervision and management of cement stability testing

In the process of cement testing, attention should be paid to the testing of cement stability and strength. For the testing of cement strength and stability, regular inspection and management of the instrument should be carried out according to the number of times it is used, and problems that arise should be reported in a timely manner. Solve. Problems such as low accuracy of testing instruments must be updated in a timely manner.

Conclusion

In summary, the test and inspection work of construction projects is the key to quality in the construction process. An indispensable part of control is also a very important part of the completion acceptance assessment. The detection of cement materials can reduce or even avoid the occurrence of building construction accidents. This prevention of testing cement components can improve the quality of construction. It provides guarantee for the property safety of our residents.

References

[1] Yin Na. Analysis of key points in the cement material testing process [J]. Sichuan Cement, 2015, 04: 12.

[2] Xiao Hong, Li Jialei. Discussion on key issues in the detection of cement in construction raw materials [J]. Heilongjiang Transportation Science and Technology, 2015, 05: 174.

[3] Han Zhixin. A brief discussion on the detection of construction raw materials [J]. Jilin Agriculture, 2012, 11: 253.

[4] Zhang Zhijun. Research on quality control of concrete raw materials [D]. Hebei University of Technology, 2014.

[5 ]__ Yong. Analysis of cement testing in construction engineering testing [J]. Doors and Windows, 2014, 08: 116.

[6] Tai Haijun. Influencing factors and quality control of cement testing[J]. Sichuan Cement, 2015, 09: 9.

Paper 3 on Construction Materials Cement

Talking about Quality Testing of Construction Cement

Abstract: The article focuses on physical indicators and chemical indicators These two aspects introduce the key points of testing indicators and testing methods of construction cement, explain the factors that affect cement quality testing, and point out the control methods.

Keywords: cement; physical and chemical indicators; detection; influencing factors; control; evaluation

Cement is one of the essential basic raw materials in construction, and the quality of cement is crucial to The quality of construction projects has a huge impact. Therefore, strengthening the testing of cement quality is of great significance to ensuring the quality of construction projects. The following author will start from the description of cement testing methods, summarize the influencing factors in cement testing, and discuss measures and methods to improve cement quality testing.

1. Detection of cement physical indicators

1. Water consumption for cement standard consistency.

By measuring the water consumption when the cement paste reaches the standard consistency, it is used as the standard for cement setting time and stability test water consumption. During the test, first pour the estimated amount of mixing water into the moistened mixing pot, and then pour 500g of cement sample. Immediately after stirring, put the clean slurry into the test mold on the glass plate at one time. After smoothing it with vibration and smoothing, quickly put the test mold and the plate on the Vicat instrument. Lower the test rod to the surface of the clean slurry and tighten the screws. Relax and let the test rod sink vertically and freely into the clean slurry. Record the distance between the test rod and the bottom plate when it stops sinking. Repeat the test with different estimated amounts of mixing water until the pure slurry when the distance between the test rod and the bottom plate is 6 mm ± 1 mm is the standard consistency pure slurry. The amount of mixing water used at this time is the standard consistency water consumption of cement. When testing, be sure to complete it within the specified time and try to put water and cement at the bottom of the pot.

2. Cement setting time.

Put the cement slurry of standard consistency into the test mold on the glass plate at one time, and then maintain it after smoothing it with vibration and vibration. The first measurement is performed 30 minutes after adding water, and the initial setting needle is allowed to drop. Reach the surface of the clean slurry and suddenly relax so that the needle sinks vertically and freely into the clean slurry. Observe the reading of the pointer when the test needle stops sinking. The time required from the time when water is added to when the test pin sinks into the pure slurry and is 4mm ± 1mm ??away from the bottom plate is the initial setting time; after the initial setting, turn the test mold and slurry over and place them on the glass plate to continue curing until the final setting pin sinks. Calculated when 0.5mm is inserted into the pure slurry, the time required from the time of adding water is the final setting time. The qualification standard for the initial setting of all cements is ≥45min, the qualification standard for the final setting of P?I and P?Ⅱ cement is ≤390min; the qualification standard for the final setting of other cements is ≤600min. During the test, the test mold must be prevented from being vibrated; when measuring initial setting, the sinking position of the needle must be ≥10mm from the inner wall of the test mold. The needle cannot be allowed to fall into the original side position for each measurement. The test needle must be wiped clean after each measurement and the test piece must continue to be maintained.

3. Cement stability.

The stability determination methods include Ray's method (standard method) and cake test method (substitute method).

The measurement by Ray's method is to put the standard consistency cement slurry into the Ray's clamp on the glass plate at one time. After curing, remove the glass plate, record the distance between the two pointer tips of the Ray's clamp at this time, boil it, and wait until it is boiled. Cool the boiling box to room temperature, take out the Ray's clamp, measure the distance between the two pointer tips of the Ray's clamp, and subtract the two distance measurements to obtain the expansion value. Use this method to make two test pieces. When the average expansion of the two test pieces is ≤5.0mm and the difference between them is ≤4.0mm, the cement stability is qualified. In this experiment, attention should be paid to the effectiveness of the Ray's clamp and accurate readings.

4. Strength of cement mortar.

Test the strength of cement at each age to determine the strength grade; or if the strength grade is known, check whether the strength meets the specification requirements. It is an important indicator for testing cement quality. During the test, first prepare mortar (P? S, P Fluidity ≥180mm to determine). After stirring in a mixing pot, it is formed. After curing for 24 hours, the mold is removed. After curing again to each test age, bending and compressive strength tests are conducted. If the test results of each age are not less than the corresponding specification requirements, it is qualified. In this test, attention should be paid to the temperature and humidity of the molding laboratory and the curing box to meet the specification requirements; during curing, the scraping surface of the specimen should be facing up and placed horizontally. The six sides of the specimen should be in contact with water and spaced apart from each other; maintain the water level in the curing container. And during the curing period, all curing water cannot be replaced, and different types of cement samples cannot be cured in the same container; the test equipment must be effective; the flexural and compressive tests must be carried out at a prescribed rate and at a uniform speed in the center of the specimen. load.

5. Cement fineness. It is a selective indicator (omitted).

2. Detection of cement chemical indicators

1. Determination of insoluble matter.

Place the weighed sample in a beaker, add distilled water, stir and add hydrochloric acid solution for treatment, then dilute it with near-boiling hot water, place it in a steam water bath and heat it for 15 minutes, and then filter it with medium-speed quantitative filter paper , the filtered insoluble residue is then treated with sodium hydroxide solution, neutralized with hydrochloric acid, filtered and fully washed with hot ammonium nitrate solution, the residue is burned at high temperature to a constant weight and weighed, the value is the mass of the insoluble matter . The ratio of the mass of insoluble matter to the mass of the sample is the percentage of insoluble matter. P?I cement is qualified when the value is ≤0.75; P?Ⅱ cement is qualified when the value is ≤1.50.

2. Determination of loss on ignition.

Place the weighed sample into a crucible that has been burned to a constant weight, and burn it in a muffle furnace at 950±25°C to drive out moisture and carbon dioxide, and at the same time remove the easily oxidized elements. Oxidation. Take out the crucible and place it in a desiccator, cool and weigh, and burn repeatedly until the weight is constant. The ratio of the lost mass to the mass of the sample is the loss on ignition. P?I cement is qualified when the value is ≤3.0; P?Ⅱ cement is qualified when the value is ≤3.5; P?O cement is qualified when the value is ≤5.0.

3. Determination of sulfur trioxide.

In acidic solution, use barium chloride solution to precipitate sulfate, let it stand for 12-24 hours, filter with slow quantitative filter paper, and wash with warm water until no chloride ions are detected. Move the sediment and filter paper into a crucible, place it in a muffle furnace at 800°C to 950°C and burn it to constant weight. Weigh it as barium sulfate and convert the measurement results into SO3 content. P?I, P?Ⅱ, P?O cement is qualified when the value is ≤3.5; P?S cement is qualified when the value is ≤4.0; P?P, P?F, P?C cement is qualified when the value is ≤3.5.

4. Determination of magnesium oxide.

The sample is melted with NaOH, and then a solution of pH 10 is prepared, using triethanolamine and potassium sodium tartrate as masking agents, using acid chromium blue K-tetraphenol green B mixed indicator, and titrating with EDTA standard solution The total amount of calcium and magnesium, after deducting the volume of EDTA standard solution consumed when titrating calcium oxide, calculate the content of magnesium oxide. P?I, P?Ⅱ, P?O cement is qualified when the value is ≤5.0; P?S?A cement is qualified when the value is ≤6.0b; P?P, P?F, P?P cement is qualified when the value is ≤6.0b qualified at the time.

5. Determination of chloride ions.

For the determination of constant chloride, the thiocyanate volumetric method is generally used; for the determination of trace chloride, the ion selective electrode method and the rapid distillation-mercury salt titration method are often used. The rapid distillation-mercury salt titration method uses a prescribed distillation device to decompose the sample with hydrogen oxide and phosphoric acid at a temperature of 250°C to 260°C. Using purified air as a carrier, chlorine ions are distilled and separated. Use dilute HNO3 as the absorption liquid. When the pH reaches about 3.5, use diphenyl azocarbon hydrazide as the indicator and titrate with mercury nitrate standard solution. The sample is qualified if the chloride ion content is ≤0.06C.

6. Determination of alkali content. It is a selective indicator (omitted).

3. Analysis of factors affecting cement quality testing and key points of control

1. Instrument factors and control methods.

Laboratory cement testing instruments and equipment are the basic link in testing and evaluating cement quality. The quality of the equipment and the accuracy of the technical parameters will all affect the accuracy of the testing. For example, the size of the mortar test mold is biased, and the vibration table device is not level, which will cause uneven strength of the test piece; the anti-folding machine device is not level and the press cannot be zeroed, which will distort the test value; the gap between the mixer blade and the pot wall is large, resulting in The density of the mortar is uneven; the temperature and humidity of the curing box cannot be controlled, which will affect the hydration, coagulation, hardening, etc. of the cement, which will directly affect the test results. Therefore, laboratories should fully understand the performance of equipment and instruments when purchasing, master the usage methods and techniques, install them correctly, and do a good job in maintaining and maintaining the 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 submit them for inspection and ask the metrology department for on-site verification, repair or update unqualified equipment and instruments in a timely manner, and minimize equipment and instrument factors for inspection The impact of the results.

2. Environmental factors and control methods.

External test environments such as temperature, humidity, air pressure, and air flow will have a certain impact on the test results. For example, due to seasonal changes, the sensitivity of electronic detection equipment will fluctuate, resulting in detection data deviation; it will also cause the various materials used in the test, and the materials and the equipment involved, to fail to uniformly reach the detection temperature required by the specification, thus affecting Check the accuracy of the data; air flow will cause the digital balance of the electronic balance to drift, causing inaccurate weighing; changes in air pressure will affect the measurement of specific surface area, etc. These will indirectly affect the test results. Therefore, the standard conditions specified in the test must be strictly observed during the test, and the impact of the environment on the test results must be reduced through reasonable operation, storage, maintenance, and artificial adjustment.

3. Operating factors and control methods.

Due to improper operation by test personnel, such as not following the test specification procedures, the experimental data will be unrepresentative; if the negative pressure sieve coefficient is not regularly calibrated, the sieve residual value will be distorted; during maintenance, the test mold will not be placed horizontally, which will Cause deformation or slurry of the test piece; the test mold is not sealed with grease around, which will cause mud to seep out; the test pieces are not marked during molding, maintenance, and testing, causing different groups of test pieces to be interchanged; equipment during testing The instrument forgets to zero, causing the detection data to become invalid; after the test, the discrete and large data are not correctly measured, and there is no timely recheck, etc. These will affect the accuracy of cement detection. In addition, due to individual differences, if different operators use the same samples and operating methods, the test results will not be exactly the same. In summary, laboratories must strengthen personnel training and management, strictly require testers to operate in accordance with specifications and design requirements, and fix a team of highly skilled and stable operators.

4. Quality evaluation of cement

According to the test results of cement physical and chemical indicators, cement can be divided into two categories: qualified products and unqualified products according to quality.

1. Qualified products. In addition to the alkali content, specific surface area, and fineness, cement can be judged as a qualified product when other indicators can meet the requirements of the GB175-2007 standard. This type of cement can be used normally according to the design requirements.

2. Defective products. In addition to the alkali content, specific surface area, and fineness, if any other indicator of the cement does not meet the requirements of the GB175-2007 standard, it will be judged as unqualified.

Unqualified cement can be used at lower standards in construction projects. If the strength index is unqualified, the grade can be reduced or used for secondary stress-bearing parts of the project.

In short, cement testing personnel must be proficient in various methods and key points of cement testing, operate in strict accordance with the specifications, reduce errors caused by instruments, equipment, environment and human factors, improve testing quality, and provide better conditions for construction. Provide true and effective inspection data accurately and timely on site to ensure the quality of construction projects.

References:

[1] GB 175-2007. General Portland Cement Standard [S].

[2] GB/T176-2008 .Chemical Analysis of Cement[S].