Methods for studying and determining the quality of building materials. Abstract: Physico-chemical methods for studying building materials

Tax legislation, due to its significance for the state as a whole, has always been the subject of close attention all walks of life. Currently, increasing attention is being paid to resolving conflict situations arising during the implementation of tax law norms. The most promising direction for resolving this issue is the development of a pre-trial procedure for resolving tax disputes, which currently needs significant adjustment.

Thus, the following problems of pre-trial settlement of tax disputes in the practice of the Federal Tax Service of the Kalininsky region are identified:

1. Lack of real guarantees of measures to prevent and suppress violations of taxpayers’ rights.

2. Lack of legislatively established procedural powers of the taxpayer.

3. Lack of separation of arbitration and prosecutorial functions in the production and making of the final decision<2>.

Problems of resolving tax disputes:

1. Ineffectiveness of pre-trial procedures.

2. Appealing decisions of judicial authorities in the absence of prospects for resolving a tax dispute in favor of the tax authority.

3. Accrual of arrears at random.

4. Psychological pressure on judges.

5. Delaying trials.

6. Performing by courts functions that are not typical for them.

7. Use of non-legal arguments.

8. Implementation of illegal decisions by force.

9. Failure of tax authorities to comply with judicial acts.

10. Leaving the actions of tax authorities without evaluation.

11. Lack of understanding of market specifics.

12. Difficulties in obtaining interim measures<3>.

An analysis of the pre-trial procedure for resolving tax disputes provided for by the Tax Code of the Russian Federation suggests the need to make significant changes to tax legislation in order to increase the efficiency of out-of-court settlement of tax disputes.

1. Creation of special mechanisms used in the pre-trial settlement of tax disputes

Until January 1, 2009, the taxpayer has the right to appeal acts, as well as actions (inactions) of tax authorities and their officials, both to a higher tax authority and to the court (after this date, going to court will be possible only if the pre-trial procedure for resolving tax disputes is followed ). However, as practice shows, in most cases taxpayers prefer judicial resolution of a tax dispute.

Simply introducing mandatory pre-trial settlement of tax disputes is not a solution to the problem. The fact that the taxpayer, before going to court to protect his rights, will be forced to contact the tax authority in the pre-trial settlement of a tax dispute will not increase the efficiency of pre-trial settlement of tax disputes. It will be possible to speak about the effectiveness of the pre-trial procedure for tax disputes when the taxpayer himself strives to resolve the tax dispute in a pre-trial manner, and the number of appeals to the judicial authorities (or at least the number of court decisions made in favor of taxpayers) is significantly reduced.

It is possible to increase the efficiency of pre-trial settlement of tax disputes only by introducing new special tools used in the pre-trial settlement of tax disputes. Moreover, such tools can only be used in the pre-trial settlement of tax disputes and cannot be used during the judicial resolution of tax disputes.

One of the mechanisms for pre-trial settlement of tax disputes may be the vesting of the tax authority with special powers regarding the amounts to be recovered from the taxpayer. It's about about the institution called in criminal procedural law “bargain with justice”. Currently, the tax authority is deprived of any powers, using which the tax authority could “forgive” the taxpayer for certain violations and (or) amounts to be collected.

Of course, the introduction of such a mechanism requires detailed study, since it provides the tax authority with opportunities for broad discretion, abuse of law, and also creates fertile ground for corruption.

As a tool to prevent abuse when using this mechanism, we can propose the introduction of the following restrictions:

1. The use of a “transaction” between the taxpayer and the tax authority is possible only in controversial situations. The controversial nature of the situation is determined by the presence of opposing decisions of the courts (in similar cases considered earlier). Currently, an example of a controversial situation can be relationships with “non-existent” counterparties, i.e. organizations that were registered in violation of current legislation (using lost passports or for a fee), as well as organizations that do not submit tax reports. Analysis judicial practice allows us to say that the courts make decisions both in favor of the tax authorities and in favor of taxpayers<4>. However, tax authorities, regardless of establishing the fact of abuse on the part of the taxpayer (i.e., the fact that the taxpayer received an unjustified tax benefit), include episodes regarding relationships with these persons in decisions made based on the results of tax audits.

2. Determination of cases of controversial situation by a special subject who is not a party to the dispute.

We are talking about a special entity to which, in our opinion, the functions of pre-trial resolution of tax disputes should be transferred. That is, the issue of a “controversial situation” must be resolved by an independent person - a person who is not a party to the tax dispute.

Another additional mechanism used at the stage of pre-trial settlement of a tax dispute may be a change in the deadline for payment of taxes and fees, as well as penalties, provided for in Chapter. 9 of the Tax Code of the Russian Federation (hereinafter referred to as changing the tax payment deadline). Currently, the use of this mechanism in pre-trial consideration of a tax dispute is impossible due to direct instructions in the law. According to paragraphs. 2 p. 1 art. 62 of the Tax Code of the Russian Federation, the deadline for paying a tax cannot be changed if, in relation to the person applying for such a change, proceedings are being carried out in a case of a tax offense or in a case of an administrative offense in the field of taxes and fees, customs affairs in terms of taxes payable in connection with with the movement of goods across the customs border Russian Federation.

However, the use of a mechanism for changing the deadline for tax payment in the pre-trial settlement of a tax dispute will not only increase the interest of the controlled entity, but will also reduce the number of tax disputes referred to the court.

However, it should be noted that for this mechanism to be truly effective, it is necessary that the taxpayer cannot abuse it. To do this, it is necessary to introduce a restriction on the taxpayer going to court when using a “transaction”. This is not about limiting the taxpayer’s right to judicial protection. The taxpayer is faced with a choice: either the taxpayer makes a “deal” with the tax authority and does not voluntarily exercise his right to judicial protection; or the taxpayer uses his right of judicial protection, but in this case all “agreements” with the tax authority lose their force, and the court considers all violations identified during tax control activities.

2. Creation of a special entity that considers disputes pre-trial

The issue of the need to create a special entity authorized to consider tax disputes in a pre-trial manner is discussed in the scientific literature. At different times, various authors have drawn attention to the need to separate arbitration and prosecutorial functions when making and making a final decision against a taxpayer

It should be recognized that the existing procedure, when the final decision is made by the same body that identified the violations (even a higher one), cannot be considered as promoting objectivity in resolving disagreements that have arisen. The assessment of the effectiveness of the activities of the tax authority is carried out depending on the amount of taxes, fines and penalties accrued by tax authorities. It seems that in such a situation there are no incentives for the tax authority to “spoil” its own performance indicators by agreeing with the taxpayer’s position and reducing the amount of taxes, fines and penalties to be collected.

In this regard, in our opinion, it is advisable to transfer the powers to review and make the final decision based on the results of tax control measures to a special body that is not organizationally subordinate to the tax authorities.

It should be noted that attempts are currently being made to create an independent entity that considers tax disputes in a pre-trial manner.

Thus, tax audit units were created within the structure of territorial tax authorities. They are designed to perform the following functions.

In the departments of the Federal Tax Service of Russia for the constituent entities of the Russian Federation:

Consideration of complaints from individuals and legal entities against acts of lower tax authorities, actions (inaction) of their officials in connection with the exercise by tax authorities of the powers established federal laws, regulatory legal acts of the President of the Russian Federation or the Government of the Russian Federation, based on the results of consideration of which a decision is made;

Consideration of objections (disagreements) of taxpayers (tax agents, payers of fees) regarding acts of repeated on-site tax audits appointed and carried out by the department of the Federal Tax Service of Russia in the constituent entity of the Russian Federation, based on the results of which a document is prepared expert opinion about the validity (unsoundness) of the taxpayer’s arguments.

In the interregional inspections of the Federal Tax Service of Russia for the largest taxpayers:

Preparation, at the request of the Federal Tax Service of Russia, of conclusions on complaints;

Consideration of objections (disagreements) of taxpayers (tax agents, payers of fees) regarding acts of on-site tax audits appointed and carried out by the interregional inspectorate of the Federal Tax Service of Russia for the largest taxpayers, based on the results of which an expert opinion is prepared on the validity (unsoundness) of the taxpayer’s arguments.

In the inspections of the Federal Tax Service of Russia by districts, districts in cities, cities without district division, inspections of the Federal Tax Service of Russia at the interdistrict level:

Preparation, at the request of the Federal Tax Service of Russia for the constituent entity of the Russian Federation, of conclusions on complaints;

Consideration of objections (disagreements) of taxpayers (tax agents, payers of fees) regarding acts of on-site tax audits appointed and carried out by this inspectorate of the Federal Tax Service of Russia, based on the results of consideration of which an expert opinion is prepared on the validity (unsoundness) of the taxpayer’s arguments<6>.

<Более того, Распоряжением Федеральной налоговой службы от 1 сентября 2006 г. N 130 была принята Концепция развития налогового аудита в системе налоговых органов Российской Федерации <7>. This document states that the purpose of creating tax audit units in the system of tax authorities is to improve administrative procedures for the consideration of tax disputes and to establish the principles of legality in the law enforcement activities of tax authorities.

Indicators for assessing the effectiveness of the functioning of tax audit units are also established. These include, in particular:

1. The number of appeals to the arbitration court after negative consideration (dissatisfaction, partial dissatisfaction) of complaints in an administrative manner.

2. The number of appeals to the arbitration court to appeal non-normative acts of tax authorities related to the application of the legislation of the Russian Federation on taxes and fees, or other acts of legislation of the Russian Federation, control over the implementation of which is entrusted to the tax authorities, bypassing the administrative appeal procedure.

3. The number of eliminated violations of the application of legislation, control over compliance with which is entrusted to the tax authorities, based on the results of an internal departmental tax audit.

An analysis of the above functions of the internal audit service allows us to conclude that work is currently underway to increase objectivity when making decisions based on the results of consideration of complaints (disagreements) of the taxpayer.

However, the measures taken cannot be regarded as aimed at creating a special (independent) entity for the pre-trial settlement of a tax dispute due to the following reasons:

1. The Internal Audit Service is not an entity that considers tax disputes in a pre-trial manner. The specified division only prepares its conclusion on the complaint (disagreement) of the taxpayer, which (conclusion) is subsequently taken into account by the head (deputy head) of the tax authority. Moreover, it (the service) is not at all an independent subject of pre-trial settlement of a tax dispute, since it is only a structural unit of the tax authority.

2. Coordination of the work of tax audit units in terms of work on reviewing complaints is carried out by the heads of tax authorities<8>. That is, there is no sign of independence, the need for which was mentioned earlier. In our opinion, without being removed from organizational subordination to the tax authority, the subject of pre-trial settlement will not have independence (objectivity) when making a decision based on the results of consideration of a tax dispute.

3. The activities of the internal audit service (even in the form in which it currently exists) are not regulated at the legislative level. Despite the fact that in the course of their activities, internal audit specialists enter into relationships with taxpayers (in particular, during a meeting of the commission reviewing tax audit materials). Currently, there is no full-fledged regulatory legal act establishing the legal status of the internal audit service. Those acts that exist were adopted at the by-law level, have not been published and regulate the activities of this service in fits and starts.

The issue of creating a special entity for the pre-trial settlement of tax disputes requires a fundamental solution, namely the creation of an independent (independent) body that will be entrusted with the function of resolving a tax dispute in a pre-trial manner.

It seems that the new subject of pre-trial settlement of tax disputes must meet two main requirements.

Firstly, the special body should not be organizationally subordinate to the tax authorities. In this regard, one should agree with the opinion of A.S. Zhiltsov, who notes that the current management system for resolving tax disputes at the pre-trial stage should be taken beyond the scope of the tax authority, i.e. structures of the Federal Tax Service. This body could function as a corresponding separate division or service within the structure of the Ministry of Finance of the Russian Federation.

This is advisable taking into account the functions and powers of the Ministry of Finance of the Russian Federation, which coordinates and controls the activities of the services under its jurisdiction, including the Federal Tax Service.

Secondly, the assessment of the effectiveness of the activities of the tax authority should be carried out by the number of disputes referred for subsequent consideration to the judicial authorities, as well as by the number of decisions made by the said body overturned by the court.

The criteria by which the effectiveness of the activities of any body performing government functions is assessed are an important element influencing the activities of this body. Since the effectiveness of the tax authority’s activities depends on the amounts of taxes and penalties collected, all the activities of the tax authority are aimed precisely at additional assessment of the corresponding amounts, often violating the law.

If the activities of the new body are assessed according to the proposed criteria, this will create a situation that encourages the adoption of the maximum possible legal and informed decisions.

The proposed directions for improving tax legislation in terms of pre-trial settlement of tax disputes are not exhaustive. The formation of a truly effective pre-trial procedure for resolving tax disputes requires a complete and comprehensive study, on the basis of which other proposals can be formulated to improve out-of-court procedures for resolving tax disputes.

Proposals for improving the mechanism for pre-trial settlement of tax disputes.

Consideration of cases of tax offenses involves two review procedures:

1. in the manner prescribed by Article 101 of the Tax Code of the Russian Federation, cases of tax offenses identified during a desk or field tax audit are considered;

2. in the manner prescribed by Article 101.4 of the Tax Code of the Russian Federation, cases of tax offenses identified during other tax control activities are considered.

These procedures have a number of differences. Thus, in the case of consideration of audit materials in accordance with Article 101.4 of the Tax Code of the Russian Federation, the possibility of extending the period for considering the act and other materials of tax control measures and making a decision on them Art. 101.4 of the Tax Code of the Russian Federation is not provided for; It also does not indicate the possibility of the head (deputy head) of the tax authority recognizing the mandatory participation of the person held liable for taxation to consider the materials and postponing the consideration of the materials on this basis. Unlike paragraph 8 of Art. 101.1 of the Tax Code of the Russian Federation, Article 101.4 of the Tax Code of the Russian Federation does not indicate the possibility of making a decision based on the results of consideration of materials on carrying out additional tax control measures and does not contain the possibility of making such a decision as an interim one.

However, the inability to postpone the consideration of the audit materials due to the absence of the person held liable for taxation (i.e., recognition by the head (deputy head) of the tax authority of the mandatory participation of the person held liable for taxation when considering the audit materials), as well as the implementation of additional tax control measures, deprives the tax authority, in the event of a taxpayer’s objection to the act and additional documents, of the opportunity to comprehensively and more fully evaluate the audit materials, which may affect the validity of the decision made based on the results of their consideration.

Offer:

Make changes to the procedure for considering audit materials in accordance with Article 101.4 of the Tax Code of the Russian Federation, providing for the possibility of postponing the consideration of audit materials due to the absence of a person brought to tax liability, as well as carrying out additional tax control measures.

Page 1

Introduction.

Throughout its development, human civilization, at least in the material sphere, constantly uses chemical, biological and physical laws operating on our planet to satisfy one or another of its needs. http://voronezh.pinskdrev.ru/ dining tables in Voronezh.

In ancient times, this happened in two ways: consciously or spontaneously. Naturally, we are interested in the first way. An example of the conscious use of chemical phenomena can be:

Souring of milk, used to produce cheese, sour cream and other dairy products;

The fermentation of certain seeds, such as hops, in the presence of yeast to produce beer;

Sublimation of pollen of some flowers (poppy, hemp) and obtaining drugs;

Fermentation of the juice of certain fruits (primarily grapes), containing a lot of sugar, resulting in wine and vinegar.

Fire brought revolutionary changes in human life. Man began to use fire for cooking, in pottery production, for processing and smelting metals, processing wood into coal, evaporating and drying food for the winter.

Over time, people began to need more and more new materials. Chemistry provided invaluable assistance in their creation. The role of chemistry is especially great in the creation of pure and ultrapure materials (hereinafter abbreviated as SHM). If, in my opinion, the leading position in the creation of new materials is still occupied by physical processes and technologies, then the production of synthetic materials is often more efficient and productive with the help of chemical reactions. And also there was a need to protect materials from corrosion; this, in fact, is the main role of physical and chemical methods in building materials. Using physicochemical methods they study physical phenomena that occur during chemical reactions. For example, in the colorimetric method, the color intensity is measured depending on the concentration of the substance; in the conductometric analysis, the change in the electrical conductivity of solutions is measured, etc.

This abstract outlines some types of corrosion processes, as well as ways to combat them, which is the main practical task of physical and chemical methods in building materials.

Physico-chemical methods analysis and their classification.

Physicochemical methods of analysis (PCMA) are based on the use of the dependence of the physical properties of substances (for example, light absorption, electrical conductivity, etc.) on their chemical composition. Sometimes in the literature physical methods of analysis are separated from FCMA, thereby emphasizing that FCMA uses chemical reaction, but in physical ones - no. Physical methods of analysis and PCMA, mainly in Western literature, are called instrumental, since they usually require the use of instruments and measuring instruments. Instrumental methods of analysis generally have their own theory, different from the theory of methods of chemical (classical) analysis (titrimetry and gravimetry). The basis of this theory is the interaction of matter with the flow of energy.

When using PCMA to obtain information about the chemical composition of a substance, the sample under study is exposed to some type of energy. Depending on the type of energy in a substance, a change occurs in the energy state of its constituent particles (molecules, ions, atoms), which is expressed in a change in one or another property (for example, color, magnetic properties and so on.). By registering a change in this property as an analytical signal, information is obtained about the qualitative and quantitative composition of the object under study or about its structure.

According to the type of disturbance energy and the measured property (analytical signal), FCMA can be classified as follows (Table 2.1.1).

In addition to those listed in the table, there are many other private FHMAs that do not fall under this classification.

Optical, chromatographic and potentiometric methods of analysis have the greatest practical application.

Table 2.1.1.

Type of disturbance energy	Property being measured	Method name	Method group name
Electron flow (electrochemical reactions in solutions and on electrodes)	Voltage, potential	Potentiometry	Electrochemical
	Electrode polarization current	Voltamperometry, polarography
	Current strength	Amperometry
	Resistance, conductivity	Conductometry
	Impedance (AC resistance, capacitance)	Oscillometry, high-frequency conductometry
	Amount of electricity	Coulometry
	Mass of electrochemical reaction product	Electrogravimetry
	The dielectric constant	Dielcometry
Electromagnetic radiation	Wavelength and intensity of the spectral line in the infrared, visible and ultraviolet parts of the spectrum =10-3 .10-8 m	Optical methods (IR spectroscopy, atomic emission analysis, atomic absorption analysis, photometry, luminescent analysis, turbidimetry, nephelometry)	Spectral
	The same, in the X-ray region of the spectrum =10-8 .10-11 m	X-ray photoelectron, Auger spectroscopy

Photocolorimetry

Quantitative determination of the concentration of a substance by light absorption in the visible and near ultraviolet region of the spectrum. Light absorption is measured using photoelectric colorimeters.

Spectrophotometry (absorption). A physicochemical method for studying solutions and solids, based on the study of absorption spectra in the ultraviolet (200–400 nm), visible (400–760 nm) and infrared (>760 nm) regions of the spectrum. The main dependence studied in spectrophotometry is the dependence of the absorption intensity of incident light on the wavelength. Spectrophotometry is widely used in studying the structure and composition of various compounds (complexes, dyes, analytical reagents, etc.), for the qualitative and quantitative determination of substances (determination of trace elements in metals, alloys, technical objects). Spectrophotometric instruments – spectrophotometers.

Absorption spectroscopy, studies the absorption spectra of electromagnetic radiation by atoms and molecules of matter in various states of aggregation. The intensity of the light flux as it passes through the medium under study decreases due to the conversion of radiation energy into various forms of internal energy of the substance and (or) into the energy of secondary radiation. The absorption capacity of a substance depends on the electronic structure of atoms and molecules, as well as on the wavelength and polarization of the incident light, layer thickness, concentration of the substance, temperature, and the presence of electric and magnetic fields. To measure absorbance, spectrophotometers are used - optical instruments consisting of a light source, a sample chamber, a monochromator (prism or diffraction grating) and a detector. The signal from the detector is recorded in the form of a continuous curve (absorption spectrum) or in the form of tables if the spectrophotometer has a built-in computer.

1. Bouguer-Lambert law: if the medium is homogeneous and the layer of matter is perpendicular to the incident parallel light flux, then

I = I 0 exp (- kd),

where I 0 and I-intensities, respectively. incident and passed through the light, d-layer thickness, k-coefficient. absorption, which does not depend on the thickness of the absorbing layer and the intensity of the incident radiation. To characterize the absorb. abilities widely use coefficients. extinction, or light absorption; k" = k/2.303 (in cm -1) and optical density A = log I 0 /I, as well as the transmittance value T = I/I 0. Deviations from the law are known only for light fluxes of extremely high intensity (for laser radiation Coefficient k depends on the wavelength of the incident light, since its value is determined by the electronic configuration of molecules and atoms and the probabilities of transitions between their electronic levels.The combination of transitions creates an absorption spectrum characteristic of a given substance.

2. Beer's law: each molecule or atom, regardless of the relative location of other molecules or atoms, absorbs the same fraction of radiation energy. Deviations from this law indicate the formation of dimers, polymers, associates, and chemical reactions. interaction of absorbing particles.

3. Combined Bouguer-Lambert-Beer law:

A = log(I 0 /I)=КLC

L – thickness of the absorbing layer of atomic vapor

Absorption spectroscopy is based on the use the ability of a substance to selectively absorb light energy.

Absorption spectroscopy studies the absorption capacity of substances. The absorption spectrum (absorption spectrum) is obtained as follows: a substance (sample) is placed between a spectrometer and a source of electromagnetic radiation with a certain frequency range. A spectrometer measures the intensity of light passed through a sample compared to the intensity of the original radiation at a given wavelength. In this case, the high energy state also has a short lifespan. In the ultraviolet region, the absorbed energy usually turns back into light; in some cases it can induce photochemical reactions. A typical water transmission spectrum taken in an AgBr cuvette about 12 µm thick.

Absorption spectroscopy, which includes methods of infrared, ultraviolet and NMR spectroscopy, provides information about the nature average molecule, but, in contrast to mass spectrometry, does not allow recognition different kinds molecules that may be present in the sample being analyzed.

Paramagnetic resonance absorption spectroscopy is a technique that can be applied to molecules containing atoms or ions with unpaired electrons. Absorption leads to a change in orientation magnetic moment when moving from one permitted position to another. The true absorbed frequency depends on the magnetic field, and therefore, by varying the field, the absorption can be determined from some microwave frequency.

Paramagnetic resonance absorption spectroscopy is a technique that can be applied to molecules containing atoms or ions with unpaired electrons. This leads to a change in the orientation of the magnetic moment when moving from one allowed position to another. The true absorbed frequency depends on the magnetic field, and therefore, by varying the field, the absorption can be determined from some microwave frequency.

In absorption spectroscopy, a molecule in a lower energy level absorbs a photon with frequency v, calculated by the equation, moving to a higher one energy level. In a conventional spectrometer, radiation containing all frequencies in infrared region. The spectrometer records the amount of energy passed through the sample as a function of the frequency of the radiation. Since the sample absorbs only radiation with a frequency determined by the equation, the spectrometer recorder shows uniform high transmittance, except in the region of those frequencies determined from the equation where absorption bands are observed.

Absorption spectroscopy determines the change in the intensity of electromagnetic radiation created by some source, a change that is observed when the radiation passes through a substance that absorbs it. In this case, the molecules of the substance interact with electromagnetic radiation and absorb energy.

The absorption spectroscopy method is used to determine the amount of a gas impurity from the measured area of ​​an individual absorption line, a group of lines, or an entire absorption band in the spectrum of radiation that has passed a certain path in the medium. The measured areas are compared with similar values ​​calculated on the basis of data on absorption spectra obtained in laboratory conditions with dosed quantities of measured gas.

In absorption spectroscopy, the minimum lifetime required before discernible spectra can be observed increases as the transition energy decreases.

For absorption spectroscopy, a white light source can be used in combination with a spectrograph to obtain a photographically recorded survey spectrum of absorbing compounds in reaction system. In other cases, a monochromator with a photoelectric detector can be used to scan the spectral range. Many short-lived intermediates under study have quite high optical absorption due to the presence of an allowed electronic dipole transition to a higher high level energy. In this case, for example, triplet excited states can be observed by their triplet-triplet absorption. In general, individual absorption bands have a greater amplitude the narrower they are. As a result of this effect, atoms have allowed absorption lines with particularly large amplitudes. In quantitative absorption measurements, a wavelength is usually selected at which a strong absorption band is observed and is not superimposed by the absorption bands of other compounds.

In absorption spectroscopy, we are limited not so much by the optical properties of the gas under study, heated by a shock wave, as by the properties of the radiation source.

The use of absorption spectroscopy involves the consumption of small quantities of the substance under study.

Kinetic absorption spectroscopy, covering the electronic region of the spectrum, is well known as the main method for monitoring the concentrations of radicals, reactants and end products formed as a result of pulsed photolysis. However, this method has only recently become widely used in many jet discharge installations. Due to low optical densities, scanning the striped spectra of unknowns chemical systems difficult. This method is most suitable for studying radicals whose electronic absorption spectra have been determined quite accurately.

In absorption spectroscopy devices, light from an illumination source passes through a monochromatizer and falls on a cuvette with the substance being studied. In practice, the ratio of the intensities of monochromatic light passing through the test solution and through the solvent or a specially selected reference solution is usually determined.

In the absorption spectroscopy method, a beam of monochromatic light with wavelength A and frequency v passes through a cuvette of length l (in cm) containing a solution of an absorbing compound of concentration c (mol/l) in a suitable solvent.

However, in atomic absorption spectroscopy this light source is still undeservedly little used. The advantage of high-frequency lamps is their ease of manufacture, since the lamp is usually a glass or quartz vessel in which there is no a large number of metal

Flame in atomic absorption spectroscopy is the most common method of atomizing a substance. In atomic absorption spectroscopy, the flame plays the same role as in flame emission spectroscopy, with the only difference being that in the latter case the flame is also a means of exciting atoms. Therefore, it is natural that the technique of flame atomization of samples in atomic absorption spectral analysis largely copies the technique of flame emission photometry.

Atomic absorption spectrometry (AAS) method, atomic absorption analysis (AAA) is a method of quantitative elemental analysis based on atomic absorption (absorption) spectra. Widely used in mineral analysis to determine various elements.

The principle of operation of the method based on the fact that the atoms of each chemical element have strictly defined resonant frequencies, as a result of which it is at these frequencies that they emit or absorb light. This leads to the fact that in a spectroscope, lines (dark or light) are visible on the spectra in certain places characteristic of each substance. The intensity of the lines depends on the amount of substance and its state. In quantitative spectral analysis, the content of the substance under study is determined by the relative or absolute intensities of lines or bands in the spectra.

Atomic spectra (absorption or emission) are obtained by transferring the substance to the vapor state by heating the sample to 1000–10000 °C. As sources of excitation of atoms at emission analysis conductive materials use a spark, an alternating current arc; in this case, the sample is placed in the crater of one of the carbon electrodes. Flames or plasmas of various gases are widely used to analyze solutions.

Advantages of the method:

· simplicity,

· high selectivity,

· little influence of the sample composition on the analysis results.

· Economical;

· Simplicity and accessibility of equipment;

· High performance analysis;

· Availability of a large number of certified analytical methods.

· Literature for familiarization with the AAS method

Limitations of the method– the impossibility of simultaneous determination of several elements when using linear radiation sources and, as a rule, the need to transfer samples into solution.

In the laboratory The HSMA AAS method has been used for more than 30 years. With his help are determined CaO, MgO, MnO, Fe 2 O 3, Ag, trace impurities; flame photometric method - Na 2 O, K 2 O.

Atomic absorption analysis(atomic absorption spectrometry), quantitative method. elemental analysis based on atomic absorption (absorption) spectra.

Principle of the method: Radiation in the range of 190-850 nm is passed through a layer of atomic vapors of samples obtained using an atomizer (see below). As a result of the absorption of light quanta (photon absorption), atoms pass into excited energy states. These transitions in atomic spectra correspond to the so-called. resonant lines characteristic of a given element. A measure of the concentration of an element - optical density or atomic absorption:

A = log(I 0 /I) = KLC (according to the Bouguer-Lambert-Beer law),

where I 0 and I are the intensities of radiation from the source, respectively, before and after passing through the absorbing layer of atomic vapor.

K-proportionality coefficient (electronic transition probability coefficient)

L - thickness of the absorbing layer of atomic vapor

C – concentration of the element being determined

Schematic diagram flame atomic absorption spectrometer: 1-radiation source; 2-flame; 3-monochrome of mountains; 4-photomultiplier; 5-recording or indicating device.

Instruments for atomic absorption analysis- atomic absorption spectrometers – precision, highly automated devices that ensure reproducibility of measurement conditions, automatic introduction of samples and recording of measurement results. Some models have built-in microcomputers. As an example, the figure shows a diagram of one of the spectrometers. The source of line radiation in spectrometers is most often single-element lamps with a hollow cathode filled with neon. To determine some highly volatile elements (Cd, Zn, Se, Te, etc.), it is more convenient to use high-frequency electrodeless lamps.

The transfer of the analyzed object into an atomized state and the formation of an absorbing layer of vapor of a certain and reproducible shape is carried out in an atomizer - usually in a flame or a tubular furnace. Naib. flames of mixtures of acetylene with air (max. temperature 2000°C) and acetylene with N2O (2700°C) are often used. A burner with a slot-like nozzle 50-100 mm long and 0.5-0.8 mm wide is installed along the optical axis of the device to increase the length of the absorbing layer.

Tubular resistance furnaces are most often made from dense grades of graphite. To eliminate vapor diffusion through the walls and increase durability, graphite tubes are coated with a layer of gas-tight pyrolytic carbon. Max. The heating temperature reaches 3000 °C. Less common are thin-walled tubular furnaces made of refractory metals (W, Ta, Mo), quartz with a nichrome heater. To protect graphite and metal furnaces from burning in air, they are placed in semi-hermetic or sealed chambers through which inert gas (Ar, N2) is blown.

The introduction of samples into the absorption zone of a flame or furnace is carried out using different techniques. Solutions are sprayed (usually into a flame) using pneumatic sprayers, less often ultrasonic sprayers. The former are simpler and more stable in operation, although they are inferior to the latter in the degree of dispersion of the resulting aerosol. Only 5-15% of the smallest aerosol droplets enter the flame, and the rest is screened out in the mixing chamber and discharged into the drain. Max. the concentration of solid matter in solution usually does not exceed 1%. Otherwise, intense deposition of salts occurs in the burner nozzle.

Thermal evaporation of dry solution residues is the main method of introducing samples into tube furnaces. In this case, samples are most often evaporated from the inner surface of the furnace; the sample solution (volume 5-50 μl) is injected using a micropipette through the dosing hole in the tube wall and dried at 100°C. However, samples evaporate from the walls with a continuous increase in the temperature of the absorbing layer, which causes instability of the results. To ensure a constant oven temperature at the time of evaporation, the sample is introduced into a preheated oven using a carbon electrode (graphite cell), graphite crucible (Woodriff oven), metal or graphite probe. The sample can be evaporated from a platform (graphite trough), which is installed in the center of the furnace under the dosing hole. As a result it means. If the temperature of the platform lags behind the temperature of the furnace, which is heated at a rate of about 2000 K/s, evaporation occurs when the furnace reaches an almost constant temperature.

To be introduced into the flame solids or dry residues of solutions, rods, threads, boats, crucibles made of graphite or refractory metals are used, placed below the optical axis of the device, so that the sample vapors enter the absorption zone with the flow of flame gases. In some cases, graphite evaporators are additionally heated by electric current. To exclude fur. To prevent loss of powdered samples during the heating process, cylindrical capsule-type evaporators made of porous graphite are used.

Sometimes sample solutions are treated in a reaction vessel with reducing agents present, most often NaBH 4 . In this case, Hg, for example, is distilled off in elemental form, As, Sb, Bi, etc. - in the form of hydrides, which are introduced into the atomizer with a flow of inert gas. To monochromatize the radiation, prisms or diffraction gratings; in this case, a resolution of 0.04 to 0.4 nm is achieved.

In atomic absorption analysis, it is necessary to exclude the overlap of the radiation of the atomizer with the radiation of the light source, to take into account a possible change in the brightness of the latter, spectral interference in the atomizer caused by partial scattering and absorption of light by solid particles and molecules of foreign components of the sample. To do this, use various techniques, for example. the source radiation is modulated with a frequency to which the recording device is tuned approximately; a two-beam scheme or an optical scheme with two light sources (with discrete and continuous spectra) is used. max. An effective scheme is based on Zeeman splitting and polarization of spectral lines in an atomizer. In this case, light polarized perpendicular to the magnetic field is passed through the absorbing layer, which makes it possible to take into account non-selective spectral interference reaching values ​​of A = 2 when measuring signals that are hundreds of times weaker.

The advantages of atomic absorption analysis are simplicity, high selectivity and little influence of the sample composition on the analysis results. The limitations of the method are the impossibility of simultaneous determination of several elements when using linear radiation sources and, as a rule, the need to transfer samples into solution.

Atomic absorption analysis is used to determine about 70 elements (mainly sample metals). Gases and some other nonmetals whose resonance lines lie in the vacuum region of the spectrum (wavelength less than 190 nm) are also not detected. Using a graphite furnace, it is impossible to determine Hf, Nb, Ta, W and Zr, which form low-volatile carbides with carbon. The detection limits of most elements in solutions during atomization in a flame or in a graphite furnace are 100-1000 times lower. The absolute detection limits in the latter case are 0.1-100 pg.

Relative standard deviation under optimal measurement conditions it reaches 0.2-0.5% for a flame and 0.5-1.0% for a furnace. In automatic operating mode, the flame spectrometer allows analyzing up to 500 samples per hour, and the spectrometer with a graphite furnace allows up to 30 samples. Both options are often used in combination with pre-treatment. separation and concentration by extraction, distillation, ion exchange, chromatography, which in some cases makes it possible to indirectly determine some non-metals and organic compounds.

Atomic absorption analysis methods are also used to measure some physical properties. and physical-chemical quantities - the coefficient of diffusion of atoms in gases, temperatures of the gaseous medium, heats of evaporation of elements, etc.; to study the spectra of molecules, study processes associated with the evaporation and dissociation of compounds.

Introduction

Throughout its development, humanity uses the laws of chemistry and physics in its activities to solve various problems and satisfy many needs.

In ancient times, this process took place in two different ways: consciously, based on accumulated experience, or by chance. Vivid examples of the conscious application of the laws of chemistry include: souring milk, and its subsequent use for the preparation of cheese products, sour cream and other things; fermentation of certain seeds, for example, hops, and subsequent production of brewing products; fermentation of the juices of various fruits (mainly grapes, which contain a large amount of sugar), ultimately produced wine products and vinegar.

The discovery of fire was a revolution in the life of mankind. People began to use fire for cooking food, for heat treatment of clay products, for working with various metals, for producing charcoal and much more.

Over time, people have developed a need for more functional materials and products based on them. Their knowledge in the field of chemistry had a huge impact on solving this problem. Chemistry played a particularly important role in the production of pure and ultrapure substances. If in the manufacture of new materials, the first place belongs to physical processes and technologies based on them, then the synthesis of ultrapure substances, as a rule, is more easily accomplished using chemical reactions [

Using physicochemical methods, they study the physical phenomena that arise during chemical reactions. For example, in the colorimetric method, the color intensity is measured depending on the concentration of the substance; in the conductometric method, the change in electrical conductivity of solutions is measured, optical methods use the relationship between the optical properties of the system and its composition.

Physico-chemical research methods are also used for complex studies building materials. The use of such methods allows for an in-depth study of the composition, structure and properties of building materials and products. Diagnostics of the composition, structure and properties of a material at different stages of its manufacture and operation makes it possible to develop progressive resource-saving and energy-saving technologies [

The above work shows the general classification of physicochemical methods for studying building materials (thermography, radiography, optical microscopy, electron microscopy, atomic emission spectroscopy, molecular absorption spectroscopy, colorimetry, potentiometry) and methods such as thermal and x-ray phase analysis, as well as methods for studying the porous structure [ Builder's Handbook [ Electronic resource] // Ministry of Urban and Rural Construction of the Belarusian SSR. URL: www.bibliotekar.ru/spravochnick-104-stroymaterialy.html].

1. Classification of physical and chemical research methods

Physico-chemical research methods are based on close connection physical characteristics of the material (for example, ability to absorb light, electrical conductivity, etc.) and structural organization material from a chemical point of view. It happens that from physico-chemical methods, purely physical research methods are distinguished as a separate group, thus showing that physico-chemical methods consider a certain chemical reaction, in contrast to purely physical ones. These research methods are often called instrumental because they involve the use of various measuring devices. Instrumental research methods, as a rule, have their own theoretical base, this base is at odds with the theoretical base chemical research(titrimetric and gravimetric). It was based on the interaction of matter with various energies.

During physical and chemical research In order to obtain the necessary data on the composition and structural organization of a substance, an experimental sample is exposed to the influence of some kind of energy. Depending on the type of energy in a substance, the energy states of its constituent particles (molecules, ions, atoms) change. This is expressed in a change in a certain set of characteristics (for example, color, magnetic properties and others). As a result of recording changes in the characteristics of a substance, data is obtained on the qualitative and quantitative composition of the test sample, or data on its structure.

According to the type of influencing energies and the characteristics being studied, physico-chemical research methods are divided in the following way.

Table 1. Classification of physicochemical methods

In addition to those given in this table, there are quite a lot of private physicochemical methods that do not fit this classification. In fact, the most actively used are optical, chromatographic and potentiometric methods for studying the characteristics, composition and structure of a sample [ Galuso, G.S. Methods for studying building materials: educational manual / G.S. Galuzo, V.A. Bogdan, O.G. Galuzo, V.I. Kovazhnkova. – Minsk: BNTU, 2008. – 227 p.].

2. Thermal analysis methods

Thermal analysis is actively used to study various building materials - mineral and organic, natural and synthetic. Its use helps to identify the presence of a particular phase in a material, determine interaction reactions, decomposition and, in exceptional cases, obtain information about the quantitative composition of the crystalline phase. The ability to obtain information on the phase composition of highly dispersed and cryptocrystalline polymineral mixtures without dividing into polymineral fractions is one of the main advantages of the technique. Thermal research methods are based on the rules of constant chemical composition and physical characteristics substances, in specific conditions, and, among other things, on the laws of correspondence and characteristicality.

The correspondence law says that a specific thermal effect can be correlated with any phase change in a sample.

And the law of characteristicality states that thermal effects are individual for each chemical substance.

The main idea of ​​thermal analysis is to study the transformations that occur under conditions of increasing temperature in systems of substances or specific compounds during various physical and chemical processes, according to the thermal effects accompanying them.

Physical processes, as a rule, are based on the transformation of the structural structure, or state of aggregation system with its constant chemical composition.

Chemical processes lead to a transformation of the chemical composition of the system. These include directly dehydration, dissociation, oxidation, exchange reactions and others.

Initially, thermal curves for limestone and clayey rocks were obtained by the French scientist chemist Henri Louis Le Chatelier in 1886 - 1887. In Russia, academician N.S. was one of the first to study thermal research methods. Kurnakov (in 1904). Updated modifications of the Kurnakov pyrometer (an apparatus for automatically recording heating and cooling curves) are still used to this day in most research laboratories. Regarding the characteristics under study as a result of heating or cooling, the following methods of thermal analysis are distinguished: differential thermal analysis (DTA) - the change in energy of the sample under study is determined; thermogravimetry – mass changes; dilatometry – volumes change; gas volumetry – the composition of the gas phase changes; electrical conductivity – electrical resistance changes.

During thermal research, several study methods can be used in parallel, each of which records changes in energy, mass, volume and other characteristics. A comprehensive study of the characteristics of the system during the heating process helps to study in more detail and more thoroughly the basics of the processes occurring in it.

One of the most important and widely used methods is differential thermal analysis.

Fluctuations in the temperature characteristics of a substance can be detected by sequentially heating it. So, the crucible is filled with experimental material (sample), placed in an electric furnace, which heats up, and the temperature readings of the system under study begin to be taken using a simple thermocouple connected to a galvanometer.

Registration of changes in the enthalpy of a substance occurs using an ordinary thermocouple. But due to the fact that the deviations that can be seen on the temperature curve are not very large, it is better to use a differential thermocouple. Initially, the use of this thermocouple was proposed by N.S. Kurnakov. A schematic representation of a self-registering pyrometer is presented in Figure 1.

This schematic image shows a pair of ordinary thermocouples, which are connected to each other by the same ends, forming the so-called cold junction. The remaining two ends are connected to the apparatus, which makes it possible to record transformations in the electromotive force (EMF) circuit that appear as a result of an increase in the temperature of the hot junctions of the thermocouple. One hot junction is located in the sample being studied, and the second is located in the reference substance.

Figure 1. Schematic representation of a differential and simple thermocouple: 1 – electric furnace; 2 – block; 3 – experimental sample under study; 4 – reference substance (standard); 5 – thermocouple hot junction; 6 – cold junction of thermocouple; 7 – galvanometer for fixing the DTA curve; 8 – galvanometer for recording the temperature curve.

If, for the system under study, any transformations that are associated with the absorption or release of thermal energy are frequent, then its temperature indicator in this moment may be much greater or less than the reference reference substance. This temperature difference leads to a difference in the EMF value and, as a consequence, to a deviation of the DTA curve up or down from zero or the base line. The zero line is the line parallel to the x-axis and drawn through the beginning of the DTA curve; this can be seen in Figure 2.

Figure 2. Schematic of simple and differential (DTA) temperature curves.

In fact, often after the completion of some thermal transformation, the DTA curve does not return to the zero line, but continues to run parallel to it or at a certain angle. This line is called the baseline. This discrepancy between the base and zero lines is explained by different thermophysical characteristics of the studied system of substances and the reference substance of comparison [].

3. X-ray phase analysis methods

X-ray methods for studying building materials are based on experiments in which X-rays are used. This class of research is actively used to study the mineralogical composition of raw materials and final products, phase transformations in the substance at various stages of their processing into ready-to-use products and during operation, and, among other things, to identify the nature of the structural structure of the crystal lattice.

The X-ray diffraction technique used to determine the parameters of the unit cell of a substance is called the X-ray diffraction technique. The technique that is followed in the study of phase transformations and the mineralogical composition of substances is called X-ray phase analysis. X-ray phase analysis (XRF) methods are of great importance in the study of mineral building materials. Based on the results of X-ray phase studies, information is obtained about the presence of crystalline phases and their quantities in the sample. It follows from this that there is a quantitative and qualitative methods analysis.

The purpose of qualitative X-ray phase analysis is to obtain information about the nature of the crystalline phase of the substance being studied. The methods are based on the fact that each specific crystalline material has a specific x-ray pattern with its own set diffraction maxima. Nowadays, there is reliable radiographic data on most known to man crystalline substances.

The task of quantitative composition is to obtain information about the amount of specific phases in polyphase polycrystalline substances; it is based on the dependence of the intensity of diffraction maxima on the percentage of the phase under study. As the amount of any phase increases, its reflection intensity becomes greater. But for polyphase substances, the relationship between the intensity and amount of this phase is ambiguous, since the magnitude of the reflection intensity of a given phase depends not only on its percentage content, but also on the value of μ, which characterizes how much the x-ray beam is attenuated as a result of passing through the material under study . This attenuation value of the material being studied depends on the attenuation values ​​and the number of other phases that are also included in its composition. It follows from this that each technique quantitative analysis must somehow take into account the effect of the attenuation index, as a result of changes in the composition of the samples, which violates the direct proportionality between the amount of this phase and the degree of intensity of its diffraction reflection [ Makarova, I.A. Physico-chemical methods for studying building materials: textbook / I.A. Makarova, N.A. Lokhova. – Bratsk: Iz-vo BrGU, 2011. – 139 p. ].

Options for obtaining X-ray images are divided, based on the method of recording radiation, into photographic and diffractometric. The use of methods of the first type involves photo registration x-ray radiation, under the influence of which darkening of the photographic emulsion is observed. Diffractometric methods for obtaining X-ray patterns, which are implemented in diffractometers, differ from photographic methods in that the diffraction pattern is obtained sequentially over time [ Pindyuk, T.F. Methods for studying building materials: guidelines for laboratory work / T.F. Pindyuk, I.L. Chulkova. – Omsk: SibADI, 2011. – 60 p. ].

4. Methods for studying porous structure

Building materials have heterogeneous and quite complex structure. Despite the variety and origin of materials (concrete, silicate materials, ceramics), their structure always contains various pores.

The term “porosity” connects the two most important properties of a material – geometry and structure. The geometric characteristic is the total volume of pores, the size of the pores and their total specific surface area, which determine the porosity of the structure (large-porous material or fine-porous one). Structural characteristics– this is the type of pores and their distribution by size. These properties vary depending on the structure of the solid phase (granular, cellular, fibrous, etc.) and the structure of the pores themselves (open, closed, communicating).

The main influence on the size and structure of porous formations is exerted by the properties of the feedstock, the composition of the mixture, and the production process. The most important characteristics are the particle size distribution, volume of the binder, percentage of moisture in the feedstock, methods of molding the final product, conditions of formation final structure(sintering, fusion, hydration and others). Strong influence The structure of porous formations is affected by specialized additives, so-called modifiers. These include, for example, fuel and burn-out additives, which are added to the mixture during the production of ceramic products, and in addition to surfactants, they are used both in ceramics and in cement-based materials. The pores differ not only in size, but also in shape, and the capillary channels they create have a variable cross-section along their entire length. All pore formations are classified into closed and open, as well as channel-forming and dead-end.

The structure of porous building materials is characterized by the combination of all types of pores. Porous formations can be randomly located inside a substance, or they can have some order.

Pore ​​channels have a very complex structure. Closed pores are cut off from open pores and are in no way connected with each other or with the external environment. This class of pores is impermeable to gaseous substances and liquids and, as a result, is not considered hazardous. Open channel-forming and dead-end porous formations water environment can be filled in without difficulty. Their filling proceeds according to various patterns and depends mainly on the area cross section and the length of the pore channels. As a result of ordinary saturation, not all porous channels can be filled with water; for example, the smallest pores less than 0.12 microns in size are not filled due to the presence of air in them. Large porous formations fill very quickly, but in an air environment, as a result of the low value capillary forces, water is poorly retained in them.

The volume of water absorbed by a substance depends on the size of the porous formations and on the adsorption characteristics of the material itself.

To determine the relationship between the porous structure and physical and chemical characteristics It is not enough for the material to know only the general value of the volume of porous formations. General porosity does not determine the structure of the substance; here important role plays the principle of pore size distribution and the presence of porous formations of a specific size.

Geometric and structural indicators of porosity of building materials differ both at the micro and macro levels. G.I. Gorchakov and E.G. Muradov developed an experimental and computational methodology for identifying the general and group porosity of concrete materials. The basis of the methodology is that during the experiment the level of hydration of cement in concrete is determined using quantitative X-ray examination or approximately by the volume of water ω bound in the cement binder that did not evaporate during drying at a temperature of 150 ºC: α = ω/ ω max .

The volume of bound water with complete hydration of cement is in the range of 0.25 – 0.30 (to the mass of uncalcined cement).

Then, using the formulas from Table 1, the porosity of concrete is calculated depending on the level of cement hydration, its consumption in concrete and the amount of water [ Makarova, I.A. Physico-chemical methods for studying building materials: textbook / I.A. Makarova, N.A. Lokhova. – Bratsk: Iz-vo BrGU, 2011. – 139 p. ].

Goal of the work: 1. Familiarize yourself with the basic methods for studying the properties of building materials.

2. Analyze the basic properties of building materials.

1. Determination of the true (absolute) density of the material

(pycnometric method) (GOST 8269)

To determine the true density, crushed building materials are taken: brick, crushed limestone, expanded clay gravel, crushed, passed through a sieve with a mesh of less than 0.1 mm, and a sample weighing 10 g each (m) is taken.

Each sample is poured into a clean, dried pycnometer (Fig. 1) and distilled water is poured into it in such an amount that the pycnometer is filled to no more than half its volume, then the pycnometer is shaken, wetting all the powder, placed in a sand bath and the contents are heated. until boiling in an inclined position for 15-20 minutes to remove air bubbles.

Rice. 1 – Pycnometer for determining the true density of the material

Then the pycnometer is wiped, cooled to room temperature, distilled water is added to the mark and weighed (m 1), after which the pycnometer is emptied of its contents, washed, filled to the mark with distilled water at room temperature and weighed again (m 2). A table is drawn in the notebook in which the masses of each material and subsequent calculations are entered.

The true density of the material is determined by the formula:

where is the mass of the powder sample, g;

Weight of pycnometer with sample and water after boiling, g;

Weight of pycnometer with water, g;

The density of water is 1 g/cm3.

2. Determination of the average density of a sample of the correct geometric shape (GOST 6427)

It is better to determine the average density for the same materials - brick, a piece of limestone and expanded clay gravel. The volume of samples of regular geometric shape (brick) is determined by geometric dimensions in accordance with the drawing, measured with an error of no more than 0.1 mm. Each linear dimension is calculated as the arithmetic mean of three measurements. Samples must be dry.

Sample volume irregular shape determined by the displaced water by dropping a piece of limestone or gravel into a measuring cylinder filled with water, which sinks, with a mark on the volume of the displaced fluid. 1ml=1cm 3.

Rice. 1 – Measurement of linear dimensions and volume of a sample

prisms cylinder

Average density determined by the formula:

where is the mass of the dry sample, g;

Sample volume, cm3.

No.	Material								P, %
	brick
	limestone
	expanded clay
	sq. sand

3. Determination of material porosity (GOST 12730.4)

Knowing the true density and average density brick, limestone, expanded clay gravel, determine the porosity of the material P,%, according to the formula:

where is the average density of the material, g/cm 3 or kg/m 3 ;

True density of the material, g/cm3 or kg/m3.

Comparative Density different materials is given in Appendix A. The results are entered into the table.

4. Determination of bulk density (GOST 8269)

Bulk material (sand, expanded clay gravel, crushed stone) in a volume sufficient to carry out the test is dried until constant mass. The material is poured into a pre-weighed measuring cylinder (m) from a height of 10 cm until a cone is formed, which is removed with a steel ruler flush with the edges (without compaction) moving towards you, after which the cylinder with the sample is weighed (m 1).

Rice. 3. Funnel for determining the bulk density of sand

1 – funnel; 2 – supports; 3 – damper

Bulk density of material determined by the formula:

where is the mass of the graduated cylinder, g;

Mass of the measuring cylinder with attachment, g;

Volume of graduated cylinder, l.

The results are entered into the table.

5. Determination of voidness (GOST 8269)

Voidness (V empty, %) bulk material determined by knowing the bulk and average density of the bulk material using the formula:

where is the bulk density of the material, kg/m3;

Average density of the material, kg/m3.

The average density of quartz sand is not determined; it is accepted as true - 2.65 g/cm 3 .

6. Determination of material moisture (GOST 8269)

A sample of the material in the amount of 1.5 kg is poured into a vessel and weighed, then dried to a constant weight in a drying oven (this must be done in advance). To determine humidity in a lesson, you can do the opposite: weigh an arbitrary amount of dry sand in a vessel and wet it arbitrarily, weigh it again, getting and.

Humidity W,%, is determined by the formula:

where is the mass of the wet sample, g;

Dry mass of sample, g.

To determine water absorption, three samples of any shape measuring from 40 to 70 mm or a brick are taken and the volume is determined. Clean the samples from dust with a wire brush and dry to a constant weight. Then they are weighed and placed in a vessel with water at room temperature so that the water level in the vessel is at least 20 mm above the top of the samples. The samples are kept in this position for 48 hours. After which they are removed from the water, moisture is removed from the surface with a wrung-out damp soft cloth, and each sample is weighed.

Water absorption by mass Wab,%, is determined by the formula:

Water absorption by volume W o,%, is determined by the formula:

where is the dry mass of the sample, g;

Mass of the sample after saturation with water, g;

Volume of the sample in its natural state, cm3.

Relative density defined as:

The coefficient of saturation of the material with water is determined:

Having calculated all the indicators with the teacher, the student receives an individual assignment based on the variants of test No. 1 problems.

7. Determination of compressive strength (GOST 8462)

Compressive strength is determined on cubes of sizes 7.07 × 7.07 × 7.07 cm, 10 × 10 × 10 cm, 15 × 15 × 15 cm and 20 × 20 × 20 cm. Bricks and beams are first tested for bending strength (8), then the halves are tested in compression.

To determine compressive strength, samples of regular geometric shape (beams, cubes, bricks) are inspected, measured and tested on a hydraulic press. Place the sample in the center of the base plate and press it with the top plate of the press, which should fit tightly along the entire edge of the sample. During testing, the load on the sample must increase continuously and evenly. The highest compressive load corresponds to the maximum pressure gauge reading during the test.

When testing the compressive strength of cubes, top edge The cube should become a side face to eliminate unevenness.

Ultimate compressive strength R compressed, MPa, for concrete cube samples is determined by the formula:

where is the maximum breaking load, kN;

Cross-sectional area of ​​the sample (arithmetic mean of the areas of the upper and lower faces), cm 2.

8. Determination of bending strength. (GOST 8462)

The tensile strength in bending is determined on samples - beams using the MII-100 universal machine, which immediately gives readings of the strength weight in kg/cm 2 or on brick using a hydraulic press using rollers according to the scheme proposed in Figure 5. Tests of the strength of the brick must be shown, then the compressive strength of the halves (9) and the brand of brick must be determined.

Rice. 4 – MII-100 testing machine for determining bending strength

Fig. 5 – Scheme of bending strength test

Ultimate bending strength R bend, MPa, is determined by the following formula:

Distance between support axes, cm;

Sample width, cm;

Sample height, cm.

Material
brick
beam
cube

9. Determination of the coefficient of structural quality (specific strength of the material)

Enter the calculation results into the table.

Control questions

1. What are the main properties of building materials, which ones are important for structural materials?

2. What densities are determined for building materials, and how?

3. What is true density? Why is it defined?

4. What is bulk density? How is it determined and why?

5. To determine the average density, what volume do you need to know? How to determine the volume of a piece of crushed stone?

6. Which density has the greatest numeric expression for the same material, which is the smallest? Why?

7. For what materials is voidness determined, how does it differ from porosity? Compare the true, average, and bulk densities of quartz sand, brick, expanded clay gravel or crushed limestone.

8. What is the relationship between total porosity and density? What is porosity?

9. What porosity can the material have? How can it be determined?

10. Does porosity affect the moisture content of a material? What is humidity?

11. How does humidity differ from water absorption? What properties can be judged by knowing water absorption?

12. How to determine the water saturation coefficient? What does it characterize?

13. How to determine the softening coefficient? What is its significance for air and hydraulic binders?

14. Will water and gas permeability change with a change in density, how? At what type of porosity do these indicators increase?

15. Does the amount of porosity affect the amount of swelling and shrinkage of the material? What is the shrinkage of cellular concrete, what is that of heavy concrete?

16. Is there a connection between the density of a material and thermal conductivity? What materials protect better from the cold? What density material are the walls of residential buildings made of?

17. Does moistening the material affect the thermal conductivity coefficient? Why?

18. What is the coefficient of linear thermal expansion for concrete, steel, granite, wood? When does it matter?

19. Is it possible to use materials with Kn = 1 for the manufacture of road surface slabs? Why?

20. How does porosity differ from voidness, and what formula is used to determine these indicators?

21. Are there materials whose true density is equal to the average?

22. Why do pores form in bricks? Does the method of brick molding affect their number?

23. How do we increase porosity in artificial stone, why?

24. What causes shrinkage, which materials have it more: dense or porous?

25. Does shrinkage depend on the water absorption of the material? What water in the structure of the material does not evaporate?

26. On what samples is the strength of binders, mortars and concrete determined, by what formula is the strength calculated, in what units?

27. On what indicators does strength depend, and in which structures is it maximum?

28. Why do some materials have greater flexural strength, while others have less compressive strength? What are such materials called?

29. What characteristics does frost resistance depend on?

30. What is called specific surface area? Does moisture depend on this characteristic?

Laboratory work №4

Gypsum binders

Goal of the work: 1. Familiarize yourself with the basic properties of building gypsum.

2. Analyze the main properties of building gypsum.