Method of determining frost resistance of stone
SUBSTANCE: stone sample saturated with water is frozen to a specified temperature. The sample is unfrozen and deformation is measured. Before freezing, the threshold load which accounts for long-term compression strength of the sample is measured using a nondestructive method. After several thermal cycles, residual deformation of the unfrozen sample is measured in the direction perpendicular the previous compression. A least residual deformation is achieved through periodical compression of the sample in the current direction from zero to a load which exceeds the threshold by not more than a third. The number of thermal cycles required for reducing long-term strength to the required value is determined by repeating these operations.
EFFECT: reduced labour input and increased efficiency.
The invention relates to methods for evaluation of long-term strength non-destructive method and is intended to clarify the brand F frost resistance of natural and artificial stones (bricks, concrete), i.e. the number of standard cycles of freezing and thawing (e.g., from +20 to -20°C for 4 hours)needed to reduce the tensile strength of the R samples, saturated with water, by an amount specified by the standard, in particular for 5 or 15% (ΔR/R=0,05 0,15...).
For basic (primary) adopted method [GOST - 10060.1-95], including the production of several samples of samples, each of size n, and the saturation of the samples with water, the initial values of R when the compression of the first sample, thermal Cycling of the other, the destruction of the compression of these samples after different number N of cycles and definitions as the mark F number of cycles needed to reduce R within the limits specified by the standard. Significant scatter of the values of R stone (coefficient of variation of 15...20%) at constant conditions of manufacture and testing of samples leads to a large scatter of sample meansand require a substantial amount of samples (n=25...50) to prove the significance of the change ΔR/R=0,05 0,15...as a result of thermal Cycling. Even with a small value of F≈50 total time thermal Cycling to exceed 6 days. That is they way the main disadvantage of the basic ways - complexity and low efficiency.
Closest to predlagaemom way [GOST - 10060.3-95], which consists in the manufacture of samples, saturated with water, the measurement of relative deformation of the sample (relative change δ volume) during the first freezing to the normalized temperature and thermal Cycling of samples, finding their mark F, and the dependence of F on δ for a particular type of stone and the use of this relationship in the future to determine F by δ when the first freezing of the sample.
The prototype disadvantages - complexity and low efficiency due to the need to investigate the dependence of F(δ) for each type of stone or binder.
The purpose of the invention is to reduce the complexity and increase efficiency.
Goal reach the fact that, as in the prototype water-rich sample is frozen up to the standard temperature, defrost and measure its deformation. But unlike prototype
- before freezing non-destructive method to determine when the compression threshold load for the water-saturated sample, consistent with its long-term strength;
after thawing of the sample is measured residual strain in the direction perpendicular to the preceding compression;
- achieve no less residual deformation cyclizes the m stationary compression of the sample in the same direction from zero to the load, exceeding the threshold is not more than one third;
by repeating these operations, determine the number of cycles required to reduce the limit R long-term strength to the desired value.
The use of non-destructive testing R allows you to identify the brand F test for one sample that has already dramatically reduces the complexity. However, such control must have high accuracy (1...3%) and not to increase the damage of the material, which leads to the choice R of the long-term strength - see patent No. 2305281. Other distinctive operations aimed at replacing more cycles operating cycles mechanical loading equivalent for insertion of damage, for the measure was adopted as the amount of permanent deformation. When replacing cycles mechanical stress must exceed a threshold of not more than 1/3. In this case, the crack shear in compression will not move into the cracks of separation, parallel compression, leading to fragmentation of the sample.
To validate the proposed method implemented in parallel with the basic method of determining the frost resistance [GOST - 10060.1-95] on samples with an edge 15 cm, made from a mixture of Portland cement (1 weight part) type 400, sand (2 concerns), crushed granite 5...20 mm (4.5 century'clock) and water (0,6 concerns). From one batch produced 108 samples fo the mA which differed from the cube with an edge 15 cm, however, what is the point of intersection of two diagonals formed opposite faces (reference point) distance from each other farther (up to 1.5 mm)than the remaining points of these edges that correspond to each other. The samples were verdeli 28 days in water at room temperature, and then 60 days in moist sand at 18...26°C. During the implementation of the basic method, the distance l between the reference points of each sample (100 PCs) was measured using instrumental microscope before and after freeze-thaw durability testing. Residual strain ε was calculated as Δℓ/l. The distance change Δℓ between reference points when implementing the proposed method on 8 samples were led at 20±2°C before and after thermal Cycling using brackets with a variable base and with a measuring cylinder and dial type (intercept 1 μm). Threshold load L0water-saturated sample was determined by recording acoustic emission (AE) with the help of the device AF-15 under cyclic loading and unloading of the sample to zero. In the first cycle, the load L brought up to 11 tons; in the absence of AE at the end of unloading the value L was increased by 5% and so on until until at the end of the load did not arise AE. For L0took an average L of the last two cycles. Thermal Cycling mentioned 8 samples from +20 to -20°C was performed 10 times in a row (decades), and then measured the residual fact deformation is s ℓΔ T. Then the sample was loaded mechanically to load 1,33R 1...2 min and unloaded. Cycles were repeated until such time as the residual strain Δℓ between reference points are not exceeded ΔℓT(12 to 19 cycles). Then spent the next decade of cycles, etc. to reduce ΔR/R=0,12 0,18.... The results of the tests are shown in the table, where the following notation: i is the number of decade of thermal Cycling; ΔεTi= ΔℓT/l - increment relative residual deformation after the first decade of thermal Cycling; Ri- long-term strength before the i-th decade thermal Cycling;i=Δεi/εTi- the equivalence of mechanical and thermal loading; Δεi- increment relative residual deformation during mechanical Cycling after the first decade of cycles;- the amount of cycles and equivalent mechanical loading
(each of 12...19 mechanical cycles). As can be seen from the table, ΔR/R=0,142 when ∑=102...107, and an average of 105. With this in mind, the results of the 50 samples, saturated with water, was thermosensible 105 times (from 20 to -20°C), then for each of them measured residual strain Δℓ and destructive method defined temporal resistance Ri. For Rithe average value of status is vilo and standard deviationfor residual strain εiaverageseemed equal 1448×10-5, Sε=77·10-5,For the other 50 samples without thermal Cycling received=34.8 MPa, S=Of 5.92. As for sample meansthe confidence interval relationslies in the range 0,12 0,20...that is not contrary to the result obtained using the proposed method (0,142) and proves its correctness. The same conclusion holds for the residual strain.
The proposed method is compared with the reference [GOST - 10060.1-95] reduces the amount of testing procedure and increases their efficiency.
The method for determining the frost resistance of stone, which consists in the fact that water-rich sample of stone frozen up to the standard temperature, defrost and measure the deformation, characterized in that before freezing non-destructive method to determine the threshold load that meets the long-term strength of the sample during compression, after a number of cycles measured residual strain thawed sample in the direction perpendicular to the preceding compression, achieve no less residual deformation of cyclic the mere compression of the sample in the same direction from zero to the load, exceeding the threshold is not more than a third, repeating these operations, determine the number of cycles needed to reduce the long-term strength to the desired values.
FIELD: measuring technique.
SUBSTANCE: method comprises heating the heat-shield structure from one side up to a high temperature, cooling the structure, applying marker dots on the section of the outer surface under study, cutting the axisymmetric specimens of the heat-shield structure, applying marker dots on the side of the specimen at a given distance from the inner surface, cutting the specimen over the planes perpendicular to its longitudinal axis and passing through the marker dots into pieces, subsequent heating of the pieces in the atmosphere of an inert gas, recording the change of weight of the pieces, recording the temperature of the beginning of the decrease of weight of each piece, and judging on the spatial temperature distribution from data obtained.
EFFECT: expanded functional capabilities.
FIELD: testing engineering.
SUBSTANCE: device comprises high-frequency generator and inductor connected in series, device for control of heating, system for air supply, device for external cooling, measuring system, unit of contact temperature gauges, and device for bottom clamping connected with the end section of the blade. The device is provided with a means for axial loading, device for top clamping connected with the shelf of the end section of the blade, device for control of axial loading, first dynamometer, device for applying torque, which has the second dynamometer, device for information input, load-bearing frame, contactless temperature gauge, generator of nonstandard signals, oil pumping system, and device for internal cooling.
EFFECT: enhanced reliability of testing.
7 cl, 1 dwg
SUBSTANCE: invention can be used to determine crystalline phase in crystalline glass materials. A sample is treated with solutions of hydrofluoric and sulphuric acid, with subsequent filtration and calcination of the residue. The analysed sample with 10% solution of hydrofluoric acid is treated in a laboratory ultrasonic bath with water heated to 50°C for 5 minutes, with subsequent addition of a 2% solution of sulphuric acid and treatment with ultrasound for 5 more minutes.
EFFECT: faster and simpler process of determining content of crystalline phase in crystalline glass material with retention of its accuracy.
SUBSTANCE: model for compressing rock when evaluating its freeze-thaw resistance consists of a rod of the analysed material, component metal holders with depressions into which the ends of the rod enter, and a fixing structure between supports and ends of the rod. The fixing structure is based on cement which expands during solidification. The depressions in the holders have the least cross sectional area where the rod enters the holder, perpendicular to the axis of the rod.
EFFECT: increased accuracy of determining type of construction materials from freeze-thaw resistance, reduced labour input and cutting on number of tests.
1 dwg, 1 tbl
SUBSTANCE: in the method of evaluating cement activity in water-cement systems, cement is mixed with water, obtaining cement dough which is then put into a mould. For 60-70 seconds change of temperature of the cement dough is measured using at least one temperature sensor from the beginning of mixing to the onset of cement setting. Histograms are drawn for distribution of the obtained values of periods versus the values and cement activity is determined by comparing the obtained histograms with standard histograms. A fibre optic or resistance thermometre is used, preferably with sensitivity less than 0.05°K. A plasticiser can be added when preparing the water-cement mixture.
EFFECT: more accurate and faster method with simplification of its implementation.
4 cl, 4 ex, 1 dwg
FIELD: physics, nuclear engineering.
SUBSTANCE: invention is related to equipment for creation of short-term intense pressure pulses and may be used for testing of structural material samples for resistance to action of shock waves of nuclear explosion (NE), in particular X-ray radiation (XR). Method for imitation of thermomechanical action of NE XR at samples of structural materials includes fixation of exploded foil to tested sample, discharge of electric current pulse that results in foil explosion, and resulting loading of sample by mechanical pressure pulse from explosive shock wave. Besides previously thickness is identified for layer of loaded sample substance sublimated in nature process, and then it is removed from the surface by any of available methods. Then uneven heating is carried out in sample thickness.
EFFECT: provision of possibility to bring reproduced conditions to nature condition of tested sample under thermomechanical action of NE XR.
FIELD: fire safety.
SUBSTANCE: invention relates to fire safety of the buildings and can be used to classify mesh-reinforced brick piers and separating walls with respect to their flame resistance characteristics. The proposed method comprises performing tech inspection, defining the bricklaying type, types of bricks and mortar, the bricklaying elastic stability, the pier support and attachment conditions, determining the probable time of occurrence of limiting flame resistance conditions of mesh-reinforced brick piers at rated load in the conditions of standards fire. Testing the said mesh-reinforced brick piers involves no destruction and incorporates a set of separate quality properties of the mesh-reinforced brick piers. The date and place are selected for quality characteristics to be defined. The aforesaid tech inspection is supplemented by instrument measurements of mesh-reinforced brick pier geometrical sizes at critical sections. The pattern of heating in aforesaid critical sections of piers in fire is determined, as well as temporary compression resistance of bricklaying. The rated load onto mesh-reinforced brick piers is selected for flame resistance test conditions and strains in the pier critical sections are defined.
EFFECT: determination of mesh-reinforced brick pier and separation wall flame resistance involving no natural heating; higher validity of quality control checks and non-destructive tests.
14 cl, 2 dwg
FIELD: fire safety.
SUBSTANCE: invention relates to fire safety of the buildings and can be used to classify brick piers and separating walls with respect to their flame resistance characteristics. The proposed method comprises performing tech inspection, defining the bricklaying type, types of bricks and mortar, the bricklaying elastic stability, the pier support and attachment conditions, determining the probable time of occurrence of limiting flame resistance conditions of plain brick piers at rated load in the conditions of standards fire. Testing the said plain brick piers involves no destruction and incorporates a set of separate quality properties of the plain brick piers. The date and place are selected for quality characteristics to be defined. The aforesaid tech inspection is supplemented by instrument measurements of brick pier geometrical sizes at critical sections. The pattern of heating in aforesaid critical sections of piers in fire is determined, as well as temporary compression resistance of bricklaying. The rated load onto brick piers is selected for flame resistance test conditions and strains in the pier critical sections are defined.
EFFECT: determination of plain brick pier and separation wall flame resistance involving no natural heating; higher validity of quality control checks and non-destructive tests.
12 cl, 5 dwg, 2 ex
FIELD: physics; measurement.
SUBSTANCE: present invention relates to quality control of construction materials, particularly to steel fibre reinforced concrete. The method involves pre-measurement of parametres of current, flowing through an electromagnetic contour lying on the surface of a sample of steel fibre reinforced concrete with a known reinforcement ratio. A calibrated graph of the current parametres versus the reinforcement ratio is plotted. After that, parametres of current flowing through the same contour on the surface of a steel fibre reinforced concrete object with an unknown reinforcement ratio are measured, and using the calibrated graph, the reinforcement ratio of these samples is determined. The reinforcement ratio is determined for steel fibre reinforced concrete with known thickness of the object and known distance between the surface of the object and the part of the object reinforced by the fibres. The electromagnetic contour is made in form of a multiple-turn circular coil, whose diametre is at least twice longer than the fibres. The length of the coil is at least 10 times shorter than its diametre. The frequency of current flowing through the coil lies in the range from 2 kHz to 50 kHz.
EFFECT: determination of the reinforcement ratio of objects made from steel fibre reinforced concrete.
4 cl, 1 dwg
FIELD: construction industry.
SUBSTANCE: concrete or mortar beam is tested for bending. Loads are applied to beam with gradual load weight increase. Then beam deflections are measured in the direction of load action, and conditional-linear "load weight - deflection" dependence is determined, and concrete or mortar elasticity modulus is calculated from the following expression, MPa: E=((Pmax·L3 )/(48·fel·I))·K. Load with weight Pmax is applied to beam within 180 days, and beam deflections are measured from time to time in the direction of load action, and creep coefficient is calculated from the expression: ϕ=(f180-fel)/fel, and creep measure, MPa-1, is calculated from the expression: C0=ϕ/E, where Pmax is maximum load weight value from specified area, kg, L is working beam span, cm, fel is beam deflection at Pmax, cm, I is inertia moment of beam section equaling to (b·h3 )/12, cm4, b is beam width, cm, h is beam height, cm, K is coefficient, cm2·MPa/kg, f180 is beam deflection in 180 days, cm.
EFFECT: reducing duration and labour cost of tests, improving test results' accuracy, and no need to use expensive complex equipment.
2 tbl, 1 ex, 4 dwg
SUBSTANCE: device for testing a lining coating bonding strength of a building construction by means of detachment of the lining coating has a base with two supports equidistant from the longitudinal axis and arranged in an axial longitudinal plane, and a hydraulic press with a closed hydraulic system. The hydraulic press consists of a piston pump with a manual drive and an actuating cylinder linked with a pull-bar capable of a hinged connection with a grabbing pivot equipped with a steel plate in order to stick to the lining coating. There is also a mechanism of the pull-bar pretensioning and a device for tack force measurement of the lining coating. The base has a central hole for the pull-bar installed inside and capable of a lengthwise movement and the piston pump, the actuating cylinder, the mechanism of the pull-bar pretensioning and the device for tack force measurement are arranged in alignment of the central hole in the base, and the pump piston is installed in the piston of the actuating cylinder.
EFFECT: reduced materials consumption and improved transportability; reliability and accuracy of the findings of the device testing.
10 cl, 7 dwg
FIELD: construction; measurement.
SUBSTANCE: invention concerns methods of definition of water mortar properties. On a definition method of water-retaining ability of a water mortar a base sheet is weighed - a fragment of the surface intended for its drawing, a base sheet is weighed with the form installed on it from a dielectric material. The form is equipped by galvanic detecting devices connected to a measuring equipment and forming with a solution mix a galvanic couple, and between a base sheet and the form a grid is placed from the dielectric material which is not absorbing water. A solution mix is filled in the form and maintained. The endurance termination is defined at the moment of the grasping beginning of the solution mix, corresponding to stabilisation of electric pressure in galvanic couple. After that the form and a base sheet are weighed and the water-retaining ability is counted on the received parameters. The invention is developed in dependent points.
EFFECT: increase of the method reliability of a water mortar water-retaining ability definition.
4 cl, 1 ex, 1 dwg
FIELD: manufacture of building materials.
SUBSTANCE: object of invention is testing materials for use in designing compositions of artificial building conglomerates and composites as well as in optimizing compositions. Method of invention involves screen fractionation to determine average size of grains of coarse-grain fraction d1 and that of fine-grain fraction d2, ratio of grain sizes d2/d1, and value of dilution of coarse-grain fraction with fine-grain fraction in terms of formula: α = [(d1 + d2)/d1]3. If d2/d1 > 0.155, degree of compaction Y and, if d2/d1 < 0.155, degree of filling Y are found from formula Y = 2 -
EFFECT: reduced volume of laboratory tests and improved qualitative characteristics of calculated and prepared loose mixtures, for which regulation of desired properties of manufactured materials is ensured.
FIELD: manufacture of building materials.
SUBSTANCE: object of invention is testing materials for use in designing compositions of artificial building conglomerates and composites based on organic and inorganic binders. Method of invention involves screen fractionation to determine average size of grains of coarse-grain fraction d1, mm, and fine-grain fraction d2, mm, ratio of grain sizes d2/d1. Degree of compaction Y at d2/d1 > 0.155 and degree of filling Y at d2/d1 < 0.155 are determined from formula Y = 1 - d2/d1.
EFFECT: enabled determining values of degree of compaction and filling of coarse-grain fractions with fine-grain ones without experimental trials associated with preparation of loose mixtures.
FIELD: manufacture of building materials.
SUBSTANCE: object of invention is testing materials for use in designing compositions of artificial building conglomerates and any-nature composites. Method of invention comprises layer-by-layer filling of volume unit with coarse-grain and fine-grain fractions, determining average size of grains of coarse-grain fraction d1 and that of fine-grain fraction d2, d2/d1 ratio, coarse-grain and fine-grain fraction volumes V1 and V2, m3, respectively, consumed per unit mixture volume (1 m3), coarse-grain fraction free volume value Vn1, coarse-grain fraction volume mass γ1, and degree of diluting coarse-grain fraction with fine-grain fraction α calculated by formula: α = γ1/V1. When d2/d1 > 0.155, degree of compaction of coarse-grain fraction with fine-grain fraction Y is calculated using formula: V = [α(V2-1)+1]/Vn1. Invention makes it possible to determine degree of compaction of one-type fractions with other-type fractions taking into account quantitative interrelations between fraction ratios, between fraction ratios and volume of mixture being formed, between volume of mixture and coarse-grain fraction free volume value, between all them and above-indicated dilution value.
EFFECT: enabled regulation of volume mass and preparation of materials with desired volume-mass characteristics.