A rapid detection method for deformation performance of C30 concrete and internal mortar

Abstract

The present invention discloses a rapid testing method for the deformation properties of C30 concrete and its internal mortar. The method comprises the following steps: sieving coarse aggregate and fine aggregate into coarse aggregate samples and fine aggregate samples of fixed particle size ranges, drying the samples, and placing the dried coarse aggregate samples and dried fine aggregate samples into a test tube, respectively, and placing a pressure head; operating a press to apply a load to the samples in the test tube via the pressure head, and simultaneously collecting the applied load value and the displacement value of the pressure head; obtaining the stress and strain of the granular aggregate in the test tube under axial compression based on the load value, the cross-sectional area value of the test tube, the displacement value, and the initial height values ​​of the coarse and fine aggregate samples in the test tube; and then calculating the elastic modulus and Poisson's ratio of the C30 strength grade concrete and its internal mortar based on the slope value of the approximate straight line segment on the aggregate stress-strain curve. The present invention addresses the structural safety hazard caused by the formula in the current standard that overestimates the deformation index of non-natural aggregate concrete.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering materials, and particularly relates to a method for quickly detecting deformation performance of C30 concrete and internal mortar. Background Art

[0002] Concrete deformation properties are its fundamental mechanical properties. Deformation performance indicators such as concrete's elastic modulus and Poisson's ratio are essential calculation parameters for component deformation verification during the structural design phase. Measuring the elastic modulus and Poisson's ratio of concrete and mortar requires mix design and the preparation of prismatic specimens. After a standard 28-day curing period, test data is collected by attaching strain gauges and installing load cells before the final calculation can be achieved. A complete testing cycle takes at least a month and places high demands on both testing equipment and personnel. Therefore, obtaining measured values ​​of the elastic modulus and Poisson's ratio during the structural design phase is often unavailable. In actual projects, calculations based on formulas in relevant national standards are commonly used to verify component deformation. Currently, the calculation formulas for concrete deformation indicators such as the elastic modulus in relevant national standards are based on the compressive strength of natural aggregate concrete mixed with natural sand and gravel aggregates and have been used for decades. With the rapid development of infrastructure construction in my country over the past three decades, natural sand and gravel aggregate resources have been intensively depleted, and in many areas, natural sand and gravel resources are nearing depletion. In recent years, the country has introduced a series of policies and regulations, strictly restricting the mining of natural sand and gravel, and encouraging the use of solid waste aggregates derived from industrial solid waste to replace natural sand and gravel aggregates in concrete production. Many regions have begun using solid waste aggregate concrete, made from solid waste aggregates, in the construction of structures such as houses and bridges, with C30 strength grade concrete being the most widely used. The large-scale application of solid waste aggregate concrete in structural engineering has become a clear direction for the future development of my country's construction industry. Through optimized mix design, the workability and strength of solid waste aggregate concrete have met general structural engineering requirements, comparable to those of natural aggregate concrete. However, in numerous engineering projects, it has been found that the measured values ​​of deformation performance indicators such as elastic modulus and Poisson's ratio of solid waste aggregate concrete of the same strength grade are generally lower than those of natural aggregate concrete, and the difference is significant. If, during the structural design phase, the elastic modulus and other deformation performance technical indicators of solid waste aggregate concrete are calculated according to the formula based on the compressive strength value of natural aggregate concrete in the relevant standards, the calculated values ​​will be higher than the measured values. Using these high calculated values ​​to verify component deformation may cause the actual deformation of solid waste aggregate concrete components or even structures to exceed the design values, and in severe cases, even lead to component or structure failure, thus leaving serious structural safety hazards during the structural design phase. Therefore, in order to meet the industry development trend of large-scale application of solid waste aggregates in structural concrete, it is necessary to develop a rapid detection method for concrete deformation performance technical indicators that is generally applicable to natural and solid waste aggregate concrete.

[0003] Aggregates account for over 70% of concrete's volume and serve as its primary framework. Numerous studies have shown that aggregate elastic modulus is the primary factor influencing concrete's elastic modulus. In engineering practice, a classic two-phase prediction model based on aggregate elastic modulus is sometimes used to calculate concrete's elastic modulus. However, because most solid waste aggregates originate from industrial tailings and construction waste, they are difficult to process into cylindrical aggregate elastic modulus specimens of the standard dimensions specified in national standards. Consequently, aggregate elastic modulus values ​​cannot be obtained, making the classic two-phase prediction model inapplicable. Furthermore, measuring the elastic modulus of single-particle solid waste aggregates fails to accurately calculate the concrete elastic modulus because it cannot reflect the effects of concrete's internal constraints on the granular aggregate. Rapidly testing the actual elastic deformation properties of granular aggregates and reliably applying them to the calculation of deformation performance indicators such as the concrete elastic modulus has become a pressing issue in the engineering community, with significant safety, economic, and environmental implications.

[0004] In order to solve the above problems, a rapid detection method for the deformation performance of C30 concrete and its internal mortar was developed. Summary of the Invention

[0005] The present invention addresses the shortcomings of the prior art by providing a rapid method for testing the deformation properties of C30 concrete and its internal mortar. This method is adaptable to C30 concrete mixed with various types of aggregates and offers higher accuracy than the current standard formula applicable only to natural aggregate concrete, thereby improving structural safety.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a method for quickly detecting the deformation performance of C30 concrete and internal mortar, characterized in that the method comprises the following steps:

[0007] S1. First, test the 24-hour saturated surface dry water absorption of coarse aggregate used for mixing C30 strength grade concrete, sieve the coarse aggregate to obtain a coarse aggregate sample, dry the coarse aggregate sample, and place the dried coarse aggregate sample into a first test cylinder to a fixed height a. Then, place a first pressure head on the dried coarse aggregate sample in the first test cylinder to obtain a test cylinder with a pressure head a.

[0008] Screening fine aggregate used for mixing C30 strength grade concrete to obtain a fine aggregate sample, drying the fine aggregate sample, placing the dried fine aggregate sample into a second test cylinder to a fixed height b, and then placing a second pressure head on the dried fine aggregate sample in the second test cylinder to obtain a test cylinder with a pressure head b;

[0009] S2. Place the test cylinder a with the pressure head obtained in S1 on a press, start the press, and uniformly apply a load to a fixed load value a to the dried coarse aggregate sample in the first test cylinder through the first pressure head. Simultaneously, collect the fixed load value a and the displacement value a of the first pressure head during the entire process.

[0010] The test cylinder b with the pressure head obtained in S1 is placed on a press, the press is started, and a load is uniformly applied to the dried fine aggregate sample in the second test cylinder through the second pressure head to a fixed load value b, while the fixed load value b of the applied load and the displacement value b of the second pressure head are synchronously collected throughout the entire process;

[0011] S3. Dividing the fixed load value a obtained in S2 by the cross-sectional area of ​​the first test cylinder to obtain a stress value of the dried coarse aggregate sample;

[0012] Dividing the fixed load value b obtained in S2 by the cross-sectional area of ​​the second test cylinder to obtain the stress value of the dried fine aggregate sample;

[0013] S4, dividing the displacement value a obtained in S2 by the fixed height value a in S1 to obtain the strain value of the dried coarse aggregate sample;

[0014] The displacement value b obtained in S2 is divided by the fixed height value b in S1 to obtain the strain value of the dried fine aggregate sample;

[0015] S5. Draw a stress-strain curve of the dried coarse aggregate sample according to the stress value of the dried coarse aggregate sample obtained in S3 and the strain value of the dried coarse aggregate sample obtained in S4;

[0016] Drawing a stress-strain curve of the dried fine aggregate sample according to the stress value of the dried fine aggregate sample obtained in S3 and the strain value of the dried fine aggregate sample obtained in S4;

[0017] S6. Calculate the slope of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying obtained in S5. E ca ;

[0018] Calculate the slope of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample obtained in S5 E fa ;

[0019] S7. The slope of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying obtained in S6 E caand the slope of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample E fa , the calculation formula for the elastic modulus of C30 strength grade concrete is:

[0020] ;

[0021] Where: E c —Elastic modulus value of C30 strength grade concrete;

[0022] α —Moisture coefficient; when the 24h saturated dry water absorption of the coarse aggregate in S1 is ≤3%, α =1.0; when the 24h saturated dry water absorption of the coarse aggregate in S1 is greater than 3%, α =0.92;

[0023] E ca —The slope of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying;

[0024] E fa —The slope of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample;

[0025] The calculation formula for the internal mortar elastic modulus value of C30 strength grade concrete is:

[0026] ;

[0027] Where: E m —Internal mortar elastic modulus value of C30 strength grade concrete;

[0028] E fa —The slope of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample;

[0029] The calculation formula for the internal mortar Poisson's ratio of C30 strength grade concrete is:

[0030] ;

[0031] Where: m m —Poisson’s ratio of internal mortar for C30 strength grade concrete;

[0032] E fa —The slope of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample;

[0033] When the fine aggregate in S1 is river sand, the calculation formula for the elastic modulus of C30 strength grade concrete is:

[0034] ;

[0035] Where: E c —When the fine aggregate is river sand, the elastic modulus value of C30 strength grade concrete;

[0036] α —Moisture coefficient; when the 24h saturated dry water absorption of the coarse aggregate in S1 is ≤3%, α =1.0; when the 24h saturated dry water absorption of the coarse aggregate in S1 is greater than 3%, α =0.92;

[0037] E ca —The slope of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying;

[0038] When the fine aggregate in S1 is river sand, the calculation formula for the internal mortar Poisson's ratio of C30 strength grade concrete is:

[0039] ;

[0040] Where: m c — When the fine aggregate is river sand, the internal mortar Poisson’s ratio of C30 strength grade concrete;

[0041] E ca —The slope value of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying.

[0042] Preferably, the particle size of the coarse aggregate in S1 is ≥4.75 mm, and the particle size of the coarse aggregate sample is 9.5 mm to 13.2 mm; the height of the first test cylinder is 128 mm, and the inner diameter is 150 mm; and the fixed height value a is 100 mm.

[0043] Preferably, the temperature of the drying treatment in S1 is ≤100° C. and the time is ≤4 h.

[0044] Preferably, the uniformly applied load in S2 is to a fixed load value a of 400 kN.

[0045] Preferably, the particle size of the fine aggregate in S1 is less than 4.75 mm, and the particle size of the fine aggregate sample is in four particle size ranges of 300 μm to 600 μm, 600 μm to 1.18 mm, 1.18 mm to 2.36 mm, and 2.36 mm to 4.75 mm; the height of the second test cylinder is 70 mm, the inner diameter is 77 mm, and the fixed height value b is 50 mm.

[0046] Preferably, the uniformly applied load in S2 is to a fixed load value b of 25 kN.

[0047] Preferably, the first test cylinder and the second test cylinder are both round test cylinders made of steel.

[0048] Preferably, the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying in S6 is a strain value of 50000 10 -6 Up to 150,000 × 10 -6 The stress-strain curve between the dried fine aggregate sample stress-strain curve is approximately a straight line segment from the stress value of 0.5MPa to the end point of the curve stress-strain curve.

[0049] Compared with the prior art, the present invention has the following advantages:

[0050] The present method examines the stress and strain of granular aggregate in a test tube under axial compression. It then calculates the elastic modulus and Poisson's ratio of C30 strength grade concrete and internal mortar based on the slope of the approximate straight line segment on the aggregate stress-strain curve. This method addresses the structural safety hazards caused by the long testing cycles, high equipment and personnel requirements for deformation performance indicators such as the elastic modulus and Poisson's ratio of concrete and internal mortar in related technologies, as well as the high calculated values ​​for solid waste aggregate concrete in the formulas in relevant standards. This method provides a new rapid testing method for deformation performance indicators such as the elastic modulus and Poisson's ratio of concrete and internal mortar, improving structural reliability.

[0051] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of coarse aggregate sample before and after loading in Example 1 of the present invention.

[0053] Figure 2 The 24 kinds of coarse aggregate after drying in Example 1 of the present invention s - e curve chart.

[0054] Figure 3 (a) is the RCA coarse aggregate after drying in Example 1 of the present invention s - e Secant plot of the curve at different strain intervals.

[0055] Figure 3 (b) is the MSG coarse aggregate after drying in Example 1 of the present invention s - e Secant plot of the curve at different strain intervals.

[0056] Figure 4 (a) is the strain value in Example 1 of the present invention e ca Increased to 50,000×10 -6 Simulation loading diagram of DSC coarse aggregate specimen when .

[0057] Figure 4 (b) is the strain value in Example 1 of the present invention e ca Increased to 150,000×10 -6 Simulation loading diagram of DSC coarse aggregate specimen when .

[0058] Figure 5 The DSC coarse aggregate simulation and actual measurement in Example 1 of the present invention s - e curve chart.

[0059] Figure 6 (a) is a schematic diagram of the calculated and measured elastic moduli of natural aggregate concrete based on different standard formulas in Example 1 of the present invention.

[0060] Figure 6 (b) is a schematic diagram of the calculated and measured elastic modulus of ordinary density solid waste coarse aggregate concrete based on different standard formulas in Example 1 of the present invention.

[0061] Figure 7 This is the XRD spectrum of the normal density tailings solid waste coarse aggregate in Example 1 of the present invention.

[0062] Figure 8 Schematic diagram of predicted and measured values ​​of concrete elastic modulus based on the classic two-phase prediction model in Example 1 of the present invention.

[0063] Figure 9 The different coarse aggregates in Example 1 of the present invention Compared with the measured concrete elastic modulus E c Linear regression analysis graph.

[0064] Figure 10 This is the pore size distribution diagram of solid waste coarse aggregate MSG and natural coarse aggregate DG in Example 1 of the present invention.

[0065] Figure 11The dry samples of coarse aggregate DG, RCA, RSA and HSG in Example 1 of the present invention and the saturated surface dry coarse aggregate s - e curve chart.

[0066] Figure 12 In Example 1 of the present invention and Linear regression analysis graph.

[0067] Figure 13 This is a comparison chart of the calculated values ​​of formula (7) in Example 1 of the present invention and the measured values ​​in the literature.

[0068] Figure 14 In Example 1 of the present invention and Linear regression analysis graph.

[0069] Figure 15 The four dried fine aggregate samples in Example 2 of the present invention are of four particle size ranges. s - e curve chart.

[0070] Figure 16 (a) is the 4 kinds of dried fine aggregate samples in Example 2 of the present invention with a particle size of 1.18mm~2.36mm. s - e curve chart.

[0071] Figure 16 (b) is the 4 kinds of dried fine aggregate samples in Example 2 of the present invention with a particle size of 0.60mm~1.18mm. s - e curve chart.

[0072] Figure 17 is the embodiment 2 of the present invention and Linear regression analysis graph.

[0073] Figure 18 is the embodiment 2 of the present invention and Linear regression analysis graph.

[0074] Figure 19 is the embodiment 3 of the present invention 、 and 3D surface fitting plot.

[0075] Figure 20 is the embodiment 3 of the present invention 、 Fitting diagram with three-dimensional plane.

[0076] Figure 21 is the embodiment 3 of the present invention 、 and Schematic diagram of the 95% confidence interval.

[0077] Figure 22 This is a comparison chart of the calculated values ​​in Example 3 of the present invention and the measured values ​​in the literature. DETAILED DESCRIPTION Example 1

[0078] This embodiment provides a method for quickly detecting the deformation performance of C30 concrete when the fine aggregate is river sand, comprising the following steps:

[0079] Ten types of natural gravel and pebbles with different lithologies were selected, namely limestone gravel (LG), dolomite gravel (DG), sandstone gravel (SG), tuff gravel (TG), andesite gravel (AG), basalt gravel (BG), conglomerate pebble (CP), fine-grained granite gravel (FG), interior fine granite gravel (IG), and coarse-grained granite gravel (GG).

[0080] Fourteen types of solid waste were selected, namely: recycled concrete aggregate (RCA), recycled self-combusted coal gangue concrete aggregate (RSA), sandy mudstone unburned coal gangue (MUG), kaolinite mudstone unburned coal gangue (KUG), sandstone unburned coal gangue (SUG), in-situ blended self-combusted coal gangue (IGS), self-combusted coal gangue with short combustion period (SGS), self-combusted coal gangue with medium combustion period (SGS), and self-combusted coal gangue with medium combustion period (SUG). Period (SGM), Self-combusted Coal Gangue with Long Combustion Period (SGL), Domestic Sludge Ceramicite (DSC), Calcined Foamed Coal Gangue Ceramicite (CFC), Iron Waste Rock (IWR), Man-made Marble Sheet Waste (MSW), and Man-made Granite Sheet Waste (GSW);

[0081] Ten kinds of natural coarse aggregates and 14 kinds of crushed solid waste were screened one by one and screened into coarse aggregates with particle sizes ranging from 4.75 mm to 19.5 mm. The 24-hour saturated dry water absorption rate of each coarse aggregate was then tested ( W 24h ), and were mixed with river sand to make C30 strength grade concrete. The particle size of the river sand was less than 4.75 mm, and the apparent density was 2591 kg / m 3 , bulk density is 1480kg / m 3, water absorption rate is 2.4%, stone powder content is 1.66%;

[0082] According to the national standard "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), the compressive strength value of 28d concrete cube is tested f cu , see Table 1, and by adding load sensors and sticking strain gauges on the specimens, the static elastic modulus of 28d concrete was detected. E c and Poisson's ratio m c , see Table 1. After subtracting the amount of coarse aggregate from the concrete mix ratio, mortar prism specimens were prepared. According to the industry standard "Standard for Test Methods for Basic Properties of Building Mortar" (JGJ / T 70-2009), the static elastic modulus of the mortar at 28 days was tested by adding load cells and attaching strain gauges to the specimens. E m , see Table 1;

[0083] Table 1 Mechanical properties of 24 types of coarse aggregate concrete

[0084]

[0085] S1. Screen 10 types of natural coarse aggregates and 14 types of crushed solid wastes one by one to obtain 24 coarse aggregate samples with a particle size of 9.5 mm to 13.2 mm. Dry the 24 coarse aggregate samples separately and place the 24 dried coarse aggregate samples into a first circular steel test cylinder with a base to a fixed height a of 100 mm. Then, place a first pressure head with a diameter of 149 mm on the dried coarse aggregate samples in the first test cylinder to obtain a test cylinder a with a pressure head. The first test cylinder has a height of 128 mm, an inner diameter of 150 mm, and a wall thickness of 12 mm. The drying temperature is ≤ 100° C. and the drying time is ≤ 4 h.

[0086] S2. Place the test cylinder a with the pressure head obtained in S1 on a WAW-1000 electro-hydraulic servo press, start the press, and uniformly apply a load to the coarse aggregate sample after drying in the first test cylinder through the first pressure head to a fixed load value a. Unload the load after it reaches a fixed load value a of 400 kN within 10 min ± 30 s. During the loading process, the electro-hydraulic servo pressure testing machine automatically and synchronously collects the fixed load value a data applied to the first pressure head and the displacement value a data of the first pressure head, which is the axial compressive load value of the coarse aggregate sample after drying in the first test cylinder ( F ) and axial displacement value (△ h ),like Figure 1 As shown;

[0087] S3. Use the axial compressive load value of the coarse aggregate sample after drying in the first test tube obtained in S2 F Divide by the internal circular cross-sectional area of ​​the first test cylinder S ( S can be d =150mm), the axial stress values ​​of 24 kinds of coarse aggregate samples after drying can be obtained s ca , the calculation formula is shown in formula (1):

[0088] (1)

[0089] S4, using the axial displacement value of the coarse aggregate sample after drying in the first test tube obtained in S2 h Divided by the fixed height a of the dried coarse aggregate sample in the first test tube in S1, which is 100 mm, the axial strain values ​​of the 24 dried coarse aggregate samples can be obtained. e ca , the calculation formula is shown in formula (2):

[0090] (2)

[0091] S5. Axial stress values ​​of 24 dried coarse aggregate samples obtained in S3 s ca and the axial strain values ​​of the 24 dried coarse aggregate samples obtained in S4 e ca Draw the stress-strain curves of 24 kinds of coarse aggregate samples after drying ( s - e curve), see Figure 2 ;

[0092] Depend on Figure 2 It can be seen that the stress and strain of the 24 coarse aggregate samples after drying are exponentially related. The regression function is shown in formula (3). The regression coefficient in formula (3) is a 、 b 、 c The values ​​are shown in Table 2, and the determination coefficient can be seen R 2 All are greater than 0.99, indicating that the rationality and fit of the regression function are good;

[0093] (3)

[0094] Table 224 Coarse aggregate samples after drying s - e The regression coefficient of the curve and R 2

[0095]

[0096] S6. Calculate the slope of the approximate straight line segment on the stress-strain curve of the 24 dried coarse aggregate samples obtained in S5. E ca ;

[0097] Depend on Figure 2 It can be seen that in the small strain value range of the early loading period, the coarse aggregate samples after drying s - e The curves are close to straight lines; in order to accurately determine the coarse aggregate sample after drying s - e The linear interval on the curve that is closest to the straight line is based on the actual measurement as shown in formula (3) s - e The high fitting of the curve regression function ( R 2 >0.99), calculate the regression of each dried coarse aggregate sample obtained in S5 s - e The strain values ​​on the curve are [0, 50000 10 -6 ),[0, 150000 10 -6 ]、[50000 10 -6 , 150000 10 -6 ] and [50000 10 -6 , 200000 10 -6 ]The curve lengths of the four strain intervals L c , curve length L c The calculation formula is shown in formula (4), where is the first-order derivative of the regression function of the curve of formula (3); by comparing the close coefficient d Numerical analysis of the length of the curve in the above different strain ranges L c Secant length L s The degree of proximity, d The smaller the value, the L c The closer L s The closer the curve is to a straight line, the more widely used solid waste coarse aggregate RCA and new solid waste coarse aggregate MSG are used as examples to draw a calculation diagram of different strain ranges of the two coarse aggregate samples after drying. Figure 3 ;

[0098] proximity coefficient d The calculation formula is shown in formula (5), and the results are shown in Table 3. The last line in the table shows the approximation coefficients for different strain ranges. d average value;

[0099] (4)

[0100] (5)

[0101] Table 3 Approach coefficient d 1 10 -6

[0102]

[0103] From Table 3, we can see that the strain range [0, 150000 10 -6 ]of d The average value is the largest, which is obviously not suitable as a linear interval; the strain interval [0, 50000 10 -6 )of d The average value is greater than the interval [50000 10 -6 , 150000 10 -6 ], and is affected by the poor fitting accuracy of the exponential regression function near the origin. Based on the measured s - e Curved d The value should be even larger, see Figure 3 , so this interval is not suitable as a linear interval; Figure 2 and Figure 3 The local enlarged image shows that the strain growth rate is greater than the stress growth rate in this interval.

[0104] The curve deflects toward the strain axis, so this interval can be defined as the coarse aggregate sample after drying. s - e Initial nonlinear interval of the curve; strain interval [50000 10 -6 , 150000 10 -6 ]of d The average value is the smallest, indicating that the curve in this interval is closest to a straight line; Figure 2 and Figure 3 It can also be seen that the stress and strain in this interval increase approximately in proportion, so this interval can be defined as the coarse aggregate sample after drying. s - eLinear range of curve; strain range [50000 10 -6 , 200000 10 -6 ]of d The average value is compared with the linear interval [50000 10 -6 , 150000 10 -6 ] increases, indicating that the curve becomes nonlinear again after passing through the linear interval. Figure 2 and Figure 3 It can also be seen that when the strain value >150000 10 -6 After that, the stress growth rate is greater than the strain growth rate, and the curve deflects toward the stress axis, so the strain value can be >150,000 10 -6 The strain range is defined as the coarse aggregate sample after drying s - e The late nonlinear interval of the curve.

[0105] In this embodiment, the coarse aggregate sample after drying during the loading process s - e The slope of the approximate straight line segment in the linear range of the curve is defined as the average elastic modulus of the coarse aggregate sample after drying (Average elastic modulus of coarse aggregate, referred to as E ca ), the calculation formula is shown in formula (6), and the coarse aggregate samples after drying in this embodiment calculated according to formula (6) are s - e The slope of the approximate straight line segment (linear interval) of the curve is the average elastic modulus of the coarse aggregate sample after drying. E ca The values ​​are detailed in Table 4;

[0106] (6)

[0107] Where: E ca is the average elastic modulus of the coarse aggregate sample after drying, MPa; e ca1 Coarse aggregate sample after drying s - e The strain value at the starting point of the linear interval of the curve, e ca1 =50000×10 -6 ; e ca2 Coarse aggregate sample after drying s - e The strain value at the end point of the linear interval of the curve, e ca2 =150000×10 -6 ; s ca1 Coarse aggregate sample after drying s - e Strain value on the curve e ca1 =50000×10 -6 Stress value at , MPa; s ca2 Coarse aggregate sample after drying s - e Strain value on the curve e ca2 =150000×10 -6 Stress value at , MPa;

[0108] Table 4 Technical indicators of 24 kinds of coarse aggregate samples after drying

[0109]

[0110] Since the loading deformation process of the coarse aggregate sample after drying in the first test tube cannot be observed, in order to accurately analyze the deformation development process of the coarse aggregate sample after drying during loading, it is necessary to clarify E ca The loading process of DSC coarse aggregate samples was simulated and analyzed using EDEM discrete element software to investigate the correlation between the loading process and the elastic deformation properties of the coarse aggregate samples. Based on the Hertz-Mindlin model in EDEM 2020 software, the simulated sample particles of DSC coarse aggregate were set according to various measured technical indicators.

[0111] Coarse aggregate is a kind of granular material. The deformation of granular material has two basic forms: structural deformation and particle deformation. Structural deformation is caused by particle displacement, including displacement deformation caused by insufficient coordination number, i.e., the number of contacting particles, and fracture deformation caused by particle breakage. Particle deformation is the deformation of particles caused by external forces, including elastic deformation and plastic deformation. Coarse aggregates used in structural concrete are all brittle materials, so it can be considered that the particle deformation of coarse aggregates during loading is elastic deformation. Elastic deformation is related to the elastic deformation properties, particle size and stacking state of coarse aggregates. The 9.5mm~13.2mm single-particle size specimens used in the test eliminate the influence of coarse aggregate particle size changes. The ratio of the inner diameter of the first test cylinder to the maximum particle size of the specimen is D / d max >5, and the adverse effects of size effect are eliminated. The irregular particle content of various samples is low, see Table 4. Ic Therefore, when a small amount of sample damage occurs, the stacking states of different samples are relatively close. In summary, the particle deformation of coarse aggregate samples during loading is mainly related to their elastic deformation properties.

[0112] The simulation loading process of DSC coarse aggregate specimens can be found in Figure 4 The pressure at the beginning of the simulated loading caused some DSC sample particles to displace, changing the coordination number of the contacting particles. Since spherical particles require a maximum of 12 coordinations to be stable, the sample displacement deformation increases rapidly, which is consistent with the measured s - e The curve shows a sudden increase in strain in the initial nonlinear range, see Figure 2 and Figure 3 Partial enlarged view. When the strain value e ca Increased to about 50000×10 -6 When the particle coordination reconstruction is complete, the structural deformation is almost zero, see Figure 4 (a). After that, the load is transferred downwards between the stably stacked particles, and the surface particles are the first to break and destroy. The broken small particles continue to accumulate on the surface, gradually increasing the compressive area of ​​the specimen, and then reducing the rate at which the particle stress increases with the increase in load, so that most particles below the surface do not break and produce elastic deformation, which is consistent with the measured s - e The stress and strain shown in the linear range of the curve are approximately proportional. s - e The slope of the approximate straight line segment of the curve is the average elastic modulus of the coarse aggregate E ca This value reflects the elastic deformation performance of most coarse aggregate samples except the surface layer, so it can be used as a technical indicator to evaluate the elastic deformation performance of granular coarse aggregate under confined compression.

[0113] When the strain value e ca Increased to about 150,000×10 -6 When the fractured small particles have filled the gaps in the sample within the thickness of about 10mm on the surface, see Figure 4 (b). The stress-bearing area of ​​the specimen no longer increases, and the particle stress increases rapidly, leading to intensified fracture damage. After that, particle fracture and coordination reconstruction occur alternately, and the proportion of structural deformation in the total deformation continues to increase. The particle expansion also causes the specimen volume to increase, reducing the strain growth rate, which is consistent with the measured s - e The curve shows a sudden increase in stress in the late nonlinear interval. Figure 5 It can be seen that the simulation curve is basically consistent with the measured curve. Eca The value is measured E ca The value is 98.60%, which shows that the simulation loading process is highly consistent with the measured loading process, and the two can verify each other.

[0114] The formulas for calculating the elastic modulus of normal-weight concrete (NC) and lightweight concrete (LC) in relevant standards in China, the United States, and Europe are shown in Table 5. It can be seen that these formulas are mainly based on the compressive strength of concrete. According to the European standard FIP Model Code 2010, the measured concrete cube compressive strength is converted to Converted to cylindrical compressive strength and Then, substitute the formula in Table 5 to calculate the elastic modulus of C30 strength grade concrete mixed with different coarse aggregates and river sand. The results are shown in Figure 6 .

[0115] Table 5 Calculation formulas for elastic modulus of concrete in different standards

[0116]

[0117] Depend on Figure 6 The comparison of the elastic modulus calculated and measured for natural coarse aggregate concrete (a) shows that the error of the calculated value of the American standard ACI 318-19 is the smallest, with a mean square error (MSE) of 12.9. The errors of the calculated values ​​of the Chinese standards GB 50010-2010 and JGJ / T12-2019 are in the middle, but the calculated values ​​of 9 out of 10 different coarse aggregate concretes exceed the measured values, with MSE = 61.4. Although the calculated value of FIP Model Code 2010 has the largest error, the calculated values ​​of 9 coarse aggregate concretes also exceed the measured values, with MSE = 85.2. However, because it introduces the aggregate lithology coefficient into the calculation formula , taking into account the influence of coarse aggregate type on the elastic modulus of concrete, the change trend of its calculated value is closest to the measured value. This shows that the type of coarse aggregate does have a greater impact on the elastic modulus of concrete of the same strength grade.

[0118] The calculated elastic moduli of the four lightweight concretes based on natural coarse aggregate TG and solid waste coarse aggregate HSG, CFC, and DSC are close to the measured values. Figure 6 This is because the strength of light coarse aggregate is generally lower than the strength of mortar inside concrete, and concrete failure often occurs first in light coarse aggregate. This makes the mortar's skeleton effect in lightweight concrete actually stronger than that of light coarse aggregate, and the influence of mortar's elastic modulus on concrete's elastic modulus is also greater than that of light coarse aggregate. Figure 6It can also be seen that the measured elastic modulus values ​​for the four types of lightweight concrete follow the same trend as that for mortar. The elastic modulus of mortar with the same fine aggregate type is primarily influenced by the water-cement ratio, which is also a major factor affecting concrete strength. Therefore, the calculation formulas based on concrete strength within each standard can achieve good accuracy for lightweight concrete.

[0119] The elastic modulus calculated by the formulas in the Chinese, American and European standards for ordinary density solid waste coarse aggregate concrete all exceeded the measured values ​​by a large margin, exceeding by 45.5%, 15.8% and 52.5% respectively. Figure 6 (b). Ordinary density coarse aggregate plays the main role of skeleton in concrete. Its elastic modulus directly affects the elastic modulus of the prepared concrete. The elastic modulus of coarse aggregate is greatly affected by the hardness of its internal components. Because it comes from industrial and mining solid waste, the composition of solid waste coarse aggregate is often more complex than that of natural coarse aggregate. The XRD patterns of 7 types of solid waste coarse aggregates from tailings can be found in Figure 7 , from top to bottom in the figure are: IWR, SUG, ISG, MSG, LSG, KUG and MUG. It can be seen that MUG, KUG, LSG, MSG and ISG all contain low-hardness minerals kaolinite and mica. RSA is prepared by crushing ISG coarse aggregate concrete, and also contains low-hardness mineral components. The old mortar in RCA and the adhesives in MSW and GSW are also low-hardness components inside the coarse aggregate. The low-hardness component makes the elastic modulus of solid waste coarse aggregate lower than that of natural coarse aggregate. If the formula based on natural coarse aggregate concrete is used for calculation, the result will be higher. IWR and SUG have fewer mineral types, and their mineral composition is close to natural quartz sandstone. Therefore, the calculated value based on the American standard ACI318-19 is closer to the measured value, see Figure 6 (b) This also demonstrates from another perspective the inapplicability of the formulas in major domestic and international standards to concrete made of solid waste coarse aggregate with complex components.

[0120] The classical two-phase prediction model of concrete elastic modulus is shown in Equations (1)-(6) in Table 6. Where the elastic modulus of coarse aggregate is E a The volume fraction of coarse aggregate can be calculated according to formula (7) in Table 6. V a It can be calculated from the concrete mix ratio, and the mortar elastic modulus is E m Take the measured value and calculate the predicted value of concrete elastic modulus of the classic two-phase prediction model. Figure 8 It can be seen that except for the three types of solid waste light coarse aggregate concrete, HSG, CFC, and DSC, the classic models have high prediction accuracy, but the prediction errors of the other concretes are large. The prediction values ​​of most models for solid waste aggregate concrete also greatly exceed the measured values, with an average excess of 26.58%.

[0121] Table 6 Calculation formula for elastic modulus of classic two-phase predicted modulus concrete

[0122]

[0123] Predicting concrete elastic modulus using standard internal formulas or the classic two-phase model requires prior knowledge of concrete compressive strength or mortar elastic modulus. Because the preparation and curing periods for concrete compressive strength and mortar elastic modulus specimens are identical to those for concrete elastic modulus specimens, actual measurements of concrete elastic modulus are often less effective. Developing a rapid prediction method for concrete elastic modulus that fully accounts for the elastic deformation properties of coarse aggregate would be even more valuable in guiding engineering practice.

[0124] During the loading process, the lateral deformation of the coarse aggregate is constrained by the rigid test tube, and the stress state is closer to the coarse aggregate constrained by the internal mortar in the concrete. Therefore, the average elastic modulus of the coarse aggregate proposed in this embodiment is E ca It should reflect the actual elastic deformation performance of coarse aggregate in concrete, and thus be linearly related to the elastic modulus of concrete. E ca Compared with the measured concrete elastic modulus E c The regression analysis results are shown in Figure 9 ,visible, E ca and E c Linear correlation, R 2 =0.89.

[0125] Because they come from tailings and construction waste, solid waste coarse aggregates generally have high porosity and small pore size. The pore size distribution of solid waste coarse aggregate MSG and natural coarse aggregate DG obtained by mercury intrusion test can be found in Figure 10 The porosity of MSG is as high as 29.44%, and the average pore size based on volume is 308.6nm. Due to the capillary effect, the micropores with a pore size of less than 500nm inside the aggregate are easily saturated with water and retain moisture. Therefore, the moisture content of the solid waste coarse aggregate inside the concrete elastic modulus specimen cured in an environment with a humidity of ≥95% as specified by the national standard will be close to the saturated surface dry water absorption rate. The water wedge effect and lubrication effect will significantly reduce the stiffness of the wet coarse aggregate. Therefore, the calculated based on the dry sample E ca It cannot accurately reflect the actual elastic deformation properties of dry coarse aggregate close to the saturated surface inside the concrete, thus affecting its E c correlation.

[0126] Take the saturated surface dry coarse aggregate sample and load it again. The dry samples and saturated surface dry samples of representative coarse aggregates DG, RCA, RSA and HSG with different water absorption rates are s - e Curve see Figure 11 , calculate the average elastic modulus of saturated surface dry coarse aggregate See Table 4 for the values. Comparison Both decreased, and the extent of the decrease was affected by the 24h saturated surface dry water absorption rate of coarse aggregate. W 24h Two moisture states of coarse aggregate DG with low water absorption s - e The curves are closer. Comparison The decrease is also small. Two moisture states of high water absorption coarse aggregate RSA and HSG s - e There is a clear difference in the curves. Also relatively In addition to RCA, water absorption W 24h >3% coarse aggregate The decline was large, with an average . RCA and W 24h ≤3% coarse aggregate The decrease is so small that it can be almost ignored. Although the RCA of recycled concrete coarse aggregate W 24h =4.92%, but because the water mainly enters the old mortar wrapped on the surface of RCA, and the water absorption rate of the old natural coarse aggregate inside is still low, the water absorption rate of the old coarse aggregate is measured after cleaning the old mortar on the surface. W 24h =1.73%. Because the old natural coarse aggregate with low water absorption is the main component that determines the elastic deformation performance of RCA, , the decline is close to W 24h ≤3% coarse aggregate. RSA coarse aggregate concrete prepared by crushing ISG coarse aggregate concrete has W 24h =6.79%, so its It can be seen that for recycled concrete coarse aggregate, its Comparison The degree of decline mainly depends on the water absorption rate of the old coarse aggregate. and Regression analysis was performed again, and the results are shown in Figure 12 , R 2=0.92>0.89, it can be seen that the average elastic modulus of dry coarse aggregate using saturated surface The elastic modulus of concrete can be predicted with better accuracy. The hypothesis test of the regression model shows that the residuals follow a normal distribution and the model is accurate and reliable.

[0127] For C30 strength grade concrete mixed with river sand, the elastic modulus of C30 strength grade concrete can be calculated using the semi-empirical formula shown in formula (7): E c .

[0128] ( )

[0129] Where: α is the moisture coefficient, for the 24h saturated surface dry water absorption rate W 24h ≤3% of the coarse aggregate and the internal old coarse aggregate are natural coarse aggregates in recycled concrete coarse aggregates. α =1.0, for other W 24h >3% coarse aggregate, where α =0.92.

[0130] The calculated values ​​of the elastic modulus of C30 strength grade concrete calculated using formula (7) of this embodiment and the measured values ​​(Table 1) and the calculated values ​​based on the formulas in Chinese, American and European standards are shown in Table 7. It can be seen that the calculated values ​​of formula (7) of this embodiment are closest to the measured values ​​and have higher accuracy than the calculated values ​​of the formulas in the standards of various countries.

[0131] Table 7 Measured and calculated values ​​of elastic modulus of 24 types of coarse aggregate concrete GPa

[0132]

[0133] Since formula (7) is a semi-empirical formula obtained based on the measured data of this embodiment, in order to test whether it has wide applicability and can guide engineering practice, the measured data of elastic modulus of C30 strength grade river sand concrete prepared by RCA, MUG, KUG, LSG, MSG, HSG and DSC in the relevant literature that have been published are selected to test the reliability of formula (7). The comparison results of the calculated values ​​of formula (7) and the measured values ​​in the literature are shown in Figure 13 , it can be seen that the relative errors of the calculated values ​​do not exceed ±10%. R 2 =0.895, MSE=0.897, indicating that Equation (7) has good applicability for various aggregate types, especially solid waste coarse aggregate concrete, and can achieve ideal calculation accuracy. At the same time, compared with the calculated values ​​of formulas in relevant domestic and international standards and the predicted values ​​of the classic two-item prediction model, the calculated value of Equation (7) proposed in this embodiment has higher accuracy, is applicable to a wider range of coarse aggregate types, and has high engineering practicality and guidance.

[0134] Coarse aggregate has a strong restraining effect on the radial deformation of concrete, so the Poisson's ratio of concrete should also be closely related to the elastic deformation performance of granular coarse aggregate. m c Average elastic modulus of coarse aggregate Linear regression analysis was performed, and the results are shown in Figure 14 ,visible m c and Linear correlation, R 2 =0.873, using Poisson's ratio of concrete can be calculated m c Based on the average elastic modulus of saturated surface dry coarse aggregate Poisson's ratio of concrete m c The regression analysis results are consistent with those based on There is not much difference. R 2 =0.877, so in order to simplify the detection process and facilitate calculation, this embodiment adopts the average elastic modulus of coarse aggregate. The semi-empirical formula for calculating the Poisson's ratio of concrete is used.

[0135] For C30 strength grade concrete mixed with river sand, the Poisson's ratio of concrete can be calculated using the semi-empirical formula shown in formula (8): m c :

[0136] (8)

[0137] The data in all figures and tables in this embodiment are the average values ​​of three groups of samples.

[0138] Example 2

[0139] The method for quickly detecting deformation performance of mortar inside C30 concrete provided in this embodiment includes the following steps:

[0140] Four types of fine aggregates were selected: river sand (RS), machine-made sand (MS), unburned coal gangue fine aggregate (UGFA), and self-combusted coal gangue fine aggregate (SGFA). MS, UGFA, and SGFA were prepared by crushing diabase, KUG, and MSG, respectively. The 24-hour saturated surface dry water absorption (W) of each fine aggregate was tested. 24h , stone powder content F fc and flake particle content F s1 and F s2 .

[0141] The DG coarse aggregate concrete mix ratio in Example 1 was used as a benchmark. The coarse aggregate content in the concrete mix ratio was removed to obtain a mortar mix ratio. According to this mortar mix ratio, mortar prism specimens with four types of fine aggregate were prepared. The static elastic modulus and Poisson's ratio of the mortar at 28 days were tested in accordance with the industry standard "Standard for Test Methods for Basic Properties of Building Mortar" (JGJ / T 70-2009).

[0142] S1. Four kinds of fine aggregate are respectively screened into fine aggregate samples of four particle sizes of 2.36mm-4.75mm, 1.18mm-2.36mm, 600μm-1.18mm, and 300μm-600μm. The dried fine aggregate samples of each particle size are then placed in a second circular steel test cylinder with a base. The second test cylinder has a height of 70mm, an inner diameter of 77mm, and a wall thickness of 10mm. The height b of the dried fine aggregate samples of each particle size placed in the second test cylinder is uniformly 50mm. A second pressure head is then placed flatly on the dried fine aggregate samples of each particle size in the second test cylinder to obtain a test cylinder b with a pressure head. The drying temperature is ≤100°C and the time is ≤4h.

[0143] S2. Place the test cylinder b with the pressure head obtained in S1 on a WDW-100E electro-hydraulic servo press, start the press, and uniformly apply a load to the dried fine aggregate samples of each particle size in the second test cylinder through the second pressure head at a speed of 500N / s to a fixed load value b. Unload after loading to a fixed load value b of 25kN. During the loading process, the electro-hydraulic servo pressure testing machine automatically and synchronously collects the fixed load value b data applied to the second pressure head and the second pressure head displacement value b data, which are the axial compressive load values ​​of the dried fine aggregate samples of each particle size in the second test cylinder. F and axial displacement value △ h ;

[0144] S3, using the axial compressive load values ​​of the fine aggregate samples of each particle size after drying in the second test cylinder obtained in S2 F Divide by the internal circular cross-sectional area of ​​the second test cylinder S ( S can be d =77mm), the axial stress value of each particle size fine aggregate sample after drying can be obtained s fa , the calculation formula is shown in formula (9). Three groups of samples of different particle sizes of each fine aggregate are tested repeatedly, and then the average value is taken;

[0145] (9)

[0146] S4, use the axial displacement value △ obtained in S2 h Divide by the height b of the dried fine aggregate sample of each particle size in the second test tube, which is 50 mm, the axial strain value of the dried fine aggregate sample of each particle size can be obtained. e fa , the calculation formula is shown in formula (10). Three groups of samples of different particle sizes of each fine aggregate are tested repeatedly, and then the average value is taken;

[0147] (10)

[0148] S5. Based on the axial stress values ​​of the dried fine aggregate samples of each particle size obtained in S3 and the axial strain values ​​of the dried fine aggregate samples of each particle size obtained in S4, draw the stress-strain curves of the four dried fine aggregate samples of each particle size ( s - e curve), see Figure 15 , it can be seen that the coarse aggregate sample after drying in Example 1 s - e The curve changes in the same trend, the four kinds of dried fine aggregate samples of each particle size in this embodiment s - e The curves all entered the linear section after the initial nonlinear section. However, since the peak loading value of the dried fine aggregate sample is only 1 / 16 of the peak loading value of the dried coarse aggregate sample, the dried fine aggregate sample remained stable until the loading was completed. s - e The curve is still in the linear section;

[0149] Similar to the coarse aggregate after drying in Example 1, the stress and strain of the fine aggregate sample after drying in this example also show an exponential relationship, and the regression function is the same as that of Example 1 (3), where the regression coefficient is a 、 b 、 c and R2 The values ​​are shown in Table 8. R 2 They are all greater than 0.99;

[0150] Table 8 Regression coefficients and R2 of σ-ε curves of four kinds of fine aggregates

[0151]

[0152] Depend on Figure 15 It can be seen that the fine aggregate samples with particle sizes of 300μm~600μm and 2.36mm~4.75mm are s - e The curvature of the curves is relatively large. This is because the content of flake particles in the 2.36mm~4.75mm particle size samples is relatively large. F s1 and F s2 The flaky particles are easy to break and increase the void ratio, which leads to a large proportion of sample structure deformation. The particle shape of the fine aggregate sample with a particle size of 300μm~600μm is close to spherical, which is easy to produce large displacement deformation due to insufficient particle coordination number. s - e The maximum curvature of the curve is consistent. Compared with the 600μm~1.18mm particle size sample, the 1.18mm~2.36mm particle size sample s - e The curve is closer to a straight line, see Figure 16 This is because the content of flake particles in the 1.18mm~2.36mm size sample is F s1 and F s2 As shown in Table 9, the displacement deformation is smaller than that of the 600μm~1.18mm particle size sample. s - e The curve is closest to a straight line. In summary, the calculation of the average elastic modulus of the 1.18mm~2.36mm particle size sample can best reflect the elastic deformation performance of the fine aggregate under the confined compression state. Therefore, this embodiment selects the 1.18mm~2.36mm particle size dry samples of each fine aggregate s - e Average elastic modulus of fine aggregate (Average elastic modulus of fine aggregate, referred to as E fa ). s - e The linear interval close to the straight line on the curve is taken as the stress value To the end point of the curve, the calculation formula is shown in formula (11). The fine aggregate calculated according to formula (11) Efa See Table 9 for values.

[0153] Table 9 Technical indicators of four types of fine aggregates

[0154]

[0155] (11)

[0156] Where: is the average elastic modulus of the fine aggregate sample after drying, MPa; ; for s - e Stress value at the end point of the curve, MPa; for s - e Stress value on the curve Strain value at for s - e The strain value at the end point of the curve;

[0157] Based on fractal theory, the average elastic modulus of the dried fine aggregate sample at the mortar layer inside the concrete is E fa It should also be compared with the elastic modulus of the mortar E m Linear correlation. Average elastic modulus of the four dried fine aggregate samples E fa Compared with the measured elastic modulus of the internal mortar of C30 strength grade concrete E m The regression equation and the confidence interval and prediction interval of 95% confidence level are as follows Figure 17 As shown, R 2 =0.83, there is a linear correlation between the two, and the residuals also obey the normal distribution.

[0158] Take 4 kinds of fine aggregate saturated surface dry samples and load them again, and measure the average elastic modulus of saturated surface dry fine aggregate. E fa-w As shown in Table 9, four types of fine aggregates can be seen. E fa-w compared to E fa There was a slight decrease,

[0159] average value , among which the fine aggregate SGFA has the highest water absorption rate It can be seen that, unlike the coarse aggregate in Example 1, the fine aggregate with high water absorption E fa-w There has been no significant decrease.E fa-w and E m After regression analysis again, R 2 =0.836, which is consistent with the E fa of R 2 =0.83, which is not much different. Therefore, for C30 strength grade concrete, the internal mortar elastic modulus can be calculated using the semi-empirical formula shown in formula (12): E m .

[0160] (12)

[0161] E fa Poisson's ratio of mortar m m There is a good linear correlation between the regression equation and the confidence interval and prediction interval of 95% confidence level. Figure 18 As shown, R 2 =0.94, and the residual follows a normal distribution. For C30 strength grade concrete, the Poisson's ratio of its internal mortar can be calculated using the semi-empirical formula shown in formula (13): m m .

[0162] (13)

[0163] Example 3

[0164] The rapid detection method for deformation performance of C30 concrete provided in this embodiment includes the following steps:

[0165] After replacing river sand, machine-made sand made from natural rocks and solid waste has been increasingly used in the preparation of structural concrete. E ca and E fa To test the feasibility of the elastic modulus of C30 strength grade concrete mixed with manufactured sand, the three coarse aggregates DG, AG, and MSG in Example 1 were combined with the four fine aggregates RS, MS, SGFA, and UGFA in Example 2 to mix C30 strength grade concrete. Then, according to the national standard "Standard for Test Methods for Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), the 28d concrete cube compressive strength and static elastic modulus were tested.

[0166] The measured results were drawn using the 3D Smoother function of Origin2021 software. Eca 、 E fa and E c 3D surface fitting diagram of Figure 19 , it can be seen that the curvature of the fitting surface is small and close to the plane. E ca and E fa and E c Linear correlation. The three-dimensional plane fitting diagram obtained by regression can be found in Figure 20 95% confidence intervals can be found in Figure 21 The regression equation is shown in formula (14). R 2 =0.96, indicating E ca and E fa and E c Good linear correlation. The diagnostic results of the binary regression model showed that the VIF values ​​were all 1.000. E ca and E fa There is no multicollinearity, the residuals obey the normal distribution, and the model is accurate and reliable.

[0167] For C30 strength grade concrete, the elastic modulus of concrete can be calculated using the semi-empirical formula shown in formula (14): E c , where the parameter α Same as formula (7).

[0168] (14)

[0169] Since Equation (14) is a semi-empirical formula based on the measured data of this embodiment, in order to verify its reliability, the measured data of the elastic modulus of C30 strength grade concrete prepared with LG, MSG, ISG, KUG, and RCA coarse aggregates and RS and SGFA fine aggregates from the published literature were selected to test Equation 14. The comparison results of the calculated values ​​of Equation (14) and the measured values ​​in the literature are shown in Figure 22 , it can be seen that the relative errors of the calculated values ​​do not exceed ±10%. R 2 =0.90, MSE =1.38. This indicates that the semi-empirical formulas for the elastic modulus of C30 strength grade concrete, established based on the average elastic moduli of coarse and fine aggregates, respectively, have good universality and prediction accuracy for concretes of various coarse and fine aggregate types. The formula (14) proposed in this example has wide applicability to coarse and fine aggregate types and good practical applicability.

[0170] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A rapid detection method for deformation performance of C30 concrete and internal mortar, characterized in that: The method comprises the following steps: S1. First, test the 24-hour saturated surface dry water absorption of coarse aggregate used for mixing C30 strength grade concrete, sieve the coarse aggregate to obtain a coarse aggregate sample, dry the coarse aggregate sample, and place the dried coarse aggregate sample into a first test cylinder to a fixed height a. Then, place a first pressure head on the dried coarse aggregate sample in the first test cylinder to obtain a test cylinder with a pressure head a. Screening fine aggregate used for mixing C30 strength grade concrete to obtain a fine aggregate sample, drying the fine aggregate sample, placing the dried fine aggregate sample into a second test cylinder to a fixed height b, and then placing a second pressure head on the dried fine aggregate sample in the second test cylinder to obtain a test cylinder with a pressure head b; S2. Place the test cylinder a with the pressure head obtained in S1 on a press, start the press, and uniformly apply a load to a fixed load value a to the dried coarse aggregate sample in the first test cylinder through the first pressure head. Simultaneously, collect the fixed load value a and the displacement value a of the first pressure head during the entire process. The test cylinder b with the pressure head obtained in S1 is placed on a press, the press is started, and a load is uniformly applied to the dried fine aggregate sample in the second test cylinder through the second pressure head to a fixed load value b, while the fixed load value b of the applied load and the displacement value b of the second pressure head are synchronously collected throughout the entire process; S3. Dividing the fixed load value a obtained in S2 by the cross-sectional area of ​​the first test cylinder to obtain a stress value of the dried coarse aggregate sample; Dividing the fixed load value b obtained in S2 by the cross-sectional area of ​​the second test cylinder to obtain the stress value of the dried fine aggregate sample; S4, dividing the displacement value a obtained in S2 by the fixed height value a in S1 to obtain the strain value of the dried coarse aggregate sample; The displacement value b obtained in S2 is divided by the fixed height value b in S1 to obtain the strain value of the dried fine aggregate sample; S5. Draw a stress-strain curve of the dried coarse aggregate sample according to the stress value of the dried coarse aggregate sample obtained in S3 and the strain value of the dried coarse aggregate sample obtained in S4; Drawing a stress-strain curve of the dried fine aggregate sample according to the stress value of the dried fine aggregate sample obtained in S3 and the strain value of the dried fine aggregate sample obtained in S4; S6. Calculate the slope value E of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying obtained in S5. ca ; Calculate the slope value E of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample obtained in S5 fa ; S7. The slope value E of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying obtained in S6 ca and the slope value E of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample fa , the calculation formula for the elastic modulus of C30 strength grade concrete is: E c =200·a·E ca +134E fa +5284 Where: E c —Elastic modulus value of C30 strength grade concrete; α—moisture coefficient; when the 24h saturated surface dry water absorption rate of the coarse aggregate described in S1 is ≤3%, α=1.0; when the 24h saturated surface dry water absorption rate of the coarse aggregate described in S1 is >3%, α=0.92; E ca —The slope of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying; E fa —The slope of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample; The calculation formula for the internal mortar elastic modulus value of C30 strength grade concrete is: E m =188E fa +7463 Where: E m —Internal mortar elastic modulus value of C30 strength grade concrete; E fa —The slope of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample; The calculation formula for the internal mortar Poisson's ratio of C30 strength grade concrete is: m m =0.00139E fa +0.15053 Where: μ m —Poisson’s ratio of internal mortar for C30 strength grade concrete; E fa —The slope of the approximate straight line segment on the stress-strain curve of the dried fine aggregate sample; When the fine aggregate in S1 is river sand, the calculation formula for the elastic modulus of C30 strength grade concrete is: AND c =218·α·E ca +13266 Where: E c —When the fine aggregate is river sand, the elastic modulus value of C30 strength grade concrete; α—moisture coefficient; when the 24h saturated surface dry water absorption rate of the coarse aggregate described in S1 is ≤3%, α=1.0; when the 24h saturated surface dry water absorption rate of the coarse aggregate described in S1 is >3%, α=0.92; E ca —The slope of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying; When the fine aggregate in S1 is river sand, the calculation formula for the internal mortar Poisson's ratio of C30 strength grade concrete is: m c =0.0018E ca +0.1073 Where: μ c — When the fine aggregate is river sand, the internal mortar Poisson’s ratio of C30 strength grade concrete; E ca —The slope value of the approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying.

2. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 1, characterized in that: The particle size of the coarse aggregate in S1 is ≥4.75 mm, and the particle size of the coarse aggregate sample is 9.5 mm to 13.2 mm.

3. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 2, characterized in that: In S1, the height of the first test cylinder is 128 mm, and the inner diameter is 150 mm; the fixed height value a is 100 mm.

4. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 3, characterized in that: The load is uniformly applied to a fixed load value a of 400 kN as described in S2.

5. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 1, characterized in that: The particle size of the fine aggregate in S1 is less than 4.75 mm, and the particle size of the fine aggregate sample is in four particle size ranges of 300 μm to 600 μm, 600 μm to 1.18 mm, 1.18 mm to 2.36 mm, and 2.36 mm to 4.75 mm.

6. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 5, characterized in that: In S1 , the height of the second test cylinder is 70 mm, the inner diameter is 77 mm, and the fixed height value b is 50 mm.

7. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 6, characterized in that: The load is uniformly applied as described in S2 to a fixed load value b of 25 kN.

8. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 1, characterized in that: The first test cylinder and the second test cylinder are both round test cylinders made of steel.

9. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 1, characterized in that: The drying process in S1 is performed at a temperature of ≤100° C. and for a time of ≤4 h.

10. A rapid detection method for deformation performance of C30 concrete and internal mortar according to claim 1, characterized in that: The approximate straight line segment on the stress-strain curve of the coarse aggregate sample after drying described in S6 is the strain value of 50000×10 -6 Up to 150,000 × 10 -6 The stress-strain curve between the dried fine aggregate sample stress-strain curve is approximately a straight line segment from the stress value of 0.5MPa to the end point of the curve stress-strain curve.

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