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GB/T 50081-2019 English PDF (GBT50081-2019)

GB/T 50081-2019 English PDF (GBT50081-2019)

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GB/T 50081-2019: Standard for test methods of concrete physical and mechanical properties

In order to standardize and unify the test methods of concrete physical and mechanical properties, to improve the level of concrete test technology, this standard is hereby formulated. This standard is applicable to the test of physical and mechanical properties of concrete in construction projects. This standard does not apply to fully graded concrete and roller-compacted concrete in water conservancy and hydropower projects.
GB/T 50081-2019
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
UDC
P GB/T 50081-2019
Standard for test methods of concrete physical and
mechanical properties
ISSUED ON: JUNE 19, 2019
IMPLEMENTED ON: DECEMBER 01, 2019
Issued by: Ministry of Housing and Urban-Rural Development of the PRC;
State Administration for Market Regulation.
Table of Contents
Foreword ... 6
1 General ... 9
2 Terms and symbols ... 9
2.1 Terms ... 9
2.2 Symbols ... 11
3 Basic requirements ... 12
3.1 General requirements... 12
3.2 Section size of specimen... 12
3.3 Dimensional measurement and tolerance of specimen ... 13
3.4 Test report ... 14
4 Preparation and curing of specimen ... 15
4.1 Instrument equipment... 15
4.2 Sampling and preparation of specimen ... 16
4.3 Preparation of specimen ... 16
4.4 Curing of specimen ... 19
5 Test of compressive strength ... 20
6 Test of axial compressive strength ... 23
7 Test of elastic modulus under static compressive stress ... 25
8 Test of Poisson's ratio ... 29
9 Test of splitting tensile strength ... 33
10 Test of flexural tensile strength ... 36
11 Test of axial tensile ... 39
12 Test of the bond strength between concrete and steel bars ... 45
13 Test of concrete bond strength ... 49
14 Test of abrasion resistance ... 51
14.1 Test of abrasion loss ... 51
14.2 Test of grinding pit length ... 54
15 Test of thermal diffusivity ... 58
16 Test of thermal conductivity ... 62
17 Test of specific heat capacity ... 66
18 Test of linear expansion coefficient ... 69
19 Test of density of hardened concrete ... 72
20 Test of water absorption ... 77
Appendix A Style sheet of test report ... 81
Appendix B Preparation and curing of cylinder specimen ... 90
Appendix C Test of compressive strength of cylinder specimen ... 93
Appendix D Elastic modulus under static compressive stress test of cylinder specimen ... 95
Appendix E Splitting tensile strength test of cylinder specimen ... 99 Appendix F Table of relation between ??/??0 value and ??t/D2 value ... 102 Explanation of wording in this standard ... 108
List of quoted standards ... 109
Standard for test methods of concrete physical and
mechanical properties
1 General
1.0.1 In order to standardize and unify the test methods of concrete physical and mechanical properties, to improve the level of concrete test technology, this standard is hereby formulated.
1.0.2 This standard is applicable to the test of physical and mechanical properties of concrete in construction projects. This standard does not apply to fully graded concrete and roller-compacted concrete in water conservancy and hydropower projects.
1.0.3 In addition to the provisions of this standard, the test methods of concrete physical and mechanical properties shall also comply with the provisions of the current relevant national standards.
2 Terms and symbols
2.1 Terms
2.1.1 Concrete
The engineering materials, which are produced through such processes as blending, forming, curing, AND have strength after hardening, through the use of cement, aggregate, water as the main raw materials, by adding mineral admixtures and additives as required, according to a certain ratio.
2.1.2 Compressive strength
The maximum pressure, that the cube specimen can withstand per unit area. 2.1.3 Axial compressive strength
The maximum pressure, that the prism specimen can withstand per unit area, in the axial direction.
2.1.4 Elastic modulus under static compressive stress
The stress required for producing unit deformation, when a prism specimen or 0.25 kg ~ 0.50 kg.
4.1.5 For dry hard concrete, a forming cover mold, weight steel plate, weight block or other pressure device shall be provided. The inner contour size of the cover mold shall be the same as the inner contour size of the specimen mold; the height should be 50 mm; it is not easy to deform AND can be fixed on the specimen mold. The side length or diameter of the weight steel plate shall be smaller than the inner contour size of the specimen mold. The difference between the two should be 5 mm.
4.2 Sampling and preparation of specimen
4.2.1 For the concrete sampling and specimen preparation, it shall comply with the relevant provisions of the current national standard "Standard for test method of performance on ordinary fresh concrete" GB/T 50080.
4.2.2 The mixture used for each set of specimens shall be sampled from the same pan of concrete OR the same truck of concrete.
4.2.3 The concrete sampled or mixed in the laboratory shall be formed as soon as possible.
4.2.4 When preparing concrete specimens, it shall take labor protection measures.
4.3 Preparation of specimen
4.3.1 Before the specimen is formed, the size of the specimen mold shall be checked, which shall comply with the relevant provisions in article 4.1.1 of this standard. The specimen mold shall be wiped clean; a thin layer of mineral oil OR release agent, which does not react with concrete, shall be evenly painted on the inner wall. The release agent on the inner wall of the specimen mold shall be evenly distributed; there shall be no obvious deposits.
4.3.2 The homogeneity of the concrete mixture shall be ensured, before it is pouring into mold.
4.3.3 It should determine the appropriate forming method, according to the consistency of the concrete mixture or the purpose of the test. The concrete shall be sufficiently dense, to avoid delamination and segregation.
1 The preparation of specimens, through vibrating, by a vibrating table shall be carried out as follows:
1) Load the concrete mixture into the specimen mold at one time. When
be 20 s. The vibrating rod shall be pulled out slowly; no holes shall be left after pulling out.
4 For self-compacting concrete, the concrete mixture shall be loaded into the specimen mold in two times. The thickness of each layer should be the
same. The interval between two loadings is 10 s. The concrete shall be
higher than the opening of specimen mold. It shall not be formed through the vibrating table, manual inserting and tamping, or vibrating rod method. 5 For dry hard concrete, the specimen can be formed according to the
following method:
1) After the concrete is mixed, it shall be poured on a non-absorbent
bottom plate. Use the quartering method to take sample AND load it
into the specimen mold of cast iron or cast steel.
2) Use the quartering method to load the uniformly mixed dry hard
concrete material into the specimen mold, to about half the height of
the specimen mold. Use the tamping rod to perform even inserting and
tamping. After compacting it, before continuing to load, it shall add a sleeve to the specimen mold. The second loading shall be slightly
higher than the top surface of the specimen mold. Then perform even
inserting and tamping. The top surface of the concrete shall be slightly higher than the top surface of the specimen mold.
3) Inserting and tamping shall be carried out evenly, from the edge to the center, along the spiral direction. When inserting and tamping the bottom layer of concrete, the vibrating rod shall reach the bottom of the
specimen mold. When inserting and tamping the upper layer, the tamping
rod shall penetrate the upper layer AND then inserting 10 mm ~ 20 mm
into the lower layer. When inserting and tamping, the tamping rod shall be vertical and not inclined. After inserting and tamping of each layer, it shall use the spatula to insert the mixture along the inner wall of specimen
mold.
4) The number of inserting and tamping of each layer shall be no less than 12, within a cross-sectional area of 10000 mm2;
5) After loading, inserting and tamping, attach or fix the specimen mold on the vibration table. Place a weight steel plate and weight block OR other pressure device. It shall, according to the consistency of the concrete mixture, adjust the mass of the weight block OR the pressure which is
applied by the pressurizing device. Start to vibrate. The vibrating time should not be less than the Viber consistency of the concrete, AND until the surface produces slurry.
L - Measurement gauge length (mm);
??n - The average value of the deformation, on both sides of the specimen, when the load is applied from F0 to Fa the last time (mm);
??a - The average value of deformation, on both sides of the specimen, at Fa (mm);
??0 - The average value of the deformation, on both sides of the specimen, at F0 (mm).
2 It shall use the arithmetic average of the measured values of the 3
specimens, as the elastic modulus value of the group of specimens, which shall be accurate to 100 MPa. After measuring the elastic modulus, when there is a specimen, whose axial compressive strength value differs from the axial compressive strength value, which is used to determine the test control load, by more than 20% of the latter, THEN, the elastic modulus value shall be calculated based on the arithmetic average of the measured values of two specimens. After measuring the elastic modulus, when there are two specimens, whose axial compressive strength values differ from
the axial compressive strength value, which is used to determine the test control load, by more than 20% of the latter, THEN, the test is invalid. 8 Test of Poisson's ratio
8.0.1 For the specimens, which are used for the test of Poisson's ratio of concrete, the size and quantity shall meet the following requirements:
1 The specimen shall be a prism specimen, which has a side length of 150 mm x 150 mm x 300 mm;
2 For each test, it shall prepare 6 specimens, of which 3 specimens are used to determine the axial compressive strength, whilst the other 3 are used to determine the Poisson's ratio.
8.0.2 The test instrument and equipment shall meet the following requirements: 1 The pressure testing machine shall comply with the provisions of item 1 in article 5.0.3 of this standard.
2 The instrument used for micro-deformation measurement shall meet the
following requirements:
1) The vertical micro-deformation measuring instrument of the specimen
may be a dial gauge, resistance strain gauge, laser length gauge,
extensometer or displacement sensor, etc. The instrument used for
When the resistance strain gauge is used to measure the vertical
deformation, the vertical measurement gauge distance shall be 150 mm.
For the resistance strain gauge that measures the lateral deformation, the measurement gauge distance shall be 100 mm. After the specimen is
taken out of the curing room, it shall process the surface defects of the specimen, in the area where the strain gauge is attached. It may use hair dryer to blow dry the surface of the specimen. Meanwhile, at the middle of both sides of the specimen, use the 502 glue to paste the strain gauge. 4 Before the specimen is placed in the testing machine, it shall wipe clean the surface of the specimen AND the upper and lower pressure plates.
5 Place the specimen upright, on the lower pressure plate or steel backing plate of the testing machine. The axis of the specimen shall be aligned with the center of the lower pressure plate.
6 Turn on the testing machine. The surface of the specimen shall be in
uniform contact with the upper and lower pressure plates OR steel backing plates.
7 It shall be loaded to the initial load value F0, which has a reference stress of 0.5 MPa. Keep the constant load for 60 s. In the subsequent 30 s, record the deformation reading ??0 and ??t0 of each measuring point. The load shall be applied continuously and uniformly, until reaching the load value Fa, which has a stress of 1/3 of the axial compressive strength fcp. Keep the constant load for 60 s. In the subsequent 30 s, record the deformation
reading ??a and ??ta of each measuring point. The loading speed used shall comply with the provisions of item 5 in article 6.0.4 of this standard. 8 When the ratio of the difference between the longitudinal or lateral
deformation values, on the left and right sides, TO their average value, is greater than 20%, the specimen shall be re-aligned and the steps of item 7 of this article shall be repeated. When it cannot be reduced to less than 20%, this test is invalid.
9 After confirming that the alignment of the specimen meets the requirements of item 8 of this article, at the same speed as the loading speed, unload to the reference stress 0.5 MPa (F0); keep the constant load for 60 s. It shall, at the same loading and unloading speed, as well as keeping the
constant load (F0 and Fa) for 60 s, carry out repeated preloading, for at least two times. After the last preloading is completed, the load shall be held at the reference stress of 0.5 MPa (F0) for 60 s; in the subsequent 30 s, record the deformation reading ??0 and ??t0 of each measuring point. Then, at the same loading speed, apply load, until reaching to Fa; hold this load for 60 s; in the subsequent 30 s, record the deformation reading ??a and ??ta of each measuring point (Figure 8.0.3).
shall be accurate to 0.01 MPa;
F - The failure load of the specimen (N);
A - The area of the splitting plane of the specimen (mm2).
2 The determination of the splitting tensile strength of concrete shall meet the following requirements:
1) It shall use the arithmetic average of the measured values of 3
specimens, as the split tensile strength value of the group of specimens, which shall be accurate to 0.01 MPa;
2) When the difference BETWEEN the maximum or minimum of the three
measured values AND the median value, exceeds 15% of the median
value, the maximum and minimum values shall be discarded together;
THEN, take the median value as the splitting tensile strength value of
this group of specimens;
3) When the difference BETWEEN the maximum value and the minimum
value AND the median value, exceeds 15% of the median value, the
test results of this group of specimens are invalid.
3 For the splitting tensile strength value, which is obtained by the use of a 100 mm ?? 100 mm ?? 100 mm non-standard specimen, it shall be multiplied
by a size conversion factor 0.85. When the concrete strength grade is not less than C60, it shall use standard specimen.
10 Test of flexural tensile strength
10.0.1 This method is suitable for determining the flexural tensile strength of concrete, also known as bending tensile strength.
10.0.2 For the specimens, which are used in the test for determining the concrete's flexural tensile strength, the size, quantity and surface quality shall meet the following requirements:
1 The standard specimen shall be a prism specimen, which has a side length of 150 mm ?? 150 mm ?? 600 mm or 150 mm ?? 150 mm ?? 550 mm;
2 Prism specimens, which have a side length of 100 mm ?? 100 mm ?? 400
mm, are non-standard specimens;
3 On the inner surface of the middle 1/3 section, in the long direction, of the specimen, there shall be no holes, which have a diameter of more than 5 mm and a depth of more than 2 mm;
which shall be accurate to 0.1 MPa;
2) When the difference BETWEEN the maximum or minimum of the three
measured values AND the median value, exceeds 15% of the median
value, the maximum and minimum values shall be discarded together;
then, take the median value as the flexural tensile strength of this group of specimens;
3) When the difference BETWEEN the maximum value and the minimum
value AND the median value, exceeds 15% of the median value, the
test results of this group of specimens are invalid.
3 When one of the 3 specimens has a fracture surface, which is outside the two concentrated loads, the flexural tensile strength of concrete shall be calculated, based on the test results of the other two specimens. When
the difference between these two measured values, is not more than 15%
of the smaller value of these two measured values, THEN, for the flexural tensile strength value of the group of specimens, it shall be calculated, based on the average of these two measured values; otherwise, the test
results of this group of specimens are invalid. When the fracture position of the lower edge of two specimens is outside the two action lines of
concentrated load, the tests of this group of specimens are invalid.
4 When the specimen is 100 mm ?? 100 mm ?? 400 mm non-standard
specimen, it shall be multiplied by the size conversion factor 0.85. When the concrete strength grade is not less than C60, it should use standard specimen. When the non-standard specimen is used, the size conversion
factor shall be determined by test.
11 Test of axial tensile
11.0.1 This method is suitable for determining the axial tensile strength, ultimate tensile value, tensile elastic modulus of concrete.
11.0.2 The size of the middle cross-section of the axially stretched specimen, which is formed indoors, shall be 100 mm ?? 100 mm (Figure 11.0.2a, Figure 11.0.2b, Figure 11.0.2c). The core-drilled specimen shall use a cylinder, which has a diameter of 100 mm (Figure 11.0.2d). Each group of specimens shall include 4 pieces.
11.0.3 The performance of the test equipment shall meet the following
requirements.
1 Tensile testing machine:
1) The failure load of the specimen should be greater than 20% of the full range of the tensile testing machine AND should be less than 80% of
the full range of the tensile testing machine;
2) The relative error of the indication shall be ??1%;
3) It shall have a loading speed indicating device or a loading speed
control device; it shall be able to load uniformly and continuously;
4) Other requirements shall comply with the relevant requirements of the current national standard "Hydraulic universal testing machines" GB/T
3159 and "General requirements for testing machines" GB/T 2611.
12.0.3 The test of bond strength between concrete and steel bars shall be carried out according to the following steps:
1 For the ribbed steel bar HRB400 used for the test, the performance shall meet the requirements of the current national standard "Steel for the
reinforcement of concrete - Part 2: Hot rolled ribbed bars" GB/T 1499.2; its nominal diameter is 20 mm. The steel bars shall have enough length, for the universal machine to hold and install the gauge. The length should be 500 mm. The size and shape of the steel bars used in the test shall be the same. Before forming, the steel bars shall be cleaned by a steel wire brush; wiped by acetone or ethanol. There shall be no rust and oil stains. The top surface of the free end of the steel bar shall be smooth and flat; it shall be consistent with the reserved holes of the specimen mold. It may also use HPB300 hot-rolled plain bars, which has a nominal diameter of
20 mm, in accordance with the current national standard "Steel for the
reinforcement of concrete - Part 1: Hot rolled plain bars" GB/T 1499.1, OR other steel bars actually used in the project. The requirements and the treatment method are the same as the ribbed steel bar.
2 The specimens shall be prepared according to the relevant requirements in article 4.3 of this standard. It shall use 6 specimens as a group. The maximum particle size of concrete aggregate shall not exceed 31.5 mm.
When installing the steel bar, the free end of the steel bar is embedded in the mold wall. For the hole on the mold wall, through which the steel bar pa...

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