GB/T 38948-2020 English PDF (GBT38948-2020)

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GB/T 38948-2020: Evaluation method for the cracking resistance of asphalt mixture at low temperature
GB/T 38948-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 93.080.20
Q 20
Evaluation method for the cracking resistance of
asphalt mixture at low temperature
ISSUED ON: JUNE 02, 2020
IMPLEMENTED ON: APRIL 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Test equipment ... 5
5 Preparation ... 5
6 Test procedure ... 7
7 Calculation ... 7
8 Test report ... 9
Appendix A (Informative) Test report on the cracking resistance of asphalt
mixture at low temperature ... 11
Evaluation method for the cracking resistance of
asphalt mixture at low temperature
1 Scope
This Standard specifies test equipment, preparation, test procedures,
calculation, and test report for the evaluation of the cracking resistance of
asphalt mixture at low temperature.
This Standard applies to all kinds of hot-mixed, warm-mixed and cold-mixed
asphalt mixtures whose nominal maximum particle size is no more than 26.5
mm.
2 Normative references
The following documents are indispensable for the application of this document.
For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
document.
JTG E20, Standard Test Methods of Bitumen and Bituminous Mixtures for
Highway Engineering
3 Terms and definitions
The following terms and definitions are applicable to this document.
3.1 Bend strain energy of asphalt mixture
The energy that is stored in the asphalt mixture when the asphalt mixture
reaches the critical state of crack formation during the bending test destruction
process.
Note: in kilojoules (kJ).
3.2 Bend strain energy density of asphalt mixture
The energy that is stored in the unit volume of asphalt mixture when the asphalt
mixture reaches the critical state of crack formation during the bending test
destruction process.
Note: in kilojoules per cubic meter (kJ/m3).
5.2 Form the test piece according to the method that is specified in T0703 of
JTG E20; after placing the ordinary asphalt mixture test piece for 24 h and the
modified asphalt mixture test piece for 48 h at room temperature, cut the test
piece according to T0715 in JTG E20; the dimensions of test pieces shall meet
the requirements of Table 2; dry naturally at room temperature; mark the height
direction of test pieces.
Table 2 -- Dimensions of test pieces for the bending test at low
temperature
5.3 Use a vernier caliper to measure the dimensions of each test piece in the
mid-span of the rectangular parallelepiped and the two fulcrum sections. When
the difference between the height (width) of the three sections of a single test
piece exceeds 2 mm, the test piece shall be invalid. The mid-span section width
is b; the height is h. Take the average of 3 sections, to the nearest 0.1 mm.
5.4 On the basis of the mixture type, determine the density, voidage and other
indicators of the test piece according to the method that is specified in
T0705/0706 of JTG E20. When the difference between the measured voidage
and the designed voidage exceeds 0.5%, the test piece shall be invalid.
5.5 The number of rectangular parallelepiped test pieces in each group should
not be less than 6; the number of effective test pieces shall not be less than 4.
5.6 The constant temperature time of the test piece shall not be less than 4 h
from the time when the thermal insulation environmental box reaches the test
temperature; the distance between the test pieces in the thermal insulation box
shall not be less than 20 mm.
5.7 Place the beam-type test piece support of the testing machine; the distance
between the fulcrums shall be 200 mm ± 0.5 mm; keep the upper indenter and
the lower support parallel, and the two sides equidistant, as shown in Figure 1;
then, fix its position.