GB/T 7897-2026Test methods for the properties of mortar for ferrocement (English PDF)

5.1 Specimen Molding

5.1.1 When preparing mortar samples in the laboratory, the materials used should be allowed to stand for at least 24 hours under the test conditions in 4.1.

5.1.2 When mixing mortar in the laboratory, the material quantities should be measured by mass, with the weighing accuracy of cement, water, and admixtures being ±0.5%; the weighing accuracy of sand should also be ±0.5%. It is ±1%.

5.1.3 Mechanical mixing should be used when mixing mortar in the laboratory. The mixer should conform to the requirements of JG/T 3033, and the mixing volume per batch should be the capacity of the mixer. The mortar should be mixed evenly, with a mixing time of 30% to 70%, and the mixing time should be 120 to 180 seconds.

5.1.4 All specimens were prepared immediately after sampling and completed within 30 minutes.

5.1.5 When molding the specimen, use a mold conforming to JC/T 726 and apply a release agent conforming to JC/T 949 to its inner wall.

5.1.6 Fill the mold with the mixed mortar all at once. The molding method depends on the consistency. The mortar consistency test method shall conform to JGJ/T 70. The regulations stipulate that mortar with a consistency of 30mm~70mm should be compacted using a vibrating table for 30s~45s. The vibrating table should conform to the requirements of JC/T 682 or higher. In accordance with JC/T 723, mortar with a consistency greater than 70 mm and less than 120 mm should be manually compacted using a tamping rod. During manual compaction, use a tamping rod with a diameter of... The 16mm steel rod was inserted and tamped in two layers, with each layer being tamped 12 times.

5.2 Specimen Curing

5.2.1 Standard curing shall be used when determining the strength grade. After molding, specimens cured under standard curing conditions shall be covered with plastic film and cured in a curing chamber or... Cured in the curing room for 24 hours, then demolded and cured in water until the strength test.

5.2.2 The curing requirements for specimens shall be in accordance with the provisions of GB/T 17671.The specimens shall be cured for 28 days (starting from the time of molding) before testing.

6.2 Instruments and Equipment

6.2.1 The flexural strength testing machine shall conform to the requirements of JC/T 724.

6.2.2 The graduation value or resolution of the caliper shall not exceed

0.1 mm, in accordance with the provisions of GB/T 21389.

6.3 Test Procedure

6.3.1 Measure the lengths of four sides of the same cross-section at the middle of the specimen once with calipers, and take the arithmetic mean of the four measurements. This is the side length of the specimen. (b) The result was rounded to

0.1 mm.

6.3.2 Place one side of the specimen on the support cylinder of the flexural testing machine, with the major axis of the specimen perpendicular to the support cylinder. The specimen is then subjected to a loading cylinder... A uniform load of 50 N/s ± 10 N/s is applied vertically to opposite sides of the specimen until it breaks. The failure load and the breaking point are recorded. Bad location. Keep both halves of the specimen moist until the compression test.

6.4 Result Calculation and Value Interpretation

6.4.1 The flexural strength of a single specimen is calculated according to formula (1), and the result is rounded to

0.1 MPa.

6.4.2 The flexural strength test results of mortar shall be the arithmetic mean of the measured values of 3 specimens in each group. If one of the 3 measured values is... If the value exceeds ±10% of the average, discard it and then take the average again as the result of the flexural strength test. If two out of the three measured values exceed the mean, the test result is considered negative. If the interval is 10%, the flexural strength test results for that group are invalid.

7.2 Instruments and Equipment

7.2.1 The compression testing machine conforms to the requirements of JC/T 960.

7.2.2 The fixtures for the compressive strength testing machine shall conform to the requirements of JC/T 683.

7.3 Test Procedure

7.3.1 The specimens after the flexural test should be subjected to a compressive test immediately. The compressive test is conducted using a compressive jig, and the test is performed based on the specimen's initial condition during molding. The side is used as the pressure surface, and the fixture is aligned with the center of the testing machine's pressure plate and on the same axis as the press. Before loading, the pressure surface of the specimen is cleaned. Sand or debris between the pressure plates.

7.3.2 The entire loading process should be carried out continuously and uniformly at a rate of 2400 N/s ±.200 N/s until the specimen fails. The maximum load at failure should be recorded. Load.

7.4 Result Calculation and Value Interpretation

7.4.1 The compressive strength of a single specimen is calculated according to formula (2), and the result is rounded to

0.1 MPa.

7.4.2 The test results for mortar compressive strength are taken as the arithmetic mean of the measurements from three specimens in each group. If one of the three measurements is... If the value exceeds ±10% of the average, discard it and take the average of the remaining two measurements as the compressive strength test result. If any of the three measurements exceed ±10%, discard it and take the average of the remaining two measurements as the compressive strength test result. If two values exceed the median value by 10%, the results of the compressive strength test for that group are invalid.

8.2 Instruments and Equipment

8.2.1 The specifications for the testing machine are the same as those in 7.2.1.

8.2.2 Use steel wire with a diameter of (4±0.1) mm as the pad, and the length of the pad is greater than 40 mm.

8.3 Test Procedure

8.3.1 Perform the splitting tensile test as soon as possible after the flexural test. During the splitting tensile test, the spacer strip should be perpendicular to the top surface of the specimen during molding. A padding layer should be placed between the upper and lower padding strips and the contact surface of the specimen. Both the padding strips and the padding layers should be placed in the center of the bearing surface of the specimen, as shown in Figure 1.

8.3.2 After starting the testing machine, when the upper pressure plate of the testing machine approaches the pad, adjust the ball seat to ensure even contact, and then apply the load continuously and evenly. The pressure is evenly transmitted to the specimen through the pads and padding layers. The loading rate is (500±50) N/s, and the loading is continuously and evenly applied until the specimen fails. Record the destructive load.

8.4 Result Calculation and Value Interpretation

8.4.1 The splitting tensile strength of a single specimen is calculated according to formula (3), and the result is rounded to

0.01 MPa.

8.4.2 The results of the mortar splitting tensile strength test shall be the arithmetic mean of the measurements of three specimens in each group. When any of the three measurements are... If one value exceeds the median value by ±10%, the median value is taken as the result of the splitting tensile strength test. If two out of the three measured values exceed the median value... If the value is 10%, the splitting tensile strength test results for that group are invalid.

9.2 Instruments and Equipment

9.2.1 The specifications for the testing machine are the same as those in 7.2.

9.2.2 The specifications for vernier calipers are the same as those in 6.2.2.

9.3 Test Procedure

9.3.1 Measure the side lengths of the upper and lower end faces of the specimen four times each using calipers, and take the arithmetic mean of the eight measurements as the side length. The result is then corrected. Approximately

0.1 mm.

9.3.2 Place the specimen vertically on the testing machine, aligning the center of the specimen with the centers of the upper and lower pressure plates. Start the testing machine. When the upper pressure plate is close to the specimen, adjust... The ball seat is adjusted to ensure even contact between the specimen and the upper pressure plate, and then a continuous and uniform load is applied at a rate of (1000±50) N/s. Pressure is manually controlled. When the specimen approaches failure and begins to deform rapidly during the loading rate, stop adjusting the testing machine throttle until the specimen fails, and then record the failure rate. Load.

9.4 Calculation and Value Interpretation of Results

9.4.1 The axial compressive strength of mortar for a single specimen is calculated according to formula (4), and the result is rounded to

0.1 MPa.

9.4.2 The axial compressive strength test results of mortar shall be taken as the arithmetic mean of the three measurements in each group. If one of the three measurements is... If the value exceeds the median value by 10%, the median value is taken as the result of the flexural strength test. If two out of the three measured values exceed the median value by 10%, then the result is considered... The results of the axial compressive strength test are invalid.

10.2 Instruments and Equipment

10.2.1 The specifications for the testing machine are the same as those in 7.2.

10.2.2 The static resistance strain gauge shall have an accuracy of 1 µepsilon, and the longitudinal resistance gauge length shall be no less than 20 mm and no more than half the height of the specimen.

10.3 Test Procedure

10.3.1 Specimen Dimension Measurement Proceed as specified in 9.3.1.

10.3.2 Determination of Elastic Modulus

10.3.2.1 Take 3 specimens and determine the axial compressive strength (fcp) of the mortar according to the provisions of 9.3.The load value corresponding to 40% of the axial compressive strength is... This represents the control load value (Pa) for the elastic modulus test.

10.3.2.2 Deformation was measured using a static resistance strain gauge. The strain gauges were attached to the midpoints of the centerlines on two or four opposite sides of the specimen. The gauge length of the resistance strain gauge shall not be less than 20 mm and shall not be greater than half the height of the specimen.

10.3.2.3 Turn on the testing machine. When the upper pressure plate approaches the specimen, adjust the ball seat to ensure even contact. Pour the test material at a rate of (1000±50) N/s. Continue to uniformly load the specimen to the control load value for the elastic modulus test. Then unload to zero at the same rate, repeating this preloading process three times. See Figure

2.During the pre-compression process, observe whether the testing machine and measuring instruments are functioning properly, and adjust the specimen position according to the deformation readings on both sides or all four sides. The setting is such that the maximum difference in deformation is no more than 20% of the average value of deformation. Figure

10.4 Result Calculation and Value Interpretation

10.4.1 The elastic modulus of a single specimen is calculated according to formula (5), and the result is rounded to

0.1 GPa.

10.4.2 The results of the elastic modulus test shall be the arithmetic mean of the measurements of the three specimens in each group. If one of the specimens fails the test, the result shall be deemed invalid. When the difference between the axial compressive strength (f'cp) measured after elastic modulus and the axial compressive strength (fcp) of the mortar exceeds 20%, then the elastic modulus... The arithmetic mean of the values measured by the other two test specimens shall be used as the calculation result. If two test specimens exceed the above-mentioned requirements, the test result shall be invalid.

11.2 Instruments and Equipment

11.2.1 The specifications for the testing machine are the same as those in 7.2.1.

11.2.2 The static resistance strain gauge shall have an accuracy of 1 µepsilon, with a longitudinal gauge length of not less than 20 mm and not greater than half the height of the specimen, and a transverse gauge length of not more than 20 mm and half the height of the specimen. The gauge length of the resistor element is 20mm.

11.3 Test Procedure

11.3.1 Specimen Dimension Measurement The measurement shall be performed in accordance with the provisions of 9.3.1.

11.3.2 Poisson's Ratio Determination

11.3.2.1 Take three specimens and attach longitudinal resistance strain gauges at the midpoints of the centerlines of two or four opposite sides of each specimen. Attach transverse resistance strain gauges; take three additional specimens and determine the axial compressive strength (fcp) of the mortar according to the specifications in 9.3.2. The load value corresponding to 40% is the control load (Pa) of the Poisson's ratio test.

11.3.2.2 After adjusting the specimen position and connecting the resistance strain gauge wires, check the instrument's operation, start the testing machine, and when the upper pressure plate is in contact with the specimen... Adjust the ball seat as the specimen approaches to ensure even contact. Continuously and uniformly load the specimen at a rate of (1000±50) N/s until the Poisson's ratio test is completed. Control the load, then unload to zero at the same rate, repeating this preloading process three times. Durin...