Introduction of JGJ70 Building Mortar Tensile Bond Strength Test

News

Introduction of JGJ70 Building Mortar Tensile Bond Strength Test

Construction mortar refers to the engineering materials used for masonry, plastering, ground engineering and other purposes of industrial and civil buildings with inorganic cementitious materials, fine aggregates and admixtures as the main materials.

1. Test Preparation

1.1 Test conditions for tensile bond strength of building mortar: the temperature is (23±2)℃, the relative humidity is 45%-75%

1.2 Tensile testing machine: choose a tensile testing machine with a suitable range according to the tensile force value of the test sample. The reference pictures and technical parameters of the testing machine are as shown in Figure 1 and Table 1. The failure load of the mortar tensile bond strength test should be in the range of 20% to 80% of the range of the tensile tester.

图片.png

Figure 1: Tensile testing machine

No	Item	Specification
1	Force capacity	20KN and lower	30/50KN	100KN
2	Measuring range	1%-100%FS
3	Accuracy of force value	Less than ±1% of set value
4	Precision of displacement	0.01mm
5	Accuracy of displacement value	±1%
6	Deformation measuring range	0.4%-100%FS
7	Accuracy of deformation measuring	±0.5%
8	Resolution of deformation	0.01mm
9	Force speed range	0.005-5%FS/S
10	Accuracy of force speed	Less than ±1% of set value
11	Deformation speed range	0.02-5%FS/S
12	Accuracy of deformation speed control	When set value is less than 0.05%FS，error is less than ±2.0% of set value When set value is more than 0.05%FS，error is less than ±0.5% of set value
13	Displacement speed range	0.001-500mm/min
14	Accuracy of displacement speed	When speed is less than 0.01mm/min，error is less than ±1.0% of set value When set value is more than 0.01mm/min，error is less than ±0.2% of set value
15	Range of constant force, constant deformation, constant displacement control	0.5％～100％FS
16	Accuracy of constant force, constant deformation, constant displacement control	When set value is less than 10%FS，error is less than ±1.0% of set value When set value is more than 10%FS，error is less than ±0.1% of set value
17	Accuracy of deformation speed	When set value is less than 0.05%FS，error is less than ±2.0% of set value When set value is more than 0.05%FS，error is less than ±0.5% of set value
18	Tension space	700mm	700mm	700mm
20	Voltage	Single phase,220V±10%,50Hz(110V)
21	Motor power	0.75KW	0.75KW	1.5KW
22	Dimension	750x480x1700mm	720x520x1800mm	900x600x2100mm
23	Weight	280kg	350kg	450kg

Table 1: Technical parameters of tensile testing machine

1.3 Tensile bond strength test fixture

The test fixtures for tensile bond strength consist of a steel backing plate (Fig. 2), a forming frame (Fig. 3), and a steel upper and lower clamp (Fig. 4). The outer frame size of the steel backing plate is 70x70mm, the inner frame size is 43x43mm, and the thickness is 3mm. The outer frame size of the forming frame is 70x70mm, the inner frame size is 40x40mm, and the thickness is 6mm;

图片.png

Figure 2: Steel Backing Plate

图片.png

Figure 3: Forming frame

图片.png

Figure 4: Upper and lower clamps

1.4 Specimen Preparation

Place the forming frame on the forming surface of the prepared 70x70x20mm cement mortar test block, pour in the prepared dry-mixed mortar or the wet-mixed mortar taken from the site, and use a tamper to evenly smash the specified number of times, and artificially shake it for specified number of times, rotate 90 degrees, and then confirm the specified amount, then use a scraper to smooth the surface at a specified angle, gently demould, and maintain it in an environment of (23±2) °C and a relative humidity of 60%-80% to the specified age. At least 10 test pieces are prepared. Coat the surface of the sample with high-strength adhesive, then bond with the upper tensile jig, and cure for 24 hours.

2. Test machine operation steps

2.1 Connect the testing machine and computer software, and turn on the power. Turn on the switch on the testing machine and open the testing software on the computer.

2.2 Select the corresponding test method from the test software or edit the test steps through the programming function of the test machine.

2.3 Create a new test on the data board of the test software, and input test related information, such as test temperature, test person, sample size, etc.

2.4 Adjust the beam of the tensile testing machine through the remote control box, and install the tensile test fixture and tensile test on the tensile testing machine.

2.5 Select the test speed on the control panel of the test software, clear the test force, displacement and deformation value to zero, click the button to start the test, and the test machine will automatically carry out the test.

2.6 When the sample fails, the testing machine automatically stops and records the maximum value, and the tensile bond strength is automatically calculated according to the following formula.

图片.png

In the formula: f_at—tensile bond strength of mortar (Mpa)

F—the force value when the sample is broken (N)

Az—bonding area (mm²)

2.7 Repeat the above steps to complete 10 samples and calculate the average value.

Note: If the difference between the strength value of a single sample and the average value is greater than 20%, the test values with the largest deviation shall be discarded successively until the difference between each test value and the average value does not exceed 20%. When there are no less than 6 valid data in 10 samples, use the average value of the remaining data as the test result, accurate to 0.01Mpa. When there are less than 6 valid data in 10 samples, the test results of this group are invalid, and the samples need to be re-prepared for testing.

We specializes in the production and sales of electronic and hydraulic universal testing machine,electronic and hydraulic tensile testing machine, bending testing machine, horizontal tensile testing machine, impact Testing machine, concrete cement compression testing machine, compressive and flexural integrated testing machine, pellet compression testing machine, manhole cover compression testing machine, tensile stress relaxation testing machine, etc. Welcome your calling or visit