GB/T 9966.6-2020Test methods for natural stone—Part 6:Determination of acid resistance (English PDF)

3.1 Principle

Ten minerals were selected as hardness standards and classified into 10 levels according to their hardness (see Table 1). The hardness level was determined by the ability to produce a noticeable scratch on the sample.

The minimum hardness grade of the standard is used as the relative hardness of the sample.

3.2 Instruments and Equipment

Mohs hardness tester. 10 hardness standard minerals, see Table 1.

3.3 Test Samples

Three test specimens with dimensions of 100 mm x 100 mm are required, and the test surfaces should be polished to a mirror finish or a fine finish.

3.4 Test Procedure

Place the sample stably on a hard, stable support, with the decorative side facing up. Select different standard scratch-resistant minerals from smallest to largest, and evenly apply the samples by hand.

Apply even pressure and perpendicularly scratch the sample surface with a new cutting edge of the standard scratching ore. Hold the standard scratching ore while scratching, keeping your wrist steady.

Move your arm horizontally while holding the standard scratched ore until a clear single-line scratch appears on the sample surface. (This is followed by a seemingly unrelated instruction to the test.)

The force applied should be moderate; the cutting edge of the standard scratch-marking ore should not break due to excessive force, resulting in double or even multiple scratch marks. Each piece

The sample was scratched four times, and the scratches on the sample surface were visually examined. The lowest hardness grade that produced a noticeable scratch on the sample was taken as the sample's hardness standard.

Mohs hardness.

4.1 Principle

A diamond punch of a specified shape is dropped freely from a fixed height onto the surface of a sample. The ratio of the punch's rebound height to its drop height is used to determine the yield.

The value is used to evaluate the hardness of the stone.

4.2 Instruments and Equipment

4.2.1 Type D Shore hardness tester

The main technical parameters are shown in Table 2, and its indication error is no greater than ±2.5.

Table 2D Technical Parameters of Shore Hardness Tester

Project technical parameters

Mass of the punch (g). 36.2

Punch drop height/mn 19

Punch tip spherical radius/mm

The relationship between the springback ratio of the punch and the Shore hardness value is HSD = 140 × (h/h).

4.2.2 Test bench

mass 4 kg.

4.2.3 Drying oven

The temperature can be controlled within the range of 65°C ± 5°C.

4.3 Test Samples

4.3.1

The specimens are 100 mm x 100 mm in length and width, and have a thickness greater than 10 mm. Three specimens are used in each group.

4.3.2

The sample should be representative of the quality characteristics of the variety, such as mineral composition and grain distribution.

4.3.3

The upper and lower surfaces of the sample should be parallel and flat, and the test surface should be mirror or matte.

4.3.4

The test surface should be free from defects such as pits, pinholes, and cracks.

4.4 Test Procedure

4.4.1

After drying the sample in a drying oven at 65 °C ± 5 °C for 48 h, place it in a desiccator to cool to room temperature.

4.4.2

The location of the test point on the sample is determined as shown in Figure 1.If the selected test point is located on the texture line of the sample, it can be offset.

3 mm to 5 mm. The distance between the test point and the edge of the sample should be greater than 10 mm.

4.4.3

Before the test, use a standard Shore hardness block to check whether the measured value of the hardness tester is within the tolerance range of the standard block, and adjust the test conditions.

4.4.4

Place the sample flat on the test bench, with a clamping force of approximately.200 N. During the test, operate the drum at a rotation speed of approximately 1 r/s to 2 r/s.

The reset speed is approximately 1 r/s to 2 r/s.

4.4.5

Each sample shall be tested at least nine points, and the measurements shall be accurate to 1 HSD.

4.5 Test Results

The arithmetic mean of the Shore hardness of each group of samples is taken as the Shore hardness of that group of samples.