How To Determine The Grinding Time Of Anti-static Terrazzo?

The determination of the grinding time for anti-static terrazzo requires comprehensive consideration of material characteristics, environmental conditions, and construction requirements. The core is to ensure that the concrete reaches sufficient strength and the anti-static function is stable. The following are specific judgment methods and precautions:

1, The core basis of grinding time: concrete strength and anti-static performance
Requirements for compressive strength
Anti static terrazzo needs to withstand the pressure of grinding machinery, usually requiring concrete compressive strength of 7-10 MPa (approximately equivalent to the strength of C15-C20 concrete). At this point, the surface of the concrete has hardened, but the interior still maintains a certain degree of plasticity, making it easier to polish a smooth surface.
Stability of anti-static function
Anti static materials (such as conductive fibers and conductive powders) need to be fully combined with concrete to form a stable conductive network. Premature grinding may damage the conductive layer and cause the resistance value to exceed the standard; If the grinding is started too late, it may increase the difficulty of polishing due to the hardness of the concrete.

2, Specific judgment method
1. Experimental method (recommended)
Steps:
Select 3-5 testing points in the construction area, press the concrete surface with your fingers, and proceed to the next step of testing when there are no obvious fingerprints and no stickiness.
Use a rebound or indentation tester to test the strength of concrete to ensure it meets the design requirements.
Use sandpaper or a small grinding disc to lightly grind at the test point and observe whether there is sanding, powder falling, or conductive material detachment. If there are no abnormalities, the grinding can be officially started.
2. Time reference method (combined with environmental adjustment)
Conventional environment (temperature 20 ± 5 ℃, humidity 50% -70%):
Ordinary anti-static terrazzo: 3-5 days (3 days in summer and 5 days in winter).
Anti static terrazzo with early strength agent added: 2-3 days.
Extreme environmental adjustment:
Low temperature (<10 ℃) or high humidity (>80%): Delay for 1-2 days, or take heating/dehumidification measures.
High temperature (>30 ℃) or low humidity (<30%): 0.5-1 day in advance, but maintenance needs to be strengthened.
3. Empirical judgment method (auxiliary reference)
Visual observation: The concrete surface changes from dark gray to light gray, and there is no obvious water seepage.
Auditory judgment: Lightly tap the surface with a metal tool, and a clear (not dull) sound indicates hardening.
Touch test: There are no obvious footprints on the foot, and the surface roughness is moderate (non powdery peeling).

3, Key inspection before grinding
Integrity of conductive layer: Use a megohmmeter to measure surface resistance and ensure compliance with design requirements (typically 1 × 10 ⁴Ω -1 × 10 ⁹ Ω).
Ground flatness: Check with a 2m ruler, with a gap of ≤ 3mm, to avoid unevenness after polishing.
Environmental conditions: Temperature ≥ 5 ℃, humidity ≤ 85%, avoid construction in rainy or windy weather.
4, Precautions after grinding
Staged polishing:
Rough grinding (30-60 mesh diamond grinding disc): Remove surface slurry and expose conductive material.
Medium grinding (100-200 mesh): Level the ground and repair rough grinding marks.
Fine grinding (over 300 mesh): Polish the surface to ensure uniform anti-static performance.
Real time detection: Check the resistance value after each stage of polishing. If the deviation is greater than 15%, local repair or re polishing is required.
Maintenance and sealing: After polishing, apply anti-static sealing agent to enhance wear resistance and stabilize conductivity.

5, Common Misconceptions and Solutions
Misconception 1: Judging solely based on time and ignoring environmental impact
Solution: Adjust the time based on temperature and humidity, or verify through experimental methods.
Misconception 2: Premature grinding leads to damage to the conductive layer
Solution: Prioritize detecting the resistance value and confirm the stability of the conductive material before construction.
Misconception 3: Failure to seal in a timely manner after polishing leads to a decline in anti-static performance
Solution: Seal within 24 hours after polishing to prevent dust and moisture from entering.
By scientifically determining the grinding time and strictly controlling the construction process, the anti-static terrazzo can ensure both aesthetics, durability, and stable anti-static function, meeting the cleanroom needs of industries such as electronics and medicine.