The detection methods and acceptance standards for the flatness and smoothness of the floor after the construction by the concrete laser leveling machine

The detection methods and acceptance standards for the flatness and smoothness of the floor after the construction by the concrete laser leveling machine are a very professional and important issue. Although laser levelings can achieve extremely high quality standards, the final acceptance relies on objective data.

The following are the detailed testing methods and acceptance criteria:

I. Standards for Flatness Inspection and Acceptance

Flatness is the greatest advantage of the laser leveling machine, and its acceptance criteria are much higher than those of traditional processes.

Detection method

Straightedge and feeler gauge method (traditional, commonly used)

Tools: 2-meter or 3-meter national standard straightedge (or electronic straightedge), feeler gauge.
Method: Place the straightedge steadily on the ground and use a feeler gauge to measure the maximum gap between the bottom of the straightedge and the ground. At least 10 points should be measured in the same area (such as a slab or a room), and the measurement points should be randomly distributed and cover key parts such as the edges of walls and the bases of columns.
Advantages: Simple tools, convenient operation and intuitive.
Disadvantage: It reflects local "wavy" undulations and cannot accurately measure the overall flatness of a large area.

Level or total station measurement method (elevation method)

Tools: High-precision level, tower ruler or total station.
Method: Set up measurement points on the ground in a certain grid (for example, 1m×1m or 2m×2m), measure the elevation value of each point with a level, and then calculate the height difference between any two points or the standard deviation of the entire area.
Advantages: The data is precise and can generate an elevation map of the entire ground, making it the most scientific.
Disadvantages: It takes a long time and requires high technical skills from the operators.
F-Number System (Internationally recognized and the most scientific method)
This is the method stipulated in the ASTM E1155 standard of the United States. It is currently the mainstream and highest standard for evaluating the flatness of the floor internationally, and is particularly suitable for high-standard floors constructed by laser levelings.

Tools: Specialized floor profile meters (such as DipStick, DynaPulse, etc.) or continuous inertial profile measurement vehicles.
Evaluation index

F_F value (flatness value) : It measures the undulation of the large wavelength (>600mm) of the floor, reflecting the degree of "tilt" or "wave" of the floor. The larger the F_F value, the flatter the overall floor.
F_L value (levelness value) : It measures the undulation of the small wavelength (<600mm) of the floor surface, reflecting the degree of "roughness" or "micro-vibration" of the floor surface. The larger the F_L value is, the smoother the local area of the floor will be.
Method: Measurement and calculation are carried out by professionals and equipment in accordance with standard procedures.

Acceptance criteria

Domestic traditional standard (ruler method

Ordinary industrial floor: Within a 2-meter straightedge range, the flatness deviation is ≤ 4mm.
High-standard industrial floor /VNA ultra-flat floor: Within a 2-meter straightedge range, the flatness deviation is ≤ 2mm. For VNA flooring, it is usually required to be ≤ 1.5mm / 2m.
International F-Number Standard (Recommended for high-standard projects)

Ordinary industrial floor: F_F 20 / F_L 15
High-standard warehouse/logistics center: F_F 35 / F_L 25
VNA narrow channel library/super flat floor: F < sub > F < / sub > 50 / F < sub > L < / sub > 40 or higher (F < sub > F < / sub > 60 / F < sub > L < / sub > 50)
Commercial floor (such as supermarkets) : F_F 25 / F_L 20
Note: The specific F value should be clearly stipulated in the project contract or design documents.

Ⅱ. Inspection and Acceptance Standards for Smoothness (Surface Quality)

Smoothness is a comprehensive concept, encompassing appearance, wear resistance, dust resistance, etc., and it is more dependent on visual inspection and functional acceptance.

Detection method

Visual inspection method

Method: Observe the floor surface from different angles under well-lit conditions.
Inspection contents

Color uniformity: Whether the surface color is consistent, and whether there are obvious color differences, water marks, excessive or insufficient cement slurry.
Defects: Whether there are honeycombs, pitted surfaces, holes, peeling, sanding, or exposed stones.
Cracks: Check for visible plastic shrinkage cracks and dry shrinkage cracks to the naked eye. Focus on inspecting corners and areas with stress concentration.
Bubbles: The quantity and size of surface bubbles. Generally, it is required that there should not be too many bubbles with a diameter greater than 2mm.
Mark and gloss: Whether the surface is smooth and if there are any obvious machine marks or manual marks.
Hard object scratching method

Tools: Keys, coins and other hard objects.
Method: Use a hard object to scratch the surface with a certain force.
Judgment: If only light white scratches are left, it indicates that the surface hardness is good. If there is obvious sand grain shedding or deep grooves, it indicates that the surface strength is insufficient and sanding may occur.
Rebound instrument method

Tool: Concrete rebound tester.
Method: Indirectly calculate the strength of the floor surface through the rebound value. This method has certain errors and needs to be corrected in accordance with the standards.
Judgment: The rebound value should meet the design strength requirements.
Abrasion resistance test (Laboratory)

For places with high wear resistance requirements, cores can be taken on-site and sent to the laboratory for "abrasion tests" (such as ASTM C779).

Acceptance criteria

Visual quality

Color: The surface color is uniform and consistent, without obvious color differences or contamination.
Defects: The surface is dense and smooth, free from quality defects such as honeycombing, pitting, cracks, sanding, peeling, and hollowing.
Seam: The cutting seam should be straight, with uniform width and depth, and no missing edges or corners.
Surface hardness and anti-dusting property

Scratching with a hard object should not produce sanding or loose substances.
In daily use, the movement of vehicles and the movement of people should not cause dust to rise on the ground.

Ⅲ. Other important Acceptance Indicators

In addition to flatness and smoothness, the following indicators also need to be paid attention to
Elevation and slope

Tools: Level, total station.
Standard: The allowable deviation between the measured elevation and the designed elevation is usually ±10mm. In areas with drainage requirements, the slope should comply with the design requirements and there should be no water accumulation.
Levelness (not flatness)

Tools: Laser leveler, level.
Standard: It refers to the degree of inclination of the entire floor relative to the absolute horizontal plane. For equipment foundations with strict level requirements, the allowable error is very small (such as ±3mm/10m).

Summary and Suggestions

Inspection items	Main detection tools	Reference for High-standard acceptance
Flatness	2-meter straightedge, feeler gauge	≤ 2mm / 2m (Recommended ≤ 1.5mm / 2m)
	F-Number measurement system	F<sub>F</sub> 50 / F<sub>L</sub> 40 (Applicable to VNA floor)
Smoothness	Visual inspection, hard object scratches	The color is uniform, without cracks, sanding or holes, and there is no sanding when scratched
Elevation	Level, total station	±10mm
Slope	Level, total station	It meets the design requirements and there is no water accumulation

Important Notice
Prior agreement: All acceptance criteria (especially the methods and standards for flatness) must be clearly stipulated in the contract before construction to avoid disputes later on.
Comprehensive inspection: During the acceptance process, a combination of a thorough census and key spot checks should be conducted; it is not advisable to merely focus on a few points.
Environmental conditions: The inspection should be carried out after the concrete has reached a certain strength and the surface should be cleaned thoroughly.
For high-standard floors constructed by laser leveling machines, it is strongly recommended to introduce the F-Number system for acceptance, as it can most scientifically and comprehensively evaluate the quality and performance of the floor, especially suitable for projects with extreme requirements for the ground such as automated warehouses and logistics centers.
 

Note: The parameters provided in this document are for reference only and are not mandatory. Due to differences in technical characteristics between different brands and models of laser levelers, please consult the manufacturer for a suitable solution before actual operation. This reference document assumes no responsibility for any issues arising from failure to follow the manufacturer's instructions.

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