Self-Leveling Cement Construction (Part 1): Preparation Phase

I. Inspection

Before construction, the concrete substrate must be tested to assess its overall condition, including strength, flatness, hollowing, cracking, etc.

1. Pull-Off Test

Self-leveling cement-based materials provide a wear-resistant surface layer, so the main load-bearing capacity depends on the substrate. Therefore, the substrate’s strength must be tested, and the pull-off strength must be greater than 1.0 MPa. Meanwhile, identify weak areas requiring repair.Test Procedure:

First, clean and smooth the ground surface.

Drill a 2cm-deep hole with a hollow drill bit and remove the core sample.

Apply bonding adhesive to both the drilled area and the test equipment, then bond the equipment to the ground.

Perform the pull-off test after the adhesive cures and record the results.

2. Flatness Test

Use a laser level to measure height differences on the ground, mark the areas, and ensure compliance with floor acceptance standards.Alternative Test Method:

Place a 2-meter straightedge on the ground and measure the gap size (recorded as the deviation value).

The height difference must be less than the thickness of the self-leveling layer to be qualified. Record all measurements.

3. Quality Inspection of Self-Leveling Material

Press the self-leveling cement packaging bag by hand to check for caking. Discard any caked material.

Verify the production date to ensure the product is not expired.

Confirm that all materials are from the same batch. Record and report any discrepancies.

II. Pre-Treatment

1. Substrate Preparation (Based on Substrate Condition)

Remove all stacked materials and equipment from the construction area.

Conduct initial cleaning with brooms, then scrape off scattered mortar, adhesive, etc., with a putty knife.

Treat damaged or uneven substrates: Chisel out weak layers and remove impurities completely.

2. Sandblasting & Grinding

Use a professional floor sandblasting machine to remove laitance and loose materials from the substrate, creating a rough surface for optimal bonding. The machine is equipped with a high-power vacuum cleaner to effectively prevent dust pollution.

Use a small scarifier to grind corners and edges of concrete columns/walls.

Focus on removing oil stains; regrind areas where stains persist after initial treatment.

After sandblasting, the substrate should be dense, free of loose laitance, debris, and impurities.

Grind the base of walls and columns with an angle grinder fitted with a diamond disc to ensure a 90° angle between the floor and walls.

Recheck for cracks and hollowing after grinding and vacuuming; focus on grinding local problem areas.

3. Vacuum Cleaning

Thoroughly remove dust generated during grinding using a vacuum cleaner.

4. Substrate Leveling & Repair

For extremely rough or uneven substrates, apply a leveling layer. Record the locations of cracks and hollowing, cut open these areas locally, and repair with self-leveling mortar.

Repair methods for common defects are detailed below:

III. Defect Repair Methods

1. Hollowing Repair

Remove the hollowed area and fill with repair material:

1.Clearly mark hollowed areas with colored pens.

2.Cut along the marked lines with a cutting machine, then chisel out the hollowed concrete (take dust control and protection measures during cutting).

3.Filling & Repair:

a. Clean the excavated area with a vacuum cleaner, then apply an interface agent.

b. Pour self-leveling mortar into the area.

2. Peeling Repair

Completely remove all peeling areas (no residue allowed), as any remaining peeling will cause delamination after self-leveling construction.

3. Crack Repair

1) Cracks < 0.3mm

After sandblasting the floor, carefully inspect and thoroughly clean the cracks with a vacuum cleaner.

No additional repair is needed; the interface agent used for self-leveling will seal the cracks.

2) Non-Structural Cracks (0.3mm < Width < 1mm)

a. Sandblast the cracks carefully, then clean with a vacuum cleaner. If soil, debris, or other bond-impairing substances remain, cut a V-groove along the crack with a cutting machine.b. Reinforce with epoxy resin and glass fiber mesh.

3) Structural Cracks in Industrial Floors (Width > 1mm, Through & Inactive)

a. Sandblast the cracks carefully, then clean with a vacuum cleaner. If soil, debris, or other bond-impairing substances remain, cut along the crack with a cutting machine.b. Cut vertical cracks to a depth of 0.5-2.0cm, repeating the cut every 15-20cm until the end of the crack.c. Insert 10cm-long steel nails or reinforcement bars into the cut cracks.d. Pour low-viscosity epoxy resin into the cracks and fill with a trowel.e. Sprinkle quartz sand on the surface to ensure good bonding with the top layer material.

IV. Measure Ground Height Differences

Measure height differences, remove protruding objects (e.g., steel bars) from the ground, and protect non-removable objects.

Seal room doorways with wooden strips before construction to prevent self-leveling mortar from overflowing and forming slopes.

V. Construction Sequencing

Determine the construction order, screeding direction, and elevation marks.

VI. Interface Agent Application

Apply two coats of interface agent to the prepared substrate:

1. First Coat

Dilute the interface agent with water at a ratio of 1:5.

Apply evenly to the cleaned floor and allow to dry for approximately 2 hours.

Wait 12 hours before applying the second coat.

2. Second Coat

Dilute the interface agent with water at a ratio of 1:3.

Apply evenly to the floor and allow to dry for approximately 3 hours.

Key Requirements for Interface Agent Application

Ensure uniform coverage without missing areas; avoid local puddles.

Fully seal pores (use a foam brush for application; saturate areas with sanding or high water absorption).

VII. Snap Lines & Grid Division

Snap lines and divide the construction area into grids based on the mortar pump’s capacity and on-site working conditions.

Use a chalk line to snap lines, with grids typically centered on columns.

Adhere foam strips along the snapped lines to form dividers.

VIII. Finished Product Protection

Protect on-site finished products with masking tape to prevent contamination.

Attach 2mm-thick double-sided tape along the base of walls and columns to separate the self-leveling layer from the structure, avoiding floor cracking due to concrete expansion or structural settlement.

Drive iron nails at both ends of concrete expansion joints, leaving 1cm exposed above the ground to align the self-leveling expansion joints with the original concrete expansion joints after construction.

IX. Shot Blaster Operation Guidelines

Regularly inspect wear parts during operation, adjust shot blasting quality in real time, and promptly identify and repair equipment malfunctions.

Clean the air compressor’s dust hopper when dust absorption decreases.

Ensure the connecting pipe between the shot blaster and air compressor is straight (no figure-8 bends) during operation; do not pull the pipe forcefully for long distances.

Check the oil level of the air compressor before startup; add oil if below the specified level.

Operate the shot blaster in straight lines as much as possible, with each pass overlapping the previous one by 1/4.

When the equipment cannot make large turns, close the sand discharge port, lower the lever, and idle to turn (do not force a turn).

Stop immediately if abnormal noises occur, identify the cause, and repair.

Recycle steel shots promptly; do not operate the equipment on scattered steel shots to avoid damage and reduced efficiency.

Park the equipment in a safe location after daily use, unplug the power supply, and store tools and accessories in the warehouse.