I. Bubble Issues of Cement-Based Self-Leveling: One Bucket Ruins the Whole Floor

Cement-based self-leveling material serves as a core material for commercial floors, industrial floorings and floor heating backfill leveling. The construction seems simple — pour it on the ground and let it self-level — yet 80% of the final floor effect depends on the mixing process.

Cement-based self-leveling features high fluidity (flow ≥130mm), low viscosity (typically 3,000~12,000cps), and contains a large amount of water reducer and defoamer. Many people mistakenly believe that "defoamer added in formula eliminates the need for extra defoaming" — this is the biggest misunderstanding.

What defoamers can and cannot do:

✅ Defoamers reduce the surface tension of bubbles and help large bubbles rupture

❌ Defoamers cannot remove tiny closed bubbles trapped inside paste

❌ Defoamers cannot stop new bubbles entrained continuously during mixing

❌ Defoamer dosage has an upper limit; excessive addition will reduce flowability and cause shrinkage cavities

Bubble manifestations in self-leveling construction:

• Pinholes: Bubbles burst after reaching the surface, leaving 0.5~3mm pores. The dried floor is covered with pinholes, resembling lunar surface.

• Pitting: Numerous micro bubbles form rough texture on the surface, losing the mirror finish that self-leveling should deliver.

• Internal cavities: Bubbles sealed inside the self-leveling layer reduce effective bearing thickness and impair compressive strength.

• Mottled color difference: Bubble positions show different color from surrounding areas, forming irregular spots after curing.

According to industry test data, cement-based self-leveling mixed by traditional paddle mixer normally has pinhole density of 50~150 pcs/㎡ after construction, and severe areas exceed 300 pcs/㎡. Repairing pinholes requires extra grinding and filling, adding 3~5 yuan per square meter and 1~2 days of construction period.

II. Real Performance of Four Mixing Methods for Self-Leveling

2.1 Manual Mixing — Strictly Not Recommended for Self-Leveling

Manual mixing fails to reach the uniformity and fluidity required by self-leveling. Powder agglomeration, uneven water addition and insufficient activation of additives lead to poor flowability, fish eyes, shrinkage cavities, color difference and other defects.

Industry standards clearly stipulate: Manual mixing is prohibited for cement-based self-leveling; mechanical mixing must be adopted.

2.2 Handheld Electric Mixer (Paddle/Propeller Type) — Standard on Construction Sites, Root Cause of Pinholes

This mixing method is adopted by over 90% construction sites: low-speed electric stirrer (300~600rpm) with propeller blades immersed in the bucket for 3~5 minutes mixing.

It seems well mixed, but it is the primary source of pinholes:

Test Data: Cement-based self-leveling (viscosity 8,000cps) mixed by handheld paddle mixer owns slurry porosity of about 6.5% after 3-min mixing. After standard construction, floor pinhole density reaches roughly 120 pcs/㎡, surface roughness Ra approx 85μm.

2.3 Vertical Mixer (Paddle/Frame Type) — Factory Applicable, Limited On-site

Some factories or large projects adopt vertical mixers for pre-mixing self-leveling slurry. It delivers large volume and uniform mixing, but bulky size restricts on-site mobility. Ordinary paddle type still causes air entrainment, while vacuum version is high-priced.

2.4 Planetary Mixing Defoaming Machine — Mixing & Defoaming in One Step

SIENOX planetary mixing defoaming machine fundamentally changes the mixing logic of self-leveling:

Core Difference — No Paddles + Vacuum:

• No mixing paddles inside material cup; slurry movement is fully driven by centrifugal force and gravity generated by planetary motion.

• No new bubbles entrained. Meanwhile vacuum environment expands, floats up and bursts existing bubbles for discharge.

• Mixing and defoaming completed in one step, no standing or secondary mixing required.

Why self-leveling is especially suitable for planetary defoaming?

Self-leveling slurry has low viscosity (3,000~12,000cps) and great flowability, meaning:

1. Bubbles rise fast in low-viscosity slurry for higher vacuum defoaming efficiency.

2. Circulation formed by planetary motion in low-viscosity slurry is more intense for better homogeneous mixing.

3. Slurry after defoaming maintains mirror finish even after full pouring.

III. Planetary vs Paddle: Actual Test Comparison on Cement-Based Self-Leveling

Take cement-based self-leveling (viscosity 8,000cps) as test object. Handheld paddle mixer (500rpm) and SIENOX MIX1000PLUS planetary mixing defoaming machine are adopted separately for treatment:

Conclusion: After adopting planetary mixing defoaming machine, slurry porosity of self-leveling drops from 6.5% to 0.2%, floor pinholes reduce from 120 pcs/㎡ to 0 pcs/㎡, surface roughness falls from 85μm to 12μm (mirror finish achieved), compressive strength rises by 14%. Processing time is shortened from 11 minutes to 3 minutes without secondary mixing.

IV. Actual Tests under Three Typical Self-Leveling Working Conditions

Case 1: Commercial Floor Leveling (8,000cps)

Result: Slurry porosity drops from 6.5% to 0.2%, floor pinhole density reduces from 120 pcs/㎡ to 0 pcs/㎡, surface roughness Ra falls to 12μm (mirror finish), flow retention rate reaches 98%, 28-day compressive strength 32MPa.

Case 2: Floor Heating Backfill Leveling (5,000cps)

Result: Slurry porosity drops to 0.15%, thermal conductivity remains 1.2 W/(m·K) (tighter heat conduction channels after bubble removal), zero pinholes on surface. 3mm-thick self-leveling layer reaches compressive strength of 35MPa with no cracking risk for floor heating coverage.

Case 3: Heavy-duty Factory Floor (12,000cps)

 Result: Slurry porosity drops to 0.3%. The 5mm-thick self-leveling layer achieves 28-day compressive strength of 38MPa and flexural strength of 8.5MPa. Zero pinholes and pitting on surface, no sanding or cracking after 6 months of forklift rolling.

V. Before & After Improvement Overview

VI. Recommended Process — Four-Step Planetary Mixing & Defoaming Process

Step 1 Precise Proportioning

Accurately weigh self-leveling powder and clean water according to product specifications, and control the water-cement ratio error within ±0.5% (self-leveling is extremely sensitive to water-cement ratio).

Step 2 Feeding & Pre-mixing

Pour water into the mixing cup first, then slowly add powder (to avoid powder scattering). Carry out low-speed revolution pre-mixing for 1 minute to fully wet powder preliminarily.

Step 3 Vacuum Mixing & Defoaming

Start vacuum system to -95KPa, set revolution 2,000rpm / rotation 1,000rpm and run for 3 minutes. Mixing and defoaming are finished in one step, no standing or secondary mixing needed.

Step 4 Direct Construction

Take out mixing cup and pour slurry directly for construction. The slurry has excellent fluidity and can be spread within 3 minutes. No auxiliary exhaust with defoaming roller required after construction.

Free Sample Test

Send your self-leveling samples to us. We will test defoaming parameters and issue test reports.

SIENOX — 20-year Original Manufacturer of Mixing & Defoaming Equipment