Epoxy terrazzo can be installed directly on raw concrete subfloors, but strict substrate conditions and specialized processes must be met. Failure to comply 

may cause cracking, delamination, or other failures. Key requirements and techniques are outlined below:

I. Prerequisites for Raw Concrete Subfloors

‌Substrate Strength Compliance

Must be solid with no hollow spots; compressive strength ≥25MPa

No severe dusting/spalling – if unstable, re-pour concrete or repair with high-strength anti-crack mortar

Moisture content ≤8% (no condensation via plastic sheet test); install vapor barrier if exceeding limit

‌Flatness & Defect Remediation

Flatness tolerance: ≤3mm/2m – grind high spots, fill lows with epoxy mortar

Cracks: Cut V-grooves, fill with epoxy mortar + fiber mesh reinforcement

Expansion joints: Seal with flexible sealant strips

II. Critical Process Adaptations

‌Reinforced Crack Prevention System

Apply 2 coats solvent-free epoxy primer (0.3kg/m²) for pore sealing and adhesion

Embed fiberglass mesh (100mm overlaps) fixed with primer to create tensile skeleton layer

Optimal: Add polyethylene isolation membrane + anti-crack leveling mortar to block substrate stress

‌Aggregate Placement Optimization

"Zoned progressive placement": Install complex patterns first with 4+ hr intervals between colors

Increase aggregate thickness to 8-10mm for impact resistance

Eliminate air pockets using vibrating trowels after placement

‌Grinding & Sealing Protocol

Post coarse-grinding: Execute two-stage grout filling:

Fill voids with epoxy mortar + 100-grit quartz sand

Seal micro-pores with fine quartz powder

Apply epoxy terrazzo-specific sealer before topcoat; post-polish gloss: 60-70°

III. Prohibited Scenarios & Alternatives

‌Strictly Prohibited If:

Substrate strength inadequate (foot-traffic causes dusting)

Moisture content >12% or active water seepage

Heavy vehicle zones without reinforced concrete base

‌Alternative Solutions:

Dusting floors: Apply densifier/hardener before epoxy terrazzo

Severely damaged slabs: Remove and re-pour concrete

Link to this article：https://springpaint.com/news/Epoxy-Terrazzo-Processes_61.html