What are the common reasons for holes and pores in the surface layer of terrazzo slabs?

The occurrence of holes and pores in the surface layer of terrazzo slabs is a common quality problem, which is closely related to materials, construction technology, maintenance, and post-processing. The following are common reasons and detailed analysis:

1, Material factors
Quality issues with aggregates
Uneven particle size of aggregate: If the particle size difference of aggregate (such as crushed stone, glass flakes) is too large, small particles may not be filled tightly, and gaps may form between large particles, resulting in loose surface layer.
Impurities in aggregates: Mixing soil, dust, or organic matter into aggregates can reduce the bonding strength with cement and form weak points.
Inappropriate proportion of aggregates: The ratio of cement to aggregates is unreasonable (such as insufficient cement dosage), resulting in insufficient bonding force and easy cracking or detachment of the surface layer.
Cement quality issues
Insufficient cement strength: Using low-grade or expired cement has low strength after hardening and is easily worn or peeled off.
Poor reaction between cement and aggregates: Some aggregates (such as stone with high alkali content) undergo alkali aggregate reaction with cement, generating expansion stress, resulting in surface cracking or pores.
Additive issue
Improper use of additives, such as water reducers, retarders, etc., with excessive or insufficient dosage, may affect the cement hydration reaction and lead to a decrease in the compactness of the surface layer.
Incompatibility between pigments and cement: In colored terrazzo, the chemical properties of pigments and cement do not match, which may cause uneven color or local peeling.

2, Construction process issues
Improper handling at the grassroots level
Uneven base layer: Uneven base layer can lead to uneven thickness of the surface layer, and thin areas are prone to cracking or holes.
Unclean base layer: Residual oil stains, floating dust or loose materials on the base layer will reduce the adhesion between the surface layer and the base layer.
Failure to apply interface agent: Failure to use interface agent or uneven application, resulting in delamination between the surface layer and the base layer.
Mixing and paving issues
Uneven mixing: Insufficient mixing of cement, aggregates, water, and additives, resulting in uneven proportions of local materials and the formation of weak areas.
Uneven paving thickness: The thickness difference of the surface layer is too large, and thin areas are prone to wear or cracking.
Insufficient vibration: Failure to use vibration equipment or insufficient vibration time results in low surface compaction and high porosity.
Pressing and finishing issues
Improper timing of calendering: Premature calendering (cement not yet fully set) can lead to excessive surface floating slurry; If the compaction is too late (the cement has already set), it cannot be compacted and holes will form.
Problem with calendering tools: Using inappropriate calendering tools (such as iron plates that are too heavy or too light), or using uneven calendering directions, can result in uneven surfaces.
Inadequate finishing: Failure to promptly repair local defects (such as bubbles and cracks) during finishing, resulting in residual pores.
3, Maintenance and protection issues
Insufficient maintenance
Short maintenance time: cement hydration reaction is not completed, surface layer strength is insufficient, and it is prone to wear or cracking.
Improper maintenance environment: Low temperature (below 5 ℃) or insufficient humidity can delay cement hardening and lead to loose surface layer.
Unprotected protection: During the maintenance period, plastic film or grass curtains are not covered, and water evaporates too quickly, forming shrinkage cracks.
Early use or heavy pressure
Use before the maintenance period expires: The surface strength does not meet the design requirements and is easily damaged by external forces.
Heavy object stacking or impact: During construction or early use, heavy object stacking or mechanical impact may cause cracking or holes in the surface layer.
4, Post processing issues
Improper grinding and polishing
Excessive grinding pressure: Excessive pressure during rough grinding may damage the surface structure and form holes.
Improper selection of polishing agent: Using mismatched polishing agents or insufficient polishing time can result in low surface glossiness and easy wear.
Unfinished pores: After grinding, the pores were not filled in a timely manner with materials such as epoxy resin, resulting in residual defects.
Insufficient cleaning and maintenance
Acid alkali corrosion: Long term exposure to acidic or alkaline cleaning agents may corrode the surface layer and cause pore enlargement.
Hard object scratching: Cleaning with sharp tools or scratching with hard objects may scratch the surface and form pores.

5, Other factors
design flaw
Thin surface layer thickness: Insufficient design thickness (such as less than 20mm) makes it difficult to withstand usage loads and prone to cracking.
Improper drainage slope: Poor drainage can lead to water accumulation, and long-term soaking may weaken the strength of the surface layer.
environmental factors
Temperature changes: Frequent temperature fluctuations (such as large temperature differences between day and night) may cause thermal expansion and contraction of the surface layer, leading to the formation of cracks.
Foundation settlement: Uneven settlement of the foundation may lead to cracking or holes in the surface layer.
Prevention and repair suggestions
Optimize material selection: Select aggregates with uniform particle size and no impurities, control cement grade and dosage, and use additives reasonably.
Strict construction process: Ensure that the base layer is flat, clean, evenly mixed, the paving thickness is consistent, and the timing and tools for pressing are appropriate.
Strengthen maintenance management: The maintenance time should not be less than 7 days, keep the environment moist, and avoid early use or heavy pressure.

Detailed post-processing: Fill the pores in a timely manner after grinding, select matching polishing agents, and regularly clean and maintain.
Rationalization of design: Design sufficient thickness according to the usage scenario to ensure a reasonable drainage slope.
Through the above measures, the occurrence of holes and pores in the surface layer of terrazzo slabs can be effectively reduced, improving the quality and durability of the project.