Analysis of the Causes of Hollowing and Delamination in Vitrified Tiles
Release Time:
2020-06-22
Source:
Vitrified tiles (also known as polished, enhanced porcelain tiles—hard, dense ceramic tiles) are now widely used in interior decoration thanks to their mirror-like smooth surface, brilliant luster, high hardness, resistance to scratches and breakage, and ease of installation.
However, due to an insufficient understanding of its performance characteristics, the conventional cement-bonding method was still employed. After one year, subjected to the temperature fluctuations of both winter and summer, widespread hollowing and detachment occurred—initially limited to a few isolated tiles, the problem rapidly escalated into extensive areas of hollowing, followed by tile loss. This posed significant safety risks and severely compromised the quality of the development. Moreover, the comprehensive remediation required for walls with hollow tiles results in substantial financial losses; and if the repair approach is improper, even a full-scale renovation may fail to completely prevent recurrence of hollowing.
Analysis of the Causes of Hollowing and Detachment in Vitrified Tiles
1. The survey reveals that hollow sounds in wall tiles primarily occur at the interface between the tiles and their cement bonding layer, with the bonding layer and tiles detaching. What begins as hollowing in one or two tiles can progress to widespread hollowing and eventual tile detachment. The primary cause is the poor bond strength and durability of the tile–cement interface, leading to the occurrence of hollowing.
2. Compared with ordinary glazed tiles, vitrified tiles have a lower water absorption rate, with a standard limit of E ≤ 0.5%, whereas earthenware tiles have a standard limit of E ≤ 10%. Consequently, the bond strength of vitrified tiles is significantly lower than that of earthenware tiles, which necessitates the use of bonding materials with high adhesive strength. If tiles with higher water absorption are used and the same installation procedures are followed, the occurrence of hollow-sounding areas will be reduced.
3. Tile sizes are continually increasing; for example, the first-floor lobby and the basement lobby both use 600×600 mm wall tiles. Larger tile dimensions make them more susceptible to volumetric changes due to thermal expansion and contraction. Porcelain tiles have a coefficient of thermal expansion and contraction of approximately 4×10⁻⁶, whereas concrete exhibits a shrinkage rate more than twice that of porcelain tiles. When cement shrinks, the shrinkage rates of the porcelain tiles and the substrate differ, which can lead to delamination between the two dissimilar materials. Therefore, the bonding material must possess adequate flexibility.
4. Vitrified tiles have high material strength but are sensitive to temperature changes. Due to asynchronous thermal expansion and differing coefficients of thermal expansion between the tiles and the cement-based substrate, large-format tiles subjected to significant temperature differentials can develop thermal stress during installation. Seasonal temperature fluctuations can further reduce bond strength, compromising the adhesion between the tile and the substrate and leading to hollow-sounding wall tiles. Consequently, as residential projects experience alternating winter and summer conditions, instances of wall-tile delamination gradually become apparent.
5. Failure to adhere strictly to code requirements, improper storage of construction cement resulting in loss of strength, and excessive shelf life of cement mortar have all reduced the final setting strength of the bonding layer, thereby significantly diminishing the effective bond strength between the wall tiles and the substrate.
6. Poor verticality of wall plastering, coupled with locally excessive and uneven overall thickness of the adhesive layer during tile installation, is also one of the factors contributing to hollow-sounding wall tiles.
7. When the strength of the rough-finishing plaster layer is low, hollowing may occasionally occur between the rough-finishing plaster layer and the base layer; this phenomenon does exist, but it is relatively rare.
In summary, the primary location of hollow-sounding tiles is at the interface between the wall tiles and the adhesive layer. The two material characteristics of vitrified tiles—low water absorption and high strength—and the lack of synchronous performance between these tiles and the cement-based adhesive layer are the root causes of tile delamination.
