Finishing materials which are bonded to wet slabs peel off at a high probability (reference to Photo 1). We are researching to propose the moisture management index of slab surface. In this paper, targeting at resilient floor coverings as a basic stage, the relation among bond strength and water content of slab surface was quantitatively examined. While drying specimens those were modeled on concrete slabs, floor covering materials were adhered on specimens (reference to Fig 1). Then, water content of slab and bond strength of covering were measured.
Concrete was very generally used one on construction sites, 27 N/mm2 in compressive strength and 18 cm in slump value (reference to Table 1). Surface finishing work was typical condition of construction sites, once of wood trowel and twice of steel trowel. Special curing was not done, and specimens were dried in the air naturally (reference to Table 2).
Water content was measured using a high-frequency capacitance moisture meter (reference to Photo 2). Floor coverings were adhered according to timing that the moisture meter reading becomes 9.0, 7.0, 5.5, 4.5 or 3.5.
Two kinds of floor coverings were used, a vinyl chloride tile and a vinyl chloride sheet. Bond strength is grasped by ‘tensile strength’ (reference to Photo 3) and ‘90 degrees peel strength’ regulated JIS A 5536 (Adhesives for resilient, textile and laminate floor coverings). The original method of 90 degrees peel strength could not apply to an actual slab, therefore we made ourselves the device that was able to be measured equal bond strength at them (reference to Fig 2).
Finally, bond strength of coverings and water content of slabs were compared (reference to Fig 4 and 6). Bond strength has decreased by growing of water content. However, at a certain sort of adhesive, bond strength has rather decreased in the very dry specimen. This result suggests the possibility that each adhesive has an optimal value in water content of slab.
It is also turned out that, even though surface water contents were the same, there was a difference in bond strength by internal water contents. Also there was a difference between two kind of measurement method. They are very important suggestions.
Moisture meter reading measured immediately before construction of the floor covering is insufficient as the moisture management index. We will have to examine to combine the change speed of the moisture meter reading or some other measurement method of water content with it.
We also should do a deeper examination about the bond strength. To set the adaptable method of evaluating bond strength, several physical properties by different force application method should be selected and be combined appropriately. From Photo 1, force besides tension which can be measured by ‘tensile strength’ or ‘90 degrees peel strength’ are obviously applied to coverings in some situations. We will have to set measurement method of other physical properties, and examine the relation between their physical properties and actual force of detachment situations.
