Finishing material that is bonded to the wet slab peels off at high probability. We are researching to propose the moisture management index of slab surface. In our previous thesis, targeting at resilient floor coverings, the relation among bond strength and water content of slab surface was quantitatively examined. At that time, it was proved that both of two methods to grasp physical properties of bond strength regulated JIS A 5536 (Adhesives for resilient, textile and laminate floor coverings) are insufficient to use them alone, due to the fact that force application modes are too simplified and unrealistic.
Actual fails were investigated in hearing for engineers of covering maker. As a result, it was found that poor adhesion part became to be "Bulding", "Peeling", "Joint tenting" or "Shrinkage". Then, we observed those fails in an actual building, and grasped the outline of force application modes of them.
When the fail which require the development of a device to simulate the actual force application mode was chosen, it takes a lot of labor and time to prepare the experiment. It was seen that joint tenting (reference to Photo 2) is suitable for our research object, because it might be reproduce immediately in our experimental environment. It can be realized just by adjusting the temperature.
By a preliminary experiment, joint tenting was able to be generated intentionally by adhering cooled coverings on specimen slabs (reference to Fig. 1) at the middle of the night in winter which was 5 °C outdoors and moving specimens to a warm laboratory. Size of specimen slab and specifications of testing covering were regulated appropriately (reference to Photo 4), joint tenting test method was fixed.
At last, while drying specimens, joint tenting tests were carried out. The target which we chose was compressive strength of concrete which is 27 N/mm2 and slump of concrete which is 18 cm (reference to Table 2). We used the working technique for 2 concrete surface finishing that is set according to the typical condition of actual construction sites (reference to Table 3). The typical tile covering was chosen for test, because hard tile covering was thought to be tented easily than soft seat covering (reference to Table 4). Two kinds of adhesives were chosen (reference to Table 5). One is an acrylic adhesive, representative of the water soluble. Another is an epoxy adhesive, representative of the one which is not soluble in water but is unexpectedly influenced by water in the chemical reaction. Water content was grasped by reading of moisture meter (reference to Photo 3). Then, the probability of occurrence of joint tenting at interval of 1 moisture meter reading was calculated. Due to the result, relationship between probability and moisture meter reading was considered (reference to Fig. 4). Then, the probability changed drastically at 5 of the moisture meter reading. This result proved covering engineers' rule of thumb to be correct, and the possibility that the moisture meter reading was able to be applied to the moisture management index.
