Heat transfer at void slab under fireproofing performance was unknown in detail. To clear the mechanism of that makes us evaluate the fire performance of void slab by calculating. At the existing fireproof test report about void slab, it indicates that void affect heat transfer for some reason. To reveal the heat transfer mechanism of void slab, authors conducted two experiments like fireproof test on pieces of void slab.
At the chapter 2, the authors confirm what happened in void during the fire by using the piece of void slab which has fireproof glass on a lateral side to observe void slab's inside as the first experiment. There are 4 specimens, which are void slab with EPS and fireproof glass, void slab with fireproof glass, void slab with EPS and slab without void. It revealed that EPS included in the void was not burning but gradually melting during the fireproof test and that EPS and water included in concrete has some relationship with heat transfer at void slab.
At the chapter 3, the authors check the impact of water included in concrete and EPS included in void slab on heat transfer at void slab by using pieces of void slab, included water and included EPS of which and water permeability in the void are controlled by drying concrete, taking EPS away from the void and coating epoxy resin on the surface of the void as the second experiment. It revealed that latent heat of water included in slab and thermoplastic and thermal insulation properties of EPS included in void were major impacts on heat transfer at void slab.
At the chapter 4, the authors make the heat transfer calculating model about void slab with consideration of latent heat of water and melting of EPS by using finite difference method. The model was mainly divided into two parts, one of which is consisted of concrete, void and EPS, and the other of which is consisted of only concrete. Basically, two parts are calculated individually, but heat transfer between the two parts gradually occurred with EPS melting. In this model, wet concrete has latent heat of water and heat absorption happens when temperature on concrete over 100°C and dried concrete has no latent heat of water. The authors set that EPS has melting point on 230°C and positons of EPS become position of void after EPS melt. The authors applied this model for the test specimens used in the chapter 3 and it revealed that calculating heat transfer at void slab by finite difference method matched results of the experiment to some extent.
As a result, the author revealed how to transfer heat on void slab by conducting the experiment imitating fireproof test and that the calculation method based on the experiments matched results of the experiment to some extent.
