Influence of pore structure on the moisture transport property of external thermal insulation composite system as studied by NMR

Abstract

In order to study the pore structure characteristics of the deteriorated structural layer of an external thermal insulation composite system (ETICS), the overall and stratified T2 spectrum signals of the system made of thin-layer inorganic insulation mortar are tested by nuclear magnetic resonance (NMR) technique under different moisture transport conditions. The variation in moisture transport with pore size in the structural layer of the ETICS is studied under three conditions, namely, vacuum-saturation, free water absorption and vapor adsorption process, and indices are proposed to evaluate the vapor adsorption and free water absorption capacity of ETICS. The results indicate that the total pore volume is predominated by the pores in the insulation layer as revealed by the peaks of T2 spectrum, which exhibit a bi-modal distribution with some larger pores. The pores in the finishing coat, protective layer and bonding layer have negligibly smaller size and smaller volume as revealed by a lower T2 peak and an indistinct second peak. The moisture transport patterns of pores with different sizes are quite different. Vapor adsorption mainly occurs in pores of size smaller than 0.1 μm and free water absorption mainly occurs in pores of size smaller than 10 μm.