Penetration of fine particles through rough cracks

Many building materials have random roughness protrusion scales of up to hundreds of micrometers. A scaled down experimental facility was designed to investigate fine particlesʹ penetration through a straight, smooth and rough crack under four different pressures ranging from 2 to 8 Pa. Sandpapers with three different roughness scales were used to create 10 to 100 micron rough surfaces. Particle concentration for sizes ranging from 20 to 500 nm was measured to determine the penetration. Contrary to expectations, the results are not sensitive to roughness scales. Besides, it is also noticed that under low differential pressure scenario, deposition for rough cracks for small particles is higher than that of smooth crack which will offer better protection for indoor exposure. A simple mathematical model was also developed to predict particle deposition on rough surfaces by diffusion mechanism on extended surfaces. The experimental results match well with the model prediction.