Also known as open porosity. The percentage of the volume of open pores in a refractory product to the total volume of the product. Unless otherwise specified, the porosity referred to in the Chinese refractory industry usually refers to the apparent porosity. Apparent porosity is an important indicator for evaluating the quality of refractory raw materials or products. It not only reflects the density of refractory materials, but also characterizes whether its manufacturing process is reasonable. In addition to lightweight refractory products, low-porosity raw materials or products are beneficial to improving product quality, improving the mechanical strength of products, reducing the surface area in contact with slag, and extending service life.

Apparent porosity formula:

Apparent porosity = (s-w/s-i)*100

s - weight of piece soaked

w - weight of dry piece

i - weight of the piece soaked and immersed.