In modern, waste-fired cement kilns, harmful atmospheric particles in the kiln gases are primarily responsible for the degradation of the refractory lining. The new formation of mineral phases is based on infiltration and chemical interaction with the primary mineral phases. This leads to a differentiation of the physical properties towards temperature gradients in the direction of the kiln shell. Suitable new product developments need to be chemically inert to alkali and sulphur and demonstrate a maximized infiltration resistance. It is self evident that adequate thermochemical resistance to the cement clinker must be present in each zone of use. Some modified and new products are described in brief form.