Based on the winter conditions in your state, it is not a matter of what material will not freeze, but what material is best suited to minimize ice-covered surfaces.
For the walkway
Look for materials that will allow drainage, such as pavers or pervious pavement. Both of these systems allow water to drain through and be absorbed into the soils below.However, buildup of snow and ice over the course of the winter will hinder the drainage and will require shoveling or even the addition of salt to aid in the melting of the snow and ice.
Another system that works better but is more costly is creating a heated walkway using a hydronic heating system integrated into a concrete slab. This system will circulate hot water through pipes located in the concrete slab of the walk and will melt all snow and ice, leaving a dry, safe surface.
For the porch
If your porch is constructed of wood or a synthetic deck board material, there is little that can be done other than shoveling and salting. However, if it is concrete, you can utilize the same hydronic heating system within the concrete slab of the porch as I had mentioned for the walkway.
However, you must weigh the pros and cons for this type of system. Ask yourself this question: is the additional cost for the installation and operation more important or less important than the safety of you, your family and guests during the winter months?
FYI, this hydronic heating system can be supplemented by the installation of a solar hot water heater, which may eliminate the cost of electricity or gas to create the hot water.