Final answer:
Concrete blocks are the suitable load-bearing structural material for masonry walls exposed to weathering or frost action.
Step-by-step explanation:
The type of load-bearing structural material suitable for masonry walls exposed to weathering or frost action is concrete blocks. Concrete is a reliable and durable material that can withstand the effects of weathering and frost. It is made of a mixture of lightweight coarse aggregate and fine aggregates like shale, clay, or slate. Concrete blocks are commonly used in masonry construction due to their strength, resistance to weathering, and thermal properties.