Final answer:
Concrete durability in freeze/thaw conditions can be addressed by designing structures to accommodate thermal expansion, using materials with harmonious coefficients of linear expansion, and leveraging historical techniques such as those used by the Romans to create versatile and robust concrete mixtures.
Step-by-step explanation:
When considering how to make concrete more durable in freeze/thaw conditions, several factors must be taken into account. The concrete mixture typically includes lightweight coarse aggregate combined with fine aggregates like shale, clay, or slate. This concoction has proven reliable over the last century, perfecting concrete's utility in construction.
One of the crucial techniques used in engineering to mitigate the effects of thermal stress is to allow for expansion and contraction of the concrete material. For example, in highway construction, gaps (often filled with a flexible material) are deliberately left between concrete slabs to accommodate thermal expansion. Additionally, reinforcing rods made of steel are used within the concrete because steel's coefficient of linear expansion is very similar to that of concrete, hence providing an even response to temperature changes.
The Roman use of concrete, mixing lime mortar with aggregates such as pebbles and sand, showed the material's versatility, as it was able to be poured into molds and harden, functioning like stone. This historical understanding of concrete's properties is still applicable today when engineering solutions for freeze/thaw durability. Using proper materials and design strategies can ensure longevity and resilience of concrete structures under varying temperature conditions.