Improving the durability of concrete structures in harsh environments remains a significant engineering challenge. This research investigates the influence of latex polymer modification on the mechanical and durability properties of concrete. Three distinct application methods were evaluated: internal mixing, surface coating, and a hybrid approach (combining both methods). Tests were conducted on concrete mixes with cement contents of 300 and 450 kg/m³. The experimental program included compressive and tensile strength tests, water penetration depth analysis, and resistance to 300 rapid freeze–thaw cycles in accordance with ASTM C666. The results demonstrate that polymer modification significantly improves concrete performance. Notably, the hybrid C450 specimens exhibited the highest efficiency, with a 51.2% increase in tensile strength and a 55.8% reduction in water penetration compared to the control group. Furthermore, while control specimens suffered up to 22% strength loss after 300 freeze–thaw cycles, the polymer-modified specimens remained highly stable, limiting strength degradation to only 8%. This confirms the superior protective role of latex polymers against frost damage. The findings suggest that surface modification is a cost-effective solution for budget-limited projects, whereas internal and hybrid methods are ideal for strategic infrastructure requiring high mechanical resilience. This study provides an optimized framework for designing high-performance concrete suitable for aggressive and cold climates.