This study aimed to assess the impact of ambient conditions on the internal microstructure of high-strength concrete (HSC) samples. A scanning electron microscope (SEM) was used with X-ray microanalysis to study the relationship between ambient conditions and the durability of concrete. The concrete specimens were cast at a temperature of 25 ±1 °C and cured under three different conditions: standard curing, steam curing, and dry curing at 50 °C. Conventional Portland cement, crushed aggregate, and natural sand were used in the production of all specimens. Three water binder ratios were typically used: 0.3, 0.35, and 0.4. Three different mixes were also used, containing different binders: 450, 520, and 480 kg/m³. In this study, 30 % fly ash was used in all mixes, while silica fume partly replaced this in a ratio of 0 %, 5 %, and 10 % by weight of cement in the concrete mixes, respectively. Additionally, the effect of ambient conditions was estimated by computing the compressive strength, flexural strength, microhardness, permeability, and the microstructure of concrete. The relationship between these concrete properties was obtained. SEM and energy-dispersive X-ray spectroscopy (EDX) were used to confirm the results for samples cured under all conditions. HSC was obtained that exhibited desirable properties when additional cement materials such as silica and fly ash were used to form homogeneous concrete with a smooth surface; the concrete had low permeability and high durability. It was concluded that it was possible to produce concrete with low permeability and durability within a harsh environment.