Cement is an important building material in the construction industry because it has a high overall strength and binds concrete mixtures together. However, if a fire occurrence or accident exposes already-produced cement to heat at temperatures of 100 °C and above, what would be the stability of those exposed cements and the possibility of their being usable for construction work? Should cement exposed to open flames be condemned and disposed of, or is it still usable? This study investigates the effect of cement exposed to open fire on the overall strength of concrete, the potential strength reduction, and whether it can still be used for construction work. A grade of 42.5 N cement was subjected to an open fire flame between 100 and 300 0C. Three different temperature levels of 100, 200, and 300 °C were chosen for this investigation. The burnt cement in its cold and hot forms was used as a binder in producing concrete cubes (CC). Seventy-two (72) CC samples of 150 x 150 x 150 mm were produced from the burnt cement, both in cold and hot form, as specified by BS EN 12390-3. Twelve (12) CC were also produced with unburned cement and served as a standard for burnt cement samples. All of the compressive strengths (CS) were examines at 7, 14, 21, and 28-day. Results show that Cement exposed to open fire had a negative effect on the stability of the concrete. The burnt cement at temperatures of 100, 200, and 300 0C in cold form reduces the CS of concrete by 34, 50, and 48%, respectively. In hot form, it reduces the CS of concrete by 35, 46, and 40%, respectively. The reduction in CS is attributed to heating calcium, silica, aluminum, and iron. Lightweight concrete can be made with burnt cement at temperatures of 100, 200, and 300 0C. It can also be used in the production of concrete blocks. The variation amongst the predicted coefficient of regression (R2) of 0.9997 and the adjusted coefficient of regression (R2) of 0.9998 is less than 0.2, which is considered to be a fair agreement.