COMPRESSIVE STRENGTH

Fire exposure destroys concrete structures, and the cooling methods significantly impacts residual strength Rapid cooling, especially with water, may cause additional damage due to thermal shock, yet limited studies compare air- and water- cooling effects. In order to determine which cooling technique best maintains structural integrity, this study will examine how various techniques affect the breaking strength of Grade 30 concrete exposed to temperatures of 200°C, 400°C, and 600°C. This study involves the preparation of Grade 10 concrete specimens, which were cured for 28 days before being subjected to elevated temperatures of 2000C 400C and 600°C in a controlled furnace. After exposure, the specimens were cooled using air and water to compare the effects of each method on compressive strength. The compressive strength of all samples was tested using a compression testing machine, and the results were analyzed through tabular and graphical comparisons to evaluate strength reduction trends. The study revealed that compressive strength decreased with increasing temperature, with watercooled samples experiencing greater strength loss than air-cooled due to rapid thermal shock. At 600°C, Average water-cooled samples record 26.561 N/mm², while air-cooled samples record 28.014 N/mm², confirming that gradual cooling helps to retain more structural integrity. Based on these findings, air cooling is recommended as a safer and more effective method for post- fire concrete recovery. Further research should explore advanced cooling techniques to enhance fire resistance and durability.

All over Nigeria as well as to the overseas the fuel oils as well as crude oils are transported through distribution pipes, tankers cargo ships. Although the processes are well laid out to avoid leakages of pipes, accidents of service tankers these events still happens on a regular bases especially in the niger delta region of the country where pipe vandalism due to oil bunkery is on the rise. All these processes leads to the leakages of fuel oils e.g kerosene which eventually settles on coastal waters. The leaked oil products would result in contaminating the water which are used in the concrete mortar and the sandcrete industry which are the cement dependent industry. In this study, the effect of water contaminated with kerosene on the compressive strength of conventional normal ordinary Portland cement has been evaluated in various exposure conditions. Kerosene (0, 2, 4 and 6%) by weight of water) was used to contaminate water to prepare cement mortar cubes specimens. A number of nine uncontaminated samples were prepared with fresh water. A number of nine samples each were prepared with contaminated water at 2%, 4%, 6% Kerosene replacement. Three samples each of percentage replacement and three uncontaminated samples were crushed at the age of three days, seven days and 28 days of curing. From the results gotten the maximum reduction in the compressive strength of 9.21% occurred at the six percentage contamination at the age of seven days. From results obtained it was seen that as the percentage of contamination increase the compressive strength decreased.