O. Osasu

This study examines how curing reinforced concrete in a urea-salt solution, which simulates urine, affects its compressive strength and durability. This is compared to concrete cured in fresh water. The research addresses concerns about the decline of concrete structures in environments that are biologically or chemically harsh, such as areas often contaminated by urine. Understanding the impact of such exposure on concrete performance is important for improving the design and maintenance of durable structures under these conditions. The experimental work involved casting twenty concrete cubes, each measuring 100 × 100 × 100 mm, using a mix ratio of 1:2:4 and a water-cement ratio of 0.5. Ten cubes were cured in fresh water, while the other ten were cured in a urea-salt solution made with 10 g of urea and 2 g of sodium chloride (NaCl) per liter of water. The cubes were tested for compressive strength after 14 and 28 days of curing using a compression testing machine. The data gathered were analyzed and compared to evaluate the impact of the urea-salt solution on concrete performance. The average compressive strengths were 18.81 N/mm² and 23.17 N/mm² for the 14- and 28- day fresh-water samples, and 18.15 N/mm² and 17.81 N/mm² for the urea-salt-cured samples which indicates that concrete cured in fresh water showed normal strength growth with age. In contrast, the concrete cured in the urea-salt solution had a slight decrease in compressive strength over time. It was concluded that exposure to the urea-salt solution restricts full hydration and weakens concrete durability with extended contact. It is advised that structures in areas prone to urine contamination be shielded from direct exposure.

This experiment studies the effect of waste ceramic tile aggregate as partial replacement of conventional coarse aggregate on the compressive strength and durability of concrete, in an attempt to determine the possibility of utilizing waste ceramic tile aggregate (WCTA) as partial replacement for conventional granite in concrete production. For the experiment, a M25 grade concrete with a water/cement ratio of 0.5 was prepared using granite substituted with WCTA at a replacement percentage of 0%, 10%, 20%, 30%, 40% and 50%. Tests such as sieve analysis and aggregate impact value was performed on the various aggregates used in the study to determine their suitability. Concrete cubes of size 100mm×100mm×100mm were casted and tested for compressive strength after a curing period of 7 and 28 days. Water absorption test was also performed on the hardened concrete mixes to determine their durability. From the experimental results, it is found that the 7th day compressive strength of the concrete mixes are 21.32N/mm², 25.37N/mm², 23.54N/mm², 24.20N/mm², 22.21N/mm² and 20.47N/mm², while 28th day compressive strength is found to be 29.66N/mm², 29.80N/mm², 31.94N/mm², 33.59N/mm², 29.65N/mm² and 27.80N/mm², for 0%, 10%, 20%, 30%, 40% and 50% substitution respectively. Also the water absorption of the concrete samples is observed to be 2.36%, 2.47%, 2.21%, 1.64%, 1.98% and 2.14% for 0%, 10% ,20% ,30%, 40% and 50% respectively. The result reveals that the use of WCTA as partial replacement of coarse aggregate in concrete leads to the enhancement of the compressive strength of concrete, as long it doesn't exceed 30% replacement. Also the addition of WCTA leads to an increase in the water absorption of the concrete for 10% substitution with WCTA, while it leads to a decrease in water absorption for 20- 50% substitution with WCTA, with 30% having the least water absorption. Therefore it is recommended to limit the replacement of granite with WCTA to a maximum of 40%, while for optimal strength and durability of structural concrete, replacement of granite with WCTA should be kept at 30%.