One of the most important concrete properties for structural concrete design or redesign is the compressive strength, it gives information on the characteristics of concrete. This strength measure is obtained through standardized crushing tests on cast cubes, the cubes are produced alongside the construction of concrete elements on site however they are not available for strength testing of existing buildings henc3e the need for non-destructive test methods. Schmidt’s Rebound Hammer is a nondestructive test which is used to assess the compressive strength of concrete using rebound index. Surface hardness test was done on different concrete mix and compared with cube compressive strength tests. The changes in one variable explained by the change in a related variable as given by the R-squared are 93.79%, 99.42%, 86.8%, 1% and 98.5% for Mix 1, 2, 3, 4 and 5 respectively. It is noted that for proper result from non-destructive tests, more than one should be implored and the model calibration should be based on actual compressive strength.
This study carried out an experimental design investigating the reaction of mineral admixtures on fresh and hardened properties of sustainable self compacting concrete (SCC). Silica fume (SF) and metakaolin (MK) were partially replaced by Portland cement at 5, 10, 15, 20 and 25% in varying proportions. The workability on the fresh concrete was examined and the strength performance. The water cement ratio of 0.38 was kept constant for all the samples tested. The compressive strength was measured at 7, 14, 21 and 28 curing days. The test results indicated that with the influence of 2% superplasticizer, the fresh concrete showed a satisfactory workability, decreased the segregation to resistance, ease of flowing ability with the addition of silica fume and metakaolin. It was concluded in this study that, the replacement with silica fume was found to have an early strength gain in the compressive strength of SCC samples and a decrease at varying dosages. However, 15% metakaolin was considered to be a suitable replacement with 49.08 MPa at 28days compared with the control mix..
The economic costs of construction have become largely unbearable today. In a bid to mitigate these costs, civil engineering faculties and stakeholders across the world have endeavoured to produce recyclable and resource saving concrete for construction purposes. Most of the environmental problems are caused by the deposit of waste to the environments in which marble shaping is part. Both stone slurry and solid wastes are generated from the marble stone slurry and with the huge discharge of marble waste locally, emphasizes has been placed on the reuse of the waste material. This research investigates the utilization of marble dust powder in concrete, where marble dust at varying percentage (0%, 15%, 25% & 35%) with replacement by sharp sand was added in M15 grade and water cement ratio 0.50 was kept constant in the concrete mixes. The quality, performance and reliability of the concrete where tested by the compressive and split tensile strength of 7, 21, 28 and 56 curing days. The results of the laboratory work showed that marble dust powder replacement with cement increased in strength up to 25% for both resistance to compressive load and tensile strength of concrete.
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