So, as time passes, the strength of concrete will increase. From table 2. 1, the compressive strength of air cured concrete (cube) in this experiment gave higher results than water cured concrete (cube). Theoretically, water cured concrete should provide better results cause water ensures constant temperature for the concrete to harden and avoids moisture loss during hydration. This may be due to the mixture being not homogeneous or the air cured concrete cube being the best mixed cube with least air bubbles.
The hand tempered concrete cube shows slightly less compressive strength than the cube vibrated by the vibrating table. This is mostly likely due to more air voids present in the hand tempered concrete cube. Air voids reduces interlocking between the concrete components. None of the concrete cubes and prisms reaches the target strength of NON/mm. This may be due to several reasons such as additional water added to the concrete mixture. The assumption used in the concrete design was that the aggregates is oven dried but the aggregated used in the experiment is moist.
This can be seen in the slump test as the target slump test was only mm but the conducted slump test in this experiment was mm. It may also be due to poor mixture of concrete components and air bubbles present in the mixture. Another significant cause may be due to segregation of the concrete mixture as the components in the concrete mixture have different densities. Average experimental values of static modulus ECMA is 32% less than theoretical values.
The inconsistencies between experimental and theoretical values may be caused by some experimental results which is not realistic such as the static modulus of air cured prism from the erudite test. The concrete prisms showed very low flexural tensile strength compared to compressive strength. This is because the prisms are made of plain concrete and not reinforced with steel. It is predicted that the air cured prism would give better results from the concrete cube compressive tests but it is shown otherwise. This proves that water cure is better for producing higher quality concrete.
Recommendations to improve future experiments: * Continuously mix the concrete mixture to avoid segregation. * Slowly increase the water content in the concrete mixture to achieve targeted slump test. Conclusion: In conclusion, even though the target concrete strength of NON/mm was not met, the experiment showed satisfactory values which did not deviate largely from theoretical values except for the air cured erudite test result and the difference in compressive strength of air and water cured concrete cube.