Q1. (a) (b) As a site engineer, you need to cast a concrete structure in a tropical weather country. Identify a chemical admixture and its dosage to be used in the casting in order to delay the concrete setting time around 4 hours. Explain the effect on the strength and shrinkage of concrete. State the limited percentage of the chemical admixture and explain why the dosage should be limited. (12 marks) As a concrete plant design engineer, you have found a concrete mix design which cannot achieve the high strength category. Identify the admixtures and dosage to be added in order to achieve the high strength concrete without affecting the workability of concrete. Interpret the mechanism of the admixtures. (13 marks) [Total: 25 marks]