The correct answer is: B. Lower initial setting time but higher final setting time.
High alumina cement is a type of cement that is made from bauxite, which is an ore of aluminum. It is a fast-setting cement, which means that it sets and hardens quickly. This makes it ideal for use in applications where early strength is required, such as in precast concrete.
High alumina cement has a lower initial setting time than ordinary Portland cement. This means that it starts to set and harden more quickly. However, it has a higher final setting time than ordinary Portland cement. This means that it takes longer to reach its final strength.
The lower initial setting time of high alumina cement can be an advantage in some applications. For example, it can be used to create concrete that can be poured and finished quickly. However, the higher final setting time of high alumina cement can be a disadvantage in some applications. For example, it can make it difficult to cast concrete into complex shapes.
Overall, high alumina cement is a versatile type of cement that has both advantages and disadvantages. It is important to choose the right type of cement for the specific application.
Here is a brief explanation of each option:
- Option A: Higher initial setting time but lower final setting time. This is not the correct answer because high alumina cement has a lower initial setting time than ordinary Portland cement.
- Option B: Lower initial setting time but higher final setting time. This is the correct answer because high alumina cement has a lower initial setting time than ordinary Portland cement and a higher final setting time than ordinary Portland cement.
- Option C: Higher initial and final setting times. This is not the correct answer because high alumina cement has a lower initial setting time than ordinary Portland cement.
- Option D: Lower initial and final setting times. This is not the correct answer because high alumina cement has a higher final setting time than ordinary Portland cement.