(ii) Differentiate between hydraulic and non-hydraulic limes. (b) Explain the following terms used in concrete: (i) setting of concrete; (ii) hardening of concrete.

(ii) Differentiate between hydraulic and non-hydraulic limes:Hydraulic lime, also known as slaked lime, is a type of lime that hard it comes into contact with water. It is composed primarily of calcium hydroxide (Ca(OH)2) and is obtained by the hydration of quicklime (CaO). Hydraulic lime is characterized by its ability to set and harden under water, making it suitable for use in water-based construction applications such as plastering, rendering, and the production of lime mortar.Non-hydraulic lime, on the other hand, does not harden when it comes into contact with water. It is composed primarily of calcium carbonate (CaCO3) and is obtained from the decomposition of limestone or chalk. Non-hydraulic lime is commonly used in dry applications such as the production of lime putty, which is used in traditional lime plaster and mortar.(b) Explain the following terms used in concrete:(i) Setting of concrete:The setting of concrete refers to the process by which the liquid cement paste begins to solidify and form a hard, solid mass. This process is initiated by the hydration of the cement, which causes the cement particles to react with water and form a gel-like substance. As the gel hardens, it forms a rigid structure that binds the aggregates (such as sand and gravel) together. The setting time of concrete is influenced by factors such as the type of cement used, the amount of water added, the temperature, and the presence of any accelerators or retarders.(ii) Hardening of concrete:The hardening of concrete, also known as curing, is the process by which the concrete gains strength and durability over time. This process is essential for ensuring the long-term performance and longevity of concrete structures. During the hardening process, the cement particles continue to react with water, forming additional cementitious bonds that strengthen the concrete. The rate of hardening is influenced by factors such as the type of cement used, the amount of water added, the temperature, and the presence of any accelerators or retarders. Proper curing is crucial for achieving the desired strength and durability of concrete structures.