What is the reason for the hardening of the mortar and how can you write the equation of the reaction that occurs?

The hardening of mortar is primarily due to the hydration of cement, which involves a chemical reaction between water and the compounds in cement, primarily tricalcium silicate (C3S) and dicalcium silicate (C2S). When water is added, these compounds react to form calcium silicate hydrate (C-S-H) and calcium hydroxide (Ca(OH)2), which contribute to the strength and stability of the mortar. The simplified reaction for the hydration of tricalcium silicate can be represented as:

[ 2 \text{C}_3\text{S} + 6 \text{H} \rightarrow 3 \text{C-S-H} + 3 \text{Ca(OH)}_2 ]

This process continues over time, leading to the hardening of the mortar.