No, after the mortar is initially mixed no water or powder should be added.
Why Adding Water to Drying Mortar is Not Recommended
According to best practices in construction and masonry, attempting to reactivate drying or hardening mortar by adding more water is strongly advised against. The reference clearly states, "No, after the mortar is initially mixed no water or powder should be added." This fundamental rule is crucial for ensuring the strength, durability, and performance of the finished mortar joint or application.
Adding water after the initial mixing phase and as the mortar begins to dry or set disrupts the chemical process that gives mortar its strength. Mortar hardens through a process called hydration, where a chemical reaction occurs between the cement, water, and other ingredients. This reaction starts upon initial mixing and continues as the mortar cures.
What Happens When You Add Water Later?
Re-tempering, or adding water to drying mortar, has several negative consequences:
- Weakened Bond: The primary issue is a significant reduction in the mortar's compressive strength and adhesive properties. The water-cement ratio, which is carefully calculated during initial mixing, is altered, leading to a weaker matrix.
- Inconsistent Mix: The mortar will not have a uniform consistency throughout. Some parts may become soupy, while others remain lumpy or partially set, making it difficult to work with and ensuring a non-uniform cure.
- Increased Shrinkage and Cracking: Adding extra water can increase the potential for shrinkage as the water evaporates, leading to hairline cracks or larger fissures in the hardened mortar.
- Reduced Durability: The finished product will be less resistant to weathering, moisture penetration, and overall wear and tear, compromising the longevity of the structure.
Instead of adding water to drying mortar, the correct procedure is to discard the old material and mix a fresh batch. This ensures that the mortar has the proper consistency, strength, and curing properties necessary for a durable and reliable bond.
