A Comparison of Portland Cement Mortar and Portland Cement and Lime Mortar

Explaining the Differences:

Lime's Role in Mortar: When considering the water tightness of mortar, the presence of lime plays a significant role. While Portland cement is a key component in mortar mixtures, the addition of lime can enhance the overall properties of the mortar. Lime helps to improve the plasticity and workability of the mortar, which in turn can lead to better water tightness.

Self-Healing Properties: Lime mortar has the unique ability to self-heal microscopic cracks that may develop over time. This process, known as autogenous healing, can contribute to reducing water permeability and enhancing the water resistance of the mortar.

The Role of Additives:

Pozzolans in Roman Concrete: The use of additives such as pozzolans, like volcanic sand, has been shown to greatly improve the durability and water resistance of mortar. Roman concrete, known for its longevity and strength, incorporated pozzolana to enhance the properties of their mortar.