True/False: A wall made of portland cement mortar (without lime) is more watertight than a wall made of portland cement and lime mortar.

A wall made of Portland cement mortar without lime is not necessarily more watertight than one made with lime. Lime improves the mortar's plasticity and can lead to better water tightness, in addition to enabling the mortar to self-heal cracks. The durability and resistance to water are greatly enhanced by additives such as pozzolana, as was done in Roman concrete.

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

18 Dec 2021

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.

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Explaining the Differences:

The Role of Additives:

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