What is used to allow differential movement of wall sections due to factors like shrinkage and temperature changes?

The appropriate choice for allowing differential movement of wall sections due to factors such as shrinkage and temperature changes is the use of expansion or control joints. These joints are specifically designed to accommodate the expansion and contraction that occurs in materials due to temperature fluctuations and other factors.

Expansion joints create a space in a structure to absorb movement, preventing the buildup of stresses that could lead to cracking or structural failure. They are crucial in ensuring that segments of walls can shift without compromising the integrity of the entire structure. Control joints, which are a type of expansion joint, are typically installed to regulate where cracking may occur and to provide relief from stresses.

Other options do not serve the same purpose as expansion or control joints. Mortar joints are primarily used to bond masonry units together and do not facilitate movement. Construction joints, while necessary for transitioning work phases, do not function to accommodate ongoing movement due to temperature changes or shrinkage. Piers are structural supports and do not play a role in movement accommodation. Thus, the use of expansion or control joints is essential for managing the dynamic behavior of wall sections in response to environmental factors.