What characteristic of concrete does the modulus of elasticity measure?

The modulus of elasticity is a critical property of concrete that quantifies its stiffness, which is the ability of a material to deform elastically when a force is applied. This characteristic is essential in structural design, as it helps engineers understand how much a concrete element will deflect under load. Essentially, the modulus of elasticity provides insight into how rigid or flexible the concrete will be, influencing how it reacts under various loading conditions.

In contrast, compressive strength is a measure of the maximum load-bearing capacity of concrete before failure, which does not directly indicate how it behaves under elastic deformation. Resistance to cracking pertains to the material's ability to resist stress-induced fractures, influenced by various factors including curing and mix design, rather than stiffness metrics. Lastly, bond strength with rebar refers to how well the reinforcing steel adheres to the concrete and transfers loads, which is also a different aspect of concrete properties than stiffness. Therefore, the modulus of elasticity distinctly measures the stiffness of the concrete material.