Explain the various causes for dimensional changes in the hardened concrete.

Step 1: Understand the concept of dimensional changes in hardened concrete. Dimensional changes

Explain the various causes for dimensional changes in the...

Key Concepts

Chemical Reactions

Certain chemical reactions, such as delayed ettringite formation or alkali-aggregate reactions, can lead to expansion in concrete. These reactions may occur over extended periods, causing internal stress changes and eventual dimensional variations that can manifest as cracking or structural deformations.

Creep

Creep is the time-dependent deformation under a sustained load. In hardened concrete, even at constant moisture and temperature conditions, long-term stress can lead to additional compressive strains, resulting in gradual changes in dimensions over its service life.

Drying Shrinkage

Drying shrinkage is the reduction in volume that occurs when hardened concrete loses moisture to the environment. This process is largely influenced by the rate of water evaporation, environmental humidity, and the porous structure of the concrete, and it plays a significant role in the dimensional stability of the material over time.

Autogenous Shrinkage

Autogenous shrinkage happens as a result of the chemical reactions during cement hydration, where water is consumed internally. Even in sealed conditions, the concrete experiences internal self-desiccation as the products of hydration occupy less space, leading to a reduction in volume without any external drying.

Thermal Effects

Thermal effects in hardened concrete include both expansion and contraction due to changes in temperature. During the hydration process, heat is generated (the heat of hydration) causing temporary expansion, and subsequent cooling leads to contraction. External temperature variations further contribute to cyclic thermal strains that affect the overall dimensions of concrete.

Please give Ace some feedback