Concrete Shrinkage
Concrete Shrinkage - Related Videos
01:27
Shrinkage in Concrete
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2024
Shrinkage in concrete is primarily due to water loss from evaporation, hydration of cement, or carbonation, leading to a reduction in volume. The volumetric contraction results in volumetric strain in concrete. However, in practice, shrinkage is measured as linear strain, which is one-third of the volumetric strain. When concrete is still in its plastic state, it can undergo a decrease in volume by about 1% of its absolute volume. This decrease is known as plastic shrinkage. It arises either...
11:23
Tests on Fresh Concrete
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2017
Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA Concrete consists of two phases, a cement paste phase comprised of cement, water, and air, and an aggregate phase comprised of coarse and fine aggregates. There are two key considerations when designing a concrete mix. First, the concrete must be workable and easy to cast in the forms in its fresh condition, even when the forms are packed with steel reinforcement. In this condition, it is the...
01:21
Drying Shrinkage
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2024
When hardened concrete is exposed to air with a relative humidity of less than 100 percent, it begins to lose the free water within its capillaries. As this water evaporates, the water initially adsorbed onto the calcium silicate hydrates migrates towards these now empty spaces and eventually evaporates as well. Over time, as more water leaves, the volume of the concrete decreases, a phenomenon known as drying shrinkage. A portion of this drying shrinkage can be reversed; if the concrete is...
01:24
Carbonation Shrinkage
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2024
Atmospheric CO2 penetrates the concrete's pores and, in the presence of moisture, forms carbonic acid, which then reacts with calcium hydroxide in the hydrated cement, forming calcium carbonate. This process reduces the concrete's volume and is termed carbonation shrinkage. The concrete's permeability is slightly reduced as calcium carbonate produced during the reaction fills its pores. Furthermore, its strength is slightly enhanced as the water released during the reaction facilitates the...
10:09
Tests of Hardened Concrete in Tension
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2023
Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA In a previous laboratory focused on concrete in compression, we observed that concrete can withstand very large stresses under uniaxial compressive forces. However, the failures observed were not compressive failures but failures along shear planes where maximum tensile forces occur. Thus, it is important to understand the behavior of concrete in tension and particularly its maximum strength...
FAQs
Drying shrinkage is closely associated with moisture leaving capillary pores, so environmental humidity and curing conditions become important influences. Autogenous shrinkage can develop within a sealed mixture because cement hydration consumes internal water, even when external moisture loss is limited. Distinguishing these mechanisms helps engineers identify whether environmental exposure or internal hydration is the more significant deformation concern.
Mixture composition, the water-to-cement ratio, curing conditions, humidity, and member size all affect the magnitude and development of Concrete Shrinkage. These variables influence moisture availability, internal chemical changes, and the distance moisture must move through the concrete. Considering them together gives engineers a more reliable basis for predicting deformation and assessing potential durability risks.
When concrete cannot freely contract, restrained movement generates tensile stress within the material. If that stress becomes significant, cracking can occur even though the underlying volume change is relatively small. Reinforcement and member configuration therefore matter during structural evaluation because they influence how shrinkage-related deformation is accommodated and where durability risks may develop.
Engineers assess shrinkage alongside mixture composition, curing conditions, humidity, member size, and reinforcement rather than treating it as an isolated material property. This evaluation supports prediction of deformation and helps identify locations where restraint may create tensile stress or cracking. The resulting assessment informs decisions intended to protect structural performance and long-term durability.
Proper curing helps control moisture-related development, while an optimized water-to-cement ratio can reduce conditions associated with excessive deformation. Shrinkage-reducing admixtures provide another mixture-level option, and joint design allows planned movement within a structure. Engineers select and combine these measures according to the expected shrinkage mechanisms, environmental conditions, and structural configuration.
Concrete Shrinkage deserves particular attention when a structure must maintain dimensional stability and resist cracking over time. Shrinkage evaluation connects early material behavior with durability risk because restrained tensile stress can damage the concrete. By incorporating curing, humidity, member size, reinforcement, mixture design, and joints into planning, engineers can improve the likelihood of a longer service life.