Unrestrained Concrete
Unrestrained Concrete - Related Videos
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...
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...
08:08
Compression Tests on Hardened Concrete
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2023
Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA There are two distinct stages in a construction project involving concrete. The first stage involves batching, transporting, and casting fresh concrete. At this stage, the material is viscous, and the workability and finishability are the key performance criteria. The second stage occurs when the hydration process begins shortly after the concrete is placed in the form, and the concrete will...
08:51
Measuring Respiratory Function in Mice Using Unrestrained Whole-body Plethysmography
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Cited by 70 •
2014
The assessment of respiratory physiology has traditionally relied upon techniques, which require restraint or sedation of the animal. Unrestrained whole-body plethysmography, however, provides precise, non-invasive, quantitative analysis of respiratory physiology in animal models. In addition, the technique allows repeated respiratory assessment of mice allowing for longitudinal studies.
10:10
Aggregates for Concrete and Asphaltic Mixes
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2023
Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA Concrete and asphalt are by far the most common construction materials used today. Concrete is a composite material consisting of cement, water, air, coarse aggregate, and fine aggregates. Fine aggregates are typically sands and coarse aggregates are natural or crushed rocks. Chemical admixtures to modify certain specific properties are also commonly used (i.e., superplasticizers to make the...
FAQs
Its response is expressed mainly as free strain, meaning measurable deformation rather than restraint-induced stress. Autogenous and drying shrinkage reduce dimensions, while thermal changes produce expansion or contraction. Creep contributes additional long-term deformation. Observing these movements separately helps engineers understand the material response before adjoining members, reinforcement, or supports limit that movement.
Free strain provides a reference for estimating how much movement the concrete would undergo if external resistance were insignificant. Cracking potential becomes more understandable when this reference is compared with a real structural condition in which walls, slabs, reinforcement, or supports oppose movement. The comparison helps distinguish material deformation from effects caused by structural restraint.
In the unrestrained condition, shrinkage, thermal movement, and creep can develop primarily as deformation. In a restrained system, adjoining structural elements, reinforcement, or supports limit that deformation, so restraint-induced stress becomes important. This contrast makes the unrestrained condition a baseline rather than a complete prediction of behavior in an actual wall, slab, pavement, or other member.
Engineering studies use the unrestrained condition as a baseline for laboratory characterization and mix-design evaluation. Researchers examine the concrete's deformation associated with autogenous and drying shrinkage, temperature variation, and creep, then use those observations to assess cracking potential and long-term behavior. The resulting baseline supports comparison with structural systems where movement is limited.
Measurements can indicate how a mix responds to cement hydration, moisture change, temperature change, and sustained deformation over time. Those observations help characterize shrinkage and creep behavior and identify the material movements that may matter when restraint is introduced. The information supports mix design decisions, durability assessment, and prediction of longer-term structural performance.
It is useful when assessing walls, slabs, pavements, and other concrete members whose real supports or connections may restrict movement. Engineers can first consider the baseline deformation, then evaluate how actual restraint changes cracking potential and stress development. This approach connects laboratory characterization with structural performance predictions and durability assessments in concrete engineering.